McQuay WMC 300D Installation Manual

Operating and Maintenance Manual

OMM WMC-3 OITS

Group: Chiller
Part Number: 331374701
Effective: April 2006

Supersedes: OM WMC-2

WMC Magnetic Bearing Compressor Chillers

Model WMC 035T, 300D
50/60 Hertz
OITS Software Version: 2.02.01
Control Software Version: WMCUU02C

Table of Contents

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

Features of the Control Panel.................4

Definitions ................................................5

General Description ................................8

Control Panel.........................................10

Use with On-Site Generators................11

Sequence of Operation..........................12

Multi-Chiller Setup ...............................13

Operating the Control System..............15

Interface Panel On/Off......................................15

Start/Stop Unit..................................................

Change Setpoints..............................................

Alarms ..............................................................

Component Failure...........................................

15
15
15
16

Component Description........................16

Operator Interface Touch Screen......................16

Unit/Compressor Controller Description..........

Navigating ........................................................

16
17

Unit Controller.......................................19

Unit Controller Setpoints..................................19

Faults, Problems, Warnings ..............................

Unit Controller Functions.................................

21
22

Compressor Controller .........................23

Compressor Controller Setpoints......................24

Compressor Faults, Problems, Warnings..........

Compressor Controller Functions.....................

25
26

Compressor On-Board

Controllers..............................................

30

Interface Touch Screen..........................32

Navigation ........................................................32

Screen Descriptions ..........................................

VIEW Screens ..................................................

SET Screens......................................................

SERVICE Screen..............................................

HISTORY Screens............................................

Download Data.................................................

ACTIVE ALARM Screen.................................

34
34
39
52
53
54
55

Unit Controller Menu Screens .............57

Menu Matrix.....................................................58

Compressor Controller Menu

Screens....................................................

Menu Matrix.....................................................75

75

BAS Interface.........................................77

Operation...............................................

Operator Responsibilities..................................78

Compressor Operation......................................

Operating Limits:..............................................

Pressure Drop Curves.......................................

MicroTech II™ Control ....................................

Capacity Control System..................................

Surge and Stall..................................................

Condenser W ater Temperature..........................

Normal Unit Startup/Shutdown........................

Annual Unit Startup/Shutdown.........................

78

78
78
80
81
82
82
82
84
85

Maintenance...........................................85

Pressure/Temperature Chart ..............................86

Routine Maintenance........................................

Repair of System...............................................

87
88

Maintenance Schedule..........................90

Service Programs...................................91

Operator Schools...................................91

Warranty Statement..............................

91

Manufactured in an ISO Certified Facility

©

Illustrations and information cover McQuay International products at the time of publication and we reserve the right to make changes in design and

®™ The following are trademarks or registered trademarks of their respective companies: BACnet from ASHRAE; Modbus from Gould, Inc; L

2 OMM WMC-3 OITS

LONWORKS from Echelon Corporation; and MicroTech II from McQuay International.

and

2005 McQuay International

construction at anytime without notice.

Controllers are LONMARK certified with an

optional LONWORKS communication module.

ONMARK

Introduction

This manual provides setup, operating, and troubleshooting information for McQuay WMC
centrifugal chillers with the MicroTech ΙΙ™ controller. Please refer to the current version of IMM
WMC for information relating to the unit itself.

Electric shock hazard. Improper handling of this equipment can cause personal injury or

equipment damage. This equipment must be properly grounded. Connections to and

service of the MicroTech II control panel must be performed only by personnel that are

Static sensitive components. A static discharge while handling electronic circuit boards

WARNING

knowledgeable in the operation of the equipment being controlled.

CAUTION

can cause damage to the components. Discharge any static electrical charge

by touching the bare metal inside the control panel before performing

any service work. Never unplug any cables, circuit board terminal blocks,

or power plugs while power is applied to the panel.

NOTICE

This equipment generates, uses and can radiate radio frequency energy and,

if not installed and used in accordance with this instruction manual,

may cause interference to radio communications. 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 the owner’s own expense.

McQuay disclaims any liability resulting from any interference or for the correction thereof.

Temperature and humidity considerations

The unit controllers are designed to operate within an ambient temperature range of 20°F to
+130°F (-7°C to +54°C) with a maximum relative humidity of 95% (non-condensing).

OMM WMC-3 OITS 3

Features of the Control Panel

• Control of leaving chilled water within a ±0.2°F (±0.1°C) tolerance.

• Display of the following temperatures and pressures on a 12-inch Super VGA touch-screen

operator interface (depending on date of manufacture):

• Entering and leaving chilled water temperature

• Enter and leaving condenser water temperature

• Saturated evaporator refrigerant temperature and pressure

• Saturated condenser temperature and pressure

• Outside air temperature (optional)

• Suction line, liquid line and discharge line temperatures, calculated superheat for discharge

and suction lines, and calculated subcooling for liquid line

• Automatic control of primary and standby evaporator and condenser pumps.

• Control of up to 4 stages of cooling tower fans plus modulating bypass valve and/or tower fan

VFD. Although fan staging is available, continuous, modulated control of tower capacity is
preferred and recommended.

• History trend feature that will constantly log chiller functions and setpoints. The controller will
store and display all accumulated data for recall in a graphic format on the screen. Data can be
downloaded for archival purposes.

• Three levels of security protection against unauthorized changing of setpoints and other control
parameters.

• Plain language warning and fault diagnostics to inform operators of most warning or fault
conditions. Warnings, problems and faults are time and date stamped for identification of when
the fault condition occurred. In addition, the operating conditions that existed just prior to
shutdown can be recalled to aid in resolving the cause of the problem.

• Twenty-five previous faults and related operating conditions are available from the display. Data
can be exported for archival purposes via a 3.5-inch floppy drive or other device (depending on
date of manuafacture).

• Soft loading feature reduces electrical consumption and peak demand charges during system
loop pulldown.

• Remote input signals for chilled water reset, demand limiting and unit enable.

• Manual control mode allows the service technician to command the unit to different operating

states. Useful for system checkout.

• BAS communication capability via L
most BAS manufacturers.

• Service Test mode for troubleshooting controller outputs.

• Pressure transducers for direct reading of system pressures.

• Preemptive control of low evaporator and high discharge pressure conditions to take corrective

action prior to a fault trip.

ONTALK®, Modbus® or BACnet® standard protocols for

4 OMM WMC-3 OITS

Definitions

Active Setpoint

The active setpoint is the parameter setting in effect at any given moment. This variation can occur
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 capacity 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.

Active-Amp-Limit

Active amp limit is the actual amp limit imposed by an outside signal such as the load limit
function.

Condenser Recirc (Recirculation) 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 sensors to take a more accurate reading of the
condenser water temperature.

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 44°F and it has a dead band of ± 2.0 degrees F, nothing will happen until the measured
temperature is less than 42°F or more than 46°F.

DIN

Digital input, usually followed by a number designating the number of the input.

Discharge Superheat

Discharge superheat is calculated 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

Evap Hold-loading

This is a setpoint that establishes the minimum evaporator pressure to which the chiller is allowed
to go. It signals that the unit is at full load so the no further loading will occur that would lower the
pressure even further.

Evap Recirc (Evaporation Recirculation) 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 to take a more accurate
reading of the chilled water temperature.

EXV

Electronic expansion valve, used to control the flow of refrigerant to the evaporator, controlled by
the circuit microprocessor.

OMM WMC-3 OITS 5

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. Used to limit unit power input.

Load Balance

Load balance is a technique that equally distributes the total unit load between two or more running
compressors.

Low Pressure Hold (Inhibit) Setpoint

The psi evaporator pressure setting at which the controller will not allow further compressor
loading. “Hold” and “Inhibit” are used interchangeably.

Low Pressure Unload Setpoint

The psi evaporator pressure setting at which the controller will unload the compressor in an effort
to maintain the minimum setting.

LWT

Evaporator leaving water temperature. The “water” is any fluid used in the chiller circuit.

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 44°F and the actual temperature of the water at a given
moment is 46°F, the LWT error is +2 degrees.

LWT Slope

The LWT slope is an indication of the trend of the chilled 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.

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.

OITS

Operator Interface Touch Screen, one screen per unit provides operating data visually and
accommodates setpoint entry.

pLAN

Peco Local Area Network is the proprietary name of the network connecting the control elements.

Refrigerant Saturated Temperature

Refrigerant saturated temperature is calculated from the pressure sensor readings. 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).

6 OMM WMC-3 OITS

SP

Setpoint

Suction Superheat

Suction superheat is calculated for each circuit using the following equation:
Suction Superheat = Suction Temperature – Evaporator Saturated Temperature

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.

VDC

Volts, Direct current, sometimes noted as vdc.

VFD

Variable Frequency Drive, a device located on the compressor, used to vary the compressor speed.

OMM WMC-3 OITS 7

f

General Description

Major Components

Figure 1, Major Component Location

Unit Control Panel

Evaporator Relie

Valve

Operator

Interface Panel

Compressor #1
with On-Board

Compressor #2
with On-Board
Controls

Condenser

Relief Valves

Optional Unit Disconnect Switch

& Single Point Power Connection

Circuit #1
Power Panel

Electronic Expansion Valve

Circuit #2
Power Panel

General Description

The centrifugal MicroTech ΙΙ control system consists of microprocessor-based controllers in the
control panel, as well as on-board the compressors, providing monitoring and control functions
required for the controlled, efficient operation of the chiller. The system consists of the following
components:

• Operator Interface Touch Screen (OITS), one per unit-provides unit information and is the
primary setpoint input instrument. It has no control function.

• Unit Controller, one per chiller-controls unit functions and communicates with all other
controllers. It is the secondary location for setpoint input if the OITS is inoperative. It is
located in the control panel that is adjacent to the OITS Panel.

• Compressor Controller for each compressor-controls compressor functions. They are located
in the control panel.

• On-board compressor controller mounted on each compressor that monitors compressor
operation and controls bearing operation.

The operator can monitor all operating conditions by using the unit-mounted OITS. 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 conditions. If a fault condition develops, the controller will shut a compressor, or
the entire unit, down 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.

8 OMM WMC-3 OITS

The system is password protected and only allows access by authorized personnel. The operator
must enter the password into the touch screen (or one of the controller's keypad) before any
setpoints can be altered.

NOTE: It is important to understand that the OITS is the operator interface device under normal
conditions. If, and only if, it is unavailable, should the unit controller be used to change setpoints
or operate the chiller.

Figure 2, Major Control Components

Comm. Module

Universal

pLAN

OPERATOR

INTERFACE

TOUCH-SCREEN

UNIT

CONTROLLER

#1 COMPRESSOR

CONTROLLER

#2 COMPRESSOR

CONTROLLER

BAS

Onboard
Control

Onboard
Control

Color Graphics

Touch-Screen Interface

View Data, Input Setpoints

Stores History

UNIT

Analog Inputs

Analog Outputs

Digital Inputs

Digital Outputs

COMPRESSOR

Analog Inputs

Analog Outputs

Digital Inputs

Digital Outputs

OMM WMC-3 OITS 9

Control Panel

The unit and compressor
controllers along with unit and
compressor on/off switches are
mounted in the unit control panel,
which is mounted adjacent to the
OITS panel. See
switches are designated “I” for on
and “0” for off. The compressor
on/off switch should only be used
when an immediate stop is
required since the normal shut
down sequence is bypassed.

The switch panel also has a Circuit
Breaker that interrupts power to
the cooling tower fans, valves and
evaporator and condenser pumps,
if any of these are tied into the
MicroTech II controller for control
of their operation. If these
components operate independently
from the chiller control, the
breaker has no effect.

The unit controller's primary
function is processing data relating
to the entire chiller
as compared to data relating to the

compressor operation. The unit

controller processes information
and sends data to the compressor
controllers and devices and relays information to the OITS for graphic display. It has a 4x20 LCD
display and keys for accessing data and changing setpoints. The controller LCD can display most
of the same information as the OITS and can operate the chiller independently if the OITS is not
available.

Figure 1. The

unit operation

Figure 3, Control Panel Interior

Switch Panel and

Switches, See Below.

Unit Controller

SW5, Emergency

Shutdown Switch,

Outside Panel

USB Port Located on

PC Located in this Area

Compressor #1

Controller

Compressor #2

Controller

Figure 4, Switch Locations

Compressor #1 Switch

Compressor #2 Switch

SWT 5, Emergency

Shutdown Switch

Outside Panel

Unit Switch

Circuit breaker

10 OMM WMC-3 OITS

Use with On-Site Generators

WMC chillers have their total tonnage divided between two compressors that start sequentially and they are
operated with variable frequency drives. These features make WMC chillers especially appropriate for use
in applications where they may be required to run with on-site electrical generators. This is particularly
true when the generators are used for temporary power when the utility power is lost.

Starting/Stopping Procedure: The stopping of the chiller in the event of a power failure should be

uneventful. The chiller will sense a loss of voltage and the compressors will stop, coasting down using
power generated from their dynamic braking to maintain the bearing magnetic field. The stop signal will
initiate a three-minute stop-to-start timer, effectively preventing compressor restart for three minutes. The
timer is adjustable from three to fifteen minutes, but the recommended, and default value, is three minutes.
This interval allows the generator sufficient time to get up to speed and stabilize. The chiller will restart
automatically when the start-to-start timer expires.

Transfer Back to Grid Power: Proper transfer from stand-by generator power back to grid power is

essential to avoid compressor damage.

Stop the chiller before transferring supply power from the generator back to the utility
power grid. Transferring power while the chiller is running can cause severe
compressor damage.

The necessary procedure for reconnecting power from the generator back to the utility grid is show below.
These procedures are not peculiar to McQuay units only, but should be observed for any chiller
manufacturer.

CAUTION

1. Set the generator to always run five minutes longer than the unit start-to-start timer, which could be set
from 15 to 60 minutes. The actual setting can be viewed on the operator interface panel on the
Setpoint/Timer screen.

2. Configure the transfer switch, provided with the generator, to automatically shut down the chiller
before transfer is made. The automatic shut-off function can be accomplished through a BAS interface
or with the “remote on/off” wiring connection shown in
after the stop signal since the three-minute start-to-start timer will be in effect.

Chiller Control Power: For proper operation on standby power, the chiller control power must remain as

factory-wired from a unit-mounted transformer. Do not supply chiller control power from an external
power source because the chiller may not sense a loss of power and do a normal shutdown sequence.

Figure 9. A start signal can be given anytime

OMM WMC-3 OITS 11

Sequence of Operation

Start-up of WMC Compressors:
“Next On” status

If none of the “OFF” conditions are true, then all the MicroTech II compressor controls in a
network of up to 2 units (four compressors) will pole the status of each to determine the one having
“Next On” status, which is usually the compressor with the least starts. This takes about one
minute.

Evap (Evaporator) Pump Start

Once this is determined, the unit controller of the chiller with the ‘Next On’ compressor (when
there are two chillers) will start the evaporator pump and determine if there is load based on the
water temperature. This is determined if the leaving evaporator water is above the ‘LWT Setpoint’
plus ‘Startup Delta T’. If there is no load, based on the temperature, the unit is in the state of
‘Awaiting Load’.

Interlock On

If there is load, the unit waits for the Evaporator Recirculation Timer period (default value of 30
seconds) and starts the Interlock Timer for 10 sec.

Cond (Condenser) Pump Start

After Interlock is confirmed, the controller starts the Condenser Pump and checks for condenser
flow before starting the first compressor.

Compressor Start

Starting the compressor is accomplished by setting the Demand to 25% of the MAX KW setpoint.
When the actual RPM of the compressor exceeds 350 RPM, the demand setting is allowed to be
governed by the normal control logic.

Compressor Run

The compressor that is running will signal all other compressors when it reaches full load.
Full load status is determined when

1. Percent RLA exceeds 100% or the Active-Amp-Limit from an external-limiting source.

2. Evap Saturation pressure drops below the Evap Hold-Loading pressure setpoint.

3. Actual compressor RPM exceeds 97% of Max RPM limit from compressor.

any one of the following tests is true:

Lag Compressor Staging

The ‘Next On’ compressor, will initiate the following staging sequence when it receives a Full
Load indication from the Lead compressor, or all other running compressors in the case of a four
compressor (two units) setup.

12 OMM WMC-3 OITS

The lag compressor will start (Demand set to 25% of Max KW setpoint). When the actual RPM
exceeds 350 RPM, the lead compressor will unload to 25% of the MAX KW setpoint. The lead
compressor will maintain this demand setting for a time period set by the Step-Down timer (found
in Set COMP1 SPs (8) ). When the Step–Down timer expires, both compressors should be nearly
matched in capacity and can began amp balancing to share the load equally.

Note: If the “Next On” compressor is on another chiller, the controller will start that chiller’s

evaporator and condenser pumps, if they are separate from the lead unit’s pumps. Only
compressors on the same unit will unload the lead compressor before starting the lag compressor.

Unloading compressors:

The setpoint of ‘Nominal Capacity’ is used for defining the point to unload a compressor on a
single or two-chiller system. With each compressor having its ‘Nominal Capacity’ defined, then
the network, which is load balanced, continues to unload at 0.2 tenths or more below setpoint.
Each compressor keeps computing the spare capacity of the network. When the designated ‘Next
Off’ sees enough spare capacity, it will turn off. Then similarly, in about 40 seconds, a new
compressor will be designated as the ‘Next Off’ and the spare capacity will continue to be
calculated between the remaining compressors. Compressors continue to unload and stage off until
there is only one compressor running. It will shut off when the water temperature reaches the LWT
Setpoint minus the Shutdown Delta T.

Multi-Chiller Setup

Component Description

pLAN Setup

The pLAN communication wiring and setup required for dual compressor operation is
setup in the factory and should be reviewed when the chiller is initially started after
installation or if there is any change made in the chiller control hardware.
pLan RS485 communication wiring between chillers should be field wired before start-up
and installed as a NEC Class 1 wiring system.

Table 1, Address DIP Switch Settings for Controllers Using pLAN).

Chiller Comp 1 Comp 2

A

B

NOTES:

1 2 5 6 7 8

100000 010000 101000 011000 111000 000100

9 10 13 14 15 16

100100 010100 101100 011100 111100 000010

Unit

Controller

Reserved

1. Two WMC units can be interconnected.

2. The interface setting is not a DIP switch setting. The ‘Operator Interface Touch Screen’ (OITS)
address is selected by selecting the ‘service’ set screen. Then, with the Technician level
password active, select the ‘pLAN Comm’ button. Buttons A(7), B(15), C(23), D(31) will
appear in the middle of the screen, then select the letter for the OITS address for the chiller that
it is on. Then close the screen. Note that A is the default setting from the factory.

3. There are six Binary DIP Switches: Up is ‘On’, indicated by ‘1’. Down is ‘Off’, indicated by
‘0’. They are slide and not rocker switches. They are located on the upper-left corner of the
face of the controller.

Operator
Interface

Reserved

OMM WMC-3 OITS 13

Operator Interface Touch Screen (OITS) Settings

Settings for any type of linked multiple compressor operation must be made to the MicroTech II
controller. Settings on a dual compressor unit are made in the factory prior to shipment, but must
be verified in the field before startup. Settings for multiple chiller installations are set in the field
on the Operator Interface Touch Screen as follows:

Maximum Co mpr esso rs O N

– SETPOINTS - MODES screen, Selection #10 = 2 for a WMC, 4 for

2 WMCs.
Sequence and Staging

– SETPOINTS - MODES screen, Selection #11 & #13; #12 & #14.
Sequence sets the sequence in which compressors will start. Setting all to “1” evokes the automatic
lead/lag feature and is the preferred setting.

