Page 1
Operating Manual
Group: Chiller
Part Number: 331373701
Effective: November 2008
Supersedes: OM WGS-4
Water-Cooled Screw Compressor Chillers
WGS 130AW to WGS 190AW, Packaged Water-Cooled Chiller
WGS 130AA to WGS 190AA, Chiller with Remote Condenser
120 to 200 Tons, 420 to 700 kW
R-134a, 60 Hz
Software Version WGSD30101H
OM WGS-5
Page 2
Table of Contents
Introduction ....................................... 3
General Description..................................... 3
Nomenclature............................................... 3
Definitions ..........................................4
W
iring Diagrams ............................... 8
Control Panel Layout...................... 10
MicroTech II Controller .............. 13
System Architecture................................... 13
General Description................................... 14
Units of measure........................................ 14
Sequence of Operation ....................16
Start-Up and Shutdown ..................23
Pre Start-up................................................ 23
Start-up ...................................................... 23
Weekend or Temporary Shutdown ............ 24
Start-up after Temporary Shutdown .......... 24
Extended Shutdown................................... 24
Start-up after Extended Shutdown............. 25
Unit Controller.................................28
Unit Inputs/Outputs ................................... 28
Unit Setpoints ............................................ 28
Circuit Controller............................ 31
Circuit Inputs and Outputs......................... 31
Circuit Setpoint Table................................ 32
Alarms and Events ..........................34
Unit Stop Alarms ....................................... 34
Unit Events ................................................ 36
Circuit Stop Alarms ................................... 36
Circuit Events ............................................ 38
Alarm Logging .......................................... 39
Event Logging ........................................... 40
Clearing Alarms......................................... 40
Unit Controller Functions............... 40
Unit Enable ................................................ 41
Unit Mode Selection .................................. 42
Unit States.................................................. 43
Evaporator Pump Control .......................... 44
Leaving Water Temperature (LWT) Reset . 45
Planned Unit Capacity Overrides .............. 47
Condenser Pump and Tower Control......... 48
Cooling Tower Control ..............................49
Evaporative Condenser Control................. 51
Circuit Controller Functions.......... 54
Refrigerant Calculations ............................54
Compressor Control................................... 55
Internal Capacity Overrides ....................... 58
Slide Positioning........................................ 59
Expansion Valve Control ...........................61
Oil Heater Control .....................................65
Starter Communications.............................65
Condenser Fan Control .............................. 66
Condenser Fan VFD ..................................68
Digital Output Control............................... 68
Using the Controller .................................. 69
Security...................................................... 71
Entering Passwords.................................... 71
Editing Setpoints........................................ 71
Clearing Alarms ......................................... 71
Menu Descriptions .......................... 72
Unit Controller........................................... 72
Circuit Controller....................................... 87
Editing Review ..........................................93
BAS Interface .................................. 94
Unit Troubleshooting Chart........... 95
Conform to the BACnet protocol
(ANSI/ASHRAE 135-2001).
Illustrations and data cover McQuay International products at the time of publication and we reserve the right to make
The following are trademarks or registered trademarks of their respective companies:
BACnet from ASHRAE; L
2 WGS 130A to WGS 190A OM WGS-5
2008 McQuay International
changes in design and construction at anytime without notice.
ONMARK and LONWORKS from Echelon Corporation;
GeneSys, McQuay and MicroTech II from McQuay International.
Unit controllers are LONMARK
certified with an optional L
communications module.
ONWORKS
Page 3
Introduction
General Description
McQuay Model WGS water chillers are designed for indoor installations and are available
with factory-mounted water-cooled condensers (Model WGS AW), or arranged for use with
remote air-cooled or evaporative condensers (Model WGS AA). Each water-cooled unit
(WGS-AW) is completely assembled and factory wired before factory evacuation, charging
and testing. The units consist of two semi-hermetic rotary screw compressors, a two-circuit
shell-and-tube evaporator, two shell-and-tube water-cooled condensers, and complete
refrigerant piping.
Units manufactured for use with remote condensers (Models WGS-AA) have all refrigerant
specialties factory-mounted and have two sets of connection points for refrigerant discharge
and liquid lines to and from the remote condenser. Discharge valves are included
Each circuit’s liquid line components are manual liquid line shutoff valve, charging valve,
filter-drier, liquid line solenoid valve, sight glass/moisture indicator, and electronic
expansion valve.
The electrical control center includes a MicroTech II microprocessor control system and
equipment protection and operating controls necessary for dependable, automatic operation.
The compressor circuits are equipped with individual circuit breakers and a unit disconnect
switch is available as an option over the standard power block.
This software revision adds fixes several bugs in the IP/SI units logic, improves the
operation of remote evaporator units in low ambient air temperatures, improves
communications with the solid state starter and provides compressor electrical data at the
supervisor port for building automation systems.
Nomenclature
W G S 130 - A W
Water-Cooled Condensing
Rotary Screw Compressor
Nominal Capacity (Tons)
Global
W = Water-Cooled Condenser
A = Unit Less Condenser
Design Vintage
OM WGS-5 WGS 130A to 190A 3
Page 4
Definitions
Active Setpoint
The active setpoint is the setting in effect at any given moment. This variation occurs on
setpoints that can be altered during normal operation. Resetting the chilled water leaving
temperature setpoint by one of several methods, such as return water temperature, is an
example.
Active Capacity Limit
The active setpoint is the setting in effect at any given moment. Any one of several external
inputs can limit a compressor’s capacity below its maximum value.
Condenser Recirc Timer
A timing function, with a 30-second default, that holds off any reading of condenser water
for the duration of the timing setting. This delay allows the water sensors (especially water
temperatures) to take a more accurate reading of the condenser water system conditions.
Condenser Saturated Temperature Target
The saturated condenser temperature target is calculated by first using the following
equation:
Sat condenser temp target raw = 0.833(evaporator sat temp) + 68.34
The “raw” value is the initial calculated value. This value is then limited to a range defined
by the Condenser Saturated Temperature Target minimum and maximum setpoints. These
setpoints simply cut off the value to a working range, and this range can be limited to a
single value if the two setpoints are set to the same value.
CPU Error
These are problems caused by a malfunction of the central processing unit.
Dead Band
The dead band is a set of values associated with a setpoint such that a change in the variable
occurring within the dead band causes no action from the controller. For example, if a
temperature setpoint is 44F and it has a dead band of 2 degrees, nothing will happen until
the measured temperature is less than 42F or more than 46F.
DIN
Digital input, usually followed by a number designating the number of the input.
Discharge Superheat
Discharge superheat shall be calculated for each circuit using the following equation:
Discharge Superheat = Discharge Temperature – Condenser Saturated Temperature
Error
In the context of this manual, “Error” is the difference between the actual value of a variable
and the target setting or setpoint.
Evaporator Approach
The evaporator approach is calculated for each circuit. The equation is as follows:
Evaporator Approach = LWT – Evaporator Saturated Temperature
4 WGS 130A to 190A OM WGS-5
Page 5
Evap Recirc Timer
A timing function, with a 30-second default, that holds off any reading of chilled water for
the duration of the timing setting. This delay allows the chilled water sensors (especially
water temperatures) to take a more accurate reading of the chilled water system conditions.
EXV
Electronic expansion valve, used to control the flow of refrigerant to the evaporator,
controlled by the circuit microprocessor.
High Saturated Condenser – Hold Value
High Cond Hold Value = Max Saturated Condenser Value – 5F
This function prevents the compressor from loading whenever the pressures approach
within 5 degrees of the maximum discharge pressure. The purpose is to keep the
compressor online during periods of possibly temporary elevated pressures.
High Saturated Condenser – Unload Value
High Cond Unload Value = Max Saturated Condenser Value – 3F
This function unloads the compressor whenever the pressures approach within 3 degrees of
the maximum discharge pressure. The purpose is to keep the compressor online during
periods of possibly temporary elevated pressures.
High Superheat Error
The degrees of temperature difference between 40F and the actual discharge temperature.
Light load Stg Dn Point
The percent load point at which one of two operating compressors will shut off, transferring
the unit load to the remaining compressor.
Load Limit
An external signal from the keypad, the BAS or a 4-20 ma signal that limits the compressor
loading to a designated percent of full load. Frequently used to limit unit power input.
Load Balance
Load balance is a technique that equally distributes the total unit load among the running
compressors.
Low Ambient Lockout
Prevents the unit from operating (or starting) at ambient temperatures below the setpoint.
Low Pressure Hold Setpoint
The psi evaporator pressure setting at which the controller will not allow further compressor
loading.
Low/High Superheat Error
The difference between actual evaporator superheat and the superheat target.
LWT
Leaving water temperature. The “water” is any fluid used in the chiller circuit.
OM WGS-5 WGS 130A to 190A 5
Page 6
LWT Error
Error in the controller context is the difference between the value of a variable and the
setpoint. For example, if the LWT setpoint is 44F and the actual temperature of the water
at a given moment is 46F, the LWT error is +2 degrees.
LWT Slope
The LWT slope is an indication of the trend of the water temperature. It is calculated by
taking readings of the temperature every few seconds and subtracting them from the
previous value, over a rolling one-minute interval.
ms
Milli-second
Maximum Saturated Condenser Temperature
The maximum saturated condenser temperature allowed is calculated based on the
compressor operational envelope.
NC
Normally closed - usually refers to a contactor or valve.
NO
Normally open - usually refers to a contactor. or valve.
OAT
Outside ambient air temperature.
Offset
Offset is the difference between the actual value of a variable (such as temperature or
pressure) and the reading shown on the microprocessor as a result of the sensor signal. See
notes on page 33 for explanation of sensor off set.
pLAN
Peco Local Area Network is the proprietary name of the network connecting the control
elements.
Rapid Stop
A compressor stop process that circumvents the normal pumpdown cycle.
Refrigerant Saturated Temperature
Refrigerant saturated temperature is calculated from the pressure sensor readings for each
circuit. The pressure is fitted to an R-134a temperature/pressure curve to determine the
saturated temperature.
Soft Load
Soft Load is a control sub-routine that allows the chiller to load up gradually. It requires
setpoint inputs of selecting it by Yes or No inputs, by selecting the percent load to start
ramping up, and by selecting the time to ramp up to full load (up to 60 minutes).
SP
Setpoint
SSS
Solid state starter as used on McQuay screw compressors.
Suction Superheat
Suction superheat is calculated for each circuit using the following equation:
Suction Superheat = Suction Temperature – Evaporator Saturated Temperature
6 WGS 130A to 190A OM WGS-5
Page 7
Stage Up/Down Accumulator
The accumulator can be thought of as a bank storing occurrences that indicate the need for
an additional fan.
Stageup/Stagedown Delta-T
Staging is the act of starting or stopping a compressor or fan when another is still operating.
Startup and Stop is the act of starting the first compressor or fan and stopping the last
compressor or fan. The Delta-T is the “dead band” on either side the setpoint in which no
action is taken.
Stage Up Delay
The time delay from the start of the first compressor to the start of the second.
Startup Delta-T
Number of degrees above the LWT setpoint required to start the first compressor.
Stop Delta-T
Number of degrees below the LWT setpoint required for the last compressor to stop.
VAC
Volts, Alternating current, sometimes noted as vac.
VDC
Volts, Direct current, sometimes noted as vdc.
VFD
Variable Frequency Drive, a device used to vary an electric motor’s speed.
OM WGS-5 WGS 130A to 190A 7
Page 8
Wiring Diagrams
UNIT MAIN
A
A
Figure 1, WGS 130AW – 190AW Field Wiring Diagram (Optional Single Point Connection)
3 PHASE
POWER
SUPPLY
DISCONNECT
(BY OTHERS)
TERMINAL BLOCK
GND LUG
TO COM PRESSO R(S)
NOTE: ALL FIELD WIRING TO BE
INSTALLED AS NEC CLASS 1
WIRING SYSTEM WITH CONDUCTOR
RATED 600 VOLTS
FACTORY SUPPLIED ALARM
FIELD WIRED
ALARM BELL
OPTION
ABR
LARM BELL RELAY
FUSED CONTROL
CIRCUIT TRANSFORMER
CHWR
EVAP. PUMP RELAY #1
(BY OTHERS)
120 VAC 1.0 AMP MAX
CHWR
EVAP. PUMP RELAY #2
(BY OTHERS)
120 VAC 1.0 AMP MAX
CWR
COND. PUMP RELAY #1
(BY OTHERS)
120 VAC 1.0 AMP MAX
CWR
COND. PUMP RELAY #2
(BY OTHERS)
120 VAC 1.0 AMP MAX
M11
TOWER FA N #1
(BY OTHERS)
120 VAC 1.0 AMP MAX
M12
TOWER FA N #2
(BY OTHERS)
120 VAC 1.0 AMP MAX
COOLING TOWER BYPASS
(BY OTHERS)
(BY OTHERS)
FU4 FU5
120 VAC
FU7
TB1
(115 VAC)
1
2
82
2
85
2
86
2
87
2
88
2
89
2
78
77
80
79
81
75
TB1-2
N
24 VAC
120 VAC
N
120 VAC
N
120 VAC
N
120 VAC
N
120 VAC
N
120 VAC
N
0-10VDC
N
0-10VDC
BELL
COM NO
12
ALARM BELL OPTION
LARM BELL
RELAY
REMOTE STOP
SWITCH
(BY OTHERS)
ICE MODE
SWITCH
(BY OTHERS)
EVAP. FLOW
SWITCH
(BY OTHERS)
*MANDATORY IF FACTORY FLOW SWITCH OPTION IS NOT SELECTED
COND. FLOW
SWITCH
(BY OTHERS)
*MANDATORY IF FACTORY FLOW SWITCH OPTION IS NOT SELECTED
EVAP. WATER RESET
8 WGS 130A to 190A OM WGS-5
TIME
CLOCK
AUTO
ON
AUTO
ON
NOR. OPEN PUMP AUX.
CONTACTS (OPTIONAL)
NOR. OPEN PUMP AUX.
CONTACTS (OPTIONAL)
4-20MA FOR
(BY OTHERS)
4-20MA FOR
DEMAND LIMIT
(BY OTHERS)
OFF
MANUAL
OFF
MANUAL
TB1
(24 VAC OR 30 VDC)
60
66
IF REMOTE STOP CONTROL
897
IS USED, REMOVE LEAD 897
FROM TERM. 40 TO 53.
60
68
60
67
60
76
+
-
+
-
72
70
71
70
DWG. 330588201 REV. 0B
GND
Page 9
Figure 2, WGS 130AA – 190AA Field Wiring Diagram (Remote Air-cooled Condenser)
UNIT MAIN
(
)
)
3 PHASE
POWER
SUPPLY
DISCONNECT
(BY OTHERS)
TERMINAL BLOCK
GND LUG
TO COMPRESSOR(S)
NOTE: ALL FIELD WIRING TO BE
INSTALLED AS NEC CLASS 1
WIRING SYSTEM WITH CONDUCTOR
RATED 600 VOLTS
FACTORY SUPPLIED ALARM
ALARM BELL
OPTION
CIRCUIT #1
M11
CONDENSER FAN
CONTACTOR COIL #1
M12
CONDENSER FAN
CONTACTOR COIL #2
M13
CONDENSER FAN
CONTACTOR COIL #3
M14
CONDENSER FAN
CONTACTOR COIL #4
M15
CONDENSER FAN
CONTACTOR COIL #5
M16
CONDENSER FAN
CONTACTOR COIL #6
FIELD WIRED
TB6
92
144
98
145
93
146
98
145
94
148
98
145
95
150
98
145
96
152
98
145
97
154
98
145
REMOTE STOP
SWITCH
(BY OTHERS)
ICE MODE
SWITCH
(BY OTHERS)
ABR
ALARM BELL RELAY
NO1
2
NO2
2
NO3
2
C
C
NO4
2
NO5
2
NO6
2
FUSED CONTROL
CIRCUIT TRANSFORMER
EVAP. PUMP RELAY #1
120 VAC 1.0 AMP MAX
EVAP. PUMP RELAY #2
120 VAC 1.0 AMP MAX
120 VAC
N
120 VAC
N
120 VAC
N
(LOCATED ON
CONTROLLER)
120 VAC
N
120 VAC
N
(LOCATED ON
CONTROLLER)
120 VAC
N
TIME
CLOCK
AUTO
ON
MANUAL
AUTO
ON
MANUAL
OFF
OFF
CHWR
(BY OTHERS)
CHWR
(BY OTHERS)
J12
CIRCUIT
J13
CIRCUIT
FU4
120 VAC
FU7
TB1
(115 VAC)
CIRCUIT #2
CONDENSER FAN
CONTACTOR COIL #1
CONDENSER FAN
CONTACTOR COIL #2
CONDENSER FAN
CONTACTOR COIL #3
CONDENSER FAN
CONTACTOR COIL #4
CONDENSER FAN
CONTACTOR COIL #5
CONDENSER FAN
CONTACTOR COIL #6
TB1
24 VAC
FU5
TB1-2
1
2
82
2
85
2
81
120 VAC
N
120 VAC
N
24 VAC
ALARM BELL
BELL
COM
2
1
ALARM BELL OPTION
RELAY
NO
75
TB7
92
244
245
246
245
248
245
250
245
252
245
254
245
NO1
2
NO2
2
NO3
2
C
C
NO4
2
NO5
2
NO6
2
98
M21
93
98
M22
94
98
M23
95
98
M24
96
98
M25
97
98
M26
60
66
IF REMOTE STOP CONTROL
897
IS USED, REMOVE LEAD 897
FROM TERM. 40 TO 53.
N
N
N
N
N
N
120 VAC
120 VAC
120 VAC
120 VAC
120 VAC
120 VAC
J12
(LOCATED ON
CIRCUIT
CONTROLLER)
J13
(LOCATED ON
CIRCUIT
CONTROLLER
60
68
EVAP. FLOW
SWITCH
(BY OTHERS)
*MANDATORY IF FACTORY FLOW SWITCH OPTION IS NOT SELECTED.
OM WGS-5 WGS 130A to 190A 9
NOR. OPEN PUMP AUX.
CONTACTS (OPTIONAL)
4-20MA FOR
EVAP. WATER RESET
(BY OTHERS)
4-20MA FOR
DEMAND LIMIT
(BY OTHERS)
60
67
+
-
+
-
72
70
71
70
GND
DWG. 330588101 REV. 0C
Page 10
Control Panel Layout
r
r
Figure 3, Outer (Microprocessor) Panel
T2, Unit Controlle
T13, Circ#1 Controller
T14, Circ#1 Load Solenoid
T15, Circ#1 EXV Power
T23, Circ#2 Controlle
T24, Circ#2 Load Solenoid
T25, Circ#2 EXV Power
Unit Controller
MHPR11 &12, Mechanical
High Pressure Relay
Circ#1 Controller
Circuit Breaker &
Switch Panel
External Disconnect Handle
Circ#1 & 2 EXV Drivers
Circ#2 Controller
TB3, Circ#2 Controller
Terminal Board
TB2, Circ#1 Controller
Terminal Board
TB1 Unit Controller
Terminal Board
NOTES:
1. Transformers T2 through T25 are class 100, 120V to 12V.
2. Switches for MHPR 11 and 12 (Mechanical High Pressure Switches) are located on the compressors.
3. Mechanical High Pressure Switches Open at 310 psi, Close at 250 psi.
10 WGS 130A to 190A OM WGS-5
Page 11
Figure 4, Inner (Power) Panel (Optional Single-Point Power with Disconnect Switches
Shown)
Circ#1 Solid State Starter
Circ#2 Solid State Starter
SSS1 Bypass Contactor
SSS2 Bypass Contactor
Secondary Fuses
External Disconnect Handle
Circ#1 Circuit Breaker
Circ#2 Circuit Breaker
Unit Disconnect Switch
W/ External Handle
T1, Supply Voltage to
120V Transformer
Primary Fuses
Outside (Microprocessor) Panel
OM WGS-5 WGS 130A to 190A 11
Page 12
Figure 5, Circuit Breaker/Fuse Panel
Open Location
S1 Main Unit On-Off Switch
CS2, Circuit#2 On-Off Switch
CS1, Circuit#1 On-Off Switch
CB11 Circ#1 Circuit Breaker
CB12, Circ#1 Sump Heater
Open Location
CB21, Circ#2 Circuit
CB22, Circ#2 Sump Heater
Open Locations
Location for Optional
115V Receptacle
OUTER PANEL INNER PANEL
T13T2 T14 T15 T23 T24 T25
UNIT
CONTROLLER
EXV.
DRIVER
#1
CIRCUIT CONTROLLER
#1
MODBUS CARD
CONVERTER BOARD
EXV.
DRIVER
#2
CIRCUIT CONTROLLER
#2
TB1
TB11 TB21
MHPR1MHPR
CS1
S1S
REC
OPTION
2
CS2
CB11
CB12
SP
CB21
CB22
SP
FU7
F3
SINGLE
POINT
OR
CIR. #1
DS
HANDLE
(MULTI-
POINT)
P
CIR. #2
DS
HANDLE
(MULTI-
POINT)
SSS #1 SSS #2
D3
CT2
T1
F
U
5
CONTACTOR
CT1
THERM-
ISTOR
CARD
BYPASS
C
B
1
(DS1 DS2
MULTIPOINT
POWER)
CT3
C
B
2
CONTR.
BRD.
CT3
F
U
6
F
U
4
D3
CONTR.
BRD.
CT2
DS1
CONTACTOR
CT1
THERM-
ISTOR
CARD
BYPASS
G
N
D
12 WGS 130A to 190A OM WGS-5
330589001 REV. 00 - Legend
Page 13
MicroTech II Controller
Software Version:WGSD30101E
Bios: 3.62
BOOT: 3.0F
System Architecture
The WGS MicroTech distributed control system consists of multiple microprocessorbased controllers that provide monitoring and control functions required for the controlled,
efficient operation of the chiller. The system consists of the following components:
Unit Controller
and communicates with the other controllers. It is located in the control panel and is
labeled “UNIT CONTROL”.
Circuit Controllers
settings specific to the circuit. The controllers are located in the control panel and are
labeled “CIRCUIT CONROL”.
In addition to providing all normal operating controls, the MicroTech II control system
monitors equipment protection devices on the unit and will take corrective action if the
chiller is operating outside of its normal design envelope. If an alarm condition develops,
the controller will shut down the compressor, or entire unit, and activate an alarm output.
Important operating conditions at the time an alarm condition occurs are retained in the
controller’s memory to aid in troubleshooting and fault analysis.
The system is protected by a password scheme that allows access only by authorized
personnel. The operator must enter the operator password into the controller’s keypad
before any setpoints can be altered.
, one per chiller controls functions and settings that apply to the unit
for each compressor/circuit that control compressor functions and
BAS Interface-
Modbus,
BACnet,
Lonworks
PLAN Addressing
Chiller
RS485/
LON
Unit Controller
4x20 LCD
Carel pLAN
Circuit Controller
Solid
State
Starter
RS485 RS485
Circuit Controller
4x20 LCD
4x20 LCD
Solid
State
Starter
The pLAN (proprietary local area network) addressing is based on a commonly used
scheme among all applications using pLAN networked MicroTech II controllers. Only
three addresses are needed, and are designated as shown in the following table.
