Software ID ........................................................................................................................................... 7
This manual provides information about the MicroTech Chiller System Controller (CSC) for
McQuay centrifugal [PEH and PFH ( both available in series 100 and 200 controllers)],
reciprocating (ALR and WHR), screw (PFS and ALS), Global (AGZ, AGR, and AGS), and J&E Hall
Chillers. It specifically describes the CSC’s features, sequences of operation, and programmable
options. It also includes information on how to use the keypad/display to enter and display data.
For information on MicroTech components, field wiring options and requirements, network
commissioning procedures, and service procedures, refer to Bulletin No. IM 618, MicroTech ChillerSystem Controller. For specific information about the MicroTech chiller controllers, refer to the
appropriate MicroTech unit controller installation or operation manual (see Table 1 and Table 2).
Table 1 MicroTech Unit Controller Installation Literature
Chiller TypeBulletin Number
Series-100 CentrifugalIM 403
Series-200 CentrifugalIM 616
ReciprocatingIM 493
ScrewIM 549
Global (AGZ)IM 686
Global (AGR)IOM 690
Table 2. MicroTech Unit Controller Operation Literature
Chiller TypeBulletin Number
Series-100 CentrifugalOM 119
Series-200 CentrifugalOM 125
ReciprocatingIM 493
ScrewIM 549
B Vintage Flooded ScrewOM 129
C Vintage Flooded ScrewOM 135
Global (AGU)IOM 690
WARNING
!
Electric shock hazard.
Can cause personal injury or equipment damage.
This equipment must be properly grounded. Connections and service to the MicroTech control
panel must be performed only by personnel that are knowledgeable in the operation of the
equipment being controlled.
NOTICE
This equipment generates, uses and can radiate radio frequency energy and, if not installed
and used in accordance with this instruction manual, may cause interference to radio
communications. It has been tested and found to comply with the limits for a Class A digital
device, pursuant to part 15 of the FCC rules. These limits are designed to provide reasonable
protection against harmful interference when the equipment is operated in a commercial
environment. Operation of this equipment in a residential area is likely to cause harmful
interference in which case the user will be required to correct the interference at his or her
own expense.
interference or for the correction thereof.
McQuay International disclaims any liability resulting from any
6OM127-1
Software ID
MicroTech CSC software is factory installed and tested in each panel prior to shipment. The software
is identified by a program code (also referred to as the “Ident”), which is printed on a small label
affixed to the MCB. The program code is also encoded in the controller’s memory and is available for
display on menu 28 of the keypad/display or a PC equipped with MicroTech Monitor™ software.
Using menu 28 or the Monitor program is the most reliable way of determining the controller’s
program code.
Figure 1. CSC Program Codification
CSC 1 E 01 F
Chiller System Controller
Program number
1 = Standard software
Units
E =English
S = SI
Version (nummeric)
Version revision (alphabetic)
a0239
If the CSC’s program code does not match the format shown above, it is likely that a special program
has been loaded into the controller and some of the information in this manual may not apply.
This edition documents revision F of the standard CSC software and all subsequent revisions of
version 01 until otherwise indicated. If your CSC software has a later revision code (for example,
CSC1E01H), some of the information in this manual may not apply to your software. However, since
revisions are usually very minor software changes, the discrepancies should be insignificant.
Software Compatibility
The current version is not compatible with some earlier versions of MicroTech centrifugal,
reciprocating, and screw chiller controller standard software. The current software compatibility is
>
summarized in Table 3. The wildcard character (
If you want to use a CSC with older chillers that have incompatible standard software, the chiller
software must be upgraded. (This applies to all Centrif-100 chillers.) If you have a version of chiller
software that has a later revision code than the compatible programs shown in Table 3, it is likely that
>
program CSC1
01> is compatible with it; however, it may not be. To find out for sure, contact
McQuayService.
File Names
In all cases, the file names of the compatible programs shown in Table 3 are the same as the program
codes except that they also include a “COD” extension. For example, the file for program PC209A is
called “PC209A.COD.”
) can be any letter.
OM127-17
Table 3. Program Code CSC1*01E Software Compatibility
Series-200 CentrifugalCFG1*01C and laterCFG1*01B and earlier
CFG3*01C and laterCFG3*01B and earlier
CFG5*01C and laterCFG5*01B and earlier
Series-100 Centrifugal: Display Proc.PDR09A and laterPDR08* and earlier
PDM09A and laterPDM08* and earlier
Series-100 Centrifugal: Control Proc.PC209A and laterPC208* and earlier
PC409A and laterPC408* and earlier
PC509A and laterPC508* and earlier
ReciprocatingRCP1*01B and laterRCP1*01A
RCP2*01B and laterRCP2*01A
noneAWR-*12* and earlier
ScrewSC1*U01A
SC2*U18D and laterSC2*18C and earlier
SC3*E18C and laterSC3*E18B and earlier
SC4*E18C and laterSC4*E18B and earlier
J&E HallJEH**01K and later
GlobalAG_UU01A and laterGZ_2E01A
The menus within the CSC refer to the chiller software in generic terms. Table 4 lists each chiller
model and the generic term for its software.
Table 4. CSC Chiller Software Terms
Chiller ModelSoftware Term in CSC Menus
PFHCentrif-100 (Series 100)
PEHCentrif-100 (Series 100)
WHRRecip-Standard
ALRRecip-Standard
PFSScrew
ALSScrew
AGZ (Global Scroll)AGU
AGR (Global
Reciprocating)
AGS (Global Screw)AGU
J&E HallHallScrew
Centrif-200 (Series 200)
Centrif-200 (Series 200)
Recip-European
Recip-European
AGU
8OM127-1
Getting Started
The MicroTech Chiller System Controller (CSC) is a self-contained device that is capable of
monitoring and controlling up to 12 McQuay centrifugal, reciprocating, screw, global, or J & E Hall
screw chillers via network communications. It can also monitor and control a variety of system
equipment such as cooling tower fans, bypass valves, and secondary pumps. You can display and
modify information in the CSC with either of the following methods:
• Using the keypad/display at the CSC
• Using an optional PC equipped with the Monitor program
In addition to system data, the CSC’s keypad/display can show a summary of important data for each
chiller. To modify information in a chiller controller, you must use either the Monitor program or the
keypad/display at that chiller.
The “Getting Started” sections describe how to use the CSC’s keypad/display. For information on
using the optional Monitor program, see the Monitor User’s Manual. The last “Getting Started”
section describes how to set up the CSC and its associated chillers for normal operation.
Chiller Definition
As used throughout this manual, the word “chiller” means chiller in all cases except for dualcompressor centrifugals. For these machines, each compressor—along with its associated MicroTech
controller—is considered a “chiller.”
Using the Keypad/Display
The Keypad/Display, shown in Figure 2, is provided with all MicroTech Chiller System Controllers.
With the keypad/display you can monitor operating conditions, alarms, control variables, and
schedules. After you enter the password, you can edit setpoints, variables, and schedules.
The keypad-accessible information in the MicroTech controller is organized in a menu structure to
provide quick access. As shown in Figure 3, this structure is divided into three levels: categories,
menus, and items. The category, which is the highest level in the structure, can be “Status,” “Control,”
or “Alarm.” The name of each category describes the basic purpose of the menus it contains.
Complete information on the contents of each menu is included in the following “Keypad/Display
Menu Reference” section.
Figure 3. Keypad Accessible Menu Structure
Item
Status
Menu 1
Items on
Screen 1
Menu 2
Items on
Screen 1
Menu 9Menu 10Menu 11Menu 30Menu 31Menu 32Menu 35
Items on
Screen 1
Category
Menu
Status Category
Menus in the Status category contain information about the current operation of the chiller system.
ControlAlarm
Items on
Screen 1
Items on
Screen 1
Items on
Screen 2
Items on
Screen 3
Items on
Screen 4
Items on
Screen 5
Items on
Screen 1
Items on
Screen 2
Items on
Screen 3
Items on
Screen 4
Items on
Screen 5
Items on
Screen 1
Items on
Screen 2
Items on
Screen 3
Items on
Screen 1
Items on
Screen 2
Items on
Screen 3
Message
Board
a0072
They also include important information about the current operating conditions in each chiller. The
fields in these menu items provide status information only and cannot be changed with the keypad.
Control Category
Menus in the Control category contain variables that define how the CSC operates. After the
password is entered, most fields in these menu items can be changed with the keypad.
Alarm Category
Menus in the Alarm category contain current and previous alarm information. They also include
variables that allow you to customize the setup of the CSC’s Alarm Horn and Alarm Output.
Display Format
The information stored in the CSC’s menu structure can be viewed on the 4-line by 40-character LCD
display. As shown in Figure 4, the current menu is displayed on the top line and the current items are
displayed on the three lines below. An item line may contain one full-row item or two half-row items,
and each item contains one or more fields that convey varying information. These fields may or may
not be adjustable.
Figure 4. LCD Display Format
Screen
Menu line
Item line 1
Item line 2
Item line 3
24.Schedule 14:34 Jun-03-95
Override= 0.00 HrsNMP Schedule= NA
One Event= Jun–12 18:30 for 2.25 Hrs
Sun 00:00–00:00Mon 06:30–17:30
FieldHalf-row item
Full-row itemNext screen indicator
10OM127-1
Previous screen indicator
a0071
In addition to the current menu, the menu line also shows the time, date, and a variety of other
messages that help you use the keypad.
The menu line and the three item lines are contained on a screen. A menu may contain one or more
screens. Each screen of a multi-screen menu (for example, menu 11) shows the same menu line and
different item lines. (The item lines do not scroll.) A down arrow in the display indicates that you can
display another screen of items by pressing the
indicates that you can display a previous screen of items by pressing the
Tabular Format
Some menus contain data that is displayed in a tabular format instead of the standard half- or full-row
NEXT ITEM
( ) key. An up arrow in the display
PREV ITEM
key ( ).
item format shown in Figure 4. In the tabular format, the column headings are displayed on item line
1 and the data fields are displayed on item lines 2 and 3. If there is a stub, it is shown on the left side
of the screen. If there are multiple screens, the menu line and item line 1 (headings) are the same on
each screen. The CSC’s menu 27, “Optimal Minutes,” is an example of a tabular menu.
Password Protection
The MicroTech controller includes password protection to guard against the entry of inadvertent or
unauthorized changes. When you attempt to change the value of an adjustable variable with the
keypad, the controller prompts you to enter the password. If the correct password is entered, the
controller allows you to make changes as desired. Five minutes after the last keystroke is made, the
controller prevents further changes until the password is re-entered.
The keypad password for all controllers is the following keystroke sequence:
ENTER
. It is not adjustable. See “Key Functions” below for more information.
ENTER, ENTER, ENTER
,
Keypad/Display Modes
The keypad/display has two modes of operation: Normal and Change Values. Depending on the
keypad/display mode, the function of each key changes. For more information, see “Key Functions.”
Normal Mode
In the Normal mode, you can use the keypad to move around the menu structure shown in Figure 3.
You can also clear alarms and get Help on using the keypad by pressing the
CLEAR
(Help) key. If you
want to edit a certain variable, first display it on the current screen and then go to the Change Values
mode by pressing
INCR, DECR
, or
ENTER
. The controller may prompt you for the password. The time
and date on the menu line are replaced by the message “<Change Values Mode>.”
Change Values Mode
In the Change Values mode, you can use the keypad to move around the screen and to change the
values of selected (flashing) fields. Any adjustable field on the current screen can be changed during
a change-values editing session: to edit a field on a different screen, you must first return to the
Normal mode and select the new screen. To return to the Normal mode, press the
Key Functions
The MicroTech controller’s keypad consists of 12 pressure sensitive membrane switches, which are
CLEAR
key.
divided into 3 groups: “Category,” “Menu-Item,” and “Action.” See Figure 5.
OM127-111
Figure 5. Keypad
CATEGORY
AlarmStatus
ControlSwitch
MENU - ITEM
Prev.
Item
Next
Item
Next
Menu
Prev.
Menu
ACTION
Help
ClearIncr.
Decr.Enter
a0074
Category Group
Acting like bookmarks in the menu structure, the keys in the Category group provide quick access to
the desired menus. Refer to Figure 3. By using these keys, you can minimize scrolling between menus
with the keys in the Menu-Item group (see below). The keys in the Category group are active only
during the Normal mode.
TATUS
S
Key:
Any time the
STATUS
key is pressed, the first menu in the Status category is
displayed. This is menu 1, “System Status.”
ONTROL
C
Key:
Any time the
CONTROL
key is pressed, the first menu in the Control category is
displayed. This is menu 10, “System Control.”
LARM
A
Key:
Any time the
ALARM
key is pressed, the first menu in the Alarm category is
displayed. This is menu 31, “Current Alarms.”
WITCH
S
Key:
The
SWITCH
key allows you to quickly switch between menus that have closely
related content. For example, if you’re interested in chiller sequencing control,
you could go to menu 1, “System Status,” and then press the
SWITCH
key
successively to see the following menus, which contain chiller sequencing data:
• Menu 1. System Status
• Menu 3. Chiller Status
• Menu 13. Chiller Sequence Order
The three menus in the above example are called a browse sequence
(1¤3¤13¤1). The following “Keypad/Display Menu Reference” section lists the
SWITCH
essential destinations and browse sequences for all applicable menus.
Menu-Item Group: Normal Mode
During the Normal mode, the keys in the Menu-Item group allow you to choose the menu and item
you want to display. Refer to Figure 3. First use the two menu keys to select the menu you want, and
then, if necessary, use the two item keys to display the items you want.
REV MENU
P
Key (
)
:
When the
PREV MENU
key is pressed, the display scrolls to the previous
menu in the structure. This action always occurs unless the current menu is
the first menu.
EXT MENU
N
Key ( ):
When the
NEXT MENU
key is pressed, the display scrolls to the next menu
in the structure. This action always occurs unless the current menu is the
last menu.
REV ITEM
P
Key ( ):
When the
PREV ITEM
key is pressed, the display scrolls to the previous
screen of items in the current menu. This action always occurs unless the
current screen is the first screen.
EXT ITEM
N
Key ( ):
When the
NEXT ITEM
key is pressed, the display scrolls to the next screen
of items in the current menu. This action always occurs unless the current
screen is the last screen.
12OM127-1
Menu-Item Group: Change Values Mode
During the Change Values mode, the keys in the Menu-Item group become “cursor control” keys for
the current screen, allowing you to quickly get to the field(s) you want to edit. For more on editing,
see “Action Group: Change Values Mode.”
Note:
In some instances during the Change Values mode, the flashing “cursor” field disappears
either upon entering the mode or after a keystroke. This is normal. An additional keystroke usually
makes the cursor field reappear.
Action Group: Normal Mode
During the Normal mode, the Action group keys allow you to (1) clear alarms, (2) get Help on using
the keypad/display, or (3) enter the Change Values mode. To enter the Change Values mode, press
INCR, DECR
the
LEAR
C
Key (Help):
, or
ENTER
key.
When the
CLEAR
key is pressed, the display shows Help on using the
keypad/display. This action always occurs except when menu 31, “Current
Alarms,” is in the display. In this instance, pressing
CLEAR
clears a current
CSC alarm. For more on clearing alarms, see the “Alarm Monitoring”
section of this manual.
Action Group: Change Values Mode
During the Change Values mode, the Action group keys allow you to edit values in the fields on the
current screen. When you enter the Change Values mode, the first adjustable field in the first item on
the current screen flashes, indicating that it can be edited with the
INCR
or
DECR
keys. To select
different fields on the screen, use the cursor control keys in the Menu-Item group.
NCR
I
D
ECR
Key (+):
Key (–):
When the
changes to the next higher value or next available selection. After pressing
you cannot select a new field for editing until you press the
When the
INCR
key is pressed, the entry in the item’s selected (flashing) field
ENTER
DECR
key is pressed, the entry in the item’s selected (flashing) field
or
CLEAR
INCR
key.
changes to the next lower value or previous available selection. After you press
NTER
E
Key (=):
DECR
, you cannot select a new field for editing until you press the
CLEAR
key.
When the
ENTER
key is pressed after a value has been changed, the new entry is
ENTER
or
locked in. A message appears on the menu line telling you that the change was
successful. To select another field for editing, use the cursor control keys in the
CLEAR
.
CLEAR
ENTER
key is pressed), the
LEAR
C
Key:
Menu-Item group. To end the edit, press
CLEAR
The
key has two functions in the Change Values mode: (1) when
pressed after a value has been changed (but before the
new entry is canceled and the previous entry is retained; (2) in any other case,
pressing
CLEAR
ends the editing session and returns the keypad/display to the
Normal mode.
,
is
Keypad/Display Exercises
Following are two exercises that guide you through some typical keypad operations. Often there is
more than one way to perform an operation. For example, you can use the Menu-Item keys with or
without the optional Category keys to quickly find the menu you want to display.
Changing a Setpoint
In this exercise, assume that the common chilled water supply temperature is 47.0°F (8.3°C) and
cooler water is required. The water temperature is too warm because not all chillers are on and both
the Minimum Chiller Setpoint and the System Setpoint are 44.0°F (6.6°C). (The system layout is such
that water from chillers that are off mixes with water from chillers that are on.) Using the following
procedure, you change the Minimum Chiller Setpoint to 41.0°F (4.9°C) and thus lower the common
supply temperature.
OM127-113
1. Press
CONTROL
. The first menu of the Control category is displayed. This is menu 10, “System
Control.”
2. Press
NEXT MENU
( ) six times. Menu 16, “Supply Tmp Cntl,” is displayed. The first screen of
this menu is also displayed.
3. Press
NEXT ITEM
( ) once. The second screen is displayed. The “Min Chil Spt=” item is on the
right half of item line 1. This is the Minimum Chiller Setpoint. Assume that it is set to 44.0°F
(6.6°C).
4. Press
5. Press
INCR
ENTER
(+),
DECR
(–) or
ENTER
(=). The controller prompts you for the password.
four times. (This is the password.) The “Password Verified” message is displayed
and then the “<Change Values Mode>” message appears on the menu line.
6. Press
NEXT MENU
( ), which is now a cursor control key, once. The “Min Chil Spt=” item’s only
field starts flashing.
7. Press
8. Press
9. Press
DECR
(–) until the setpoint is 41.0°F (4.9°C).
ENTER
. The “Change Successful” message appears. This means that the new setpoint is
locked in. Now press
SWITCH
twice. The actual supply temperature (“Supply ChW=” item under menu 2,
CLEAR
to end the edit and return to the keypad/display’s Normal mode.
“Temperatures”) is displayed. With the new setpoint entered, this temperature begins to drop.
Clearing a CSC Alarm
In this exercise, assume that a Fault alarm which requires a manual reset occurred in the system. If the
conditions that caused the alarm are gone, use the following procedure to clear the alarm.
1. Press
ALARM
. The Alarm Horn is silenced and the first menu of the Alarm category is displayed.
This is menu 31, “Current Alarms.” The “CSC=” item is also displayed. It probably shows
“None,” but assume that a Fault exists; for example, “No Sec ChW Flow.”
2. Press
CLEAR
. This clears the alarm and returns the CSC to normal operation. The “CSC=” item
automatically changes to “None.”
Keypad/Display Menu Reference
The following tables show every menu, item, and field in the menu structure of the CSC. These menus
and items can all be displayed with the keypad/display. (the Monitor program provides some
additional monitoring features and adjustable variables.)
Using the Tables
The menu tables tell you several things:
• The exact location of each item in the menu structure
• The default value of each adjustable field
• The range of possible values for each field
• The variable name for each item
• The
Figure 5 shows an example of a typical CSC screen and its corresponding menu table.
Location
Each menu table has a “Screen” (Scr.) column and a “Line” column. The Screen column tells you
which screen a particular item is on. The Line column tells you which item line a particular item is on.
For multi-screen menus, this information can be useful because it gives you an idea of the number of
times you need to press the
SWITCH
key destination for each menu
NEXT ITEM
key upon entering the menu.
14OM127-1
Default Value
The tables for menus in the Control and Alarm categories show the default, factory set values of every
adjustable field. These are shown in the “Name” column in bold italic. For many variables, the default
values are typical values that may not need to be changed; for example, control loop parameters such
as deadbands and mod limits. Other variables must be set in accordance with the application, and thus
their default values have little meaning; for example, the First On Chiller variable shown in Figure 6.
Range
The range of possible values for every field is shown in the “Range” column. Since many items in the
Control and Alarm categories have more than one field, the tables for these menus also have a “Field
No.” column. If there is a number in the Field No. column, it indicates that the field is adjustable and
thus it can be selected with the cursor control keys during the Change Values mode. If there is a dash
(–) in the Field No. column, it indicates that the field is not adjustable. The range for each field is
shown in the adjacent Range column.
Using Figure 6 as an example, notice that all items on the screen have one adjustable field except “On
First=,” which has two. The “On First=” item’s first field can be set to “N/A,” “#1,” or “#2” through
“#12.” Its second field can be set to either “at Stage Two” or “Last.”
Note:
The resolution of all adjustable temperature fields is 0.5°F (0.2–0.3°C).
Variable Name
Every item in the CSC’s menu structure represents a variable (adjustable or status only). The item
names that appear in the display are usually abbreviations of the variable names, which are listed in
the “Variable Name” column. Variable names are used in the text of this manual to describe the
operation of the CSC and its associated chillers.
Figure 6. Example of Screen and Corresponding Menu Table (Screen 2 of Menu 11 Shown)
Screen 2
Menu line
Item line 1
Item line 2
Item line 3
Scr.LineName
21
2
3On Last= NA & Off First1N/A, #1 – #12Last On Chiller
WITCH
S
Key Destination:
S
Key Destination
WITCH
At the bottom of each menu table, the
SWITCH
key destination is the menu the CSC displays after the
menu 11 is in the display, pressing
11.Chil Sequencing 15:20 Jun-03-95
Standby= #1
On First= #2 & Off at Stage Two
On Last= #3 & Off First
Adjustable Field 1
(default values: bold italic
Standby=
On First= NA & Off
NA
Menu 3. Chiller Status
Last
Adjustable Field 2
)
SWITCH
SWITCH
displays menu 3.
FieldRangeVariable Name
1N/A, #1 – #12Standby Chiller
1N/A, #1 – #12First On Chiller
2at Stage Two
Last
key destination for that menu (if any) is shown. The
SWITCH
key is pressed. For example, if
a0073
OM127-115
Browse Sequences
A browse sequence is a series of closely related menus that you can display cyclically by repeatedly
pressing the
cooling tower control—without having to navigate through unrelated menus. You can enter a browse
sequence at any menu, and if you press
from.
Browse sequences include only menus that contain information you may need on a day-to-day basis;
they do not include menus that contain setup information.
TopicBrowse Sequence Menus
Chiller Sequencing1¤3¤13¤1
System/Scheduling10¤24¤10
Chilled Water Temperatures2¤16¤17¤2
Cooling Tower6¤18¤19¤20¤6
Load Limit ing5¤14¤15¤5
Chilled Water Flow7¤21¤22¤7
SWITCH
key. They allow you to focus on a specific chiller system function—for example,
SWITCH
enough times, you return to the menu you started
Not all menus that have
SWITCH
you press
from one of these menus, it usually brings you to a related browse sequence. For example, if
SWITCH
SWITCH
key destinations are part of a browse sequence. However, if you press
while menu 11 is in the display, you enter the Chiller Sequencing browse sequence
at menu 3.
Status Menus
The Status category includes menus 1 through 9. Following are brief descriptions of them.
System Status
Menu 1, “System Status,” tells you the current overall status of the CSC and its associated chillers.
For more information, see the “Determining Chiller System Status” section in the “Operator’s Guide”
portion of this manual.
Temperatures
Menu 2, “Temperatures,” provides the current system water temperatures and the outdoor air
temperature. Except for the chilled water supply sensor, these temperature sensors are optional. If the
display shows “Open” or “Short,” it is likely that the sensor has not been installed.
Chiller Status
Menu 3, “Chiller Status,” tells you whether each chiller is currently starting, on, stopping, or off. If a
chiller is off, the chiller status tells whether it is disabled at the chiller or by the CSC. The load on
each chiller and the water temperatures at each chiller are also displayed. The chiller load is in
percent of rated load amps (% RLA) for centrifugal and percent of available stages that are active for
reciprocating and screw.
Chiller Operating Hours
Menu 4, “Operating Hours,” gives you run-time history for each chiller in the system. Run time is
accumulated whenever a compressor is actually running.
Load Limiting Status
Menu 5, “Load Limit Status,” tells you which of the three percent-of-capacity load limiting functions
are currently affecting the chillers: demand limiting, load balancing, or start-up unloading. A value of
100% means that no load limiting is occurring. The current capacity limit on each individual chiller,
which is the minimum value produced by the three functions, is also shown on menu 5. For more
information, see the “Determining Chiller System Status” section in the “Operator’s Guide” portion of
this manual.
16OM127-1
Cooling Tower Status
Menu 6, “Tower Status,” tells you the current status of the cooling tower system. For more
information, see the “Determining Chiller System Status” section in the “Operator’s Guide” portion of
this manual.
Flow To Load
Menu 7, “Flow To Load,” tells you the current status of the chilled water distribution system, which
may include secondary pumps or a differential pressure bypass valve. For more information, see the
“Determining Chiller System Status” section in the “Operator’s Guide” portion of this manual.
Miscellaneous Inputs
Menu 8, “Misc Inputs,” tells you the flow rate in the decoupler line and the states of the external
start/stop, chilled water reset override, and cooling tower alarm inputs. The conditioned (0–5 Vdc)
values of the external demand limiting and external chilled water reset signals are also displayed.
Miscellaneous Status
Menu 9, “Misc Status,” tells you the current value of the Stage-Up Inhibit Level variable. This signal
can be sent to the CSC by a MicroTech Network Master Panel that has a demand meter connected to
it or by a building automation system via Open Protocol™. The signal and its corresponding setpoint
(menu 11) can be used to prevent further chiller system loading when a certain electrical demand
target is reached.
Table 5. Menu 1 System Status
ScrLineName
11State= On:Schedule
(typical values shown italic)
RangeVariable Name
Off:Unocc
•
Off:Manual
•
Off:Ambient
•
Off:Network
•
Off:Alarm
•
Recirculate
•
On:Schedule
•
On:Input
•
On:Manual
•
On:Network
•
Free Clg
•
System Spt= 44.0°F (6.6°C)32.0 – 60.0°F
0.0 – 20.0°C
CSC Operating State
System Setpoint (chilled water
{
supply)
2Chiller Stage= 20 – 12Current Chiller Stage
Average Load= 67%0 – 125%Average Chiller Load
(operational chillers)
3Chillers On= #1 #2 __ __ __ __ __ __
#1 - #12
|
Chiller Status Bitset
__ __ __ __
WITCH
S
Key Destination:
:
Notes
1. Program CSC1S01
2. If a chiller is either starting or running, that chiller’s number appears in the item line.
Menu 3. Chiller Status
>
only.
Table 6. Menu 2 Temperatures
ScrLineName
11Supply ChW= 44.2°F (6.7°C)–45.0 – 255.0°F
OM127-117
(typical values shown italic)
RangeVariable Name
–40.0 – 125.0°C
{
Return ChW= 54.6°F (12.6°C)–45.0 – 255.0°F, N/A
–40.0 – 125.0°C{, N/A
Chilled Water Supply
Temperature (common)
Chilled Water Return
Temperature
ScrLineName
(typical values shown italic)
RangeVariable Name
2Ent CondW= 79.5°F (26.4°C)–45.0 – 255.0°F, N/A
–40.0 – 125.0°C{, N/A
Lvg CondW= 92.1°F (33.4°C)–45.0 – 255.0°F, N/A
–40.0 – 125.0°C{, N/A
3Decoupler= 45.1°F (7.3°C)–45.0 – 255.0°F, N/A
–40.0 – 125.0°C{, N/A
Outdoor Air= 90.0°F (32.2°C)–45.0 – 255.0°F, N/A
–40.0 – 125.0°C{, N/A
WITCH
S
Key Destination:
Notes:
1. Program CSC1S01
Menu 16. Chilled Water Supply Temperature Control
>
only.