Nominal Capacity

– SETPOINTS - MOTOR screen, Selection #10. The setting is the compressor

design tons. Compressors on dual units are always of equal capacity.

pLAN Setup

1. With no pLAN connections between chillers, disconnect control power and set the DIP

switches as shown in

2. With all manual switches off, turn on control power to each chiller and set each OITS address

(see Note 2 above).

3. Verify correct nodes on each OITS Service Screen.

4. Connect chillers together (pLAN, RS485, between pLAN connections on each unit’s UCM or

J10 and J11 terminals on the unit controller. The UCM board part number is 330276202 and
can be ordered with this units or separately after shipment.

5. Verify correct nodes on each OITS Service Screen. See

Table 1.

Figure 27 on page 52.

14 OMM WMC-3 OITS

Operating the Control System

Interface Panel On/Off

The Operator Interface Panel is turned on and off with a push-push switch located at the upper-left
corner of the panel. ON is the outermost switch position and a white band will be visible on the
switch stem. Off is innermost and no white is visible.

The screen is equipped with a screen saver that blackens the screen. Touching the screen anywhere
reactivates the screen. If the screen is black, touch it first to be sure it is on before using the
ON/OFF switch.

Start/Stop Unit

There are four ways to start or stop the chiller. Three are shown below and selected in SETPOINT\
MODE\SP3; the fourth way is through panel-mounted switches:

1. Operator Interface Panel (LOCAL)

Home Screen 1 has AUTO and STOP buttons that are only active when the unit is in "LOCAL
CONTROL". This prevents the unit from being accidentally started or stopped when it is normally
under control from a remote switch or BAS. When these buttons are pressed, the unit will cycle
through its normal starting or stopping sequence.

2. Remote SWITCH

Selecting SWITCH in SP3 will put the unit under the control of a remote switch that must be wired
into the control panel (see

Figure 9 on page 31).

3. BAS

BAS input is field-wired into a module that is factory-installed on the unit controller.

Control Panel Switches

The unit control panel, located adjacent to the Interface Panel, has switches inside the panel for
stopping the entire unit or individual compressors. When the UNIT switch is placed in the OFF
position the chiller will shut down through the normal shutdown sequence, whether one or two
compressors are on.

The COMPRESSOR switches will immediately shut down the compressor without going through
the shutdown sequence when placed in the OFF position. It is equivalent to an emergency stop
switch.

Change Setpoints

Setpoints are easily changed on the Operator Interface Touch Screen (OITS). A complete
description of the procedure begins on page
controller, but this is not recommended except in an emergency, when the OITS is unavailable.

40. Setpoints can also be changed in the unit

Alarms

A red ALARM light in the lower middle of any screen is illuminated if there is an alarm. If the
optional remote alarm is wired in, it too will be energized.

There are three types of alarms:

• Fault, equipment protection alarms that shut a unit or compressor off.

• Problem, limit alarms that limit compressor loading in response to an out-of-normal condition.

If the condition that caused a limit alarm is corrected, the alarm light will be cleared
automatically.

• Warning, notification only, no action taken by controller.

OMM WMC-3 OITS 15

Any type will light the ALARM light. Procedures for dealing with alarms are shown below:

1. Press the alarm light button. This will go directly to the ACTIVE ALARMS screen.

2. The alarm description (with date stamp) will be shown.

3. Press the ACKNOWLEDGE button to recognize the alarm.

4. Correct the condition causing the alarm.

5. Press the CLEAR button to clear the alarm from the controller. If the fault condition is not

fixed, the alarm will continue to be on and the unit will not be able to be restarted.

Component Failure

Chiller Operation without the Operator Interface Panel

The Interface Panel communicates with the unit and compressor controllers, displaying data and
transmitting touch screen inputs to the controllers. It does no actual controlling and the chiller can
operate without it. Should the Touch Screen become inoperable, no commands are necessary for
continuing unit operation. All normal inputs and outputs will remain functional. The unit
controller can be used to view operational data, to clear alarms and to change setpoints, if
necessary.

Component Description

Operator Interface Touch Screen

The operator interface touch screen (OITS) is the
primary device for entering commands and entries
into the control system. (Settings can also be made
directly into the unit controller.) The OITS can also
display controller data and information on a series of
graphic screens. A single OITS is used per unit.

Selected information from the OITS panel can be
down-loaded via a USB port located in the unit
control panel.

The OITS panel is mounted on a moveable arm to
allow placement in a convenient position for the
operator.

There is a screen-saver programed into the system. The screen is reactivated by touching it
anywhere.

Unit/Compressor Controller Description

Hardware Structure

The controllers are fitted with a microprocessor for running the control program. There are
terminals for connection to the controlled devices (for example: solenoid valves, tower fans,
pumps). The program and settings are saved permanently in FLASH memory, preventing data loss
in the event of power failure, without requiring a back-up battery.

Each controller connects to other controllers, the on-board compressor microprocessors and the
OITS via a local communications network (pLAN). The unit controller also has remote
communication capability for BAS interface.

16 OMM WMC-3 OITS

A

t

Keypad

A 4 line by 20 character/line liquid crystal display and 6-button keypad is mounted on the unit and
compressor controllers. Its layout is shown below.

Figure 5, Controller Keypad

Key-to-Screen Pathway

Air Conditioning

LARM

<

VIEW

<

SET

<

MENU Key

ARROW Keys (4)

ENTER Key with

Green Run Ligh

Behind

The four arrow keys (UP, DOWN, LEFT, RIGHT) have three modes of use:

• Scroll between data screens in the direction indicated by the arrows (default mode).

• Select a specific data screen in the menu matrix using dynamic labels on the right side of the

display such as ALARM, VIEW, etc (this mode is entered by pressing the MENU key). For
ease of use, a pathway connects the appropriate button to its respective label on the screen.

• Change field values in setpoint programming mode according to the following table:

LEFT key = Default RIGHT key = Cancel
UP key = Increase (+) DOWN key = Decrease (-)
These four programming functions are indicated by one-character abbreviation on the right side of
the display. This programming mode is entered by pressing the ENTER key.

Getting Started

There are two basic procedures to learn in order to utilize the MicroTech II controller:

1. Navigating through the menu matrix to reach a desired menu screen and knowing where a
particular screen is located.

2. Knowing what is contained in a menu screen and how to read that information or how to
change a setpoint contained in the menu screen.

Navigating

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 location of each controller’s screens can be
found in the following table:

Controller Screen Matrix Screen Details

Unit Page 58 Page 60
Compressor Page 75 Not Applicable

There are two ways to navigate through the menu matrix to reach a desired menu screen.

1) One is to scroll through the matrix from one screen to another using the four ARROW keys.

2) Another way is to use shortcuts to work through the matrix hierarchy. From any menu screen,
a) Pressing the MENU key will take you to the top level of the hierarchy. The display will

show ALARM, VIEW, and SET as shown in

Figure 5. One of these choices can then be

selected by pressing the key connected to it via the pathway shown in the figure.

OMM WMC-3 OITS 17

b) Depending on the top-level selected, a second level of screens will appear. For example,

selecting ALARM will go the next level of menus under ALARM (ALARM LOG or
ACTIVE ALARM). Selecting VIEW will go the next level of menus (VIEW
COMPRESSOR STATUS, VIEW UNIT STATUS, VIEW EVAPORATOR, or VIEW
CONDENSER). Selecting SET will go to a series of menus for looking at and changing
setpoints.

c) After selecting this second level, the desired screen can be acquired using the arrow keys.

A typical final screen is shown below.

Pressing the MENU key from any menu screen will automatically return you to the MENU mode.

Figure 6, Typical Menu Display and Keypad Layout

MENU Key

Air Conditioning

VIEW UNIT STATUS
Unit = COOL
Compr. #1/#2=OFF/OFF
Evap Pump = RUN

ARROW Keys

ENTER Key

Menu Screens

A hierarchical menu structure is used to access the various screens. Each menu screen can have
one to four lines of information. Optionally, the last menu selection can access one of a set of
screens that can be navigated with the UP/DOWN arrow keys (see the scrolled menu structure
below). Menu selection is initiated by pressing the MENU key, which changes the display from a
data screen to a menu screen. Menu selections are then made using the arrow keys according to
labels on the right side of the display (the arrows are ignored). When the last menu item is
selected, the display changes to the selected data screen. An example follows showing the
selection of the “VIEW COMPRESSOR (n) screen. Suppose the initial screen is:

ALARM LOG
(data)
(data)

After pressing the MENU button, the top-level menu screen will
show:

(data)

< ALARM
< VIEW
< SET

After pressing the “VIEW” menu button, a menu screen will
show:

<

VIEW < COMPRESSOR
< UNIT
< EVAPORATOR

After pressing the “COMPRESSOR” menu button, the selected
data screen will show

< CONDENSER

VIEW COMP (n)
(screen n data)
(screen n data)
(screen n data)

.

18 OMM WMC-3 OITS

Where “n” is the number of the last viewed COMPRESSOR
screen. The arrow keys will automatically return to the
“scroll” mode at this time. Different compressor screens can
then be selected with the UP/DOWN arrow keys

Unit Controller

Table 2, Unit Controller, Analog Inputs

# Description Signal Source Range

1 Reset of Leaving Water Temperature 4-20 mA Current 0-(10 to 80°F)

Entering Evaporator Water

2

Temperature
Entering Condenser Water

3

Temperature
4 Leaving Condenser Water Temperature NTC Thermistor (10k@25°C) -58 to 212°F
5 Liquid Line Refrigerant Temperature NTC Thermistor (10k@25°C) -58 to 212°F
6 Demand Limit 4-20 mA Current 0-100 %RLA
7 Evaporator Water Flow 4 to 20 mA Current 0 to 10,000 gpm
8 Condenser Water Flow 4 to 20 mA Current 0 to 10,000 gpm
9 Refrigerant Leak Sensor 4 to 20 mA Current 0 to 100 ppm

10 Spare

Table 3, Unit Controller, Digital Inputs

# Description Signal Signal

1 Unit OFF Switch 0 VAC (Stop) 24 VAC (Auto)
2 Remote Start/Stop 0 VAC (Stop) 24 VAC (Start)
3 Not Used
4 Evaporator Water Flow Switch 0 VAC (No Flow) 24 VAC (Flow)
5 Condenser Water Flow Switch 0 VAC (No Flow) 24 VAC (Flow)

NTC Thermistor (10k@25°C) -58 to 212°F
NTC Thermistor (10k@25°C) -58 to 212°F

Table 4, Unit Controller, Digital Outputs

# Description Load Output OFF Output ON

1 Evaporator Water Pump #1 Pump Contactor Pump OFF Pump ON
2 Evaporator Water Pump #2 Pump Contactor Pump OFF Pump ON
3 Condenser Water Pump #1 Pump Contactor Pump OFF Pump ON
4 Condenser Water Pump #2 Pump Contactor Pump OFF Pump ON
5 Tower Fan #1 Fan Contactor Fan OFF Fan ON
6 Tower Fan #2 Fan Contactor Fan OFF Fan ON
7 Spare
8 Alarm Alarm Indicator Alarm OFF Alarm ON
9 Tower Fan #3 Fan Contactor Fan OFF Fan ON

10 Tower Fan #4 Fan Contactor Fan OFF Fan ON

Table 5, Unit Controller, Analog Outputs

# Description Output Signal Range

1 Cooling Tower Bypass Valve Position 0 to 10 VDC 0 to 100% Open
2 Cooling Tower VFD Speed 0 to 10 VDC 0 to 100%
3 EXV signal to IB Valve Control Bd. 0 to 10 VDC 0 to 100%
4 Y3 Electronic Expansion Valve 0 to 10 VDC 0 to 100% Open

Unit Controller Setpoints

The following parameters are remembered during power off, are factory set to the Default value,
and can be adjusted to any value in the

The “Type: column defines whether the setpoint is part of a coordinated set of duplicate setpoints
in different controllers. There are three possibilities as given below:

Range column.

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
S = Slave setpoint - Setpoint is a copy of the master setpoint (in the unit controller)

OMM WMC-3 OITS 19

At power-up the slave node checks if the master node is operational and if so, it sets its copy of the
setpoint equal to the master’s. Otherwise, the setpoint remains unchanged. During normal
operation, any time the master setpoint changes, the slave is updated as well.

The PW (password) column indicates the password that must be active in order to change the
setpoint. Codes are as follows:

O = Operator, M = Manager, T = Technician (not available through the 4x20 display/keypad)

The following table groups setpoints that relate to the entire unit operation and are stored, for the
most part, in the unit controller. All settings are made through the OITS, indiscriminately as to
whether they are “unit” or “compressor”.

Table 6, Unit Controller Setpoints

Description Default Range Type PW

Unit

Unit Enable OFF OFF, ON M O Pg. 50
Control Source KEYPAD
Display Units

Language ENGLISH ENGLISH, (TBD) N O -­BAS Protocol NONE

Leaving Water

Cool LWT
Startup Delta T
Shutdown Delta T
LWT Reset Type NONE NONE, RETURN, 4-20mA N M Pg. 22
Max Reset Delta T
Start Reset Delta T

Timers

Evap Recirculate 30 sec 15 sec to 5 min N M Pg. 5

Pumps

Evap Pump
Cond Pump

Cooling Tower

Tower Control None None, Temperature, Lift N M Pg. 46
Tower Stages 2 1 to 4 N M Pg. 46
Stage Up Time 2 min 1 to 60 min N M Pg. 46
Stage Down Time 5 min 1 to 60 min N M Pg. 46
Stage Differential (Temp)
Stage Differential (Lift) 6.0 psi 1.0 to 20.0 psi N M Pg. 46
Stage #1 On (Temp)
Stage #2 On (Temp)
Stage #3 On (Temp)
Stage #4 On (Temp)
Stage #1 On (Lift) 35 psi 10 to 130 psi N M Pg. 46
Stage #2 On (Lift) 45 psi 10 to 130 psi N M Pg. 46
Stage #3 On (Lift) 55 psi 10 to 130 psi N M Pg. 46
Stage #4 On (Lift) 65 psi 10 to 130 psi N M Pg. 46

Cooling Tower Valve / VFD

Valve/VFD Control None
Valve Setpoint (Temp)

Valve Setpoint (Lift) 30 psi 10 to 130 psi N M Pg. 46
Valve Deadband (Temp)
Valve Deadband (Lift) 4.0 psi 1.0 to 20.0 psi N M Pg. 46

°F/psi °F/psi, °C/kPa

None, Local, Remote, BACnet, LON,

44. 0°F 40.0 to 80.0 °F

3.0°F 0.0 to 10.0 °F

3.0°F 0.0 to 3.0 °F

0.0°F 0.0 to 20.0 °F

10. 0°F 0.0 to 20.0 °F

Pump #1

Only

Pump #1

Only

3.0 °F 1.0 to 10.0 °F

70 °F 40 to 120 °F
75 °F 40 to 120 °F
80 °F 40 to 120 °F
85 °F 40 to 120 °F

65 °F 40 to 120 °F

2.0 °F 1.0 to 10.0 °F

Pump #1 Only, Pump #2 Only, Auto
Pump #1 Only, Pump #2 Only, Auto

None, Valve Setpoint, Valve Stage,

VFD Stage, Valve SP/VFD Stage

KEYPAD, BAS,

DIGITAL INPUT

MODBUS, CSC

Lead, #1 Primary, #2 Primary
Lead, #1 Primary, #2 Primary

N O Pg. 50
N O --

N M Pg. 50, Pg 77

M O Pg. 11, Pg. 51
M O Pg. 11, Pg. 51
M O Pg. 11, Pg. 51

N M Pg. 22
N M Pg. 22

N M Pg. 65
N M Pg. 65

N M Pg. 46

N M Pg. 46
N M Pg. 46
N M Pg. 46
N M Pg. 46

N M Pg. 46
N M Pg. 46

N M Pg. 46

Continued on next page

Manual

Reference

20 OMM WMC-3 OITS

Description Default Range Type PW

Stage Down @ 20% 0 to 100% N M Pg. 46
Stage Up @ 80% 0 to 100% N M Pg. 46
Valve Control Range (Min) 10% 0 to 100% N M Pg. 46
Valve Control Range(Max) 90% 0 to 100% N M Pg. 46

Valve Type
Minimum Start Position 0% 0 to 100% N M Pg. 46

Minimum Position @
Maximum Start Position 100% 0 to 100% N M Pg. 46
Maximum Position @
Error Gain 25 10 to 99 N M Pg. 46
Slope Gain 25 10 to 99 N M Pg. 46

NC

(To Tower)

60 °F 0 to 100 °F

90 °F 0 to 100 °F

NC, NO N M Pg. 46

N M Pg. 46

N M Pg. 46

Manual

Referance

These setpoints are normally viewed or changed on the OITS.

Faults, Problems, Warnings

Faults (Equipment Protection Shutdowns)

There are no Unit protection shutdown alarms; all such alarms are handled through the compressor
controllers.

Problems (Limit Alarms)

The following alarms limit operation of the chiller in some way as described in the Action Taken
column.

Table 7, Unit Controller Limit Alarms

Description Occurs When: Action Taken Reset

Evaporator Pump #1
Fault

Evaporator Pump #2
Fault

Condenser Pump #1
Fault

Condenser Pump #2
Fault

Entering Evaporator
Water Temperature
Sensor Fault

No flow indicated for (5 sec) with Evaporator Pump #1 ON

AND [the other pump is available (per the Evap Pump SP)

AND has not faulted]
No flow indicated for (5 sec) with Evaporator Pump #2 ON
AND [the other pump is available (per the Evap Pump SP)

AND has not faulted]
No flow indicated for (5 sec) with Condenser Pump #1 ON
AND [the other pump is available (per the Evap Pump SP)

AND has not faulted]
No flow indicated for (5 sec) with Condenser Pump #2 ON
AND [the other pump is available (per the Evap Pump SP)

AND has not faulted]

Sensor fault AND leaving water reset is based on entering

water

Start pump #2 Manual

Start pump #1 Manual

Start pump #2 Manual

Start pump #1 Manual

Manual.

Reset mode is

set to No Reset

(Reset mode
goes back to

Entering

Water)

Warnings

The following “alarms” only generate a warning message to the operator. Chiller operation is not
affected.

Table 8, Unit Controller Warnings

Description Occurs When: Action Taken Reset

Entering Evaporator Temperature Sensor Fault Sensor is open or shorted Annunciation Automatic
Entering Condenser Temperature Sensor Fault Sensor is open or shorted Annunciation Automatic
Leaving Condenser Temperature Sensor Fault Sensor is open or shorted Annunciation Automatic
Liquid Line Refrigerant Temperature Sensor Fault Sensor is open or shorted Annunciation Automatic

OMM WMC-3 OITS 21

Unit Controller Functions

Leaving Water Temperature (LWT) Reset

The Active Leaving Water variable shall be set to the current Leaving Water Temperature (LWT)
setpoint unless modified by one of the reset methods below. (The current LWT setpoint is Cool
LWT as determined by the chiller mode.) The type of reset in effect is determined by the LWT
Reset T ype setpoint.

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.
When the chiller mode = COOL, the Active Leaving Water variable is reset using the following

parameters:

1. Cool LWT setpoint

2. Max Reset Delta T setpoint

3. Start Reset Delta T setpoint
Reset is accomplished by changing the Active Leaving Water variable from the (Cool LWT

setpoint) to the (Cool LWT setpoint + Max Reset Delta T setpoint) when the evaporator (return –
leaving) water temperature delta varies from the (Start Reset Delta T setpoint) to 0.