Controller Address Dip Sw 1 Position Dip Sw 2 Position Dip Sw 3 Position
Unit 5 Up Down Up
Circuit 1 1 Up Down Down
Circuit 2 2 Down Up Down
The Dip switches are located on the upper front of the controller above the screen.
OM WGS-5 WGS 130A to 190A 13
Page 14
General Description
The MicroTech II controller’s design permits the chiller to run more efficiently, and it
simplifies troubleshooting if a system failure occurs. Every MicroTech II controller is
programmed and tested prior to shipment to assist in a trouble-free start-up. The MicroTech
II controller can be used to cycle fans on remote air-cooled condensers for head pressure
control when the setpoint Water Cooled=N is selected in one of the setpoint menu screens.
Water Cooled=Y sets the chiller for operation with the water-cooled condenser and activates
settings for cooling tower control. Remote evaporative condensers will have to have selfcontained, on-board, head pressure control systems.
Units of measure
Version “C”, as described in this manual, supports metric (SI) units of measure.
Inch-Pound SI
F to 0.1F C to 0.1C
psi to 0.1 psi KPa to 1.0 kPa
Distributed Control
The WGS units have three MicroTech II microprocessors, a Unit Controller plus a Circuit
Controller for each of the two circuits. The Circuit Controllers are independent such that
either one will operate its circuit if the other Circuit Controller is out of service.
Operator-friendly
The MicroTech II controller menu structure is separated into three distinct categories, which
provide the operator or service technician with a full description of the following:
1. Current unit status
2. Control parameters (setpoint settings and adjustment). Security protection prevents
unauthorized changing of the setpoints and control parameters.
3. Alarm notification and clearing
The MicroTech II controller continuously performs self-diagnostic checks, monitoring
system temperatures, pressures and protection devices, and will automatically shut down a
refrigerant circuit or the entire unit if a fault occurs. The cause of the shutdown and date
stamp are retained in memory and can be easily displayed in plain English for operator
review, which is an extremely useful feature for troubleshooting. In addition to displaying
alarm diagnostics, the MicroTech II controller also provides the operator with a warning of
pre-alarm limit conditions.
Staging
The two screw compressors are loaded and staged on and off as a function of leaving chilled
water temperature, number of starts and run-hours. See Sequence of Operation beginning
on page 16.
Equipment Protection
The unit is protected by alarms that shut it down and require manual reset, and also by limit
alarms that limit unit operation in response to some out-of-ordinary condition. Shutdown
alarms activate an alarm signal that can be wired to a remote device.
14 WGS 130A to 190A OM WGS-5
Page 15
Unit Enable Selection
A
(4)
Enables unit operation from local keypad or digital input.
Unit Mode Selection
Selects standard cooling, ice, glycol, or test operation mode.
Keypad/Display
A 4-line by 20-character/line liquid crystal display and 6-key keypad is mounted on each
controller. Its layout is shown below.
Figure 6, Keypad and Display in MENU Mode
Air Conditioni ng
Key to Screen Pathway
<
LARM
<
VIEW
<
Arrow Keys
SET
"Enter" Key and Green
Red Alarm Light
Menu Key
Comp. Run Light
The four arrow keys (UP, DOWN, LEFT, RIGHT) have three modes of use.
1. Scroll between data screens as indicated by the arrows (default mode).
2. Select a specific data screen in a hierarchical fashion using dynamic labels on the right
side of the display (this mode is entered by pressing the MENU key).
3. Change field values in edit mode according to the following table:
LEFT Default
RIGHT Cancel
UP Increment
DOWN Decrement
These four edit functions are indicated by one-character abbreviations on the right side of
the display (this mode is entered by pressing the ENTER key).
OM WGS-5 WGS 130A to 190A 15
Page 16
Sequence of Operation
Compressor Heaters
With the control power on, 120V power is applied through the control circuit Fuse FU7 to
the compressor oil separator heater (HTR-OIL SEP).
Startup/Compressor Staging
During Cool Mode the following must be true to start a circuit operating. The evaporator
and condenser pump (WGS-AW only) outputs must be energized and flow must be
established for a period of time defined by the evaporator recirculate setpoint. Established
flow will be detected by evaporator and condenser water flow switches. The water
temperature leaving the evaporator must be greater than the Active Leaving Water
Temperature setpoint, plus the Startup Delta-T, before a circuit will start. The first circuit to
start is determined by sequence number. The lowest sequence numbered circuit will start
first. If all sequence numbers are the same (default), then the circuit with the fewest number
of starts will start first.
During operation, the slide valves for loading and unloading will be pulsed until the active
leaving water temperature setpoint is maintained. The second circuit start will occur once
the first circuit has loaded to 75% slide capacity or is in Capacity Limit and the water
temperature leaving the evaporator is greater than the active leaving water temperature
Setpoint plus Stage Delta-T. The circuits will load or unload simultaneously through a
continuous capacity control to maintain the evaporator leaving water temperature. If all
sequence numbers are the same, the circuit with the most run hours will be shut down first.
The circuit with the most run hours will stop when the water temperature leaving the
evaporator is less than the Active Leaving Water Temperature Setpoint minus Stage DeltaT. The last remaining circuit will shut down when the water temperature leaving the
evaporator is lower than the Active Leaving Water Temperature Setpoint minus the Stop
Delta-T.
Automatic Pumpdown
The Model WGS chiller has two separate refrigerant circuits so the refrigerant charge is
stored in the condenser when the circuit is off. Pumpdown to the condenser helps keep
refrigerant from migrating to the compressor. It also helps establish a pressure differential
on start for oil flow. In a normal shutdown, each circuit will close its expansion valve,
causing the evaporator pressure to reach a low-pressure setpoint. Once this setpoint is
reached, or a specified amount of time has elapsed, the running circuit will be shut down.
Chilled Water and Condenser Water Pumps
The chiller’s MicroTech II controller has a total of four pump outputs, two for the
evaporator and two for the condenser (WGS-AW only). There is a manual setting in the
software for the user to select either pump output 1 or 2. It is recommended that the
chiller’s outputs control the water pumps, as this will offer the most protection for the unit.
Cooling Tower Control
The MicroTech II controller can control the cooling tower fans and/or a tower bypass valve.
This provides a simple and direct method to control the unit’s discharge pressure.
Programming directions and the sequence of operation can be found on page 49. Some
eans of discharge pressure control is recommended and must be installed if the entering
m
condenser water temperature to the condenser can fall below 60F.
Condenser Fan Control
The MicroTech II controller can be programmed to cycle air-cooled condenser fans on and
off based on the discharge pressure. Details are on page 66.
16 WGS 130A to 190A OM WGS-5
Page 17
Low Ambient Start Logic
Low pressure operation at start (due to low ambient air temperature)is allowed for every
start regardless of the condenser saturated temperature at start or condenser configuration
( water-cooled or remote condenser). This is called Start Logic. START Logic is active for
a time period determined by the unit Startup Timer setpoint. This was called the Low OAT
Start Timer in previous software versions.
The Low OAT Restart Failure logic, which applies ONLY to units configured for remote
condenser, still allows for three start attempts. If the condenser saturated temperature at
start is less than 70F, another start attempt is allowed until failure of the third attempt,
which will generate an alarm.
Remote Condenser EXV Operation
For units configured for remote condensers, there is pre-open logic that allows the electronic
expansion valve to open prior to starting the compressor. This allows the expansion valve
to be in a better position for control at start-up. The factory mounted liquid line solenoid
remains closed until the compressor starts. On units configured for remote condensers, if
the evaporator pressure is greater than the condenser pressure at start, the pre-open logic is
bypassed. NOTE: Pre-open logic also exists for units configured as packaged water cooled
condensers.
Electronic expansion valve post-open logic has been added to help prevent hydraulic lock
between the liquid line solenoid and the electronic expansion valve when a circuit cycles
off. After the compressor performs a pump down and cycles off, the electronic expansion
valve will re-open for 30 seconds and then return to its closed position.
OM WGS-5 WGS 130A to 190A 17
Page 18
Unit Controller Sequence of Operation
Unit power up
Unit in Off state
The chiller may be disabled via the unit switch, the remote switch, the keypad
enable setting, or the BAS network. In addition, the chiller will be disabled if both
circuits are disabled, either because of an alarm or the circuit pumpdown switch on
No
each circuit, or if there is a unit alarm. If the chiller is disabled, the unit status
display will reflect this and also show why it is disabled.
Is unit enabled?
Yes
Evaporator pump output on
Is flow present?
Yes
Wait for chilled water loop to
recirculate.
If the unit switch is off, the unit status will be
disabled due to network command, the unit status will be
the remote switch is open, the unit status will be
alarm is active, the unit status will be
are enabled, the unit status will be
Off:All Cir Disabled
Off:Unit Switch
Off:Remote Switch
Off:Unit Alarm
. If the chiller is
Off:BAS Disable
. When a unit
. In cases where no circuits
.
If the chiller is enabled, then the unit will be in the Auto state and the evaporator
water pump output will be activated.
No
The chiller will then wait for the flow switch to close, during which time the unit
status will be
Auto:Wait for flow
.
After establishing flow, the chiller will wait some time to allow the chilled water loop
to recirculate for an accurate reading of the leaving water temperature. The unit
status during this time is
Auto:Evap Recirc
.
. When
Keep evaporator pump
output on while unit is
enabled.
No
Is there enough load to
start chiller?
Yes
18 WGS 130A to 190A OM WGS-5
The chiller is now ready to start if enough load is present. If the LWT is not high
enough to start, the unit status will be
If the LWT is high enough to start, the unit status will be
Auto:Wait Evap Flow
Auto
.
.
Page 19
Is unit watercooled?
Yes
If the unit is configured as watercooled, the condenser pump will need to be started.
Otherwise, the unit can start the first circuit at this point.
Condenser pump output on
Is flow present?
Yes
Wait for condenser water
loop to recirculate.
Keep condenser pump
output on while unit is
enabled and load is present.
Start first circuit.
Load/unload as needed to
satisfy load.
Is more capacity
needed to satisfy load?
If load is present, the condenser water pump output will be activated.
No
The chiller will then wait for the condenser flow switch to close, during which time
the unit status will be
No
Auto:Wait Cond Flow
.
After establishing condenser flow, the chiller will wait some time to allow the
condenser water loop to recirculate and guarantee consistent flow. The unit status
during this time is
Auto:Cond Recirc
.
Once the condenser flow has been present for enough time, the unit status will
become
Auto
. The tower control logic will start working to control the condenser
water temperature, using outputs from the unit controller to control tower fans,
bypass valves, and vfd's as determined by the tower set points.
The first circuit to start is generally the one with the least number of starts, or circuit
one if there is a tie. This circuit will go through its start sequence at this point.
A number of fans may be started with the compressor based on the OAT. Fan
stages will be added/removed as needed to control condenser pressure. The EXV
will begin controlling at this point as well. The compressor cannot start loading until
it has at least 22
o
discharge superheat for more than 30 seconds.
The first circuit will load and unload as needed in an attempt to satisfy the load. It
will eventually get to a point where it is considered to be at full load. A circuit is at
No
full load when it reaches 75% slide target, it reaches the max slide target setting, or
it encounters a problem and is running in an inhibited state.
If a single circuit is not enough to satisfy the load, the second circuit will need to be
started.
No
Yes
Has the stage up time
delay expired?
Yes
OM WGS-5 WGS 130A to 190A 19
A minimum time must pass between the start of the first circuit and the second
circuit.
Page 20
The second circuit will go through its start sequence at this point.
Start second circuit.
Load/unload as needed to
satisfy load.
Can one circuit handle
the load?
Yes
Shut down one circuit.
Load/unload as needed to
satisfy load.
A number of fans may be started with the compressor based on the OAT. Fan
stages will be added/removed as needed to control condenser pressure. The EXV
will begin controlling at this point as well. The compressor cannot start loading until
it has at least 22
o
discharge superheat for more than 30 seconds.
Both circuits will now load/unload as needed to satisfy the load. In addition, they will
load balance so that both circuits are providing nearly equal capacity.
No
As the load drops off, the circuits will unload accordingly. If the LWT gets low
enough, or both circuits unload enough, one circuit can shut off.
The first circuit to shut off is generally the one with the most run hours. The circuit
will do a pumpdown by closing the EXV and continuing to run the compressor until it
reaches the pumpdown pressure or exceeds the pumpdown time limit. Then, the
compressor and all fans will be turned off.
The single running circuit will load/unload as needed to satisfy the load.
No
With one circuit running, the load may drop off to the point where even minimum
Is load satisfied?
Yes
unit capacity is too much. The load has been satisfied when the LWT drops below
the shutdown point. At this time the only running circuit can shut down.
The last circuit running now shuts down. The circuit will do a pumpdown by closing
the EXV and continuing to run the compressor until it reaches the pumpdown
Shut down last circuit.
pressure or exceeds the pumpdown time limit. Then, the compressor and all fans
will be turned off.
The unit should be ready to start again when the LWT gets high enough. The unit
Turn off condenser pump
and tower control.
status at this time will be
The condenser pump and tower control outputs are turned off until the LW T is high
enough to start again.
Auto:Wait for load
.
20 WGS 130A to 190A OM WGS-5
Page 21
Circuit Controller Sequence of Operation
Unit power up
Circuit is in Off state
Next on?
Yes
Stage up now?
Yes
No
No
When the circuit is in the Off state the EXV is closed, compressor is off, and all fans
are off. The oil heater will be on at this time as long as oil is detected in the
separator.
If the compressor is ready to start when needed, the circuit status will be
Off:Ready
be
. When the circuit switch is off, the circuit cannot start and the status will
Off:Pumpdown Switch
.
If this compressor has the least starts, the other compressor is disabled for some
reason, or the other compressor is already running, then this compressor will be
designated as the next one on.
If there is a need for more cooling capacity, the compressor designated as next on
can start.
Is unit watercooled?
Yes
Preopen EXV
Start Compressor
No
If the unit is configured as watercooled, then the EXV preopen process must be
performed. Otherwise, this is skipped and the compressor can be started.
At this point, the EXV will perform a preopen. While the compressor is off, the EXV
is opened for a period of time to prime the evaporator and avoid low pressure at
startup. The circuit status will display
EXV Preopen
.
When the compressor starts, the EXV will open (if not already open) and hold at
3000 steps for 15 seconds.
If the unit is aircooled, depending on the OAT, a number of fans may be started with
the compressor to keep condenser pressure from climbing too fast.
The circuit status will normally be
Run: Disc SH Low
after the compressor starts.
OM WGS-5 WGS 130A to 190A 21
Page 22
Run Compressor
Next off?
Yes
Stage down now?
Yes
When in the Run state, the compressor will load/unload as needed to satisfy the
load. The compressor will also load/unload to load balance with the other
compressor if it is running and not in a limited condition. However, it cannot load up
until the discharge superheat has been over 22 F for at least 30 seconds. After this,
the circuit status will be
Run:Normal
.
The EXV will operate in either Pressure Control or Superheat Control. In Pressure
Control, the evaporator pressure is controlled to a target pressure, which is adjusted
based on LWT and discharge superheat. In Superheat Control, the suction
superheat is controlled to a target that varies with discharge superheat.
No
If unit is aircooled, fans will be staged on and off to control the condenser pressure.
The condenser pressure is controlled to a target that is based on evaporator
pressure, with the target getting higher as the evaporator pressure gets higher.
No
If this compressor has the most run hours or the other compressor is already off,
then this compressor will be designated as the next one off.
If less cooling capacity is needed, the compressor designated as next off can shut
down. This condition may arise when either the LWT has dropped far enough below
the active set point or both circuits are running at a low capacity.
When the circuit does a normal shutdown, a pumpdown is performed. The EXV is
closed while the compressor continues to run. As soon as the pumpdown is
initiated, the compressor is unloaded to the minimum. The condenser fans
continue to control normally during this process. The circuit status during this time
Run:Pumpdown
is
.
Pumpdown circuit
After the evaporator pressure drops below the pumpdown pressure or enough time
has passed, the compressor and fans are shut off to end the pumpdown process.
The circuit status will normally be
Off:Cycle Timers
at this time.
22 WGS 130A to 190A OM WGS-5
Page 23
Start-Up and Shutdown
Pre Start-up
1. Flush and clean the chilled-water system. Proper water treatment is required to prevent
corrosion and organic growth. A 20-mesh strainer is required at the evaporator chilledwater inlet and should be cleaned after system flushing.
Failure to flush, clean and provide system water treatment can damage the unit.
2. With the main disconnect open, check all electrical connections in control panel and
starter to be sure they are tight and provide good electrical contact. Connections are
tightened at the factory, but can loosen enough in shipment to cause a malfunction.
Lock and tag out all power sources when checking connections. Electrical shock
can cause severe personal injury or death..
3. Check and inspect all water piping. Make sure flow direction is correct and that piping
is made to the correct connection on evaporator and condenser.
4. Check that refrigerant piping on remote condensers is connected to the correct circuits
and not crossed and has been properly leak tested and evacuated.
5. Open all water flow valves to the condenser and evaporator.
6. Flush the cooling tower and system piping to be sure the system is clean. Start
evaporator pump and manually start condenser pump and cooling tower. Check all
piping for leaks. Vent the air from the evaporator and condenser water circuit, as well
as from the entire water system. The cooler circuit should contain clean, treated, noncorrosive water.
7. Check to see that the evaporator water temperature sensor is securely installed.
8. Make sure the unit control switch S1 is open OFF and the circuit switches CS1 and CS2
are open. Place the main power disconnect switch to ON. This will energize the
compressor sump heaters. Wait a minimum of 12 hours before starting the unit.
9. Measure the water pressure drop across the evaporator and condenser, and check that
water flow is correct (on pages 26 and 27) per the design flow rates.
10. Check the actual line voltage to the unit to m
compressor nameplate, within + 10%, and that phase voltage unbalance does not exceed
2%. Verify that adequate power supply and capacity is available to handle load.
11. Make sure all wiring and fuses are of the proper size. Also make sure that all interlock
wiring is completed per McQuay diagrams.
12. Verify that all mechanical and electrical inspections by code authorities have been
completed.
13. Make sure all auxiliary load and control equipment is operative and that an adequate
cooling load is available for initial start-up.
!
CAUTION
!
CAUTION
ake sure it is the same as called for on the
Start-up
1. Open the compressor discharge shutoff valves until backseated. Replace valve seal
caps.
2. Open the two manual liquid line shutoff valves (king valves).
OM WGS-5 WGS 130A to 190A 23
Page 24
3. Verify that the compressor sump heaters have operated for at least 12 hours prior to
start-up. Crankcase should be warm to the touch.
4. Check that the MicroTech II controller is set to the desired chilled water temperature.
5. Start the system auxiliary equipment for the installation by turning on the time clock,
ambient thermostat and/or remote on/off switch and water pumps.
6. Switch on the unit circuit breakers.
7. Set circuit switches CS1 and CS2 to ON for normal operation.
8. Start the system by setting the unit system switch S1 to ON.
9. After running the unit for a short time, check the oil level in each compressor, rotation
of condenser fans (if any), and check for flashing in the refrigerant sight glass.
Weekend or Temporary Shutdown
Move circuit switches CS1 and CS2 to the OFF pumpdown position. After the compressors
have shut off, turn off the chilled water pump if not on automatic control from the chiller
controller or building automation system (BAS). With the unit in this condition, it will not
restart until these switches are turned back on.
Leave on the power to the unit (disconnect closed) so that the sump heaters will remain
energized.
Start-up after Temporary Shutdown
1. Start the water pumps.
2. Check compressor sump heaters. Compressors should be warm to the touch.
3. With the unit switch S1 in the ON position, move the circuit switches CS1 and CS2 to
the ON position.
4. Observe the unit operation for a short time, noting unusual sounds or possible cycling of
compressors.
Extended Shutdown
1. Close the manual liquid line shutoff valves.
2. After the compressors have shut down, turn off the water pumps.
3. Turn off all power to the unit.
4. Move the unit control switch S1 to the OFF position.
5. Close the discharge shutoff valves.
6. Tag all opened disconnect switches to warn against start-up before opening the
compressor suction and discharge valves.
7. Drain all water from the unit evaporator, condenser and chilled water piping if the unit
is to be shut down during the winter and exposed to below-freezing temperatures. To
help prevent excessive corrosion, do not leave the vessels or piping open to the
atmosphere over the shutdown period.
24 WGS 130A to 190A OM WGS-5
Page 25
Start-up after Extended Shutdown
1. Inspect all equipment to see that it is in satisfactory operating condition.
2. Remove all debris that has collected on the surface of the condenser coils (remote
condenser models) or check the cooling tower, if present.
3. Open the compressor discharge valves until backseated. Always replace valve seal
caps.
4. Open the manual liquid line shutoff valves.
5. Check circuit breakers. They must be in the OFF position.
6. Check to see that the circuit switches CS1 and CS2 and the unit control switch S1 are in
the OFF position.
7. Close the main power disconnect switch. The circuit disconnects switches should be
off.
8. Allow the sump heaters to operate for at least 12 hours prior to start-up.
9. Start the chilled water pump and purge the water piping as well as the evaporator in the
unit.
10. Start the system auxiliary equipment for the installation by turning on the time clock,
ambient thermostat and/or remote on/off switch.
11. Check that the MicroTech II controller is set to the desired chilled water temperature.
12. Switch the unit circuit breakers to ON.
13. Start the system by setting the system switch S1 and the circuit switches to ON.
!
CAUTION
Most relays and terminals in the control center are powered when S1 is closed and the
control circuit disconnect is on. Therefore, do not close S1 until ready for start-up or serious
equipment damage can occur.
14. After running the unit for a short time, check the oil level in the compressor oil sight
glass and check the liquid line sight glass for bubbles.
OM WGS-5 WGS 130A to 190A 25
Page 26
Figure 7, Evaporator Pressure Drop WGS 130 – WGS 190
Flow Rate (L/s)
6131925323844505763
60
126
180
50
40
30
20
10
9
8
Pressure Drop (ft of water)
7
6
5
WGS 130, 140
WGS 160, 170, 190
150
120
90
60
30
27
24
21
18
15
Pressure Drop (kPa)
4
3
100 200 300 400 500 600 700
800
900
1000
12
9
2000
Flow Rate (GPM)
Minimum Flow Nominal Flow Maximum Flow
WGS Model
130AW/AA
140AW/AA
160AW/AA
170AW/AA
190AW/AA
Note: Minimum, nominal, and maximum flows are at a 16F, 10F, and 6F chilled water temperature range respectively and at ARI tons.