Table 7. Menu 3 Chiller Status
Common Entering Condenser
Water Temperature
Common Leaving Condenser
Water Temperature
Decoupler Temperature
Outdoor Air Temperature
ScrLineName
11#1 Status= Running
(typical values shown italic)
RangeVariable Name
Off:Local
•
Off:CSC
•
Starting
•
Running
•
Stopping
•
Comm Loss
•
N/A
•
Chiller #1 Status
Load= 54%0 – 125%Chiller #1 Load
2Ent Evap= 53.6°F (12.0°C)–45.0 – 255.0°F
–40.0 – 125.0°C
Ent Cond= 75.7°F (24.3°C)–45.0 – 255.0°F
–40.0 – 125.0°C
3Lvg Evap= 44.2°F (6.8°C)–45.0 – 255.0°F
–40.0 – 125.0°C
Lvg Cond= 85.6°F (29.8°C)–45.0 – 255.0°F
–40.0 – 125.0°C
{
{
{
{
Chiller #1 Entering Evaporator
Water Temperature
Chiller #1 Entering Condenser
Water Temperature
Chiller #1 Leaving Evaporator
Water Temperature
Chiller #1 Leaving Condenser
Water Temperature
21#2 Status= Running(same as Chiller #1 Status)Chiller #2 Status
The Control category includes menus 10 through 30. Following are brief descriptions of them.
System Control
Menu 10, “System Control,” contains the CSC Control Mode variable, which allows you to set up the
CSC for automatic or manual operation. It also contains the low ambient lockout variables that are
used to prevent chiller system operation when the outdoor air temperature is below a set temperature.
For more information, see the “Auto/Manual Operation” section in the “Operator’s Guide” portion of
this manual.
Chiller Sequencing
Menu 11, “Chil Sequencing,” can be used to designate whether the chiller sequence order is set
manually or automatically and whether certain chillers are designated as standby, first on, or last on. It
can also be used to set up the CSC’s chiller sequencing control logic. For more information, see the
“Chiller Sequencing Control” section of this manual.
Chiller Staging Factors
Menu 12, “Chil Stg Factors,” contains the variables that cause the active chiller stage number to
increase or decrease as the cooling load varies. Individual variables are provided for each chiller
stage. Chiller staging is based on the average load of all operational chillers, an adjustable time delay,
and in some applications, flow rate through the decoupler (bypass) line.
In addition to the chiller staging variables, a limit on the number of cooling tower stages can be
specified. For more information, see the “Chiller Sequencing Control” section of this manual.
Chiller Sequence Order
Menu 13, “Chiller Order,” shows the order in which the CSC sequences chillers as the cooling load
varies. When the CSC is set up to change the sequence order automatically, the variables in menu 13
are status only (non-adjustable). When the CSC is set up to allow manual sequence order changes, the
variables in menu 13 are used to set a fixed sequence order.
In either case, the sequence order is organized according to chiller stages rather than individual
chillers. A chiller stage is a defined set of chillers; for example, stage 1 might consist of Chiller #2,
and stage 2 might consist of Chiller #1 and Chiller #2. (In this instance, Chiller #2 would be “lead”
and Chiller #1 would be “lag.”) This approach provides more sequencing flexibility because chillers
can be either started or stopped in sets of one or more as the cooling load either increases or
decreases. For more information, see the “Chiller Sequencing Control” section of this manual.
Load Limiting Setup
Menu 14, “Load Limiting,” contains variables that allow you to set up the two system-wide, percentof-capacity load limiting functions: load balancing and demand limiting. Both are optional.
Load balancing causes all centrifugal chillers to operate at about the same capacity (% RLA). It is
typically used when there are dual-compressor chillers or chillers piped in series.
Demand limiting prevents chillers from operating above a specified capacity (% RLA for centrifugal;
stages for reciprocating and screw). The demand-limiting signal can be either an external input
(4-20 mA, 1–5 Vdc, 2–10 Vdc) or a network input received via Open Protocol. For more information,
see the “Load Limiting Control” of this manual.
OM127-123
Start-Up Unloading
Menu 15, “Start-Up Unload,” contains variables that allow you to set up the start-up-unloading load
limiting function. Start-up unloading is different from load balancing and demand limiting in that it
works on separate groups of chillers (centrifugal only) rather than all chillers. Start-up unloading
causes all operational compressors in a group to unload when another compressor in the same group
starts up. It is typically used only for dual-compressor chillers. For more information, see the “Load
Limiting Control” section of this manual.
Chilled Water Supply Temperature Control
Menu 16, “Supply Tmp Cntl,” can be used to specify whether the CSC controls common (system
supply) chilled water temperature or controls unit (leaving evaporator) chilled water temperature.
Either control method can be used with any of the reset options. For more information, see the
“Chilled Water Temperature Control” section of this manual.
Chilled Water Supply Temperature Reset
Menu 17, “Supply Tmp Reset,” contains variables that are used to reset the chilled water supply
temperature setpoint. Four types of reset are available. For more information, see the “Chilled Water
Temperature Control” section of this manual.
Cooling Tower Stages
Menu 18, “Clg Tower Stages,” contains variables that control staging for the cooling tower system.
Twelve stages are possible, and each stage has a separate setpoint. For more information, see the
“Cooling Tower Control” section of this manual.
Cooling Tower Output Order
Menu 19, “Twr Output Order,” can be set the order in which the CSC stages tower outputs as the heat
rejection requirement varies. Like a chiller stage, a tower stage is a defined set of tower outputs; for
example, stage 1 might consist of Fan #1, stage 2 of Fan #2, and stage 3 of Fan #1 and #2. For more
information, see the “Cooling Tower Control” section of this manual.
Cooling Tower Bypass Valve
Menu 20, “Clg Tower Valve,” contains variables that control the bypass valve for the cooling tower
system. The valve can be set up to modulate either before tower stage 1 is activated or between tower
stages. In either case, you can set an initial valve position function, which sets the bypass valve
position as appropriate for the outdoor air temperature during system start-up. For more information,
see the “Cooling Tower Control” section in of this manual.
Load Flow Control
Menu 21, “Load Flow Cntl,” contains variables that can be used to set up the chilled water system
flow control. Bypass valve control and three types of secondary pump logic are possible. Secondary
pumps can be fixed or variable speed. For more information, see the “Chilled Water Flow Control”
section of this manual.
Secondary Pump Sequence Order
Menu 22, “Sec Pump Order,” can be used to set the order in which the CSC sequences secondary
pumps to maintain the differential pressure across the supply and return lines. Like a chiller stage, a
pump stage is a defined set of pumps; for example, stage 1 might consist of Pump #1, stage 2 of Pump
#1 and #2, and stage 3 of Pump #1, #2, and #3. For more information, see the “Chilled Water Flow
Control” section of this manual.
Time/Date
Menu 23, “Time/Date,” allows you to adjust the current time, day, and date. For more information,
see the “Scheduling” section of this manual.
24OM127-1
Schedule
Menu 24, “Schedule,” contains the CSC’s internal scheduling variables. It also includes an operator
override timer and a one-event schedule that can be used to enable chiller system operation for a
specified time period. For more information, see the “Scheduling” and “Auto/Manual Operation”
sections of this manual.
Holiday Date
Menu 25, “Holiday Date,” allows you to schedule 12 holiday dates. Each date can be assigned a
duration from 1 to 31 days. On each day of the holiday period, the holiday schedule entered under
menu 24 is used. For more information, see the “Scheduling” section of this manual.
Optimal Start
Menu 26, “Optimal Start,” contains variables that are used to set up the CSC’s adaptive optimal start
feature. Optimal start uses the scheduled start time, the outdoor air temperature, and the chilled water
loop temperature to determine the best possible time to enable chiller system operation. For more
information, see the “Scheduling” section of this manual.
Table of Optimal Start Time Increments
Menu 27, “Optimal Minutes,” contains a table of time increments (in minutes) that are subtracted
from the CSC’s normal scheduled start time to get the optimal start time. The table value that is used
for any particular day is based on the outdoor air and chilled water loop temperatures. For more
information, see the “Scheduling” section of this manual.
Service
Menu 28, “Service,” contains CSC setup and service related items. For more information, see the
following “CSC and Chiller Controller Initial Setup” section. The last item on screen 1, “IDENT=,”
displays the CSC’s program code.
Chiller Setup
Menu 29, “Chiller Setup,” contains variables that define each chiller associated with the CSC. For
more information, see the following “CSC and Chiller Controller Initial Setup” section.
Service Testing
Menu 30, “Service Testing,” contains variables that allow a service technician to manually control the
CSC’s digital and analog outputs. This would normally be done only during system commissioning or
when service is required. For more information, see Bulletin No. IM 618 and the “Auto/Manual
Operation” section in the “Operator’s Guide” portion of this manual.
Table 13. Menu 10, System Control
ScrLineName
11
2
3
S
Key Destination: Menu 24. Schedule
WITCH
Notes:
1. Program CSC1S01
(default values: bold italic
CSC Control Mode=
Rapid Restart Time=
Low Amb Lockout=
Low Amb Spt=
>
only.
50.0°F (9.9°C)
Manual Off
10 Sec
No
FieldRangeVariable Name
)
1
1
1No
115.0 – 99.5°F
Manual Off
•
Automatic
•
Manual On
•
Service Testing
•
0 – 60 Sec
•
1 – 60 Min
•
1 – 60 Hr
•
Yes
–9.5 – 37.4°C
CSC Control Mode
Rapid Restart Time
Low Ambient Lockout Flag
Low Ambient Lockout Setpoint
{
OM127-125
Table 14. Menu 11, Chiller Sequencing
ScrLineName
11
(default values: bold italic
Option=
Automatic
FieldRangeVariable Name
)
1Fixed
Chiller Sequence Order Option
Automatic
2
Control Type=
Standard
1Standard
Chiller Sequencing Control Type
Decoupled
21
2
Standby=
NA
{
On First= NA & Off
Last
|
1NA, #1 – #12Standby Chiller
1NA, #1 – #12First On Chiller
2at Stage Two
Last
3
31
On Last= NA & Off First
Resequence Day/Time=
|
N/A 00:00
1NA, #1 – #12Last On Chiller
1
N/A
•
Sun – Sat
•
Dly
•
Hol
•
Now
•
}
Chiller Resequence Day/Time
20 – 23
30 – 59
2
Inhibit Stage-Up After
23:59
10 – 23Inhibit Stage-Up After Time
20 – 59
3
Stage-Up Inhibit Setpoint=
None
1None
Stage-Up Inhibit Setpoint
1 – 11
41
Number Of Chillers=
2
Number Of Stages=
3
Stage-Up Differential=
3
3
~
+1.0°F
(+0.5°C)
51Decoupler Temperature Diff=
+2.0°F (+1.1°C)
2
Decoupler Flow Factor=
1.10
11 – 12Number Of Chillers
11 – 12Number Of Chiller Stages
10.0 – 9.5°F
0.0 – 5.2°C
10.0 – 9.5°F
0.0 – 5.2°C
Chiller Stage-Up Differential
Decoupler Stage-Up Temperature
Differential
10.75 – 1.50Decoupler Stage-Down Flow Rate
Factor
WITCH
S
Key Destination:
:
Notes
1. If a standby chiller is designated, it is automatically placed only in the highest stage (menu 13) regardless of the Chiller Sequence
Order Option setting. If the Chiller Sequence Order Option is set to “Automatic,” the Last On Chiller variable is automatically set
equal to the Standby Chiller variable.
2. The First On Chiller and Last On Chiller variables have meaning only when the Chiller Sequence Order Option is set to
“Automatic.” The controller does not allow the same chiller to be designated both first on and last on.
3. The “Now” selection automatically changes to “N/A” after the resequence day/time function is executed.
4. The Number Of Chiller Stages variable is adjustable only when the Chiller Sequence Order Option is set to “Fixed.” If the Chiller
Sequence Order Option is set to “Automatic,” the Number Of Chiller Stages variable is automatically set equal to the Number Of
Chillers variable.
5. Program CSC1S01
Menu 3. Chiller Status
>
only.
Table 15. Menu 12, Chiller Staging Factors
ScrLineName
11Stage 1:(screen name)
2
3
21Stage 2:(screen name)
2
26OM127-1
(default values: bold italic
Stage-Up Load=
Stage-Dn Load=
Time Delay=
95%
NA%
5 Min
Max Tower Stage=
Stage-Up Load=
Stage-Dn Load=
95%
50%
FieldRangeVariable Name
)
1NA, 1 – 99%Chiller Stage 1 Stage-Up Setpoint
{
–––
12 – 60 MinChiller Stage 1 Delay Time
1
1NA, 1 – 12Chiller Stage 1 Max Tower Stage
1NA, 1 – 99%Chiller Stage 2 Stage-Up Setpoint
1NA, 1 – 99%Chiller Stage 2 Stage-Down
Setpoint
ScrLineName
3
(default values: bold italic
Time Delay=
5 Min
Max Tower Stage=
FieldRangeVariable Name
)
12 – 60 MinChiller Stage 2 Delay Time
2
1NA, 1 – 12Chiller Stage 2 Max Tower Stage
31Stage 3:(screen name)
2
3
Stage-Up Load=
Stage-Dn Load=
Time Delay=
5 Min
Max Tower Stage=
95%
67%
3
1NA, 1 – 99%Chiller Stage 3 Stage-Up Setpoint
1NA, 1 – 99%Chiller Stage 3 Stage-Down
12 – 60 MinChiller Stage 3 Delay Time
11 – 12Chiller Stage 3 Max Tower Stage
41Stage 4:(screen name)
2
3
Stage-Up Load=
Stage-Dn Load=
Time Delay=
5 Min
Max Tower Stage=
95%
75%
4
1NA, 1 – 99%Chiller Stage 4 Stage-Up Setpoint
1NA, 1 – 99%Chiller Stage 4 Stage-Down
12 – 60 MinChiller Stage 4 Delay Time
11 – 12Chiller Stage 4 Max Tower Stage
51Stage 5:(screen name)
2
3
Stage-Up Load=
Stage-Dn Load=
Time Delay=
5 Min
Max Tower Stage=
95%
80%
5
1NA, 1 – 99%Chiller Stage 5 Stage-Up Setpoint
1NA, 1 – 99%Chiller Stage 5 Stage-Down
12 – 60 MinChiller Stage 5 Delay Time
11 – 12Chiller Stage 5 Max Tower Stage
61Stage 6:(screen name)
2
3
Stage-Up Load=
Stage-Dn Load=
Time Delay=
5 Min
Max Tower Stage=
95%
80%
6
1NA, 1 – 99%Chiller Stage 6 Stage-Up Setpoint
1NA, 1 – 99%Chiller Stage 6 Stage-Down
12 – 60 MinChiller Stage 6 Delay Time
11 – 12Chiller Stage 6 Max Tower Stage
71Stage 7:(screen name)
2
3
Stage-Up Load=
Stage-Dn Load=
Time Delay=
5 Min
Max Tower Stage=
95%
80%
7
1NA, 1 – 99%Chiller Stage 7 Stage-Up Setpoint
1NA, 1 – 99%Chiller Stage 7 Stage-Down
12 – 60 MinChiller Stage 7 Delay Time
11 – 12Chiller Stage 7 Max Tower Stage
81Stage 8:(screen name)
2
3
Stage-Up Load=
Stage-Dn Load=
Time Delay=
5 Min
Max Tower Stage=
95%
80%
8
1NA, 1 – 99%Chiller Stage 8 Stage-Up Setpoint
1NA, 1 – 99%Chiller Stage 8 Stage-Down
12 – 60 MinChiller Stage 8 Delay Time
11 – 12Chiller Stage 8 Max Tower Stage
91Stage 9:(screen name)
2
3
Stage-Up Load=
Stage-Dn Load=
Time Delay=
5 Min
Max Tower Stage=
95%
80%
9
1NA, 1 – 99%Chiller Stage 9 Stage-Up Setpoint
1NA, 1 – 99%Chiller Stage 9 Stage-Down
12 – 60 MinChiller Stage 9 Delay Time
11 – 12Chiller Stage 9 Max Tower Stage
101Stage 10:(screen name)
2
Stage-Up Load=
95%
1NA, 1 – 99%Chiller Stage 10 Stage-Up
Setpoint
Setpoint
Setpoint
Setpoint
Setpoint
Setpoint
Setpoint
Setpoint
OM127-127
ScrLineName
3
(default values: bold italic
Stage-Dn Load=
Time Delay=
80%
5 Min
Max Tower Stage=
10
FieldRangeVariable Name
)
1NA, 1 – 99%Chiller Stage 10 Stage-Down
12 – 60 MinChiller Stage 10 Delay Time
11 – 12Chiller Stage 10 Max Tower Stage
111Stage 11:(screen name)
2
3
Stage-Up Load=
Stage-Dn Load=
Time Delay=
95%
80%
5 Min
Max Tower Stage=
11
1NA, 1 – 99%Chiller Stage 11 Stage-Up
1NA, 1 – 99%Chiller Stage 11 Stage-Down
12 – 60 MinChiller Stage 11 Delay Time
11 – 12Chiller Stage 11 Max Tower Stage
121Stage 12:(screen name)
2
Stage-Up Load=
Stage-Dn Load=
3
Time Delay=
Max Tower Stage=
WITCH
S
Key Destination
Notes:
1. This item is not used.
95%
80%
5 Min
12
: Menu 3. Chiller Status
1NA, 1 – 99%Chiller Stage 12 Stage-Up
1NA, 1 – 99%Chiller Stage 12 Stage-Down
12 – 60 MinChiller Stage 12 Delay Time
11 – 12Chiller Stage 12 Max Tower Stage
Setpoint
Setpoint
Setpoint
Setpoint
Setpoint
Table 16. Menu 13, Chiller Sequence Order
ScrLineName
11
2
3
21
2
3
31
2
(default values: bold italic
Stage 1=
#1 x x x x x x x x xx xx xx
{
Stage 2=
#1 #2 x x x x x x x xx xx
{
xx
Stage 3=
#1 #2 #3 x x x x x x xx xx
{
xx
Stage 4=
#1 #2 #3 #4 x x x x x xx
{
xx xx
Stage 5=
#1 #2 #3 #4 #5 x x x x xx
{
xx xx
Stage 6=
#1 #2 #3 #4 #5 #6 x x x xx
{
xx xx
Stage 7=
#1 #2 #3 #4 #5 #6 #7 x x
{
xx xx xx
Stage 8=
#1 #2 #3 #4 #5 #6 #7 #8 x
{
xx xx xx
)
FieldRangeVariable Name
1x, #1Chiller Stage 1 Bitset
2x, #2
3x, #3
4x, #4
5x, #5
6x, #6
7x, #7
8x, #8
9x, #9
10xx, #10
11xx, #11
12xx, #12
(same as Stage 1 Bitset)Chiller Stage 2 Bitset
(same as Stage 1 Bitset)Chiller Stage 3 Bitset
(same as Stage 1 Bitset)Chiller Stage 4 Bitset
(same as Stage 1 Bitset)Chiller Stage 5 Bitset
(same as Stage 1 Bitset)Chiller Stage 6 Bitset
(same as Stage 1 Bitset)Chiller Stage 7 Bitset
(same as Stage 1 Bitset)Chiller Stage 8 Bitset
28OM127-1
ScrLineName
3
41
2
2
WITCH
S
Key Destination
:
Notes
1. The fields for this item are adjustable when the Chiller Sequence Order Option (menu 11) is set to “Fixed.” They are not
adjustable when the Chiller Sequence Order Option is set to “Automatic”; they show the current values set by the CSC.
(default values: bold italic
Stage 9=
#9
Stage 10=
#9
Stage 11=
#9
Stage 12=
#9
#1 #2 #3 #4
{
xx xx xx
#1 #2 #3 #4
{
#10 xx xx
#1 #2 #3 #4
{
#10 #11 xx
#1 #2 #3 #4
{
#10 #11 #12
: Menu 1. System Status
#5 #6 #7 #8
#5 #6 #7 #8
#5 #6 #7 #8
#5 #6 #7 #8
FieldRangeVariable Name
)
(same as Stage 1 Bitset)Chiller Stage 9 Bitset
(same as Stage 1 Bitset)Chiller Stage 10 Bitset
(same as Stage 1 Bitset)Chiller Stage 11 Bitset
(same as Stage 1 Bitset)Chiller Stage 12 Bitset
Table 17. Menu 14, Load Limiting Setup
ScrLineName
11
2
3
WITCH
S
Key Destination:
(default values: bold italic
Load Balancing=
No
Capacity Difference Limit=
Demand Limiting Type=
Menu 15. Start-Up Unloading
None
5%
Table 18. Menu 15, Start-Up Unloading
ScrLineName
11
2
3
1
2
3
21
2
3
1
2
3
WITCH
S
Key Destination:
(default values: bold italic
Chiller #1 Group=
Chiller #2 Group=
Chiller #3 Group=
Chiller #4 Group=
Chiller #5 Group=
Chiller #6 Group=
Chiller #7 Group=
Chiller #8 Group=
Chiller #9 Group=
Chiller #10 Group=
Chiller #11 Group=
Chiller #12 Group=
Menu 5. Load Limiting Status
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
FieldRangeVariable Name
)
1No
Load Balancing Flag
Yes
12 – 20%Load Balancing Capacity
Difference Limit
1None
Demand Limiting Type
External
Open Protocol
)
FieldRangeVariable Name
1NA, 1 – 6Chiller #1 Group
1NA, 1 – 6Chiller #2 Group
1NA, 1 – 6Chiller #3 Group
1NA, 1 – 6Chiller #4 Group
1NA, 1 – 6Chiller #5 Group
1NA, 1 – 6Chiller #6 Group
1NA, 1 – 6Chiller #7 Group
1NA, 1 – 6Chiller #8 Group
1NA, 1 – 6Chiller #9 Group
1NA, 1 – 6Chiller #10 Group
1NA, 1 – 6Chiller #11 Group
1NA, 1 – 6Chiller #12 Group
Table 19. Menu 16, Chilled Water Supply Temperature Control
ScrLineName
11
2
3
21
OM127-129
(default values: bold italic)
Control=
System Setpoint=
Chiller Setpoint=
Deadband=
Unit
44.0°F (6.6°C)
44.0°F (6.6°C)
±0.5°F (±0.2°C)
FieldRangeVariable Name
1Unit
10.0 – 80.0°F
{
–0.0 – 80.0°F
}
10.5 – 9.5°F
Common
–17.8–26.6°C
–17.8–26.6°C
0.2 – 5.2°C
|
Chilled Water Temperature
Control Option
System Setpoint (chilled water
|
supply)
Chiller Setpoint (leaving
|
evaporator water)
Common Supply Deadband
ScrLineName
2
(default values: bold italic)
Min Chil Spt=
Mod Limit=
Sample Time=
40.0°F (4.4°C)
±6.0°F (±3.3°C)
30 Sec
FieldRangeVariable Name
~
10.0 – 80.0°F
–17.8–26.6°C
11.0 – 60.0°F
0.5 – 33.3°C
11 – 60 Sec
Minimum Chiller Setpoint
|
Common Supply Mod Limit
|
Common Supply Sample Time
1 – 60 Min
3
Max Change=
PA Time=
WITCH
S
Key Destination:
Notes:
1. The System Setpoint is adjustable only when the Chilled Water Temperature Reset Type variable (menu 17) is set to “None.”
Otherwise, the System Setpoint is automatically set by the CSC and is status only. The actual range of System Setpoint values is
defined by the Minimum System Setpoint and Maximum System Setpoint (menu 17).
2. Program CSC1S01
3. The Chiller Setpoint is not adjustable; it is automatically set by the CSC and is thus status only. When the Chilled Water
Temperature Control Option is set to “Unit,” the Chiller Setpoint is always equal to the System Setpoint.
4. The Minimum Chiller Setpoint can be set below 40.0°F (4.4°C) only when the Glycol Flag (menu 28) is set to “Yes.” It cannot be
set above the Minimum System Setpoint (menu 17).
>
only.
2.0°F (1.1°C)
0 Sec
Menu 17. Chilled Water Supply Temperature Reset
10.5 – 20.0°F
0.2 – 11.1°C
10 – 240 Sec
0 – 240 Min
Common Supply Max Change
|
Common Supply Project Ahead
Time
Figure 8. Menu 17, Chilled Water Supply Temperature Reset
ScrLineName
11
(default values: bold italic
Reset Type=
None
FieldRangeVariable Name
)
1
None
•
External
•
OAT
•
RChWT
•
Constant
•
Chilled Water Temperature
Reset Type
RChWT
2
3
21
2
Min Sys Spt=
Max Sys Spt=
MinSysSptAt
MaxSysSptAt
RChWT Spt=
Deadband=
±0.5°F (±0.2°C)
Mod Limit=
Sample Time=
44.0°F (6.6°C)
54.0°F (12.2°C)
90.0°F (32.2°C)
70.0°F (21.0°C)
54.0°F (12.2°C
±6.0°F (±3.3°C)
45 Sec
{
)
10.0 – 80.0°F
10.0 – 80.0°F
{
10.0 – 99.5°F
}
10.0 – 99.5°F
}
120.0 – 80.0°F
10.5 – 9.5°F
11.0 – 60.0°F
11 – 60 Sec
–17.8–26.6°C
–17.8–26.6°C
–17.8–37.4°C
–17.8–37.4°C
–6.7 – 26.6°C
0.2 – 5.2°C
0.5 – 33.3°C
Minimum System Setpoint
|
Maximum System Setpoint
|
Minimum System Setpoint At
|
Maximum System Setpoint At
|
Constant Return Setpoint
|
Constant Return Deadband
|
Constant Return Mod Limit
|
Constant Return Sample Time
1 – 60 Min
3
Max Change=
PA Time=
30 Sec
2.0°F (1.1°C)
10.5 – 10.0°F
0.2 – 11.1°C
10 – 240 Sec
0 – 240 Min
Constant Return Max Change
|
Constant Return Project Ahead
Time
31External Signal= 0.0 Vdc–0.0 – 5.0 VdcExternal Chilled Water Reset
Signal (conditioned)
2Return ChWT= 54.6°F (12.6°C)–
–45.0 –
•
255.0°F, N/A
–40.0 –125.0°C,
•
{
N/A
Chilled Water Return
Temperature
30OM127-1
ScrLineName
3OAT= 90.0°F (32.2°C)–
(default values: bold italic
FieldRangeVariable Name
)
–45.0 –255.0°F,
•
Outdoor Air Temperature
N/A
–40.0 –
•
125.0°C, N/A
WITCH
S
Key Destination:
Notes:
1. This setpoint can be set below 40.0°F (4.4°C) only when the Glycol Flag (menu 28) is set to “Yes.”
2. Program CSC1S01
3. The default value for this item is typical for the “OAT” reset method.
Menu 2. Temperatures
>
only.
{
Table 20. Menu 18, Cooling Tower Stages
ScrLineName
11
Tower Control=
Cntl Temp Src=
2
Number Of Stages=
Stage Diff=
3
StageUp Time=
StageDn Time=
21
31
WITCH
S
Key Destination:
Notes:
1. Program CSC1S01
2
3
1
2
3
2
3
1
2
3
Stg 1 Spt=
Stg 2 Spt=
Stg 3 Spt=
Stg 4 Spt=
Stg 5 Spt=
Stg 6 Spt=
Stg 7 Spt=
Stg 8 Spt=
Stg 9 Spt=
Stg 10 Spt=
Stg 11 Spt=
Stg 12 Spt=
>
only.