The Active Leaving Water variable is set equal to the Cool LWT setpoint if the reset signal is less
than or equal to 4 mA. It is set equal to (Cool LWT setpoint + Max Reset Delta T setpoint) if the
reset signal equals or exceeds 20 mA. The Active Leaving Water variable will vary linearly
between these extremes if the reset signal is between 4 mA and 20 mA. An example of this action
is shown below.

LWT Reset (Cool mode)

(temperatures are examples only)

(54.0°F)

Max Reset Delta T

(10.0°F)

Cool LWT Set-Point

(44.0°F)

0 ma

4 ma

20 ma

22 OMM WMC-3 OITS

Compressor Controller

The compressor controller's primary function is controlling and protecting the compressor. No
setpoints are input to it. There is one compressor controller for each compressor on the unit. The
compressor controller receives, processes, and sends data to the unit controller, the compressor on­board microprocessors and to external devices. With some operator intervention the compressor
controller can operate the compressor if the operator interface touch screen is unavailable. Inputs
and outputs are as follows:

Table 9, Compressor Controller, Analog Inputs

# Description Signal Source Range

Leaving Evaporator Water

1

Temperature
2 Spare
3 Motor Current 0 to 5 VDC 0 to 125% RLA

Table 10, Compressor Controller, Digital Inputs

# Description Signal Signal

1 Manual Off 0 VAC (Off) 24 VAC (Auto)
2 Spare
3 Spare
4 Spare
5 Spare
6 Spare
7 Evaporator Water Flow Switch 0 VAC (No Flow) 24 VAC (Flow)
8 Condenser Water Flow Switch 0 VAC (No Flow) 24 VAC (Flow)
9 Spare

NTC Thermistor

(10k@25°C)

-58 to 212°F

Table 11, Compressor Controller, Analog Outputs

# Description Output Signal Range

1 Spare

Table 12, Compressor Controller, Digital Outputs

# Description Load Output OFF Output ON

1 Compressor Off Emer. Solenoid Circuit Breaker ON
2 Spare

3 Spare
4 Spare
5 Spare
6 Spare
7 Spare
8 Inter Lock Solenoid Comp Disabled OFF Comp. Enabled ON
9 Spare

Circuit Breaker

OFF

OMM WMC-3 OITS 23

Compressor Controller Setpoints

The following parameters in Table 13 are remembered during power off, are factory set to the

Default value, and can be adjusted to any value in the Range column.

Type: column defines whether the setpoint is part of a coordinated set of duplicate setpoints

The “
in different controllers. The possibilities are given below:

• N = Normal setpoint - Not copied from, or copied to, any other controller.

• D = Duplicate setpoint. Setpoint is duplicated (same value) in all compressor controllers on the

same chiller.

• G = Group setpoint. Setpoint is duplicated (same value) in all compressor controllers on all

chillers in a group.

• M = Master setpoint - Setpoint is copied to all controllers in the “Sent To” column.

• S = Slave setpoint - Setpoint is a copy of the master setpoint (in the Unit controller).

At power-up the slave controller checks if the master is operational and if so, it sets its copy of the
setpoint equal to the master’s. Otherwise, the setpoint remains unchanged. During normal
operation, any time the master setpoint changes, the slave is updated as well.

PW (password) column indicates the password that must be active in order to change the

The
setpoint. Codes are as follows:

O = Operator, M = Manager, T = Technician (not available through the 4x20 display/keypad)

The following table groups setpoints that relate to compressor operation and are stored, for the
most part, in the compressor controllers. All settings are made through the OITS, indiscriminately
as to whether they are “unit” or “compressor”.

Table 13, Compressor Controller Setpoints

Description Default Range Type PW

Motor Amps

Demand Limit OFF OFF, ON N O
Minimum Amps 40% 20 to 80% N T
Maximum Amps 100% 40 to 100% N T
Soft Load OFF OFF, ON D M
Begin Amp Limit 40% 20 to 100% N M
Soft Load Ramp 5 min 1 to 60 min D M
Maximum Rate
Minimum Rate

Staging

Mode Normal
Sequence # 1

Maximum Compressors ON 16 1-16 G M
Stage Delta T 1.0 0.5-5.0 G M
Full Load 120 sec 30 to 300 sec N T
Absolute Capacity 100 Tons 0 to 9999 Tons D T

Timers

Start-Start 40 min 15 to 60 min N M
Stop-Start 3 min 3 to 20 min N M
Source No Start

0.5 °F/min 0.1 to 5.0 °F/min

0.1 °F/min 0.0 to 5.0 °F/min

Normal, Efficiency,

Pump, Standby

1,2, … (# of

Compressors)

70 °F 50 to 100 °F

D M
D M

N M
N M

D T

Continued next page.

Manual

Reference

24 OMM WMC-3 OITS

Description Default Range Type PW

Alarms

Evaporator Freeze
Condenser Freeze
Low Evap Pressure 26 psi 10 to 45 psi D T
Low Evap Pressure-Inhibit 38 psi 20 to 45 psi D T
Low Evap Pressure-Unload 31 psi 20 to 45 psi D T
High Discharge Temperature-Shutdown
High Discharge Temperature-Load
High Condenser Pressure 140 psi 120 to 240 psi D T
Motor Current Threshold 10% 1 to 20% N T
Surge High Suction SH - Start
Surge High Suction SH - Run

Service

Vane Mode AUTO AUTO, MANUAL N T
Unload Timer 10 sec 10 to 240 sec N T
STOP Timer 1 sec 1 to 240 sec N T

34.0 °F -9.0 to 45.0 °F

34.0 °F -9.0 to 45.0 °F

190 °F 120 to 240 °F
170 °F 120 to 240 °F

50 °F 25 to 90 °F
25 °F 5 to 45 °F

D T
D T

N T
N T

N T
N T

Manual

Reference

These setpoints are normally viewed or changed on the OITS, but can be changed on the unit
controller if the OITS is not available.

Compressor Faults, Problems, Warnings

Faults (Equipment Protection Shutdowns)

Equipment protection faults cause rapid compressor shutdown. The compressor is stopped
immediately (if the compressor was running).

The following table identifies each alarm, gives the condition that causes the alarm to occur, and
states the action taken because of the alarm. All equipment protection alarms require a manual
reset.

Table 14, Compressor Controller Faults (Equipment Protection Shutdowns)

Description Occurs When: Action Taken

Low Evaporator Pressure Evaporator Press < Low Evap Pressure SP Rapid Stop
High Condenser Pressure Cond Press > High Condenser Pressure SP Rapid Stop
Low Motor Current I < Motor Current Threshold with Compressor ON for 30 sec Rapid Stop
High Discharge Temperature Temp > High Discharge Temperature SP Rapid Stop
Mechanical High Pressure Digital Input = High Pressure Rapid Stop
High Motor Temperature Digital Input = High Temperature Rapid Stop

Surge High Suct SH-Starting
Surge High Suct SH-Running
No Compressor Stop
Starter Fault

Leaving Evaporator Water
Temperature Sensor Fault

Evaporator Pressure Sensor Fault Sensor shorted or open Rapid Stop
Condenser Pressure Sensor Fault Sensor shorted or open Rapid Stop
Suction Temperature Sensor Fault Sensor shorted or open Rapid Stop

Discharge Temperature Sensor
Fault

Evaporator Water Flow Loss Evaporator Flow DI = No Flow for > 10 sec Rapid Stop
Condenser Water Flow Loss Condenser Flow DI = No Flow for > 10 sec Rapid Stop

Temp > Surge High Suct SH-Start SP during first 5 minutes

of Compressor ON

Temp > Surge High Suct SH-Run SP after first 5 minutes of

Compressor ON

%RLA > Motor Current Threshold SP with Compressor OFF

for 30 sec

Starter Fault Digital Input = Fault AND Compressor State =

START, INTLOK, RUN, or UNLOAD

Sensor shorted or open Rapid Stop

Sensor shorted or open Rapid Stop

Rapid Stop
Rapid Stop

Annunciation

Rapid Stop

OMM WMC-3 OITS 25

Compressor Controller Events (Limit Alarms)

The following alarms do not cause compressor shutdown but limit operation of the chiller in some
way, as described in the Action Taken column.

Table 15, Compressor Controller Events

Description Occurs When: Action Taken Automatic Reset

Low Evaporator Pressure
– Inhibit Loading
Low Evaporator Pressure
– Unload
Evaporator Freeze
Protect
Condenser Freeze
Protect

High Discharge
Temperature

Pressure < Low Evap Pressure–Inhibit

setpoint

Pressure < Low Evap Pressure–Unload

setpoint

Evap Sat Refr Temp < Evaporator Freeze

setpoint

Cond Sat Refr Temp < Condenser Freeze

Setpoint

Temperature > High Discharge

Temperature-Load SP AND

Suction superheat < 15°F

Inhibit loading

Unload

Start evaporator

pump

Start condenser

pump

Load

Evap Press rises above

(SP + 3psi)

Evap Press rises above

(SP + 3psi)

Temp > (Evaporator Freeze

SP + 2°F)

Temp > (Condenser Freeze

SP + 2°F)

Temp < (High Dsch Temp

Load SP – 3°F) OR

Superheat > 18°F

Warnings

Warnings advise that a non-catastrophic problem exists, such as failed temperature sensor that
provides a signal for information, not control purposes. There are no Warnings associated with the
compressor controllers.

Compressor Controller Functions

Each compressor determines if it is at its maximum capacity (or maximum allowed capacity) and if
so, set its Full Load flag. The flag is based on a number of conditions.

Absolute Capacity

Each compressor estimates its absolute capacity from the present value of %RLA and the Absolute
Capacity setpoint from the equation:

Absolute Capacity = (%RLA Factor) * (Absolute Capacity setpoint)
where the %RLA Factor is interpolated from the following table.

%RLA 0 50 75 100 150
%RLA Factor 0 0.35 0.75 1.00 1.50

Multiple Compressor Staging

This section defines which compressor is the next one to start or stop. The next section defines
when the start, or stop, is to occur.

Functions

1. Can start/stop compressors according to an operator defined sequence.

2. Can start compressors based on the number of starts (run hours if starts are equal) and stop on
run hours

3. 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.

4. An “efficiency priority” mode can be selected for two or more chillers where one compressor is
started on each chiller in the group before a second is started on any of them.

26 OMM WMC-3 OITS

5. A “pump priority” mode can be selected for one or more chillers where all compressors on a
given chiller are started before going to the next chiller in the group.

6. One or more compressor can be defined as “standby” where it is never used unless one of the
normal compressors is unavailable.

Required Parameters

1. Sequence number setpoint (SQ#_SP) for all compressors. Possible settings = (1-4).

2. Compressor Staging Mode setpoint (CSM_SP) for all compressors. Possible settings are:
NORMAL,
EFFICIENCY PRIORITY,
PUMP PRIORITY,
STANDBY

3. Maximum Number of compressors ON setpoint (MAX_ON_SP). Possible settings = (1-4).
This setpoint is the same for all compressors.

4. Number of starts for all compressors.

5. Number of run hours for all compressors.

6. Status of all compressors (On-line, Available/Unavailable, Starting, Running, etc.).

Configuration Rules

1. Each standby compressor must have a sequence number greater than or equal to all non­standby compressors for which it is in standby.

2. All compressors in an “efficiency priority” or “pump priority” group must be set to the same
sequence number.

OMM WMC-3 OITS 27

m

p

Compressor State Control (Comp State)

Operation of the compressor is controlled by the state-transition diagram shown below. A state
variable (Comp State) shall be used to maintain the current state (OFF, START, INTLOK, RUN,
UNLOAD, or STOP). Transitions from one state to another are controlled by the condition
statements in the

Figure 7,Compressor State

TEST: Motor Current < Motor Current Threshold SP

& STOP Timer Ex

TEST boxes. TASK boxes indicate actions that must be performed.

TEST:

& Evap State=RUN & Next On = Yes &

ired

Power ON

OFF

Unit State=AUTO
Stage Up Now = YES & (Unit Mode NOT= HEAT OR
EvLWT Temperature > Source No Start SP) &

Start-Start Timer Expired & Stop-Start Timer Expired &

No Safety Alarms

TASK: Restart Start-Start Timer

VaneCloseDelay

TEST: Manual OFF DI = OFF OR

Vanes Closed

TASK: Start STOP Timer

Start Stop-Start Timer & Update Run Hours

OR Unit State = OFF

OR Unload Timer Expired OR Safety Alar

UNLOAD

TEST: Unit State = SHUTDOWN OR

[Next Off = Yes

& Stage Down Now = Yes

TASK: Start Unload Timer

Compressor Capacity Control

TEST: Manual OFF DI = OFF OR

Unit State = (OFF

TEST: Manual OFF DI = OFF

OR Unit State = OFF

TEST: Unit State = AUTO

& Next Off = No

OR SHUTDOWN)

OR Safety Alarm

TEST: Unit State= AUTO & Evap State=RUN &

RUN

START

TASK: Start Interlok Timer (10sec)

InterLock

Cond State = RUN & Vanes Closed &

InterLok Timer Expired

TASK: Increment # of starts

Leaving Water Control Mode

Compressor capacity is determined by the status of the leaving chilled water temperature (LWT),
which is a direct indicator of whether the chiller is producing enough cooling to satisfy the cooling
load. The LWT is compared to the active chilled water setpoint and compressor loading or
unloading ensues, considering any capacity overrides that may be in effect.

Capacity Overrides

The conditions described in the following subparagraphs override normal capacity control when
the chiller is in the COOL mode. These overrides are not in effect for loading and unloading when
the Vane Mode is set to MANUAL. Of the following limits, the one creating the lowest amp limit
is in effect. The resulting present limit value for compressor current is stored in the Active Demand
Limit variable.

28 OMM WMC-3 OITS

Low Evaporator Pressure

If the evaporator pressure drops below the Low Evaporator Pressure – Inhibit setpoint, the unit will
inhibit capacity increase. If the evaporator pressure drops below the Low Evaporator Pressure ­Unload setpoint, the unit will begin capacity decrease.

High Discharge Temperature - Load

If the discharge temperature rises above the High Discharge Temperature - Load setpoint and the
motor current is < 50% RLA, the unit will begin capacity increase.

Soft Load

Soft Loading is a configurable function used at compressor startup to limit the maximum current
draw on the compressor in a ramp-up type manner. It is only active on the first compressor to start.
The setpoints that control this function are:

• Soft Load – (ON/OFF)

• Begin Amp Limit – (%RLA)

• Maximum Amps – (%RLA)

• Soft Load Ramp – (seconds)

The active soft load limit value (in %RLA) increases linearly from the Begin Amp Limit setpoint to
the Maximum Amps setpoint over the amount of time specified by the Soft Load Ramp setpoint. If
the amp draw rises above the currently active soft load limit value, the unit will inhibit capacity
increases. If the amp draw rises to 5% or more above this value, the unit will begin capacity
decrease.

Maximum LWT Rate

The maximum rate at which the leaving water temperature can drop (chiller mode = COOL) is
limited at all times by the Maximum Rate setpoint. If the rate exceeds this setpoint, capacity
increases is inhibited.

Demand Limit

The maximum amp draw of the compressor can be limited by a 4 to 20 mA signal on the Demand
Limit analog input. This function is only enabled if the Demand Limit setpoint is set to ON. The
amp limit decreases linearly from the Maximum Amp Limit setpoint (at 4 mA) to the Minimum
Amp Limit setpoint (at 20mA). If the amp draw rises above the limit value, the unit will inhibit
capacity increases. If the amp draw rises to 5% or more above this value, the unit will begin
capacity decrease.

Network Limit

The maximum amp draw of the compressor can be limited by a value sent through a BAS network
connection and stored in the Network Limit variable. If the amp draw rises above the limit value,
the unit will inhibit capacity increases. If the amp draw rises to 5% or more above this value, the
unit will begin capacity decrease.

Minimum Amp Limit

The minimum amp draw of the compressor can be limited by the Minimum Amps setpoint. If the
amp draw drops below the limit value, the unit will inhibit capacity decrease.

Maximum Amp Limit

The maximum amp draw of the compressor is always limited by the Maximum Amps setpoint.
This limit has priority over all other functions including manual capacity control. If the amp draw
rises above the limit value, the unit will inhibit capacity increases. If the amp draw rises to 5% or
more above this value, the unit will begin capacity decrease.

OMM WMC-3 OITS 29

Compressor On-Board Controllers

Each compressor is equipped with microprocessor controllers and sensors that provide control and
data acquisition. The data is transmitted to other controllers and the OITS via the pLAN. The on­board controllers consist of:

• Compressor Controller; the compressor controller is the central processor of the compressor. It

is continually updated with critical data from the motor/bearing controller and external sensors.
An important function is to control the compressor speed and guide vanes operation in order to
satisfy load requirements, to avoid surge and to provide for optimum efficiency. The controller
monitors over 60 parameters, including:

Refrigerant pressures and temperatures Line voltage
Phase failure detection Motor temperature
Silicone Rectifier (SCR) temperature Speed
Line currents Guide vane position

• Soft-Start Controller; the soft-start controller limits current inrush by temporarily inserting a

charging resistor between the ac line and the +DC bus. It works in conjunction with the
variable-speed function.

• Motor/Bearing Controller; the motor/bearing system provides the measurements and control to

calculate and maintain the desired shaft position. An RS-485 link connects the bearing
controller and the compressor controller.

• Backplane; although not a controller, the backplane connects the on-board control modules

with the soft-start controller, power electronics, motor cooling solenoids and
pressure/temperature sensors.

Figure 8, Compressor Electric/Electronic Components

1. Rectifiers

2. Main Power Block

3. Soft Start Controller

4. Insulated-gate
Bipolar Transistor

I.G.B.T Inverter

5. High Voltage DC-DC
Converter

6. Compressor, Bearing/Motor
Controllers

7. Interstage pressure /

temperature sensor

8. Suction Pressure /

temperature sensor

4

5

6

3

7

8

2

1

30 OMM WMC-3 OITS

A

CROTECH CO

A

A

A

Figure 9, Field Wiring Diagram

MI

BOX TERMINALS

(115V) (24V)

UTB1

NOTE 3

PE
85

86

80

74
86
86

79

73

78

77

76

75

81
82(NO)
83(NC)

84

* COOLING

TOWER

FOURTH

STAGE

STARTER

* COOLING

TOWER
THIRD
STAGE

STARTER

* COOLING

TOWER

SECOND

STAGE

STARTER

* COOLING

TOWER
FIRST
STAGE

STARTER

GND

POWER

*

NOTE 6
NEUTRAL

NOTE 9

*

H

O

C4

A

NOTE 9

*

H

O

C3

A

*

NOTE 9

H

O

C2

A

NOTE 9

*

H

O

C1

A

COMMON

*

POWER

70
55

CF1

EF1
EF2

CF2

54

NTROL

A

(NOTE 5)
SWITCH
DELTA P
FLOW OR
EVAP.

*ALARM RELAY

(NOTE 3)

*

MODE SWITCH

(NOTE 5)
SWITCH
DELTA P
FLOW OR
COND.

* REMOTE
ON/OFF
(NOTE 4)

*

NOTE 7

EP2

NOTE 10

*

NOTE 7

EP1

NOTE 10

O

O

EWI-1

*

NOTE 8

NOTE 10

H

EWI-2

H

CP2

C

* CHILLED
WATER
PUMP

STARTERS

C

H

O

C

CWI-2

* CONDENSER
WATER
PUMP
STARTERS

*COOLING TOWER BYPASS VALUE

*COOLING TOWER VFD

0-10 VDC

0-10 VDC

52

71

71

53

NOTE 8

*

NOTE 10

CP1

H

O

CWI-1

C

330617801 REV. 00

1. Compressor terminal boxes are factory-mounted and wired. All line-side wiring must be in accordance with the NEC and be made
with copper wire and copper lugs only. Power wiring between the terminal box and compressor terminals is factory installed.