Flow Rate Pressure Drop Flow Rate Pressure Drop Flow Rate Pressure Drop
gpm L/s Ft. kPa gpm L/s Ft. kPa gpm L/s Ft. kPa
195 12.3 5.8 17.4 312 19.7 13.5 40.4 520 32.9 33.9 101.1
211 13.4 6.7 20.0 338 21.4 15.6 46.6 563 35.6 39.0 116.5
235 14.9 4.6 13.8 376 23.8 10.8 32.3 627 39.7 27.3 81.6
254 16.1 5.3 15.9 407 25.8 12.5 37.3 678 42.9 31.6 94.2
273 17.3 6.1 18.1 437 27.7 14.2 42.5 728 46.1 35.9 107.2
26 WGS 130A to 190A OM WGS-5
Page 27
Figure 8, Condenser Pressure Drop WGS 130 – WGS 190
)
)
Flow Rate (L/s
6131925323844505763
60
126
180
Pressure Drop (ft of water)
WGS
Model
130AW
140AW
160AW
170AW
190AW
WGS
Model
130AW
140AW
160AW
170AW
190AW
50
40
WGS 170, 190
150
120
with Manifold
30
90
WGS 130, 140, 160
with Manifold
20
10
9
8
7
6
5
WGS 170, 190
60
30
27
24
21
18
15
without Manifold
4
12
WGS 130, 140, 160
3
100 200 300 400 500 600 700
without Manifold
800
900
1000
9
2000
Flow Rate (GPM
Pressure Drop Without Optional Condenser Manifold
Minimum Flow Nominal Flow Maximum Flow
Flow Rate Pressure Drop Flow Rate Pressure Drop Flow Rate Pressure Drop
gpm L/s Ft. kPa gpm L/s Ft. kPa gpm L/s Ft. kPa
304 19.2 4.1 12.2 390 24.7 6.5 19.3 650 41.1 16.0 47.9
304 19.2 4.1 12.2 422 26.7 7.4 22.2 704 44.5 18.5 55.1
304 19.2 4.1 12.2 470 29.8 9.0 26.9 784 49.6 22.4 66.8
372 23.5 4.3 12.8 509 32.2 7.9 23.7 848 53.7 19.8 59.1
372 23.5 4.3 12.8 546 34.6 9.0 26.9 911 57.6 22.5 67.1
Pressure Drop With Optional Condenser Manifold
Minimum Flow Nominal Flow Maximum Flow
Flow Rate Pressure Drop Flow Rate Pressure Drop Flow Rate Pressure Drop
gpm L/s Ft. kPa gpm L/s Ft. kPa gpm L/s Ft. kPa
304 19.2 4.7 14.0 390 24.7 7.4 22.0 650 41.1 18.5 55.1
304 19.2 4.7 14.0 422 26.7 8.5 25.3 704 44.5 21.3 63.5
304 19.2 4.7 14.0 470 29.8 10.3 30.7 784 49.6 25.8 77.1
372 23.5 5.3 15.8 509 32.2 9.4 28.1 848 53.7 23.8 71.1
372 23.5 5.3 15.8 546 34.6 10.7 32.0 911 57.6 27.1 80.9
Pressure Drop (kPa)
OM WGS-5 WGS 130A to 190A 27
Page 28
Unit Controller
Unit Inputs/Outputs
Table 1, Analog Inputs
# Description Signal Source Range
1
2
3
4
5
C1 = Refrigerant Circuit #1, C2 = Refrigerant Circuit #2, UT = Unit
Table 2, Analog Outputs
# Description Output Signal Range
1
2
3
4
Table 3, Digital Inputs
# Description Signal Signal
1
2
3
4
5
6
7
8
Condenser EWT or Outdoor
Ambient Temp.
Demand Limit 4-20 mA Current 0 to 100% limit
Chilled Water Reset 4-20 mA Current
Leaving Evaporator Water Temp. Thermister (10k@25°C) -58 to 212°F
Entering Evaporator Water Temp. Thermister (10k@25°C) -58 to 212°F
Cooling Tower Bypass Valve Position 0 to 10 VDC 0 to 100%
Cooling Tower VFD Speed 0 to 10 VDC 0 to 100%
Open
Open
Unit Switch 0 VAC (Stop) 24 VAC (On)
Remote Switch 0 VAC (Stop) 24 VAC (Start)
Evaporator Water Flow Switch 0 VAC (No Flow) 24 VAC (Flow)
Mode Switch 0 VAC (Cool) 24 VAC (Ice)
Condenser Water Flow Switch 0 VAC (No Flow) 24 VAC (Flow)
Open
Open
Open
Thermister (10k@25°C) -58 to 212°F
0 to 10 degrees
60F max.
Table 4, Digital Outputs
# Description Load Output OFF Output ON
Evaporator Water Pump 1 Pump Contactor Pump OFF Pump ON
1
Evaporator Water Pump 2 Pump Contactor Pump OFF Pump ON
2
Condenser Water Pump 1 Pump Contactor Pump OFF Pump ON
3
Condenser Water Pump 2 Pump Contactor Pump OFF Pump ON
4
Tower Fan 1 Fan Contactor Fan OFF Fan ON
5
Tower Fan 2 Fan Contactor Fan OFF Fan ON
6
Remote Run Status All Circuits Off Any Circuit On
7
Alarm Remote Alarm No alarm Stop alarm
8
Unit Setpoints
The following parameters are retained during power off, are factory set to the Default value,
and can be adjusted to any value in the Range column.
The Type defines whether the setpoint is part of a coordinated set of duplicate setpoints in
different controllers. Types are as follows:
N = Normal setpoint – Not copied from, or copied to, any other controller
M = Master setpoint – Setpoint is copied to all controllers in the “Sent To” column
The PW (password) column indicates the password level that must be active in order to
change the setpoint. Passwords are as follows:
O = Operator [0100] M = Manager (8745)
28 WGS 130A to 190A OM WGS-5
Page 29
Toggle: Setpoints that have two choices, such as ON and OFF are toggled between the two
settings using the Up or Down keys on the controller.
NOTE: in some software versions the terms “inhibit” and “hold” are used interchangeably.
Table 5, Unit Controller Setpoints
Description Default Range Type PW
Unit
Unit Enable OFF OFF, ON N O
Unit Mode Cool Cool, Ice, Test M O
Control source Switches Switches, Keypad, Network N O
Available Modes Cool
Cool LWT
Ice LWT
Start Delta T
Stop Delta T
Stage Up Delta T
Stage Down Delta T
Max Pulldown
Evap Recirc Timer 30 0 to 300 seconds N M
Evap Pump Select #1 Only #1 Only, #2 Only, Auto N M
Water-cooled Yes No, Yes N M
Cond Recirc Timer (water-
cooled only)
Cond Pump Select (watercooled only)
LWT Reset Type NONE NONE, RETURN, 4-20mA, OAT N M
Max Reset
Start Reset Delta T
Soft Load Off Off, On N M
Begin Capacity Limit 40% 20-100% N M
Soft Load Ramp 20 min 1-60 minutes N M
Demand Limit Off Off, On N M
Low OAT Operation
(air-cooled only)
Low Ambient Lockout (air
cooled only)
Ice Time Delay 12 1-23 hours N M
Clear Ice Timer No No,Yes N M
Evap LWT sensor offset 0 -5.0 to 5.0 deg N M
Evap EWT sensor offset 0 -5.0 to 5.0 deg N M
Cond EWT/OAT sensor offset 0 -5.0 to 5.0 deg N M
Cond LWT sensor offset 0 -5.0 to 5.0 deg N M
Units
BAS Protocol Modbus BACnet, LonWorks, Modbus N M
Ident number 1 0-200 N M
Baud Rate 19200 1200,2400,4800,9600,19200 N M
Compressors
Sequence # Cir 1 1 1-2 M M
Sequence # Cir 2 1 1-2 M M
Max Comps ON 2 1-2 N M
Start-start timer 20 min 15-60 minutes M M
Stop-start timer 5 min 3-20 minutes M M
Pumpdown Pressure 25 psi 10 to 40 psi M M
Pumpdown Time Limit 120 sec 0 to 180 sec M M
Light Load Stg Dn Point 25% 20 to 50% M M
44 F 30(40) to 60 F
25 F 20 to 38F
10 F 0 to 10 F
1.5 F 0 to 3 F
2 F 0 to 3 F
1 F 0 to 3 F
5 F/min 0.5-5.0 F /min
30 0 to 300 seconds N M
#1 Only #1 Only, #2 Only, Auto N M
0 F 0 to 20 F
10 F 0 to 20 F
No No, Yes N M
55 F -10(35) to 70 F
F/psi F/psi, C/kPa
Continued next page.
Cool, Cool w/Glycol, Cool/Ice
w/Glycol, ICE w/Glycol, TEST
N T
N O
N O
M O
M O
M O
M O
M M
N M
N M
N M
N M
OM WGS-5 WGS 130A to 190A 29
Page 30
Description Default Range Type PW
Stage Up Delay 5 min 0 to 60 min M M
Disc. Temp Sensor Type PT1000 NTC, PT1000 M M
Alarms
Low Evap Pressure-Unload 28 psi [0,26] to 45 psi M M
Low Evap Pressure-Hold 30 psi [0,28] to 45 psi M M
Low Oil Level Delay 120 sec 10-180 sec M M
High Oil Press Diff Delay 15 sec 0-90 sec M M
High Discharge Temperature
High Lift Pressure Delay 5 sec 0 to 30 sec M M
Evaporator Water Freeze
Evaporator Flow Proof 3 sec 3 to 10 sec N M
Recirculate timeout 3 min 1 to 10 min. N M
Startup Timer 60 sec 20 to 90 sec. M M
Condenser Water Freeze
(water cooled only)
Condenser Flow Proof (water
cooled only)
Cooling Tower(available for Water cooled only)
Tower Control None None, Temperature N M
Tower Stages 2 0 to 2 N M
Stage #1 On
Stage #2 On
Stage Differential
Stage Up Time 2 min 1 to 60 min N M
Stage Down Time 5 min 1 to 60 min N M
Stage Fan Down @ 20% 0 to 100% N M
Stage Fan Up @ 80% 0 to 100% N M
Valve/VFD Control None
Valve Type NC to tower NC, NO N M
Valve Setpoint
Valve Deadband
Minimum Start Position 0% 0 to 100% N M
Minimum Position @
Maximum Start Position 100% 0 to 100% N M
Maximum Position @
Valve Control Range (Min) 10% 0 to 100% N M
Valve Control Range(Max) 90% 0 to 100% N M
Error Gain 25 10 to 99 N M
Slope Gain 25 10 to 99 N M
200 F
36 F 15(36) to 42 F
38 F 34 to 42 F
3 sec 3 to 10 sec N M
70 F 40 to 120 F
75 F 40 to 120 F
3.0 F 1.0 to 10.0 F
None, Valve Setpoint, Valve Stage,
VFD Stage, Valve SP/VFD Stage
65 F 60 to 120 F
2.0 F 1.0 to 10.0 F
60 F 0 to 100 F
90 F 0 to 100 F
150 to 200 F M M
N M
N M
N M
N M
N M
N M
N M
N M
N M
N M
Auto Adjusted Ranges
The following settings have different ranges of adjustment based on other settings.
Table 6, Cool LWT
Unit Mode = Cool 40 to 60oF
Unit Mode = Cool w/Glycol, Ice w/ Glycol 20 to 60oF
Table 7, Evaporator Water Freeze
Unit Mode = Cool 34 to 42oF
Unit Mode = Cool w/Glycol, Ice w/ Glycol 15 to 42oF
30 WGS 130A to 190A OM WGS-5
Mode Range
Mode Range
Page 31
Table 8, Low Evaporator Pressure Inhibit
Unit Mode = Cool 30 to 45 Psig
Unit Mode = Cool w/Glycol, Ice w/ Glycol 15 to 45 Psig
Table 9, Low Evaporator Pressure Unload
Unit Mode = Cool 28 to 45 Psig
Unit Mode = Cool w/Glycol, Ice w/ Glycol 15 to 45 Psig
Circuit Controller
Circuit Inputs and Outputs
Table 10, Analog Inputs
# Description Signal Source Range
1 Evaporator Pressure 0.1 to 0.9 VDC
2 Condenser Pressure 0.1 to 0.9 VDC
3 Open
4 Suction Temperature NTC Thermister (10k@25°C) -58 to 212°F
5 Discharge Temperature NTC Thermister (10k@25°C) -58 to 212°F
6 Open
7 Slide Load Indicator 4 to 20 mA
8 Condenser LWT (circuit 1, water cooled only) NTC Thermister (10k@25°C) -58 to 212°F
Mode Range
Mode Range
0 to 132 psi
3.6to 410 psi
0 to 100%
Table 11, Analog Outputs
# Description Output Signal Range
1 Fan VFD (air cooled only) 0 to 10 VDC 0 to 100% (1000 steps resolution)
2 Open
3 EXV Driver 0 to 10 VDC 0 to 6386 steps (1000 steps resolution)
4 Open
Table 12, Digital Inputs
# Description Signal Signal
1 Circuit Switch 0 VAC (Off) 24 VAC (Auto)
2 Open
3 Open
4 VFD Fault 0 VAC (Fault) 24 VAC (No Fault)
5 Oil Differential Pressure Switch 0 VAC (Fault) 24 VAC (No Fault)
6 Mechanical High Pressure Switch 0 VAC (Fault) 24 VAC (No Fault)
7 Open
8 Open
9 Oil Level Sensor 0 VAC (Fault) 24 VAC (No Fault)
10-14 Open
The status of digital inputs may be viewed on Circuit Status screen 5, on the circuit
controllers only.
OM WGS-5 WGS 130A to 190A 31
Page 32
Table 13, Digital Outputs
# Description Output OFF Output ON
1 Fan 1 Contactor (air cooled only) Fan off Fan on
2 Fan 2 Contactor (air cooled only) Fan off Fan on
3 Fan 3 Contactor (air cooled only) Fan off Fan on
4 Fan 4 Contactor (air cooled only) Fan off Fan on
5 Fan 5 Contactor (air cooled only) Fan off Fan on
6 Fan 6 Contactor (air cooled only) Fan off Fan on
7 Load/Unload Pulse Hold load slide Move load slide
8 Load/Unload Select Unload Load
9 Compressor SSS Contact Compressor off Compressor on
10 Open
11 Oil Heater Heater off Heater on
12 Interstage Injection (future use) Injection off Injection on
13 EXV Close Signal
EXV follows
0 –10 VDC
EXV closed, ignores 0 –
10 VDC
Circuit Setpoint Table
The following parameters must be remembered during power off, are factory set to the
Default value, and can be adjusted to any value in the Range column.
The PW (password) column indicates the password that must be active in order to change
the setpoint. Codes are as follows:
O = Operator (100) M = Manager
Table 14, Circuit Setpoints
Description Default Range PW
Compressor
Circuit Mode enable Disable, enable, test M
Slide Control auto Auto, manual M
Slide target 0 0-100 M
Compressor Size 167 167, 179, 197 M
Clear Cycle Timers No No, Yes M
Full Load Amps 10 1 to 341 amps M
Rated load Amps 10 1 to 341 amps M
Service Factor 125% 100 to 199% M
Ground Fault Enable Disable Disable, enable M
Ground Fault Trip Level 1% 1 to 100% M
Overload Class 10 0 to 40 M
Initial Motor Current 225% 50 to 400% FLA M
Maximum Motor Current 300% 100 to 800% M
Ramp Time 7 seconds 0 to 300 seconds M
Up to Speed Time (UTS) 10 seconds 1 to 900 seconds M
Stop Mode CoS Coast(CoS), volt decel(dcL) M
Rated RMS Voltage 460 volts 100 to 1000 volts M
Over Voltage Trip Level 10% 1 to 40% rated volts M
Under Voltage Trip Level 10% 1 to 40% rated volts M
Ovr/Undr Volt Trip Delay 1.0 seconds 0.1 to 90.0 seconds M
Current Unbalance Trip Level 15% 5 to 40% M
Auto Fault Reset Time 60 seconds 0 to 120 seconds M
CT Ratio 864:1 72-8000:1 M
Maximum Slide Target 100.0 0-100.0% M
Continued next page
32 WGS 130A to 190A OM WGS-5
Page 33
Description Default Range PW
EXV
EXV control Auto Auto, manual M
Manual EXV position 0 0-6386 M
Service Pumpdown No No,Yes M
Preopen Timer (water cooled only) 20 20 to 120 seconds M
Sensors (NOTE 1)
Evap pressure offset 0 -10.0 to 10.0 psi M
Cond pressure offset 0 -10.0 to 10.0 psi M
Suction temp offset 0 -5.0 to 5.0 deg M
Discharge temp offset 0 -5.0 to 5.0 deg M
Slide Minimum Position Offset 0 -15 to 15% M
Slide Maximum Position Offset 0 -15 to 15% M
Fans (available for air-cooled only)
Fan VFD enable On Off, On M
Number of fans 4 4 to 6 M
Saturated Condenser Temp Target Min 90.0 80.0-110.0
Saturated Condenser Temp Target Max 110.0 90.0-120.0 oF M
Stage 1 On Deadband 8.0 1.0-20.0 oF M
Stage 2 On Deadband 10.0 1.0-20.0 oF M
Stage 3 On Deadband 11.0 1.0-20.0 oF M
Stage 4 On Deadband 12.0 1.0-20.0 oF M
Stage 2 Off Deadband 20.0 1.0-25.0 oF M
Stage 3 Off Deadband 16.0 1.0-25.0 oF M
Stage 4 Off Deadband 11.0 1.0-25.0 oF M
Stage 5 Off Deadband 8.0 1.0-25.0 oF M
VFD Max Speed 100% 90 to 110% M
VFD Min Speed 25% 20 to 60% M
Forced Fantrol 1 2 1 to 4 M
Forced Fantrol 2 3 1 to 4 M
Forced Fantrol 3 4 1 to 4 M
o
F M
Notes:
1. Offsets are used to fine-tune certain readings generated by sensors. For example, if the controller was
showing a 125 psi value and a calibrated pressure gauge at the same location showed 127 psi, an offset of
+2 psi would be entered and the controller would then read the corrected value of 127 psi.
Table 15, RLA/FLA Values
Compressor 575V 460V 380V 230V 208V 400V (50Hz)
RLA
197
179
167
All
NOTE: Table values used for circuit controller input.
113 141 178 282 312 141
94 122 145 240 267 122
85 112 128 210 232 112
FLA
113 141 178 282 312 141
OM WGS-5 WGS 130A to 190A 33
Page 34
Alarms and Events
Situations may arise that require some action from the chiller or that should be logged for
future reference. A condition that causes a shutdown and requires manual reset is known as
a stop alarm. Other conditions can trigger what is known as an event, which may or may
not require an action in response. All stop alarms and events are logged.
Unit Stop Alarms
The alarm output and red button led shall be turned ON when any stop alarm occurs. They
shall be turned off when all alarms have been cleared.
Evaporator Flow Loss
Alarm description (as shown on screen): Evap Water Flow Loss
Trigger:
1: Evaporator Pump State = Run AND Evaporator Flow Digital Input = No Flow for time >
Flow Proof Set Point AND at least one compressor running
2: Evaporator Pump State = Start for time greater than Recirc Timeout Set Point and all
pumps have been tried
Action Taken: Rapid stop all circuits
Reset: This alarm can be cleared at any time manually via the keypad or via the BAS clear
alarm signal.
If active via trigger condition 1
When the alarm occurs due to this trigger, it can auto reset the first two times each day, with
the third occurrence being manual reset.
For the auto reset occurrences, the alarm will reset automatically when the evaporator state
is Run again. This means the alarm stays active while the unit waits for flow, then it goes
through the recirculation process after flow is detected. Once the recirculation is complete,
the evaporator goes to the Run state which will clear the alarm. After three occurrences, the
count of occurrences is reset and the cycle starts over if the manual reset flow loss alarm is
cleared.
If active via trigger condition 2:
If the flow loss alarm has occurred due to this trigger, it is always a manual reset alarm.
:
Condenser Flow Loss
Alarm description (as shown on screen): Cond Water Flow Loss
Trigger:
1: Condenser Pump State = Run AND Condenser Flow Digital Input = No Flow for time >
Flow Proof Set Point AND at least one compressor running
2: Condenser Pump State = Start for time greater than Recirc Timeout Set Point and all
pumps have been tried
Action Taken: Rapid stop all circuits
Reset: This alarm can be cleared at any time manually via the keypad or via the BAS clear
alarm signal.
If active via trigger condition 1
34 WGS 130A to 190A OM WGS-5
:
Page 35
The alarm will reset automatically when the condenser state is Run again. This means the
alarm stays active while the unit waits for flow, then it goes through the recirculation
process after flow is detected. Once the recirculation is complete, the condenser goes to the
Run state which will clear the alarm.
If active via trigger condition 2:
If the flow loss alarm has occurred due to this trigger, it is always a manual reset alarm.
Evaporator Water Freeze Protect
Alarm description (as shown on screen): Evap Water Freeze
Trigger: Evaporator LWT drops below evaporator freeze protect set point AND Unit State
= Auto AND Evaporator LWT Sensor Fault not active
Action Taken: Rapid stop all circuits
Reset: This alarm can be cleared manually via the keypad or via the BAS clear alarm
signal, but only if the alarm trigger conditions no longer exist.
Leaving Evaporator Water Temperature Sensor Fault
Alarm description (as shown on screen): Evap LWT Sens Fault
Trigger: Sensor shorted or open
Action Taken: Rapid stop all circuits
Reset: This alarm can be cleared manually via the keypad, but only if the sensor is back in
range.
Entering Condenser Water Temperature Sensor Fault
Alarm description (as shown on screen): Cond EWT Sens Fault
Trigger: Sensor shorted or open
Action Taken: Rapid stop all circuits
Reset: This alarm can be cleared manually via the keypad, but only if the sensor is back in
range.
Outdoor Air Temperature Sensor Fault
Alarm description (as shown on screen): OAT Sensor Fault
Trigger: Sensor shorted or open AND unit is aircooled
Action Taken: Rapid stop all circuits
Reset: This alarm can be cleared manually via the keypad, but only if the sensor is back in
range.
pLAN Failure
Alarm description (as shown on screen): pLAN Failure
Trigger: No circuit controllers found on pLAN for 60 seconds
Action Taken: Rapid stop all circuits
Reset: This alarm can be cleared manually via the keypad, but only if at least one circuit is
connected to pLAN.
OM WGS-5 WGS 130A to 190A 35
Page 36
Unit Events
The following unit events are logged in the event log with a time stamp.
Entering Evaporator Water Temperature Sensor Fault
Event description (as shown on screen): Evap EWT Sens Fault
Trigger: Sensor shorted or open
Action Taken: Return water reset cannot be used.
Reset: Auto reset when sensor is back in range.
Leaving Condenser Water Temperature Sensor Fault
Event description (as shown on screen): Cond LWT Sens Fault
Trigger: Sensor shorted or open AND unit is watercooled
Action Taken: None
Reset: Auto reset when sensor is back in range.
Circuit Stop Alarms
All circuit stop alarms require shutdown of the circuit on which they occur. Rapid stop
alarms do not do a pumpdown before shutting off. All other alarms will do a pumpdown.
The red button led on the circuit controller shall be turned on when any circuit stop alarm
occurs. It shall be turned off when all circuit alarms have been cleared. In addition, the
alarm status shall be sent to the unit control so the alarm output and the red button led on the
unit controller can be energized while alarms are active.