(default values: bold italic)
Yes
Ent
6
–3.0°F (–1.6°C)
2 Min
5 Min
74.0°F (23.3°C)
76.0°F (24.4°C)
78.0°F (25.5°C)
78.0°F (25.5°C)
78.0°F (25.5°C)
78.0°F (25.5°C)
78.0°F (25.5°C)
78.0°F (25.5°C)
78.0°F (25.5°C)
78.0°F (25.5°C)
78.0°F (25.5°C)
78.0°F (25.5°C)
Menu 19. Cooling Tower Output Sequence Order
FieldRangeVariable Name
1No
1Ent
1NA, 1 – 12Number Of Tower Stages
10.0 – 9.5°F
11 – 60 MinTower Stage-Up Delay Time
11 – 60 MinTower Stage-Down Delay Time
140.0 – 99.5°F
(same as Tower Stage 1 Spt.)Tower Stage 2 Setpoint
(same as Tower Stage 1 Spt.)Tower Stage 3 Setpoint
(same as Tower Stage 1 Spt.)Tower Stage 4 Setpoint
(same as Tower Stage 1 Spt.)Tower Stage 5 Setpoint
(same as Tower Stage 1 Spt.)Tower Stage 6 Setpoint
(same as Tower Stage 1 Spt.)Tower Stage 7 Setpoint
(same as Tower Stage 1 Spt.)Tower Stage 8 Setpoint
(same as Tower Stage 1 Spt.)Tower Stage 9 Setpoint
(same as Tower Stage 1 Spt.)Tower Stage 10 Setpoint
(same as Tower Stage 1 Spt.)Tower Stage 11 Setpoint
(same as Tower Stage 1 Spt.)Tower Stage 12 Setpoint
Yes
Lvg
{
0.0 – 5.2°C
{
4.4 – 37.4°C
Tower Control Flag
Control Temperature Source
Tower Stage Differential
Tower Stage 1 Setpoint
Table 21. Menu 19, Cooling Tower Output Sequence Order
ScrLineName
11
OM127-131
(default values: bold italic
Stage 1=
x 2 x x x x x x x xx xx xx
FieldRangeVariable Name
)
1x, 1Tower Stage 1 Bitset
2x, 2
3x, 3
4x, 4
5x, 5
6x, 6
7x, 7
8x, 8
9x, 9
10xx, 10
ScrLineName
(default values: bold italic
FieldRangeVariable Name
)
11xx, 11
12xx, 12
2
3
21
2
3
31
2
3
41
2
3
WITCH
S
Key Destination:
Stage 2=
1 x x x x x x x x xx xx xx
Stage 3=
1 2 x x x x x x x xx xx xx
Stage 4=
1 x 3 x x x x x x xx xx xx
Stage 5=
1 2 3 x x x x x x xx xx xx
Stage 6=
1 x 3 4 x x x x x xx xx xx
Stage 7=
x x x x x x x x x xx xx xx
Stage 8=
x x x x x x x x x xx xx xx
Stage 9=
x x x x x x x x x xx xx xx
Stage 10=
Stage 11=
Stage 12=
x x x x x x x x x xx xx xx
x x x x x x x x x xx xx xx
x x x x x x x x x xx xx xx
Menu 20. Cooling Tower Bypass Valve
same as Tower Stage 1 BitsetTower Stage 2 Bitset
same as Tower Stage 1 BitsetTower Stage 3 Bitset
same as Tower Stage 1 BitsetTower Stage 4 Bitset
same as Tower Stage 1 BitsetTower Stage 5 Bitset
same as Tower Stage 1 BitsetTower Stage 6 Bitset
same as Tower Stage 1 BitsetTower Stage 7 Bitset
same as Tower Stage 1 BitsetTower Stage 8 Bitset
same as Tower Stage 1 BitsetTower Stage 9 Bitset
same as Tower Stage 1 BitsetTower Stage 10 Bitset
same as Tower Stage 1 BitsetTower Stage 11 Bitset
same as Tower Stage 1 BitsetTower Stage 12 Bitset
Table 22. Menu 20, Cooling Tower Bypass Valve
ScrLineName
11
2
Valve Control=
Valve Spt=
Valve Db=
3
Min Position=
Max Position=
21
2
Valve Type=
Mod Limit=
Sample Time=
3
Max Change=
PA Time=
31
Min Start Pos=
Max Start Pos=
2
Min Pos At
Max Pos At
WITCH
S
Key Destination:
Notes:
1. Program CSC1S01
>
(default values: bold italic
None
70.0°F (21.0°C)
±2.0°F (±1.1°C)
20%
80%
NO To Tower
±7.5°F (±4.1°C)
15 Sec
4%
5 Sec
0%
100%
60.0°F (15.5°C)
90.0°F (32.2°C
Menu 6. Cooling Tower Status
only.
)
FieldRangeVariable Name
)
1None
Tower Valve Control Option
Valve Spt
Stage Spt
140.0 – 99.5°F
4.4 – 37.4°C
10.0 – 9.5°F
0.0 – 5.2°C
{
Tower Valve Setpoint
{
Tower Valve Deadband
10 – 100%Minimum Tower Valve Position
10 – 100%Maximum Tower Valve
Position
1NC To Tower
Tower Valve Type
NO To Tower
11.0 – 60.0°F
{
0.5 – 33.3°C
11 – 60 Sec
Tower Valve Mod Limit
Tower Valve Sample Time
1 – 15 Min
11 – 50%Tower Valve Max Change
10 – 240 SecTower Valve Project Ahead
Time
10 – 100%Minimum Tower Valve Start-
Up Position
10 – 100%Maximum Tower Valve Start-
Up Position
10.0 – 120.0°F
–17.8–48.8°C
10.0 – 120.0°F
–17.8–48.8°C
Minimum Tower Valve Start-
{
Up Position At
Maximum Tower Valve Start-
{
Up Position At
32OM127-1
Table 23. Menu 21. Load Flow Control
ScrLineName
11
2
3
(default values: bold italic)
Pump Control=
Pump Delay=
Mod Control=
Reseq=
None
30 Sec
None
N/A 00:00
FieldRangeVariable Name
1
None
•
One Pump
•
Auto Lead
•
#1 Lead
•
#2 Lead
•
Sequencing
•
Secondary Pump Control Option
11 – 60 SecPump Status Check Delay Time
1
1
None
•
Valve
•
VFD
•
N/A
•
Sun – Sat
•
Dly
•
Hol
•
{
Now
•
Modulation Control Option
Pump Resequence Day/Time
20 – 23
30 – 59
21
2
Setpoint=
Deadband=
10 psi (69 kPa)
±2 psi (±13 kPa)
Mod Limit=
Sample Time=
±10 psi (±69 kPa)
15 Sec
12 – 99 psi
|
13 – 683 kPa
10 – 9 psi
|
0 – 62 kPa
11 – 99 psi
|
6 – 683 kPa
11 – 60 SecLoop Differential Pressure Sample
Loop Differential Pressure
Setpoint
Loop Differential Pressure
Deadband
Loop Differential Pressure Mod
Limit
Time
3
Max Change=
5%
11 – 50%Loop Differential Pressure Max
Change
PA Time=
5 Sec
11 – 240 SecLoop Differential Pressure Project
Ahead Time
31
Pump Stages=
6
11 – 9Number Of Sequenced Pump
Stages
2
3
Diff=
+2 psi (+13 kPa)
StageUp Time=
StageDn Time=
Min Valve Pos=
2 Min
5 Min
20%
10 – 9 psi
|
0 – 62 kPa
11 – 60 MinPump Stage-Up Delay Time
11 – 60 MinPump Stage-Down Delay Time
10 – 100%Minimum Loop Bypass Valve
Pump Stage Differential
Position
Max Valve Pos=
90%
10 – 100%Maximum Loop Bypass Valve
Position
WITCH
S
Key Destination:
Notes:
1. The “Now” selection automatically changes to “N/A” after the resequence day/time function is executed.
2. Program CSC1S01
Menu 22. Secondary Pump Sequence Order
>
only.
Table 24. Menu 22. Secondary Pump Sequence Order
ScrLineName
11
OM127-133
(default values: bold italic)
Stage 1=
P1xxxxxxxxxx
FieldRangeVariable Name
1xx, P1Pump Stage 1 Bitset
2xx, P2
3xx, P3
4xx, P4
ScrLineName
2
3
21
2
3
31
2
3
WITCH
S
Key Destination:
Notes:
1. Program CSC1S01
(default values: bold italic)
Stage 2=
P1P2xxxxxxxx
Stage 3=
P1P2P3xxxxxx
Stage 4=
P1P2P3P4xxxx
Stage 5=
P1P2P3P4P5xx
Stage 6=
P1P2P3P4P5P6
Stage 7=
xxxxxxxxxxxx
Stage 8=
xxxxxxxxxxxx
Stage 9=
xxxxxxxxxxxx
Menu 7. Flow To Load
>
only.
Table 25. Menu 23. Time/Date
FieldRangeVariable Name
5xx, P5
6xx, P6
same as Pump Stage 1 BitsetPump Stage 2 Bitset
same as Pump Stage 1 BitsetPump Stage 3 Bitset
same as Pump Stage 1 BitsetPump Stage 4 Bitset
same as Pump Stage 1 BitsetPump Stage 5 Bitset
same as Pump Stage 1 BitsetPump Stage 6 Bitset
same as Pump Stage 1 BitsetPump Stage 7 Bitset
same as Pump Stage 1 BitsetPump Stage 8 Bitset
same as Pump Stage 1 BitsetPump Stage 9 Bitset
ScrLineName
11
2
3
WITCH
S
Key Destination:
(default values: bold italic)
Time=
hh:mm:ss
Day=
Day
Date=
Mth-dd-yy
None
Table 26. Menu 24. Schedule
ScrLineName
11
2
3
21
2
3
WITCH
S
Key Destination
(default values: bold italic)
Override=
NMP Schedule=
One Event=
0.00 Hrs
NA
N/A-01 18:00
Hrs
Sun
00:00–00:00
Mon
00:00–00:00
Tue
00:00–00:00
Wed
00:00–00:00
Thu
00:00–00:00
Fri
00:00–00:00
Sat
00:00–00:00
Hol
00:00–00:00
: Menu 10. System Control
for
2.00
FieldRangeVariable Name
10 – 23Current Time
20 – 59
30 – 59
1Sun – SatCurrent Day
1Jan – DecCurrent Date
21 – 31
300 – 99
FieldRangeVariable Name
1
{
0.00 – 60.00 HrsOverride Time
1NA, 1 – 32NMP Schedule Number
1N/A, Jan – DecOne Event Schedule
21 – 31
30 – 23
40 – 59
5
{
0.00 – 60.00 Hrs
10 – 23Sunday Schedule
20 – 59
30 – 23
40 – 59
(same as Sunday Schedule)Monday Schedule
(same as Sunday Schedule)Tuesday Schedule
(same as Sunday Schedule)Wednesday Schedule
(same as Sunday Schedule)Thursday Schedule
(same as Sunday Schedule)Friday Schedule
(same as Sunday Schedule)Saturday Schedule
(same as Sunday Schedule)Holiday Schedule
34OM127-1
Notes:
1. The resolution is 0.25 hour (15 minutes).
Table 27. Menu 25. Holiday Date
ScrLineName
11
#1 Date=
Duration=
2
#2 Date=
Duration=
3
#3 Date=
Duration=
21
#4 Date=
Duration=
2
#5 Date=
Duration=
3
#6 Date=
Duration=
31
#7 Date=
Duration=
2
#8 Date=
Duration=
3
#9 Date=
Duration=
41
#10 Date=
Duration=
2
#11 Date=
Duration=
3
#12 Date=
Duration=
WITCH
S
Key Destination
(default values: bold italic
Dec 25
1 Days
N/A 01
1 Days
N/A 01
1 Days
N/A 01
1 Days
N/A 01
1 Days
N/A 01
1 Days
N/A 01
1 Days
N/A 01
1 Days
N/A 01
1 Days
N/A 01
1 Days
N/A 01
1 Days
N/A 01
1 Days
: None
FieldRangeVariable Name
)
1N/A, Jan – DecHoliday Date #1
21 – 31
11 – 31 DaysHoliday Date #1 Duration
1N/A, Jan – DecHoliday Date #2
21 – 31
11 – 31 DaysHoliday Date #2 Duration
1N/A, Jan – DecHoliday Date #3
21 – 31
11 – 31 DaysHoliday Date #3 Duration
1N/A, Jan – DecHoliday Date #4
21 – 31
11 – 31 DaysHoliday Date #4 Duration
1N/A, Jan – DecHoliday Date #5
21 – 31
11 – 31 DaysHoliday Date #5 Duration
1N/A, Jan – DecHoliday Date #6
21 – 31
11 – 31 DaysHoliday Date #6 Duration
1N/A, Jan – DecHoliday Date #7
21 – 31
11 – 31 DaysHoliday Date #7 Duration
1N/A, Jan – DecHoliday Date #8
21 – 31
11 – 31 DaysHoliday Date #8 Duration
1N/A, Jan – DecHoliday Date #9
21 – 31
11 – 31 DaysHoliday Date #9 Duration
1N/A, Jan – DecHoliday Date #10
21 – 31
11 – 31 DaysHoliday Date #10 Duration
1N/A, Jan – DecHoliday Date #11
21 – 31
11 – 31 DaysHoliday Date #11 Duration
1N/A, Jan – DecHoliday Date #12
21 – 31
11 – 31 DaysHoliday Date #12 Duration
Table 28. Menu 26. Optimal Start
ScrLineName
11
OM127-135
(default values: bold italic
Optimal Start=
No
FieldRangeVariable Name
)
1No
Optimal Start Flag
Yes
ScrLineName
(default values: bold italic
Auto Update=
No
FieldRangeVariable Name
)
1No
Auto Update Flag
Yes
2
Recirc At 04 :00
100 – 23Optimal Start Begin Recirculate
Time
Recirc Time=
10 Min
10 – 59 MinOptimal Start Recirculation
Period
WITCH
S
Key Destination
3
Calculated Start Time=
06:45
: None
–00:00 – 23:59Today’s Optimal Start Time
Table 29. Menu 27. Table of Optimal Start Time Increments (in Minutes)
Return Chilled Water Temperature
ScrLine
1250°F (10°C)5 10152025
360°F (15°C)1015202530
2270°F (21°C)1520253035
380°F (26°C)2025303540
3290°F (32°C)2530354045
3100°F (38°C)3035404550
WITCH
S
Key Destination:
Outdoor Air
Temperature50°F (10°C)60°F (15°C)70°F (21°C)80°F (26°C)90°F (32°C)
None
Note:
Each element of the table is an adjustable field with a range of 0 – 240 minutes. If the Auto
Update Flag (menu 26) is set to “Yes,” the CSC automatically updates these fields (if necessary) as it
adapts to the cooling system’s unique characteristics.
Table 30. Menu 28. Service
ScrLineName
11
2
3
21Decoupler Flow Calibration:(Screen name)
2
3
31Differential Pressure Calibration:(Screen name)
2
3
41Analog Output Zero Setup:(Screen name)
2Tower Bypass Valve=
3Load Bypass Valve or VFD=
(default values: bold italic
{
Level=
1
{
Port A Baud=
Total Slaves=
Glycol=
IDENT=
Flow At 4mA/1Vdc/2Vdc
9600
0
No
CSC1E01F
= 0 gpm
(0.0 L/s)
Flow At 20mA/5Vdc/10Vdc=
1000
gpm (63.0 L/s)
Pressure At 4mA/1Vdc/2Vdc=
(0 kPa)
Pressure At 20mA/5Vdc/10Vdc=
psi (207 kPa)
4mA/1Vdc/2Vdc
4mA/1Vdc/2Vdc
FieldRangeVariable Name
)
11
Controller Level
2
1
•
•
•
1200
2400
9600
Port A Baud Rate
10 – 64Total Slaves
1No
Glycol Flag
Yes
––Program Code (“Ident”)
10 – 5120 gpm
|
10 – 5120 gpm
|
10 – 150 psi
0 psi
|
10 – 150 psi
30
|
10mA/0Vdc
0.0 – 322.5 L/s
0.0 – 322.5 L/s
0 – 1035 kPa
0 – 1035 kPa
Decoupler Flow Meter Low Cal Rate
Decoupler Flow Meter High Cal
Rate
Loop DP Sensor Low Cal Pressure
Loop DP Sensor High Cal Pressure
Tower Bypass Valve AO Zero
4mA/1Vdc/2Vdc
10mA/0Vdc
4mA/1Vdc/2Vdc
Load Bypass Valve AO Zero or
VFD AO Zero
36OM127-1
ScrLineName
51
(default values: bold italic
Ret ChW Sensor=
Decouple Sensor=
No
No
FieldRangeVariable Name
)
1No
Yes
1No
Return Chilled Water Sensor Present
Flag
Decoupler Sensor Present Flag
Yes
2
Ent CndW Sensor=
Lvg CndW Sensor=
3
OAT Sensor=
>
only.
None
WITCH
S
Key Destination:
Notes:
1. After changing the value of this variable, you must reset the controller to cause the change to go into effect. You can reset the
controller by cycling power to the panel.
2. Program CSC1S01
No
No
None
1No
Yes
1No
Yes
1
None
•
Local
•
Remote
•
Entering Condenser Water Sensor
Present Flag
Leaving Condenser Water Sensor
Present Flag
Outdoor Air Temperature Source
Table 31. Menu 29. Chiller Setup
ScrLineName
11
21
31
41
2
3
1
2
3
2
3
1
2
3
2
3
1
2
3
2
#1=
NA
Address=
Flow Rate=
#2=
NA
Address=
Flow Rate=
#3=
NA
Address=
Flow Rate=
#4=
N/A
Address=
Flow Rate=
#5=
N/A
Address=
Flow Rate=
#6=
N/A
Address=
Flow Rate=
#7=
N/A
Address=
(default values: bold italic
NA
1200 gpm (75.6 L/s)
NA
1200 gpm (75.6 L/s)
NA
1200 gpm (75.6 L/s)
NA .00
1200 gpm (75.6 L/s
)
NA .00
1200 gpm (75.6 L/s)
NA .00
1200 gpm (75.6 L/s)
NA .00
FieldRangeVariable Name
)
1
N/A
•
Centrif-100
•
Centrif-200
•
Recip- Standard
•
Screw
•
Recip-European
•
HallScrew
•
AGU
•
Chiller #1 Type
1NA, 01 – 40 (hex)Chiller #1 Address
10 – 5120 gpm
{
0 – 322.5 L/s
Chiller #1 Flow Rate
(same as Chiller #1 Type)Chiller #2 Type
1NA, 01 – 40 (hex)Chiller #2 Address
10 – 5120 gpm
{
0 – 322.5 L/s
Chiller #2 Flow Rate
(same as Chiller #1 Type)Chiller #3 Type
1NA, 01 – 40 (hex)Chiller #3 Address
10 – 5120 gpm
{
0 – 322.5 L/s
Chiller #3 Flow Rate
(same as Chiller #1 Type)Chiller #4 Type
1NA, 01 – 40 (hex)Chiller #4 Address
10 – 5120 gpm
{
0 – 322.5 L/s
Chiller #4 Flow Rate
(same as Chiller #1 Type)Chiller #5 Type
1NA, 01 – 40 (hex)Chiller #5 Address
10 – 5120 gpm
{
0 – 322.5 L/s
Chiller #5 Flow Rate
(same as Chiller #1 Type)Chiller #6 Type
1NA, 01 – 40 (hex)Chiller #6 Address
10 – 5120 gpm
{
0 – 322.5 L/s
Chiller #6 Flow Rate
(same as Chiller #1 Type)Chiller #7 Type
1NA, 01 – 40 (hex)Chiller #7 Address
OM127-137
ScrLineName
3
Flow Rate=
1
#8=
N/A
2
Address=
3
Flow Rate=
51
61
WITCH
S
Key Destination:
Notes:
1. Program CSC1S01
2
3
1
2
3
2
3
1
2
3
#9=
N/A
Address=
Flow Rate=
#10=
Address=
Flow Rate=
#11=
Address=
Flow Rate=
#12=
Address=
Flow Rate=
>
(default values: bold italic
1200 gpm (75.6 L/s)
NA .00
1200 gpm (75.6 L/s)
NA .00
1200 gpm (75.6 L/s)
N/A
NA .00
1200 gpm (75.6 L/s)
N/A
NA .00
1200 gpm (75.6 L/s)
N/A
NA .00
1200 gpm (75.6 L/s)
None
only.
FieldRangeVariable Name
)
10 – 5120 gpm
{
0 – 322.5 L/s
Chiller #7 Flow Rate
(same as Chiller #1 Type)Chiller #8 Type
1NA, 01 – 40 (hex)Chiller #8 Address
10 – 5120 gpm
{
0 – 322.5 L/s
Chiller #8 Flow Rate
(same as Chiller #1 Type)Chiller #9 Type
1NA, 01 – 40 (hex)Chiller #9 Address
10 – 5120 gpm
{
0 – 322.5 L/s
Chiller #9 Flow Rate
(same as Chiller #1 Type)Chiller #10 Type
1NA, 01 – 40 (hex)Chiller #10 Address
10 – 5120 gpm
{
0 – 322.5 L/s
Chiller #10 Flow Rate
(same as Chiller #1 Type)Chiller #11 Type
1NA, 01 – 40 (hex)Chiller #11 Address
10 – 5120 gpm
{
0 – 322.5 L/s
Chiller #11 Flow Rate
(same as Chiller #1 Type)Chiller #12 Type
1NA, 01 – 40 (hex)Chiller #12 Address
10 – 5120 gpm
{
0 – 322.5 L/s
Chiller #12 Flow Rate
Table 32. Menu 30. Service Testing
ScrLineName
11
2
3
1
2
3
21
2
3
1
2
3
(default values: bold italic
DO 0=
Off
DO 1=
Off
DO 2=
Off
DO 3=
Off
DO 4=
Off
DO 5=
Off
DO 6=
Off
DO 7=
Off
DO 8=
Off
DO 9=
Off
DO 10=
Off
DO 11=
Off
FieldRangeVariable Name
)
1Off
On
Digital Output 0 Service Test
State
same as DO 0 Svc. Test StateDigital Output 1 Service Test
State
same as DO 0 Svc. Test StateDigital Output 2 Service Test
State
same as DO 0 Svc. Test StateDigital Output 3 Service Test
State
same as DO 0 Svc. Test StateDigital Output 4 Service Test
State
same as DO 0 Svc. Test StateDigital Output 5 Service Test
State
same as DO 0 Svc. Test StateDigital Output 6 Service Test
State
same as DO 0 Svc. Test StateDigital Output 7 Service Test
State
same as DO 0 Svc. Test StateDigital Output 8 Service Test
State
same as DO 0 Svc. Test StateDigital Output 9 Service Test
State
same as DO 0 Svc. Test StateDigital Output 10 Service Test
State
same as DO 0 Svc. Test StateDigital Output 11 Service Test
State
38OM127-1
ScrLineName
31
41
51
WITCH
S
Key Destination
DO 12=
2
DO 13=
3
DO 14=
1
DO 15=
2
DO 16=
3
DO 17=
DO 18=
2
DO 19=
3
DO 20=
1
DO 21=
2
DO 22=
3
DO 23=
AO 0=
2
AO 1=
3
AO 2=
1
AO 3=
(default values: bold italic
Off
Off
Off
Off
Off
Off
Off
Off
Off
Off
Off
Off
0%
0%
0%
0%
: None
FieldRangeVariable Name
)
same as DO 0 Svc. Test StateDigital Output 12 Service Test
same as DO 0 Svc. Test StateDigital Output 13 Service Test
same as DO 0 Svc. Test StateDigital Output 14 Service Test
same as DO 0 Svc. Test StateDigital Output 15 Service Test
same as DO 0 Svc. Test StateDigital Output 16 Service Test
same as DO 0 Svc. Test StateDigital Output 17 Service Test
same as DO 0 Svc. Test StateDigital Output 18 Service Test
same as DO 0 Svc. Test StateDigital Output 19 Service Test
same as DO 0 Svc. Test StateDigital Output 20 Service Test
same as DO 0 Svc. Test StateDigital Output 21 Service Test
same as DO 0 Svc. Test StateDigital Output 22 Service Test
same as DO 0 Svc. Test StateDigital Output 23 Service Test
10 – 100%Analog Output 0 Service Test
10 – 100%Analog Output 1 Service Test
10 – 100%Analog Output 2 Service Test
10 – 100%Analog Output 3 Service Test
State
State
State
State
State
State
State
State
State
State
State
State
Setpoint
Setpoint
Setpoint
Setpoint
Note:
To use the Service Testing menu, set the CSC Control Mode variable (menu 10) to “Service
Testing.”
Alarm Menus
The Alarm category includes menus 31 through 35.
Current Alarms
Menu 31, “Current Alarms,” tells you whether a CSC alarm or chiller alarm exists in the network. The
first item identifies the current CSC alarm and the time and date it occurred. Each of the remaining
items identifies the current chiller alarm type (Fault, Problem, or Warning) and the time and date the
alarm occurred in each chiller. If there is no current alarm, the “None” message is displayed. When
the current CSC alarm clears, it moves to the CSC Alarm Buffer menu. For more information, see the
“Alarm Monitoring” section of this manual.
CSC Alarm Buffer
Menu 32, “CSC Alarm Buffer,” tells you what the previous CSC alarms were and when they
occurred. When the current CSC alarm clears, it moves to this menu. The buffer holds nine alarms.
For more information, see the “Alarm Monitoring” section of this manual.
OM127-139
Alarm Horn Setup
Menu 33, “Alarm Horn Setup,” allows you to specify whether or not a certain type of CSC or chiller
alarm causes the CSC’s Alarm Horn to sound. For more information, see the “Alarm Monitoring”
section of this manual.
Alarm Output Setup
Menu 34, “Alarm Out Setup,” allows you to specify the states of the CSC’s Alarm Output for the four
types of CSC and chiller alarms. The options for each alarm type are open, closed, fast pulse, and
slow pulse. For more information, see the “Alarm Monitoring” section of this manual.
Message Board
Menu 35, “Message Board,” is a special menu that you can use to annotate any information that you
or other operators may need. For example, you may want to post an after-hours phone number that an
operator could call in case of trouble with the chiller system. To enter information onto the Message
Board, you must have a PC equipped with MicroTech Monitor program.
Table 33. Menu 31. Current Alarms
ScrLineName
(typical values: italic
11CSC= Sec Pump 1 Fail
At 17:55Jul-01
2Chil #1= Fault
At 14:21Jul-02
3Chil #2= None
At 00:00N/A-00
21Chil #3= None
At 00:00N/A-00
2Chil #4= None
At 00:00N/A-00
3Chil #5= None
At 00:00N/A-00
31Chil #6= None
At 00:00N/A-00
2Chil #7= None
At 00:00N/A-00
3Chil #8= None
At 00:00N/A-00
WITCH
S
Key Destination
: None
)
FieldRangeVariable Name
–
Lvg CndW T Fail
•
Ent CndW T Fail
•
No Sec ChW Flow
•
{
NoCommChil#
•
Decouple F Fail
•
{
Sec Pump
•
Outside T Fail
•
Decouple T Fail
•
Ret ChW T Fail
•
Sup ChW T Fail
•
ChW Press Fail
•
Clg Tower Fail
•
LvgCndW T Warn
•
EntCndW T Warn
•
Chiller Offline
•
None
•
Current CSC Alarm
>
>
Fail
–any time and date
–Fault
Current Chiller #1 Alarm Type
Problem
Warning
None
–any time and date
same as Chiller #1 Alarm Type Current Chiller #2 Alarm Type
same as Chiller #1 Alarm Type Current Chiller #3 Alarm Type
same as Chiller #1 Alarm Type Current Chiller #4 Alarm Type
same as Chiller #1 Alarm Type Current Chiller #5 Alarm Type
same as Chiller #1 Alarm Type Current Chiller #6 Alarm Type
same as Chiller #1 Alarm Type Current Chiller #7 Alarm Type
same as Chiller #1 Alarm Type Current Chiller #8 Alarm Type
40OM127-1
Notes:
1. The wildcard character (
) indicates the number of the unit with the alarm.