2. Minimum wire size for 115 VAC is 12 ga. for a maximum length of 50 feet. If greater than 50 feet refer to McQuay for
recommended wire size minimum. Wire size for 24 VAC is 18 ga. All wiring to be installed as NEC Class 1 wiring system. All
24 VAC wiring must be run in separate conduit from 115 VAC wiring. Wiring must be wired in accordance with NEC and
connection to be made with copper wire and copper lugs only.

3. A customer furnished 24 or 120 Vac power for alarm relay coil may be connected between UTB1 terminals 84 power and 81
neutral of the control panel. For normally open contacts wire between 82 & 81. For normally closed wire between 83 & 81.
Maximum rating of the alarm relay coil is 25VA.

4. Remote on/off control of unit can be accomplished by installing a set of dry contacts between terminals 70 and 54.

5. If field supplied pressure differential switches are used, they must be installed across the vessel and not the pump. They must be
suitable for 24vac and low current application

6. Customer supplied 115 VAC 20 amp pow er for optional evaporator and condenser water pump control power and tower fans is
supplied to unit control terminals (UTB1) 85 power / 86 neutral, PE equipment ground.

7. Optional customer supplied 115 VAC, 25 VA maximum coil rated, chilled water pump relay (ep1 & 2) may be wired as shown.
This option will cycle the chilled water pump in response to chiller demand.

8. The condenser water pump must cycle w ith the unit. A customer supplied 115 VAC 25 VA maximum coil rated, condenser water
pump relay (CP1 & 2) is to be wired as shown. Units with free-cooling must have condenser water above 60°F before starting.

9. Optional customer supplied 115 VAC 25 VA maximum coil rated cooling tower fan relays (C1 - C2 standard, C3-C4 optional) may
be wired as shown. This option will cycle the cooling tower fans in order to maintain unit head pressure.

10. Auxiliary 24 VAC rated contacts in both the chilled water and condenser water pump starters should be wired as shown.

11. Voltage unbalance not to exceed 2% with a resultant current unbalance of 6 to 10 times the voltage unbalance per NEMA MG-1,
1998 Standard

OMM WMC-3 OITS 31

Interface Touch Screen

Navigation

The home screen shown in VIEW screen on page 34 is usually left on (there is a screen-saver built
in that is reactivated by touching the screen anywhere). This VIEW screen contains the STOP and
AUTO buttons used to start and stop the unit when in Local control. Other groups of screens can
be accessed from the Home screen by pressing one of three buttons on the bottom of the screen;
HISTOR Y, VIEW , SET.

• HISTORY will go to the last history screens viewed and can toggle between the two history

screens.

• Trend History

• Alarm History

• VIEW will go to the home View screen. Pressing again will go to the detail View screen used

to look in detail at settings and the operation of the chiller. Pressing VIEW from any other
screen will return to the last displayed View screen. A new button called MENU will appear
when in the View mode. See page

• SET will go to the last Set screen used.

37 for details.

Figure 10on the following page illustrates the arrangement of the various screens available on the
OITS. A few minutes practice on an actual OITS should provide an acceptable level of confidence
in navigating through the screens.

32 OMM WMC-3 OITS

A

A

Figure 10, OTIS Screen Layout

SET SCREENS

HOME

SCREEN

SET

PRESS VIEW

SETPOINTS

EACH GROUP OF

SETPOINTS HAVE

SETTING AND RANGE

EXPLAINED ON SCREEN

PRESS SET

SEE FIGURE 22

POWER

TIMERS

LARMS

VALVE (TOWER)

TOWER (FANS)

MOTOR

MODES

WATER

HISTORY

HOME

SCREEN

HISTORY

TREND

HISTORY

OR

LARM

PRESS HISTORYPRESS VIEW

VIEW SCREENS

HOME

SCREEN

VIEW

PRESS VIEW

SCREEN

PRESS MENU

MENU

LABELS
ON/OFF

BAR GRAPHS

SCHEMATIC

PRESS VIEW

VIEW

PRESS VIEW

Pressing VIEW from any sub-menu will toggle back to the home
Pressing MENU when in any sub-menu will return to the view
Pressing SET or HISTORY will go to these groups of

SEE FIGURE 13

SEE FIGURE 14

SEE FIGURE 17

COMPRESSOR STATE

COMPRESSOR I/O

UNIT I/O

EVAPORATOR

CONDENSER

SEE FIGURE 20

SEE FIGURE 18

SEE FIGURE 19

OMM WMC-3 OITS 33

Screen Descriptions

Figure 11, Home View Screen

VIEW Screens

View screens are used for looking at unit status and conditions.

Home View Screen

The Home View Screen shows the basic operating condition of the chiller and is the screen that is
normally left on. Superimposed on a chiller schematic drawing is:

Alarm

A red “ALARM” light will appear to the right of the “SET” button should an alarm occur. Pressing
it will bring up the active alarm screen to view the alarm details.

Information

• Chilled water setpoint (ACTIVE LWT SETPOINT)

• Entering and leaving chilled water temperatures

• Entering and leaving condenser water temperatures

• Percent motor amps

• UNIT STATUS is MODE followed by STATE followed by the SOURCE that is the device or

signal that created the STATE. The possible combinations are in the following table:

Table 16, UNIT STATUS Combinations

MODES STATES SOURCES

COOL OFF Manual Switch
SHUTDOWN (Note 1) Remote Switch
AUTO Local
BAS Network

Note 1: Shutdown is the state of shutting down; vane close, etc

34 OMM WMC-3 OITS

• COMPRESSOR STATUS is MODE followed by STATE followed by the SOURCE that is the

device or signal that created the STATE. The possible combinations are in the following table

Table 17, COMPRESSOR STATUS Possibilities

Complete STATUS Text

(in priority sequence)

OFF Manual Switch
OFF Compressor Alarm
OFF Unit State
OFF Evap Flow/Re-circulate
OFF Start to Start Timer=xxx
OFF Stop to Start Timer=xxx
OFF Staging (Next ON)
OFF Awaiting Load
RUN Unload Vanes-Max Amps
RUN Hold Vanes-Max Amps
RUN Manual Vanes & Speed
RUN Load Vanes-Manual Speed
RUN Hold Vanes-Manual Speed
RUN Unload Vanes-Manual Speed
RUN Load Speed-Manual Vanes
RUN Hold Speed-Manual Vanes
RUN Unload Speed-Manual Vanes
RUN Unload Vanes-Lag Start
RUN Hold Vanes-Evap Press
RUN Unload Vanes-Evap Press
RUN Unload Vanes-Soft Load
RUN Hold Vanes-Soft Load
RUN Load Vanes-Disch Temp
RUN Hold Vanes-Pull-down Rate
RUN Unload Vanes-Demand Limit
RUN Hold Vanes-Min Amps
RUN Load Vanes
RUN Hold Vanes
RUN Unload Vanes
SHUTDOWN Unload Unloading during the shutdown sequence

Used for service purposes. "T" password required. Operated

Reason for the compressor being off.

Overrides water temperature command

from compressor controller

Overrides water temperature command

Notes

Normal operation

NOTES:

1. Timer countdown values will be shown where “(xxx)” is shown below.

2. “Vanes” or “Speed” is shown in the RUN state to indicate if the capacity is controlled by speed from the VFD or

by vane control.

Action Buttons for:

Chiller Control: normal start (AUTO button) and STOP button. The STOP button activates the

•

normal shutdown sequence. These buttons are only active when the when control is in the
"Local Control" mode. This eliminates the possibility of inadvertently shutting off the unit
locally when it is under control of a remote signal such as a BAS.

• HISTORY, toggles between the Trend History screen and the Alarm History screen.

• SET, toggles between the Setpoints screen that are used for changing setpoints and the Service

screen.

Returning

Pressing the VIEW button from any screen will return to this screen

OMM WMC-3 OITS 35

Figure 12, Detail View Screen

Data for one compressor is shown at a time on this screen. Pressing the COMPRESSOR button in the
screen lower-left hand corner will toggle between #1 and #2 compressor.

Pressing the VIEW button on the bottom of the Home View screen accesses the Detail View Screen
shown above. This screen gives additional information on the refrigerant pressures and temperatures.

Pressing the STATE button will bring up a display of the compressor state as described on page
Pressing the I/O button displays the status of the compressor inputs and outputs as described in

37.
Figure 15

on the same page. WMC units will have a COMP button that will toggle between the two compressors'
data, allowing the STATE and I/O detail screens to be viewed for either compressor.

Pressing the UNIT I/O button displays the unit inputs and outputs as described in

Figure 16 on page 38.

Pressing the EVAP or COND button will give detailed information on the evaporator or condenser
pressures and temperatures.

Pressing the ACTIVE LWT SETPOINT button will show a window from which the leaving water
setpoints can be changed. However, it is recommended that the SETPOINT screens described later be
used for this purpose.

Pressing the MENU button on the bottom of the screen will go to a menu (see

Figure 13) from which the

above listed screens can also be accessed.
This screen will be superimposed on the right side of the VIEW screen. This screen will remain

visible until another display button; such as STATE, I/O, etc. is pressed.

36 OMM WMC-3 OITS

Figure 13, View Menu

This View Menu is accessed by pressing the MENU button from the Detail View Screen. The menu screen
accesses several informational screens as shown in the above figure.

Figure 14, View Compressor State Screen

For example, pressing the Compressor-State button on the Menu screen in
Figure 13 will display the screen shown in Figure 14 on the right side of
both the Menu screen and the Detail View screen. The Compressor State
screen is basically a compilation of the events that the chiller sequences
through at startup. A green light (light gray in the figure) indicates that a
particular sequence requirement has been satisfied. It is recommended that
this screen be viewed during the start up sequence. One can see the
requirements light up as they are met and quickly see why a non-start may
have occurred. For example, The Evap Flow OK will light when the
evaporator flow switch is closed by flow.

The bottom sections (from "RUN" down) are in effect during the shut
down process. The sequence transitions back to OFF at this point and the
OFF light will be illuminated.

OMM WMC-3 OITS 37

Figure 15, View Compressor Input/Output Status

Pressing the I/O button adjacent to the compressor on the VIEW-MENU screen
will access the screen shown in
of the Detail View Screen. It gives the status of the
and outputs. Many of these I/Os also appear in the Compressor State screen
since they are part of the start up sequence and define the compressor state at
any given time. WMC units will have two of any compressor screen.

A COMP button will appear in the lower left-hand corner of the Detail View
Screen. This button will toggle compressor data from #1 compressor to #2
compressor .

.

Figure 16, Unit Input/Output Screen

Figure 15. It is superimposed on the right side

compressor digital inputs

The screen shown in

Figure 16 to the left gives the status of the unit controller
digital inputs and outputs and analog outputs. The unit controller in concerned
with the operation of the entire unit and its I/Os reflect this. Note that
operation of condenser and evaporator water pumps and tower operation
constitute most of the data flow. An illuminated block (gray in the figure)
indicated that either an input or output signal exists

Pressing the Evaporator or Condenser buttons on Detail View Screen will
display pertinent vessel temperatures and pressures. The screens are very
simple, self-explanatory, and not shown here.

38 OMM WMC-3 OITS

Figure 17, Labeled Bar Graphs

The bar chart screen is accessed from the MENU screen (
for the graphs with labels attached as shown above or select Bar Graphs for charts without labels.

Pressing “COMP” on the lower left corner of the screen will toggle between the unit’s two
compressors. Pressing “MENU”, HISTORY”, “VIEW”, or “SET”buttons will forward to those
respective screens.

Figure 13) by selecting Labeled Bar Graphs

SET Screens

The set screens on the Interface Panel are used to input the many setpoints associated with equipment
of this type. MicroTech II provides an extremely simple method for accomplishing this. (NOTE: If
the Interface Panel is unavailable, the unit controller can be used to change setpoints.) Appropriate
setpoints are factory set and checked by McQuayService or Factory Authorized Service Company
during commissioning. However, adjustments and changes are often required to meet job conditions.
Certain settings involving pumps and tower operation are field set.

Pressing the SET button found on almost every screen accesses the last SET screen used or the
SERVICE screen, whichever of the two was used last.

When in any SET screen, pressing the SET button again will toggle to the SERVICE screen shown on
page

52.

OMM WMC-3 OITS 39

t

Unit Status

N

Compressor

Status

Setpoint

Description

Range of

Settings

umeric

Keypad

Figure 18, A Typical SETPOINT Screen

Action

Buttons

Setpoints

Setpoint

Selection

Buttons

Initiate

Change

Button

Setpoin

Groups

The above figure shows the Water screen with Leaving Water Temp setpoint selected. The various
setpoint groups are in a column on the right side of the screen. Each button contains a number of
setpoints grouped together by similar content. The WATER button (as shown) contains various
setpoints relating to water temperature setpoints.

NOTE: Some setpoints that do not apply to a particular unit application may still be listed on the

screen. They will be inactive and can be ignored.
The numbered buttons in the second from right column are pressed to select a particular setpoint. The

selected setpoint will appear in blue on the screen and a description of it (with the range of available
settings) will appear in the upper left-hand box.

Procedure for Changing a Setpoint

A list of setpoints, their default value, their available setting range, and password authority are in
Table 6 on page 20 for the unit and Table 13 on page 24 for the compressor.

1. Press the applicable Setpoint Group). (A complete explanation of setpoint content of each
group follows this section.)

2. Select the desired setpoint by pressing the numbered button.

40 OMM WMC-3 OITS

3. Press the CHANGE button indicating that you wish to change a setpoint value. The
KEYBOARD screen will be turned on automatically to facilitate entering the password.

• O = Operator level password is 100

• M = Manager level password is 2001

• T = Technician level password

4. Press the appropriate numbers in the numeric keyboard to enter the password. There is a small
delay between pressing the keypad and recording the entry. Be sure that an asterisk appears in
the window before pressing the next number. Press ENTER to return to the SETPOINT
screen. The password will remain open for 15 minutes after initiation and does not need to be
re-entered.

5. Press CHANGE again. The right side of the screen will turn blue (inactive).

6. The numeric keypad and action buttons in the lower left-hand corner of the screen will be
activated (the background will turn green). Setpoints with numeric values can be changed in
two ways:

• Select the desired value by pressing the numbered buttons. Press ENTER to enter the value or

CANCEL to cancel the transaction.

• Press the UP or DOWN button to increase or decrease the value displayed. Press ENTER to

enter the value or CANCEL to cancel the transaction.
Some setpoints are text rather than numeric values. For example, LWT Reset Type can be

"None" or "4-20 ma". The selection can be made by toggling between choices using the UP or
Down button. If dashed lines appear in the setpoint window, it indicates that you have toggled
too far and need to reverse direction. Press ENTER to enter the choice or CANCEL to cancel
the transaction.

Once CHANGE is selected, the CANCEL or ENTER buttons must be pressed before another
setpoint can be selected.

7. Additional setpoints can be changed by selecting another setpoint on the screen or by selecting
an entirely new group of setpoints.

Explanation of Setpoints

Each of the seven setpoint group of screens are detailed in the following section. In many cases the
setpoint content is obvious and no explanation is included.

1. TIMERS, for setting timers such as start-to-start, etc.

2. ALARMS, for setting the limit and shutdown alarms.

3. VALVE, sets the parameters for operation of an optional field-installed tower bypass valve.

4. TOWER, selects the method of controlling the cooling tower and sets the parameters for fan
staging/VFD.

5. MOTOR, selects motor related setpoints such as amp limits. Also has maximum and minimum
rate of change of chilled water temperature.

6. MODES, selects various modes of operation such as control source, multiple compressor
staging, pump staging, BAS protocol, etc.

7. WATER, leaving water temperature setpoint, start and stop delta-T, resets, etc.

OMM WMC-3 OITS 41

TIMERS Setpoint

Figure 19, TIMERS Setpoint Screen

Table 18, TIMER Setpoints

Description No. Default Range

Full Load Timer 5 300 sec
Interlock Timer 4 10 sec
Stop-Start Timer 3 3 min 3 to 20 min M
Start-Start Timer 2 40 min

Evap Recirculate
Timer

1 30 sec 0.2 to 5 min M

0 to 999

sec.

10 to 240

seconds

15 to 60

min

Pass-

word

Comments

Time compressor must load (without unloading) before

M

vanes are considered fully open.
Maximum time allowed before interlock confirmation

M

from compressor
Time from when compressor stops to when it can
restart
Time from when compressor starts to when it can start

M

again
Time that evaporator pump must run before
compressor start

42 OMM WMC-3 OITS

ALARMS Setpoint

Figure 20, ALARMS Setpoint Screen

Table 19, ALARM Setpoints

Description No. Default Range

Condenser Freeze 11
Evaporator Freeze 10
Motor Current Threshold 9 10% 1 to 20% T Min %RLA to consider that the is motor off

Surge Slope Limit 8

Surge Temperature Limit 7
High Discharge Temp-Stop 6
High Discharge Temp-Load 5

High Condenser Pressure 4 140 psi 120 to 240 psi T Max discharge pressure, stop compressor
Low Evap Pressure, Stop 3 26 psi 10 to 45 psi T Min evap pressure – stop compressor
Low Evap Pressure-Unload 2 31 psi 20 to 45 psi T Min evap pressure – unload compressor
Low Evap Pressure-Inhibit 1 33 psi 20 to 45 psi T Min evap pressure – inhibit loading

34.0 °F -9.0 to 45.0 °F

34.0 °F -9.0 to 45.0 °F

20 deg

F/min

50 °F 2 to 45 °F
190 °F 120 to 240 °F
170 °F 120 to 240 °F

1 to 99

deg F/min

Pass-

word

T Minimum cond. sat. temp. to start pump
T Minimum evap. sat. temp. to start pump

Surge temperature (ST) slope value above

T

which alarm occurs. Active only if ST>SP7
at start

At start, Surge Temp (ST) is compared to

T

this SP. Alarm at ST>2x SP.
Max discharge temp to shut down

T

compressor
Sets discharge temp above which a forced

T

capacity increase occurs.

Comments

OMM WMC-3 OITS 43

Cooling Tower Bypass VALVE Settings

Figure 21, Tower Bypass VALVE Setpoint Screen

Table 20, Tower Bypass VALVE Setpoints (See page

Description No. Default Range

Slope Gain 15 65 10 to 99 M Control gain for temperature (or lift) slope
Error Gain 14 55 10 to 99 M Control gain for temperature (or lift) error

Valve Control Range(Max) 13 45% 0 to 100% M
Valve Control Range (Min) 12 35% 0 to 100% M Minimum valve position, overrides all other settings

Temp - Maximum Start
Position

Maximum Start Position 10 80% 0 to 100% M
Temp - Minimum Position 9
Minimum Start Position 8 10% 0 to 100% M

Stage Down @ 7 20% 0 to 100% M

Stage Up @ 6 80% 0 to 100% M

Valve Deadband (Lift) 5 4.0 psi
Valve Deadband (Temp) 4
Valve Target (Lift) 3 30 psi
Valve Setpoint (Temp) 2
Valve Type 1

11

85 °F 0 to 100 °F

75 °F 0 to 100 °F

2.0 °F

65 °F

NC (To
Tower)

1.0 to 20.0
psi

1.0 to 10.0

°F

10 to 130

psi

40 to 120

°F

NC, NO M

Pass-

word

M

M

M Control deadband, Tower - Setpoint #1=Lift
M Control deadband, Tower Setpoint #1=Temp
M
M

46 for complete explanation.)

