McQuay ALR032D Installation Manual

Operating Manual OMRCPMICRO

Group: Chiller
Part Number: 585571Y
Effective: July 2000

Supersedes: IM 493-4

MicroTech Reciprocating Chiller / Templifier Control

Models ALR 032 D/E thru 185 D/E
Models WHR 040 D/E thru 210 D/E
Models THR 040 D/E thru 210 D/E

© 1999 McQuay International

Table of Contents

Introduction............................................3

General Description...............................4

Features of the MicroTech Control Panel

.................................................................4

Optional Sensor Packages.....................5

Controller Layout...................................6

Component Data....................................7

Installation and Maintenance..............10

Field Wiring..........................................12

Software Identification.........................15

Controller Inputs/Outputs....................16

Remote Demand Limiting....................22

Head Pressure Control.........................28

Pumpdown Control................................31

"Monitor Only" Sensors and Display

Items .....................................................31

Safety Systems .....................................32

Circuit Alarm Conditions......................33

System Alarm Conditions.....................35

Other Conditions ..................................36

Normal Sequence of Operation...........37

Start-Up and Shutdown.........................39

Keypad/Display....................................42

Password Information...........................43

THR Heat/Cool Changeover...............23

Soft Loading .........................................23

Compressor Control.............................24

Lead-Lag of Refrigerant Circuits........25

Manual Operation................................25

Unit Status Modes...............................26

Circuit Status Modes...........................27

McQuay" is a registered trademark of McQuay International

"Information covers McQuay International products at the time of publication and we reserve the right

to make changes in design and construction at anytime without notice"



1997 McQuay International

Keypad Key Functions.........................43

Menu Descriptions...............................45

MicroTech Keypad Directory..............50

Test Procedure - Trouble Analysis ......59

Testing Solid-State Relays...................64

MicroTech Monitoring and Networking

Options..................................................65

2 OMRCPMICRO

Introduction

This manual provides installation, setup and troubleshooting information for the MicroTech controller
provided on McQuay reciprocating compressor chillers. Please refer to unit installation manuals for unit
application information as well as water and refrigerant piping details. All operating descriptions contained in
this manual are based on MicroTech controller software version RCPXX02G. Chiller operating characteristics
and menu selections may vary with other versions of controller software. Contact McQuayService for
software update information.

This equipment generates, uses and can radiate radio frequency energy and if not installed
and used in accordance with the instructions manual, may cause interference to radio
communications. It has been tested and found to comply with the limits for a class A digital
device, pursuant to part 15 of the FCC rules. These limits are designed to provide
reasonable protection against harmful interference when the equipment is operated in a
commercial environment.

Operation of this equipment in a residential area is likely to cause harmful interference in
which case the user will be required to correct the interference at his own expense.
McQuay International disclaims any liability resulting from any interference or for the
correction thereof.

The McQuay MicroTech control panel contains static sensitive components. A static
discharge while handling electronic circuit boards may cause damage to the components.

CAUTION

CAUTION

To prevent such damage during service involving board replacement, McQuay recommends
discharging any static electrical charge by touching the bare metal inside the panel before
performing any service work.

CAUTION

Excessive moisture in the control panel can cause hazardous working conditions and
improper equipment operation.

When servicing equipment during rainy weather conditions, the electrical devices and
MicroTech components housed in the main control panel must be protected.

The MicroTech controller is designed to operate within an ambient temperature range of -40 to 149°F and a
maximum relative humidity of 95% (non-condensing).

Figure 1, MicroTech Control

OMRCPMICRO 3

General Description

The MicroTech Unit Control Panel, available on some McQuay ALR, WHR, and THR products, contains a
Model 250 microprocessor based controller which provides all monitoring and control functions required for
the safe, efficient operation of the unit. The operator can monitor all operating conditions by using the panels
built in 2-line by 16-character display and keypad or by using an IBM compatible computer running McQuay
Monitor software. In addition to providing all normal operating controls, the MicroTech controller monitors all
safety devices on the unit and will shut the system down and close a set of alarm contracts if an alarm
condition develops. Important operating conditions at the time an alarm occurs are retained in the controllers
memory to aid in troubleshooting and analysis.

The system is protected by a simple password scheme which only allows access by authorized personnel. A
valid password must be entered into the panel keypad by the operator before any setpoints may be altered.

Features of the MicroTech Control Panel

Ø Enhanced head pressure control on air-cooled units resulting in increased total unit SEER during

transitional seasons.

Ø Preemptive control of high discharge pressures prior to a fault.
Ø 12-key keypad for adjusting water temperature set points, low water temperature cutout, high pressure

cutout, suction pressure cutout, and freeze protection. The operator can use the keypad to monitor
various operating conditions, setpoints or alarm messages.

Ø Easy-to-read 2-line by 16-character display for plain English readout of operating temperatures and

pressures, operating modes or alarm messages.

Ø Security password protection against unauthorized changing of set points and other control parameters.
Ø Complete plain English diagnostics to inform the operator of pre-alarms and alarms. All alarms are time and

date stamped so there is no guessing of when the alarm condition occurred. In addition, some operating
conditions that existed at the instant of shutdown can be recalled to aid in isolating the cause of the
problem.

Ø Soft Loading feature to reduce electrical consumption and peak demand charges during start-up.
Ø Adjustable load pulldown rate reduces over-shoot during loop pulldown.
Ø Easy integration into building automation systems via separate 4-20 milliamp signals for chilled water reset

and demand limiting (chillers only).

Ø BAS communication capability via McQuay’s open protocol strategy to over 10 major BAS manufacturers.
Ø Internal time clock for on/off scheduling.
Ø 14 holidays / dates with programmable duration.
Ø Communications capabilities for local system monitoring, changing of set points, trend logging, remote

reset, alarm and event detection via IBM-compatible PC. The optional modem kit supports the same
features from an off-site PC running the McQuay Monitor software.

Ø Manual control mode to override automatic unit staging, useful for system checkout.
Ø Pressure transducers for direct reading of system pressures.

4 OMRCPMICRO

Optional Sensor Packages

Water and air sensor package

Air-cooled units:

Ø Entering evaporator water temperature
Ø Ambient outside air temperature

Water-cooled units only:

Ø Entering evaporator water temperature
Ø Entering condenser water temperature
Ø Leaving condenser water temperature

Refrigerant sensor package

Ø Suction line temperature, circuit #1
Ø Suction line temperature, circuit #2
Ø Liquid line temperature, circuit #1
Ø Liquid line temperature, circuit #2 (Provides direct display of subcooling and superheat).

Unit amp package

Percent total unit amperage including compressors and condenser fans. Does not include externally powered
equipment such as water pumps.