>
Table 34. Menu 32. CSC Alarm Buffer
ScrLineName
(typical values: bold italic
111. Ret ChW T Fail
At 08:09 Jun-30
22. None
At 00:00N/A-00
33. None
At 00:00N/A-00
214. None
At 00:00N/A-00
25. None
At 00:00N/A-00
36. None
At 00:00N/A-00
317. None
At 00:00N/A-00
28. None
At 00:00N/A-00
39. None
At 00:00N/A-00
4110. None
At 00:00N/A-00
211. None
At 00:00N/A-00
312. None
At 00:00N/A-00
WITCH
S
Key Destination
: None
FieldRangeVariable Name
)
same as Current CSC AlarmBuffer Alarm #1 (most recent)
same as Current CSC AlarmBuffer Alarm #2
same as Current CSC AlarmBuffer Alarm #3
same as Current CSC AlarmBuffer Alarm #4
same as Current CSC AlarmBuffer Alarm #5
same as Current CSC AlarmBuffer Alarm #6
same as Current CSC AlarmBuffer Alarm #7
same as Current CSC AlarmBuffer Alarm #8
same as Current CSC AlarmBuffer Alarm #9
same as Current CSC AlarmBuffer Alarm #10
same as Current CSC AlarmBuffer Alarm #11
same as Current CSC AlarmBuffer Alarm #12
Table 35. Menu 33. Alarm Horn Setup
ScrLineName
11
2
WITCH
S
Key Destination
(default values: bold italic
Comm Loss=
Faults=
Problems=
Warnings=
No Horn
Horn
Horn
No Horn
: None
Table 36. Menu 34. Alarm Output Setup
ScrLineName
11
2
(default values: bold italic
Normal=
Comm Loss=
Open
Fast
FieldRangeVariable Name
)
1
1
1
1
FieldRangeVariable Name
)
1
1
No Horn
•
Horn
•
No Horn
•
Horn
•
No Horn
•
Horn
•
No Horn
•
Horn
•
Open
•
Closed
•
Open
•
Closed
•
Slow
•
Fast
•
Horn On Comm Loss Flag
Horn On Fault Flag
Horn On Problem Flag
Horn On Warning Flag
Alarm Output Normal State
Alarm Output Comm Loss State
OM127-141
ScrLineName
3
WITCH
S
Key Destination
(default values: bold italic
Faults=
Fast
Problems=
Warnings=
Slow
Slow
: None
FieldRangeVariable Name
)
1
1
1
•
•
•
•
•
•
•
•
•
•
•
•
Open
Closed
Slow
Fast
Open
Closed
Slow
Fast
Open
Closed
low
Fast
Alarm Output Fault State
Alarm Output Problem State
Alarm Output Warning State
CSC and Chiller Controller Initial Setup
This section explains the setup variables in the CSC and chiller controllers that must be set to
integrate the CSC, its associated chillers, and a PC (if used) into a working network. It also explains
the setup variables that are related to the CSC’s analog inputs and outputs. Once set in accordance
with the job requirements and characteristics, most of these variables should never need to be
changed. Most of this CSC and chiller controller setup is necessary to commission the network. For
more information on network commissioning, see Bulletin MicroTech Chiller System Controller.
After a working network has been established, further setup is likely necessary to adapt the CSC and
chiller controllers to your particular application’s requirements. For complete information on how to
do this, see the “Operator’s Guide” and “Description of Operation” portions of this manual. Until this
application setup is done, the chiller system should remain disabled. See “Control Mode” in “Setting
Up the CSC” below for information on how to disable the chiller system.
Dual-Compressor Centrifugal Chillers
If the CSC is controlling dual-compressor centrifugal chillers (Centrif-100 or Centrif-200), load
balancing and start-up unloading control must be set up before the system is started. For more
information, see the “Load Limiting Control” section of this manual.
Setting Up the CSC
Variable NameKeypad
CSC Control Mode10-1
Number Of Chillers11-4
Controller Level28-1
Port A Baud Rate28-1
Total Slaves28-1
Decoupler Flow Meter Low Cal Rate28-2
Decoupler Flow Meter High Cal Rate28-2
Loop DP Sensor Low Cal Pressure28-3
Loop DP Sensor High Cal Pressure28-3
Tower Bypass Valve AO Zero28-4
Load Bypass Valve AO Zero or VFD AO Zero28-4
Tower Valve Type20-2
Outdoor Air Temperature Source28-5
Return Chilled Water Sensor Present Flag28-5
(Menu-Scr.)
42OM127-1
Variable NameKeypad
Decoupler Sensor Present Flag28-5
Entering Condenser Water Sensor Present Flag28-5
Leaving Condenser Water Sensor Present Flag28-5
>
Chiller #
Chiller #
Note:
Type29-1 to -4
>
Address29-1 to -4
The wildcard character (
) could be 1 through 12.
>
(Menu-Scr.)
Control Mode
Until the CSC and chiller controllers are set up properly for the chiller system applications, the chiller
system should remain disabled. You can disable the chiller system by setting the CSC Control Mode
variable to “Manual Off.” This prevents chillers from starting when communications between the
CSC and the chillers begin.
Number Of Chillers
The Number Of Chillers variable tells the CSC how many chillers are connected to it. Starting at
Chiller #1 and proceeding consecutively, the CSC attempts to communicate to the number of chillers
specified. For example, if the Number Of Chillers variable is set to “3,” the CSC attempts to
communicate with Chiller #1, Chiller #2, and Chiller #3.
Controller Level
The Controller Level variable defines the CSC’s level in the network. For the typical CSC network in
which there is one CSC and no Network Master Panel, the CSC is the level-1 controller, and chillers
are level-2 controllers. If a Network Master Panel is included in a network with one or more CSCs,
the CSC(s) and chillers are level-2 controllers. If there are two or more CSCs in the same network but
no Network Master Panel, one of the CSCs is the level-1 controller, and the other CSC(s) and chillers
are level-2 controllers. For more information, see “Network Communications” in the “Field Wiring”
section of Bulletin No. IM 618.
To change the controller level
1. Set the hex switches as required. A level-2 controller’s hex switch setting cannot be 00. A level-1
controller’s hex switch setting must be 00.
2. At the keypad/display, set the Controller Level variable to “1” or “2” as required. When the
ENTER
key is pressed, the CSC automatically corrects its checksums. The display shows the new
controller level, but the level does not actually change until the controller is reset.
3. Reset the controller by doing one of the following:
Cycle power to the panel with the circuit breaker (CB1).
Execute a soft reset at a PC equipped with the Monitor program.
Port A Baud Rate
A direct or remotely connected PC equipped with the Monitor program can be connected to the CSC
at port A on the Microprocessor Control Board. You can set the CSC’s port A data transmission
speed with the Port A Baud Rate variable (default is 9600 baud). Typically, a PC communicates with
the CSC at 9600 baud regardless of whether it is connected directly or remotely (via modem). For
more information, see “PC Connection” in the “Field Wiring” section of Bulletin No. IM 618.
To change the port A baud rate
1. Set the Port A Baud Rate variable as required. After changing it, the display show the new baud
rate, but the baud rate does not actually change until the controller is reset.
2. Reset the controller by doing one of the following:
Cycle power to the panel with the circuit breaker (CB1).
Execute a soft reset at a PC equipped with the Monitor program. (If you use this method and
your PC is connected to the CSC, you will lose communications.)
OM127-143
Total Slaves
The Total Slaves variable tells the level-1 CSC how many level-2 controllers (slaves) it must poll.
(When a level-1 controller polls one of its level-2 slaves, it actively “asks” the slave if it has any
requests for information from other controllers.) The Total Slaves variable defines this number.
The Total Slaves variable should be kept as low as possible to reduce unnecessary network
communications and thus improve network performance. If a level-2 controller must be polled, set the
Total Slaves variable just high enough to include that controller. For example, assume there are nine
level-2 controllers connected to a level-1 CSC, and the controllers at addresses 02 and 06 need to be
polled. In this case, the Total Slaves variable should be set to “6.”
The typical chiller system network includes one CSC (level 1) and up to 12 chillers (level 2). A PC
might be directly or remotely connected to the CSC, but not to any of the chillers. In this situation,
none of the chillers must be polled and thus the Total Slaves variable should be set to “0.”
Following are two examples of situations in which the Total Slaves variable should be changed:
1. If a PC is directly or remotely connected to one of the level-2 slaves, that slave must be polled so
the PC can access controllers throughout the network. Set the level-1 CSC’s Total Slaves
variable high enough to include that slave.
2. If one or more level-2 CSCs are in the same network with a level-1 CSC, the level-2 CSCs must
be polled so they can monitor and control their chillers. Set the level-1 CSC’s Total Slaves
variable high enough to include all level-2 CSCs. A level-2 CSC’s Total Slaves variable should
always be set to “0.”
Decoupler Flow Meter Calibration
If the chiller system has a flow meter installed in the decoupler line, the flow rates that correspond to
the low and high transducer signals must be entered into the CSC. The flow rate in the decoupler line
is always measured in the supply-to-return direction.
Use the Decoupler Flow Meter Low Cal Rate variable to enter the flow rate when the transducer
signal is one of the following:
• 4 mA for 4–20 mA transducers
• 1 Vdc for 1–5 Vdc transducers
• 2 Vdc for 2–10 Vdc transducers
Use the Decoupler Flow Meter High Cal Rate variable to enter the flow rate when the transducer
signal is one of the following:
• 20 mA for 4–20 mA transducers
• 5 Vdc for 1–5 Vdc transducers
• 10 Vdc for 2–10 Vdc transducers
Note:
In addition to these calibration constants, dip switches on the Input Conditioning Module must
be set as required for the type of transducer being used. See Bulletin No. IM 605, MicroTech InputConditioning Module, for more information.
Loop Differential Pressure Sensor Calibration
If the chiller system has a differential pressure sensor installed across the supply and return lines, the
pressures that correspond to the low and high transducer signals must be entered into the CSC.
Use the Loop DP Sensor Low Cal Pressure variable to enter the differential pressure when the
transducer signal is one of the following:
• 4 mA for 4–20 mA transducers
• 1 Vdc for 1–5 Vdc transducers
• 2 Vdc for 2–10 Vdc transducers
Use the Loop DP Sensor High Cal Pressure variable to enter the flow rate when the transducer signal
is one of the following:
44OM127-1
• 20 mA for 4–20 mA transducers
• 5 Vdc for 1–5 Vdc transducers
• 10 Vdc for 2–10 Vdc transducers
Note:
In addition to these calibration constants, dip switches on the Input Conditioning Module must
be set as required for the type of transducer being used. See Bulletin No. IM 605, MicroTech InputConditioning Module, for more information.
Analog Output Zero Setup
If the chiller system has a cooling tower bypass valve, a cooling load bypass valve, or a secondary
pump with a variable frequency drive (VFD), the low value of the device’s input signal range must be
entered into the CSC. Use the Tower Bypass Valve AO Zero, Load Bypass Valve AO Zero, or VFD
AO Zero variables to do this. (Since a cooling load bypass valve and secondary pump VFDs are
mutually exclusive, these last two are really one variable with two names.)
Set the variable to “0mA/0Vdc” for the following actuator or VFD input ranges:
• 0–20 mA
• 0–5 Vdc
• 0–10 Vdc
Set the variable to “4mA/1Vdc/2Vdc” for the following actuator or VFD input ranges:
• 4–20 mA
• 1–5 Vdc
• 2–10 Vdc
Note:
In addition to these range zeros, jumper plugs on the Analog Output Expansion Module must
be set as required for the type of actuator or VFD being used. See Bulletin No. IM 607, MicroTechAnalog Output Expansion Module, for more information.
Valve Types
If you are using a cooling load bypass valve, it must be a normally closed (NC) valve. (A closed valve
prevents flow from bypassing the cooling loads.) When the CSC opens the valve it increases the
voltage or current signal. When there is no control signal, the valve should be closed.
If you are using a cooling tower bypass valve, it can be either type: normally open (NO) to the tower
or normally closed (NC). You can specify which type it is with the Tower Valve Type variable.
NC Tower Valve:
If the valve type is NC, the CSC increases the voltage or current signal to the
valve as it opens the valve to the tower. When there is no control signal, the valve should be closed to
the tower (full bypass).
NO Tower Valve:
If the valve type is NO, the CSC decreases the voltage or current signal to the
valve as it opens the valve. When there is no control signal, the valve should be open to the tower.
Outdoor Air Temperature Source
The CSC can get the outdoor air temperature from one of three sources: (1) a CSC input, (2) a
MicroTech Network Master Panel (NMP), or (3) a building automation system (BAS) communicating
via Open Protocol. The Outdoor Air Temperature Source variable tells the CSC where to find the
temperature.
If the outdoor air temperature sensor is connected to the CSC, set the Outdoor Air Temperature
Source variable to “Local.” If it is connected to an NMP or a BAS, set the variable to “Remote.” If
the outdoor air temperature is not available, set the variable to “None” to prevent nuisance sensor
failure alarms from occurring.
Temperature Sensor Flags
In addition to the outdoor air sensor, the following temperature sensors are optional:
OM127-145
• Return chilled water
• Decoupler water
• Entering condenser water
• Leaving condenser water
The CSC must know whether these sensors are connected so that it can generate or suppress sensor
failure alarms. If one of the above sensors is connected, set its associated sensor flag to “Yes.”
Otherwise, set the flag to “No.” For example, if there is a return chilled water temperature sensor
connected to AI 1, set the Return Chilled Water Sensor Present Flag to “Yes.”
Chiller Type
The Chiller #
>
Type variables tell the CSC what types of chillers are connected to it. (The wildcard
character in the variable name could be a number from 1 to 8.) The CSC can communicate with and
control seven types of MicroTech-equipped McQuay chillers:
• Centrif-200 (new style controller)
• Centrif-100 (old style controller)
• Recip-Standard
• Screw
• Recip-European
• HallScrew Screw
• AGU
Unused Chiller #
>
Type variables should be set to “N/A.”
Note:
The Chiller #
>
Type variables must be set consecutively, starting with Chiller #1. For example,
if there are three chillers associated with a CSC, the following variables must be set: Chiller #1 Type,
Chiller #2 Type, and Chiller #3 Type.
Chiller Address
The Chiller #
>
Address variables tell the CSC what its associated chillers’ level-2 network addresses
are. (The wildcard character in the variable name is a number from 1 to 12.) The first two digits of
these variables must match the hex switch setting at the corresponding chiller. For example, if the hex
switch setting at Chiller #2 is 04, the Chiller #2 Address variable must be set to “04.00.”
Setting Up Centrif-200 and HallScrew Chiller Controllers
Following are guidelines for setting up Centrif-200 and HallScrew chiller controllers. For information
on the series-200 centrifugal chiller controller, refer to Bulletin Nos. IM 616 and OM 125.
Unit Setup Variables
Three unit setup variables must be set in all chiller controllers associated with a CSC. These
variables, which are summarized in Table 5, must be set to the values shown in italic. This is trueregardless of whether the chiller has a single compressor or dual compressors. You can find them at
the chiller controller’s keypad/display under menu 26, “Unit Setup.”
Table 37. Unit Setup Variables
Keypad/Display ID
Chiller Controller VariableMenuItem
Port Configuration26Config= L2-TTY-Slave
Chiller Type26Chiller Only
Master/Slave Type26Master/Slave= Slave
46OM127-1
Control Mode
Each chiller’s Control Mode variable must be set to “Auto:Network” to allow the CSC to enable it.
You can find this variable at the chiller controller’s keypad/display under menu 11, “Control Mode.”
The item name is “Mode=.”
Note:
During the network commissioning process, it is recommended that the chillers be shut down
by setting their control modes to “Manual Off.” If the network is being commissioned before a
particular chiller has been commissioned, that chiller’s control mode must be set to “Manual Off” to
prevent it from starting. For more on network commissioning, see Bulletin No. IM 618.
Setting Up Centrif-100 Chiller Controllers
Following are guidelines for setting up Centrif-100 chiller controllers. For information on the series100 centrifugal chiller controller, refer to Bulletin Nos. IM 403 and APM 950.
Note:
No series-100 centrifugal chillers were shipped with software that is compatible with the CSC.
Therefore, all series-100 controllers associated with a CSC must have new software downloaded to
them in the field. Be sure that this has been done before proceeding.
Start Mode
Each chiller’s Start Mode variable must be set to “Remote” to allow the CSC to enable it. You can get
to the Start Mode variable by pressing the chiller controller’s
SET-UP OPTIONS
key five times.
Note:
When the Start Mode is set to “Remote,” the chiller controller checks its remote start/stop
input. This input must be closed before the CSC can enable the chiller. If the Start Mode had been set
to “Local” and a remote start/stop switch is not being used, a jumper must be installed across the
remote start/stop input (field terminals 9 and 64 in the control box).
Setting Up Recip-Standard, Screw, Recip-European, and AGU Chiller
Controllers
Following are guidelines for setting up reciprocating, screw, and AGU (global) chiller controllers. For
information on the chiller controllers, refer to the appropriate MicroTech unit controller installation
or operation manual (see Tables 1 and 2).
Control Mode
Before the CSC controller can enable a chiller, its control mode must be set for automatic operation
(all circuits or at least one circuit). The normal setting is “Automatic.” You can set its control mode
with the Control Mode variable. At the chiller controller’s keypad/display, this is the first item under
the “Control Mode” menu (menu 13 on 2-circuit chillers; menu 16 on 3-circuit chillers).
Note:
During the network commissioning process, it is recommended that the chillers be shut down
by setting their control modes to “Manual Unit Off.” If the network is being commissioned before a
particular chiller has been commissioned, that chiller’s control mode must be set to “Manual Unit
Off” to prevent it from starting. For more on network commissioning, see Bulletin No. IM 618.
OM127-147
Operator’s Guide
The following “Operator’s Guide” sections provide information on the day-to-day operation of the
CSC. They tell you how to perform such common tasks as scheduling, displaying and clearing alarms,
and setting the controller for manual operation. Any programmable variables that can affect the
controller operation being described are listed at the beginning of each applicable sub-section.
Determining Chiller System Status
The CSC provides a variety of information that you can use to determine the overall status of the
chiller system. At the keypad/display, you can find most of this information under menus 1 through 9.
The following are available:
• CSC operating state
• Current chiller stage
• Chiller load
• Chiller status (generalized operating state)
• Water temperatures
• Chiller run time
• Load limiting status
• Chilled water distribution system status
• Cooling tower status
The CSC summarizes the most important chiller system information; you can get details about any
chiller by using its keypad/display or the Monitor program. For your convenience, each chiller’s
operating state (generalized), load, run time, and local water temperatures are included in the CSC’s
keypad/display menus.
CSC Operating State
Variable NameKeypad (Menu-Scr.)
CSC Operating State1-1
The CSC Operating State variable tells you what state the CSC—and thus the chiller system—is
currently in. (The chiller system includes everything under the CSC’s supervision; for example,
chillers, cooling towers, and secondary pumps.) At the keypad, it can be displayed by pressing the
STATUS
Off
When the operating state is Off, all chillers, cooling tower fans, and secondary pumps are disabled.
The Off state has five sub-states:
1. Off:Alarm
2. Off:Manual
3. Off:Ambient
4. Off:Network
5. Off:Unoccupied
The sub-state name tells you why the CSC is in the Off state.
Off:Alarm Sub-state:
CSC cannot start for any reason. To get the CSC out of Off:Alarm, you must clear any Fault alarms
that exist. The Off:Alarm state overrides any On state.
key. Four operating states are possible: Off, Recirculate, On, and Free Cooling.
The Off:Alarm state indicates that a CSC Fault alarm exists. In this state, the
48OM127-1
Off:Manual Sub-state:
The Off:Manual state indicates that the CSC’s control mode (menu 10) is
either Manual Off or Service Testing. In this state, the CSC cannot start for any reason. To get the
CSC out of Off:Manual, you must set the control mode to “Automatic” or “Manual On.” The
Off:Manual state overrides any On state.
Off:Ambient Sub-state:
The Off:Ambient state indicates that the CSC’s low ambient lockout feature
is enabled and the outdoor air temperature is below the Low Ambient Lockout Setpoint (menu 10). In
this state, the CSC cannot start for any reason. Before the CSC can leave Off:Ambient, the outdoor air
temperature must rise above the setpoint by a fixed differential of 2°F (1.0°C). Or you could also
disable the feature by setting the Low Ambient Lockout Flag (menu 10) to “No.” The Off:Ambient
state overrides any On state.
Off:Network Sub-state:
The Off:Network state indicates that the CSC’s control mode (menu 10) is
Automatic and the CSC is receiving a shutdown command from a MicroTech Network Master Panel
(NMP) or a building automation system (BAS) communicating via Open Protocol. In the case of an
NMP, the shutdown command can only be issued by an operator at a PC equipped with the Monitor
program. The Off:Network state overrides the On:Schedule, On:Input, and On:Network states.
Off:Unoccupied Sub-state:
The Off:Unoccupied state indicates that the CSC is ready to operate
whenever it receives a start command. Off:Unoccupied is different from the other Off states in that it
is not caused by any one stop condition; for example, a Manual Off control mode. Instead, it is caused
by the absence of a start condition. If the CSC’s control mode (menu 10) is Automatic, any of the
following start conditions override the Off:Unoccupied state and start the system:
• An occupied daily or holiday schedule (CSC or NMP)
• An occupied one-event schedule
• A pre-occupancy optimal start
• An Override Time setting other than zero
• A closed external start/stop input
• A network override from an NMP or BAS
Conversely, Off:Unoccupied can occur only when the CSC’s control mode is Automatic and none of
the above conditions exist.
Recirculate
In systems that have at least one secondary pump, the Recirculate state is used (1) to verify secondary
water flow during the transition between Off and On and (2) to obtain an accurate secondary loop
water temperature reading before optimal start operation. During Recirculate, the secondary pump
system operates normally. The chillers and cooling tower systems are disabled.
On
When the operating state is On, the CSC supervises chiller system operation, deciding which chillers
and auxiliary equipment should operate based on the chiller sequence order and the cooling load. The
On state has four sub-states:
1. On:Manual
2. On:Network
3. On:Input
4. On:Schedule
The sub-state name tells you why the CSC is in the On state.
On:Manual Sub-state:
The On:Manual state indicates that the CSC has started because the control
mode is Manual On and low ambient lockout is not in effect. The On:Manual state overrides the
Off:Unoccupied, Off:Network, and Off:Manual states.
On:Network Sub-state:
The On:Network state indicates that the CSC has started because the control
mode is Automatic, low ambient lockout is not in effect, and at least one of the following start
conditions exists:
• A Global CSC Control Mode setting of “Manual On” at an NMP (set by an operator at a PC)
OM127-149
• A Start network command sent by a BAS
The On:Network state overrides the Off:Unoccupied and Off:Network states.
On:Input Sub-state:
The On:Input state indicates that the CSC has started because the control mode
is Automatic, low ambient lockout is not in effect, and the external start/stop input is closed. The
On:Input state overrides the Off:Unoccupied state. At the keypad/display, the status of the external
start/stop switch is shown on the first screen of menu 8 (“Auto” is open; “Occupied” is closed).
On:Schedule Sub-state:
The On:Schedule state indicates that the CSC has started because the
control mode is Automatic, low ambient lockout is not in effect, and at least one of the following start
conditions exists:
• An occupied daily or holiday schedule (CSC or NMP)
• An occupied one-event schedule
• A pre-occupancy optimal start period
• An Override Time setting other than zero
The On:Schedule state overrides the Off:Unoccupied state.
Free Cooling
During the Free Cooling state, the CSC’s chilled water flow and cooling tower systems operate
normally. The chillers are disabled. This alone is not enough to create free cooling. The Free Cooling
state is provided so that an external controller can implement a custom free cooling strategy in
conjunction with the CSC’s standard chiller system control strategies. Unless it has special software,
the CSC is not capable of coordinating an entire free cooling strategy by itself.
Unlike the other operating states, Free Cooling can only occur as a result of a network command the
CSC receives from a MicroTech Application Specific Controller (ASC) or a building automation
system (BAS) communicating via Open Protocol. In addition to sending the Free Cooling network
command, the ASC or BAS would typically perform many others tasks as part of a free cooling
strategy. For example, it might send different cooling tower setpoints to the CSC, open two-position
bypass valves via digital outputs, and override chiller pumps via digital outputs.
Note:
All free cooling strategies must be approved by personnel in McQuay International’s chiller
applications group. Contact your McQuay representative for information.
Current Chiller Stage
Variable NameKeypad
Current Chiller Stage1-1
Chiller Status Bitset1-1
In the CSC, a chiller stage is defined as a set of chillers. As the CSC sequences chillers on and off, it
(Menu-Scr.)
“stages up” and “stages down.” If the sequence order is set properly, each successive stage has more
capacity than the preceding stage. Additional capacity could be in the form of one added chiller
(typical), two or more added chillers, a chiller swap (in which the replacement chiller has more
capacity than the one that is stopped), or any combination of these. Thus the Current Chiller Stage
variable gives you an indication of how large the cooling load is.
Chillers On
At the keypad/display, the chillers that are on (see note) are shown on menu 1, and the chillers that
make up each stage are shown on menu 13. The chillers that are on should match the chillers that
make up the current stage. If not all of the current-stage chillers are on, the CSC generates the Chiller
Offline alarm.
Note:
On chillers are defined as chillers that have a chiller status of Starting or Running. See “Chiller
Status (Generalized Operating State)” below for more information.
50OM127-1
Chiller Load
Variable NameKeypad
Average Chiller Load1-1
>
Chiller #
Note:
For any given chiller, the chiller load is the percent of available capacity currently being used. The
Load3-1 to -12
The wildcard character (
(Menu-Scr.)
>
) could be 1 through 12.
way the chiller load is calculated depends on the type of chiller. See below.
The CSC uses the average chiller load in its sequencing control processes. When it calculates the
average chiller load, the CSC uses only the chiller load values from operational chillers.
Load Calculation: Centrifugal Chillers
The chiller load for centrifugal chillers is the percent of rated load amps (% RLA).
Load Calculation: Reciprocating and Screw Chillers
The chiller load for reciprocating and screw chillers is the percent of available compressor stages that
are active. If a refrigeration circuit is shut down for some reason, the number of available compressor
stages is reduced and thus the load value increases for a particular stage. Calculating chiller load in
this way allows the CSC’s chiller sequencing logic to work properly when there are partially disabled
chillers in the system.
As an example, consider a two-circuit, eight-stage reciprocating chiller. If the chiller is operating at
stage 3 and both circuits are enabled (8 available stages), the chiller load is 38%. If the chiller is
operating at stage 3 and one circuit is disabled (4 available stages), the chiller load is 75%.
Note:
The method described above is always used to calculate the chiller load—even when the
chiller is equipped with the optional percent-of-unit-amps monitoring package.
Chiller Status (Generalized Operating State)
Variable NameKeypad
>
Chiller #
Note:
The chiller status tells you what general state a chiller is currently in. The following chiller status
Status3-1 to -12
The wildcard character (
(Menu-Scr.)
>
) could be 1 through 12.
states are possible:
• Off
• Starting
• Running
• Stopping
• Comm Loss
Each chiller status at the CSC corresponds to one or more operating states (or other conditions) at a
chiller. For example, the Running chiller status occurs when a Centrif-200 chiller’s operating state is
“Running OK” or when a reciprocating chiller’s operating state is “Stage 2.” For information on
specific chiller operating states, refer to the appropriate MicroTech unit controller operation manual
(see Table 2).
Off
When the chiller status is Off, the chiller is disabled. The Off chiller status has two sub-states:
1. Off:Local
OM127-151
2. Off:CSC
The sub-state name tells you why the chiller status is Off.
Off:Local Sub-state:
The Off:Local chiller status indicates that something at the chiller has it
disabled and thus the CSC is not able to start it. The cause might be, for example, a Fault alarm, an
open remote start/stop switch, or a start-to-start timer that has not expired. Table 38 lists the possible
Off:Local conditions. Throughout this manual, a chiller whose chiller status is Off:Local is called
“locally disabled.”
Table 38. Off:Local Conditions at the Chiller
Chiller ControllerOff:Local Condition at Chiller
Centrif-200 and
HallScrew
Centrif-100
Recip-Standard, Screw,
Recip-European
AGU
Notes:
1. This operating state—and the resultant Off:Local chiller status at the CSC—is temporary. It only occurs during a chiller’s start-up
sequence. If a chiller fails to start because of this condition, its operating state returns to Off:Ready To Start (Centrif-100) or
Off:Remote Comm (Centrif-200, reciprocating, or screw). As a result, the cause of the failure, which may still exist, is not obvious.