Comments

Maximum valve position, overrides all other
settings

Condenser EWT at which valve should be open to
tower. Valve position is set to SP8

Initial valve position when condenser EWT is at or
above Setpoint # 9

Condenser EWT at which initial valve position is
set to Setpoint # 6

Initial position of valve when condenser EWT is at
or below Setpoint # 7
Valve position below which the fans can stage
down (Tower - Setpoint #2 = Valve Stage Down
VFD speed below which the next fan speed can
turn off (Tower - Setpoint # 2 = valve/VFD
Valve position above which the fans can stage up
(Tower - Setpoint #2 = Valve Stage Down
VFD speed above which the next fan speed can
turn on (Tower - Setpoint # 2 = valve/VFD

Target for lift pressure (Tower - Setpoint #1= Lift),
Works with Setpoint # 5
Target for condenser EWT (Tower Setpoint #1=
Temp), Works with Setpoint # 4
Normally closed (NC) or normal open (NO)
to tower

44 OMM WMC-3 OITS

Cooling TOWER Fan Settings

Figure 22, Cooling TOWER Fan Setpoint Screen (See page 46 for complete explanation.)

Table 21, Tower Fan Settings

Description No. Default Range

Stage #4 On (Lift) 15 35 psi 10 to 130 psi M Lift pressure for fan stage #1 on
Stage #3 On (Lift) 14 45 psi 10 to 130 psi M Lift pressure for fan stage #2 on
Stage #2 On (Lift) 13 55 psi 10 to 130 psi M Lift pressure for fan stage #3 on
Stage #1 On (Lift) 12 65 psi 10 to 130 psi M Lift pressure for fan stage #4 on
Stage #4 On (Temp) 11
Stage #3 On (Temp) 10
Stage #2 On (Temp) 9
Stage #1 On (Temp) 8
Stage Differential (Lift) 7 6.0 psi 1.0 to 20.0 psi M Fan staging deadband with Setpoint # 1=Lift

Stage Differential
(Temp)

Stage Down Time 5 5 min 1 to 60 min M
Stage Up Time 4 2 min 1 to 60 min M

Tower Stages 3 2 1 to 4 M Number of fan stages used

Valve/VFD Control 2 None

Tower Control 1 None

70 °F 40 to 120 °F
75 °F 40 to 120 °F
80 °F 40 to 120 °F
85 °F 40 to 120 °F

6

3.0 °F 1.0 to 10.0 °F

None, Valve

Setpoint, Valve

Stage, VFD

Stage, Valve

SP/VFD Stage

None,

Temperature,

Lift

Pass-

word

M Temperature for fan stage #1 on
M Temperature for fan stage #2 on
M Temperature for fan stage #3 on
M Temperature for fan stage #4 on

M Fan staging deadband with Setpoint #1=Temp

Time delay between stage up/down event and
next stage down
Time delay between stage up/down event and
next stage up

None: No tower valve or VFD
Valve Setpoint: Valve controls to VALVE SP3(4)
& 5(6)
Valve Stage: Valve control setpoint changes to

M

fan stage setpoint
VFD Stage: 1
Valve Setpoint/VFD Stage: Both valve and VFD
None: No tower fan control

M

Temperature: Fan and valve controlled by EWT
Lift: Fan and valve controlled by lift pressure

Comments

st

fan is VFD controlled, no valve

OMM WMC-3 OITS 45

Explanation of Tower Control Settings

The MicroTech II controller can control cooling tower fan stages, a tower bypass valve, and/or a
tower fan VFD if the chiller has a dedicated cooling tower.

The Tower By pass Valve position will always control the Tower Fan Staging if Valve Setpoint or
Stage Setpoint is selected.

There are five possible tower control strategies as noted below and explained in detail later in this
section. They are selected from SETPOINT TOWER SP2.

1. NONE

, Tower fan staging only , which is not recommended. In this mode the tower fan staging
(up to 4 stages) is controlled by either the condenser Entering Water Temperature (EWT) or
LIFT pressure (difference between the condenser and evaporator pressure). Tower bypass or
fan speed are not controlled.

2. VALVE SP

, Tower staging with low-limit controlled bypass valve. In this mode the tower fans
are controlled as in #1, plus a tower bypass valve is controlled to provide a minimum
condenser EWT. There is no interconnection between the fan control and the valve control.

3. VALVE STAGE

, Tower staging with stage controlled bypass valve. In this mode the

bypass valve controls between fan stages to smooth the control and reduce fan cycling

4. VFD STAGE.

In this mode a VFD controls the first fan. Up to 3 more fans are staged on and

off and there is no bypass valve.

5. VALVE/VFD

, Tower fan control with VFD plus bypass valve control.

1. Tower Fan Staging Only (NONE), This is not a recommended control strategy,

The following settings are used for the Tower Fan Staging Only mode, (SP= setpoint)

1) TOWER SETPOINT Screen
a) SP1. Select TEMP if control is based on condenser EWT or LIFT if based on compressor lift

expressed in degrees.

b) SP2. Select NONE for no bypass valve or fan VFD control.
c) SP3. Select one to four fan outputs depending on the number of fan stages to be used. More

than one fan can be used per stage through the use of relays.

d) SP4. Select STAGE UP TIME from 1 to 60 minutes. The default value of 2 minutes is

probably a good starting point. The value may need to be adjusted later depending on actual
system operation.

e) SP5. Select STAGE DOWN TIME from 1 to 60 minutes. The default value of 5 minutes is

probably a good starting point. The value may need to be adjusted later depending on actual
system operation.

f) If TEMP is selected in SP1, use

i) SP6. Select STAGE DIFFERENTIAL in degrees F, start with default of 3 degrees F.
ii) SP8-11. Set the STAGE ON temperatures consistent with the temperature range over

which the condenser EWT is desired to operate. The default values of 70
80

°F and 85°F are a good place to start in climates with moderate wet bulb

°F, 75 °F,

temperatures. The number of STAGE ON setpoints used must be the same as SP3.

g) If LIFT is selected in SP1, use

i) SP7. Select STAGE DIFFERENTIAL in PSI. Start with default of 6 PSI.
ii) SP12-15. Start with default setpoints. The number of STAGE ON setpoints used must

be the same as SP3.

See

Figure 9, Field Wiring Diagram on page 31, for fan staging field wiring connection points.

46 OMM WMC-3 OITS

2. Tower Fan Staging With Bypass Valve Controlling Minimum EWT (VALVE SP)

1) TOWER SETPOINT Screen
a) SP1. Select TEMP if control is based on condenser EWT or LIFT if based on compressor

lift expressed in pressure.
b) SP2. Select Valve SP for control of bypass valve based on temperature or lift.
c) SP3. Select one to four fan outputs depending on the number of fan stages to be used.

More than one fan can be used per stage through the use of relays.
d) SP4. Select STAGE UP TIME from 1 to 60 minutes. The default value of 2 minutes is

probably a good starting point. The value may need to be adjusted later depending on

actual system operation.
e) SP5. Select STAGE DOWN TIME from 1 to 60 minutes. The default value of 5 minutes is

probably a good starting point. The value may need to be adjusted later depending on

actual system operation.
f) If TEMP is selected in SP1, use

i) SP6. Select STAGE DIFFERENTIAL in degrees F, start with default of 3 degrees F.

ii) SP8-11. Set the STAGE ON temperatures consistent with the temperature range over

which the condenser EWT is desired to operate. The default values of 70
80

°F and 85°F are a good place to start in climates with moderate wet bulb

°F, 75 °F,

temperatures. The number of STAGE ON setpoints used must be the same as SP3.

g) If LIFT is selected in SP1, use

i) SP7. Select STAGE DIFFERENTIAL in PSI. Start with default of 6 PSI.

ii) SP12-15. Start with default setpoints. The number of STAGE ON setpoints used must

be the same as SP3.

2) VALVE SETPOINT Screen
a) SP1, Select NC or NO depending if valve is closed to tower with no control power or open

to tower with no control power.

b) If TEMP was selected for fan control above, use

i) SP2, Set the VALVE TARGET (setpoint), usually 5 degrees below the minimum fan

stage setpoint established in TOWER SP11. This keeps full flow through the tower

until the last fan is staged off.
ii) SP4, Set VALVE DEADBAND, the default of 2 degrees F is a good place to start.
iii) SP8, Set MINIMUM VALVE POSITION when EWT is at or below SP9. Default is

0%.
iv) SP9, Set the EWT at which the valve position will be at (SP8). Default is 60

°F.

v) SP10, Set the initial valve position when EWT is at or above SP11. Default is 100%.

vi) SP11, Set the EWT at which initial valve position is set to SP10. Default is 90

°F.

vii) SP12, Set the minimum position to which the valve can go. Default is 10%.
viii) SP13, Set the maximum position to which the valve can go. Default is 100%.
ix) SP14, Set the control gain for error. Default is 25.
x) SP15, Set the control gain for slope. Default is 25.

NOTE: Setpoints 14 and 15 are site specific, dealing with system fluid mass, component

size and other factors affecting the reaction of the system to control inputs. These

setpoints should be set by personnel experienced with setting up this type of control.

OMM WMC-3 OITS 47

c) If LIFT was selected for fan control, use:

i) SP3, Set the VALVE TARGET (setpoint), usually 30 psi below the minimum fan stage

setpoint established in TOWER SP15. This keeps full flow through the tower until the

last fan is staged off.
ii) SP5, Set VALVE DEADBAND, the default of 6 psi is a recommended initial setting.
iii) SP12, Set the minimum position to which the valve can go. Default is 10%.
iv) SP13, Set the maximum position to which the valve can go. Default is 100%.
v) SP14, Set the control gain for error. Default is 25.

vi) SP15, Set the control gain for slope. Default is 25.

NOTE: Setpoints 14 and 15 are site specific dealing with system fluid mass, component

size and other factors affecting the reaction of the system to control inputs. These

setpoints should be set by personnel experienced with setting up this type of control.

Figure 23, Bypass Valve Positions

Initial Valve Position

Max Po sitio n

@ Setpoint

(90°F)

Min Position

@ Setpoint

(65°F)

Min Start Position
Set Point (10%)

See

Figure 9 on page 31 for fan staging and bypass valve field wiring connection points.

3. Tower staging with bypass valve controlled by fan stage (VALVE STAGE)

Max Start Position
Set Point (90%)

This mode is similar to #2 above except that the bypass valve setpoint changes to be set at the same
point of whatever fan stage is active rather than just maintaining a single minimum condenser EWT.
In this mode the valve controls between fan stages and tries to maintain the fan stage setting in
effect. When it is max open or max closed (staging up or down) and the temperature (or lift) moves
to the next fan stage, the valve will go the opposite max setting. This mode reduces fan cycling.

This mode is programmed the same as Mode #2 above except that in SETPOINT, TOWER, SP2,
VALVE STAGE is selected instead of VALVE SP and:

• SP6, Set the valve position (% open) above which the first fan can stage on (fan stage ON

temperature and STAGE UP TIMER must also be satisfied). Default is 80%.

• SP7, Set the valve position (% closed) below which the first fan can stage off (the fan stage

temperature and STAGE DOWN TIMER must also be satisfied). Default is 20%.

4. Fan VFD, no bypass valve (VFD STAGE) The fan VFD mode assumes the tower is driven by

one large fan. Set up is as above except in SETPOINT, TOWER, SP2, VALVE/VFD is selected.

48 OMM WMC-3 OITS

MOTOR Setpoint Screen

Figure 24, MOTOR Setpoint Screen

Table 22, MOTOR Setpoint Settings

Description No. Default Range

Nominal Capacity 10 100 0 to 9999 Tons Determines when to shut off a compressor
Maximum LWT Rate 9

Minimum LWT Rate 8
Soft Load Ramp Time 7 5 min 1 to 60 min M

Initial Soft Load Amp
Limit

Soft Load Enable 5 OFF OFF, ON M Soft load on or off Uses SP6 & 7
Nameplate RLA 4 52 to 113 Amps T RLA value from compressor nameplate

Maximum Amps 3 100% 10 to 100% T
Minimum Amps 2 40% 5 to 80% T % RLA below which unloading is inhibited

Demand Limit Enable 1 OFF OFF, ON O

6 40% 10 to 100% M Initial amps as % of RLA uses SP4 & 6

0.5

°F/min

0.1

°F/min

0.1 to 5.0
°F/min

0.1 to 5.0
°F/min

Pass-

word

M

M

Comments

Inhibits loading if LWT change exceeds the setpoint
value.

Additional compressor can start if LWT change is
below setpoint.
Time period to go from initial load point (% RLA) set
in SP 5 to 100% RLA

% RLA above which loading is inhibited (Load Limit)
SP + 5% unloads compresso

ON sets %RLA at 0% for 4 mA external signal and at
100% RLA for 20 mA signal
OFF – signal is ignored

OMM WMC-3 OITS 49

MODES Setpoints

Figure 25, MODES Setpoint Screen

NOTE

: Gray setpoints are not used with WMC chillers.

Table 23, MODE Setpoint Settings

Description No. Default Range

Comp # 2 Stage
Sequence

Comp # 2 Stage
Mode

Comp #1 Stage
Sequence

Comp #1 Stage
Mode

Max. Comp. ON 6 1 1-16 M Total number of compressors minus standby

BAS Protocol 5 MODBUS

Cond Pump 4

Evap Pump 3

Control Source 2 LOCAL LOCAL, BAS, SWITCH O Sets control source
Unit Enable 1 OFF OFF, AUTO O

10 1

9 Normal

8 1
7 Normal

Pump #1

Only

Pump #1

Only

1,2, … (# of

Compressors)

Normal, Efficiency,

Pump, Standby

1,2, … (# of

Compressors)

Normal, Efficiency,

Pump, Standby

None, Local, Remote

MODBUS LON, BACnet,

CSC

Pump #1 Only, Pump #2

Only, Auto Lead, #1
Primary, #2 Primary

Pump #1 Only, Pump #2

Only, Auto Lead, #1
Primary, #2 Primary

1. If both compressors have the same sequence number, they will automatically balance starts and run-hours.

2. See page 68 for further details on pump operation.

Pass-

word

Sets sequence number for # 2 compressor, if 1 it is

M

always first to start, if 2 is always second (Note 1)
Normal uses standard sequencing

Efficiency starts one compressor on each unit

M

Pump starts all compressors on one chiller first
Standby uses this compressor only if another fails.

Sets sequence number for # 1 compressor, if 1 it is

M

always first to start, if 2 is always second (Note 1)

M Ditto No. 9.

Sets BAS Standard Protocol to be used, or LOCAL

M

if none.
Pump #1 Only, Pump #2 Only, use only these

pumps

M

AUTO, balance hours between #1 and #2
#1 Primary, #2 Primary, if primary fails, use other

Pump #1 Only, Pump #2 Only, use only these
pumps

M

AUTO, balance hours between #1 and #2
#1 Primary, #2 Primary, if primary fails, use other

OFF, everything is off. AUTO, Evap pump on,
comp, cond pump and tower on as required to
meet LWT

Comments

50 OMM WMC-3 OITS

WATER Setpoints

Figure 26, WATER Setpoint Screen

Table 24, WATER Setpoint Settings

Description N0. Default Range

Max Reset Delta-T 7

Start Reset Delta-T 6

LWT Reset Type 5 NONE

Stage Delta-T 4 1.0
Startup Delta-T 3

Shutdown Delta-T 2
Cool LWT 1

0.0°F 0.0 to 20.0 °F

10. 0°F 0.0 to 20.0 °F
NONE, RETURN,

4-20mA

0.5 to 5°F

3.0°F 0.0 to 10.0 °F

3.0°F 0.0 to 3.0 °F

44. 0°F 40.0 to 80.0 °F

Pass-

word

Set the maximum reset that can occur, in

M

degrees F if LWT reset is selected or max reset
at 20 mA input if 4-20 mA is selected in SP7

Sets the evap delta-T above which Return reset

M

begins.
Select reset type, NONE for none, RETURN for

M

reseting chilled water based on the entering
water, or 4-20 mA for external analog signal

Sets the temperature the leaving water must be

M

above setpoint for next compressor to start.
M Degrees above setpoint for compressor to start.
M Degrees below setpoint for compressor to stop.
M Evaporator LWT setpoint in COOL mode

Comments

OMM WMC-3 OITS 51

Active

p

LAN

Nodes

SERVICE Screen

Figure 27, Service Screen

The SERVICE screen is accessed by pressing SET from any SET screen. In other words, it is the
second "SET" screen. While containing information and activity buttons for the service technician,
it also has valuable information for the operator.

The upper left corner contains compressor information such as number of starts and operating hours
for each compressor. "Spare Capacity" is used to set the compressor stopping increments.

The Active pLAN Nodes matrix shows active control components on the pLAN. A, B, C, D are
individual chillers. 1 and 2 are compressor controllers, 5 is the unit controller and 7 is the interface
panel.

pLAN Comm is used for setting up multiple chillers and is set at startup by the McQuay startup
technician as is LOAD UCM.

CHANGE UNITS button allows selection of Inch-Pounds or Metric units of measure on the OITS
SELECT LANGUAGE allows toggling between the available languages. The language can be set

separately for display or history, which is used for alarm and trend files.
The version numbers shown in the lower left corner are the controllers' software identification. The

number in the upper right corner is the Operator Interface Panel software identification number.
These numbers may be required by McQuay to answer questions about unit operation or to assist in
possible future upgrades of software.

The PASSWORD button is used to access the Keyboard screen to enter a password.
The Alarm ON/OFF button is usually only found on demonstration software.
The red ALARM light appears on this, and many other screens, when an alarm becomes active.

There is no alarm active on this demonstration screen, so the Alarm shows as dark blue.
OPERATING MANUAL displays the manual in Adobe. It can be downloaded via the USB port.
PARTS LIST displays the list. It may not be active on some units.

52 OMM WMC-3 OITS

HISTORY Screens

Figure 28, History Trend Graph

The Trend History Overview allows the user to view the various parameters listed on the right side
of the screen. The temperature scale in
represented by the right-hand scale. The screen can display history for 8 hour, 2 hour or 20-minute
periods by pressing 8, 2, or 1/3 respectively.

Pressing NOW for any time period will start the display for the current time beginning on the right
of the screen with history flowing to the left.

The arrow buttons scroll the time period forward or backward. Obviously, if NOW is selected, the
forward button > will not go into the future.

The COMP button toggles between compressors one and two.

°F is on the left. Pressure in psi and % RLA are

OMM WMC-3 OITS 53

Figure 29, Alarm History/Floppy Download

The Alarm History lists the alarms with the most current on top with date stamp, action taken and the cause of
the alarm. It is accessed from the history screen by pressing HISTORY again.

The alarms have a color code as follows:

• Faults (shutdowns) = Red

• Problems (limit alarms) = Yellow

• Warnings (notifications) = Dark Blue

Download Data

This screen is also used to download the Trend History (Figure 28) selected by date or the Alarm History
shown above. Download to a USB memory device via a USB port located in the control panel.

• For Alarms, press the ALARMS button on the screen, then press the COPY to USB button.

• For Trend History, select the desired History File by date using the PREV or NEXT buttons, then press

the COPY to USB button.

54 OMM WMC-3 OITS

ACTIVE ALARM Screen

Figure 30, Active Alarms

The Active Alarm screen is only accessible when an active alarm exists on the unit. Pressing the
red alarm signal on any screen will access this screen. It can also be accessed from the SERVICE
screen by pressing the dark blue button (where the Alarm indicator normally appears). There are
no alarms active on this demonstration screen.