Alarm descriptions apply to both circuits, the circuit number is represented by ‘N’ in the
description.
Low Evaporator Pressure
Alarm description (as shown on screen): Evap Press Low N
Trigger: [Freezestat trip AND Compressor State = Run AND Low OAT Start not active
AND Evap Pressure Sensor Fault not active] OR [Evaporator Press < -10 psi AND startup
timer complete AND Evap Pressure Sensor Fault not active] and the compressor has been
running longer than the Startup Timer setting
Freezestat logic allows the circuit to run for varying times at low pressures. The lower the
pressure, the shorter the time the compressor can run. This time is calculated as follows:
Freeze error = Low Evaporator Pressure Unload – Evaporator Pressure
Freeze time = 70 – 6.25 x freeze error, limited to a range of 20-70 seconds
When the evaporator pressure goes below the Low Evaporator Pressure Unload set point, a
timer starts. If this timer exceeds the freeze time, then a freezestat trip occurs. If the
evaporator pressure rises to the unload set point or higher, and the freeze time has not been
exceeded, the timer will reset.
Action Taken: Rapid stop circuit
Reset: This alarm can be cleared manually via the Unit Controller keypad if the evaporator
pressure is above –10 psi.
36 WGS 130A to 190A OM WGS-5
Page 37
High Lift Pressure
Alarm description (as shown on screen): Lift Pressure High N
Trigger: Condenser Saturated Temperature > Max Saturated Condenser Value for time >
High Lift Delay set point
Action Taken: Rapid stop circuit
Reset: This alarm can be cleared manually via the Unit Controller keypad.
Mechanical High Pressure
Alarm description (as shown on screen): Mech High Pressure N
Trigger: Mechanical High Pressure switch input is low
Action Taken: Rapid stop circuit
Reset: This alarm can be cleared manually via the Unit Controller keypad if the MHP
switch input is high.
High Discharge Temperature
Alarm description (as shown on screen): Disc Temp High N
Trigger: Discharge Temperature > High Discharge Temperature set point AND compressor
is running AND Discharge Temperature Sensor Fault is not active
Action Taken: Rapid stop circuit
Reset: This alarm can be cleared manually via the Unit Controller keypad.
Low Oil Level
Alarm description (as shown on screen): Oil Level Low N
Trigger: Oil Level Switch input is open for time greater than Low Oil Level Delay while
compressor is in the Run state AND the Low Oil Level Event has occurred in the past hour.
Action Taken: Rapid stop circuit
Reset: This alarm can be cleared manually via the Unit Controller keypad.
High Oil Pressure Difference
Alarm description (as shown on screen): Oil Pres Diff High N
Trigger: Oil DP switch input is low for time greater than High Oil Pressure Difference
Delay set point AND compressor is running
Action Taken: Rapid stop circuit
Reset: This alarm can be cleared manually via the Unit Controller keypad.
Low Evaporator Pressure Start
Alarm description (as shown on screen): LowPress StartFail N
Trigger: Saturated condenser temperature greater than 70°F at start and circuit failed a Start Logic
attempt.
Action Taken: Rapid stop circuit
Reset: This alarm can be cleared manually via the Unit Controller keypad.
No Evaporator Pressure Drop After Start
Alarm description (as shown on screen): No Evap Press Drop N
Trigger: After start of compressor, at least a 1 psi drop in evaporator pressure has not
occurred after 15 seconds
Action Taken: Rapid stop circuit
Reset: This alarm can be cleared manually via the Unit Controller keypad.
OM WGS-5 WGS 130A to 190A 37
Page 38
No Pressure Change At Start
Alarm description (as shown on screen): NoPressChgAtStart N
Trigger: After start of compressor, at least a 1 psi drop in evaporator pressure or 5 psi rise
in discharge pressure has not occurred after 15 seconds.
Action Taken: Rapid stop circuit
Reset: This alarm can be cleared manually via the Unit Controller keypad.
Circuit Events
The following events limit operation of the circuit in some way as described in the Action
Taken column. The occurrence of a circuit event only affects the circuit on which it
occurred. Circuit events
Low Evaporator Pressure - Hold
Event description (as shown on screen): EvapPress Low Hold N
trigger: The low pressure events are not enabled until the compressor has started and the
evaporator pressure has risen above the Low Evaporator Pressure - Hold set point. The unit
mode must also be Cool. Then, while running, if evaporator pressure <= Low Evaporator
Pressure - Hold set point the event is triggered.
Action Taken: Inhibit loading by only allowing the slide target to be reduced.
Reset: While still running, the event will be reset if evaporator pressure > (Low Evaporator
Pressure - Hold SP + 2psi). The event is also reset if the unit mode is switched to Ice, or the
compressor state is no longer Run.
are logged in the event log on the unit controller.
Low Evaporator Pressure - Unload
Event description (as shown on screen): EvapPressLowUnload N
Trigger: The low pressure events are not enabled until the compressor has started and the
evaporator pressure has risen above the Low Evaporator Pressure - Hold set point. The unit
mode must also be Cool. Then, while running, if evaporator pressure <= Low Evaporator
Pressure - Unload set point the event is triggered.
Action Taken: Unload the compressor by decreasing the slide target 5% every five seconds
until the evaporator pressure rises above the Low Evaporator Pressure – Unload set point.
Reset: While still running, the event will be reset if evaporator pressure > (Low Evaporator
Pressure - Hold SP + 2psi). The event is also reset if the unit mode is switched to Ice, or the
compressor state is no longer Run.
High Lift Pressure - Hold
Event description (as shown on screen): LiftPressHigh Hold N
Trigger: While the compressor is running and unit mode is Cool, if saturated condenser
temperature >= High Saturated Condenser - Hold Value, the event is triggered.
Action Taken: Inhibit loading by only allowing the slide target to be reduced.
Reset: While still running, the event will be reset if saturated condenser temperature <
(High Saturated Condenser - Hold Value – 10
switched to Ice, or the compressor state is no longer Run.
o
F). The event is also reset if the unit mode is
High Lift Pressure - Unload
Event description (as shown on screen): LiftPressHighUnloadN
Trigger: While the compressor is running and unit mode is Cool, if saturated condenser
temperature >= High Saturated Condenser - Unload Value, the event is triggered.
Action Taken: Unload the compressor by decreasing the slide target 5% every five seconds
until the condenser pressure drops below the High Saturated Condenser - Unload Value.
38 WGS 130A to 190A OM WGS-5
Page 39
Reset: While still running, the event will be reset if saturated condenser temperature <
(High Saturated Condenser - Unload Value – 10
o
F). The event is also reset if the unit mode
is switched to Ice, or the compressor state is no longer Run.
Oil Level Low
Event description (as shown on screen): Oil Level Low Cir N
Trigger: Oil Level Switch input is open for time greater than Low Oil Level Delay while
compressor is in the Run state AND the Low Oil Level Event has not occurred in the past
hour.
Action Taken: Rapid stop circuit
Reset: Compressor state = off
Failed Pumpdown
Event description (as shown on screen): Pumpdown Fail Cir N
Trigger: Circuit state = pumpdown for time > Pumpdown Time set point
Action Taken: Shutdown circuit
Reset: N/A
Power Loss While Running
Event description (as shown on screen): Run Power Loss Cir N
Trigger: Circuit controller is powered up after losing power while compressor was running
Action Taken: Delay start of compressor by time equal to the Start-Start timer set point.
Reset: N/A
Condenser Freeze Protect
Event description (as shown on screen): Cond Frz Protect Cir N
Trigger: Cond Sat Refr Temp < Condenser Freeze SP AND Cond Pump State = Off AND
unit is watercooled
Action Taken: Start condenser pump
Reset: Cond Sat Refr Temp > Condenser Freeze SP + 2
o
F
VFD Fault
Event description (as shown on screen): VFD Fault Cir N
Trigger: VFD enabled and VFD fault input goes low
Action Taken: None
Reset: N/A
Slide Positioning Error
Event description (as shown on screen): Slide Pos Error Cir N
Trigger: [Slide Position > Slide Target + 25% OR Slide Position < Slide Target – 25%] for
time > 5 minutes
Action Taken: None
Reset: Circuit State = Off
Alarm Logging
When an alarm occurs, the alarm type, date, and time are stored in the active alarm buffer
corresponding to that alarm (viewed on the Alarm Active screens) and also in the alarm
history buffer (viewed on the Alarm Log screens). The active alarm buffers hold a record of
all current alarms. The active alarms can be cleared by pressing the Edit key when the end
of the list has been reached by scrolling. Active alarms may only be cleared if at least the
Operator password level is active.
OM WGS-5 WGS 130A to 190A 39
Page 40
A separate alarm log stores the last 25 alarms to occur. When an alarm occurs, it is put into
the first slot in the alarm log and all others are moved down one, dropping the last alarm. In
the alarm log, the date and time the alarm occurred are stored, as well as a list of other
parameters. These parameters include unit state, OAT, LWT, and EWT for all alarms. If the
alarm is a circuit alarm, then the circuit state, refrigerant pressures and temperatures, EXV
control state, EXV position, slide position, slide target, number of fans, and compressor run
time on are also stored.
Event Logging
An event log similar to the alarm log holds the last 25 events to occur. When an event
occurs, it is put into the first slot in the event log and all other entries are moved down one,
dropping the last event. Each entry in the event log includes an event description as well as
the time and date of the occurrence. No additional parameters are logged for events.
The event log shall only be accessible with the Manager password.
Clearing Alarms
Alarms may be cleared at the unit controller and no password is required. The BAS can
clear evaporator flow loss, evaporator water freeze and pLAN failure regardless of what
other alarms are active.
Unit Controller Functions
Calculations
LWT Slope
LWT slope is calculated such that the slope represents the change in LWT over a time frame
of one minute.
Every 12 seconds, the current LWT is subtracted from the value 12 seconds back. This
value is added to a buffer containing values calculated at the last five intervals. The final
result is a slope value that is an average over the past 60 seconds.
Pulldown Rate
The slope value calculated above will be a negative value as the water temperature is
dropping. For use in some control functions, the negative slope is converted to a positive
value by multiplying by –1.
Unit Capacity
Unit capacity is estimated based on the slide target of each running circuit. The capacity of
a running circuit is estimated with this equation:
Circuit capacity = 0.8(slide target) + 20
A circuit that is off is assumed to be at 0% capacity. The unit capacity is then calculated by
this equation:
Unit capacity = (Circuit 1 capacity + Circuit 2 capacity)/2
40 WGS 130A to 190A OM WGS-5
Page 41
Unit Enable
Enabling and disabling the chiller is controlled by the Unit Enable Setpoint with options of
OFF and ON. Enabling allows the unit to start if there is a call for cooling and also starts
the evaporator pump.
This setpoint (in other words, enabling the unit to run) can be altered by the:
Unit OFF input (unit On/Off switch)
a field installed remote stop switch
a keypad entry
a BAS request
The Control Source Setpoint determines which sources can change the Unit Enable Setpoint
with options of SWITCHES, KEYPAD or NETWORK.
Changing the Unit Enable Setpoint can be accomplished according to the following table.
NOTE: An “x” indicates that the entry is ignored.
Table 16, Unit Enable Combinations
Unit On/Off
Switch
OFF x x x x OFF
ON/OFF SWITCHES OFF x x OFF
ON SWITCHES ON x x ON
ON KEYPAD x OFF x OFF
ON KEYPAD x ON x ON
ON NETWORK x x OFF OFF
ON NETWORK OFF x x OFF
ON NETWORK ON x ON ON
Control Source
Setpoint
Remote
Stop Switch
Key-pad
Entry
BAS
Request
Resultant
Unit Enable
Status
Example:
1. If the Control Source is set to “Switches”, enabling is controlled by the field-installed
remote stop switch. If the unit-mounted On/Off switch is either On or Off, the unit will
be disabled if the remote switch is Off. If the unit-mounted On/Off switch is On, the
unit will be enabled if the remote switch is On.
Chiller Control Source Options:
Set Unit Setpoints Screen #1 (shown below) has three fields: “Enable”, “Mode” and
“Source.”
Unit Setpoints
SET UNIT SPs (1)
Enable=On
Mode= COOL
Source = KEYPAD
The Enable field can only be used with Source = Keypad, to enable and disable the chiller
through the key pad, any other control inputs including unit and pumpdown switches and
BAS controls are ignored. The Enable field toggles between On and Off using the Up or
Down key on the controller.
1. The Mode field is an informational display, showing the active control mode of the
chiller. It is used as an input only when the source is set to keypad, only then can this
field be changed manually.
2. The Source field has three options, “SWITCHES”(default), “KEYPAD”, and “BAS
NETWORK”.
OM WGS-5 WGS 130A to 190A 41
Page 42
a. Switches source is used when there is no BAS interface used. This allows the unit
switches to function as pumpdown and shut down switches for the circuit. This
option is also used with applications using the remote start/stop input and not using
a BAS interface.
b. Keypad source is used to override BAS or remote start/stop commands. This would
be used for servicing only.
c. BAS Network source would be used for those applications using “MODBUS”,
“BACnet”, or “LON” communications through a building automation system. BAS
Protocol is set at Set Unit Setpoints item #14.
All methods of disabling the chiller, except for the unit switch, will cause a normal
pumpdown shutoff of any running circuits. Any time the unit switch is used to disable the
chiller, all running circuits will shut down immediately, without pumping down.
Shutdown by the unit switch without going through the pumpdown cycle is undesirable and
should only be used for an emergency shutdown or for manually and locally disabling the
unit after both circuits have gone through a normal shutdown.
Unit Mode Selection
The overall operating mode of the chiller is set by the Unit Mode setpoint with options of
COOL, ICE and TEST. This setpoint can be altered by the keypad, BAS, and Mode input.
Changes to the Unit Mode Setpoint are controlled by two additional setpoints.
Available Modes setpoint: usually set during initial setup and determines the
operational modes available at any time with options of:
COOL, cooling only operation, with setpoints available for normal chilled water
temperatures
COOL w/Glycol, cooling only operation, allows lower setpoints than COOL
COOL/ICE w/Glycol, allows both cooling and ice mode operation, switchable by a
field-installed remote ICE mode switch, by the BAS or through the keypad.
ICE w/Glycol, ice mode only, i.e., full load operation until LWT setpoint is reached
TEST
Control Source Setpoint: The setting determines the source that can change the Unit
Mode Setpoint with options of KEYPAD, NETWORK, or SWITCHES.
When the Control source is set to KEYPAD, the Unit Mode stays at its previous setting until
changed by the operator. When the Control source is set to BAS, the most recent BAS
mode request goes into effect, even if it changed while the Control source was set to
KEYPAD or DIGITAL INPUTS.
Changing the Unit Mode Setpoint can be accomplished according to the following table.
NOTE: An “x” indicates that the value is ignored.
Table 17, Unit Mode Setpoint Sources
Control Source
Setpoint
x x x x COOL COOL
x x x x COOL w/Glycol COOL w/Glycol
SWITCHES OFF x x COOL/ICE w/Glycol COOL w/Glycol
SWITCHES ON x x COOL/ICE w/Glycol ICE w/Glycol
KEYPAD x COOL w/Glycol x COOL/ICE w/Glycol COOL w/Glycol
KEYPAD x ICE w/Glycol x COOL/ICE w/Glycol ICE w/Glycol
NETWORK x x COOL COOL/ICE w/Glycol COOL w/Glycol
NETWORK x x ICE COOL/ICE w/Glycol ICE w/Glycol
x x x x ICE w/Glycol ICE w/Glycol
x x x x TEST TEST
42 WGS 130A to 190A OM WGS-5
Remote
ICE Mode
Switch
Keypad Entry
BAS
Request
Available Modes
Setpoint
Resultant Unit
Mode
Page 43
The Remote ICE Mode Switch (usually a time clock) is a field installed option and is used
to switch from ice mode operation at night to cooling mode operation during the day. This
requires that the Control Source be set to SWITCHES, which in this case refers to the
Remote ICE Mode Switch.
There are really only three operational modes for the unit, although they can be used in
combination:
1. COOL, the unit unloading and compressor staging is controlled by the Active LWT
Setpoint. COOL w/ Glycol is a special case, providing for lower setpoint ranges.
2. ICE, the unit runs with all compressors fully loaded until the LWT (set for making ice)
is reached, and the unit shuts off. The Ice Delay Timer can be set to prevent restarting
until the next ice making cycle.
3. TEST, manually energize controller outputs to test functionality.
Unit Test Mode
The unit test mode allows manual testing of controller outputs. Entering this mode shall
require the following conditions.
Unit OFF input = OFF (i.e. entire chiller is shut down).
Technician password active.
Available Circuit Mode setpoint = TEST
A test menu can then be selected to allow activation of the outputs. It shall be possible to
switch each digital output ON or OFF and set the analog outputs to any value.
Unit States
The unit will always be in one of three states.
Unit States
Power ON
T3
PUMPDOWN
Transitions:
T1 – Transition from Off to Auto
Requires all of the following
Unit enabled based on settings and switches
If unit mode is ice, the ice timer has expired
No unit alarms exist
At least one circuit is enabled and available to start
T2 – Transition from Auto to Pumpdown
Requires any of the following
Control source is key
Control source is BAS and either the remote switch is “off” or the BAS command is
“off”
Control source is switches and the remote switch is “off”
pad and the unit enable keypad setting is “off”
OFF
T2
T1
T4
AUTO
OM WGS-5 WGS 130A to 190A 43
Page 44
T3 – Transition from Pumpdown to Off
Requires any of the following
All circuits have finished pumpdown and are off
A unit alarm is active
Unit switch is “off”
T4 – Transition from Auto to Off
Requires any of the following
Unit switch is “off”
A unit alarm is active
All circuits are unavailable to start (cannot start even after any cycle timers have
expired)
The unit mode is ice, all circuits are off, and the ice mode delay is active
Ice Mode Start Delay
An adjustable start to start ice delay timer will limit the frequency with which the chiller
may start in Ice mode. The timer starts when the first compressor starts while the unit is in
ice mode. While this timer is active, the chiller cannot restart in Ice mode. The time delay
is user adjustable.
The ice delay timer may be manually cleared to force a restart in ice mode. A setpoint
specifically for clearing the ice mode delay is available. In addition, cycling the power to
the controller will clear the ice delay timer.
Evaporator Pump Control
The state-transition diagram shown below controls operation of the evaporator pump.
Evaporator Pump
States
T5
OFF
T1
T4
T2
START
Power ON
T3
RUN
Transitions:
T1 – Transition from Off to Start
Requires any of the following
Unit state = Auto AND [If Low OAT Lockout active then LWT <=40]
LWT < Freeze setpoint - 1
T2 – Transition from Start to Run
Flow ok for time > evaporator recirculate time
44 WGS 130A to 190A OM WGS-5
Page 45
T3 – Transition from Run to Off
Requires any of the following
Unit state = Off AND LWT > Freeze setpoint
Low OAT Lockout is active AND No compressors running AND LWT > 70°F
T4 – Transition from Start to Off
Requires any of the following
Unit state = Off AND LWT > Freeze setpoint
Low OAT Lockout is active AND No compressors running AND LWT > 70°F
T5 – Transition from Run to Start
Requires all of the following
Evaporator water flow loss for time > flow proof
Pump Selection
The pump output used will be determined by the Evap Pump Control set point. This setting
allows the following configurations:
#1 only – Pump 1 will always be used
#2 only – Pump 2 will always be used
Auto – The primary pump is the one with the least run hours, the other is used as a backup
#1 Primary – Pump 1 is used normally, with pump 2 as a backup
#2 Primary – Pump 2 is used normally, with pump 1 as a backup
Primary/Standby Pump Staging
The pump designated as primary will start first. If the evaporator state is start for a time
greater than the recirculate timeout set point and there is no flow, then the primary pump
will shut off and the standby pump will start. When the evaporator is in the run state, if
flow is lost for more than half of the flow proof set point, the primary pump will shut off
and the standby pump will start. Once the standby pump is started, the flow loss alarm logic
will apply if flow cannot be established in the evaporator start state, or if flow is lost in the
evaporator run state.
Auto Control
If auto pump control is selected, the primary/standby logic above is still used. When the
evaporator is not in the run state, the run hours of the pumps will be compared. The pump
with the least hours will be designated as the primary at this time.
Leaving Water Temperature (LWT) Reset
The Active Leaving Water variable shall be set to the current Leaving Water Temperature
(LWT) setpoint unless the unit is in COOL mode and any of the reset methods below are
selected. The type of reset in effect is determined by the LWT Reset Type setpoint. The
Active Leaving Water variable is sent from the unit controller to all circuits for capacity
control after the applicable reset is applied.
Reset Type – NONE
The Active Leaving Water variable is set equal to the current LWT setpoint.
Reset Type – RETURN
The Active Leaving Water variable is adjusted by the return water temperature.
OM WGS-5 WGS 130A to 190A 45
Page 46
LWT set Point+Max Reset
(54)
Return Reset
Active
LWT
o
(
F)
Max Reset
(10)
LWT Set Point
(44)
0
Start Reset Delta T
Evap Delta T (oF)
The active setpoint is reset using the following parameters:
1. Cool LWT setpoint
2. Max Reset setpoint
3. Start Reset Delta T setpoint
4. Evap Delta T
Reset is accomplished by changing the Active Leaving Water variable from the Cool LWT
setpoint to the Cool LWT set-point + Max Reset setpoint as the Evaporator EWT – LWT
(Evap Delta T) varies from the Start Reset Delta T setpoint to 0.
Referring to the above figure as an example, the LWT is 44F and a 10-degree maximum
reset value was selected. The Active LWT setpoint would range from the normal 44F
setting up to 54F depending on the Evap Delta-T. The amount of reset would be at the
maximum value (10 degrees) when the Evap Delta-T is zero and at the minimum value
when the Evap Delta-T is at the Start Reset Delta T value and is proportional in between.
The Start Reset Delta T function is available so that the start of reset can be adjusted. For
example, on a system with a 10-degree Delta-T, it may be desirable to not start the resetting
until the evaporator Delta-T goes down to eight degrees (80% load), or some other value.
Reset Type – 4-20 mA
The Active Leaving Water setpoint is adjusted by the 4 to 20 mA reset analog input, using:
1. Cool LWT setpoint
2. Max Reset setpoint
3. LWT Reset signal
Reset is 0 if the reset signal is less than or equal to 4 mA. Reset is equal to the Max Reset
Delta T setpoint if the reset signal equals or exceeds 20 mA. The amount of reset will vary
linearly between these extremes if the reset signal is between 4 mA and 20 mA. An
example of the operation of 4-20 reset in Cool mode is shown below.
46 WGS 130A to 190A OM WGS-5
Page 47
(54)
4-20 mA Reset - Cool Mode
Active
LWT
o
(
F)
Max Reset
(10)
Cool LWT Set
Point (44)
0
4
20
Reset Signal (mA)
Reset Type – OAT
This reset can only be used if the unit is configured as air-cooled.
The Active Leaving Water variable is reset based on the outdoor ambient temperature.