2. This operating state can only occur when the chiller’s Control Mode variable is set to “Auto:Local.”
Off:Alarm state
•
Off:Ambient state
•
Off:Front Panel Switch state
•
Off:Manual state
•
Off:Remote Contacts state
•
{
Waiting Low Sump Temp state
•
{
Start-to-start timer not expired when CSC enables chiller(Waiting Cycle Timers state is
•
displayed)
{
Stop-to-start timer not expired when CSC enables chiller(Waiting Cycle Timers state is
•
displayed)
|
Off:Time Schedule state
•
Off:Due To Fault state
•
Off:Manual Switch state
•
{
Waiting Low Sump Temp state
•
Remote start/stop input open(Off:Remote Signal state is temporarily displayed)
•
{
Start-to-start timer not expired when CSC enables chiller(Will Start In xx Min state is
•
displayed)
{
Stop-to-start timer not expired when CSC enables chiller(Will Start In xx Min state is
•
displayed)
Start Mode set to “Local”
•
Off:Alarm state
•
Off:Manual Mode state
•
Off:Remote Switch state
•
Off:System Switch state
•
Off:Pumpdown Switches state
•
Off:Time Clock state
•
{
Waiting For Flow state
•
Off:Alarm state
•
Off:Manual Mode state
•
Off:Remote Switch state
•
Off:System Switch state
•
Off:Pumpdown Switches state
•
Off:Time Clock state
•
{
Waiting For Flow state
•
Unit Disable
•
OAT Lockout
•
Note:
A chiller may go through some transient Off:Local conditions just after the CSC enables it. For
this reason, the CSC ignores a chiller’s status for 60 seconds after that chiller is enabled.
52OM127-1
Off:CSC Sub-state:
The Off:CSC chiller status indicates that the chiller is available, but the CSC has
it disabled. This is the normal chiller status of a chiller that is not part of the current stage. If the
chiller status of a chiller that is part of the current stage is Off:CSC, it is likely that the CSC tried to
start that chiller but was unable to. In this instance, the CSC keeps the chiller off and—in most
cases—stage up. This situation might occur, for example, if the CSC tried to start a chiller that had a
Fault alarm (Off:Local condition), which was subsequently cleared. Table 39 lists the possible
Off:CSC conditions.
Table 39. Off:CSC Conditions at the Chiller
Chiller ControllerOff:CSC Condition at Chiller
Centrif-200 and HallScrewOff:Remote Comm state
Centrif-100Off:Ready To Start state(Off:System Control state is temporarily displayed)
Recip-Standard, Screw, Recip-
Off:Remote Comm state
European, and AGU
Starting
The Starting chiller status indicates that a chiller is going through its start-up sequence after being
enabled either locally or by the CSC. Table 40 lists the possible Starting conditions.
Table 40. Starting Conditions at the Chiller
Chiller ControllerStarting Condition at Chiller
Centrif-200 and
HallScrew
Centrif-100
Recip-Standard, Screw,
Recip-European, and
AGU
Evap Pump On–Recirculate state
•
Start-to-start timer not expired after load recycle shutdown (Waiting Cycle Timers state is
•
displayed)
Stop-to-start timer not expired after load recycle shutdown (Waiting Cycle Timers state is
•
displayed)
Waiting For Load state
•
Pre-Lube state
•
Cond Pump On state
•
Start-Up Unloading state
•
MCR Started state
•
Start-to-start timer not expired after load recycle shutdown (Will Start In xx Min state is
•
displayed)
Stop-to-start timer not expired after load recycle shutdown (Will Start In xx Min state is
•
displayed)
Evap Pump Is On xx state
•
Waiting For Load state
•
Oil Pump Is On xx state
•
Cond Pump Is On xx state
•
Start, Unloading xx state
•
MCR Is On xx state
•
Starting state
•
Wait For Load state
•
Running
The Running chiller status indicates that a chiller is operational. For centrifugal chillers, it means the
compressor is on. For reciprocating and screw chillers, it means at least one compressor is on.
Table 41 lists the possible Running conditions.
Table 41. Running Conditions at the Chiller
Chiller ControllerRunning Condition at Chiller
Centrif-200 and
HallScrew
OM127-153
Running OK state
•
Centrif-100
Recip-Standard, Screw,
Recip-European, and
AGU
Notes:
1. This operating state indicates that the chiller is being controlled locally.
Unit Is Running OK state
•
Stage x state
•
{
Manual Stage x state
•
Stopping
The Stopping chiller status indicates that a chiller is going through its shutdown sequence after being
disabled either locally or by the CSC. Table 42 lists the possible Stopping conditions.
Table 42. Stopping Conditions at the Chiller
Chiller ControllerStopping Condition at Chiller
Centrif-200
Centrif-100
Shutdown Unloading state
•
MCR Off:Routine Shutdown state
•
MCR Off:Rapid Shutdown state
•
Cond Pump Off–Shutdown state
•
Evap Pump Off–Shutdown state
•
Post-Lube state
•
Oil Pump Off–Shutdown state
•
Stop, Unloading xx state
•
MCR Off, Unloading xx state
•
Waiting, High Amps xx state
•
MCR Off, Post-Lube xx state
•
Comm Loss
The Comm Loss chiller status indicates that the CSC has lost communications with a chiller. The
CSC generates a Comm Loss alarm whenever this happens. See the “Alarm Control” section for more
information about what happens when a loss of communications occurs.
Note:
A chiller that is running when it loses communications does not automatically stop.
Water Temperatures
Variable NameKeypad (Menu-Scr.)
Chilled Water Supply Temperature2-1
Chilled Water Return Temperature2-1
Common Entering Condenser Water Temperature2-1 and 6-1
Common Leaving Condenser Water Temperature2-1 and 6-1
Decoupler Temperature2-1
>
Chiller #
Chiller #
Chiller #
Chiller #
Note:
The CSC provides both system water temperatures and, for your convenience, local water
temperatures (at each chiller). Figures 9 and 10 show the locations of these temperature sensors.
Entering Evaporator Water Temperature3-1 to -12
>
Entering Condenser Water Temperature3-1 to -12
>
Leaving Evaporator Water Temperature3-1 to -12
>
Leaving Condenser Water Temperature3-1 to -12
The wildcard character (
>
) could be 1 through 12.
54OM127-1
Figure 9. Chilled Water Temperature Sensor Locations
Cooling Loads
Optional secondary pump/decoupler line
Decoupler line temperature
Chilled water return temperature
Leaving evaporator water temperature
Chilled water supply temperature
Entering evaporator
water temperature
Chiller #1
Evaporator
Chiller #2
Evaporator
a0139
Figure 10. Condenser Water Temperature Sensor Locations
Optional cooling tower bypass
Common entering condenser water temperature
Common leaving condenser water temperature
Leaving condenser water temperature
Entering condenser
water temperature
Chiller #1
Condenser
Chiller #2
Condenser
a0140
Chiller Run Time
Variable NameKeypad (Menu-Scr.)
Chiller # > Operating Hours4-1 to -2
The wildcard character (
Note:
OM127-155
>
) could be 1 through 12.
The CSC tracks the run time of each chiller, which is measured in hours. For centrifugal chillers, run
time is accumulated whenever the compressor is on. For reciprocating and screw chillers, run time is
accumulated whenever at least one compressor is on. The CSC uses this run-time data to set the
sequence order when the Chiller Sequence Order Option (menu 11) is set to “Automatic.”
Load Limiting Status
Variable NameKeypad (Menu-Scr.)
System Load Balancing Load Limit5-1
System Demand Limiting Load Limit5-1
Start-Up Unloading Group #1 Load Limit5-2
Start-Up Unloading Group #2 Load Limit5-2
Start-Up Unloading Group #3 Load Limit5-2
Start-Up Unloading Group #4 Load Limit5-2
>
Chiller #
External Demand Limiting Signal8-2
Stage-Up Inhibit Level9-1
Note:
The CSC can perform four types of load limiting:
1. Load balancing
2. Start-up unloading
3. Demand limiting
4. Stage-Up Inhibiting
Following are brief explanations of them. For more information, see the “Load Limiting Control”
section in the “Description of Operation” portion of this manual.
Load Limit5-3 to -4
The wildcard character (
>
) could be 1 through 12.
Percent-of-Capacity Limiting
The first three types of load limiting prevent the affected chillers from exceeding a certain percentage
of their capacity. At the keypad/display, the effects of these load limiting functions are shown on
menu 5.
When no percent-of-capacity load limit is in effect, the load limit sent to each chiller is 100%. When
any one is in effect, the load limit is less than 100%; for example, 92%. Each chiller receives the
minimum of the three percent-of-capacity load limit values that apply to it (see below). The Chiller #
Load Limit variables show the load limit values the CSC sends to the individual chillers.
A centrifugal chiller uses a load limit value it receives from the CSC in the same manner as a load
limit value it might generate internally:
1. Loading is inhibited when the load (% RLA) is equal to the load limit or 1% to 4% above the
load limit.
2. Unloading occurs when the load is 5% or more above the load limit.
A reciprocating or screw chiller, which can only be affected by the demand limiting function,
converts the load limit value it receives from the CSC into a maximum stage value.
Load Balancing:
When load balancing is enabled (menu 14), it applies to all centrifugal chillers
associated with the CSC. The System Load Balancing Load Limit variable shows the current value.
Start-Up Unloading:
chillers. The Start-Up Unloading Group #
Demand Limiting:
Start-up unloading can be assigned to four separate groups of centrifugal
>
Load Limit variables show the load limit for each group.
When the CSC receives a demand limiting signal, it sends it to all chillers
associated with it. The System Demand Limiting Load Limit variable shows the current value. If an
external voltage or current is being used, the External Demand Limiting Signal variable shows the
conditioned value of the input. (The ICM conditions all analog inputs to 0–5 Vdc signals.)
>
56OM127-1
Chiller Stage-Up Inhibiting
The last type of load limiting, stage-up inhibiting, prevents additional chillers from being enabled by
preventing a load-based stage-up. (A stage-up can still occur if an operational chiller becomes locally
disabled or loses communications.) Stage-up inhibiting is either on or off. If it is off, the CSC stages
normally. If it is on, the CSC can stage down, but it cannot stage up. Stage-up inhibiting does not
affect the loading on each chiller; instead, the overall system load is limited to the available capacity
of all operational chillers.
The CSC has two types of stage-up inhibiting: (1) Daily and (2) Network. Daily stage-up inhibiting is
on when the current time is later than the Inhibit Stage-Up After Time (menu 11). Network stage-up
inhibiting is on when the Stage-Up Inhibit Level is greater than or equal to the Stage-Up Inhibit
Setpoint (menu 11). This network signal can come to the CSC from a MicroTech Network Master
Panel or a building automation system communicating via Open Protocol.
Chilled Water Distribution System Status
Variable NameKeypad (Menu-Scr.)
Differential Pressure Bypass Valve Position or Secondary VFD Pump Speed7-1
Chilled Water Loop Pressure Difference7-1
Current Sequenced Pump Stage7-1
Secondary Pump #1 Operating Hours7-1
Secondary Pump #2 Operating Hours7-1
>
Secondary Pump #
Secondary Pump #
Decoupler Flow Rate8-2
The wildcard character (
Note:
Output State7-2 to -3
>
Status7-2 to -3
>
) could be 1 through 6.
The CSC can maintain a constant differential pressure across the cooling loads by controlling a
bypass valve, variable speed secondary pump(s), or a set of sequenced secondary pumps. For
applications that require a “lead/standby” arrangement of two secondary pumps, the CSC can
automatically alternate the lead pump to equalize run time. For more information, see the “Chilled
Water Flow Control,” section in the “Description of Operation” portion of this manual.
Decoupler Line Flow Rate
For primary-secondary systems, the CSC uses the flow rate through the decoupler line to determine
whether it should stage down. If the flow rate from supply to return is greater than the flow that would
be lost after a stage down (plus an adjustable differential), a stage down becomes possible. For more
information, see the “Chiller Sequencing Control” section of this manual.
Cooling Tower Status
Variable NameKeypad (Menu-Scr.)
Current Cooling Tower Stage6-1
Cooling Tower Bypass Valve Position6-1
Common Entering Condenser Water Temperature6-1 and 2-1
Common Leaving Condenser Water Temperature6-1 and 2-1
Cooling Tower Alarm Input Status8-1
The CSC can maintain a common entering or leaving condenser water temperature by controlling up
to 12 cooling tower stages and a bypass valve. For more information, see the “Cooling Tower
Control,” section in the “Description of Operation” portion of this manual.
OM127-157
Auto/Manual Operation
WARNING
!
Electric shock and moving machinery hazard. Can cause severe personal injury or death.
When the CSC or a chiller controller is in the Off state, power is not removed from the chiller
controller or components. Lock power off by means of the unit disconnect switch before
servicing line voltage equipment on a chiller.
CSC Control Mode
Variable NameKeypad (Menu-Scr.)
CSC Control Mode10-1
Digital Output > Service Test State
>
Analog Output
Notes:
1. The wildcard character (
2. The wildcard character (
Service Test Setpoint
You can set up the chiller system for automatic or manual operation with the CSC Control Mode
variable. Following are descriptions of the four possible modes.
Manual Off
{
|
>
) could be 0 through 23.
>
) could be 0 through 3.
30-1 to -4
30-5
The Manual Off mode places the CSC into the Off: Manual state. As a result, the CSC disables all of
its associated chillers that are set up for automatic operation, placing them into the Off:CSC chiller
state. Auxiliary equipment such as secondary pumps and cooling tower fans also shut down.
Automatic
The Automatic mode allows the chiller system to operate automatically. This means that the CSC
enables and disables chillers according to its scheduling, operator override, network override, optimal
start, low ambient lockout, and sequencing control features. When the CSC has enabled at least one
chiller, it also controls auxiliary equipment such as secondary pumps.
Manual On
When the CSC is in the Manual On mode, it acts as though it were in the Automatic mode with a
permanently occupied schedule. This means that the CSC enables and disables chillers according to
its low ambient lockout and sequencing control features. When the CSC has enabled at least one
chiller, it also controls auxiliary equipment such as secondary pumps and cooling tower fans.
Service Testing
The Service Testing control mode is a special mode that allows a technician to test the CSC’s analog
and digital outputs, the field wiring to them, and the auxiliary equipment they control. Service Testing
is similar to Manual Off; the only difference is that each output can be manually controlled with the
items in menu 30. For example, if the control mode is Service Testing and the Digital Output 3
Service Test State variable is set to “On,” LED 3 on the Output Board should light and Pump #1
should start and run. And if the Analog Output 0 Service Test Setpoint is set to “100%,” the cooling
tower bypass valve should fully open to the tower.
Operator Override
Variable NameKeypad (Menu-Scr.)
CSC Control Mode10-1
Override Time24-1
58OM127-1
There are two ways an operator can start the chiller system during a scheduled unoccupied period:
timed override and non-timed override. Both methods have the same authority as a scheduling
function; thus (1) they can only override the Off:Unoccupied state, and (2) the CSC Control Mode
must be set to “Automatic” to use them.
Note:
These two override methods require that the operator be present to implement the override. If
this is not possible, the CSC’s one-event time schedule can be used instead.
Timed Override
With the Override Time variable, you can manually set a timer that overrides the Off:Unoccupied
state for the length of time specified. Override Time can be set for any amount of time up to 60 hours
in 15-minute increments. After it is set, the Override Time variable shows the time remaining in the
override period. You can reset it (up or down) at any time. If nothing else is enabling the CSC (for
example, an occupied schedule), the operating state returns to Off:Unoccupied when the timer
expires. During a timed override period, the operating state is On:Schedule.
Non-timed Override
You can use the CSC’s external start/stop input to override the Off:Unoccupied state indefinitely. If
the switch or relay contact connected to it is closed, the CSC is enabled. If nothing else is enabling the
CSC (for example, an occupied schedule), the operating state returns to Off:Unoccupied when the
switch or relay opens. During a non-timed override period, the operating state is On:Input.
Note:
The external start/stop contact can be used for non-timed override, external time clock
scheduling, or both (wired in parallel). For more on external time clocks, see the following
“Scheduling” section.
Network Override
Variable NameKeypad (Menu-Scr.)
CSC Control Mode10-1
The CSC’s operating state can be overridden by a network command received from any of three
sources: a MicroTech Network Master Panel (NMP), a MicroTech Application Specific Controller
(ASC), or a building automation system (BAS) communicating with the CSC via Open Protocol.
Regardless of the source, the network command has one higher level of authority than a scheduling
function; thus it can override the Off:Unoccupied, On:Schedule, and On: Input states. The Control
Mode must be set to “Automatic” to use a network command; otherwise, the command is ignored.
The five network override commands and their resultant operating states are as follows:
Network commandCSC Operating State
StopOff:Network
Autovaries; CSC is in normal operation
StartRecirculateOn:Network
RecirculateRecirculate
Free CoolingFree Cooling
These operating states occur only when the CSC’s control mode is Automatic and the conditions for a
higher authority Off state (Off:Alarm, Off:Manual, or Off:Ambient) do not exist.
NMP Source
When the source of the network command is an NMP, the command must be manually issued by an
operator at a PC. The NMP variable that holds the network command is called the Global CSC
Control Mode because it affects all CSCs in the network.
OM127-159
ASC Source
When the source of the command is an ASC, the command may be issued by an operator at a PC or
automatically by the ASC’s custom software. An ASC might be used, for example, to coordinate a
free cooling strategy in which primary chilled water pumps are started, valves are opened, cooling
tower setpoints are changed, and the Free Cooling network command is sent to the CSC.
BAS Source
When the source of the command is a BAS, the command may be manually issued by an operator at a
PC or automatically issued by the BAS’s scheduling function or a custom free cooling strategy.
To schedule the CSC with a BAS, the BAS would typically send a Start command during occupied
periods and a Stop or Auto command during unoccupied periods. If the Stop command is used, the
operator override and internal scheduling features do not work. If the Auto command is used, the
operator override and internal scheduling features work, but its internal schedules must be set for
unoccupied and its external start/stop switch must be open before the system can shut down.
A BAS might also be used, for example, to coordinate a free cooling strategy in which primary chilled
water pumps are started, valves are opened, cooling tower setpoints are changed, and the Free
Cooling network command is sent to the CSC.
Loss of Communications
If the NMP, ASC, or BAS loses communications with the CSC, it retains and uses the last network
command it received for 10 minutes. After that it automatically changes the network command to
Auto. As a result, it operates according to its internal scheduling and operator override features.
You can use this fact to fail-safe your system. For example, if you’re using a BAS to schedule the
CSC, you may want to set the internal schedules for the same hours as the BAS schedules or even for
continuous operation. For more information, see the following “Scheduling” section.
Caution:
setpoints as it changes the network command, the CSC should be set up to shut down the system upon
a loss of communications during any period when free cooling is possible. If this is not done, chillers
could start and operate with extremely low condenser water temperatures.
If an ASC or BAS is coordinating a free cooling strategy in which it changes cooling tower
Local Override
CSC control can be overridden if you want to enable or disable a chiller locally (at the chiller);
however, this should be done only if it is absolutely necessary. If you locally enable or disable a
chiller that is part of the current chiller stage, the CSC generates the Chiller Offline alarm and forces a
stage-up, causing another chiller to start. If you locally enable a chiller that the CSC has disabled, the
average load could decrease enough to cause a stage-down to occur.
Following are several ways to locally enable or disable a chiller. When you disable a chiller as
described below, it cannot run for any reason. When you enable a chiller as described below, it
runs—if the CSC is the only thing disabling it. (For example, if there is a Fault alarm in a chiller, the
chiller cannot start if you try to enable it locally.)
Centrif-200 and HallScrew Chillers
To locally disable a chiller, do one of the following:
• Set the chiller’s control mode to “Manual Off.”
• Set the chiller’s control mode to “Auto:Local” and set the chiller’s schedule for unoccupied
operation.
• Set the chiller’s front panel switch to “Stop.”
• Open the chiller’s remote stop switch input.
To locally enable a chiller, do one of the following:
• Set the chiller’s control mode to “Manual Enable.”
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• Set the chiller’s control mode to “Auto:Local” and set the chiller’s schedule for occupied
operation.
Centrif-100 Chillers
To locally disable a chiller, do one of the following:
• Set the chiller’s front panel switch to “Stop.”
• Open the chiller’s remote stop switch input.
To locally enable a chiller, remove the network communications connector from port B on the display
processor and cycle power to the controller.
Recip-Standard, Screw, Recip-European, and AGU Chillers
To locally disable a chiller, do one of the following:
• Set the chiller’s control mode to “Manual Unit Off.”
• Set the chiller’s schedule for unoccupied operation.
• Set the chiller’s pumpdown switches to “Pumpdown and Stop.”
• Set the chiller’s system switch to “Emergency Stop.”
• Open the chiller’s remote stop switch input.
To locally enable a chiller, do one of the following:
• Set the chiller’s control mode to “Manual Staging” and set the desired stage number.
• Remove the network communications connector from port B on the MCB, cycle power to the
controller, and set the chiller’s schedule for occupied operation.
Low Ambient Lockout
Variable NameKeypad(Menu-Scr.)
Low Ambient Lockout Flag10-1
Low Ambient Lockout Setpoint10-1
The CSC’s low ambient lockout feature can disable the entire chiller system whenever the outdoor air
temperature is less than the Low Ambient Lockout Setpoint. If this occurs, the operating state changes
to Off:Ambient. As a result, the CSC disables all of its associated chillers and shuts down all auxiliary
system equipment. This occurs regardless of the control mode setting.
When the outdoor air temperature rises to equal the Low Ambient Lockout Setpoint plus its
differential, which is fixed at 2°F (1.1°C), the CSC enables normal chiller system operation again.
Note:
If communications are lost with an NMP or building automation system that is supplying the
outdoor air temperature to the CSC, it retains and uses the last temperature it received until
communications are restored.
To set up low ambient lockout
1. Set the Low Ambient Lockout Flag to “Yes.”
2. Set the Low Ambient Lockout Setpoint as required.
Note:
To use the low ambient lockout feature, an outdoor air temperature sensor must be connected
to the CSC, a Network Master Panel (NMP), or a building automation system (BAS) communicating
with the CSC via Open Protocol.
Rapid Restart
Variable NameKeypad (Menu-Scr.)
Rapid Restart Time10-1
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The rapid restart feature allows you to specify how you want the chiller system to react after the CSC
has a temporary loss of power. If this happens, it loses communications and its supervisory control of
the chillers. In this instance, Centrif-200 chillers revert to local control after 5 minutes, and all other
chillers stay in whatever state they were in when communications failed.
If the power-loss period is less than the Rapid Restart Time setting, the CSC returns to normal
operation without changing the current chiller stage when its power is restored. Any operational
chillers in the current stage continue to operate.
If the power-loss period is greater than the Rapid Restart Time setting, the CSC returns to normal
operation when its power is restored, but it resets the current chiller stage to stage 0. Any operational
chillers are disabled.
For more on what happens when the CSC loses communications with its chillers, see the “Alarm
Control” section in the “Description of Operation” portion of this manual.
Scheduling
The CSC can be scheduled for occupied operation with any of five methods:
1. CSC internal daily scheduling
2. CSC internal holiday scheduling
3. CSC internal one-event scheduling
4. Network Master Panel (NMP) scheduling
5. External time clock
This section describes how to use the CSC’s internal scheduling features. Internal variables that must
be set to use the NMP scheduling method or an external time clock are also discussed. For
information on how to use the NMP scheduling function, refer to the literature provided with the
Network Master Panel. For information on how to connect an external time clock, refer to the “Field
Wiring” section of Bulletin No. IM 618, MicroTech Chiller System Controller.
The CSC’s optimal start feature works in conjunction with the internal daily and holiday scheduling
methods. When optimal start is enabled, the CSC can start the chiller system early to ensure that the
loop temperature is cold when the normal scheduled start time occurs.
Scheduling Method Interaction
When any of the above scheduling functions is calling for occupied operation, the CSC (chiller
system) operates—if its control mode is Automatic. Conversely, it goes into its unoccupied state only
when all of the above scheduling methods are calling for unoccupied operation. Therefore, any
unused schedules should be set for continuous unoccupied operation. (An unassigned NMP schedule
or a disconnected external time clock are equivalent to an unoccupied setting for those functions.)
Chiller Controller Setup
Every MicroTech-equipped chiller has its own internal scheduling capability. When chillers are
networked with a CSC, these chiller schedules are not used because the CSC coordinates chiller
operation. Thus the system (CSC) is scheduled rather than the individual chillers.
Centrif-200 and HallScrew:
operation when the chiller’s control mode is set to “Auto:Network.” This allows them to be set as
appropriate for a situation in which communications are lost with the CSC. In this instance the local
chiller schedules are used.
Centrif-100:
operation when the chiller’s start mode is set to “Remote.” Unlike Centrif-200 chillers, the local
schedules are not used if communications between the series-100 chiller and the CSC fail. Therefore,
no setup is required for local series-100 chiller schedules; they can be set to anything.
Individual Centrif-100 chiller controller schedules cannot affect chiller system
Individual chiller controller schedules cannot affect chiller system
62OM127-1
Recip-Standard, Screw, Recip-European, and AGU:
Individual reciprocating, screw, and global
chiller controller schedules can affect chiller system operation. These chillers must be in a locallyscheduled occupied period before the CSC can enable them. If one of these chillers is in a scheduled
unoccupied period, it is locally disabled. Thus each chiller’s schedule should normally be set for
continuous occupied operation (00:00–23:59) so that the CSC can always have complete authority
over scheduling.
Setting Time and Date
Variable NameKeypad (Menu-Scr.)
Current Time23-1
Current Day23-1
Current Date23-1
The CSC uses the time and date to execute its internal scheduling functions. Once set, the batterybacked internal clock keeps the current time regardless of whether power is supplied to the panel.
You can set the time of day by entering the hour (0–23), minute (0–59), and second (0–59) into the
Current Time variable’s three fields; the day of the week by entering the day (Sun–Sat) into the
Current Day variable’s one field; and the date by entering the month (Jan–Dec), date (1–31), and year
(0–99) into the Current Date variable’s three fields.
Daily Scheduling
Variable NameKeypad (Menu-Scr.)
Sunday Schedule24-1
Monday Schedule24-1
Tuesday Schedule24-2
Wednesday Schedule24-2
Thursday Schedule24-2
Friday Schedule24-2
Saturday Schedule24-2
Holiday Schedule24-2
NMP Schedule Number24-1
With the CSC’s internal daily scheduling function, you can set one start and one stop time for each
day of the week and for designated holidays (see below).
As shown in Figure 11, each daily schedule has four adjustable fields: start hour, start minute, stop
hour, and stop minute. The schedule shown in Figure 11 would cause the chiller system to start up at
6:30 a.m. and shut down at 6:00 p.m. every Monday.
Figure 11. Daily Schedule Fields
Start hour
Start minute
Stop hour
Stop minute
Mon 06:30-18:00
For continuous chiller system operation, set the schedule fields to “00:00–23:59.” To keep the chiller
system off for the entire day, set the schedule fields to “00:00–00:00” (this is the default).
If you want the CSC to have complete authority over chiller system scheduling, set the NMP
Schedule Number variable to “NA” (this is the default setting) and do not connect a clock to the
external start/stop input.
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Note:
An internal daily schedule’s start time must occur before its stop time; otherwise, the chiller
system cannot start that day. If you want to schedule the chiller system to shut down and then start up
again on the same day, you must (1) use an NMP schedule, (2) use an external clock, or (3) use a
combination of scheduling methods; for example, a CSC daily schedule and a one-event schedule.
NMP Scheduling
If a Network Master Panel is included in the network with the CSC, an NMP schedule can be used to
schedule chiller system operation. To use an NMP schedule, set the CSC’s NMP Schedule Number
variable as desired. When the CSC Control Mode (menu 10) is set to “Automatic,” the NMP schedule
you selected enables and disables the chiller system. If you don’t want the CSC to influence
scheduling, set the internal daily schedule variables to “00:00–00:00” (the default setting).