Alarms are arranged in order of occurrence, with the most recent on top. Once the abnormal
condition is corrected, pressing the "CLEAR" key will clear the alarm.

The current active alarms (there may be more than one) are displayed. Note that the alarms are
color-coded red for FAULT (equipment protection control) that causes a rapid compressor
shutdown, yellow for PROBLEM (limit alarm) that will inhibit loading, or load or unload the
compressor, and blue for WARNING which is information only and takes no action. Faults,
Problems, and Warnings as detailed on pages

The date/time and cause of the alarm are displayed.
After eliminating the cause of the alarm, clear the alarm by pressing the CLEAR button. This will

clear the alarm from the register and allow the unit to restart after going through the start sequence.
The alarm notice will be deleted from the screen.

However, if the cause of the alarm is not remedied, the alarm is still active and the alarm message
will remain open. The unit will not begin its starting sequence

21 and 25.

OMM WMC-3 OITS 55

Figure 31, Keyboard

The keyboard is only used to enter the password when attempting to enter or change a setpoint.
Input the number (100 for operator, 2001 for manager level) and press Enter to enter the password.
The screen will automatically revert back to the previous Set screen.

This screen will appear automatically when a password is required for changing a setpoint. It can
also be access from the service screen (second set screen) by pressing PASSWORD.

56 OMM WMC-3 OITS

Unit Controller Menu Screens

The unit controller, located in the control panel adjacent to the OITS, is the only controller used by
the unit operator. In addition to unit functions, most compressor parameters are viewable on it, and
all setpoints can be accessed from it.

Unit of Measure

SI units of measure can be selected with the appropriate setpoint screen but will appear only on the
OITS. The controller screens read only in inch-pounds unit of measure.

Menu Structure (Hierarchical)

A hierarchical menu structure is used to access the various screens. Each menu screen can have
one to four lines of information. Optionally, the last menu selection can access one of a set of
screens that can be navigated with the UP/DOWN arrow keys (see the scrolled menu structure
below). Menu selection is initiated by pressing the MENU key, which changes the display from a
data screen to a menu screen. Menu selections are then made using the arrow keys according to
labels on the right side of the display (the arrows are ignored). When the last menu item is
selected, the display changes to the selected data screen. An example follows showing the
selection of the “VIEW COMPRESSOR (n) screen.

Suppose the current screen is:

ALARM LOG
(data)
(data)
(data)

After pressing the MENU button, the top-level menu screen will show:

< ALARM
< VIEW
< SET
<

After pressing the “VIEW” menu button, a menu screen will show:

VIEW < COMPRESSOR
< UNIT
< EVAPORATOR
< CONDENSER

After pressing the “COMPRESSOR” menu button, the selected data screen will show:

VIEW COMP (n)
(screen n data)
(screen n data)
(screen n data)

Where “n” is the number of the last viewed COMPRESSOR screen. The arrow keys will
automatically return to the “scroll” mode at this time. Different compressor screens can then be
selected with the UP/DOWN arrow keys.

OMM WMC-3 OITS 57

The complete menu structure follows. Data screens are shown as [data] when a single screen is at
the bottom of the menu structure and as [data n] when multiple screens are available (using
UP/DOWN keys).

Menu Structure (Scrolled)

As an alternate to selecting screens with the menu function, it is be 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 in
Figure 32.

Menu Matrix

Figure 32, Unit Controller Menu Matrix

View Unit Information View Compressor Information

VIEW UNIT
STATUS(1)
UNIT= OFF
COMP#1 OFF #2RUN
Ev/Cn Pmps=OFF/OFF

VIEW UNIT
STATUS(2)
Comp#1 OFF
Start-Start Tmr Clr
Inhibits None

VIEW UNIT
STATUS(3)
Comp#2 RUN
Start-Start Tmr Clr
Inhibits None
VIEW COMP (4) oF

VIEW COMP (5) oF

VIEW COMP (7)

VIEW UNIT
WATER(1)oF
In Out Delta
Evap 00.0 00.0 00.0
Cond 00.0 00.0

00.0
VIEW UNIT
WATER (2)
IN OUT
DELTA
HtRc NA NA NA
Cond NA
VIEW UNIT
WATER (3)
Water Flow Rates
Evap = XXXXX GPM
Cond = XXXXX GPM

VIEW COMP (6)

VIEW UNIT REFRG (1)
psi oF
Sat Evap 000.0 000.0
Sat Cond 000.0 000.0

VIEW UNIT REFRG (2)
Suct Line = 000.0oF
Liquid Line = 000.0oF
Lift Press = 000.0psi

VIEW COMP (3) psi

VIEW UNIT TOWER (1)
Stages ON= 0 of 2

Setpoint= XXX °F

VIEW UNIT TOWER (2)
Bypass Valve= XXX%
VFD Speed = XXX%

VIEW COMP 31 (1)
State = OFF
% RLA = 000%
Evap LWT =

054.0oF

VIEW COMP (2) psi
Cond Press = 000.0
Evap Press = 000.0
Lift Press = 000.0

WMC Compressor
Oilless Design

(blank mask page)

Cavity Temp=000.0°F
Invert Temp=000.0°C
Lift Temp = 00.0°F

Temp
SH
Suction 000.0 00.0
Discharge 000.0 00.0

psi oF
SatEvap 000.0 000.0
SatCond 000.0 000.0

Hours = 00000 x10
Starts = 00000

VIEW COMP#2 (1)
State = RUN
% RLA = 095%
Evap LWT = 054.0oF

VIEW COMP#2 (2) psi
Cond Press = 000.0
Evap Press = 000.0
Lift Press = 000.0

VIEW COMP#2 (3) psi
WMC Compressor
Oilless Design
(blank mask page)

VIEW COMP#2 (4) oF
Cavity Temp=000.0°F
Invert Temp=000.0°C
Lift Temp = 00.0°F
VIEW COMP#2 (5) oF
. Temp SH
Suction 000.0 00.0
Discharge 000.0 00.0

VIEW COMP#2 (6)
psi oF
SatEvap 000.0 000.0
SatCond 000.0 000.0
VIEW COMP#2 (7)
Hours = 00000 x10
Starts = 00000

The right half of the matrix is continued on next page

NOTE 1, There is a VIEW CONDENSER menu to the right of VIEW EVAPORATOR, but omitted from this matrix due to

space limitations.

View

Evaporator

VIEW EVAPORATOR
Suct SH = 000.0oF
Approach = 00.0oF

See NOTE 1

58 OMM WMC-3 OITS

Table Continued

VIEW ALARMS SET SETPOINTS PASSWORD

Alarm Log: 01
description
HH:MM:SS
MM/DD/YY
Alarm Log: 02
description
HH:MM:SS
MM/DD/YY .
Alarm Log: 03 to 25
description
HH:MM:SS
MM/DD/YY

^ SET UNIT SPs (4)

^ SET UNIT SPs (5)

^ SET UNIT SPs (6)

Alarm Log: 25
description
HH:MM:SS
MM/DD/YY

SET UNIT SPs (1)
Unit Enable = OFF
Unit Mode = COOL
Source = SWITCHES
SET UNIT SPs (2)
Available Modes
= COOL
Select w/Unit Off
SET UNIT SPs (3)
Cool LWT = 44.0°F

Leaving Water Temp
StartDelta = 3.0°F
StopDelta = 3.0°F

Rest Type = NONE
MaxResetDT =00.0oF
StrtResetDT = 10.0oF

Soft Load = OFF
BeginAmpLimit= 040%
SoftLoadRamp=05min
SET UNIT SPs (7)
Max/Min LWT Rates
Max = 0.5oF/min
Min = 0.1oF/min

SET UNIT SPs (8)

EvapRecTmr = 0.5min
EvapPump = #1 ONLY
CondPump = #1 ONLY

SET UNIT SPs (9)

Templifier Src Water
No Start = 070oF
Delta Reset = 055oF
Ignore this menu

SET UNIT SPs (10)

VFD = YES
Min Speed =015%-KW
Max Kw = 076.0
Ignore this menu

SET UNIT SPs (11)

Max Wtr Flow Rates
Evap WF=02400GPM
CondWF=03000GPM

SET UNIT SPs (12)

Time
Day/Mon/Yr
24 hr time day of wk

SET UNIT SPs (13)

Display Format
Units = oF/psi (IP)
Lang = English

SET UNIT SPs (14)

Protocol = MODBUS
Id #= 001 Units =IP
Baud Rate = 19200

SET UNIT SPs (15)

Ex-Val Std Values
Pos 450% L76.0psi
Enthalpy Sp 85.0°F
Ignore this menu

SET COMP#1 SPs (1)
Demand Limit=OFF
Minimum Amps=040%
Maximum Amps=100%
SET COMP SPs (2)
StageMode =Normal
StageSequence# = 01
Max Compr ON = 01
SET COMP SPs (3)
StageDeltaT = 1.0oF
Stop-Start = 03 min
Start-Start = 40 min
SET COMP SPs (4)
Full Load = 300 sec
Name Plate RLA 085

SET COMP SPs (5)

Nom Capacity = 0100T

SET COMP SPs (6)
InterLokTmr= 010sec
UnloadTimer = 030 sec

SET COMP SPs (7)
WMC Automatic
Vane Control
(blank mask page)
SET COMP SPs (8)
MAX KW = 76.0
Lag Start = 000Sec
Step Down = 060Sec
SET COMP SPs (9)
Protocol =M-BUS
MSTR
Ident Number= 001
Baud Rate = 19200
SET COMP SPs (10)
Refrg Sat Pressure
Evp Offset =+00.0 psi
Cnd Offset = +00.0psi

SET COMP SPs (11)
ELWT Offset = +0.0 oF

SET COMP#2 SPs (1)
Demand Limit=OFF
Minimum Amps=040%
Maximum Amps=100%
SET COMP#2 SPs (2)
StageMode =Normal
StageSequence# = 01
Max Compr ON = 01
SET COMP#2 SPs (3)
StageDeltaT = 1.0oF
Stop-Start = 03 min
Start-Start = 40 min
SET COMP#2 SPs (4)
Full Load = 300 sec

SET COMP#2 SPs (5)

Nom Capacity = 0100T

SET COMP#2 SPs (6)
UnloadTimer = 060 sec
PostlubeTmr = 030 sec

SET COMP SPs (7)
WMC Automatic
Vane Control
(blank mask page)
SET COMP SPs (8)
MAX KW = 76.0
Lag Start = 000Sec
Step Down = 060Sec
SET COMP SPs (9)
Protocol =M-BUS
MSTR
Ident Number= 001
Baud Rate = 19200
SET COMP#2 SPs (10)
Refrg Sat Pressure
Evp Offset =+00.0 psi
Cnd Offset = +00.0psi

SET COMP#2 SPs (11)
ELWT Offset = +0.0 oF

SET ALARM LMTs (1)
LowEvPrHold=33psi
LowEvPrUnld=31psi
LowEvPrStop=29psi
SET ALARM LMTs (2)
HighCondPr =140psi
HiDschT-Load=170oF
HiDschT-Stop=190oF
SET ALARM LMTs (3)
WMC Compressor
Oilless Design
(blank mask page)
SET ALARM LMTs (4)
Surge Slp Str=20oF
Surge Tmp Run=06oF
MtrCurThrshld=10%
SET ALARM LMTs (5)
Evap Freeze= 34.0°F
Cond Freeze= 34.0°F

SET TOWER SPs (6)

SET TOWER SPs (7)

SET TOWER SPs (8

SET TOWER SPs (1)
TowerControl=(type?)
Tower Stages=4
StageUP/Dn=080/020
SET TOWER SPs (2)
Stage ON
#1 #2 #3 #4
xxx xxx xxx xxx
SET TOWER SPs (3)
StageDiff= (type?)
StageUp = 02 min
StageDown=05 min
SET TOWER SPs (4)
Valve/VFD Control=
None
Valve Type=NC
SET TOWER SPs (5)
Valve Sp= (type?)
Valve DB= (type?)

ValveStartPosition
Min=010% @ 060oF
Max=090% @ 090oF

Valve Control Range
Min = 010%
Max = 090%

PD Control Loop
Error Gain = 25
Slope Gain = 25

SET PASSWORD
Enter
Password:00000
No Access Given
SET PASSWORD (2)
Tech Password
00000 00000
No Access Given

OMM WMC-3 OITS 59

Selection can then be made by using the LEFT/RIGHT keys to move between columns and the
UP/DOWN keys to move between rows.

If the VIEW COMP#2 (3) screen is being viewed and the RIGHT arrow key is pressed, the display
will show VIEW EVAP. If the LEFT arrow key is then pressed, the display will show VIEW
COMP#2 (3) again (not VIEW COMP (1)).

Attempts to scroll past the limits of the matrix are ignored.

Screen Definitions – VIEW

The following screens are shown in °F/psi. When the Display Units setpoint is set to °C/kPa, the
units of measure on the OITS will change accordingly. The unit and compressor controllers will
always be in inch-pounds.

View Unit Status

VIEW UNIT STATUS (1)
Unit=COOL
COMP#1 OFF #2 RUN
Ev/Cn Pmps=STRT/RUN

Unit states can be OFF, COOL, SHUTDOWN, and ALARM as determined from the Unit State
variable, the Unit Mode setpoint, and the presence of a unit shutdown alarm.

Compressor states can be OFF, START, HOLD, LOAD, UNLOAD, SHUTDN, and ALARM as
determined from the Comp State variable, the Load and Unload outputs, and the presence of a
compressor shutdown alarm.

Evap and Cond Pump states can be OFF, STRT (start), & RUN

VIEW UNIT STATUS (2)
COMP#1 = OFF
Start-Start Tmr Cir
Inhibits-None

Inhibits are signals that prevent further loading such as Load Limit, High Discharge Pressure, etc.

VIEW UNIT STATUS (3)
COMP#2 = OFF
Start-Start Tmr Cir
Inhibits-None

Inhibits are signals that prevent further loading such as Load Limit, High Discharge Pressure, etc.

View Water Status

VIEW UNIT WATER°F(1)
In Out Delta
Evap XX.X XX.X XX.X
Cond XX.X XX.X XX.X

VIEW UNIT WATER°F(2)
In Out Delta
HtRC
Cond XX.X XX.X XX.X

This screen deals with a heat recovery option not currently available on WMC units.

60 OMM WMC-3 OITS

VIEW UNIT WATER°F(3)
Water Flow Rates
Evap = XXXXX GPM
Cond = XXXXX GPM

View Refrigerant Status

VIEW UNIT REFRG (1)
psi °F

Sat Evap XXX.X XX.X
Sat Cond XXX.X XX.X

VIEW UNIT REFRG (2)
Suct Line = XXX.X°F
Liquid Line= XXX.X°F

Lift Press =XXXX psi

View Tower Status

Towe r Contro l = Temp/ None Tower Co ntrol = L ift

VIEW UNIT TOWER (1) VIEW UNIT TOWER (1)
Stages ON = 2 of 4 Stages ON = 2 of 4

Setpoint = XXX °F

The first Stages ON value is the number of fan stages ON. The second number is the Tower Stages
setpoint (0 if Tower Control = None).

Setpoint = XXXX psi

VIEW UNIT TOWER (2)
Bypass Valve = XXX%
VFD Speed = XXX%

The Bypass Valve value is “None” (in place of XXX%) if the Valve/VFD Control setpoint = None
or VFD Stage. The VFD Speed value shall be “None” if the Valve/VFD Control setpoint = None,
Valve Setpoint, or Valve Stage.

View Compressor Status

NOTE: In the following VIEW COMP screens, the #N field indicates which compressor (#1, or

#2,) is being viewed. There are two columns of menus, the first for compressor #1, the second for
#2.

VIEW COMP#N (1)
State = RUN
% RLA = XXX %

Evap LWT =000.0°F

State settings can be OFF, START, INTLOK, HOLD, LOAD, UNLOAD, SHUTDOWN, STOP,
and ALARM as determined from the Comp State variable, the Load and Unload outputs, and the
presence of a compressor shutdown alarm.

OMM WMC-3 OITS 61

VIEW COMP#N (2)psi
Cond Press =XXXX
Evap Press =XXXX
Lift Press = XXX

VIEW COMP#N (3) psi
WMC Compressor
Oilless Design
(blank menu)

VIEW COMP#N (4) °F
Cavity Temp=XXX.X°F
Invert Temp=XXX.X°C
Lift Temp = XX.X°F

VIEW COMP#N (5) °F
Temp SH
Suction XXX.X XX.X
DischargeXXX.X XX.X

VIEW COMP#N (6)
psi °F
SatEvap XXX.X XXX.X
SatCond XXX.X XX.X

VIEW COMP#N (7)
Hours = XXXXX
Starts = XXXXX

The following menus are found only on the compressor controllers and contain detailed
information on the compressor operation, used only by trained compressor technicians.

VIEW COMP#N (8)
WMC Compressor Rdy
Mode3 Unit0 Float0
Auto Demand 000.0KW

VIEW COMP#N (9)RPM
Min=00000 Act=00000
Max=00000 Des=00000
Ver=419 Serial=0000

VIEW COMP#N(10)Alrms
Ctl----------------­BearingF-00000A00000
Motor F-00000A00000

62 OMM WMC-3 OITS

VIEW COMP#N (11)Pwr
L1=458V 000.0Amps
L2=458V 000.0Amps
L3=458V 000.0Amps

VIEW COMP#N(12)Bear
FX 00000 RX 00000
FY 00000 RY 00000
AX 00000 Ver3939 Off

VIEW COMP#N(13)S-Str
UpTrp=0530 Vdrp 0000
DnTrp=0380 RxV 0654
Ver=00136 Ok SCR-On

VIEW COMP#N (14) Psi
IGV=020.0 DisC=082.6

024.9 Suct=081.9
00000Alr Intr=000.0

VIEW COMP#N(15)Temps
Suct=89.4 Cav=093.9
SCR=090.8 Ent=077.4
Disc=090.7 Lev=077.4

VIEW COMP#N(16)Motor
S_SP 0017
Spdly 0000
Inv_Temp 031.0 deg C

View Vessel Status

VIEW EVAPORATOR
Suct SH = XXX.X °F
Approach = XX.X °F

Press right arrow to view the condenser data.

VIEW CONDENSER
Disch SH = XXX.X °F
Approach = XX.X °F
Subcooling= XX.X °F

OMM WMC-3 OITS 63

View Alarms

ALARM LOG 01
Description

hh:mm:ss dd/mmm/yyyy

ALARM LOG 02 to 25
Description

hh:mm:ss dd/mmm/yyyy

ACTIVE ALARM
Time Date
Fault Description

Set Unit Setpoints

The following screens are only shown in °F/psi. Setpoint default vales and available setting range
can be found in

Table 6 on page 20.

SET UNIT SPs (1)
Unit Enable = OFF
Unit Mode = COOL
Source = SWITCHES

Unit Enable settings can be OFF and ON as determined from the Unit Enable setpoint.
Unit Mode settings can be COOL, or TEST as determined from the Unit Mode setpoint (TEST

mode is not be selectable from the 4x20 display/keypad although it may be displayed if already
set).

Source settings can be KEYPAD, SWITCHES, or NETWORK as determined from the Mode
Source setpoint.

SET UNIT SPs (2)
Available Modes
= COOL
Select w/Unit Off

Available Modes settings for WMC chillers can be COOL. The unit must be turned off to change
this setpoint.