Parameters used:
1. Cool LWT setpoint
2. Max Reset setpoint
3. OAT
Reset is 0 if the outdoor ambient temperature is greater than 75 F. From 75 down to 60 F
the reset varies linearly from no reset to the max reset at 60 F. At ambient temperatures less
than 60 F, reset is equal to the Max Reset setpoint.
OAT Reset
Cool LWT+Max Reset
(54)
Active
LWT
o
F)
(
Max Reset
(10)
Cool LWT Set-Point
(44)
60
OAT (oF)
75
Planned Unit Capacity Overrides
Unit capacity limits can be used to limit total unit capacity in COOL mode only. Multiple
limits may be active at any time, and the lowest limit is always used in the compressor
capacity control.
The estimated unit capacity and the active capacity limit are sent to all circuits for use in
compressor capacity control.
Soft Load
Soft Loading is a configurable function used to slowly ramp up the unit capacity over a
given time. The setpoints that control this function are:
OM WGS-5 WGS 130A to 190A 47
Page 48
Soft Load – (ON/OFF)
Begin Capacity Limit – (Unit %)
Soft Load Ramp – (seconds)
The Soft Load Unit Limit increases linearly from the Begin Capacity Limit setpoint to
100% over the amount of time specified by the Soft Load Ramp setpoint. If the option is
turned off, the soft load limit is set to 100%.
Demand Limit
The maximum unit capacity can be limited by a 4 to 20 mA signal on the Demand Limit
analog input at the unit controller. This function is only enabled if the Demand Limit
setpoint is set to ON.
As the signal varies from 4 mA up to 20 mA, the maximum unit capacity changes linearly
from 100% to 0%. Although the demand limit can call for 0% capacity, this signal will
never cause a running compressor to shut down. Rather, all running compressors will be
held at minimum load, and this may occur at a demand limit value that is actually less than
20mA.
Network Limit
The maximum unit capacity can be limited by a network signal. This function is only
enabled if the unit control source is set to network. The signal will be received through the
BAS interface on the unit controller.
As the signal varies from 0% up to 100%, the maximum unit capacity changes linearly from
0% to 100%. Although the network limit can call for 0% capacity, this signal will never
cause a running compressor to shut down. Rather, all running compressors will be held at
minimum load, and this may occur at a network limit value that is actually less than more
than 0%.
Condenser Pump and Tower Control
Condenser pump and cooling tower control logic requires that the unit be configured as
water-cooled in order to be active. The unit controller controls water-cooled components
such as condenser pumps and tower controls, since there is usually one tower per unit. Aircooled equipment, associated with the remote condenser option, is controlled by the circuit
controllers. Remote evaporative condensers require a self-contained, on-board, discharge
pressure control system.
Condenser Water Pump State Control
If the unit is configured as water-cooled, then the condenser pump is controlled by the statetransition diagram shown below.
Condenser Pump
States
T5
OFF
T1
T4
T2
START
Power ON
T3
RUN
48 WGS 130A to 190A OM WGS-5
Page 49
Transitions:
T1 – Transition from Off to Start
Requires any of the following
Unit state = Auto AND any circuit available AND LWT error > Startup Delta
Cond Water Freeze Alarm
T2 – Transition from Start to Run
Flow ok for time > cond recirculation timer setpoint
T3 – Transition from Run to Off
Requires all of the following
Unit state = Off OR No circuit available OR LWT error < Start Delta-1
Cond Water Freeze Alarm not active
No compressors running
T4 – Transition from Start to Off
Requires all of the following
Unit state = Off OR No circuit available OR LWT error < Start Delta
Cond Water Freeze Alarm not active
No compressors running
T5 – Transition from Run to Start
Requires all of the following
Condenser water flow loss for time > flow proof
All circuits in Off state
Pump Selection
The pump output used will be determined by the Condenser Pump Control setpoint. This
setting allows the operator to select pump #1, pump #2, or auto. The first two selections
will use a single pump output all the time. The auto selection will start the pump with the
least run hours.
The selected output will be ON if the Evap State is set to START or RUN. Both outputs
will be OFF if the Evap State is set to OFF.
Cooling Tower Control
Tower Fans
Tower fan control is active when the unit is set up as water-cooled, Tower Control is set to
Temperature, and the condenser pump is in the RUN state. Staging is based on Condenser
Entering Water Temperature. Operation depends on the following parameters.
Condenser pump state
Condenser EWT
Stage up and stage down timer values
Tower setpoints (Tower Control, Tower Stages, Stage Up Time, Stage Down Time,
Stage Differential, Stage #1 ON, Stage #2 ON, Stage Down @, Stage Up @)
When the condenser pump starts, the stage up timer shall start. The first stage shall turn ON
when the following conditions are met:
The stage up timer completes
The Condenser EWT is > Stage #1 ON setpoint
Bypass valve position is > the Stage Up @ setpoint (only if Valve/VFD Control setpoint
= Valve Stage)
VFD Speed is > the Stage Up @ setpoint (only if Valve/VFD Control setpoint = VFD
Stage OR Valve SP/VFD Stage)
OM WGS-5 WGS 130A to 190A 49
Page 50
Additional stages can turn on (up to the number specified by the Tower Stages setpoint)
when above conditions are met for the next stage.
Down staging shall occur when the following conditions are met:
The stage down timer completes
The Condenser EWT is < Stage #X ON (Temp) setpoint – Stage Differential (Temp)
setpoint
Bypass valve position is < the Stage Down @ setpoint (only if Valve/VFD Control
setpoint = Valve Stage)
VFD Speed is < the Stage Down @ setpoint (only if Valve/VFD Control setpoint =
VFD Stage OR Valve SP/VFD Stage)
Each stage up or stage down event shall restart both the stage up and stage down timers.
Only one fan output shall be switched at a time (except that all outputs switch OFF when
the condenser pump state equals OFF).
Cooling Tower Bypass Valve
When the Valve/VFD Control setpoint is set to None OR VFD Stage, this output shall be set
to 0. Otherwise, it shall be controlled as described below.
Initial Valve Position
When the condenser pump is not in the RUN state, the valve output shall be set as a
function of entering condenser water temperature (ECWT)) per the following graph.
Initial Valve Position
Max Position @
(values are examples only)
Set Point
(90°F)
Min Position @
Set Point
(60°F)
Min Start Position
Set Point (10%)
Operation After Start
When the condenser pump is in the RUN state, the valve output shall be controlled in one of
two modes as specified by the Valve/VFD Control setpoint. The controlled parameter shall
be the condenser entering water temperature. When the desired output signal varies from 0
to 100%, the output voltage shall vary as shown below.
Max Start Position
Set Point (90%)
0 to 10 VDC (Valve Type = NC to tower)
10 to 0 VDC (Valve Type = NO to tower)
Valve Setpoint Mode
This mode is operational when the Valve/VFD Control setpoint is set to Valve setpoint OR
Valve SP/VFD Stage. In this mode the valve output is varied with a proportional-derivative
50 WGS 130A to 190A OM WGS-5
Page 51
(PD) algorithm (with deadband) in order to maintain the controlled parameter (CP) at the
desired value. The output is always limited between the Valve Control Range (Min)
setpoint and the Valve Control Range (Max) setpoint. A valve increment shall be computed
once every 5 seconds according to the following equation.
Increment = [(Error) * (Error Gain setpoint)] + [(Slope) * (Slope Gain setpoint)] Where:
Error = ECWT – Valve Setpoint Slope = (Present CP) – (Previous CP)
When the Error is > the Valve Deadband setpoint, the valve position analog output (% of
full scale) is updated according to the following equation.
New %Position = Old %Position + Increment/10.
Valve Stage Mode
This mode is only operational when the Valve/VFD Control setpoint is set to Valve Stage.
In this mode the valve output is controlled as for Valve setpoint mode (above) except that
the active setpoint for the controlled parameter is selected according to the following table.
# of Fans ON Active Setpoint
0 Valve Setpoint
1 Stage #1 ON
2 Stage #2 ON
Cooling Tower Fan VFD
When the Valve/VFD Control setpoint is set to None, Valve Setpoint, OR Valve Stage, this
output shall be set to 0. Otherwise, it shall be controlled in a manner identical to Valve
Stage Mode (above) except that (1) it shall be kept at zero until the first fan stage is ON and
(2) the following setpoints do not apply.
Valve Control Range (Min)
Valve Control Range (Max)
Val v e Ty pe
Evaporative Condenser Control
It is acceptable to use WGS-A chillers (less condenser) with evaporative condensers. It is
the installer's responsibility to provide the evaporative condenser control because this
condenser type is not available from McQuay. The WGS-A software does not directly
support evaporative-cooled applications since there is a variety of fan configurations and
pumps available from the manufacturers of evaporative condensers. In addition, the WGS
software does not support the auxiliary functions of the evaporative condenser such as make
up water valves, sump drain valves, electronic make up water valves, water freeze
protection, variable frequency drives, damper controls or water treatment options. The
WGS software will provide equipment protection and operational limits as if it were a
remote air-cooled condenser application. See other sections of this manual for complete
descriptions.
The system must be comprised of two controls systems that operate together to make a
complete system. First, the WGS-A software provided with the unit will control the indoor
chiller section of the unit including compressor loading/unloading, equipment protection,
BAS interface (when applicable), and other functions as described in this manual without
the condenser control. The WGS software setup shall be treated as a remote air-cooled
application. The second control system is required to control the condenser and auxiliary
functions. The best method for interfacing the two systems is through the "first on, last off"
fan contacts as if the application was a remote air-cooled condenser. At start up of the
compressors, the Fan 1 Contactor fan contacts will close and activate the condenser control
OM WGS-5 WGS 130A to 190A 51
Page 52
system provided by others. At shut down, the reverse occurs where the condenser control
will be deactivated when the compressor stops as the Fan 1 fan contacts open.
Special considerations must be given to the condenser control including (but not limited to)
the following items.
1. All WGS-A chillers have two refrigerant circuits and an evaporative condenser with two
refrigerant circuits is also required.
2. A control system for each refrigerant circuit is required. It is best to have separate fans
and pumps for each refrigerant circuit to prevent "fighting" of control signals between
the two refrigerant circuits.
3. The control system shall maintain a minimum condenser pressure at all times.
4. The normal control philosophy is to maintain the lowest possible condensing pressure
above the minimum allowable to provide the best operating efficiency throughout the
chiller's entire operating range.
5. For a normal starting sequence, it is best to start the fans first with minimum airflow.
As the condenser pressure rises, increase the airflow by increasing the fan RPM,
opening inlet vanes, opening outlet dampers, or other meaning of increasing airflow. If
condensing pressure continues to rise after maximum airflow is reached, start the
circulating pump (s). Reverse the sequence for the shut down procedure.
6. Provide the maximum number of condenser staging steps as possible to provide as
stable operation as possible.
7. Recognize that condenser pressure will change drastically and rapidly, when the water
pump starts and stops. This is the reason for starting the fan first in an increasing
capacity situation and stopping the fan operation last with a shutdown procedure.
8. It is important for the control pressure settings for the fans and pumps to have a large
control band so that condenser component cycling does not occur. It is also good
practice for the fan and pump control to "overlap". Overlap means that the control
bands must be determined so that there is a pressure range between when a pump starts/
stops with fan operation. Use caution to be certain that fan & pump cycling does not
occur which causes rapid changes in condensing pressure which causes instability in the
refrigeration system.
9. Refer to the installation, operation and maintenance manuals of the manufacturer of the
evaporative condenser for their guidelines and recommendations. Give special
consideration to preventing freezing conditions, make up water, and other functions
common to evaporative condensers that should be described in those brochures.
!
CAUTION
Use water treatment with evaporative condensers. Failure to prevent microbiology growth,
scaling and corrosion can damage the unit.
10. Damage caused or contributed by improper water treatment may not be covered by
McQuay’s warranty.
52 WGS 130A to 190A OM WGS-5
Page 53
11. For recommendations and answers to system questions, contact the McQuay
Applications Group in Staunton, Virginia.
Building Automation System (BAS) interface and monitoring is an optional accessory
required for many systems. The WGS-A interface options are communication cards
supporting L
ONWORKS, BACnet or Modbus. Refer to the other McQuay brochures listed in
this manual for a complete description of capabilities. As a general statement, the McQuay
communication cards do NOT support the evaporative condenser. The desired interface
points for the condenser must be provided by others and through the control system
provided with the evaporative condenser. Use caution in the ability to change condenser
setpoints through the BAS system as such changes can impact chiller operation.
OM WGS-5 WGS 130A to 190A 53
Page 54
Circuit Controller Functions
Refrigerant Calculations
Refrigerant Saturated Temperature
Refrigerant saturated temperature is calculated from the pressure sensor readings for each
circuit. The pressure will be fitted to a curve made up of 12 straight line segments. The
points used to define these segments are shown in the following tables.
Table 18, Evaporator Pressure Conversion:
Pressure (PSI) Temperature (oF)
0 -15.0
7.1 0
19.0 20.0
34.7 39.0
50.7 54.0
70.4 69.0
99.6 87.0
129.2 102.0
166.8 118.0
205.4 132.0
246.5 145.0
320.0 165.0
428.5 188.1
Table 19, Condenser Pressure Conversion:
Pressure (PSI) Temperature (oF)
0 0.6
17.5 18.5
31.5 35.9
50.0 53.7
76.0 73.4
115.0 95.6
161.5 116.2
185.0 125.2
260.0 149.2
284.5 155.9
349.5 172.0
365.5 175.5
428.5 188.1
Circuit Operating Mode
The circuits on the chiller can each be individually enabled or disabled. Test mode on each
circuit can also be entered independent of all other circuits. With the circuit switch on, the
circuit mode setpoint offers settings of either enable or disable. This simply allows the
circuit to be disabled through a keypad setting.
Circuit Test Mode
The circuit test mode allows manual testing of all controller outputs. Entering this mode
requires the following conditions.
54 WGS 130A to 190A OM WGS-5
Page 55
Circuit Switch = OFF
Technician password active
Circuit Mode setpoint = TEST
A test menu can then be selected to allow activation of the outputs. It is possible to switch
each digital output ON or OFF and set the analog outputs to any value. Upon entering test
mode, all outputs will always default to the off state. Upon leaving test mode, all outputs
will automatically reset to the off state.
Compressors cannot be started in TEST mode.
Compressor Control
Multiple Compressor Staging
This section defines which compressor is the next one to start or stop. Compressors with
fewer starts will normally start first, and compressors with more run hours will normally
stop first.
Functions
Can start/stop com
Can start compressors based on number of starts (run hours if starts are equal) and stop
on run hours.
The above two modes can be combined, so that there are two or more groups, where all
compressors in the first group are started (based on number of starts/hours) before any
in the second group, etc. Conversely, all compressors in a group are stopped (based on
run hours) before any in the preceding group, etc.
pressors according to an operator defined sequence.
Multiple Compressor Start/Stop Timing – Cool Mode
This section defines when a com
cool mode.
Required Parameters
Startup Delta T setpoint.
Stage Up Delta T setpoint
Stage Down Delta T setpoint
Stop Delta T setpoint
LWT error (See definition under Compressor Capacity Control section.)
Full load indicator for each compressor
Full Load Indicator
A
circuit is considered to be at full load in the compressor staging logic when any of the
following occur:
Slide control = manual
A low or high pressure limit event has been active for 10 seconds
Slide target >= 75% AND max slide target > 75%
Slide target >= max slide target AND max slide target <= 75%
pressor is to start or stop when the chiller is operating in
OM WGS-5 WGS 130A to 190A 55
Page 56
Starting
A compressor will start (stage up):
IF LWT is above the Active LWT Setpoint plus the Startup Delta-T SP AND no
compressors are running OR all running compressors are at full load
Stopping
A compressor will stop (stage down);
IF LWT is below the Active LWT Setpoint minus the Stop Delta-T SP AND other
compressors are running or not;
OR IF LWT is below the Active LWT Setpoint minus the Stop Delta-T SP AND all other
running compressor’s slide position is less than the light load stagedown setpoint.
Multiple Compressor Start/Stop Timing – Ice Mode
This section defines when a compressor is to start or stop when the chiller is operating in ice
mode.
Required Parameters
Startup Delta T setpoint.
Stage Up Delta T setpoint
LWT error (See definition under Compressor Capacity Control section.)
Starting
A compressor will start (stage up):
IF LWT is above the Active LWT Setpoint plus the Startup Delta-T SP AND no
compressors are running OR all running compressors are at full load.
Stopping
The compressor will stop.
IF LWT reaches the ICE LWT Setpoint
Compressor Capacity Control
Compressor capacity is determined by calculating a slide position target. Adjustment to the
slide target for normal running conditions occurs every 5 seconds. For loading a maximum
change of 1% is allowed, and for unloading a maximum change of 2% is allowed.
Required parameters
Count In Load Balance status for each compressor
Slide targets of all compressors
LWT error
LWT slope
LWT Error
LWT error compares the actual LWT to the active LWT setpoint. The equation is:
LWT error = LWT – active LWT setpoint
LWT Slope
LWT slope is calculated in the unit controller and sent to circuits via pLAN.
In the unit controller, this value is calculated such that the slope represents a time frame of
one minute.
56 WGS 130A to 190A OM WGS-5
Page 57
Every 12 seconds, the current LWT is subtracted from the value 12 seconds back. This
value is added to a buffer containing values calculated at the last five intervals. The final
result is a slope value that is an average over the past 60 seconds.
Count In Load Balance Flag
A circuit will be counted for load balancing only if all of the following are true:
Compressor state is run
Compressor is able to load up (no limits in effect due to pressure or superheat)
Slide control is auto
Slide position target is less than the max slide target setpoint
Cool Mode
When the chiller is in COOL mode, capacity of the compressor is adjusted to maintain
leaving water temperature at the Active LWT setpoint while balancing the load between
running circuits. Load balance offset, LWT error, and LWT slope are used to calculate a
change in slide position as described below.
Load balance offset:
IF other compressor is flagged to be counted in load balance
THEN Load Balance Offset = slide target - (cir 1 target + cir 2 target)/2
ELSE Load Balance Offset = 0
LWT Error:
LWT Error = (Leaving Evaporator Water Temp) – (Active LWT setpoint).
LWT slope:
Slope (deg/minute) = sum of last five LWT changes as calculated every 12 seconds
Slide target adjustment = [LWT Error + (LWT Slope x 4) – Load Balance Offset] / #
Compressors Running
Ice Mode
In ICE mode, the compressor capacity is increased at the maximum rate continuously until
reaching the maximum slide position. Load balancing, LWT error, and LWT slope are
ignored.
Low OAT Start Logic
In order to avoid low pressure alarms at the start of a circuit, low OAT start logic allows for
running at low pressures for a longer time than normal, as well as multiple start attempts.
This logic is only used for air-cooled operation.
A low OAT start is initiated if the condenser saturated temperature is less than 60F when
the compressor starts. Once this happens, the circuit is in the low OAT start state for a time
equal to the low OAT start timer setpoint. During this time, the freezestat logic and the low
pressure events are disabled. The absolute limit of –10 psi is still enforced.
At the end of the low OAT start, the evaporator pressure is checked. If the pressure is
greater than, or equal to, the low evaporator pressure unload setpoint, the start is considered
successful. If the pressure is less than the unload setpoint, the start is not successful and the
compressor will stop. Three start attempts are allowed before tripping on the restart alarm;
so if on the third attempt the start is not successful, the restart alarm is triggered.
The restart counter will be reset when either a start is successful or the circuit is off on an
alarm.
OM WGS-5 WGS 130A to 190A 57
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Internal Capacity Overrides
The following conditions override the automatic slide control when the chiller is in COOL
mode or ICE mode. These overrides keep the circuit from entering a condition in which it is
not designed to run. Any compressor running with capacity limits because of these
conditions is considered to be at full load in the compressor staging logic.
Low Evaporator Pressure
If the evaporator pressure drops below the Low Evaporator Pressure Hold setpoint while the
compressor is running, the Low Evaporator Pressure Inhibit (Hold) event is triggered.
When triggered, the compressor will not be allowed to increase in capacity.
If the evaporator pressure drops below the Low Evaporator Pressure Unload setpoint while
the compressor is running, the Low Evaporator Pressure Unload event is triggered. When
triggered, the compressor will begin reducing capacity. The maximum allowed slide target
will be adjusted down 5% every 5 seconds until the evaporator pressure rises above the Low
Evaporator Pressure-Unload setpoint.
These events are logged to an event log when they occur. Both remain active until the
evaporator pressure rises above the hold setpoint plus 2 psi, or the circuit goes to a state
other than Run.
High Lift Pressure
If the compressor is running and the condenser pressure rises above the High Lift Pressure
Hold setpoint, the High Lift Pressure Inhibit event is triggered. When this happens, the
compressor will not be allowed to increase capacity. This event is active until the condenser
pressure drops 10 psi below the hold setpoint.
If the compressor is running above minimum load capacity and the condenser pressure rises
above the High Lift Pressure Unload setpoint, the High Lift Pressure Unload event is
triggered. When this happens, the compressor will begin reducing capacity. The maximum
allowed slide target will be adjusted down 5% every 5 seconds until the condenser pressure
drops below the High Condenser Pressure Unload setpoint. The compressor will not be
allowed to increase in capacity until the condenser pressure drops to 10 psi below the
unload setpoint.
Maximum LWT Pulldown Rate
The maximum rate at which the leaving water temperature can drop is limited by the
Maximum Rate setpoint, only when the LWT is less than 60
slope unload factor is used to reduce the slide target if the pulldown rate exceeds the
Maximum Rate setpoint.
Slope Unload Factor: Maximum Rate + LWT slope
If the pulldown rate is too fast, then the slide adjustment made will be equal to the slope
unload factor.
o
F and the unit mode is Cool. A
High Water Temperature Capacity Limit
If the evaporator LWT exceeds 55F, compressor slide position will be limited to a
maximum of 75%. Compressors shall unload to 75% or less if running at greater than 75%
slide position when the LWT exceeds the limit. This feature is to keep the circuit running
within the capacity of the condenser coil.
58 WGS 130A to 190A OM WGS-5
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Unit Capacity Overrides
Unit capacity limits override the automatic slide control when the chiller is in COOL mode
only. The active capacity limit as well as the estimated unit capacity will be calculated in the
unit controller and sent to all circuits.
If the unit capacity is greater than the active capacity limit, then no circuit will increase slide
position. If the unit capacity is greater than the active limit plus 1%, the circuits will unload
until the unit capacity is less than 1% greater than the active limit.
Pumpdown
When a circuit reaches a condition where the compressor needs to shut down normally, a
pumpdown will be performed. The slide target will automatically go to 0 while pumping
down, and the compressor will run until the pumpdown pressure has been reached, or the
pumpdown time has been exceeded.
Service Pumpdown
If the option for a service pumpdown is enabled, then on the next pumpdown the pressure
setpoint will be 5 psi. The circuit will pumpdown to this pressure and shut off. When the
compressor has completed the service pumpdown, the setpoint is reset to No.
Slide Positioning
Slide Position Indicator
Each compressor estimates its slide load percentage from the present value of the slide
position indicator. The percentage is based on the 4-20mA signal from the slide load
indicator. A percentage value of 0 corresponds to approximately a 4mA signal, a percentage
value of 100 corresponds to approximately a 20mA signal.