Using an External Time Clock
If desired, an external clock can be used to schedule chiller system operation. The clock must be
connected to the CSC’s external start/stop input (DI 0). When the CSC Control Mode (menu 10) is
set to “Automatic,” the external clock enables and disables the chiller system. If you don’t want the
CSC to influence scheduling (likely), set the CSC’s internal daily schedule variables to “00:00–
00:00” (the default setting).
An external clock does not actually schedule the CSC; it works by overriding the Off:Unoccupied
state. Therefore, when the external clock is in the occupied mode, the CSC’s system status is
“On:Input” instead of “On:Schedule.” The effect is the same—except that the CSC’s optimal start
feature cannot work with an external clock.
Holiday Scheduling
Variable NameKeypad (Menu-Scr.)
Holiday Schedule24-2
Holiday Date #
Holiday Date #
Note:
>
>
Duration25-1 to -4
The wildcard character (
25-1 to -4
>
) could be 1 through 12.
You can schedule special operating hours for up to 12 holiday periods by using the CSC’s holiday
scheduling feature. Whenever a holiday date occurs, the controller uses the Holiday Schedule’s start
and stop times for the number of successive days you specify with the associated holiday date
duration variable. For example, assume that this year Christmas Eve occurs on a Thursday. Your
building is shut down on both Christmas Eve and Christmas Day, but operates normally on the
weekend. To schedule this holiday, set the Holiday Schedule to “00:00–00:00”; set the Holiday Date
#1 variable to “Dec 24”; and set the Holiday Date #1 Duration variable to “2 Days.”
If any of the 12 holiday dates are not required, enter “N/A” into the month field of those holiday dates
(the default setting).
Note:
In addition to allowing special operating hours, the CSC’s holiday scheduling feature can be
used to specify certain days on which the chiller or secondary pump (lead/ standby) sequence order is
forced to change. If you specify a holiday date to force a sequence order change and you’re using the
internal daily scheduling function, be sure to set the Holiday Schedule’s start and stop times as
required for chiller system operation on that day. For more information, see the “Chiller Sequencing
Control” and “Chilled Water Flow Control” sections.
One-Event Scheduling
Variable NameKeypad (Menu-Scr.)
One Event Schedule24-1
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With the CSC’s internal one-event scheduling function, you can schedule one special period of
occupied operation that is outside (or around) the normal daily and holiday schedules. The one-event
schedule is similar to the timed operator override feature discussed in the previous “Auto/Manual
Operation” section. The difference is that the override period can be set in advance.
As shown in Figure 12, the one-event schedule has five adjustable fields: start month, start date, start
hour, start minute, and duration. The schedule shown in Figure 12 starts the chiller system at
4:30 a.m. on July 1 and shuts down 20.5 hours later. Following is an example that uses these values.
Assume that your building is a department store and on Saturday July 1 there is a sale that requires
the chiller system to start up at 4:30 a.m. and shut down at 1:00 a.m. on Sunday morning. The normal
start and stop times are 6:00 a.m. and 11:00 p.m. for both Saturday and Sunday. Although you can
change the normal Saturday and Sunday schedules to for the sale (and then change them back before
the normal 6:00 a.m. Sunday start), it is much easier to enter a one-event schedule.
Figure 12. One Event Schedule Fields
Start Month
Start Date
Start Hour
Start Minute
Duration
One Event = Jul-01 04:30 for 20.50 Hrs
a0238
To disable the one-event schedule, set its start month field to “N/A.”
Optimal Start
Variable NameKeypad (Menu-Scr.)
System Setpoint16-1
Optimal Start Flag26-1
Auto Update Flag26-1
Optimal Start Begin Recirculate Time26-1
Optimal Start Recirculation Period26-1
Today’s Optimal Start Time (status only)26-1
Table of Optimal Start Time Increments27-1 to -3
The adaptive optimal start feature works with the internal daily and holiday scheduling functions to
start the chiller system early during periods of high cooling load. The goal of optimal start is to drop
the chilled water supply temperature to the System Setpoint just as the normal occupied period
begins. Optimal start uses an algorithm that adapts to the characteristics of your chiller system.
The following events occur:
1. The secondary pumps are started and operated just long enough to get a representative return
chilled water temperature.
2. The return chilled water and outdoor air temperatures are sampled. Based on these temperatures,
an estimate is made of the amount of time required to pull the chilled water supply temperature
down to the System Setpoint.
3. An optimal start time is calculated by subtracting the estimate from the scheduled start time.
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4. The system starts and operates. When the chilled water supply temperature reaches the System
Setpoint, the time that it took is averaged with the estimate—if you want to adapt the time.
Note:
Optimal start control can be used only with primary-secondary systems in which the CSC is
controlling the secondary pump(s).
How Optimal Start Works
Optimal chiller system start-up can occur only during a window prior to occupancy that is defined by
the scheduled start-up time for the day, the Optimal Start Begin Recirculate Time variable, and the
Optimal Start Recirculation Period variable. See Figure 13.
Figure 13. Optimal Start Time Line
Optimal Start Begin Recirculate Time
CSC samples temperatures and
calculates optimal start time
Scheduled start-up time
Optimal start window
time
Optimal Start
Recirculation Period
Today's Optimal Start Time
Optimal start
time increment
When the Optimal Start Begin Recirculate Time occurs, the CSC enters the Recirculate operating
state and starts the secondary pump(s). The Optimal Start Recirculation Period variable defines the
length of time the CSC remains in the Recirculate state. At the end of the recirculation period, the
CSC samples the return chilled water and outdoor air temperatures.
The exacttime at which the CSC enables the chiller system is determined by the Table of Optimal
Start Time Increments, shown in Table 43 with its default values. For any combination of return water
and outdoor air temperatures, a particular time increment in the table is used. Notice that as the return
water or outdoor air temperature increases, the optimal start time increment increases. If the
temperatures don’t exactly match those in the table, the controller selects the closest table value.
Table 43. Default Optimal Start Time Increments (in Min.)
Return Chilled Water Temperature
Outdoor Air Temperature50°F(10°C)60°F(15°C)70°F(21°C)80°F(26°C)90°F(32°C)
50°F (10°C)510152025
60°F (15°C)1015202530
70°F (21°C)1520253035
80°F (26°C)2025303540
90°F (32°C)2530354045
100°F (38°C)3035404550
For example, if the return water temperature is 83°F (28°C) and the outdoor air temperature is 87°F
(31°C), the optimal start time increment would be 40 minutes. If the outdoor air temperature were
106°F (41°C) instead of 87°F (31°C), the optimal start time increment would be 45 minutes. (This
example is based on the default time increment values shown in Table 43.)
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The CSC subtracts the start time increment from the scheduled start time to get Today’s Optimal Start
Time. If the calculated optimal start time is after the current time, the CSC returns to the
Off:Unoccupied state, stops the secondary pump(s), and waits. If the calculated optimal start time is
before the current time, the CSC immediately enters the On:Schedule state and starts the system.
Note:
If the return water or outdoor air temperature sensor fails, the optimal start algorithm assumes
that the unreliable temperature is higher than those in the table. As a result, the increment used is
likely be higher, and thus the CSC starts the chiller system earlier than it would otherwise.
Note:
If communications are lost with an NMP or building automation system that is supplying the
outdoor air temperature, the CSC retains the last temperature it received and uses it until
communications are restored.
Adaptation
Each day, the CSC keeps track of how long it takes the chilled water supply temperature to reach the
System Setpoint after start-up. When the supply temperature falls to the setpoint, the controller
averages this amount of time with the optimal start time increment that it used. The CSC replaces the
old table value with the new averaged value. This adaptation process only occurs if the Auto Update
Flag is set to “Yes.” Adaptation is illustrated below in “Typical Operating Sequence.”
If the supply temperature reaches the System Setpoint before the scheduled start-up time, the system
continues to operate; it does not shut down and then start up again. Over time, adaptation reduces the
amount of overshoot or undershoot.
You can manually adjust each value in the Table of Optimal Start Time Increments. The CSC
continues to use and—if adaptation is enabled—change whatever values are contained in the table.
Typical Operating Sequence
Following is an example of how the optimal start feature works. Assume that the following is true:
1. The Table of Optimal Start Time Increments contains the default values shown in Table 43.
2. The return chilled water temperature is 82.4°F (28.0°C).
3. The outdoor air temperature is 86.7°F (30.4°C).
4. The System Setpoint is 44.0°F (6.6°C).
5. The Optimal Start Begin Recirculate Time is 6:00 a.m.
6. The Optimal Start Recirculation Period is 10 minutes.
7. The scheduled start time is 7:00 a.m.
At 6:00 a.m., the CSC starts the secondary pump as it enters the Recirculate operating state. At
6:10 a.m., it reads the two temperatures above, stops the pump, and returns to the Off:Unoccupied
state. The Today’s Optimal Start Time variable changes to “6:20” because the optimal start time
increment is 40 minutes. As a result, the chiller system is enabled at 6:20 a.m., or 40 minutes early.
The chilled water supply temperature ideally falls to 44.0°F (6.6°C), the System Setpoint, right at
7:00 a.m. Following are two scenarios that illustrate how the optimal start feature adapts if this
doesn’t happen.
Scenario 1:
The chilled water supply temperature falls to the System Setpoint at 7:12 a.m., or 52
minutes after start-up. When this occurs, the CSC updates the optimal start table by changing the time
increment that it used to 46 minutes, the average of 52 and 40.
Scenario 2:
The chilled water supply temperature falls to the System Setpoint at 6:36 a.m., or 16
minutes after start-up. When this occurs, the CSC updates the optimal start table by changing the time
increment value that it used to 28 minutes, the average of 16 and 40.
To set up optimal start control
1. Set the Optimal Start Flag to “Yes.”
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2. If you want the CSC to automatically adapt to your chiller system’s characteristics, set the Auto
Update Flag to “Yes.”
3. Set the Optimal Start Begin Recirculate Time to the desired time after which optimal chiller
system start-up can be possible, allowing time for the recirculation period.
A typical setting would be about one hour before the normal scheduled start time.
Note:
The scheduled start time and the Optimal Start Begin Recirculate Time must be on the
same day.
4. Set the Optimal Start Recirculation Period to the amount time you want the secondary pump(s) to
run before the CSC takes a temperature reading at the return chilled water sensor.
The CSC requires an accurate return water temperature to estimate the load and thus the optimal
start-up time.
Note:
The CSC’s optimal start feature works only with systems that have at least one secondary
pump. To use the optimal start feature, chilled water supply and return temperature sensors must
be connected to the CSC. In addition, an outdoor air temperature sensor must be connected to the
CSC, an NMP, or an Open Protocol building automation system.
Alarm Monitoring
About Alarms
The CSC and chiller controllers are programmed to monitor their equipment for specific alarm
conditions that may occur. If the CSC or a chiller controller detects an alarm condition, it indicates
the alarm, identifies the alarm, and executes appropriate control actions that fail-safe the equipment.
The CSC also indicates the existence of chiller alarms, and it tells you which chiller or chillers have
them. It tells you the type of chiller alarm (Fault, Problem, or Warning), but it can not identify
specific chiller alarms. For example, if the Low Evaporator Pressure alarm occurs in Chiller #1
(assume it’s reciprocating), the chiller controller’s keypad/display shows “Lo Evap Pressure” and the
CSC’s keypad/display shows “Chil #1= Fault.” If you were at the CSC, you would immediately know
that a Fault alarm occurred in Chiller #1.
In addition to chiller alarms, the CSC monitors the network for loss-of-communications alarms. This
type of alarm is indicated only at the CSC. If a loss-of-communications alarm occurs, the CSC
indicates the existence of the alarm and tells you which chiller or chillers are affected.
For detailed information on CSC alarms, refer to Table 45 and the “Alarm Control” section in the
“Description of Operation” portion of this manual. For detailed information on chiller alarms, refer to
the appropriate MicroTech unit controller operation manual (see Table 2).
Alarm Indication
The CSC has three components that can indicate an alarm: the Alarm LED, the Alarm Horn, and the
Alarm Output. The Alarm LED always flashes when an alarm occurs. The Alarm Horn and the Alarm
Output can be independently set to indicate certain alarms in different ways. The default setup is
shown in Table 44.
Silencing the Alarm Horn
To silence the CSC’s Alarm Horn, press the
clear the alarm, and it does not return the Alarm Output to its normal state. See “Clearing Alarms”
below for more information.
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ALARM
key. Note that silencing the Alarm Horn does not
Table 44. Default Alarm Indication Setup
Indication
Alarm TypeAlarm LEDAlarm HornAlarm Output
Comm LossFlash (not adj.)OffFast Pulse
FaultFlash (not adj.)OnFast Pulse
ProblemFlash (not adj.)OnSlow Pulse
WarningFlash (not adj.)OffSlow Pulse
Normal StateOff (not adj.)Off (not adj.)Open
Priority
The various alarms that can occur in MicroTech unit controllers are prioritized by severity. Three
categories are possible: Fault, Problem, and Warning. A fourth category is possible in the CSC and
other MicroTech controllers that network unit controllers together: Comm Loss.
Faults are the highest priority alarms. If a Fault occurs, the equipment (CSC or chiller) is shut
Fault:
down until the alarm condition is gone and the Fault is cleared. Reciprocating and screw chillers have
a sub-category of Fault alarms: the Circuit-Fault. If a Circuit-Fault occurs, the affected refrigeration
circuit is shut down until the alarm condition is gone and the Fault is cleared. Most Fault alarms must
be manually cleared.
Problem:
Problems have lower priority than Faults. If a Problem occurs, the equipment is not shut
down, but its operation is modified in some way to compensate for the alarm condition. Most Problem
alarms automatically clear when the alarm conditions that causes them returns to normal.
Warning:
Warnings are the lowest priority alarms. No control action is taken when a Warning
occurs; it is simply indicated to alert the operator that the alarm condition needs attention. Most
Warning alarms automatically clear when the alarm conditions that caused them returns to normal.
Comm Loss:
Depending on the application, the priority of a loss-of-communications, or “Comm
Loss,” alarm varies. In the CSC, the priority of Comm Loss alarms is higher than Problem alarms and
lower than Fault alarms. Comm Loss alarms automatically clear when communications are restored
with the affected chillers.
Table 45. CSC Alarms
Alarm TypeAlarm MessageIndicationReset
FaultLvg CndW T FailCommon leaving condenser water temperature sensor failed while it was
the cooling tower Control Temperature source
Ent CndW T FailCommon entering condenser water temperature sensor failed while it
was the cooling tower Control Temperature source
No Sec ChW FlowAll secondary pumps failed, resulting in a loss of chilled water flow to
the loads
Comm LossNo Comm Chil #12Communications lost between CSC and Chiller #12Auto
No Comm Chil #11Communications lost between CSC and Chiller #11Auto
No Comm Chil #10Communications lost between CSC and Chiller #10Auto
No Comm Chil #9Communications lost between CSC and Chiller #9Auto
No Comm Chil #8Communications lost between CSC and Chiller #8Auto
No Comm Chil #7Communications lost between CSC and Chiller #7Auto
No Comm Chil #6Communications lost between CSC and Chiller #6Auto
No Comm Chil #5Communications lost between CSC and Chiller #5Auto
No Comm Chil #4Communications lost between CSC and Chiller #4Auto
No Comm Chil #3Communications lost between CSC and Chiller #3Auto
No Comm Chil #2Communications lost between CSC and Chiller #2Auto
No Comm Chil #1Communications lost between CSC and Chiller #1Auto
Manual
Manual
Manual
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Alarm TypeAlarm MessageIndicationReset
ProblemDecouple F FailDecoupler line flow rate sensor failedAuto
Sec Pump #6 FailSecondary Pump #6 status not proven after output was energizedManual
Sec Pump #5 FailSecondary Pump #5 status not proven after output was energizedManual
Sec Pump #4 FailSecondary Pump #4 status not proven after output was energizedManual
Sec Pump #3 FailSecondary Pump #3 status not proven after output was energizedManual
Sec Pump #2 FailSecondary Pump #2 status not proven after output was energizedManual
Sec Pump #1 FailSecondary Pump #1 status not proven after output was energizedManual
Outside T FailOutdoor air temperature sensor (connected to CSC) failedAuto
Decouple T FailDecoupler temperature sensor failedAuto
Ret ChW T FailCommon return chilled water temperature sensor failedAuto
Sup ChW T FailCommon supply chilled water temperature sensor failedAuto
ChW Press FailChilled water loop differential pressure sensor failedAuto
WarningClg Tower FailCooling tower partially or totally failedAuto
Lvg CndW T WarnCommon leaving condenser water temperature sensor failed while it was
Auto
not the cooling tower Control Temperature source
Ent CndW T WarnCommon entering condenser water temperature sensor failed while it
Auto
was not the cooling tower Control Temperature source
Chiller OfflineAt least one chiller that is part of the current stage (1) is not running, (2)
Auto
is running under local control, or (3) has lost communications with the
CSC
Displaying Alarms
Variable NameKeypad(Menu-Scr.)
Current CSC Alarm31-1
Current Chiller #
Buffer Alarm #
Notes:
1. The wildcard character (
2. The wildcard character (
>
Alarm Type
>
|
Current Alarms
When the CSC indicates that an alarm has occurred, you can find out what it is and when it happened
by displaying the current alarms at the keypad or PC. For CSC alarms, the specific alarm is displayed;
for chiller alarms, the affected chiller and the alarm type (Fault, Problem, or Warning) is displayed.
You can find out what specific chiller alarm occurred by going to the chiller’s keypad/display or to
the chiller’s alarm screen on a PC equipped with the Monitor program.
A current CSC alarm is displayed until either it clears (see below) or another alarm with higher
priority occurs. Thus if a situation arises in which two or more CSC alarms exist at the same time, the
Current CSC Alarm variable displays the alarm that has the highest priority. The CSC alarms shown
in Table 45 are listed in order of priority. For example, the “No Comm Chil #1” alarm has higher
priority than the “Chiller Offline” alarm.
CSC Alarm History
When the current CSC alarm is cleared or replaced by another alarm, it is stored in the CSC Alarm
Buffer (menu 32), which holds the last nine CSC alarms. Each alarm’s time and date of occurrence is
also stored. Buffer Alarm #1 is the most recent alarm.
{
31-1 to -3
32-1 to -3
>
) could be 1 through 12.
>
) could be 1 through 12.
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Clearing Alarms
Before an alarm can be cleared, the alarm conditions that caused it must be returned to normal. When
the alarm conditions are gone, an alarm may be cleared either automatically or manually. Table 45
shows how CSC alarms are cleared.
An auto-reset alarm immediately clears when the alarm conditions that caused it returns to normal.
You can clear a manual-reset alarm at the affected controller’s keypad/display (see below) or a PC.
You cannot clear a chiller alarm from the CSC’s keypad/display.
Note:
Some of the chiller safety devices that detect alarm conditions require a manual reset at the
device before the controller alarm can clear.
To clear a CSC alarm from the keypad/display
ALARM
1. Press the
2. Press the
key. The current CSC alarm is displayed.
CLEAR
key. The alarm condition must be removed before the alarm clears.
To clear a chiller alarm from the keypad/display
1. Go to the affected chiller.
2. Press the
FAULT
key.) The alarm condition must be removed before the alarm clears.
CLEAR
key while the current alarm is in the display. (On Centrif-100, it’s the
CLEAR
Setting Up the Alarm Horn
Variable NameKeypad (Menu-Scr.)
Horn On Comm Loss Flag33-1
Horn On Fault Flag33-1
Horn On Problem Flag33-1
Horn On Warning Flag33-1
The CSC has a piezo alarm annunciator (Alarm Horn) that you can set to sound whenever an alarm
occurs anywhere in the chiller system. You can enable the Alarm Horn to sound only when certain
types of alarms occur—or you can disable it completely. For example, if you want the horn to sound
when a Fault alarm occurs in the CSC or any chiller, set the Horn On Fault Flag to “Horn.”
Setting Up the Alarm Output
Variable NameKeypad(Menu-Scr.)
Alarm Output Normal State34-1
Alarm Output Comm Loss State34-1
Alarm Output Fault State34-1
Alarm Output Problem State34-1
Alarm Output Warning State34-1
The CSC’s Alarm Output can be set up in a variety of ways to accommodate devices such as building
automation systems, remote annunciators, or dial-out notification systems. Like the Alarm Horn, the
Alarm Output can be set up to change state only when certain types of alarms occur. Four alarm state
options are available for each alarm type: open, closed, slow pulse (0.5 second on; 0.5 second off),
and fast pulse (0.1 second on; 0.1 second off).
The Alarm Output Normal State variable specifies the state of the alarm output when there are no
current CSC or chiller alarms. The other four variables shown above specify the state of the Alarm
Output when a current CSC or chiller alarm of that type exists. If multiple alarms exist, the output
state is the one specified for the highest priority alarm. If you don’t want any indication for a certain
alarm type, set its alarm state variable to the same value as the Alarm Output Normal State variable.
OM127-171
As an example, assume that the Alarm Output is connected to a building automation system that
requires a constant-state (non-pulsed) input. The Alarm Output must be normally closed, and
Warning alarms need not be reported. The following settings would produce the desired result:
Alarm OutputSetting
Normal StateClosed
Comm Loss StateOpen
Fault StateOpen
Problem StateOpen
Warning StateClosed
72OM127-1
Description of Operation
The following sections describe how the various CSC control processes work to manage chiller
system operation. The adjustable variables that affect these control processes are listed at the
beginning of each applicable sub-section. Before changing any control variables, you should read and
understand the applicable text.
Chiller Sequencing Control
As the cooling load varies, the CSC enables and disables chillers so that the current cooling capacity
is matched to the current cooling load. This action is commonly called chiller sequencing. The two
fundamental elements of any sequencing control strategy are the sequence order, the order in which
chillers are enabled and disabled, and the sequencing logic, the rules by which chillers are enabled
and disabled to match the cooling capacity to the load.
Sequencing and Staging
In the CSC, a chiller stage is defined as a set of chillers. As the CSC sequences chillers on and off, it
“stages up” and “stages down.” If the sequence order is set properly, each successive stage has more
capacity than the preceding stage. Additional capacity could be in the form of one added chiller
(typical), two or more added chillers, a chiller swap (in which the replacement chiller has more
capacity than the one that is stopped), or any combination of these. Thus the words “sequencing” and
“staging” essentially mean the same thing.
Sequence Order
Variable NameKeypad (Menu-Scr.)
Chiller Sequence Order Option11-1
First On Chiller11-2
Last On Chiller11-2
Chiller Resequence Day/Time11-3
Number Of Chiller Stages11-4
Chiller Stage > Bitset13-1 to -3
The wildcard character (
Note:
You can set the chiller sequence order automatically or manually. You select the method with the
Chiller Sequence Order Option variable. There are two options: Automatic and Fixed. Regardless of
the method used, the sequence order is contained in a stage table.
Understanding the Stage Table
Table 46 is an example of a stage table for a typical chiller system. At the keypad/display, the stage
table is shown at menu 13. Each Chiller Stage
You can determine the sequence order by comparing the contents of each stage with the previous
stage, starting at stage 1. Any chillers in stage 1 are lead; any new chillers in stage 2 (compared to
stage 1) are next in the sequence order; any new chillers in stage 3 (compared to stage 2) are next in
the sequence order; and so on.
Table 46. Example of Chiller Stage Table
>
) could be 1 through 12.
>
Bitset variable (1 through 12) is a row of the table.
Chiller
Stage No.#1#2#3#4#5#6#7#8#9#10#11#12
Stage 1–––
Stage 2––––
Stage 3––
OM127-173
#3
––––––––
#4
–––––––
#5
–#5–––––––
Chiller
Stage No.#1#2#3#4#5#6#7#8#9#10#11#12
Stage 4–
Stage 5–#2#3–#5
Stage 6
Stage 7––––––––––––
Stage 8––––––––––––
Stage 9––––––––––––
Stage 10––––––––––––
Stage 11––––––––––––
Stage 12––––––––––––
#1
#3–#5–––––––
#2
––––––
#6
#2#3–#5#6––––––
The advantage of the stage table is that it is flexible enough to allow for unusual sequences; for
example, chillers can be turned off when a stage-up occurs, chillers can be turned on when a stagedown occurs, and more than one chiller can be started or stopped for a single stage change.
Consider the stage table shown in Table 46. Notice that this system has six chillers and six stages.
Assume that Chiller #4 is a reciprocating chiller, and the other chillers are centrifugals. By comparing
rows, you can see that this system’s sequence order is as follows (“new” chillers are shown in bold
italic):
1. Chiller #4
2. Chiller #5 (Chiller #4 also goes off)
3. Chiller #3
4. Chiller #2
5. Chiller #6
6. Chiller #1
Chiller #4, which has much less capacity than any of the centrifugal chillers, is used only when the
cooling load is extremely light.
Stage Table Changes:
The CSC actually maintains two chiller stage tables in its memory. One is the
active stage table, and the other is the ideal stage table. While the CSC is operational, it uses only the
active stage table. Any changes to the sequence order—whether entered manually by an operator or
automatically by the CSC—are stored in the ideal stage table. A new sequence is implemented when
the ideal stage table is copied over the existing active stage table. Until this happens, any changes tothe sequence order are used as the CSC sequences its chillers. There are two methods of
implementing a new sequence order: natural and forced.
Note:
The stage table of menu 13 is the ideal stage table. The active stage table is not shown on the
keypad/ display.
Automatic Sequence Order Option
With the Automatic sequence order option, the CSC modifies the stage table as required to equalize
each chiller’s run time. Chillers that have less run time are placed before chillers that have more run
time in the sequence order. As changes occur, the CSC stores them in the ideal stage table.
For centrifugal chillers, run time is totaled when the compressor is on. For reciprocating and screw
chillers, run time is totaled when at least one compressor is on. Once every 15 minutes, the CSC reads
the run time values from each chiller controller, which totals and stores them. At the keypad/display,
you can find each chiller’s run time under menu 4.
To use the Automatic option, your sequencing strategy must have the following characteristics:
• The number of stages must be equal to the number of chillers.
• Each chiller must be able to assume any place in the sequence order—with two exceptions:
a. one chiller can be designated as always “first on” (lead), and
74OM127-1
b. one chiller can be designated as always “last on” (most lag). See below.
• A stage-up must enable one chiller, and a stage-down must disable one chiller.
• If both a first-on and a last-on chiller are designated, they must be different chillers.
Designating a First-On Chiller:
With the First On Chiller variable, you can designate one chiller
that is always lead regardless of its run time. You can also specify whether this chiller goes off at
stage 2 and higher (“Off at Stage Two”) or stay on at stage 2 and higher (“Off Last”). The first-on
chiller is always the only chiller in stage 1. For example, the sequence order shown in Table 46 could
be set up by designating Chiller #4 as “First On & Off at Stage Two.”
Designating a Last-On Chiller:
With the Last On Chiller variable, you can designate one chiller that
is always most lag regardless of its run time. The last-on chiller is always placed only in the highest
stage. If a stage-down occurs while the CSC is at the highest stage, the last-on chiller is always the
first chiller to be turned off. For example, in the sequence order shown in Table 46, Chiller #1 would
never occur in stages 1 through 5 if it were designated as “Last On & First Off.”
Note:
When the Automatic option is used, the following variables are set by the CSC: Number Of
Chiller Stages, Chiller Stage > Bitset (1 through 12). The CSC does not allow you to change them.
To set up the Automatic sequence order option
1. Set the Chiller Sequence Order Option to “Automatic.”
2. If one of the chillers will always be lead, set the First On Chiller variable as required.
Note that in addition to the chiller’s number, you must also specify when the first-on chiller goes
off (“at Stage Two” or “Last”).
3. If one of the chillers is always most lag, set the Last On Chiller variable as required.
Fixed Sequence Order Option
With the Fixed sequence order option, you can manually enter the sequence order into the ideal stage
table. Once the fixed sequence order is implemented, the CSC uses it until you change it.
The Fixed option is very flexible. It allows you to set up sequencing strategies that (1) have an
unequal number of chillers and stages or (2) turn multiple chillers on or off at any stage change.