OMRCPMICRO 5

Controller Layout

All major MicroTech components are mounted inside the control section side of the unit's control cabinet. The
individual components are interconnected by ribbon cables, shielded multi-conductor cables or discrete
wiring. Power for the system is provided by transformers T-2 and T-4. All field wiring must enter the control
cabinet through the knockouts provided and is terminated on field wiring terminal strips.

The standard ALR keypad/display is located inside the control cabinet for protection from the weather while
the back lit WHR and THR keypad/displays are accessible through the exterior of the control cabinet. See
Figure 2 for typical control cabinet layout.

Figure 2, Typical control cabinet layout

6 OMRCPMICRO

Component Data

Microprocessor control board

The Model 250 Microprocessor Control Board contains the electronic hardware and software necessary to
monitor and control the unit. The microprocessor control board receives input from the Analog/Digital Input
Board (ADI) and sends commands to the output board, maintaining the unit's optimum operating mode for the
current conditions. Status lights mounted on the control board indicate operating condition of the
microprocessor.

Analog/digital input board (ADI)

The ADI board receives analog/digital signals from sensors and switches. The ADI board also provides
optical isolation between the microprocessor control board and all 24 volt switch inputs. LEDs on the ADI
board provide visual indication of the status of all digital inputs. All analog and digital signals from sensors,
transducers, and switches received by the ADI board and sent to the microprocessor control board for
interpretation.

Output board

The output board contains up to 16 solid-state relays and provides optical isolation between the control board
and Vac load volts. These relays control all compressors, condenser fans, solenoid valves, and alarm
annunciation. The output board receives control signals from the microprocessor control board through a 50
conductor ribbon cable.

Keypad and display

The keypad and display is the primary operator interface to the unit. Operating conditions, system alarms, and
set points can be monitored from this display. All adjustable set points can be modified from this keypad after
the operator has entered a valid password.

Thermistor sensors

MicroTech panels use a negative temperature coefficient thermistor for temperature sensing. A sensor
operating correctly will measure 3,392 ohmsat 72°F. See Table 1 for temperature conversion information.

Pressure transducers

Pressure transducers are selected for a specific operating range and provide an output signal proportional to
the sensed pressure. Typical range for evaporator sensor is 5 to 145 psig with a resolution of 0.1 psig.
Condenser pressure sensors have a range of 20 to 450 psig and a resolution of 0.5 psig. The transducer output
characteristics are shown in Figure 3 and 4 on page 9.

Table 1, MicroTech thermistors (resistance and voltage vs. temperature)

Temp°FTemp°CResistance

Ohms
0 -17.8 25,617 4.426 50 10.0 5,971 3.213 100 37.8 1,747 1.724
1 -17.2 24,817 4.410 51 10.6 5,814 3.183 101 38.3 1,708 1.698
2 -16.7 24,044 4.393 52 11.1 5,662 3,152 102 38.9 1,670 1.673
3 -16.1 23,299 4.376 53 11.7 5,514 3.121 103 39.4 1,633 1.648
4 -15.6 22,579 4.359 54 12.2 5,371 3.090 104 40.0 1,597 1.624
5 -15.0 21,883 4.341 55 12.8 5,231 3.059 105 40.6 1,562 1.600
6 -14.4 21,212 4.323 56 13.3 5,096 3.028 106 41.1 1,528 1.576
7 -13.9 20,563 4.305 57 13.9 4,965 2.996 107 41.7 1,494 1.552
8 -13.3 19,937 4.286 58 14.4 4,838 2.965 108 42.2 1,461 1.528

Table continued on next page.

VDC
Input

Temp°FTemp°CResistance

Ohms

VDC
Input

Temp°FTemp°CResistance

Ohms

VDC
Input

OMRCPMICRO 7

Table 1, Continued from previous page

Temp°FTemp°CResistanc

e

Ohms

9 -12.8 19,332 4.267 59 15.0 4,714 2.934 109 42.8 1,430 1.505
10 -12.2 18,747 4.248 60 15.6 4,594 2.902 110 43.3 1,398 1.482
11 -11.7 18,182 4.228 61 16.1 4,477 2.871 111 43.9 1,368 1.459
12 -11.1 17,636 4.208 62 16.7 4,363 2.839 112 44.4 1,339 1.437
13 -10.6 17,108 4.187 63 17.2 4,252 2.808 113 45.0 1,310 1.415
14 -10.0 16,597 4.167 64 17.8 4,146 2.777 114 45.6 1,282 1.393
15 -9.4 16,104 4.145 65 18.3 4,042 2.745 115 46.1 1,254 1.371
16 -8.9 15,627 4.124 66 18.9 3,941 2.714 116 46.7 1,228 1.350
17 -8.3 15,166 4.102 67 19.4 3,843 2.683 117 47.2 1,201 1.328
18 -7.8 14,720 4.080 68 20.0 3,748 2.651 118 47.8 1,176 1.308
19 -7.2 14,288 4.057 69 20.6 3,655 2.620 119 48.3 1,151 1.287
20 -6.7 13,871 4.034 70 21.1 3,565 2.589 120 48.9 1,127 1.267
21 -6.1 13,467 4.011 71 21.7 3,477 2.558 121 49.4 1,103 1.247
22 -5.6 13,076 3.988 72 22.2 3,392 2.527 122 50.0 1,080 1.227
23 -5.0 12,690 3.964 73 22.8 3,309 2.496 123 50.6 1,058 1.208
24 -4.4 12,333 3.940 74 23.3 3,228 2.465 124 51.1 1,036 1.189
25 -3.9 11,979 3.915 75 23.9 3,150 2.434 125 51.7 1,014 1.170
26 -3.3 11,636 3.890 76 24.4 3,074 2.404 126 52.2 993 1.151
27 -2.8 11,304 3.865 77 25.0 3,000 2.373 127 52.8 973 1.133
28 -2.2 10,983 3.839 78 25.6 2,927 2.343 128 53.3 953 1.115
29 -1.7 10,672 3.814 79 26.1 2,857 2.313 129 53.9 933 1.097
30 -1.1 10,371 3.788 80 26.7 2,789 2.283 130 54.4 914 1.079
31 -0.6 10,079 3.761 81 27.2 2,723 2.253 131 55.0 895 1.062
32 0.0 9,797 3.734 82 27.8 2,658 2.223 132 55.6 877 1.045
33 0.6 9,523 3.707 83 28.3 2,595 2.194 133 56.1 859 1.028
34 1.1 9,258 3.680 84 28.9 2,534 2.164 134 56.7 842 1.012
35 1.7 9,002 3.653 85 29.4 2,474 2.135 135 57.2 825 0.995
36 2.2 8,753 3.625 86 30.0 2,416 2.106 136 57.8 809 0.980
37 2.8 8,512 3.597 87 30.6 2,360 2.077 137 58.3 792 0.963
38 3.3 8,278 3.569 88 31.1 2,305 2.049 138 58.9 777 0.948
39 3.9 8,052 3.540 89 31.7 2,251 2.020 139 59.4 761 0.932
40 4.4 7,832 3.511 90 32.2 2,199 1.992 140 60.0 746 0.917
41 5.0 7,619 3.482 91 32.8 2,148 1.964 141 60.6 731 0.902
42 5.6 7,413 3.453 92 33.3 2,099 1.937 142 61.1 717 0.888
43 6.1 7,213 3.424 93 33.9 2,051 1.909 143 61.7 703 0.874
44 6.7 7,019 3.394 94 34.4 2,004 1.882 144 62.2 689 0.859
45 7.2 6,831 3.365 95 35.0 1,959 1.855 145 62.8 676 0.846
46 7.8 6,648 3.335 96 35.6 1,914 1.828 146 63.3 662 0.831
47 8.3 6,471 3.305 97 36.1 1,871 1.802 147 63.9 649 0.818
48 8.9 6,299 3.274 98 36.7 1,829 1.776 148 64.4 627 0.794
49 9.4 6,133 3.244 99 37.2 1,788 1.750 149 65.0 625 0.792