SET UNIT SPs (3)
Cool LWT = XX.X°F

Ice LWT = XX.XF
Heat LWT = XX.XF

Ignore any setting other than COOL LWT should they appear on this menu.

SET UNIT SPs (4)
Leaving Water Temp

StartDelta= 03.0°F
StopDelta = 03.0°F
SET UNIT SPs (5)

64 OMM WMC-3 OITS

Reset Type =none
MaxResetDT =XX.X°F
StrtResetDT=XX.X°F

Reset Type settings can be NONE, RETURN, or 4-20 as determined by the LWT Reset Type
setpoint.

SET UNIT SPs (6)
Soft Load = OFF
BeginAmpLimit=40%
SoftLoadRamp=05min

Soft Load settings can be OFF or ON as determined from the Soft Load setpoint.

SET UNIT SPs (7)
Max/Min LWT Rates

Max = 0.5°F/min
Min = 0.1°F/min

Pump Selection

SET UNIT SPs (8)
EvapRecTmr =X.Xmin
EvapPump = #1 ONLY
CondPump = #2 PRIM

The Evaporator Water Pump outputs will be controlled in a Primary/Standby manner according to
the Evap Pump setpoint which may be set to #1 Only, #2 Only, Auto, #1 Primary/#2 Standby, or #2
Primary/#1 Standby.

• If #1 Only is selected, only pump #1 will be started even in event of a failure.

• If #2 Only is selected, only pump #2 will be started.

• If Auto is desired, the unit will try to balance operating hours on each pump by starting the

pump with the least amount of operating hours first. In case of pump failure, the unit will start
the backup pump.

• In standby mode, the primary pump will always be started first. The standby pump will only

be started if there is a failure indicated on the primary pump.

An Evaporator Water Pump 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.

SET UNIT SPs (9)
Templifier Scr Water

No Start =070°F
Delta Reset=055°F

This menu does not apply to WMC chillers and should be ignored.

SET UNIT SPs (10)
VFD = Yes

OMM WMC-3 OITS 65

Min Speed = XXX%
Max Kw = 076.0

VFD settings are controlled by the compressor on-board microprocessor and these settings are not
used.

SET UNIT SPs (11)
Max Wtr Flow Rates
Evap WF = 02400 GPM
Cond WF = 03000 GPM

These settings are used to calibrate customer-supplied flow switches.

SET UNIT SPs (12)
STD/Day Light Time
dd/mmm/yyyy
hh:mm:ss Day of week

SET UNIT SPs (13)
Display Format

Units = °F/psi (IP)
Lang = English

SET UNIT SPs (14)
Protocol = Modbus
Id#= 001 Units=IP
Baud Rate = 19200

SET UNIT SPs (15)
EX-Val Std Values
Pos 450% L76.0psi
Enthalpy Sp 85.0°F

This menu is used for setting certain electronic expansion valves and does not apply to WMC
chillers.

Set Compressor Setpoints

NOTE: In the following SET COMP screens, the #N field indicates which compressor (#1, or #2 )
is being set. There is basically a column of menu screens for each compressor.

SET COMP#N SPs (1)
Demand Limit = OFF
Minimum Amps = 010%
Maximum Amps = 100%

Demand Limit settings can be OFF or ON as determined from the Demand Limit setpoint.

SET COMP#N SPs (2)
StageMode = NORMAL
StageSequence# =01
Max Comprs ON =02

66 OMM WMC-3 OITS

StageMode settings can be NORMAL, HI EFF, PUMP, and STANDBY as determined by the Stage
Mode setpoint.

NORMAL has the auto-balance sequence that starts compressors with least starts and stops
compressors with most hours, in sequence, providing all compressors have the same sequence
number. If they have different sequence numbers, say 1, 2, 3, 4, they will always start in that
sequence. That is, sequence number will take precedence over auto-balance sequencing.

HI EFF is used with multiple chillers and runs one compressor per chiller when ever possible.
PUMP starts all compressors on the same chiller first, starting with the chiller with the compressor

with the least starts (or by sequence number if they are different).
STANDBY is used in multi-compressor systems and reserves a compressor to come on only if

there is a failure of another compressor in the system and the standby compressor capacity is
required to maintain chilled water temperature.

StageSequence is set for each compressor:
In NORMAL or STANDBY Mode, all compressors can have the same number or a number from 1

up to the total number of compressors. Sequence number has priority over other considerations. If
four compressors in a system are given the sequence numbers 1 through 4, they will always start in
that order. With the same number they will auto-sequence.

In HI EFF or PUMP, all compressors must have the same sequence number.
Max Comprs ON limits the number of compressors allowed to run in multi-compressor systems. It

provides a "floating standby" compressor. All compressor controllers must have the same setting
for this setpoint.

SET COMP#N SPs (3)
StageDeltaT =1.0°F
Stop-Start =03min
Start-Start =40min

SET COMP#N SPs (4)
Full Load = 300sec
Name Plate RLA 085

Full Load timing is one of several “full load flags”, parameters that indicate a compressor is at full
load.

SET COMP#N SPs (5)

Nom Capacity=0100T
Hotgasbypass =

Ignore hot gas bypass setting. WMC are not so equipped.

SET COMP#N SPs (6)
IntrLokTmr=010sec
UnloadTimer=030sec

Max Str LWT = XXX°F

Ignore Max Str LWT setting.

OMM WMC-3 OITS 67

SET COMP#N (7)
WMC Automatic
Vane Control
(blank menu)

Ignore this menu on WMC chillers.

SET COMP#N (8)
MAX KW = 076.0
Lag Start = 000Sec
Step Down = 060Sec

Staging Parameters

Full Load Determination

Each compressor determines if it is at its maximum capacity (or maximum allowed capacity) and,
if so, set its Full Load flag. The flag advises other components that the compressor is fully loaded.
The flag is set (full load) when one or more of the following conditions are met.

• The compressor is at its physical limit of capacity which means:

For VFD Set Point = NO: The load output has been pulsed ON for a cummulative time equal to
or greater than the Full Load set point (menu #4). Any unload pulse will reset the cummulative
time to zero.

For VFD Set Point = YES: Load pulsing has exceeded the Full Load set point (as described
above) AND the VFD speed = 100%

OR

The Vanes Open digital input is On AND the VFD speed = 100%.

• The %RLA is above or equals the Maximum Amp limit set point.

• The %RLA is above or equals the Demand Limit analog input value

• The %RLA is above or equals the Network Limit value

• The evaporator pressure is below the Low Evap Pressure-Inhibit set point.

When none of the above conditions are met, the Full Load flag is cleared.

Absolute Capacity

Each compressor estimates its absolute capacity from the present value of %RLA and the Absolute
Capacity set point from the equation:

Absolute Capacity = (%RLA Factor) * (Absolute Capacity set point)
Where the %RLA Factor is interpolated from the following table.

%RLA 0 50 75 100 150
%RLA Factor 0 0.35 0.75 1.00 1.50

SET COMP#N (9)
Protocol =M-BUS MSTR
Ident Number= 001
Baud Rate = 19200

68 OMM WMC-3 OITS

SET COMP#N (10)
Refrg Sat Pressure
Evp Offset=+00.0psi
Cnd Offset=+00.0psi

SET COMP#N (11)
ELWT Offset=+00.0°F

Set Alarm Limits

SET ALARM LMTS (1)
LowEvPrHold=33psi
LowEvPrUnld=31psi
LowEvPrStop=29psi

SET ALARM LMTS (2)
HighCondPr = 140psi

HiDschT-Load=170°F
HiDschT-Stop=190°F

SET ALARM LMTS (3)
WMC Compressor
Oilless Design
(blank mask page)

SET ALARM LMTS (4)
Surge Slp Str=20°F
Surge Tmp Run=12°F

MtrCurrThrshld=05%

Only trained compressor technicians should set these setpoints.

SET ALARM LMTS (5)
Evap Freeze=34.0°F
Cond Freeze=34.0°F

Set Tower Setpoints

SET TOWER SPs (1)
TowerControl = None
Tower Stages = 2
StageUP/DN=080/020%

Tower control settings can be None, Temp, or Lift.

OMM WMC-3 OITS 69

Towe r Contro l = Temp/ None Tower Co ntrol = L ift

SET TOWER SPs (2) SET TOWER SPs (2)
Stage ON (Temp)°F

Stage ON (Lift)psi

#1 #2 #3 #4 #1 #2 #3 #4
XXX XXX XXX XXX XXX XXX XXX XXX

Tower Control = Temp/None To wer Control = Lift(psi)

SET TOWER SPs (3) SET TOWER SPs (3)
StageDiff = XX.X°F

StageDiff =XX.Xpsi

Stage Up = XX min Stage Up = XX min
StageDown = XX min StageDown = XX min

SET TOWER SPs (4)
Valve/VFD Control=
ValveSP/VFDStage
Valve Type = NC

Valve/VFD Control settings are None, Valve Setpoint, Valve Stage, VFD Stage, or
ValveSP/VFDStage. Valve Type settings are NC (normally closed to tower) or NO (normally
open).

Towe r Contro l = Temp/ None Tower Co ntrol = L ift

SET TOWER SPs (5) SET TOWER SPs (5)
Valve SP = XXX °F
Valve DB = XX.X °F

Valve SP = XXX psi
Valve DB = XXX.Xpsi

SET TOWER SPs (6)
ValveStartPosition

Min = 010% @ 060°F
Max = 100% @ 090°F

SET TOWER SPs (7)
Valve Control Range
Min = 010%
Max = 100%

SET TOWER SPs (8)
PD Control Loop
Error Gain = 25
Slope Gain = 25

Tower fan control is active when the Tower Control setpoint is set to Temperature or Lift and the
condenser pump is in the RUN state. Staging is based on either Entering Condenser Water
Temperature (ECWT) or Lift pressure as selected by the Tower Control setpoint. Operation
depends on the following parameters.

• Condenser pump state

• ECWT OR Lift pressure

• Stage up and stage down timer values

70 OMM WMC-3 OITS

• Tower setpoints (Tower Control, Tower Stages, Stage Up Time, Stage Down Time, Stage

Differential (Temp OR Lift), Stage #1 ON (Temp OR Lift), Stage #2 ON (Temp OR Lift),

Stage #3 ON (Temp OR Lift), Stage #4 ON (Temp OR Lift), Stage Down @, Stage Up @)
The stage up timer starts when the condenser pump starts. The first stage turns ON when the
following conditions are met:

• The stage up timer completes

• The ECWT is > Stage #1 ON (Temp) setpoint (only if the Tower Control setpoint =

Temperature)

• The Lift pressure is > Stage #1 ON (Lift) setpoint (only if the Tower Control setpoint = Lift)

• 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 occus when the the following conditions are met:

• The stage down timer completes

• The ECWT is < Stage #X ON (Temp) setpoint – Stage Differential (Temp) setpoint point

(only if the Tower Control setpoint = Temperature).

• The Lift pressure is < Stage #X ON (Lift) setpoint – Stage Differential (Lift) setpoint point

(only if the Tower Control setpoint = Lift)

• 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 restarts both the stage up and stage down timers. Only one fan
output is switched at a time (except that all outputs switch OFF when the condenser pump state
equals OFF).

Analog Output Control

Each analog output is controlled according to the following rules/algorithms and in accordance
with whether the Compressor Mode setpoint is set to AUTO or MANUAL (normal operation) or
TEST (test mode). All outputs are initialized to 0 at power on.

Cooling Tower Bypass Valve

When the Valve/VFD Control setpoint is set to None OR VFD Stage, this output is set to 0.
Otherwise, it is controlled as described below.

Initial Valve Position

When the condenser pump is not in the RUN state, the valve output is set as a function of entering
condenser water temperature (ECWT)) per the following graph.

OMM WMC-3 OITS 71

Figure 33, Bypass Valve Position

(values are examples only)

Max Position @

Set Point

(90°F)

Min Position @

Set Point

(60°F)

Initial Valve Position

Min Start Position

Set Point (10%)

Normal Operation

Max Start Position

Set Point (90%)

When the condenser pump is in the RUN state, the valve output is controlled in one of two modes
as specified by the Valve/VFD Control setpoint. The controlled parameter (CP) is either ECWT or
Lift as specified by the Tower Control setpoint. When the desired output signal varies from 0 to
100%, the output voltage will vary as follows.

• 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 (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 is computed once every 5 seconds according to
the following equation.

• Increment = [(Error) * (Error Gain setpoint)] + [(Slope) * (Slope Gain setpoint)]

• Where: Error = ECWT – Valve Setpoint (Temp), (only if Tower Control setpoint =

Temperature)

• Error = Lift – Valve Setpoint (Lift), (only if Tower Control setpoint = Lift)

• Slope = (Present CP) – (Previous CP)

When the Error is > the Valve Deadband (Temp OR Lift as appropriate) 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.

Table 25, Valve Staging

# Of Fans ON Active Setpoint

0 Valve Setpoint (Temp OR Lift as appropriate)
1 Stage #1 ON (Temp OR Lift as appropriate)
2 Stage #2 ON (Temp OR Lift as appropriate)
3 Stage #3 ON (Temp OR Lift as appropriate)
4 Stage #4 ON (Temp OR Lift as appropriate)

72 OMM WMC-3 OITS

Cooling Tower Fan VFD

Normal Operation

When the Valve/VFD Control setpoint is set to None, Valve Setpoint, OR Valve Stage, this output
is set to 0. Otherwise, it shall be controlled in a manner identical to Valve Stage Mode (above)
except that (1) it is 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)

• Valve Type

Editing

Editing is accomplished by pressing the ENTER (lower-right key) key until the desired field is
selected. This field is indicated by a blinking cursor under it.. The arrow keys then operate as
follows.

CANCEL (
DEFAULT (
INCREMENT (
DECREMENT (
During edit mode, the display shows a two-character wide menu pane on the right as shown below.

⇒ Key) Reset the current field to the value it had when editing began.

⇐ Key) Set value to original factory setting.

⇑ Key) Increase the value or select the next item in a list.

⇓ Key) Decrease the value or select the previous item in a list.

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, 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 log 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.

Display Languages

It will be possible to select multiple languages from the keypad at any time. Languages currently
available are:

• English

Units of Measure

It is possible to select units of measure directly from the keypad. Systems available are:

• °F / psi: unit controller, compressor controller, touch screen

• °C / kPa: touch screen only

OMM WMC-3 OITS 73

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 in one of three ways:

1. The SET UNIT SPs menu

2. Scrolling to it (last screen in the SET UNIT SPs column)

3. By simply pressing the UP ARROW, DOWN ARROW, or DEFAULT keys while on the
desired field 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. The length of the password shall not be indicated. Once the
correct password has been entered (cases 1 and 2 above), the PASSWORD screen shall
show the active password level. For case 3 above, the previously selected screen shall
reappear (still in edit mode) with the cursor on the previously selected field. Once a
password has been entered, it shall remain valid for 15 minutes after the last key-press. It
shall be possible to change the passwords through pLAN. Parameters and screens that
require the MANAGER password shall not be displayed unless the MANAGER password
is active.

74 OMM WMC-3 OITS

Compressor Controller Menu Screens

Menu Matrix

Each of the two compressor controllers has the same menu screens, as shown in the following matrix.

NOTE: All relevant unit operating data and setpoint entry are available and performed on the unit controller

and there is no need to consult the individual compressor controllers. The following table is for general
information only.

VIEW STATUS SCREENS

VIEW UNIT STATUS(1)
UNIT= OFF
COMP OFF
Ev/Cn Pmps=OFF/OFF

VIEW UNIT STATUS(2)
Comp OFF
Start-Start Tmr Clr
Inhibits None
VIEW COMP (3) psi

VIEW COMP (4) oF

VIEW COMP (5) oF

VIEW COMP (7)

NOTE: Right half of matrix continued on the next page.

VIEW UNIT WATER(1)oF
In Out Delta
Evap 00.0 00.0 00.0
Cond 00.0 00.0 00.0

VIEW UNIT REFRG (2)

VIEW COMP (6)

VIEW UNIT REFRG (1)
psi oF
Sat Evap 000.0 000.0
Sat Cond 000.0 000.0

Suct Line = 000.0oF
Liquid Line = 000.0oF
Lift Press = 000.0psi

VIEW COMP (1)
State = OFF
% RLA = 000%
Evap LWT = 054.0oF

VIEW COMP (2) psi
Cond Press = 000.0
Evap Press = 000.0
Lift Press = 000.0

WMC Compressor
Oilless Design
(blank menu)

Cavity Temp=000.0°F
Invert Temp=000.0°C
Lift Temp = 00.0°F

Temp SH
Suction 000.0 00.0
Discharge 000.0 00.0

psi oF
SatEvap 000.0 000.0
SatCond 000.0 000.0

Hours = 00000 x10
Starts = 00000

VIEW EVAPORATOR
Suct SH = 000.0oF
Approach = 00.0oF

VIEW CONDENSER
Disch SH =

000.0oF
Approach = 00.0oF
Subcooling = 00.0°F

OMM WMC-3 OITS 75

SET COMP#1 SPs (1)
Demand Limit=OFF
Minimum Amps=040%
Maximum Amps=100%
SET COMP SPs (2)
StageMode =Normal
StageSequence# = 01
Max Compr ON = 01
SET COMP SPs (3)
StageDeltaT = 1.0oF
Stop-Start = 03 min
Start-Start = 40 min
SET COMP SPs (4)
Full Load = 300 sec Name
Plate RLA 085

SET COMP SPs (5)

Nom Capacity = 0100T
HotGasBypass = 30%
SET COMP SPs (6)
InterLokTmr= 010sec
UnloadTimer = 030 sec

SET COMP SPs (7)
WMC Automatic
Vane Control
(blank mask page)
SET COMP SPs (8)
MAX KW = 76.0
Lag Start = 000Sec
Step Down = 060Sec
SET COMP SPs (9)
Protocol =M-BUS MSTR
Ident Number= 001
Baud Rate = 19200
SET COMP SPs (10)
Refrg Sat Pressure
Evp Offset =+00.0 psi
Cnd Offset = +00.0psi
SET COMP SPs (11)
ELWT Offset = +0.0 oF

SET SETPOINTS

SET ALARM LMTs (1)
LowEvPrHold=33psi
LowEvPrUnld=31psi
LowEvPrStop=29psi
SET ALARM LMTs (2)
HighCondPr =140psi
HiDschT-Load=170oF
HiDschT-Stop=190oF
SET ALARM LMTs (3)
WMC Compressor
Oilless Design
(blank mask page)
SET ALARM LMTs (4)
Surge Slp Str=20oF
Surge Tmp Run=06oF
MtrCurThrshld=10%
SET ALARM LMTs (5)
Evap Freeze= 34.0°F
Cond Freeze= 34.0°F

SET PASSWORD
Enter
Password:00000
No Access Given
SET PASSWORD (2)
Tech Password
00000 00000
No Access Given

76 OMM WMC-3 OITS

BAS Interface

The MicroTech II controller is available with the optional 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.

• IM 735, LONWORKS® Communication Module Installation

• IM 736, BACnet® Communication Module Installation

• IM 743, Modbus® Communication Module Installation

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.

OMM WMC-3 OITS 77

Operation

Operator Responsibilities

It is important that the operator become familiar with the equipment and the system before attempting to
operate the chiller.

During the initial startup of the chiller, the McQuay technician will be available to answer any questions and
instruct in the proper operating procedures.

It is recommended that the operator maintain an operating log for each individual chiller unit. In addition, a
separate maintenance log should be kept of the periodic maintenance and servicing activities.