Slide Calibration Procedure
Slide Position is a relative capacity adjustment from 0.0%(Min load) to 100.0%(Max Load).
There are two MicroTech readings that apply to the indicator, Slide Target and Slide
Position. It is important to understand the difference between these. The Slide Target is
the value in which the controller uses to display the calculated prediction of slide position,
this value represents the destination or goal of pulsing the load and unload solenoid coils.
The slide target is used for direction of control for all load and unload operations, including
alarm limit events. When putting a circuit in Manual mode, the slide target is the value that
you will be adjusting. The controller will load or unload the chiller to match, with in about
3%, the target entered with the current slide position value. The second value is the Slide
Position (Pos) this is the slide position value which is the 4-20mA reading received from
the position indicator. These values can be viewed at the circuit controller on screen
“VIEW CIR STATUS (1)”.
A slide target of 0.0% is fully unloaded and the unload solenoid will be constantly
energized. A slide target of 100.0% means that the chiller is at full load and the load
solenoid is continually energized. The chiller will regulate the slide position to infinite
steps between 0% and 100% by pulsing the appropriate solenoid. Facing the discharge end
of the compressor, looking along the left side, the solenoid coil on the top is for load (oil
vent) and the solenoid coil on the side is for unload (oil feed). During normal operation, the
controller makes decisions to move the Slide target, the calculated value, and pulses the
proper solenoid in order to keep the actual and the target position with in a few percent.
OM WGS-5 WGS 130A to 190A 59
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Figure 9, Slide Indicator and Coils
Load Coil
Unload Coil
Slide Indicator
Calibration Procedure:
1. The circuit to be calibrated should be near normal operating temperatures. Note that the
compressor requires sufficient oil pressure to unload the compressor while it is running,
and may load up due to lack of oil feed pressure.
2. On the Circuit controller, first verify what your current slide target is at screen “View
Circ Status (1)” and then go to screen “SET COMP SPs (2)” to switch circuit into
manual slide control. Note: Some hold limits will be ignored but all alarm limits are
still active while in manual slide control.
3. Slowly take the circuit to 0% slide position. When the slide target is at 0%, verify that
the unload coil is energized.
4. Find the slide indicator device located on the left side of the compressor facing the
discharge end. Unscrew the metal cap and press the calibrate button beside the LED.
The red LED will come on for about 30 seconds and then start to blink. The indicator is
now calibrated at 0%.
5. Now, slowly take the circuit to 100% slide position, watching that the suction pressure
and other unit readings are OK. Always keep discharge superheat above 22°F. When
the slide target is at 100%, verify that the load coil is energized. Press the calibrate
button. The red LED will come on for about 30 seconds and then the green LED will
come on. The indicator is now calibrated at 100%.
6. The mechanical calibration is now complete for the compressor you are working with.
Replace the calibration cap.
7. Once you have the mechanical slide calibration complete you may fine tune the
calibration from the circuit controller, if necessary. On the circuit controller scroll all
the way to the right, this is the calibration and offsets menu. Scroll down until you see
“SET SENSOR OFFSET(3)”. You will see an adjustment for Min Load and Max Load
and on the bottom line you will see the value of actual slide position indicator. Add
offset until value is within +/-.5% of the corresponding full load or minimum load
position.
8. Repeat calibration procedure until all circuits have min and max positions calibrated.
Note: The Slide Indicator Transducers may vary a considerable amount with
temperature change, and therefore they need to be calibrated at typical running
temperatures.
60 WGS 130A to 190A OM WGS-5
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Manual Slide Control Mode
The slide position on each circuit can be controlled manually. A setting on the compressor
setpoints screen in each circuit controller allows the operator to select manual slide control.
On the same screen, a slide target can be selected, from 0% to 100%.
Anytime a circuit is in manual slide control, it is considered to be at full load in the staging
logic. It also will not be considered in load balancing calculations. None of the capacity
limits outlined above will apply in manual slide control, but all stop alarms are still
applicable.
Slide control will revert back to automatic control if a stop alarm occurs on the circuit or
unit, or the slide control has been manual for four hours.
Slide Pulse
The slide pulse output moves the compressor slide in order to reach the capacity requested
by the slide position target. The output will pulse for 200 ms every 6 seconds while the
Slide Pulse flag is true, that is, whenever there is a difference between the actual slide
position and the requested position.
Expansion Valve Control
The EXV can be in one of four control states. Each state is described below.
Preopen
At the time of a start request, the EXV will perform a pre-open function. This mode applies
to both remote air cooled and packaged water cooled condenser operation and helps prime
the evaporator prior to starting as well as getting the EXV in a better starting position. For
remote air-cooled condenser operation, this function is disabled should the condenser
pressure be less than the evaporator pressure at start. For remote air-cooled condenser
operation, the liquid line solenoid shall remain closed until the compressor starts. During
pre-open, the EXV signal is held at 3000 steps.
For remote condenser configuration units that come equipped with a factory mounted liquid
line solenoid, a post-open logic has been added to prevent hydraulic lock between the liquid
line solenoid and the electronic expansion valve. After the compressor performs a pump
down and cycles off, the electronic expansion valve will re-open for 30 seconds and then
return to its closed position.
Pressure Control
In pressure control, the evaporator pressure is controlled by the EXV position. The
pressure target varies based on evaporator LWT and discharge superheat values. PID logic
will be used to control the pressure to the target value.
The base pressure target is calculated using the following formula:
Base target = 0.6(LWT) – 2
The base target is limited to a range from low pressure inhibit set point + 2 psi, to 52 psi.
The pressure control target may be adjusted if the discharge superheat is not within an
acceptable range. If the superheat is less than 22oF, the base pressure target will be
reduced by a value equal to the low superheat error. If the superheat is more than 40F, the
base pressure target will be increased by a value equal to the high superheat error. At any
time, the adjusted target pressure cannot go below the low pressure inhibit set point or
above 52 psi.
When the EXV transitions to the pressure control state, the target will start at the current
evaporator pressure value. The pressure target will then decrement 0.2 psi every second
until reaching the normal calculated target. If the pressure at transition is less than the
calculated target, then pressure control will start immediately with the calculated target.
OM WGS-5 WGS 130A to 190A 61
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Superheat Control
In superheat control, suction superheat is controlled directly by the EXV. The superheat
target varies linearly from 6 to 10 degrees F as discharge superheat changes from 30
degrees F to 22 degrees F. PID logic controls the superheat to the target value.
When the EXV transitions to the superheat control state, the target will start at the current
suction superheat value. This target will then decrement 0.1 degree F every second until
reaching the normal target.
Closed
Any time the EXV is not in pressure control or superheat control, it will be in a closed
state. At this time, the EXV position is 0 steps and the EXV close signal (digital output) is
active.
After the compressor performs a pumpdown and cycles off, the electronic expansion valve
will re-open for 30 seconds. After these 30 seconds, the expansion valve will return to its
closed position. This logic has been added to help prevent hydraulic lock between the
liquid line solenoid and the electronic expansion valve.
EXV State Transitions
The following state diagram shows the transitions between EXV control states for both
packaged water-cooled and remote air-cooled condenser configurations. Preopen is not
performed for remote air cooled condenser configurations when the evaporator pressure is
greater than condenser pressure. See “EXV State Transitions – Aircooled” on page 63.
Power ON
Closed
Superheat
Transitions:
EXV States
T1
T6T7
T4
T5
T3
Preopen
T2
Pressure
T1 – Transition from Closed to Preopen
Requires all of the following
Unit State = Auto
Evap State = Run
Compressor is available
Compressor is next on
Stage up now flag is set
Compressor State = Off
OR (as in the case when a circuit cycles off)
Compressor State = Off and unit configured for remote air-cooled condenser,
(will perform a pre-open for 30 seconds (post open time) then return to Closed state)
T2 – Transition from Preopen to Pressure Control
Requires the following
62 WGS 130A to 190A OM WGS-5
Page 63
EXV State has been Preopen for a time greater than the preopen timer set point
T3 – Transition from Pressure Control to Superheat Control
Requires all of the following
Suction Superheat > Superheat target
Evap LWT <= 60 F
EXV State = Pressure AND Discharge Superheat >= 22 F for at least 3 minutes
T4 – Transition from Superheat Control to Pressure Control
Requires any of the following
Evap LWT > 63 F
Low Evap Pressure Unload event active
Discharge Superheat < 22 F or > 40 F
T5 – Transition from Pre-open to Closed state
Compressor State = Off and unit configured for remote air-cooled condenser and EXV
post open timer (non-field-adjustable at 30 seconds) has expired.
Compressor State not Run
T6, T7 – Transition from any state to Closed state
Requires the following
Compressor State not Run
EXV State Transitions – Aircooled
The following state diagram shows the transitions between EXV control states for remote
air-cooled
operation when evaporator pressure is greater than condenser pressure at start.
EXV States
Power ON
T1T4T5
Pressure
Transitions:
Closed
Superheat
T2
T3
T1 – Transition from Closed to Pressure Control
Requires all of the following
Unit State = Auto
Evap State = Run
Compressor is available
Compressor is next on
Stage up now flag is set
Compressor State = Off
T2 – Transition from Pressure Control to Superheat Control
Requires all of the following
Suction Superheat >= Superheat target
Evap LWT <= 60F
OM WGS-5 WGS 130A to 190A 63
Page 64
EXV State = Pressure AND Discharge Superheat >= 22 degrees F for at least 3 minutes
Discharge Temperature <= 180F
T3 – Transition from Superheat Control to Pressure Control
Requires any of the following
Evap LWT > 63F
Low Evap Pressure Unload event active
Discharge Superheat < 22F
Discharge Temperature > 185F
T4, T5 – Transition from any state to Closed state
Requires the following
Compressor State not Run
EXV Control Range
The table below shows the EXV range for each size compressor at minimum and maximum
capacity. The minimum and maximum values vary linearly with slide position, defining a
new EXV control range for every change in slide position.
EXV Slide %
Min 0 250 250 250
167
Compressor Size
179 197
Max 0 3000 3000 3000
Min 100 870 1080 1300
Max 100 3400 4200 5000
Based on the values in the above table, the EXV control range varies as shown in the table
below. The shaded area the control range.
EXV Control Range
Max EXV
@ 100%
EXV
Steps
Max EXV
@ 0%
Min EXV
@ 100%
Min EXV
@ 0%
0
Slide Position (%)
100
Manual EXV Control
The EXV position can be set manually. Manual control can only be selected when the
compressor is in the run state. At any other time, the EXV control set point is forced to
auto.
When EXV control is set to manual, the EXV position is equal to the manual EXV position
setting. If set to manual when the compressor state transitions from run to another state, the
control setting is automatically set back to auto.
64 WGS 130A to 190A OM WGS-5
Page 65
Oil Heater Control
The oil heater shall be on when the compressor is not running AND the oil level input is
closed for 15 seconds. This output will turn off immediately when either the oil level
switch opens or the compressor state is no longer off.
Starter Communications
The Modbus protocol is used to establish communications between the compressor starter
and the circuit controller on the supervisor port, with the circuit controller acting as the
master and the starter as the slave.
Table 20, Parameters to be Read/Written:
Register Description R/W Range Units
Bit Mask
1020 Starter Control R/W
1021 Starter Status R
1026 Avg Current R Amps
0: Run/Stop
1: Fault Reset
0: Ready
1: Running
5: Lockout
Bit Mask
2: UTS
3: Alarm
4: Fault
-
-
1027 L1 Current R Amps
1028 L2 Current R Amps
1029 L3 Current R Amps
1032 Avg Voltage R Volts
1033 L1-L2 Voltage R Volts
1034 L2-L3 Voltage R Volts
1035 L3-L1 Voltage R Volts
1037 PF R
1038 KW R KW
1039 KVA R KVA
1045 Motor FLA R/W 1-9999 Amps
1046 Motor RLA R/W 1-9999 Amps
1057 Ground Fault Trip Enable R/W
1058 Ground Fault Trip Level R/W 1-100 % RLA
1078
Fault Code – Most Recent
Fault Log Entry
R -
-99 to 100 (in 16 bit two’s
compliment signed format)
0: Disabled
1: Enabled
0.01
-
Read-only parameters are displayed at the circuit controller, and sent over pLAN to the unit
controller where they will also be displayed. Read/write parameters are accessible at the
circuit controller only. These read/write parameters are changeable when the starter
communication is working and the proper password is active.
Starter Faults
Starter faults can be viewed from the unit controller. Some starter faults will be
implemented as unique alarms, and others are grouped into a generic starter fault alarm.
OM WGS-5 WGS 130A to 190A 65
Page 66
The most recent fault code shall be stored in the alarm log parameter list. The fault reset
signal is sent to the starter when the operator clears the active alarm on the unit controller.
The starter fault codes and their corresponding alarms are shown in the table below:
Table 21, Starter Fault Codes
Fault Code Starter Fault Description Alarm Triggered
00 No Fault N/a
01 UTS Time Limit Expired No Starter Transition
02 Motor Thermal Overload Trip Compressor Current Overload Trip
10 Phase Rotation Error, not ABC Phase Reversal
12 Low Line Frequency Starter Fault
13 High Line Frequency Starter Fault
15 Input power not three phase Phase Loss
21 Low Line L1-L2 Voltage Undervoltage
22 Low Line L2-L3 Voltage Undervoltage
23 Low Line L3-L1 Voltage Undervoltage
24 High Line L1-L2 Voltage Overvoltage
25 High Line L2-L3 Voltage Overvoltage
26 High Line L3-L1 Voltage Overvoltage
27 Phase Loss Phase Loss
28 No Line Voltage Undervoltage
30 Instantaneous Overcurrent Compressor Current Overload Trip
31 Overcurrent Compressor Current Overload Trip
37 Current Imbalance Motor Current Imbalance
38 Ground Fault Ground Fault Protection
39 No Current at Run Low Motor Current
40 Shorted/Open SCR Starter Fault
47 Stack Protection Fault Starter Fault
48 Bypass Contactor Fault (on Stop Input) No Starter Transition
50 Control Power Low Starter Fault
51 Current Sensor Offset Error Starter Fault
52 Burden Switch Error Starter Fault
60 Thermistor Trip (on DIN#1) High Motor Temperature
61 Stack OT Switch Trip (on DIN#2) Starter Fault
71 Analog Input Trip Starter Fault
82 Modbus Timeout
94 CPU Error – Software Fault Starter Fault
95 CPU Error – Parameter Storage Fault Starter Fault
96 CPU Error – Illegal Instruction Trap Starter Fault
97 CPU Error – Software Watchdog Fault Starter Fault
98 CPU Error – Spurious Attempt Starter Fault
99 CPU Error – Program Storage Fault Starter Fault
Starter Fault (detected by circuit
controller)
If a starter fault is active and the active alarms are cleared at the unit controller, the clear
alarm signal will also be sent to the starter to clear the alarm status in the starter.
Loss of Starter Comm
If starter communication is lost for 10 seconds while the circuit is in a state other than Off or
there is a start request, then the Starter Fault alarm will be triggered. Without
communication, the fault code cannot be read from the starter so the code 82 will be
automatically logged with the alarm.
Condenser Fan Control
Condenser fan control from the MicroTech II controller is used only for air-cooled
condenser operation. Head pressure control, as part of the condenser, can be used instead.
66 WGS 130A to 190A OM WGS-5
Page 67
Remote evaporative condensers require their own self-contained, on-board, head pressure
controls. See page 51.
Fan Stages
There are up to 6 stages of Fantrol available. See the table below:
Table 22, Fantrol Staging
Fantrol Stage Fans On
2 1,2
3 1,2,3
4 1,2,3,4
5 1,2,4,5,6
6 1,2,3,4,5,6
Staging Up
The controller looks at high the discharge pressure is and how quickly it is rising by
accumulating “points” in a collection bin called the “Stage Up Accumulator”.
There are four Stage Up deadbands that apply to the Fantrol stages. Stages one through
three use their respective deadbands. Stage four to six share the fourth Stage Up dead band.
When the saturated condenser temperature is above the Target + the active deadband, a
Stage Up Error is accumulated.
Stage Up Error Step = Saturated Condenser Refrigerant temperature – (Target + Stage Up
dead band). If the condensing temperature is high (rising quickly) relative to the Target plus
the dead band, multiple Stage Up Error Steps will be accumulated. This will start a fan
sooner than if the temperature is rising slowly.
The Stage Up Error Step is added to Stage Up Accumulator once every Stage Up Error
Delay seconds. When the Stage Up Error Accumulator is greater than the Stage Up Error
Setpoint, another stage is added.
When a stage up occurs or the saturated condenser temperature falls back within the Stage
Up deadband, the Stage Up Accumulator is reset to zero.
Forced Fan Stage At Start
Fans may be started simultaneously with the compressor based on outdoor ambient
temperature. When the compressor starts, a Fantrol stage is forced based on the following
table. Since this logic applies only to Fantrol fans, the VFD fan is not affected.
Table 23, Forced Fan Staging
OAT Fantrol Stage At Start
> 75 oF Forced Fantrol 1 SP
> 90 oF Forced Fantrol 2 SP
> 105 oF Forced Fantrol 3 SP
Staging Down
There are four Stage Down dead bands. Stages one through three use their respective
deadbands. Stages four to eight share the fourth Stage Down deadband.
The Stage Down process is similar to the Stage Up except in reverse.
When the saturated condenser refrigerant temperature is below the Target – the active
deadband, a Stage Down error is accumulated.
Stage Down Error Step = (Target - Stage Down dead band) - Saturated Condenser
Refrigerant temperature.
OM WGS-5 WGS 130A to 190A 67
Page 68
The Stage Down Error Step is added to Stage Down Accumulator once every Stage Down
Error Delay seconds. When the Stage Down Error Accumulator is greater than the Stage
Down Error Setpoint, another stage of condenser fans turned off.
When a stage down occurs or the saturated temperature rises back within the Stage Down
deadband, the Stage Down Error Accumulator is reset to zero. The accumulator is also held
at zero after startup until either the outside ambient temperature is less than or equal to 75F,
or the saturated condenser temperature is greater than the condenser target less the active
stage down deadband.
Condenser Fan VFD
Fan VFD operation is available for use with remote condenser units.
For units configured with remote condensers, there is an option to enable fan VFD
operation.
Fan VFD speed and target are displayed.
Fan VFD minimum speed and maximum speed set points are available.
An input for fan VFD fault was added at digital input 4 on each circuit controller. VFD
faults are logged in the event log, and notification sent on BAS interface.
Fan VFD speed is sent on BAS interface.
Digital Output Control
Each digital output is controlled according to the following rules. All outputs are initialized
to OFF at power on.
Alarm – (Terminals J12 – NO1)
This output is turned ON when any Equipment Protection ALARM occurs. It is turned OFF
when all alarms have been cleared.
Evaporator Pump – (Terminals J12 – NO2)
An Evaporator Water Pump output is ON if the Evap State is set to START or RUN.
Fan #1 to #8 (Air-Cooled Condensers)
[Water Cooled = N] - Condenser Fans Staging is based on condenser pressure as selected by
Fan Stage On & Off setpoints. Fans 1, 3, 5 and 7 are for circuit 1, and fans 2, 4, 6, and 8 are
for circuit 2. Fans 1 and 2 start with the first compressor on the respective circuit when the
ambient temperature is greater than 75F. Below 75F, these fans start when the condenser
pressure gets up to the stage on setpoint.
68 WGS 130A to 190A OM WGS-5
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Using the Controller
A
4x20 Display & Keypad
Layout
The 4-line by 20-character/line, liquid crystal display and 6-key keypad for both of the
circuit controller and the unit controller is shown below.
Figure 10, Display (in MENU mode) and Keypad Layout
Air Conditioni ng
Left Arrow Key and
Red Alarm Light
<
LARM
<
VIEW
<
SET
MENU Key
Key-to-Screen
ARROW Keys (4)
ENTER Key and Green
Compressor Run Light
Note that each ARROW key has a pathway to a line in the display. Pressing an ARROW
key will activate the associated line when in the MENU mode
. There is no display line
associated with the Down Arrow.
Arrow Keys
The four arrow keys (UP, DOWN, LEFT, RIGHT) have three modes of use.
1. Scroll between data screens as indicated by the arrows (default mode).
2. Select a specific data screen in a hierarchical fashion using dynamic labels on the right
side of the display (this mode is entered by pressing the MENU key).
3. Change field values in edit mode according to the following table:
LEFT Default (D)
RIGHT Cancel (C)
UP Increment (+)
DOWN Decrement (-)
These four edit functions are indicated by one-character abbreviations on the right side of
the display (this mode is entered by pressing the ENTER key).
Getting Started, Navigating - Press the MENU key to get started. The navigating
procedures are the same for both the unit controller and the circuit controller
MENU Key
The MENU key is used to switch between the MENU mode as shown in Figure 10 and the
SCROLL mode as shown in Figure 11. The MENU mode is basically a shortcut to specific
groups of m
OM WGS-5 WGS 130A to 190A 69
.
enus used for checking ALARMS, for VIEWING information, or to SET
Page 70
setpoint values. The SCROLL mode allows the user to move about the matrix (from one
menu to another, one at a time) by using the four ARROW keys.
When in the MENU mode (as shown in Figure 10), pressing the LEFT ARROW key will
select
the ALARM menus, the RIGHT ARROW key will select the VIEW menus and the
UP key the SET menus. The controller will go the next lower menu in the hierarchy, and
then other menus can be accessed by using the ARROW keys. Pressing the MENU key
from any menu screen will automatically return to the MENU mode as shown in Figure 10.
Another way
to navigate through the menus is to press the MENU key when in the MENU
mode (as above). This will switch the controller to the SCROLL mode. The controller will
automatically go to the first screen as shown below (the upper-left menu on the menu matrix
shown on pages 72 and 87. From there, the four ARROW keys can be used to scroll up,
down, or across to any
other menu.
Figure 11, Display in the Shortcut (SCROLL) Mode and Keypad Layout
Red light for fault indication
Air Conditioni ng
MENU Key
VIEW UNIT STATUS
Unit = COOL
Compr. #1/#2=OFF/OFF
Evap Pump = RUN
ARROW Keys (4)
ENTER Key
ENTER Key + Green light for comp. On
Pressing the ENTER key changes the function of the ARROW keys to the editing function
as shown below:
LEFT key Default
, changes a value to the factory-set default value.
RIGHT key Cancel
, cancels any change made to a value and returns to the original
setting.
UP key Increment
DOWN key Decrement
, increases the value of the setting
decreases the value of a setting.
These four edit functions are indicated by one-character abbreviation on the right side of
the display (this mode is entered by pressing the ENTER key).
Changing Setpoints
Most menus containing setpoint values have several different setpoints shown on one menu.
When in a setpoint menu, the ENTER key is used to proceed from the top line to the second
line and on downward. The cursor will blink at the entry point for making a change. The
ARROW keys (now in the edit mode) are used to change the setpoint as described above.
When the change has been made, press the ENTER key to enter it. Nothing is changed until
the ENTER key is pressed.