VDC

Input

Temp°FTemp°CResistanc

e

Ohms

VDC

Input

Temp°FTemp°CResistanc

e

Ohms

VDC

Input

8 OMRCPMICRO

Figure 3, Evaporator transducer Figure 4, Condenser transducer

OMRCPMICRO 9

Installation and Maintenance

The MicroTech controller is factory tested and configured for the unit being controlled.

Sensors and transducers

Sensors and transducers are mounted and connected to the MicroTech ADI board with shielded cable.
Transducers are on Shrader fittings and sensors are in wells except the optional suction and liquid line sensors
(in the refrigerant sensor package). The suction and liquid line sensors are placed in a copper sleeve that is
brazed to the copper tubing. Insulation is placed around the assembly.

Sensors and transducers are connected to the MicroTech analog inputs with IDC connectors (Insulation
Displacement Connectors).

To change the transducers, just unscrew and replace. The transducers have removable cables. High pressure
transducers have a red dot on them and low pressure transducers have blue dots. Sensors do not have
separate cables.

Control wiring

Low voltage control wiring is installed, labeled and tested by the factory before shipment.

Remote 4-20 milliamp signals

Signals for leaving water reset and demand limiting can be provided by the customer and should be connected
to the terminals on the field wiring strip inside the control cabinet. See the Field Wiring section for more
details.

Interlock wiring

All interlock wiring to field devices (such as flow switches and pump starters) is provided by the installing
contractor. See Figure 5, unit wiring schematics, and field wiring diagrams at the end of this manual for details.

Unit set points and calibration

The control software is installed and tested by the factory before shipping. No periodic calibration of the
controller is necessary. All control and safety set points must be checked by the installing contractor and
adjusted as necessary before starting the unit. Controllers for McQuay chillers and Templifiers have default
set points (shown on Menus 13 through 22, in Table 8 on page 52) for:

Ø Control mode
Ø Leaving water temperature
Ø Head pressure settings
Ø Compressor staging

The default set points are suitable for most installations.
On Menu 13, the default control mode is set for "Manual Unit Off". Adjust this setting before continuing with

unit operation. Check and set the control and safety settings for the application before staging the unit. For
more information on menu items, see the Menu Description section of this manual.

Ø Softloading
Ø Holiday dates
Ø Internal scheduling
Ø Alarm functions

Modem kit

An optional modem kit allowing remote monitoring of the chiller from an off-site PC running the McQuay
Monitor software is available from McQuayService. The kit, complete with modem, mounting bracket, wiring

10 OMRCPMICRO

harness, and installation instruction can be installed in the field or at the factory. Modem wiring is shown on

the MicroTech wiring schematic. For more information, see "Telephone Line" in the Field Wiring section on

page 14.

Optional sensors

Optional sensor kits, available from the factory, can be installed in the field. Thermistors in the optional sensor

kit are negative coefficient type and have the same characteristics (see Table 1) as the thermistors used on

McQuay centrifugal chillers. Contact McQuayService for retrofit kits and ordering information.

Figure 5, Typical field wiring

OMRCPMICRO 11

Field Wiring

Interconnecting wiring for the reciprocating control panel consists of:

Ø 115 VAC power wiring
Ø Analog input signals
Ø Digital input signals
Ø Digital output signals
Ø Condenser pump
Ø Fan starter
Ø Communications to a personal computer
Ø Telephone line for remote modem access

See Figure 5 and unit field wiring diagrams at the end of this manual for more details.

Power wiring

Separate disconnects for the cooler heating tape and control circuit transformer are available as options on
ALR units. The installing contractor provides the 115 VAC power source, disconnect, 10 amp fuse, and
necessary wiring for these circuits. All wiring must conform to the National Electrical Code and applicable
local building code. If the separate power option is used, then the installing contractor must remove wires 540
and 545 from terminals #13 and #16 on TB2 before running the unit. See the ALR Field Wiring Diagram for
more detail.

Power supplies

There are several internal power supplies used by the controller and related circuitry. The regulated 5 VDC
power on terminal #214 is used to support the analog inputs on the ADI board. Do not use this power supply
to operate external devices. An unregulated 12 VDC power supply is available on field wiring terminal #146
and an unregulated 24 VAC power supply is available on field wiring terminal #25.

Analog input signals

All sensors and transducers required for normal chiller operation are installed and wired at the factory. All
optional analog signal wiring provided by the installing contractor must be twisted, shielded pair (Belden
#8760 or equal). Figure 5 and unit field wiring diagrams at the end of this manual for more detail. The optional
demand limit and leaving water reset signals are 4 to 20 milliamp DC signals. The resistive load that conditions
the milliamp signal is a 249 ohm resistor mounted on the ADI board at the factory.

Remote demand limit

To use the demand limit function, the installer will connect the wiring to terminals #131 and #132 on TB7.
Demand Limit can only be used on WHR and ALR units. See the MicroTech schematic and Field Wiring
diagrams at the end of this manual for more detail. More information on how Demand Limit works is available
in the Remote Demand Limit section on page 12 of this manual.

Leaving water reset*

Leaving water reset on ALRs, WHRs and THRs may be achieved by using the "4-20mA Reset" option on
Menu 14. The installer must connect wiring to terminals #134 and #135 on TB7. See the Reset Options section
of this manual for more detail.

12 OMRCPMICRO

Digital input signals

Remote contacts for all digital inputs into the MicroTech controller must be dry contacts suitable for the 24

VAC control signals from the reciprocating control panel. Do not connect 120 VAC control power to these or

any other connecting circuits.

Remote stop/start

If remote stop/start control is preferred, then remove the jumper between terminals #140 and #141 on TB7.