Note:
The variables First On Chiller and Last On Chiller are not used with the Fixed option:.
To set up the Fixed sequence order option
1. Set the Chiller Sequence Order Option to “Fixed.”
2. Set the Number Of Chiller Stages variable to the number of stages the stage table has.
In a typical system, this number equals the number of chillers.
3. Set up the ideal stage table by setting the Chiller Stage
>
Bitset variables (1 through x, where x is
the number of stages specified in step 2).
Natural Sequence Order Implementation
Natural sequence order implementation automatically occurs when the CSC is in an Off operating
state. Because all chillers are disabled during the Off state, this method allows the active stage table to
change without disabling one chiller in order to enable another chiller. For a chiller system in which
all chillers are shut down daily, a new sequence is implemented within 24 hours (at most).
Forced Sequence Order Implementation
With the Chiller Resequence Day/Time variable, you can force a new sequence order to go into effect
either immediately or at a scheduled time on a scheduled day. You can choose any day of the week,
every day, or holidays. The following selections are possible:
• Now
• Daily, any time
• Sunday, any time
OM127-175
• Monday, any time
• Tuesday, any time
• Wednesday, any time
• Thursday, any time
• Friday, any time
• Saturday, any time
• Holidays, any time
If you set the Chiller Resequence Day/Time variable’s day setting to “Hol,” the forced sequence order
implementation occurs when a scheduled CSC holiday occurs. In this way you can customize the
sequence order change schedule to make it, for example, biweekly, monthly, or quarterly. You can
disable the scheduled sequence order change feature by setting the Chiller Resequence Day/Time
variable to “N/A 0:00” (default).
When you enter “Now” or when the current day and time match the Chiller Resequence Day/Time
variable’s setting, the following occurs regardless of the CSC’s operating state:
1. The active stage table is updated.
2. The Current Chiller Stage (menu 1) remains the same—except when there is an operational
standby chiller.
3. Disabled, available chillers that are part of the current (updated) stage are enabled. (The chiller
status of these available-but-disabled chillers is Off:CSC.)
4. Chillers in the current (updated) stage that were already on remain on with no interruption.
5. Enabled chillers that are no longer part of the current (updated) stage are disabled.
6. Locally disabled chillers that are part of the current (updated) stage remain disabled. (The CSC
does not attempt to enable them.)
In a typical situation, the same number of chillers that were enabled before the resequence time are
enabled after the resequence time. However, as described above, the CSC may simultaneously enableand disable chillers to satisfy a new sequence order when the resequence time occurs. If enabled and
disabled chillers trade positions, a temporary loss of capacity occurs while the new chiller loads up.
Because of this, you should only use forced sequence order implementation if your chiller system
seldom or never shuts down.
Restoring Offline Chillers:
In addition to forced sequence order implementation, the resequence
day/time function can be used to return the CSC and offline chillers to normal operation when the
Chiller Offline alarm exists. In this case, it is likely that more chillers are enabled after the resequence
time than were enabled before it even though the current chiller stage remains the same.
Note:
The Chiller Resequence Day/Time variable’s setting is always compared with the day and time
on the CSC’s internal clock. Therefore, if you are using a Network Master Panel (NMP) to schedule
chiller system operation and you want to schedule a forced sequence order implementation on a
“holiday,” you must set that holiday date in the CSC (menu 25).
Normal Sequencing Logic
Variable NameKeypad(Menu-Scr.)
Chiller Sequencing Control Type11-1
Chiller Stage-Up Differential11-4
Decoupler Stage-Up Temperature Differential11-5
Decoupler Stage-Down Flow Rate Factor11-5
Chiller Stage 1 Stage-Up Setpoint12-1
Chiller Stage 1 Delay Time12-1
Chiller Stage > Stage-Up Setpoint
Chiller Stage > Stage-Down Setpoint
76OM127-1
{
{
12-2 to -9
12-2 to -9
Variable NameKeypad(Menu-Scr.)
Chiller Stage > Delay Time
Chiller # > Flow Rate
Notes:
1. The wildcard character (
2. The wildcard character (
{
|
>
) could be 2 through 12.
>
) could be 1 through 12.
12-2 to -9
29-1 to -4
The CSC’s chiller sequencing logic determines when chillers must be enabled or disabled to increase
or decrease capacity. The term “stage up” means to increase capacity by one step (typically by
enabling one chiller), and the term “stage down” means to decrease capacity by one step (typically by
disabling one chiller). (If there are reciprocating or screw chillers in your chiller system, do not
confuse compressor staging with chiller staging.)
Two types of sequencing logic are available: Standard and Decoupled. You can select the type
suitable for your system with the Chiller Sequencing Control Type variable.
Start-Up Control
When the chiller system starts, the CSC’s operating state changes from Off to Recirculate. If there is a
secondary pump, the CSC proves that chilled water flow in the secondary loop exists before leaving
Recirculate and going to the On state.
Upon entering the On state, the CSC enables the stage-1 chiller. (Assume there is only one chiller in
stage 1 and that it is available.) Once the stage-1 chiller is enabled, its controller starts the primary
chilled water pump, checks for evaporator water flow, and checks for a cooling load. The chiller
starts if there is flow and the leaving evaporator water temperature is greater than the Active Setpoint
by more than a differential, which varies and depends on the chiller type.
After the stage-1 chiller starts, its controller increases cooling capacity as required, but only within
the constraints of an active maximum pull down rate control and soft loading control. Any active
maximum pull down rate or soft loading control in the stage-1 chiller can limit the chiller’s capacity
and thus may delay chiller sequencing (see below).
Standard Sequencing Logic
Standard sequencing logic is intended for primary-only chiller systems. A typical primary-only system
is shown in Figure 14. The distinguishing characteristic is that the primary pumps distribute water to
the cooling loads. (The primary pump and evaporator piping arrangements are not distinguishing
characteristics. Dedicated primary pumps and parallel evaporators are shown in Figure 14, but a
common primary pump and series evaporators are also possible.)
Figure 14. Typical Primary-Only System
Cooling Loads
Optional pressure-controlled loop bypass
Differential pressure transducer
DPT
Chilled water supply temperature
Primary pump
Chiller #1
% Load
Chiller #2
% Load
a0141
OM127-177
Standard sequencing logic uses each chiller’s percent load and the chilled water supply temperature to
stage the chillers.
Stage-Up Control:
The CSC stages up when additional cooling capacity is required. This occurs
when the following three conditions are satisfied:
1. The average percent load of all operational chillers is greater than the Chiller Stage x Stage-Up
Setpoint, where x is the current chiller stage (1 through 12).
2. The chilled water supply temperature is greater than the System Setpoint (menu 1 and 16) by
more than the Chiller Stage-Up Differential.
3. Conditions 1 and 2 above have been true for a period of time specified by the Chiller Stage
x
Delay Time variable, where x is the current chiller stage.
Stage-Down Control:
The CSC stages down when there is an excess of cooling capacity. This occurs
when the following three conditions are satisfied:
1. At least one chiller in next lower stage is available. (A chiller is available when it is
communicating and it is not locally disabled or locally enabled.)
2. The average percent load of all operational chillers is less than the Chiller Stage x Stage-Down
Setpoint, where x is the current chiller stage (2 through 9).
3. Condition 2 above has been true for a period of time specified by the Chiller Stage x Delay Time
variable, where x is the current chiller stage.
To set up Standard sequencing logic
1. Set the Chiller Sequencing Control Type variable to “Standard.”
2. Set the Chiller Stage-Up Differential as required.
3. Set the Chiller Stage
>
Stage-Up Setpoint variables (1 through x, where x is the number of stages
in the stage table) as required.
4. Set the Chiller Stage
>
Stage-Down Setpoint variables (2 through x, where x is the number of
stages in the stage table) as required.
5. Set the Chiller Stage
>
Delay Time variables (1 through x, where x is the number of stages in the
stage table) as required.
Note:
To use Standard sequencing logic, a chilled water supply temperature sensor must be
connected to the CSC. For more information, see the “Field Wiring” section of Bulletin No. IM 618.
Decoupled Sequencing Logic
Decoupled sequencing logic is intended for use with primary-secondary chiller systems. A typical
primary-secondary system is shown in Figure 15. The distinguishing characteristics of this system are:
(1) each chiller (or set of series chillers) has its own primary pump, (2) one or more secondary pumps
distribute water to the cooling loads, and (3) the secondary circuit is hydraulically isolated from the
primary circuit by a decoupler line. (Evaporator piping arrangements are not distinguishing
characteristics. Parallel evaporators are shown in the figure, but series evaporators are also possible.)
The purpose of primary-secondary (decoupled) systems is to maintain relatively constant flow
through the chillers while at the same time allowing variable flow to the cooling loads. Because the
relationship between a building’s total cooling load and its required chilled water flow rate is seldom
proportional, situations can occur in which partly loaded chillers cannot provide enough chilled water
to the secondary loop. In this instance, water flows from return to supply in the decoupler line. As a
result, supply and return water mix, and the chilled water temperature going to the cooling loads rises.
The CSC’s Decoupled sequencing logic can prevent this from happening.
Decoupled sequencing logic uses each chiller’s percent load, the chilled water supply temperature, the
decoupler line temperature, and the decoupler line flow rate (supply to return only) to stage the
chillers. A stage-up can occur for either of two reasons: (1) to satisfy the need for additional capacity,
or (2) to satisfy the need for additional flow.
78OM127-1
Figure 15. Typical Primary-Secondary System
Cooling Loads
Uni-directional flow meter
(supply to return)
FM
Decoupler line temperature
Chilled water supply temperature
Primary pump
Chiller #1
% Load
Chiller #2
% Load
Secondary pump
a0142
Stage-Up-for-Capacity Control:
The CSC stages up when additional cooling capacity is required.
This occurs when the following three conditions are satisfied:
1. The average percent load of all operational chillers is greater than the Chiller Stage x Stage-Up
Setpoint, where x is the current chiller stage (1 through 12).
2. The chilled water supply temperature is greater than the System Setpoint (menu 1 and 16) by
more than the Chiller Stage-Up Differential.
3. Conditions 1 and 2 above have been true for a period of time specified by the Chiller Stage
x
Delay Time variable, where x is the current chiller stage.
Stage-Up-for-Flow Control:
The CSC stages up when additional primary water flow is required.
This occurs when the following two conditions are satisfied:
1. The decoupler line temperature is greater than the chilled water supply temperature by more than
the Decoupler Stage-Up Temperature Differential. (Water is flowing the wrong way through the
decoupler line.)
2. Condition 1 above has been true for a period of time specified by the Chiller Stage x Delay Time
variable, where x is the current chiller stage.
Stage-Down Control:
The CSC stages down when there is an excess of cooling capacity and
primary chilled water. This occurs when the following four conditions are satisfied:
1. At least one chiller in next lower stage is available. (A chiller is available when it is
communicating and it is not locally disabled or locally enabled.)
2. The average percent load of all operational chillers is less than the Chiller Stage x Stage-Down
Setpoint, where x is the current chiller stage (2 through 12).
3. The decoupler line flow rate is greater than an adjustable percentage of the defined flow rate of
the chiller(s) to be disabled. The chiller flow rates are defined with the Chiller #
>
Flow Rate
variables, and the percentage is defined with the Decoupler Stage-Down Flow Rate Factor.
4. Conditions 2 and 3 above have been true for a period of time specified by the Chiller Stage
x
Delay Time variable, where x is the current chiller stage.
OM127-179
Condition 3 assures that the chillers that would still be on after a stage-down continues to meet the
building’s flow requirement. As an example, consider a system in which Chiller #3 is the only chiller
that is part of stage 2 and not part of stage 1. Assume that Chiller #3’s defined flow rate is 1000 gpm
(50 L/s) and that the Decoupler Stage-Down Flow Rate Factor is set to 1.10. If the CSC is at stage 2
and the decoupler line flow rate is slightly more than 1100 gpm (55 L/s), condition 3 is satisfied. If
the stage down occurs, the flow rate from supply to return in the decoupler line drops from 1100 gpm
(55 L/s) to 100 gpm (5 L/s).
To set up Decoupled sequencing logic
1. Set the Chiller Sequencing Control Type variable to “Decoupled.”
Stage-Up Setpoint variables (1 through x, where x is the number of stages
in the stage table) as required.
5.Set the Chiller Stage
>
Stage-Down Setpoint variables (2 through x, where x is the number of
stages in the stage table) as required.
6.Set the Chiller Stage
>
Delay Time variables (1 through x, where x is the number of stages in the
stage table) as required.
7.Set the Chiller #
>
Flow Rate variables (1 through x, where x is the number of chillers) as
required.
Note:
To use Decoupled sequencing logic, a chilled water supply temperature sensor, a decoupler
line temperature sensor, and a uni-directional decoupler line flow meter must be connected to the
CSC. For more information, see the “Field Wiring” section of Bulletin No. IM 618.
Special Sequencing Logic
Variable NameKeypad (Menu-Scr.)
Chiller Resequence Day/Time11-3
The CSC uses special sequencing logic to compensate for a chiller that (1) is part of the current stage
and (2) cannot be enabled or disabled by the CSC. Such a chiller is called an offline chiller. An
offline chiller must be compensated for because it represents a significant loss of capacity for the
current stage. For example, if stage 2 consists of two equally sized chillers and one of them is offline,
stage 2’s capacity is reduced by 50 percent.
Special sequencing logic is similar to normal sequencing logic; the basic differences are that (1)
forced stage-ups can occur and (2) normal stage-downs are allowed at lower-than-normal average
percent load levels. The overall effect is to make it easier to add capacity and more difficult to shed
capacity. Although special sequencing logic usually keeps the chiller system operating with no
adverse effects, it is not an ideal situation—especially if multiple chillers are offline at the same time.
Therefore, the CSC generates the Chiller Offline alarm to alert you that the system may need
attention. See “Restoring Offline Chillers to Normal Operation” below for more information.
Unavailable and Available Chillers
Before a chiller is marked offline, it must first be unavailable. A chiller is unavailable when the CSC
cannot influence its start/stop operation. This can occur for any of three reasons:
1. The chiller is locally disabled.
The chiller status (menu 3) of a locally disabled chiller is always Off:Local. If a chiller is locally
disabled, it is always off. For more information on locally disabled chillers, see “Chiller Status
(Generalized Operating State)” in the “Determining Chiller System Status” section and “Local
Override” in the “Auto/Manual Operation” section.
2. The chiller is locally enabled.
80OM127-1
If a chiller is locally enabled, it is usually on, but it may also be off if it is locally disabled at the
same time. If a locally enabled chiller is part of the current stage, it is not possible to tell whether
it is locally enabled from information available at the CSC’s keypad/display. However, since a
chiller can become locally enabled only as a result of a manual override, the system operator
knows which chillers are locally enabled. For more information on locally enabled chillers, see
“Local Override” in the “Auto/Manual Operation” section.
3.The chiller has lost communications with the CSC.
The chiller status (menu 3) of a chiller that has lost communications with the CSC is always
Comm Loss. Such a chiller may be on or off; the CSC has no way of knowing.
Conversely, a chiller is available when none of the above conditions apply to it.
New Offline Chillers and Forced Stage-Ups
A normal chiller becomes an offline chiller when it is part of the current stage but is unavailable.
Whenever the CSC finds an offline chiller, it marks the chiller, disables the chiller, and usually forces
a stage-up (see below). The chiller is marked so that it does not force another stage-up at a different
stage, and it is disabled so that it won’t start if the condition that caused it to go offline is removed
(this would result in an excess of system capacity).
Once a chiller is marked offline, it remains offline until certain conditions are satisfied. An offline
chiller that becomes available again (Off:CSC chiller status) does not automatically lose its offline
marking and start up. See “Restoring Offline Chillers to Normal Operation” for more information.
There are three situations in which the CSC can find a new offline chiller:
1. At stage-up
2. At stage-down
3. During steady-state operation
In situations 1 and 3, a forced stage-up occurs.
Offline at Stage-Up:
As a stage-up occurs, the CSC checks the availability of each chiller in the new
stage. If it finds a new unavailable chiller, it marks the chiller as offline and forces another stage-up.
(If it finds a chiller that had been marked offline, it does nothing.) For example, if a stage-up from
stage 1 to stage 2 occurs and the CSC finds a locally disabled chiller in stage 2 that is not part of stage
1, the CSC marks the chiller as offline and immediately goes to stage 3.
Offline at Stage-Down:
As a stage-down occurs, the CSC checks the availability of each chiller in
the new stage. If it finds a new unavailable chiller, it marks the chiller as offline. Because it is a stagedown, no forced staging (up or down) occurs. For example, if a stage-down from stage 3 to stage 2
occurs and the CSC finds a locally disabled chiller in stage 2 that is not part of stage 3, the CSC
marks the chiller as offline.
Offline During Steady-State:
During the first 60 seconds after any stage change, the CSC ignores
each chiller’s chiller status. If the CSC finds a new unavailable chiller anytime after this period, it
marks it as offline and forces a stage-up. For example, if the CSC has been at stage 2 for more than 60
seconds and a chiller that is part of stage 2 suddenly loses communications, the CSC marks the chiller
as offline and immediately go to stage 3.
Note:
In the case of an operational chiller that loses communications, a forced stage-up could result
in an excess of capacity until communications are restored because an enabled chiller that loses
communications with the CSC remains enabled. When communications are restored with such a
chiller, it is shut down by the CSC since it is marked as offline.
How Offline Chillers Affect Normal Stage-Down Logic
Any time an offline chiller exists, the CSC ignores the Chiller Stage
>
Stage-Down Setpoint variables.
Instead of the set variables, it uses a value of 0% at stage 2, and it uses the Chiller Stage 2 StageDown Setpoint at stage 3 through 9. This is done because these variables depend on capacity, and
when a chiller is offline, there is likely a significant reduction in capacity for any current stage.
OM127-181
As an example, consider a chiller system that has three 400 ton centrifugal chillers. Stage 1 is one
chiller; stage 2 is two chillers; and stage 3 is three chillers. The Chiller Stage 2 Stage-Down Setpoint
is 50%, and the Chiller Stage 3 Stage-Down Setpoint is 67%.
Normal Logic:
During normal operation, a stage-down from stage 3 to stage 2 occurs when the three
chillers are operating at an average load of 66% or less. The 67% setting is used for stage 3 because
the capacity of three chillers operating at two-thirds load is approximately equal to the capacity of two
chillers operating at full load.
Special Logic:
If the stage-1 chiller is offline, a stage-down from stage 3 to stage 2 should not occur
at the same stage-3 setpoint because the capacity of two chillers operating at two-thirds load is greater
than the capacity of one chiller operating at full load. However, if stage 2’s lower setting of 50% is
used for stage 3, the stage-down can safely occur because the capacity of two chillers operating at
one-half load is approximately equal to the capacity of one chiller operating at full load.
Restoring Offline Chillers to Normal Operation
When all offline chillers are unmarked, the Chiller Offline alarm clears and normal sequencing
resumes. The CSC unmarks an offline chiller when any of the following situations occur:
1. The CSC’s operating state changes to Off (chiller system shutdown).
Like natural sequence order implementation, restoration of offline chillers automatically occurs
whenever the CSC is in any Off operating state. For a typical chiller system in which all chillers
are shut down daily, any offline, available chillers are restored to normal operation within
24 hours (at most).
2. The chiller is no longer part of the current stage.
Regardless of whether a stage-up or stage-down occurs, an offline chiller is unmarked if it is not
part of the new stage. Since the chiller’s capacity is not required (it is not part of the stage), it
remains disabled after it is unmarked. If there are no offline chillers in the new stage, there is no
missing capacity and thus normal sequencing logic can safely resume.
3. The chiller is available, the current stage is the highest stage, and more capacity is required.
If a normal stage-up condition occurs while the current stage is the highest stage, the CSC checks
for offline chillers that are also available. If it finds one, it automatically unmarks and enables it.
If there are two or more offline, available chillers, the CSC unmarks and enables the one that has
the lowest chiller number and then resets the stage-up timer. If another stage-up condition occurs,
the chiller with the next lowest number is unmarked and enabled. For example, if Chiller #1 and
Chiller #3 are both offline and available, the CSC unmarks and enables Chiller #1 first.
Note:
This logic does not occur when a standby chiller is designated. See “Designating a
Standby Chiller” below for more information.
4. The chiller is available and a resequence time occurs.
With the Chiller Resequence Day/Time variable, you can force the CSC to unmark and enable all
offline chillers that are also available. To do this, set the variable to “Now.” (You can also
schedule the resequence time.) If there are multiple offline chillers, be aware that the sudden
increase in capacity may be very large.
Note:
If there is a standby chiller and the current stage is the highest stage, the resequence
day/time function forces a stage-down before it executes, disabling the standby chiller. See
“Designating a Standby Chiller” below for more information.
Caution:
A forced sequence order implementation also occurs when the resequence day/time
function executes. If the ideal stage table changed, some chillers may stop while others start. For
more information, see the “Sequence Order” sub-section above.
82OM127-1
Notice that offline chillers are unmarked in situations 3 and 4 only if they are available. This is
because an offline chiller’s capacity is required in these two situations. An offline chiller becomes
available again when the condition that caused the chiller to be unavailable is removed. For example,
if a chiller has a Fault alarm, the alarm must be cleared; if a chiller’s remote stop switch input is
opened, the input must be closed again; if a chiller is locally enabled, it must be returned to automatic
(network) control; if a chiller loses communications, communications must be restored.
An offline chiller that is available has a chiller status (menu 3) of Off:CSC. This chiller status
indicates that the only thing disabling the chiller is the CSC. If an offline chiller is running when it
becomes available again, it stops. This situation could occur, for example, when communications are
restored or when a series-200 chiller’s control mode is changed from “Manual Enable” to
“Auto:Network.”
To manually restore offline chillers to normal operation
1. Verify that the offline chiller(s) you want to run are available.
The chiller status (menu 3) of an offline chiller that is available is Off:CSC.
2. Set the Chiller Resequence Day/Time variable to “Now.”
After you enter the value, it automatically changes back to “N/A.” Note that this causes a forced
sequence order implementation.
The CSC enables all available chillers in the current stage.
Designating a Standby Chiller
Variable NameKeypad(Menu-Scr.)
Standby Chiller11-2
Regardless of whether you’re using Automatic or Fixed sequence ordering, you can designate one
chiller as a standby chiller with the Standby Chiller variable. If you designate a standby chiller, the
CSC does not allow it to operate unless at least one other chiller is offline. It does this by (1) forcing
the standby chiller to exist only in the highest stage and (2) disallowing a stage-up to the highest stage
unless a chiller is offline. Notice that when you designate a standby chiller, the highest stage of the
stage table effectively becomes a “standby stage.”
If you’re using Fixed sequence ordering, the CSC automatically removes the standby chiller from all
but the last stage of the ideal stage table. If you’re using Automatic sequence ordering, the CSC
automatically sets the Last On Chiller variable (menu 11) equal to the Standby Chiller variable, which
has the same effect.
Caution:
An offline chiller may be operational if it becomes unavailable as a result of (1) losing
communications with the CSC or (2) being locally enabled. In these instances, the standby chiller
could start, making possible a situation in which all chillers are running at the same time.
Standby Chillers and Special Sequencing Logic
It is assumed that when a standby chiller is designated, a situation in which all chillers are operating at
the same time is undesirable—though still possible since offline chillers are not necessarily off (see
caution above). Therefore, special sequencing logic is modified in two ways when there is a standby
chiller:
1. Offline chillers that are also available are not enabled when the current stage is the standby
(highest) stage and more capacity is required.
Normally, more capacity is not required when the standby chiller is on unless two or more
chillers are offline.
2. The resequence day/time function forces a stage-down if it executes while the current stage is the
standby (highest) stage.
The stage-down turns off the standby chiller, and any offline chillers in the new stage that are
also available start.
OM127-183
To designate a standby chiller
• Set the Standby Chiller variable as required. If you do not want a standby chiller, set it to “NA.”
Load Limiting Control
Load Balancing
Variable NameKeypad (Menu-Scr.)
Load Balancing Flag14-1
Load Balancing Capacity Difference Limit14-1
The CSC can provide load balancing control for all centrifugal chillers in the system. If you choose to
use load balancing control, it affects the entire system.
When to Use Load Balancing
Load balancing control is required if there is at least one dual-compressor centrifugal chiller in the
system. It is often used (but not required) when there is at least one set of series-piped centrifugal
chillers in the system.
If all the centrifugal chillers have single compressors and are piped in parallel, load balancing control
is optional. As long as their leaving evaporator water temperature setpoints are the same, chillers in
these systems tend to automatically balance their loads as they control their chilled water
temperatures. In fact, load balancing control can actually override chilled water temperature control.
So if load balancing control is in use, you can expect some variation in the chillers’ leaving
evaporator water temperatures. This is more likely to occur in a system that has chillers with a wide
range of efficiencies.
How Load Balancing Works
The CSC continually reads the percent load (% RLA) from each centrifugal compressor that is
running. It then selects the lowest of these percent load values and adds the Load Balancing Capacity
Difference Limit variable (default is 5%) to this minimum. The result is the System Load Balancing
Load Limit (menu 5). If this value is less than the capacity limits produced by the start-up unloading
and demand limiting functions, the CSC sends it to every centrifugal chiller. Each chiller then inhibits
loading or unloads as required to keep the load within 5% of this limit.
The Load Balancing Capacity Difference Limit effectively defines a range of acceptable compressor
percent load values. This range floats up and down as the minimum percent load value floats.
As an example, consider a system with two older, inefficient chillers and one new, efficient chiller.
The new chiller is Chiller #3, the CSC’s Load Balancing Capacity Difference Limit variable is set to
5%, and the chilled water setpoints in each chiller controller are the same. When Chiller #3’s load is
55% RLA, the load on Chiller #1 and Chiller #2 is prevented from exceeding 64% RLA. (Loading is
inhibited at 60% through 64%; unloading occurs at 65% and higher.)
To set up load balancing control
1. Set the Load Balancing Flag to “Yes.”
2. Set the Load Balancing Capacity Difference Limit as required.
Start-Up Unloading
Variable NameKeypad(Menu-Scr.)
Chiller # > Group15-1 to -2
The wildcard character (
Note:
>
) could be 1 through 12.
The CSC can provide start-up unloading control for defined groups of centrifugal chillers. Six groups
are possible, and a group can have 2 to 12 chillers. If you choose to use start-up unloading control, it
only affects groups in which a compressor is starting.
84OM127-1
When to Use Start-Up Unloading
Start-up unloading control is required for dual-compressor centrifugal chillers. Both compressors of a
particular chiller must be assigned to the same group so that if either one starts, the other unloads.
For single-compressor centrifugal chillers, start-up unloading control is optional. You may want to
use it, for example, if the primary chilled water flow to certain chillers is temporarily but significantly
reduced when another chiller starts up.
How Start-Up Unloading Works
When two or more chillers are assigned to a start-up unloading group, all chillers in the group unload
when any chiller in the group starts up. The CSC checks the chiller status of each chiller to find out
whether any of them are starting up. If at least one chiller status is Starting, the CSC sets the Start-Up
Unloading Group #x Load Limit variable (menu 5) to 30%, where x is the group that the starting
chiller is part of. The CSC then sends this 30% load limit to each chiller controller in that group. As a
result, all operational compressors in the group unload.
When all chillers in a group are no longer starting, the CSC sets the Start-Up Unloading Group #
x
Load Limit variable back to 100%, allowing normal operation to resume.
To set up start-up unloading control
• Assign the same group number to every chiller in the group with the Chiller #
>
Group variables.
Do this for each of the six groups as required.
For example, if Chiller #1 and Chiller #2 are two compressors of a dual-compressor chiller, set
the Chiller #1 Group and Chiller #2 Group variables to “1.” This results in Group 1 consisting of
these two chiller controllers.
Demand Limiting
Variable NameKeypad (Menu-Scr.)
Demand Limiting Type14-1
The CSC can provide demand limiting control for all chillers in the system. If you choose to use
demand limiting control, it affects the entire system.
How Demand Limiting Works
Demand limiting control requires a capacity limit value, which must come from an outside source.