For example, to change the chilled water setpoint:
1. Press MENU key to go to the MENU mode.
2. Press SET (the UP Key) to go to the setpoint menus.
3. Press UNIT SPs (the Right key) to go to setpoints associated with unit operation.
70 WGS 130A to 190A OM WGS-5
Page 71
4. Press the DOWN key to scroll down through the setpoint menus to the third menu
which contains Evap LWT=XX.XF.
5. Press the ENTER key to move the cursor down from the top line to the second line in
order to make the change.
6. Use the ARROW keys (now in the edit mode as shown above) to change the setting.
7. When the desired value is achieved, press ENTER to enter it and also move the cursor
down.
At this point, the following actions can be taken:
1. Change another setpoint in this menu by scrolling to it with the ENTER key.
2. Using the ENTER key, scroll to the first line in the menu. From there, the ARROW
keys can be used to scroll to different menus.
Security
All setpoints on the unit controller, as well as the circuit controllers, are protected using
passwords. Two four-digit passwords provide OPERATOR and MANAGER levels of
access to changeable parameters.
Entering Passwords
Passwords can be entered using the ENTER PASSWORD screen on the unit controller,
which is the last screen in the Unit SPs column. The password is entered by pressing the
ENTER key, scrolling to the correct value with the UP and DOWN arrow keys, and pressing
ENTER again. The longer a key is held down, the faster it will increment. The entered
password is not shown after the enter key is pressed. The operator password is 100.
Once the correct password has been entered, the ENTER PASSWORD screen indicates
which password is active (none, operator, technician, or manager). If the wrong password is
entered, a temporary message will appear so stating. If no valid password is active, the
active password level displays “none”.
Entering an incorrect password while a password is active will render that password
inactive. Entering a valid password that is not the same as the active password will result in
the active password level being changed to reflect the new password level.
Editing Setpoints
After a valid password has been entered at the unit controller, setpoints on the circuit
controllers and the unit controller can be changed. If the operator attempts to edit a setpoint
for which the necessary password level is not active, no action will be taken.
Once a password has been entered, it remains valid for 60 minutes after the last key-press
on the unit controller.
Clearing Alarms
Alarms are only shown on the unit controller and are cleared at the unit controller. No
password is required.
To clear an alarm, go to the unit controller Alarm Log. Scroll down to the last alarm listed.
The screen will note “No More Alarms”. Press and hold ENTER for several seconds until
the circuit controllers get a clear signal. If there are no active alarms, the red Alarm light
will be off and alarms status will clear from the unit and circuit controllers.
OM WGS-5 WGS 130A to 190A 71
Page 72
Menu Descriptions
Unit Controller
Various menus are shown in the controller display. Each menu screen shows specific
information. In some cases menus are used only to view the status of the unit, in some cases
they are used for checking and clearing alarms, and in some case they are used to set the
setpoint values that can be changed.
The menus are arranged in a matrix of screens across a top horizontal row. Some of these
top-level screens have sub-screens located under them. The content of each screen and its
location in the matrix are shown in Unit Controller Menu Matrix. Each menu screen’s
detailed description begins on page 73.
ARROW keys on the controller are used to navigate through the menus. The keys are
The
also used to change numerical setpoint values contained in certain menus.
As an alternate to selecting screens with the menu function, it is possible to scroll through
all of them with the 4 arrow keys. For this use, the screens are arranged logically in a
matrix as shown below.
Shortcut Menus
These menus are accessed by pressing the Menu button at any time. The hierarchical
structure of the shortcut menus is shown below.
Table 24, Unit Controller Shortcut Menus
LEVEL 1 LEVEL 2 LEVEL 3
STATUS VIEW UNIT STATUS (1-4)
TEMP VIEW UNIT TEMP (1-3)
CIR 1 VIEW CIR 1 STATUS (1-5)
CIR 2 VIEW CIR 2 STATUS (1-5)
CIR 1 VIEW REFR CIR 1 (1-5)
CIR 2 VIEW REFR CIR 2 (1-5)
VIEW
ALARM
SET
UNIT
CIR STATUS
REFRIGERANT
FANS VIEW FANS
TOWER VIEW TOWER (1-2)/
LOG EVENT/ALARM LOG
ACTIVE ALARM ACTIVE
UNIT SPs SET UNIT SPs (1-15)
COMPRESSOR SPs SET COMP SPs (1-4)
ALARM LIMITS SET ALARM LIMITS (1-4)
TOWER SPs SET TOWER SPs (1-8)
72 WGS 130A to 190A OM WGS-5
Page 73
Unit Controller Menu Matrix
When scrolling through the screens, the following matrix is used:
“VIEW” SCREENS
VIEW
UNIT
STATUS
(1)
VIEW
UNIT
STATUS
(2)
VIEW
UNIT
STATUS
(3)
VIEW
UNIT
STATUS
(4)
CONTINUATION
FROM ABOVE
VIEW
UNIT
TEMP
(1)
VIEW
UNIT
TEMP
(2)
VIEW
UNIT
TEMP
(3)
VIEW
CIR 1
VIEW
CIR 1
VIEW
CIR 1
VIEW
CIR 1
VIEW
CIR 1
ALARM
ALARM
VIEW
CIR 2
(1)
VIEW
CIR 2
(2)
VIEW
CIR 2
(3)
VIEW
CIR 2
(4)
VIEW
CIR 2
(5)
“ALARM”
SCREENS
LOG
(1)
.
.
.
.
.
.
.
.
LOG
(25)
(1)
(2)
(3)
(4)
(5)
ALARM
ACTIVE
(1)
.
.
.
.
.
.
.
.
ALARM
ACTIVE
(n)
VIEW
REFRG
CIR 1
(1)
VIEW
REFRG
CIR 1
(2)
VIEW
REFRG
CIR 1
(3)
VIEW
REFRG
CIR 1
(4)
VIEW
REFRG
CIR 1
(5)
VIEW
REFRG
CIR 2
(1)
VIEW
REFRG
CIR 2
(2)
VIEW
REFRG
CIR 2
(3)
VIEW
REFRG
CIR 2
(4)
VIEW
REFRG
CIR 2
(5)
SET UNIT
SPs
(1)
.
.
.
.
.
.
.
.
SET UNIT
SPs
(15)
VIEW
FANS
VIEW
TOWER
(1)
VIEW
TOWER
(2)
“SET SCREENS” TEST
SET COMP
SPs
(1)
SET COMP
SPs
(2)
SET COMP
SPs
(3)
SET COMP
SPs
(4)
EVENT
LOG
EVENT
LOG
(25)
SET ALARM
LMTS
(1)
SET ALARM
LMTS
(2)
SET ALARM
LMTS
(3)
SET ALARM
LMTS
(4)
(1)
.
.
.
.
.
.
.
.
CONTINUED
SET
TOWER
SPs (1)
.
.
.
.
.
.
.
.
SET
TOWER
SPs (8)
BELOW
TEST
UNIT
Selection can be made within the matrix by using the LEFT/RIGHT keys to move between
columns and the UP/DOWN keys to move between rows.
Unit Controller Menu Descriptions
This section contains information on each screen of the unit controller. The menu screens
are in order of the matrix above, going from left to right and also down when there are submenus. Many menus are self-explanatory. A Setpoint menu allows selection of whether the
unit has a water-cooled condenser, Water-Cooled = Y (Yes) or a remote condenser, WaterCooled = N (No). This selection will alter some menus as appropriate to the type of
condenser.
Screen Definitions – MENU
Top level menu:
< ALARM
< VIEW
< SET
<
OM WGS-5 WGS 130A to 190A 73
Page 74
ALARM menu:
ALARM < ACTIVE
< LOG
<
<
VIEW menu:
Water-cooled Air-cooled
VIEW < UNIT VIEW < UNIT
< CIR STATUS < CIR STATUS
<REFRIGERANT <REFRIGERANT
< TOWER < FANS
VIEW UNIT menu:
VIEW < STATUS
UNIT < TEMP
<
<
VIEW CIRCUIT STATUS menu:
VIEW CIR < CIR 1
STATUS < CIR 2
<
<
VIEW REFRIGERANT menu:
VIEW REFR < CIR 1
< CIR 2
<
<
SET menu:
Water-cooled Air-cooled
SET < ALARM LIMITS SET < ALARM LIMITS
< UNIT SPs < UNIT SPs
< COMPRESSOR SPs < COMPRESSOR SPs
< TOWER SPs
Screen Definitions – VIEW
View Unit Status
Water-cooled: Air-cooled:
VIEW UNIT STATUS (1) VIEW UNIT STATUS (1)
{Unit Status} {Unit Status}
Evap Pump= {state} Evap Pump= {state}
Cond Pump= {state}
74 WGS 130A to 190A OM WGS-5
Page 75
Unit Status will display one of the following:
Auto Off:Ice Mode Timer Off:All Cir Disabled
Off:Unit Alarm Off:Keypad Disable Off:Remote Switch
Off:BAS Disable Off:Unit Switch Off:Test Mode
Auto:Wait for load Auto:Cond Recirc Auto:Evap Recirc
Auto:Wait Cond Flow Auto:Wait Evap Flow Auto:Pumpdown
Pump states include Off, Start, and Run. The condenser pump state is visible only for
water-cooled operation.
VIEW UNIT STATUS (2)
Softload Limit=XXX.X
Demand Limit= XXX.X
Network Limit= XXX.X
VIEW UNIT STATUS (3)
Unit Capacity=XXX.X%
Ice Delay= XXh XXm
Ice Delay will be visible only when unit mode is ice. It prevents the unit from undesirable
starts before the next day’s ice-making cycle.
VIEW UNIT STATUS (4)
1 2 3 4 5 6 8
D.O. X X X X X X X
D.I. X X X X X
The digital input and output status will show either a “0” or a “1” designating Off and On
states respectively.
View Unit Temperature
VIEW UNIT TEMP (1)
Evap LWT= XXX.X oF
Evap EWT= XXX.X oF
Active SP= XXX.X oF
VIEW UNIT TEMP (2)
LWT Pulldn= 0.0 oF/m
Evap Delta T= XX.X
Water-cooled: Air-cooled:
VIEW UNIT TEMP (3) VIEW UNIT TEMP (3)
Cond EWT= XXX.X oF OAT= XXX.X oF
Cond LWT= XXX.X oF
OM WGS-5 WGS 130A to 190A 75
Page 76
View Circuit Status
In the following VIEW CIR screens, the N field indicates which circuit (#1, #2) is being
viewed. Certain screens located in the circuit controller are also displayed here on the unit
controller for convenience.
VIEW CIR N STATUS(1)
{Circuit Status}
Slide Pos= 000.0%
Slide Target=000.0%
Circuit Status will display one of the following:
Off:Ready Off:Cycle Timer Off:Low OAT Lock
Off:Keypad Disable Off:Pumpdown Switch Off:Alarm
Off:Test Mode EXV Preopen Run:Pumpdown
Run:Normal Run:LWT PullDn Limit Run:Unit Cap Limit
Run:High LWT Limit Run:Evap Press Low Run:Lift Press High
Off:pLAN failure
VIEW CIR N STATUS(2)
Hours = XXXXX
Starts = XXXXX
VIEW CIR STATUS (3)
Current (amps)
L1 L2 L3 Avg
XXX XXX XXX XXX
VIEW CIR STATUS (4)
Voltage
L1-2 L2-3 L3-1 Avg
XXX XXX XXX XXX
VIEW CIR STATUS (5)
PF= 0.XX %RLA=XXX.X
KW= XXX
KVA= XXX
View Refrigerant
In the following VIEW REFR screens, the N field indicates which circuit (#1, #2) is being
viewed.
VIEW REFR CIR N (1)
Evap Press=XXX.X psi
Cond Press=XXX.X psi
76 WGS 130A to 190A OM WGS-5
Page 77
VIEW REFRG CIR N (2)
Sat Evap= XXX.XF
Sat Cond= XXX.XF
VIEW REFRG CIR N (3)
Suct Temp = XXX.X F
Disc Temp = XXX.X F
VIEW REFRG CIR N (4)
Suct SH= XXX.X F
Disc SH= XXX.X F
VIEW REFRG CIR N (5)
Evap Approach=XX.XF
Cond Approach=XX.XF
EXV position = XXXX
View Fans
This screen is only viewable when unit is configured for air-cooled.
VIEW FANS
Fans On, Cir 1= X
Fans On, Cir 2= X
View Tower
These screens is only viewable when unit is configured for water-cooled.
VIEW TOWER (1)
Fans On= X of X
Cond EWT= XXX.X F
Set Point=XXX F
VIEW TOWER (2)
Bypass Valve=XXX.X%
VFD Speed= XXX.X%
OM WGS-5 WGS 130A to 190A 77
Page 78
Screen Definitions – ALARM
ALARM LOG: XX
{Alarm Description}
hh:mm mm/dd/yy
{Parameters}
The most recent 25 alarms, either shutdown or limit, are shown in this menu and subsequent
menus located under it. The last alarm is shown first. ARROW DOWN from this menu
will go to the next-to-last alarm, ARROW DOWN again will go to the second from last, and
so on through the last 25 occurrences. The screens are numbered (1), (2), (3), etc.
Alarm Description will indicate which alarm occurred. If the alarm is a circuit alarm, then
the circuit for which the alarm occurred will also be indicated.
Parameters at the time of the alarm are shown on the bottom line of the screen one at a time.
These are scrolled through by pressing the edit key and using the up and down arrows to
scroll through the list. Parameters include:
Unit State Evap LWT Evap EWT
Cond EWT/OAT Circuit State Evaporator Pressure
Condenser Pressure Suction Temperature Discharge Temperature
Discharge Superheat EXV Position EXV State
Slide Position Fans On
Starter Fault Code (will show “00” when the alarm logged is not a starter fault)
EVENT LOG: XX
{Event Description}
hh:mm mm/dd/yy
*** ALARM ***
hh:mm mm/dd
{Alarm Description}
NO MORE ALARMS
Press ENTER to clear
If the unit is off on a shutdown alarm or running, but in a limit alarm condition, the cause
and date will appear in the above screen. If there is a simultaneous occurrence of more than
one alarm, the others will appear in additional screens below the first one, accessed by the
DOWN ARROW. Either type alarm will light a red light in back of the LEFT-ARROW
KEY. The light will go out when the fault is cleared. To clear the fault, scroll down to the
last screen and press ENTER. If other faults have appeared, they will all be cleared at the
same time.
78 WGS 130A to 190A OM WGS-5
Page 79
Screen Definitions – SET
Unit Set Points
SET UNIT SPs (1)
Enable=On
Mode= COOL
Source = KEYPAD
Unit Enable settings can be OFF and ON as determined from the Unit Enable setpoint.
Unit Enable is an external signal or a keypad setting that keeps the unit off when the setting
is OFF and allows it to run if there is a call for cooling when the setting is ON. The source
for the signal is selected in the 4
1. KEYPAD, in which case the selection is made in line 2 and would be normally selected
as ON. This is the normal setting when no external signals are controlling the unit.
2. SWITCHES, in which an external switch is wired across terminals #60 and #66. (See
wiring diagram page 8 or 9.)
th
line and can be:
3. NETWORK, used with BAS signal, which is wired to the three com
Unit Mode settings can be
1. COOL, normal setting used with chilled water air-condition applications.
2. COOL w/GLYCOL, used with low temperature, glycol applications. It allows a lower
LWT setpoint to be used.
3. ICE w/GLYCOL, used with ice storage systems, allows changing from chilled glycol
operation to lower temperature ICE operation. In ICE, the unit runs at full load until the
ICE setpoint is reached, at which time the unit shuts off. A three-position switch wired
to terminals #60 and #68 initiates the change from glycol cooling to making ice. (See
wiring diagrams on page 8 or 9.)
Mode settings can be COOL COOLw/Glycol, or ICEw/Glycol, as determined from the
Unit
Unit Mode setpoint.
Source settings can be KEYPAD, SWITCHES, or NETWORK as determined from the
Mode Source setpoint.
munication ports.
SET UNIT SPs (2)
Available Modes
= COOL
Select w/Unit Off
SET UNIT SPs (3)
Cool LWT = XX.XF
Ice LWT = XX.XF
StartDelta=XX.XF
SET UNIT SPs (4)
StopDelta= X.XF
Stg Up Delta= X.XF
Stg Down Delta=X.XF
OM WGS-5 WGS 130A to 190A 79
Page 80
SET UNIT SPs (5)
Max Pulldn=X.XF/min
EvapRecTimer=XXX sec
Evap Pump= #1 Only
Water-cooled: Air-cooled:
SET UNIT SPs (6) SET UNIT SPs (6)
Watercooled= Yes Watercooled= No
CondRecTimer=XXX sec
Cond Pump= #1 Only
SET UNIT SPs (7)
Reset Type= none
Max Reset = XX.XF
StrtResetDT= XX.XF
SET UNIT SPs (8)
Soft Load= Off
Begin Capacity= XXX%
SoftLoadRamp= XXmin
Water-cooled: Air-cooled:
SET UNIT SPs (9) SET UNIT SPs (9)
Demand limit= Off Demand limit= Off
LowOAT Operation=No
Low Amb Lock= XX.XF
SET UNIT SPs (10)
Ice Time Delay=XXhrs
Clear Ice Timer=No
SET UNIT SPs (11)
Sensor Offset
Evap LWT= XX.XF
Evap EWT= XX.XF
80 WGS 130A to 190A OM WGS-5
Page 81
Water-cooled: Air-cooled:
SET UNIT SPs (12) SET UNIT SPs (12)
Sensor Offset Sensor Offset
Cond EWT= XX.XF OAT= XX.XF
Cond LWT= XX.XF
SET UNIT SPs (13)
CLOCK
mm/dd/yyyy
hh:mm day
SET UNIT SPs (14)
Units = F/psi
Lang = ENGLISH
After entering a valid manager password, selecting F/psi will provide IP units; selecting
C/kPa will provide SI units.
SET UNIT SPs (15)
Protocol=
Ident Number=
Baud Rate=
SET UNIT SPs (16)
Enter Password:0000
Active Password
Level:none
Compressor Set Points
SET COMP SPs (1)
Seq # Comp 1= X
Seq # Comp 2= X
SET COMP SPs (2)
Max Comps On = x
Start-Start =XX min
Stop-Start =XX min
This menu sets the anti-recycle timers. Stop-Start is the time required before starting a
compressor after it has stopped. Start-Start is the time required before starting a compressor
after the last time it has started. It is recommended that the default values of 5 minutes and
15 minutes not be changed. Max Comps On can be 1 or 2 with 2 being the default.
OM WGS-5 WGS 130A to 190A 81
Page 82
SET COMP SPs (3)
Pumpdown
Pressure= XX.X psi
Time Limit= XXX sec
SET COMP SPs (4)
Light Load Stage
Down Point=XX% slide
Stg Up Delay= XX min
SET COMP SPs (5)
Discharge Temp
Sensor Type=PT1000
Alarm Set Points
SET ALARM LIMITS (1)
Low Evap Pressure
Hold=XX.Xpsi
Unload=XX.Xpsi
The LowEvPrHold (Low Evaporator Pressure Hold) and LowEvPrUnld (Low Evaporator
Pressure Unload) have the same default value of 59 psi. If two compressors are running, the
LowEvPrUnld is in effect and the lag compressor will be shut off to unload the unit. If one
compressor is running, the LowEvPrHold is in effect and the lag compressor is prevented
from starting, thereby holding the unit capacity.
The last action to take place is the shutoff of all compressors running when the
LowEvPrStop setting is reached (default is 58 psi). Reducing these time intervals will
increase detrimental compressor cycling. It is recommended that these settings not be
changed.
SET ALARM LIMITS (2)
LowOilDelay= XXX sec
HighOilDpDel=XXX sec
Water-cooled: Air-cooled
SET ALARM LIMITS (3) SET ALARM LIMITS (3
High Disc Temp=XXXF High Disc Temp=XXXF
HighLift Delay=XXsec HighLift Delay=XXsec
LowOATStartTmr=XXsec
:
SET ALARM LIMITS (4)
Evap Freeze= XX.XF
Evap Flow Proof=XXXs
Recirc Timeout=xxmin
Evap Freeze (the unit freeze protection shutdown) is actually a stop alarm and shuts off the
unit when the LWT reaches 36F. It is cleared by going to the CLEAR ALARM menu in
the ACTIVE ALARM hierarchy.
82 WGS 130A to 190A OM WGS-5
Page 83
Evap/Cond FlowProof is the flow switch interlock. Closing the flow switch, and therefore
proving the existence of chilled water flow, resets this trip. It is recommended that these
settings not be changed.
SET ALARM LIMITS (5)
Cond Freeze= XX.XF
Cond Flow Proof=XXXs
Set Alarm Limits (5) is accessible only if unit is configured as water-cooled.
Tower Setpoints
Tower set points are only available when the unit is configured as water-cooled.
The MicroTech II controller is capable of controlling cooling tower water temperature on
chillers using water-cooled condensers. Output wiring connection points are shown on the
field wiring diagrams beginning on page 8.
Water Cooled = Y] - Condenser Pump on with first Compressor on. Tower fan control is
[
active when the Tower Control setpoint is set to Temperature and the condenser pump is in
the RUN state. Staging is based on Entering Condenser Water Temperature (ECWT).
Operation depends on the following parameters.
Condenser pump state
ECWT OR Lift pressure
Stage up and stage down timer values
Tower setpoints (Tower Control, Tower Stages, Stage Up Time, Stage Down Time,
Stage Differential, Stage #1 ON, Stage #2 ON, Stage Down @, Stage Up @)
When the condenser pump starts, the stage up timer shall start. The first stage shall turn ON
when the following conditions are met:
The stage up timer completes
The ECWT is > Stage #1 ON setpoint
Bypass valve position is > the Stage Up @ setpoint (only if Valve/VFD Control setpoint
= Valve Stage)
Additional stages can turn on (up to the number specified by the Tower Stages setpoint)
when above conditions are met for the next stage plus the following condition:
VFD Speed is > the Stage Up @ setpoint (only if Valve/VFD Control setpoint = VFD
Stage OR Valve SP/VFD Stage)
Down staging shall occur when the following conditions are met:
The stage down timer completes
The ECWT is < Stage #X ON (Temp) setpoint – Stage Differential (Temp) setpoint
point
Bypass valve position is < the Stage Down @ setpoint (only if Valve/VFD Control
setpoint = Valve Stage)
VFD Speed is < the Stage Down @ setpoint (only if Valve/VFD Control setpoint =
VFD Stage OR Valve SP/VFD Stage)
Each stage-up or stage-down event shall restart both the stage-up and stage-down timers.
Only one fan output shall be switched at a time (except that all outputs switch OFF when
the condenser pump state equals OFF).
OM WGS-5 WGS 130A to 190A 83
Page 84
SET TOWER SPs (1)
Tower Control=None
Tower Stages= 2
When Tower Control is None, the control of condenser water temperature is not by the
MicroTech II controller and assumed to be furnished elsewhere.
Tower Stages is the number of tower fans to be staged by the controller, choices are 0, 1, or
2. "0" indicates control will be by a bypass valve or variable speed pump controlled by the
MicroTech II controller.