When the remote stop/start switch is open, the controller will be in the "off: remote Sw" mode. The unit is

enabled when the switch is closed.

Chilled water flow switch

The chilled water flow switch is connected to field wiring terminals #142 and #143 on TB7. When the chilled

water pump is enabled, the MicroTech controller checks for proof-of-flow through the flow switch digital input.

Digital outputs

The MicroTech output device is a normally open solid-state relay with an on-board, replaceable 5 amp fuse.

The status of all outputs are shown by individual red LEDs.

Chilled water pump relay

The optional chilled water pump relay is connected to terminal #10 on TB2. When the unit is enabled, the

chilled water pump relay is energized. Be sure the relay coil is rated for a maximum load of 1.8 amps at 120 VAC.

External alarm annunciator circuitry

An audible alarm connected to the Alarm Output of the reciprocating control panel is highly recommended to

make certain the operator is alerted to any alarm condition.

The MicroTech panel can activate an external alarm circuit when an alarm or pre-alarm condition is detected.

The alarm signal is de-energized during normal operations. During an alarm condition the alarm circuit will

energize and the alarm status light will be lit. During a pre-alarm condition, the alarm output and status light

will pulse "on" for one-half second and "off" for four seconds.

24 VAC is available at field wiring terminal #19 to power a bell, light, relay, or other external alarm devices. The

installing contractor must provide and install an alarm enunciator rated for a maximum load of 1.8 amps at 24

VAC. See the field wiring diagrams at the end of this manual for terminal locations.

Note: The alarm signal is not active during a power failure and will not provide a "Loss of Power"

alarm.

115 VAC power for the optional control transformer is obtained from the 3-phase power connection provided

by the electrical contractor.

Condenser fan wiring for chillers without condensers

The first fan of each circuit is to be wired in parallel with the first compressor stage for each circuit. Each

refrigerant circuit has three additional digital outputs available for refrigerant head pressure control. Each

output will energize an additional bank of condenser fans with each bank consisting of 1 or 2 fans, depending

on the size of the unit. The relays used to energize the fan motors must be rated for 120 VAC, 1.5 amps

maximum per coil. If a McQuay APD condenser is used, then the relays will be supplied by the factory. Relays

and fans are denoted as M12 through M24. The first number indicates the circuit while the second number

indicates the fan or fan bank number. See the Field Wiring Diagram and Staging Schematics at the end of this

manual for more detail.

Condenser pump or fan starter

Terminals #11 and #12 on TB2 on water-cooled units are reserved for starting the first fans of each circuit on a

remote condenser or for starting a single condenser pump. The relay coils should be rated for a maximum load

OMRCPMICRO 13

of 1.8 amps at 120 VAC. The terminals are wired in parallel with the compressor outputs so the coils will be
energized with the first compressor stage.

To start a condenser pump, install a jumper between terminals #11 and #12 and connect a single starter
between terminals #11 and #16 on TB2. When either of the lead compressor start, the condenser pump will
start.

To start a fan, connect the first fan of circuit #1 to terminals #11 and #16 on TB2. Connect the first fan of
circuit #2 to terminal #12 and #16 on TB2. When the lead compressor of a circuit starts, the first condenser fan
will start. See the Field Wiring Diagram and Compressor Control Schematics in the back of this manual for
more detail.

PC connection

The MicroTech controller can be connected to an IBM or IBM compatible computer for local or remote system
monitoring. Communication network wiring uses low voltage shielded twisted pair cable (Belden 8760 or
equal). The network uses the RS232 communications standard with a maximum cable length of 50 feet. An
RS232/485 adapter may be used to allow for cable runs to 5000 feet. See the Personal Computer Specification
section of this manual for hardware requirements.

Telephone line

If remote access and monitoring of the unit is chosen, then a voice quality direct dial telephone line is required.
The line must be a dedicated line and used only for modem access. The phone line must be terminated with a
standard RJ-11 modular phone plug. See the Start-Up and Shutdown section on page 39of this manual for
more detail on start-up procedures.

14 OMRCPMICRO

Software Identification

Control software is factory installed and tested in each panel prior to shipment. The software is identified by a

program code which is printed on a small label attached to the controller. The software version may also be

displayed on the keypad display be viewing the last menu item in the Misc Setup menu (menu 23).

The software "version" is the 6th and 7th digit of the software identification. In this example, the version is

"02" and the revision to the software is "G". Revisions are released in alphabetical order.

The new reciprocating codes are from a single master code which combined chiller and Templifier functions.

The new code enables selection of chiller or chiller/Templifier operation. A high memory chip is required to run

this software. Controller series 250-4 and greater can successfully run on chiller/Templifier software versions.

Example of typical software identification

RCP 2 E 01 B

Revision (A, B, C, etc.)

Version (1, 2, 3, etc.)

English/U.S. customary display units (S=SI/metric)

R-22 refrigerant (3=R-134a refrigerant)

Reciprocating chiller/Templifier code

Figure 6, Software ID tag

McQuay 06/01/95 Date Shipped

P/N 950820A-01-A Part Number

S/N 1058 Serial Number

Ver. RCP2E01B Software Version No.

OMRCPMICRO 15

Controller Inputs/Outputs

- A 4 to 20 milliamp DC signal from a building automation system

- A 4 to 20 milliamp signal from a building automation system to determine the maximum

signal from a unit mounted switch allows the unit to run in heat (0 volts - switch open) or cool (5 volts -

(standard on THR heat pumps; optional on WHR chillers) - For

common line of manifolded condenser head. The signal is used for capacity control on THRs and for

(optional) - A current transformer and adjustable voltage dropping resistor

located in the power side of the control box along with a voltage converter board sends a DC signal

Analog inputs

Analog inputs are used to read the various temperatures and pressures on the chiller as well as any customer
supplied 4-20mA reset signals. The controller's internal regulated 5 VDC and 12 VDC supplies provide the
correct operating voltage for the sensors. See Table 2 for details.

Input No. Description

0 Leaving evaporator water temperature - Sensor is located in the leaving chilled water nozzle. The

signal is used for capacity control and freeze protection.

1 Evaporator pressure transducer circuit #1 - Sensor is located in the common circuit #1 suction line.

Used to determine suction saturated refrigerant pressure and temperature. This sensor also provides
refrigerant freeze protection for circuit #1.

2 Evaporator pressure transducer circuit #2 - Sensor is located in the common circuit #2 suction line.

Used to determine suction saturated refrigerant pressure and temperature. This sensor also provides
refrigerant freeze protection for circuit #2.

3 Condenser pressure transducer circuit #1 - Saturated refrigerant pressure and temperature.
4 Condenser pressure transducer circuit #2 - Saturated refrigerant pressure and temperature.
5 Transducer power voltage ratio signal - The signal is used to correct for differences between the

controller power supply and an ideal 5 VDC supply. The controller uses this information to ensure
temperature and pressure sensor accuracy and for alarm monitoring.