You can choose one of two possible sources with the Demand Limiting Type variable:
• External (analog signal)
• Open Protocol (network BAS signal)
After receiving the capacity limit from either source, the CSC generates the System Demand Limiting
Load Limit (menu 5). If the value of this variable is less than the capacity limits produced by the load
balancing and start-up unloading functions, the CSC sends it to every centrifugal chiller controller in
the system. Each centrifugal chiller then inhibits loading or unloads as required to keep the load
within 5% of this limit. The CSC always sends the value to every reciprocating or screw chiller
controller in the system. After converting the percent-load limit to a maximum-stage limit, each
reciprocating or screw chiller inhibits stages ups down as required to keep the load at the limit.
Demand Limiting from an External Signal
If the Demand Limiting Type variable is set to “External,” the CSC uses an external voltage or
current signal as the source of the System Demand Limiting Load Limit. The capacity limit is
calculated according to the function shown in Figure 16.
OM127-185
Figure 16. External Signal Demand Limiting Function
100
80
60
Capacity Limit (% Load)
40
0–5 Vdc:
01235
0–10 Vdc:
0246108
0–20 mA:
048122016
External Signal
Demand Limiting via Open Protocol
If the Demand Limiting Type variable is set to “Open Protocol,” the CSC accepts a capacity limit
4
value sent by a building automation system (BAS) via Open Protocol. The value from the BAS
becomes the System Demand Limiting Load Limit; however, the CSC limits the value to a range of
40% to 100%. For example, if the BAS writes a value of 20%, the System Demand Limiting Load
Limit variable is set to 40%.
Note:
If communications are lost with a BAS that is supplying the demand limiting value, the CSC
retains and uses the last value it received for 10 minutes. After that, it automatically sets the System
Demand Limiting Load Limit variable to 100%.
Reciprocating and Screw Chillers
Since reciprocating and screw chillers control their capacity in stages, the System Demand Limiting
Load Limit cannot be used directly as it is in centrifugal chillers. Instead, each reciprocating or screw
chiller controller converts the percent-load capacity limit into a maximum-stage capacity limit. The
step functions these controllers use to do this are shown in Figure 14.
Figure 17. Recip-Standard, Screw, Recip-European, and AGU Chiller Demand Limiting
12
11
10
9
8
7
6
5
4
3
2
Capacity Limit (Compressor Stages)
1
0
40506070100
12-stage chillers
8-stage chillers
6-stage chillers
4-stage chillers
Capacity Limit (% Load)
80
90
a0143
86OM127-1
To set up demand limiting control
• Set the Demand Limiting Type variable as required. If you do not want demand limiting control,
set it to “None.”
Note:
To use an externally sourced demand limiting signal, an analog signal (0–5 Vdc, 0–10 Vdc, or
0–20 mA) must be connected to AI 9 on the CSC. For more information, see the “Field Wiring”
section of Bulletin No. IM 618.
Stage-Up Inhibiting
Variable NameKeypad(Menu-Scr.)
Inhibit Stage-Up After Time11-3
Stage-Up Inhibit Setpoint11-3
As its name implies, stage-up inhibiting limits loading by preventing further stage-ups. If stage-up
inhibiting is on, the CSC is able to stage down, but it is not able to stage up when a normal stage-up
would otherwise occur. If it is off, normal sequencing control occurs. Stage-up inhibiting does not
prevent a forced stage-up from occurring when the CSC finds a new offline chiller. (See “Special
Sequencing Logic” in the “Chiller Sequencing Control” section for more on offline chillers.)
Unlike load balancing, start-up unloading, and demand limiting, stage-up inhibiting does not directly
influence the loading of individual chillers, and it cannot actively reduce the system-wide load. It can
only prevent more capacity—in the form of additional chillers—from being added to the system.
There are two types of stage-up inhibiting:
• Daily
• Network
You can use either type or both types at the same time.
Daily Method
With the Inhibit Stage-Up After Time variable, you can specify a particular time after which no more
stage-ups occur. For example, if your chiller system shuts down at 9:00 p.m., you may want to
prevent more capacity from being added to the system after 8:15 p.m. In this instance, you could set
the Inhibit Stage-Up After Time to “20:15.”
Network Method
If your network includes a MicroTech Network Master Panel (NMP) or if a building automation
system (BAS) is connected to the CSC via Open Protocol, you can use the Stage-Up Inhibit Setpoint
to turn stage-up inhibiting on and off. Whenever the Stage-Up Inhibit Level (menu 9) is greater than
or equal to the setpoint, stage-up inhibiting is on; otherwise, it is off. The value of the level and the
setpoint can be whole numbers from 1 to 7. If the level or the setpoint is “None” (0), stage-up
inhibiting does not occur.
The NMP generates the Stage-Up Inhibit Level according to its load shed function and the input from
a demand meter.
A BAS can generate the Stage-Up Inhibit Level in any manner required.
Note:
If communications are lost with an NMP or BAS that is supplying the Stage-Up Inhibit Level,
the CSC retains and uses the last value it received for 10 minutes. After that, it disables Network
stage-up inhibiting.
To set up stage-up inhibiting control
1. Set the Inhibit Stage-Up After Time as required.
Normal stage-ups do not occur after this time.
2. Set the Stage-Up Inhibit Setpoint as required. If there is no NMP or BAS, set it to “None.”
OM127-187
Normal stage-ups do not occur when the Stage-Up Inhibit Level (menu 9) is greater than or equal
to this setpoint.
Soft Loading
Soft loading control can be used to prevent the lead chiller’s load from rising too fast during chiller
system start-up when the return chilled water temperature is high. Unlike the other load limiting
functions, soft loading control is performed by the individual chiller controllers, not the CSC.
However, the CSC does influence soft loading control by disabling it in all but the lead chiller. This
feature allows you to use soft loading control in conjunction with automatic sequence ordering.
How Soft Loading is Influenced by the CSC
Whenever a chiller starts up, the CSC checks to see whether any other chillers are already running. If
no other chillers are running, it does nothing, allowing soft loading to occur. If any other chiller is
running, it disables soft loading in all chillers.
The chiller in which the CSC allows soft loading is typically the single chiller in stage 1. If the stage-1
chiller fails or is disabled, the above logic allows the new chiller in stage 2 to start with soft loading.
The above logic may give undesired results with unusual sequence orders. For example, if stage 1 has
two chillers in it, soft loading does not occur. And if stage 1 and 2 both have one chiller each (a
chiller swap), soft loading occurs in both chillers when they start.
Chiller Controller Setup
If soft loading control is desired, the soft loading variables must be set in all chillers that may at some
time be the lead chiller. Typically, these variables are set identically in each chiller of the same type;
however, this is not required.
The soft load variables that must be set in each type of chiller are summarized in Tables 46, 47, and
48. The values shown in italic are typical settings.
Table 47. Soft Loading Variables: Centrif-200 and HallScrew
1. Determine which chillers may at some time be lead.
A lead chiller can be a stage-2 chiller that starts to replace the designated stage-1 chiller if it fails
or is locally disabled.
2. Set the soft loading variables as required. Refer to Tables 46, 47, and 48.
The CSC automatically disables soft loading control in all lag chillers when they start.
Chilled Water Temperature Control
In a system of multiple chillers, each individual chiller should normally maintain its leaving
evaporator water temperature at the same setpoint—even if that setpoint is being reset. The CSC can
generate this setpoint (with or without reset) and send it to every chiller in the system via network
communications.
Figures 18 and 19 show how leaving evaporator water temperature setpoints are generated and how
they flow to and through the chiller controllers, which ultimately use them to control capacity and
thus water temperature. Notice that the link between the CSC and the chiller controllers—and
between the two figures—is the Chiller Setpoint.
The discussion of the following sub-sections starts at the end of the flow chart (setpoint source at
chillers in Figure 18) and works back to the beginning (setpoint reset in Figure 19).
Setpoint Source at Chillers
In all cases, each individual chiller controller attempts to maintain its leaving evaporator water
temperature at its Active Setpoint, which is the “working” leaving evaporator water temperature
setpoint. Any capacity overrides that are in effect, such as load balancing or demand limiting, can
affect a chiller’s ability to control temperature. See Figure 18.
For almost all applications, the source of the Active Setpoint should be the CSC so that the same
setpoint is used throughout the system. Some unusual applications may require local setpoint
generation; for example, chillers piped in series that are not being load balanced.
Chiller Controller Setup
In all centrifugal chiller controllers, you can use the Setpoint Source variable to specify whether the
Active Setpoint comes from the CSC or the local controller. In reciprocating and screw chiller
controllers, the Active Setpoint must come from the CSC.
There are many other chiller controller variables that affect leaving evaporator water temperature and
load recycle control; for example, Start-Up Delta-T and Maximum Pull Down Rate. For more
information, refer to the appropriate MicroTech unit controller operation manual (see Table 2).
Centrif-200 and HallScrew Screw:
When the Setpoint Source variable is set to “Network,” the CSC
provides the working setpoint to the chiller. When the Setpoint Source variable is set to “Local,” the
chiller generates its own working setpoint. The series-200 centrifugal chiller controller has the ability
to revert to local control if communications have been lost for five minutes. So if you are using the
CSC as the chiller’s setpoint source, you may want to specify a local setpoint—and local reset if
desired—that would be used in such a case. Table 50 summarizes the local chilled water set-point
variables (excluding local reset variables). The values shown in italic are typical settings.
Table 50. Setpoint Variables: Centrif-200 and HallScrew
Keypad/Display ID
Chiller Controller VariableMenuItem
Setpoint Source12Spt Source= Network
Active Setpoint (status only)12Active Spt= 45.0°F
Local Setpoint12Local Spt= 44.0°F
OM127-189
Centrif-100:
When the Setpoint Source variable is set to “Remote,” the CSC provides the working
setpoint to the chiller. When the Setpoint Source variable is set to “Local,” the chiller generates its
own working setpoint. Table 51 summarizes the local chilled water setpoint variables (excluding local
reset variables). The values shown in italic are typical settings.
Table 51. Setpoint Variables: Centrif-100
Keypad/Display ID
Chiller Controller VariableKeyItem
Setpoint Source
Active Setpoint (status only)
Leaving Evaporator Setpoint
SET-UPOPTIONS
WATERTEMP’S
WATERTEMP’S
Spt Source= Remote
Active Spt= 45.0°F
Lvg Evap Spt= 44.0°F
Figure 18. Chiller Leaving Evaporator Water Temperature Flow Chart
CSC
Chiller Setpoint
Via network comm.
Chiller #1
Max Setpoint
Local Setpoint
Network Setpoint
Chiller #2
Max ChW Reset
Lvg Evap Spt
Chiller #3
Lvg Evap Spt
(series-200 centrifugal or J&E Hall screw
chiller shown)
Local Reset
Methods
Setpoint Source
Local
Network
Active Setpoint
(series-100 centrifugal shown)
Local Reset
Methods
Setpoint Source
Local
Remote
Active Setpoint
(recip-standard, screw, recip-Eupropean, or
AGU shown)
Local Reset
Methods
The local reset method must be
Note:
set to “None.”
Active Setpoint
Leaving Evap
Temperature
Inlet Vane
S&W Function
Capacity
Overrides
Leaving Evap
Temperature
Inlet Vane
S&W Function
Capacity
Overrides
Leaving Evap
Temperature
Compressor
Staging Logic
Capacity
Overrides
Vane
Outputs
Vane
Outputs
Compressor
Outputs
a0144
Recip-Standard, Screw, Recip-European, or AGU:
The CSC always provides the working setpoint
to the chiller. When the Reset Option variable is set to “None,” the Active Setpoint is the same as the
Leaving Evaporator Setpoint, which the CSC continuously sets as long as network communications
exist. You can reset the Active Setpoint with a local reset method, but it is best to let the CSC do the
reset. Table 52 summarizes the local chilled water setpoint variables. The values shown in italic are
typical settings.
Table 52. Setpoint Variables: Reciprocating/Screw
Keypad/Display ID
Chiller Controller VariableMenuItem
Active Setpoint (status only)14 (2 ckt.)Actv Spt= 45.0°F
1. Determine whether the chiller needs a local or CSC setpoint.
In almost all applications, the CSC should provide the setpoint.
2. Set the chilled water setpoint variables as required in the chiller controller. Refer to Tables 49,
50, and 51.
Temperature Control
Variable NameKeypad
Chilled Water Temperature Control Option16-1
System Setpoint16-1
Chiller Setpoint (status only)16-1
Minimum Chiller Setpoint16-2
Common Supply Deadband16-2
Common Supply Mod Limit16-2
Common Supply Sample Time16-2
Common Supply Max Change16-2
Common Supply Project Ahead Time16-2
Minimum System Setpoint17-1
Maximum System Setpoint17-1
Glycol Flag28-1
(Menu-Scr.)
The CSC’s ultimate purpose in temperature control is to distribute the same leaving evaporator water
temperature setpoint to every chiller in the network. This setpoint is the Chiller Setpoint. The CSC
can generate the Chiller Setpoint, which is not manually adjustable, in a variety of ways. See
Figure 19.
OM127-191
Figure 19. CSC Leaving Evaporator Water Temperature Setpoint Flow Chart
Chiller Setpoint
Unit
Common
Control Option
Return Water
Temperature (PA)
C&W Function
Constant Return
External Reset
External Signal
Supply Water
Common Supply
Temperature (PA)
Min Chiller Spt
Outdoor Air Temp
C&W Function
See note 1
OAT Reset
Reset Ovr.
None
Reset TypeReset Override
Constant RChWT
Temperature
Return Water
System Setpoint
OAT
RChWT
External
Return Reset
Max System Spt
Return ChWT Spt
Max System Spt
Min Sys Spt At
Max Sys Spt At
Max System Spt
a0145
Min Sys Spt At
Max Sys Spt At
Max System Spt
Min System Spt
Notes:
1. When the Chilled Water Temperature Reset Type is “None,” the System Setpoint can be set manually.
92OM127-1
System Setpoint
The Chiller Setpoint is derived from the System Setpoint, which is the CSC’s chilled water supply
setpoint for the system. You can set the System Setpoint manually or let the CSC reset it
automatically. In either case, the System Setpoint is limited to a range defined by the Minimum
System Setpoint and Maximum System Setpoint.
The Chilled Water Temperature Control Option variable defines how the Chiller Setpoint is derived
from the System Setpoint. There are two options:
• Unit (leaving evaporator water temperature control)
• Common (chilled water supply temperature control)
Unit Option
The Unit option simply sets the Chiller Setpoint equal to the System Setpoint. In effect, the common
chilled water supply setpoint becomes each chiller’s leaving evaporator water setpoint.
The Unit option should be used for systems in which each chiller is isolated when not operating.
These systems are by far the most common; they include, for example, chillers with dedicated primary
pumps or isolation valves. See Figure 20.
When the Unit option is used in systems with isolated chillers, the supply water temperature usually is
very close to the System Setpoint even though there is no direct control. (This may not be true if your
system is using load balancing.) The Common option can also be used in these systems, but the Unit
option is simpler and the effect is usually the same.
Figure 20. Typical System with Isolated Chillers
Cooling Loads
Optional secondary pump/decoupler line
Chilled water return temperature
Leaving evaporator water temperature
Common Option
The Common option uses a proportional-integral (PI) control loop to generate a Chiller Setpoint that
keeps the chilled water supply temperature at the System Setpoint.
The Common option should be used for systems in which each chiller is not isolated when not
operating. These systems are uncommon; they include, for example, chillers with a common primary
pump and no isolation valves. See Figure 21.
Chilled water supply temperature
Chiller #1
Evaporator
Chiller #2
Evaporator
Chiller #3
Evaporator
a0146
OM127-193
Because water always flows through each chiller’s evaporator, the common supply temperature varies
with the number of operational chillers in systems with nonisolated chillers. The Common option
compensates for this temperature variation by lowering the Chiller Setpoint as necessary to keep the
common supply temperature at the System Setpoint. The Unit option can also be used in these
systems, but the chilled water supply temperature is warmer than the System Setpoint whenever one
or more chillers are disabled.
The Common option may also be beneficial in any system that is using load balancing.
Figure 21. Typical System with Nonisolated Chillers
Cooling Loads
Chilled water return temperature
Leaving evaporator water temperature
Load Balancing May Affect Temperature Control
When a centrifugal chiller is being load balanced, its temperature control processes can be
Chilled water supply temperature
Chiller #1
Evaporator
Chiller #2
Evaporator
Chiller #3
Evaporator
a0147
overridden. Since load balancing limits a chiller’s ability to load, a load-balanced chiller’s leaving
evaporator water temperature always is higher than its Active Setpoint—if the temperature control
process is being overridden. In most applications, in which all centrifugal chillers have the same
capacity and efficiency, load balancing does not override temperature control.
If you find that load balancing is overriding temperature control in your system, you can eliminate the
problem by using the Common option. As described above, the Common option compensates for any
temperature control override by lowering each chiller’s Active Setpoint. The effect is to lower each
chiller’s leaving evaporator water temperature, and though these temperatures remain unequal, their
average—the supply temperature—eventually falls to the System Setpoint.
PI Control Process
When the supply temperature is above the System Setpoint, the control loop lowers the Chiller
Setpoint. When the supply temperature is below the System Setpoint, the control loop raises the
Chiller Setpoint. The Chiller Setpoint is limited to a range defined by the System Setpoint itself and
the Minimum Chiller Setpoint. Since the leaving evaporator water temperatures should never be
higher than the desired supply temperature, the System Setpoint is the upper limit. The Minimum
Chiller Setpoint is the lower limit. You should set it to the lowest acceptable leaving evaporator water
temperature.
The PI control loop consists of two intrinsic MicroTech DDC functions: Change-and-Wait and
Project Ahead. To modulate the Chiller Setpoint, these functions use five variables that are dedicated
to common chilled water supply temperature control: (1) Common Supply Deadband, (2) Common
Supply Mod Limit, (3) Common Supply Sample Time, (4) Common Supply Max Change, and (5)
Common Supply Project Ahead Time. For many applications, the default values for these variables
provide good control.
94OM127-1
Note:
The Common option must be used for applications with nonisolated chillers that require
optimal start and its automatic adaptation feature. If automatic adaptation is not needed, optimal start
works well with both the Common and Unit options.
Low Temperature Operation
The CSC has a software safety built into it that does not allow three chilled water setpoints to be
adjusted below 40.0°F (4.4°C): Minimum System Setpoint, Maximum System Setpoint, and
Minimum Chiller Setpoint. If your system can withstand low temperature operation with no danger of
freezing, you can override the safety by setting the Glycol Flag to “Yes.” This allows the above
setpoints to be adjusted down to 0.0°F (–17.8°C).
To set up chilled water temperature control
1. Determine whether Common or Unit control is required, and set the Chilled Water Temperature
Control Option variable accordingly.
In almost all applications, the Unit option provides simple and satisfactory control.
2. Set the remaining chilled water temperature control variables as required.
If you’re using the Unit option, you can ignore the following variables:
Minimum Chiller Setpoint
Common Supply Deadband
Common Supply Mod Limit
Common Supply Sample Time
Common Supply Max Change
Common Supply Project Ahead Time
If you’re using reset, you won’t need to set the System Setpoint. See “Setpoint Reset” below.
Setpoint Reset
Variable NameKeypad
Chilled Water Temperature Reset Type17-1
System Setpoint16-1
Minimum System Setpoint17-1
Maximum System Setpoint17-1
Minimum System Setpoint At17-1
Maximum System Setpoint At17-1
Constant Return Setpoint17-2
Constant Return Deadband17-2
Constant Return Mod Limit17-2
Constant Return Sample Time17-2
Constant Return Max Change17-2
Constant Return Project Ahead Time17-2
External Chilled Water Reset Signal (status
only)
Chilled Water Return Temperature (status only)17-3
Outdoor Air Temperature (status only)17-3
(Menu-Scr.)
17-3
By automatically varying the leaving evaporator water temperature to suit the building’s cooling load,
chilled water temperature reset can make some chiller systems more energy efficient. The CSC
provides four types of reset, which are described below:
• Return Water
• Outdoor Air
• External (analog signal)
OM127-195
• Constant Return (PI control)
When a reset strategy is active, it automatically changes the System Setpoint as required. Regardless
of the reset method, the Minimum System Setpoint and the Maximum System Setpoint define the
range of possible System Setpoint values. The current value of the System Setpoint is determined by
the current value of the input variable; for example, outdoor air temperature.
If you don’t want a reset, set Chilled Water Temperature Reset Type to “None” (default).
Reset Override
The CSC provides a digital input (DI 1) that you can use to override reset. You may want to do this,
for example, if very cold water is temporarily required for dehumidification.
When the reset override input is closed, the CSC sets the System Setpoint equal to the Minimum
System Setpoint. When the input is open, the reset strategy you’ve selected operates automatically.
Reset override can occur even when Chilled Water Temperature Reset Type is set to “None.”
Reset from Return Water or Outdoor Air Temperature
When the Return Water or Outdoor Air reset method is used, the System Setpoint is determined by
the temperature input and the reset function, which is shown in Figures 22 and 23. The following
variables define the function:
• Minimum System Setpoint
• Maximum System Setpoint
• Minimum System Setpoint At
• Maximum System Setpoint At
The figures show typical values of these variables. (The values of the “At” variables shown in the
figures would be appropriate for Outdoor Air reset.)
Figure 22. Return Water or Outdoor Air Reset (English)
54
Max System Spt= 54°F
49
Min System Spt= 44°F
44
System Setpoint (°F)
40
5060708090
Return Water or Outdoor Air Temperature (°F)
Max Sys Spt At= 60°F
Min Sys Spt At= 80°F
a0148
96OM127-1
Figure 23. Return Water or Outdoor Air Reset (SI)
12
11
10
9
8
7
6
System Setpoint (°C)
5
1015202530
Return Water or Outdoor Air Temperature (°C)
Max System Spt= 12°C
Min System Spt= 7°C
Max Sys Spt At= 15°C
Min Sys Spt At= 25°C
a0149
For example, if the settings of Figures 22 and 23 are used, the following occurs when Outdoor Air
reset is selected:
When the outdoor air temperature isThe System Set point will be
55.0°F (12.5°C)54.0°F (12.0°C)
70.0°F (20.0°C)49.0°F (9.5°C)
85.0°F (27.5°C)44.0°F (7.0°C)
At the keypad/display, you can monitor the current return water and outdoor air temperatures on the
last screen of menu 17.
Note:
If communications are lost with an NMP or building automation system that is supplying the
outdoor air temperature to the CSC, the CSC retains and uses the last temperature it received until
communications are restored.
To set up Return Water or Outdoor Air reset
1. Set the Chilled Water Temperature Reset Type variable to “RChWT” for Return Water reset or
“OAT” for Outdoor Air reset.
2. Set the following variables as required:
Minimum System Setpoint
Maximum System Setpoint
Minimum System Setpoint At
Maximum System Setpoint At
The CSC automatically resets the System Setpoint. You can ignore the remaining reset variables.
Note:
To use the Outdoor Air reset method, an outdoor air temperature sensor must be connected to
the CSC, an NMP, or a building automation system communicating with the CSC via Open Protocol.
To use the Return Water reset method, a return chilled water temperature sensor must be connected to
the CSC. For more information, see the “Field Wiring” section of Bulletin No. IM 618.
Reset from an External Signal
When the External reset method is used, the System Setpoint is determined by an external analog
signal and the reset function. See Figures 24 and 25. The following variables define the function:
Minimum System Setpoint and Maximum System Setpoint. The figures show typical values of these
variables.
OM127-197
Figure 24. External Reset (English)
54
49
44
Max System Spt= 54°F
System Setpoint (°F)
40
0–5 Vdc:
01235
0–10 Vdc:
0246 108
0–20 mA:
048122016
Figure 25. External Reset (SI)
12
11
10
9
8
7
6
System Setpoint (°C)
5
0–5 Vdc:
0–10 Vdc:
Min System Spt= 44°F
4
External Signal
Max System Spt= 12°C
Min System Spt= 7°C
01235
0246 108
a0150
4
0–20 mA:
048122016
External Signal
a0151
For example, if the settings of Figures 24 and 25 are used, the following occurs when External reset is
selected:
When the external analog signal isThe System Set point will be
4 mA44.0°F (7.0°C)
12 mA49.0°F (9.5°C)
20 mA54.0°F (12.0°C)
At the keypad/display, you can monitor the current value of the external signal on the last screen of
menu 17. Note that in all cases the displayed value is a conditioned value of 0–5 Vdc.
To set up External reset
1. Set the Chilled Water Temperature Reset Type variable to “External.”
2. Set the following variables as required:
Minimum System Setpoint
Maximum System Setpoint
98OM127-1
The CSC automatically resets the System Setpoint. You can ignore the remaining reset variables.
Note:
To use the External reset method, an external analog signal (0–5 Vdc, 0–10 Vdc, or 0–20 mA)
must be connected to the CSC.
Constant Return Chilled Water Temperature Control
The Constant Return reset method uses a proportional-integral (PI) control loop to generate a System
Setpoint that keeps the return chilled water temperature at the Constant Return Setpoint. It is different
from the other three reset methods in that it does not use a mathematical function to reset the System
Setpoint.
Constant return temperature control is usually used only in systems that have constant chilled water
flow. This is true because return water temperature is a good indicator of cooling load only when the
flow is constant. If your system has three-way valves at the loads or a supply-to-return bypass valve, it
probably has constant flow.
When the return temperature is above the Constant Return Setpoint, the control loop lowers the
System Setpoint. When the return temperature is below the Constant Return Setpoint, the control loop
raises the System Setpoint. The System Setpoint is limited to a range defined by the Minimum System
Setpoint and Maximum System Setpoint.
The PI control loop consists of two intrinsic MicroTech DDC functions: Change-and-Wait and
Project Ahead. To modulate the System Setpoint, these functions use five variables that are dedicated
to return chilled water temperature control: (1) Constant Return Deadband, (2) Constant Return Mod
Limit, (3) Constant Return Sample Time, (4) Constant Return Max Change, and (5) Constant Return
Project Ahead Time. For many applications, the default values for these variables provides good
control.
Note:
Although there is nothing to prevent you from using the Constant Return reset method and the
Common control option, this is not recommended. Three cascaded control loops (return to supply to
unit) are more likely to become unstable than two cascaded control loops (return to unit). And if you
want a constant return temperature, the common supply temperature does not need to be controlled—
except for applications with nonisolated chillers that require optimal start and its automatic adaptation
feature. If constant return temperature control is required, the Common control option must be used
with the Constant Return reset method.
To set up Constant Return reset
1. Set the Chilled Water Temperature Reset Type variable to “Constant RChWT.”
2. Set the following variables as required:
Minimum System Setpoint
Maximum System Setpoint
Constant Return Setpoint
Constant Return Deadband
Constant Return Mod Limit
Constant Return Sample Time
Constant Return Max Change
Constant Return Project Ahead Time
The CSC automatically resets the System Setpoint. You can ignore the remaining reset variables.
Note:
To use the Constant Return reset method, a return chilled water temperature sensor must be
connected to the CSC. For more information, see the “Field Wiring” section of Bulletin No. IM 618.
OM127-199
Chilled Water Flow Control
The CSC can control a variety of chilled water distribution system equipment in several
combinations. There are six basic configurations:
1. Fixed-speed secondary pump, with optional pressure-controlled loop bypass valve
Typical, schematic representations of these configurations are shown in Figures 26 through 31.
Configurations 1 through 5 are primary-secondary (decoupled) systems. Configuration 6 is a primaryonly system.
The following sub-sections are organized according to the types of equipment that you may have in
your system. You only need to read the ones that apply to your application. For example, if your
system is like configuration 4 (Figure 29), you should look at “Secondary Pump Logic: Single Pump”
and “Pump Speed Control.” Or if your system is like configuration 3 (Figure 28) with the optional
bypass valve, you should look at “Secondary Pump Logic: Sequenced Pumps” and “Loop Bypass
Valve Control.”
Figure 26. Configuration. 1: Fixed-Speed Single Pump
Cooling Loads
Optional pressure-controlled loop bypass
Differential pressure transducer
DPT
P1
ChWRChWS
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100OM127-1
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