StageUP/DN imposes a time delay between fan stages when turning on or turning off.
SET TOWER SPs (2)
Stage 1 On =XXX
Stage 2 On =XXX
StageDiff = XX.X
SET TOWER SPs (3)
Stage Up Tmr= XX min
Stage Dn Tmr= XX min
Stage Up/Dn=XXX/XXX%
StageDiff is the number of degrees below the Stage ON that will turn off the tower fans.
For example, if Stage ON #1 is 70F and StageDiff is 5F, tower fan #1 will stage off when
the ECWT drops to 65F and stage the fan on when the ECWT rises to 70F. The same is
true for fan #2.
Stage Up timer is the number of minutes that must elapse between the condenser pump
starting (it starts with the unit) and fan #1 starting or the time between fan #1 starting and
fan #2 starting.
StageDown is the elapsed time between staging down the fan motors.
SET TOWER SPs (4)
Valve/VFD Control=
None
Valve Type=NC to twr
Valve/VFD Control settings are None, Valve Setpoint, Valve Stage, VFD Stage, or
ValveSP/VFDStage. Default is None which results in no control of the tower from the
MicroTech II controller.
Valve Setpoint
as established by the Set Tower SPs in screen number 5 shown on the following page.
This mode is operational when the Valve/VFD Control setpoint is set to Valve Setpoint
OR Valve SP/VFD Stage. In this mode the valve output is varied with a proportionalderivative (PD) algorithm (with deadband) in order to maintain the controlled parameter
(CP) at the desired value. The output is always limited between the Valve Control
Range (Min) setpoint and the Valve Control Range (Max) setpoint. A valve increment
shall be computed once every 5 seconds according to the following equation. (Error
Gain and Slope Gain are set in menu screen #8.)
, the valve will control (bypass tower) to hold the minimum temperature
84 WGS 130A to 190A OM WGS-5
Page 85
Increment = [(Error) * (Error Gain setpoint)] + [(Slope) * (Slope Gain setpoint)]
Where: Error = ECWT – Valve Setpoint
Slope = (Present CP) – (Previous CP)
When the Error is > the Valve Deadband setpoint, the valve position analog output (%
of full scale) is updated according to the following equation.
New %Position = Old %Position + Increment/10
Valve Stage
, controls from the fan stage setpoint in use. It is recommended that the
Valve Setpoint method explained above be used rather than this mode.
This mode is only operational when the Valve/VFD Control setpoint is set to Valve
Stage. In this mode the valve output is controlled as for Valve Setpoint mode (above),
except that the active setpoint for the controlled parameter is selected according to the
following table.
# Of Fans ON Active Setpoint
0 Valve Setpoint
1 Stage #1 ON
2 Stage #2 ON
3 Stage #3 ON
4 Stage #4 ON
VFD Stage, ValveSP/VFDStage, When the Valve/VFD Control setpoint is set to None,
Valve Setpoint, OR Valve Stage, this output is set to 0. Otherwise, it will be controlled
in a manner identical to Valve Stage Mode (above) except that (1) it shall be kept at zero
until the first fan stage is ON, and (2) the following setpoints do not apply.
Valve Control Range (Min)
Valve Control Range (Max)
Val ve Ty pe
Valve Type settings are NC (normally closed to tower) or NO (normally open).
These settings establish the operation of a tower bypass valve (must be a 3-way valve).
Initial Valve Position
When the condenser pump is not in the RUN state, the valve output shall be set as a
function of entering condenser water temperature (ECWT) per the following graph.
Figure 12, Initial Valve Position
Initial Valve Position
Max Position @
(values are examples only)
Setpoint
(90°F)
Min Position @
Setpoint
(60°F)
Min Start Position
Setpoint
(10%)
Max Start Position
Setpoint
(90%)
OM WGS-5 WGS 130A to 190A 85
Page 86
Operation After Start
When the condenser pump is in the RUN state, the valve output shall be controlled in one of
two modes as specified by the Valve/VFD Control setpoint. The controlled parameter shall
be the condenser entering water temperature. When the desired output signal varies from 0
to 100%, the output voltage shall vary as shown below.
0 to 10 VDC (Valve Type = NC)
10 to 0 VDC (Valve Type = NO)
SET TOWER SPs (5)
Valve SP=XXX
Valve DB=XX.X
Valve SP is the minimum tower water temperature acceptable, default is 65F.
Valve DB is the dead-band in degrees, default is 2.0F.
SET TOWER SPs (6)
Valve Start Position
Min= XXX% @XXX
Max= XXX% @XXX
The ValveStart position is the position of the valve when the unit starts. Default for
minimum start position is 0%, and 100% for maximum position.
SET TOWER SPs (7)
Valve Control Range
Min= XXX%
Max= XXX%
Defaults are 10% minimum and 90% maximum.
SET TOWER SPs (8)
PD Control Loop
Error Gain=XX
Slope Gain=XX
Defaults are 25 for both error and slope.
Screen Definitions – TEST
TEST UNIT (1)
Alarm Out=Off
Evap Pump 1= Off
Evap Pump 2= Off
TEST UNIT (2)
Cond Pump 1= Off
Cond Pump 1= Off
TEST UNIT (3)
86 WGS 130A to 190A OM WGS-5
Page 87
Tower Fan 1= Off
Tower Fan 2= Off
TEST UNIT (4)
Tower Bypass= XXX.X
Tower VFD Spd= XXX.X
Circuit Controller
The display on the circuit controller displays information about the circuit that it is
controlling. Setpoint availability will be limited to setpoints that are unique to that circuit.
Other set points are changed at the Unit Controller.
Shortcut Menus
Pressing the Menu button at any time accesses these menus. The hierarchical structure of
the shortcut menus is shown below.
LEVEL 1 LEVEL 2 LEVEL 3 (No. of Screens)
UNIT VIEW UNIT (1-2)
VIEW
SET
CIR STATUS VIEW CIR STATUS (1-9)
REFRIGERANT VIEW REFRIGERANT (1-7)
FANS VIEW FANS (1-2)
COMPRESSOR SPs SET COMP SPs (1-4)
EXV SPs SET EXV SPs (1-2)
FAN SPs SET FANS (1-6)
SENSOR OFFSETS SET SENSOR OFFSET (1-3)
Menu Matrix
When scrolling through the screens, the following matrix is used:
VIEW
UNIT (1)
VIEW
UNIT (2)
VIEW CIR
STATUS
(1)
VIEW CIR
STATUS
(2)
VIEW CIR
STATUS
(3)
-
-
-
-
VIEW CIR
STATUS
(9)
VIEW
REFRG
(1)
VIEW
REFRG
(2)
VIEW
REFRG
(3)
-
-
-
-
VIEW
REFRG
(7)
VIEW
FANS
(1)
VIEW
FANS
(2)
SET
COMP SPs
(1)
SET
COMP SPs
(2)
SET
COMP SPs
(3)
SET
COMP SPs
(4)
SET
STARTER
SPs
(3-8)
SET
EXV
SPs (1)
SET
EXV
SPs (2)
SET
FANS
(1)
SET
FANS
(2)
SET
FANS
(3)
-
-
-
-
SET
FANS
(5)
Screen Definitions – MENU
Top level menu:
< VIEW
< SET
<
<
View menu:
SET
SENSOR
OFFSETS
(1)
SET
SENSOR
OFFSETS
(2)
SET
SENSOR
OFFSETS
(3)
TEST
CIRCUIT
(1)
TEST
CIRCUIT
(2)
TEST
CIRCUIT
(3)
TEST
CIRCUIT
(4)
OM WGS-5 WGS 130A to 190A 87
Page 88
VIEW < UNIT
< CIR STATUS
<REFRIGERANT
< FANS
Fan data is available only when unit is configured as air-cooled.
Set menu:
SET <COMPRESSOR SPs
< EXV SPs
< FAN SPs
<SENSOR OFFSETS
Fan setpoints are available only when unit is configured as air-cooled.
Screen Definitions – VIEW
View Unit Status
Water cooled: Air cooled:
VIEW UNIT (1) VIEW UNIT (1)
{Unit status} {Unit status}
Evap pump = {State} Evap pump = {State}
Cond pump = {State}
Unit Status will display one of the following:
Auto Off:Ice Mode Timer Off:All Cir Disabled
Off:Unit Alarm Off:Keypad Disable Off:Remote Switch
Off:BAS Disable Off:Unit Switch Off:Test Mode
Auto:Wait for load Auto:Cond Recirc Auto:Evap Recirc
Auto:Wait Cond Flow Auto:Wait Evap Flow Auto:Pumpdown
Pump states include Off, Start, and Run. The condenser pump state is visible only for
water-cooled operation.
VIEW UNIT (2)
Evap LWT= XXX.XF
Active SP= XX.XF
LWT pulldn= XX.XF/m
View Circuit Status
VIEW CIR STATUS (1)
{Circuit Status}
Slide Pos= XXX.X%
Slide Target= XXX.X%
Circuit Status will display one of the following:
Off:Ready Off:Cycle Timer Off:Low OAT Lock
Off:Keypad Disable Off:Pumpdown Switch Off:Alarm
Off:Test Mode EXV Preopen Run:Pumpdown
Run:Normal Run:LWT PullDn Limit Run:Unit Cap Limit
Run:High LWT Limit Run:Evap Press Low Run:Lift Press High
Off:pLAN failure Off:Stage Up Delay
88 WGS 130A to 190A OM WGS-5
Page 89
VIEW CIR STATUS (2)
Hours = XXXXX
Starts = XXXXX
KW Hours= XXXXXXX
A KW hours counter has been added to the Circuit control Circuit Status Screen. The KW
Hours field will display up to 9,999,999 kW-Hours.
VIEW CIR STATUS (3)
Current (amps)
L1 L2 L3 Avg
XXX XXX XXX XXX
VIEW CIR STATUS (4)
Voltage
L1-2 L2-3 L3-1 Avg
XXX XXX XXX XXX
VIEW CIR STATUS (5)
PF= 0.XX %RLA=XXX.X
KW= XXX
KVA= XXX
VIEW CIR STATUS (6)
Digital Outputs
1 2 3 4 5 6 7 8 9 10
X X X X X X X X X X
Status will be “0” for OFF and “!” for ON.
VIEW CIR STATUS (7)
Digital Outputs
11 12 13
X X X
VIEW CIR STATUS (8)
Analog Outputs
(volts X 100)
1=XXXX 3=XXXX
VIEW CIR STATUS (9)
Digital Inputs
1 3 4 5 6 9
X X X X X X
View Refrigerant
VIEW REFRIGERANT (1)
Evap Press=XXX.X psi
Cond Press=XXX.X psi
VIEW REFRIGERANT (2)
OM WGS-5 WGS 130A to 190A 89
Page 90
Sat Evap = XXX.X F
Sat Cond = XXX.X F
VIEW REFRIGERANT (3)
Suct Temp = XXX.X F
Disc Temp = XXX.X F
VIEW REFRIGERANT (4)
Suct SH= XXX.X F
Disc SH= XXX.X F
VIEW REFRIGERANT (5)
Evap Approach=XX.XF
Cond Approach=XX.XF
VIEW REFRIGERANT (6)
MaxCondSatT= XXX.XF
EXV Ctrl=Superheat
SH target= XX.XF
VIEW REFRIGERANT (7)
EXV Steps= XXXX
EXV ctrl range:
XXXX – XXXX steps
View Fans
View Fans screens are only available when the unit is configured as air-cooled.
VIEW FANS (1)
Fans Running= X
Stage Up Err= XXX
Stage Dn Err= XXX
VIEW FANS (2)
Target Sat T=XXX.XF
VFD Speed=XXX.X%
VFD Target=XX.XF
Screen Definitions – SET
Compressor Set Points
SET COMP SPs (1)
90 WGS 130A to 190A OM WGS-5
Page 91
Clear Cycle Tmr= no
Comp Size= XXX
Max Slide= XXX.X %
SET COMP SPs (2)
Circuit Mode=Enable
Slide Target= XXX.X%
Slide Control=auto
SET STARTER SPs (3)
Motor FLA= XXX amps
Motor RLA= XXX amps
The starter set points are stored in permanent memory on the starter and the Circuit control set
points will be reset to the values stored on starter when the Circuit control is powered up.
When the Circuit control is powered up the starter set points MUST be adjusted from the
Circuit control.
Ground Fault Enable, Ground Fault Trip Level, Rated RMS Voltage and CT Ratio set points
are NOT adjustable while the compressor is running.
SET STARTER SPs (4)
Ground Fault=No
GF Trip Level= XXX%
EXV Set Points
SET EXV SPs (1)
Manual EXV Pos= XXXX
EXV Control=auto
Service Pumpdown=No
SET EXV SPs (2)
Preopen Timer=XXXsec
Sensor Offsets
SET SENSOR OFFSET(1)
Evap Press= XX.X psi
Cond Press= XX.X psi
SET SENSOR OFFSET(2)
Suct Temp= X.X F
Disch Temp= X.X F
SET SENSOR OFFSET(3)
Slide min pos= XX%
Slide max pos= XX%
OM WGS-5 WGS 130A to 190A 91
Page 92
Slide Pos= XXX.X%
Fan Set Points
SET FAN SPs (1)
Number of fans = X
Fan VFD = Enable
SET FAN SPs (2)
Stg On Deadband(F)
Stg1=XX.X Stg2=XX.X
Stg3=XX.X Stg4=XX.X
SET FAN SPs (3)
Stg Off Deadband(F)
Stg2=XX.X Stg3=XX.X
Stg4=XX.X Stg5=XX.X
SET FAN SPs (4)
VFD Min Speed= XX%
VFD Min Speed= XXX%
SET FAN SPs (5)
Cond Sat Temp Target
Max= XXX.X F
Min= XXX.X F
SET FAN SPs (6)
# Fans On At Startup
>75F >90F >105F
X X X
Screen Definitions – TEST
TEST CIRCUIT (1)
Slide
Direction = Unload
Pulse = Off
TEST CIRCUIT (2)
Oil Heater= Off
EXV Closed= Off
92 WGS 130A to 190A OM WGS-5
Page 93
TEST CIRCUIT (3)
EXV Position=XXXX
TEST CIRCUIT (4)
Condenser Fans:
1=Off 2=Off 3=Off
4=Off 5=Off 6=Off
Editing Review
Editing is be accomplished by pressing the ENTER key until the desired field is selected.
This field shall be indicated by a blinking cursor under it. The arrow keys shall then operate
as defined below.
CANCEL (Right) ............. Reset the current field to the value it had when editing began.
DEFAULT (Left).............. Set value to original factory setting.
INCREMENT (Up).......... Increase the value or select the next item in a list.
DECREMENT (Down).... Decrease the value or select the previous item in a list.
During edit mode, the display shows a two-character wide menu pane on the right as shown
below.
SET UNIT SPs (X) <D
(data) <C
(data) <+
(data) <-
Additional fields can be edited by pressing the ENTER key until the desired field is
selected. When the last field is selected, pressing the ENTER key switches the display out
of “edit” mode and returns the arrow keys to “scroll” mode.
Alarms
When an alarm occurs, the alarm type, limit value (if any), date, and time are stored in the
active alarm buffer corresponding to that alarm (viewed on the Alarm Active screens) and
also in the alarm history buffer (viewed on the Alarm Log screens). The active alarm
buffers hold a record of the last occurrence of each alarm and whether or not it has been
cleared. The alarm can be cleared by pressing the Edit key. A separate buffer is available
for each alarm (High Cond Pressure, Evaporator Freeze Protect, etc.). The alarm history
buffer holds a chronological account of the last 25 alarms of any type.
Security
Two four-digit passwords provide OPERATOR and MANAGER levels of access to
changeable parameters. Either password can be entered using the ENTER PASSWORD
screen which can be accessed either through the SET OTHER menu or by simply pressing
the ENTER key while on one of the SET screens. The password can then be entered by
pressing the ENTER key, scrolling to the correct value with the UP and DOWN arrow keys,
and pressing ENTER again. Once the correct password has been entered, the previously
selected screen will reappear. Once a password has been entered, it will remain valid for 15
minutes after the last key-press.
OM WGS-5 WGS 130A to 190A 93
Page 94
BAS Interface
The MicroTech II controller is equipped with the Protocol Selectability feature, an
exclusive McQuay feature that provides easy unit interface with a building automation
system (BAS). If the unit will be tied into a BAS, the controller should have been
purchased with the correct factory-installed interface module. The modules can also be
added in the field during or after installation.
If an interface module was ordered, one of the following BAS interface installation manuals
was shipped with the unit. Contact your local McQuay sales office for a replacement, if
necessary or download from www.mcquay.com.
IM 735, L
IM 736, BACnet Communication Module Installation
IM 743, Modbus Communication Module Installation
ED 15062-0, MicroTech II Chiller Protocol Information – BACnet and L
ED 15063-0, MicroTech II Chiller Unit Controller Protocol Information – Modbus
Unit Controller Setting
Settings are made in the unit controller. Set Unit Setpoints, Menu 1 is set to Source =
Network. The specific protocol being used is set in Set Unit Setpoints, menu 15.
Connection to Chiller
Connection to the chiller for all BAS protocols will be at the unit controller. An interface
card will have to be installed in the unit controller depending on the protocol being used.
NOTE:
In this revision (D), the starter electric data in the table below is now available to the
Building Automation System at the unit control supervisor port:
Starter Parameter
Compressor Average Amps Analog Output 26
Compressor Kilowatts Analog Output 27
Compressor Average Volts Analog Output 29
ONWORKS Communication Module Installation
ONWORKS
Supervisor Type Index Number
94 WGS 130A to 190A OM WGS-5
Page 95
Unit Troubleshooting Chart
Troubleshooting can cause severe personal injury or death. Troubleshooting must
be performed by trained, experienced technicians only.
PROBLEM POSSIBLE CAUSES POSSIBLE CORRECTIVE STEPS
1. Main switch, circuit breakers open.
2. Fuse blown.
3. Thermal overloads tripped or fuses
blown.
Compressor Will
Not Run
Compressor
Noisy or Vibrating
High Discharge
Pressure
Low Discharge
Pressure
High Suction
Pressure
Continued on next page.
4. Defective contactor or coil.
5. System shut down by equipment
protection devices.
6. No cooling required.
7. Liquid line solenoid will not open.
8. Motor electrical trouble.
9. Loose wiring.
1. Flooding of refrigerant into compressor.
2. Improper piping support on suction or
liquid line.
3. Worn compressor.
1. Condenser water insufficient or
temperature too high.
2. Fouled condenser tubes (water-cooled
condenser). Clogged spray nozzles
(evaporative condenser). Dirty tube and
fin surface (air cooled condenser).
3. Noncondensables in system.
4. System overcharge with refrigerant.
5. Discharge shutoff valve partially closed.
6. Condenser undersized (air-cooled).
7. High ambient conditions.
1. Faulty condenser temp. regulation.
2. Insufficient refrigerant in system.
3. Low suction pressure.
4. Condenser too large.
5. Low ambient conditions.
1. Excessive load.
2. Expansion valve overfeeding.
!
WARNING
1. Close switch
2. Check electrical circuits and motor
winding for shorts or grounds.
Investigate for possible overloading.
Replace fuse or reset breakers after fault
is corrected.
3. Overloads are auto reset. Check unit
closely when unit comes back on line.
4. Repair or replace.
5. Determine type and cause of shutdown
and correct it before resetting protection
switch.
6. None. Wait until unit calls for cooling.
7. Repair or replace coil.
8. Check motor for opens, short circuit, or
burnout.
9. Check all wire junctions. Tighten all
terminal screws.
1. Check superheat setting of expansion
valve.
2. Relocate, add or remove hangers.
3. Replace.
1. Readjust temperature control or water
regulating valve. Investigate ways to
increase water supply.
2. Clean.
3. EPA purge the noncondensables.
4. Remove excess refrigerant.
5. Open valve.
6. Check condenser rating tables against
the operation.
7. Check condenser rating tables against
the operation.
1. Check condenser control operation.
2. Check for leaks. Repair and add charge.
3. See corrective steps for low suction
pressure below.
4. Check condenser rating table against the
operation.
5. Check condenser rating tables against
the operation.
1. Reduce load or add additional
equipment.
2. Check remote bulb. Regulate superheat.
OM WGS-5 WGS 130A to 190A 95
Page 96
PROBLEM POSSIBLE CAUSES POSSIBLE CORRECTIVE STEPS
1. Check for leaks. Repair and add charge.
2. Clean chemically.
3. Replace cartridge(s).
4. Check and reset for proper superheat.
Replace if necessary.
5. Check means for regulating condensing
temperature.
6. See corrective steps for failure of
compressor to unload.
7. Adjust flow.
1. Clean.
2. Check sump heater. Reset expansion
valve for higher superheat. Check liquid
line solenoid valve operation.
3. Add oil.
4. Adjust expansion valve.
1. Check for leaks and repair. Add
refrigerant.
2. Check riser sizes.
3. Check pitch of lines and refrigerant
velocities.
1. Check supply voltage for excessive line
drop.
2. Replace compressor-motor.
3. Check all connections and tighten.
4. See corrective steps for high discharge
pressure.
5. Check Supply voltage. Notify power
company. Do not start until fault is
corrected.
6. Provide ventilation to reduce heat.
1. Add facilities so that conditions are within
allowable limits.
2. Open valve.
1. Reset to 42°F (6°C) or above.
2. Adjust flow.
3. See “Low Suction Pressure.”
Low Suction
Pressure
Little or No Oil
Pressure
Compressor
Loses Oil
Motor Overload
Relays or Circuit
Breakers Open
Compressor
Thermal Switch
Open
Freeze Protection
Opens
1. Lack of refrigerant.
2. Evaporator dirty.
3. Clogged liquid line filter-drier.
4. Expansion valve malfunctioning.
5. Condensing temperature too low.
6. Compressor will not unload.
7. Insufficient water flow.
1. Clogged suction oil strainer.
2. Excessive liquid in crankcase.
3. Low oil level.
4. Flooding of refrigerant into crankcase.
1. Lack of refrigerant.
2. Velocity in risers too low (A-C only).
3. Oil trapped in line.
1. Low voltage during high load conditions.
2. Defective or grounded wiring in motor or
power circuits.
3. Loose power wiring.
4. High condensing temperature.
5. Power line fault causing unbalanced
voltage.
6. High ambient temperature around the
overload relay
1. Operating beyond design conditions.
2. Discharge valve partially shut.
1. Thermostat set too low.
2. Low water flow.
3. Low suction pressure.
96 WGS 130A to 190A OM WGS-5
Page 97
Page 98
All McQuay equipment is sold pursuant to McQuay’s Standard Terms and Conditions of Sale
and Limited Product Warranty. Consult your local McQuay Representative for warranty
details. Refer to form 933-430285Y-00-A (09/08). To find your local representative, go to
www.mcquay.com
This document contains the most current product information as of this printing. For the most
up-to-date product information on this unit and others, please go to www.mcquay.com.
(800) 432-1342 www.mcquay.com OM WGS-5 (11/08)
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