6 Evaporator water temperature reset

or temperature transmitter to reset the leaving chilled water set point. The impedance of the ADI board
is 249 ohms.

7 Demand limit

number of cooling stages which may be energized. The impedance of the ADI board is 249 ohms.

8 Chiller/Templifier signal (on THR heat pumps only) - In place of the Demand Limit input, a 0 or 5 volt

switch closed) modes.

9 Entering evaporator water temp (optional) - Sensor is located in the entering chilled water nozzle. The

signal is used for monitoring and for the return reset option if selected.

10 Entering condenser water temp (optional) (O.A. temp for air cooled units) - Sensor is located in the

common entering condenser water nozzle or located remotely as an outside air temp sensor for air
cooled units. This sensor is used for monitoring purposes only.

11 Leaving condenser water temperature

WHRs, sensor is located in leaving water nozzle of one condenser only. For THRs, sensor is located in

monitoring only on WHRs.

12 Percent of total unit amps

proportional to total motor current to the microprocessor. O VDC = 0%, 4 VDC = 100%

13 Suction temp circuit #1 (optional) - Sensor located in a copper sleeve brazed to the circuit #1 suction

line measures refrigerant temperature to calculate superheat. This sensor is used for monitoring
purposes only.

14 Suction temp circuit #2 (optional) - Sensor located in a copper sleeve brazed to the circuit #2 suction

line measures refrigerant temperature to calculate superheat. This sensor is used for monitoring
purposes only.

15 Liquid line temp circuit #1 (optional) - Sensor located in a copper sleeve brazed to the circuit #1 liquid

line measures refrigerant temperature to calculate subcooling. This sensor is used for monitoring
purposes only.

16 OMRCPMICRO

16 Liquid line temp circuit #2 (optional) - Sensor located in a copper sleeve brazed to the circuit #2 liquid

line measures refrigerant temperature to calculate subcooling. This sensor is used for monitoring
purposes only.

Front panel mount
heat/cool switch front panel
mount heat/cool switch

Table 2, Analog inputs

Input Function Location Range Resolution

0 Leaving Chw temperature Leaving Chw Nozzle -40 to 263°F 0.1°F
1 Circuit #1 Evaporator Pressure Circuit #1 Suction Line 5 to 145 psig 0.1 psi
2 Circuit #2 Evaporator Pressure Circuit #2 Suction Line 5 to 145 psig 0.1 psi
3 Circuit #1 Condenser Pressure - 20 to 450 psig 0.5 psi
4 Circuit #2 Condenser Pressure - 20 to 450 psig 0.5 psi
5 Voltage Ratio Signal EnGinn Power Supply - ­6 Chw Reset Signal Supplied By Others 4 to 20mA DC ­7 Demand Limit Signal Supplied By Others 4 to 20mA DC ­8 Entering Evaporator Water Temperature Entering Chw Nozzle -40 to 263°F 0.1°F

9 Entering Condenser Water Temperature Entering Condenser Water Nozzle -40 to 263°F 0.1°F
10 Leaving Conderser Water Temperature Leaving Condenser Water Nozzle -40 to 263°F 0.1°F
11 % Total Unit Amps Control Cabinet 0 to 4 VDC 1%
12 Circuit #1 Suction Temperature Circuit #1 Suction Line -40 to 263°F 0.1°F
13 Circuit #2 Suction Temperature Circuit #2 Suction Line -40 to 263°F 0.1°F
14 Circuit #1 Liquid Line Temperature Circuit #1 Liquid Line -40 to 263°F 0.1°F
15 Circuit #2 Liquid Line Temperature Circuit #2 Liquid Line -40 to 263°F 0.1°F

Digital inputs

Table 3, Digital inputs

Inpu

LED Description Circuit Closed Open

t

0 0 Mechanical high pressure switch Circuit #1 Normal High discharge pressure
1 1 Oil differential pressure switch Compressor 1 Normal Low oil pressure
2 2 Motor protection switch Compressor 1 Normal High motor temperature
3 3 Oil differential pressure switch Compressor 3 Normal Low oil pressure
4 4 Motor protection switch Compressor 3 Normal High motor temperature
5 5 System switch Unit Normal Unit shutdown
6 6 Phase/voltage monitor Unit Normal PVM alarm
7 7 Pumpdown switch Circuit #1 Normal Manual pumpdown
8 8 Mechanical high pressure switch Circuit #2 Normal High discharge pressure
9 9 Oil differential pressure switch Compressor 2 Normal Low oil pressure

10 10 Motor protection switch Compressor 2 Normal High motor temperature
11 11 Oil differential pressure switch Compressor 4 Normal Low oil pressure
12 12 Motor protection switch Compressor 4 Normal High motor temperature
13 13 Remote stop switch Unit Run Pumpdown & stop
14 14 Water flow switches Unit Normal No evaporator (condenser) flow
15 15 Pumpdown switches Circuit #2 Normal Manual pumpdown

Note: All Digital Inputs are 24 VAC. At 7.5 VAC to 24 VAC the digital input contacts are considered
closed. Below 7.5 VAC, the contacts are considered open.

OMRCPMICRO 17

Relay board outputs

All of the MicroTech panel outputs are controlled by solid-state relays which are driven by the model 250
controller. The controller activates a solid-state relay by sending a "trigger" signal to the output board via the
attached ribbon cable. The relay responds to the trigger by lowering its resistance which allows current to
flow through its "contacts". When the controller removes the trigger signal, the relay's resistance becomes
very high, causing the current flow to stop. The outputs are individually protected by a 5 amp fuse mounted
on the output board adjacent to each relay. Table 4 and Table 5 provide additional information about each
output. Refer to the MicroTech Stage Schematics for digital output wiring.

Table 4, ALR relay board outputs

6-Stage

Digital

Output

Number

0 Alarm Circuit Same Same Same Same
1
2 Liq Sol circ #1 Same Same Same Same

3 Liq Sol circ #2 Same Same Same Same
4 Cooling

5 Cooling

6 Cooling

7 Cooling

8 Cooling Not Used Not Used

9 Cooling Not Used Not Used

10 Condenser Fan(s) M12
11 Condenser Fan(s) M13 - Same Same Same

12 Condenser Fan(s) M14 - Same Same Same
13 Condenser Fan(s) M22 Same Same Same Same
14 Condenser Fan(s) M23 - Same Same Same
15 Condenser Fan(s) M24 - Same Same Same

Note: j Number of fans varies. Refer to the Head Pressure Control section on page 28 of this manual for Fan Staging

information.

Output

Description

Chilled Water

Pump Relay

j

4-Stage Compressor Capacity

2-Compressor 2-Compressor 4-Compressor

035-070 050-070 050-070 085-185

Same Same Same Same

Compressor 1

Circuit #1

Compressor 2

Circuit #2

Compressor 1

Unloader 1

Compressor 2

Unloader 1

Same Same Same Same

Compressor 1

Circuit #1

Compressor 2

Circuit #2

Compressor 1

Unloader 1

Compressor 2

Unloader 1

Compressor

Capacity

Compressor 1

Circuit #1

Compressor 2

Circuit #2

Compressor 1

Unloader 1

Compressor 2

Unloader 1

Compressor 1

Unloader 2

Compressor 2

Unloader 2

8-Stage Compressor

Capacity

Compressor 1

Circuit #1

Compressor 2

Circuit #2

Compressor 1

Unloader 1

Compressor 2

Unloader 1

Compressor 3

Unloader 1

Compressor 4

Unloader 2

Table 5, WHR and THR relay board outputs

4-Stage Compressor

Digital

Output

Number

0 Alarm Circuit Same Same Same
1
2 Liq Sol circ #1 Same Same Same

3 Liq Sol circ #2 Same Same Same
4 Cooling

5 Cooling

6 Cooling

Output

Description

Chilled Water

Pump Relay

Capacity

2-Compressor 2-Compressor 4-Compressor

WHR 040-085E

THR 040-110D

Same Same Same

Compressor 1

Circuit #1

Compressor 2

Circuit #2

Compressor 1

Unloader 1

18 OMRCPMICRO

6-Stage

Compressor

Capacity

WHR 070-085E

THR 070-110D

Compressor 1

Circuit #1

Compressor 2

Circuit #2

Compressor 1

Unloader 1

8-Stage Compressor

Capacity

WHR 095-210E

THR 120-170D

Compressor 1

Circuit #1

Compressor 2

Circuit #2

Compressor 1

Unloader 1

7 Cooling

8 Cooling Not Used

9 Cooling Not Used

10 Condenser Fan(s) M12

k

11 Condenser Fan(s) M13

k

12 Condenser Fan(s) M14

k

13 Condenser Fan(s) M22

k

14 Condenser Fan(s) M23

k

15 Condenser Fan(s) M24

k

Compressor 2

Unloader 1

Same Same Same
Same Same Same
Same Same Same
Same Same Same
Same Same Same
Same Same Same

Compressor 2

Unloader 1

Compressor 1

Unloader 2

Compressor 2

Unloader 2

Compressor 2

Unloader 1

Compressor 3

Circuit 1

Compressor 4

Circuit 2

Note: kCondenserless WHR only.
User selectable reset options are found under Menu 14, item line G "ResetOpt= " for chillers and item line H

"Reset Sig= ##.#mA" for Templifiers. Most reset options apply to leaving chilled water only—ALRs, WHRs,
and THRs operated in chiller mode. The only reset options available for THRs operated in heating mode
(controlled by leaving condenser water) are: "None", "4-20mA", and "Network". Selected reset option
settings for chilled and heated water temperatures are displayed in Menu 14.

None

"None" is the Default Values setting. When selecting "None", the following applies:

Ø Leaving evaporator water temperature or leaving condenser water temperature, whichever is applicable

control the unit.

Ø Leaving evaporator water temperature control ALRs, WHRs, and THRs operating in the "chiller" mode.
Ø Leaving condenser water temperature control THRs operating in "heat pump" mode.

Return

By selecting "Return" as the reset mode, the controller resets the leaving chilled water temperature set point as
required to maintain a constant return water temperature. To choose "Return" as the reset option, first select
"Return" in the "ResetOpt" mode and press <ENTER>, then in the "ReturnSpt" item, select the return water set
point temperature to be maintained. The return water set point algorithm is internal to the controller. No other
action is required.

4-20mA (remote reset signal)*

By selecting "4-20mA" as the reset option, the controller will reset the leaving chilled water temperature to a
higher value based on a percentage of the Maximum Chilled Water Reset ("MaxChWRst"). At 4mA, the chilled
water set point resets to a value equal the Leaving Evaporator Water Set Point ("Lvg Evap") plus the
MaximumChilled Water Reset ("MaxChWRst") set point. Any valuebetween 4 and 20mA will add a
proportional value of the Maximum Chilled Water Reset to the Leaving Chilled Water Set Point. The reset
schedule is linear and may be determined using Figure 7, Leaving Water Reset, below. The external 4-20mA
control signal displays under "ResetSig=" on Menu 14.

For THRs operated in heating mode, the "Lvg Evap" indicates the degree of heating reset. Using the 4-20mA
reset signal, a proportional value of the Maximum Chilled Water Reset "MaxChWRst" is subtracted from the
Leaving Condenser Water Set Point ("Lvg Cond" Menu #4). The reset control signal will display on Menu
#14, item line "Reset Sig". The reset schedule is linear and may be determined using Figure 7, Leaving Water
Reset, below.

Terminals #134 and #135 on TB7 are the field wiring 4-20mA remote reset terminal. See the field wiring
diagrams in the back of this manual for more detail.

OMRCPMICRO 19

Figure 7, Leaving water reset

Ice (remote reset signal)

When in "Ice" mode, all compressors will run 100% loaded (that is no unloaders energized) to make certain that
compressors cool appropriately. As a result, the number of stages in "Ice" mode will equal the number of
compressors. Use approved solutions in the chilled water loop to protect the system to at least 15°F lower
than the ice setpoint. When Leaving Evaporator Water (Lvg Evap") is set less than 34°F, "Ice" mode must be
used. Cylinder unloading of compressors when suction temperatures fall below 25°F will prevent the
compressor motor from cooling adequately. The lowest Leaving Water Ice set point for McQuay reciprocating
chillers is 21°F. With an Ice set point of 21°F, saturated suction temperatures of 12°F or 13°F are typical. This
is the lowest recommended saturated suction temperature for McQuay reciprocating products.

Most ice storage applications require dual reset control. Use terminals #134 and #135 on TB7 for field wiring 4­20mA remote reset connections. See the field wiring diagrams at the end of this manual for more detail.

IMPORTANT

If a 4-20mA signal device is not available, a dual contact is required, then a dry contact

between terminals #215 and #135 may be used to initiate reset. When using a dry contact,

"open" will maintain the ice set point and "close" will initiate a full reset.

If the chiller is to be used for ice storage, select the "Ice" option in Menu 14. "LvgWater Spts", "ResetOpt=".
To calculate the leaving chilled water set point, the control band (Menu 14 "CntrlBand=") and shut down
delta-T (Menu 14 ShutDn D-T=") must first be selected. The equation to determine leaving chilled water
temperature:

Lvg Evap = Desired Ice Temp + 1/2"CntrlBand + " "ShutDn D-T"

Lvg Evap = 21°F + 1/2 (4) + 1.5°F

LvgEvap = 21 +2+ 1.5

Lvg Evap = 24.5

For day operation the maximum chilled water reset (Menu 14 "MaxChWRst=") is added to the "Lvg Evap" as
calculated above to reach the desired day operating leaving chilled water temperature.

When the Ice option is selected, the resetting of the leaving chilled water set point (during day operation) via
the 4-20mA input is not a functional option. To retain the option, the set points in Menu 14 must be changed
by a Building Automation System through our MicroTech Open Protocol Monitor Software.

When a 4-20mA signal is used to initiate ice reset, if a signal less than 4mA is received, nothing happens—the
ice mode temperature will be maintained. When a signal of 4mA or more is received, the unit changes to a non­ice building mode temperature. The control signal will be displayed under "Reset Sig" on Menu #14.

The alarm setpoints (see Menu 22) will also need to be adjusted. The following is an example of alarm set
points for a typical ice operation:

20 OMRCPMICRO

1. "Frz Stat": Set to the saturated refrigerant pressure that corresponds to a temperature equal to 13.5°F

below the ice set point. For example, if the ice set point is 23°F, the "Frz Stat" would be set at 33 psig,
(which is 23°-13.5° = 9.5°F; 33 psig is R-22 saturation pressure at 9.5°F).

2. "Frze H 2O": Set at least 4°F below the ice set point, but not lower than the freezing point of the solution.

In this example, the "Frze H2O" would be set at 19°F.

3. "LP CutOut": Set 8 to 10 psi below the "Frz Stat" setting but never below 20 psig.

4. "LP Cutin": Set 15 to 20 psi above "LP CutOut".

5. FreezeTimer ("FreezeTim") and Condenser High Pressure ("Hi Press"): Do not need to be adjusted.

Network

Based on the Maximum Chilled Water Reset Set Point ("MaxChWRst"), the "Network" option allows a signal
to be sent that reflects 0 to 100% reset of the Leaving Chilled Water Set Point ("Lvg Evap") for chillers (except
Ice mode) or Leaving Condenser Water Set Point ("Lvg Cond") for THRs. This option functions similar to the
4-20mA option.

OMRCPMICRO 21

Remote Demand Limiting

Demand limiting applies to ALR and WHR chillers only. Remote demand limiting may be accomplished by
connecting to terminals #131 and #132 on TB7. A 4-20mA signal is required. Based on the 4-20mA signal,
demand limiting will cause the chiller to limit the total number of stages regardless of the amount of cooling
actually required. A signal of 4mA or less allow all stages to operate while a 20mA or more will allow only one
stage to operate. The effect of the 4-20mA signal may be determined using Figures 8, 9 and 10. Under Menu
#18, demand limits, the number of stages allowed by demand limiting will be displayed as well as the actual
remote demand limit signal in milliamps.

Figure 8, Remote demand limit, 4-stage unit

Figure 9, Remote demand limit, 6-stage unit

Figure 10, Remote demand limit, 8-stage unit

22 OMRCPMICRO

THR Heat/Cool Changeover

On THR heat pumps, instead of the demand limit input, a 0 to 5 volt signal from a front panel unit-mounted
switch allows the unit to run in heat and cool modes. Five volts is obtained at terminal #215, wired through the
unit mounted switch and then connected to terminal #132 on TB7. When the switch is "open", the unit is in
heating mode. When the switch is "closed" the unit is in cooling mode. Menu #18 shows which mode the unit
is in. "ChVTmp Sig = Temp" denotes heating mode and "Chl/Tmp Sig = Chil" denotes cooling mode. In chiller
mode, the unit is controlled by the leaving evaporator water. To operate the unit as a Templifier, choose
"ChlTmp" under Item E of Menu #23. See Normal Sequence of Operation section of this manual for more
information.

Soft Loading

Soft loading limits the number of available stages when the unit is started to prevent excessive power
consumption and possible overshoot of the leaving water temperature set point. Soft loading is in effect
whenever the unit is started from an "off" cycle. This option is selectable and available in Menu 15.

On initial start-up, the controller will run the chilled water pump and sample the loop water temperature for a
time equal to the Load Delay set point ("LoadDelay") on Menu 15. If cooling or heating is required at the end
of the time delay, then the liquid line solenoid valve will be open and refrigerant will flow. When the
evaporator refrigerant pressure rises above the LP Cut In Set Point ("LP CutIn" see Menu #22), the controller
will start the first compressor. On entering the "Stage" the controller starts a countdown timer to indicate how
long the unit has been in the cool or heat stage mode. The number of stages allowed during soft loading is
determined by the Soft Load Maximum Stages ("SoftLdMaxStg" see Menu #15). The duration of the soft load
sequence is determined by the Soft Load Timer ("SoftLoad" see Menu #15). If the Soft Load Timer is set to
zero, no soft loading will take place. When the soft load option is enabled, any time remaining in the Soft Load
Timer will be displayed on Menu 15 under item "Time Left".

The following set points may be adjusted on Menu 15:

Ø Soft Load: This is the amount of time soft loading will be in effect after the controller begins staging. If set

to zero, no soft loading is cancelled.

Ø SoftLdMaxStg: Determines the maximum number of cooling or heating stages which may be energized

while soft loading is in effect.

Ø LoadDelay: The amount of time allowed for the controller to sample the loop water temperature before

initiating cool or heat stages.

OMRCPMICRO 23

Compressor Control

The compressor staging logic uses an adjustable control band and interstage timer to determine the correct
number of cooling or heating stages to activate. A project-ahead temperature calculation and a maximum pull
down rate provide stable operation. Compressor set points are shown on Menu 16.

The Control Band is the temperature range on either side of the active leaving water set point that must be
exceeded for a stage change to occur. When in chiller mode and after the unit has started, the controller will
stage-up when the leaving water temperature rises to the Leaving Chilled Water Set Point plus half of the
Control Band. The controller will stage-down when the leaving water temperature lowers to the Leaving
Chilled Water Set Point minus half the Control Band. The THR, controlled from leaving condenser water,
stages up and down in the reverse order of a unit in chiller operation.

The adjustable compressor Interstage Timer set point ("InterStg", see Menu #16) sets the time delay between
the current cooling or heating stage and the next stage-up request. The compressor stage-down time delay is
fixed at a 1/3 ratio of the stage-up setting. For more information on staging, refer to the "Normal Sequence of
Operation" section on page 37 of this manual.

The controller performs a project-ahead temperature calculation to protect against an overshoot condition
when the leaving water temperature is outside the control band. Project-ahead calculation also moderates the
controller's response to a rapid increase and decrease in leaving water temperature. During cooling mode, if
the chilled water temperature is above the control band and the project-ahead calculation has determined that
the chilled water temperature will fall below the control band within 240 seconds (4 minutes), then the
controller will unload the compressors and stage-down the unit until the condition is no longer true. For THRs
in the heating mode, if the project-ahead calculation has determined that the leaving condenser water
temperature will rise above the control band wishing 240 seconds (4 minutes), then the controller will unload
the compressors and stage-down the unit until the condition is no longer true.

As additional protection against overshooting the unit set point, the controller uses the maximum pull down
rate ("MaxPullDn", on Menu #14) to determine if the leaving water temperature is pulling down or up too
rapidly. Every minute, the controller checks the leaving water temperature and compares the temperature to the
last reading. If the Pull Down Rate is exceeded, the controller delays additional stages. Maximum Pull Down
("MaxPullDn", on Menu #14) default setting is 0.5°F. This setting may be changed on Menu 14, Lvg Evap
Spts,.

The MicroTech soft loading feature will also guard against problems of overshooting the set point. The Soft
Load ("SoftLoad" on Menu #15) default setting is 20 minutes up to stage 4 of cooling and heating stages. See
"Soft Loading" section of this manual for more information.

The Interstage Timer ("InterStg" on Menu #16) default setting is 180 seconds for cooling and heating stages.
Interstage timers (anti-cycle) for compressors are 5 minute stop-to-start and 15 minute start-to-start.

24 OMRCPMICRO

Lead-Lag of Refrigerant Circuits

Automatic

The controller provides automatic lead-lag of refrigeration circuits. The circuit having the fewest number of
starts on all compressors in the circuit will be started first. Changes to circuit capacity will be made by
changing the position of the compressor unloaders when applicable. Compressors will be selected by
changing unloader status. This prevents short-cycling of compressors when the cooling load is low. If both
circuits are operating and a stage-down to one circuit is required, the circuit with the most operating hours will
cycle off first.

Manual

The operator may manually select the lead refrigerant circuit or have the controller automatically select the lead
refrigerant circuit to equalize compressor hours. Automatic lead-lag may be defeated by selecting circuit #1 or
circuit #2 as the lead circuit ("Lead Circuit" Menu 16).

Manual Operation

Manual operating modes are available to facilitate setup and troubleshooting of the unit. Any of the following
manual modes may be selected from the Control Mode Menu.

ManualOff: Manual unit off.
Auto1Off2: Automatic Circ #1, Circ #2 off.
Auto2Off1: Automatic Circ #2, Circ #1 off.
ManualStaging: Manual Staging, Circ #1 & 2.

Note: These manual settings are intended to aid in troubleshooting and should not be considered to
be normal operating modes. The equipment should not be left unattended during manual operation as
the automatic staging controls are disabled. The chiller will remain in the manual mode until
Automatic operation is selected.

OMRCPMICRO 25

Unit Status Modes

The operating status of the unit is displayed on the keypad/display when the information is requested by the
operator. Description of each Unit Status Mode are listed below.

"Off: Remote SW" mode

Upon start-up, the panel will check the "Remote Stop Switch" digital input. If the switch is open, the controller
will be in the "Off: Remote SW" mode. Note that from the factory, the unit will ship with a mechanical jumper
between the field terminals. If remote stop/start control is desired, remove jumper between terminals 140 and

141.

"Off: Time Clock" mode

If the controller has been commanded to an off state via the internal time clock (Menu 20), the mode will be
"Off: Time Clock". Note that if a customer wishes the unit to run 24 hours per day, the eight day clock must be
set to start at 00:00 and stop at 23:59 for all days.

"Starting" mode

If the remote stop switch is closed and the internal time clock is calling for the unit to run, the controller will
initiate "Starting" mode.

"Wait for Flow" mode

The chilled water pump output relay is energized any time the unit is enabled. The controller will check for the
presence of chilled water flow via the normally open flow switch. If flow is not proven within 30 seconds, the
alarm "LossofWater Flow" will be activated and the unit will remain in the "Waiting for Flow" mode until water
flow is proven. Once flow is established, the alarm will automatically be cleared.

Loss of water flow during unit operation will cause the unit to log the alarm and return to the "Waiting for
Flow" state. When chilled water flow has been re-established, the alarm will again automatically be cleared.

"Wait for Load" mode

With water flow established, the controller will wait for a period of time equal to the "Load Delay" set point to
determine if the water loop is above or below the current active water set point. In chiller mode, if leaving
chilled water temperature is above the leaving chilled water set point plus 1/2 of the control band plus the
start-up delta-T, the controller will enter the stage mode otherwise the controller will wait until the end of the
currently scheduled run period.

In heating mode (Templifier only), if the leaving condenser water temperature is below the leaving condenser
water set point minus 1/2 the control band minus the start-up delta-T, the controller will enter the stage mode.

"Stages 1-8"

This is the normal mode the unit will be in while cooling or heating. The number of currently active stages will
be displayed. The stage is only an indicator of system capacity and does not indicate which compressors or
circuits are on.

"Off: Alarm"

This is the mode which will be displayed when a circuit is in an alarm condition which means no cooling or
heating on that circuit is possible. Refer to the System Alarms and Circuit Alarms sections in this manual for
additional details.

"Off: Manual" mode - If the control mode of the unit is "Manual Off" the unit status will be displayed as "Off:
Manual" mode.

"Off: PumpDnSw's" - If the pumpdown switch digital inputs for both circuits are in the "manual " position,
the mode of the unit is "Off: PumpDnSw's".

"Manual Stage" - If the control mode of the unit is "Manual Stage" the unit status will be displayed as
"Manual Stage".

26 OMRCPMICRO

"Stage Up", "Stage Down" - These are momentary operating modes indicating a stage up or stage down is
being initiated by the controller.

"Off: System Sw" mode - Upon start-up the panel will check the front panel "System Switch" position. If the
switch is in the "stop" position, the mode will be "Off: System Sw".

Circuit Status Modes

The operating status of each refrigeration circuit is displayed on the keypad/display when the information is
requested by the operator. Descriptions of each Circuit Status Mode are listed below.

"Off:System Sw" - Off due to System Switch.
"Off: Manual Mode" - Off due to Control Mode Set Point.
"Off: Alarm" - Off due to Alarm Condition.
"Off:PumpDnSw" - Off, the circuit pumpdown switch is in the manual position.
"Off: CycleTime" - Off due to anti-cycle timers.
"Off: Ready" - Off Ready to start or Standby.
"Pumping Down" - The circuit is in the process of pumping down, the solenoid valve is closed.
"Open Solenoid" - A request has been made for the circuit to be energized for cooling or heating, the solenoid

is open and the controller is waiting for the pressure to rise above the LPCutIn set point.
"% Capacity" - Circuit is running, all operating conditions are normal. The circuit percent capacity is

displayed.

OMRCPMICRO 27