Now that you have made an investment in modern, efficient McQuay equipment, its care and operation
should be a high priority. For training information on all McQuay HVAC products, please visit us at
www.mcquay.com and click on Training or phone [phone] and ask for the Training Department.
These sessions are structured to provide basic classroom instruction and include hands-on operating and
troubleshooting exercises.

Compressor Operation

The WMC compressors are two-stage. Suction gas enters the compressor through inlet guide vanes that can
be opened and closed to control refrigerant flow as the cooling load changes. The suction gas enters the first
stage impeller, is compressed, travels through the vaned radial diffuser to the second stage impeller where
compression is completed. The gas travels to the condenser via the discharge volute, which converts any
remaining velocity pressure to static pressure.

Motor cooling is accomplished by utilizing the refrigerant effect of high-pressure refrigerant from the
condenser expanded to a gas within the compressor. The refrigerant cools heat sinks and the motor.

A five-axis magnetic bearing system supports the motor/compressor shaft, resisting radial and thrust forces.
The bearing control system uses shaft position feedback to continually adjust the bearing to keep the shaft in
the correct position. In the event of a power failure, the compressor motor acts as a generator and powers
the bearing support system during coastdown. There is also a system to gently de-levitate the shaft.

Many controls are mounted directly on the compressor where they monitor and control compressor
operation. These compressor controls are interfaced with the conventional MicroTech II controls to provide
a complete chiller control system.

Operating Limits:

Maximum standby ambient temperature, 130°F (55°C)
Minimum operating ambient temperature (standard), 35
Leaving chilled water range, 38
Maximum operating evaporator inlet fluid temperature, 66
Maximum startup evaporator inlet fluid temperature, 90
Maximum non-operating inlet fluid temperature, 100
Minimum condenser water entering temperature, 65
Minimum condenser water entering temperature, 55
Maximum condenser entering temperature, 105F (40.6C)
Maximum condenser leaving temperature, 115F (46.1C)

°F to 60°F (3°C to 15°C)

°F (2°C)

°F (19°C)

°F (32°C)

°F (38°C)
°F (18°C)
°F (12.8°C)

78 OMM WMC-3 OITS

System Water Volume

It is important to have adequate water volume in the system to provide an opportunity for the chiller to sense
a load change, adjust to the change, and stabilize. As the expected load change becomes more rapid, a
greater water volume is needed. The system water volume is the total amount of water in the evaporator, air
handling products and associated piping. If the water volume is too low, operational problems can occur
including rapid compressor cycling, rapid loading and unloading of compressors, erratic refrigerant flow in
the chiller, improper motor cooling, shortened equipment life and other undesirable consequences.

For normal comfort cooling applications, where the cooling load changes relatively slowly, we recommend a
minimum system volume of three minutes times the flow rate (gpm). For example, if the design chiller flow
rate is 300 gpm, we recommend a minimum system volume of 900 gallons (300 gpm x 3 minutes).

For process applications where the cooling load can change rapidly, additional system water volume is
needed. A process example would be a quenching tank. The load would be very stable until the hot material
is immersed in the water tank. Then, the load would increase drastically. For this type of application,
system volume may need to be increased.

Since there are many other factors that can influence performance, systems may successfully operate below
these suggestions. However, as the water volume decreases below these suggestions, the possibility of
problems increases.

Variable Speed Pumping

Variable water flow involves inversely changing the water flow through the evaporator as the load changes.
McQuay chillers are designed for this duty provided that the rate of change in water flow is slow and the
minimum and maximum flow rates for the vessel, as shown in

Figure 34 on page 80 are not exceeded.

The recommended maximum change in water flow is 10 percent of the allowable flow change per minute.
Flow is usually not reduced below 50 percent of design flow (provided vessel minimum flow rates are not
exceeded).

For example, a 150 ton chiller might have chilled water flow of 360 gpm, reduced to 50 percent, would be
180 gpm. However, the minimum flow rate is 216 gpm, so the flow change would be 360 gpm minus 216
gpm, or 144 gpm. This means that the allowable flow rate change would be 10 percent of 144 or 14.4 gpm
per minute.

OMM WMC-3 OITS 79

Pressure Drop Curves

Figure 34, Evaporator Pressure Drops

WMC Evap - Water Side Pressure Drop

90

80

70

60

50

EPD - ft

40

30

20

10

E2212-B 1 pass
E2212-B 2 pass
E2209-B 1 pass
E2209-B 2 pass
E2212-C 1 pass
E2212-C 2 pass
E2212-C 3 pass
E2209-C 1 pass
E2209-C 2 pass
E2209-C 3 pass
E2212-D 1 pass
E2212-D 2 pass
E2212-D 3 pass
E2209-D 1 pass
E2209-D 2 pass
E2209-D 3 pass

0

0 200 400 600 800 1000 1200 1400 1600 1800

EGPM - gpm

Figure 35, Condenser Pressure Drops

WMC Cond - Water Side Pressure Drop

60.0

50.0

40.0

30.0

CPD - ft

20.0

10.0

C2012-B 1 pass
C2012-B 2 pass
C2009-B 1 pass
C2009-B 2 pass
C2012-C 1 pass
C2012-C 2 pass
C2012-C 3 pass
C2009-C 1 pass
C2009-C 2 pass
C2009-C 3 pass

0.0
0 500 1000 1500 2000 2500

CGPM - gpm

80 OMM WMC-3 OITS

MicroTech II™ Control

Figure 36, Unit Control Panel

SW1, Unit Switch
SW12, Circ #1 Switch
SW22, Circ #2 Switch
Control Circuit Breaker

Unit T erminal Board

UTB1

Unit Controller

Circuit # 1 Controller

MOD1, MOD2

Circuit #1 Terminal
Board, TB1

Circuit # 2 Controller

Circuit #2 Terminal
Board, TB2

Ground

OMM WMC-3 OITS 81

Capacity Control System

The capacity of the chiller is controlled by, 1) staging the compressors on and off, 2) by adjusting
the capacity of each compressor by opening or closing the inlet vanes to control the quantity of
refrigerant entering the impeller, and 3) varying compressor speed to change capacity.

The speed control and vane control work in conjunction. As load decreases, compressor speed is
reduced as low as possible but above the point where stall might begin. If further capacity
reduction is required, the guide vanes will close to whatever position is required to match the
compressor capacity to the load.

Surge and Stall

Stall and surge are a characteristic of all centrifugal compressors. These conditions can occur at
low load conditions when the operating point moves to the left of the compressor surge line on the
performance curve.

In surge, the discharge gas alternately flows backward and forward through the impeller reversing
about every two seconds. Increased noise, vibration and heat occur and motor current varies
widely. Surge can damage a compressor. The compressors are equipped with safety features that
help prevent surge from occurring.

Another instability is stall or incipient surge, which occurs a little to the left, or before, the surge
condition. Discharge gas in the diffuser forms rotating stall pockets or cells. The compressor
sound level will change and the impeller starts to heat up. Motor current remains steady.

Condenser Water Temperature

When the ambient wet bulb temperature is lower than design, the entering condenser water
temperature can be allowed to fall, improving chiller performance.

The McQuay WMC centrifugal chiller will start and run with 55
water temperature.

Depending on local climatic conditions, using the lowest possible entering condenser water
temperature can be more costly in total system power consumed than the expected savings in
chiller power would suggest due to the excessive fan power required.

To obtain lower than 65
produce 85
must continue to operate at 100% capacity at low wet bulb temperatures. As chillers are selected
for lower kW per ton, the cooling tower fan motor power becomes a higher percentage of the peak
load chiller power. The offsets of compressor power and fan power must be examined. On the
other hand, the low condenser water temperatures can be easy and economical to achieve in mild
climates with low wet bulb temperatures.

Even with tower fan control, some form of water flow control such as tower bypass must be used.
The MicroTech II control is capable of controlling tower fans and bypass valve.

Figure 38 and Figure 39 illustrate two temperature actuated tower bypass arrangements. The “Cold
Weather” scheme provides better startup under cold ambient air temperature conditions. The check
valve may be required to prevent air at the pump inlet.

°F (29.4°C) water temperature at design ambient air temperatures, cooling tower fans

°F (18.3°C) entering condenser water temperature with a tower selected to

°F (12.8°C) entering condenser

82 OMM WMC-3 OITS

Figure 37, Tower Bypass Valve, Pressure Actuated

Figure 38, Tower Bypass, Mild Weather Operation

Figure 39, Tower Bypass, Cold Weather Operation

OMM WMC-3 OITS 83

Normal Unit Startup/Shutdown

Startup and shutdown, other than seasonal shutdowns, are considered to be normal operation and
the following procedures apply (assuming that the equipment room temperature are above
freezing). The procedures would be used for a weekend shutdown, for example.

Note that the chiller is part of an entire building heating and cooling system that are usually unique
to a particular site. For example, the chilled water loop and chilled water pump can also be used
for heating and therefore must be operational year-around. The cooling tower can be used for other
equipment besides the chiller and may have to remain functional even though the chiller is not.
The following procedures, therefore, must take the peculiarities of the entire system into account.

Shutdown

If the unit is to be secured for several days, and is already off due to lack of load, the UNIT switch
in the Unit Control Panel (and the remote Start/Stop switch, if used) should be placed in the OFF
position. If the chilled water pump and cooling tower are not required for other purposes, they too
can be turned off. If the pumps are controlled by the WMC unit controller, they will shut down
after the compressors.

If the chiller is running, the chilled water and condenser water pumps must remain on until the
compressors are stopped. This is true regardless of how the unit is turned off, whether by the local
switches or through a remote signal. The compressors go through a short shutdown sequence,
shutting guide vanes and performing other functions, before it finally stops. The pumps must
remain on during this shutdown period.

Once the compressors and pumps have stopped, no further action is required other than opening
disconnects, if so desired.

Startup

Any disconnects that were opened must be closed. The chilled water pump and cooling tower
should be turned on and flow verified. The chiller can then be started by placing the UNIT switch
(and the remote Start/Stop switch, if used) in the ON position. There is no lube warm-up period
required. The compressors go through a starting sequence and may not start immediately. Once
started, it is prudent to observe unit operation on the operator interface screen for several minutes
to check for normal functioning.

Start/Stop Switching

There are four ways to start/stop the chiller. Three are selected in SETPOINT\ MODE\SP3, the
fourth way is through panel-mounted switches:

Operator Interface Panel, (LOCAL) Home Screen 1 has AUTO and STOP buttons that are

1.
only active when the unit is in "LOCAL CONTROL". This prevents the unit from being
accidentally started or stopped when it is under control from a remote switch or BAS. When
these buttons are pressed, the unit will cycle through its normal starting or stopping sequence,
both compressors will be stopped and normal dual compressor starting procedure will be in
effect.

Remote SWITCH, Selecting SWITCH in SP3 will put the unit under the control of a remote

2.
switch that must be wired into the control. See Field Wiring Diagram, page

3.

BAS, BAS input is field-wired into a card that is factory-installed on the unit controller.

31.

84 OMM WMC-3 OITS

4. Control Panel Switches

Three On/Off switches are located in the upper left corner of the main Control Panel, which is
adjacent to the operator interface panel, and have the following function:

• UNIT shuts down the chiller through the normal shutdown cycle of unloading the

compressors.

• COMPRESSOR one switch for each compressor on the unit, executes an immediate

shutdown without the normal shutdown cycle.

• CIRCUIT BREAKER disconnects optional external power to system pumps and tower

fans.

A fourth switch located on the left outside of the Unit Control Panel and labeled
EMERGENCY STOP SWITCH
the COMPRESSOR On/Off switches.

stops the compressor immediately. It is wired in series with

Annual Unit Startup/Shutdown

Annual Shutdown

Where the chiller can be subject to freezing temperatures, the condenser and chiller must be drained
of all water. Dry air blown through the condenser will aid in forcing all water out. Removal of
condenser heads is also recommended. The condenser and evaporator are not self-draining and tubes
must be blown out. Water permitted to remain in the piping and vessels can rupture these parts if
subjected to freezing temperature.

Forced circulation of antifreeze through the water circuits is one method of avoiding freeze up.

1. Take measures to prevent the shutoff valve in the water supply line from being accidentally
turned on.

2. If a cooling tower is used, and if the water pump will be exposed to freezing temperatures, be
sure to remove the pump drain plug and leave it out so any water that can accumulate will
drain away.

3. Open the compressor disconnect switch
switches in the Unit Control Panel to the OFF position.

4. Check for corrosion and clean and paint rusted surfaces.

5. Clean and flush water tower for all units operating on a water tower.

6. Remove condenser heads at least once a year to inspect the condenser tubes and clean if
required.

. Set the manual COMPRESSOR and UNIT ON/OFF

Annual Startup

1. Check and tighten all electrical connections.

2. Replace the drain plug in the cooling tower pump if it was removed at shutdown time the previous
season.

3. Install fuses in main disconnect switch (if removed).

4. Reconnect water lines and turn on supply water. Flush condenser and check for leaks.

Maintenance

Danger

OMM WMC-3 OITS 85

Wait 10 minutes after compressor shutdown before opening any compressor access panel.

The DC link capacitors store enough energy to cause electrocution.

Pressure/Temperature Chart

HFC-134a Temperature Pressure Chart

°F PSIG °F PSIG °F PSIG °F PSIG

6 9.7 46 41.1 86 97.0 126 187.3

8 10.8 48 43.2 88 100.6 128 192.9
10 12.0 50 45.4 90 104.3 130 198.7
12 13.2 52 47.7 92 108.1 132 204.5
14 14.4 54 50.0 94 112.0 134 210.5
16 15.7 56 52.4 96 115.9 136 216.6
18 17.1 58 54.9 98 120.0 138 222.8
20 18.4 60 57.4 100 124.1 140 229.2
22 19.9 62 60.0 102 128.4 142 235.6
24 21.3 64 62.7 104 132.7 144 242.2
26 22.9 66 65.4 106 137.2 146 249.0
28 24.5 68 68.2 108 141.7 148 255.8
30 26.1 70 71.1 110 146.3 150 262.8
32 27.8 72 74.0 112 151.1 152 270.0
34 29.5 74 77.1 114 155.9 154 277.3
36 31.3 76 80.2 116 160.9 156 284.7
38 33.1 78 83.4 118 166.0 158 292.2
40 35.0 80 86.7 120 171.1 160 299.9
42 37.0 82 90.0 122 176.4 162 307.8
44 39.0 84 93.5 124 181.8 164 315.8

86 OMM WMC-3 OITS

Routine Maintenance

Refrigerant Cycle

Maintenance of the refrigerant cycle includes maintaining a log of the operating conditions, and checking
that the unit has the proper refrigerant charge.

At every inspection, the suction, and discharge pressures should be noted and recorded, as well as condenser
and chiller water temperatures.

The suction line temperature at the compressor should be taken at least once a month. Subtracting the
saturated temperature equivalent of the suction pressure from this will give the suction superheat. Extreme
changes in subcooling and/or superheat over a period of time will indicate losses of refrigerant or possible
deterioration or malfunction of the expansion valve. The evaporator operates at 0 to 1 degree F (0.5 degree
C) of superheat through most of the load range. The refrigerant used for compressor cooling dumps at the
compressor suction, where the suction temperature sensor is located. This results in a warming of the
suction gas and superheat readings of 4 to 5 degrees F (2 to 3 degrees C).

The discharge superheat should be between 16 and 18 degrees F (9 to 10 degrees C), and remains fairly
constant through most of the load range.

Liquid subcooling is in the range of 8 to 9 degrees F (4.5 to 5.0 degrees C).
The MicroTech II interface panel can display all superheat and subcooling temperatures.

Electrical System

Maintenance of the electrical system involves the general requirement of keeping contacts clean and
connections tight and checking on specific items as follows:

1. The compressor current draw should be checked and compared to nameplate RLA value. Normally, the
actual current will be lower, since the nameplate rating represents full load operation. Also check all
pump and fan motor amperages, and compare with nameplate ratings.

2. At least once a quarter, all equipment protection controls, except compressor overloads, should be made
to operate and their operating points checked. A control can shift its operating point as it ages, and this
must be detected so the controls can be adjusted or replaced. Pump interlocks and flow switches should
be checked to be sure they interrupt the control circuit when tripped.

Cleaning and Preserving

A common cause of service calls and equipment malfunction is dirt. This can be prevented with normal
maintenance. The system components most subject to dirt are:

1. Permanent or cleanable filters in the air handling equipment must be cleaned in accordance with the
manufacturer’s instructions; throwaway filters should be replaced. The frequency of this service will
vary with each installation.

2. Remove and clean strainers in the chilled water system and condenser water system at every inspection.

Water Treatment

Make sure tower blowdown or bleed-off is operating. Set up and use a good maintenance program to
prevent “liming up” of both tower and condenser. It should be recognized that atmospheric air contains
many contaminants that increase the need for proper water treatment. The use of untreated water can result
in corrosion, erosion, sliming, scaling or algae formation. It is recommended that the service of a reliable
water treatment company be used. McQuay International assumes no responsibility for the results of
untreated or improperly treated water.

OMM WMC-3 OITS 87

Repair of System

Pressure Relief Valve Replacement

Current condenser designs use two relief valves separated by a three-way shutoff valve (one set). This
three-way valve allows either relief valve to be shut off, but at no time can both be shut off. In the event
one of the relief valves are leaking in the two valve set, these procedures must be followed:

• If the valve closest to the valve stem is leaking, back seat the three-way valve all the way, closing the

port to the leaking pressure relief valve. Remove and replace the faulty relief valve. The three-way
shutoff valve must remain either fully back seated or fully forward to normal operation. If the relief
valve farthest from the valve stem is leaking, front seat the three-way valve and replace the relief
valve as stated above.

• The refrigerant must be pumped down into the condenser before the evaporator relief valve can be

removed.

Pumping Down

If it becomes necessary to pump the system down, extreme care must be used to avoid damage to the
evaporator from freezing. Always make sure that full water flow is maintained through the chiller and
condenser while pumping down. To pump the system down, close all liquid line valves. With all liquid
line valves closed and water flowing, start the compressor. Set the MicroTech II control to the manual
load. The vanes must be open while pumping down to avoid a surge or other damaging condition. Pump
the unit down until the MicroTech II controller cuts out at approximately 20 psig. It is possible that the
unit might experience a mild surge condition prior to cutout. If this should occur, immediately shut off the
compressor. Use a portable condensing unit to complete the pump down, condense the refrigerant, and
pump it into the condenser or pumpout vessel using approved procedures.

Pressure Testing

No pressure testing is necessary unless some damage was incurred during shipment. Damage can be
determined by a visual inspection of the exterior piping, checking that no breakage occurred or fittings
loosened. Service gauges should show a positive pressure. If no pressure is evident on the gauges, a leak
may have occurred, discharging the entire refrigerant charge. In this case, the unit must be leak tested to
determine the location of the leak.

Leak Testing

In the case of loss of the entire refrigerant charge, the unit must be checked for leaks prior to charging the
complete system. This can be done by charging enough refrigerant into the system to build the pressure up
to approximately 10 psig (69 kPa) and adding sufficient dry nitrogen to bring the pressure up to a
maximum of 125 psig (860 kPa). Leak test with an electronic leak detector. Halide leak detectors do not
function with R-134a. Water flow through the vessels must be maintained anytime refrigerant is added or
removed from the system.

WARNING

Do not use oxygen or a mixture of a refrigerant and air to build up pressure

as an explosion can occur causing serious personal injury.

If any leaks are found in welded or brazed joints, or it is necessary to replace a gasket, relieve the test
pressure in the system before proceeding. Brazing is required for copper joints.

After making any necessary repair, the system must be evacuated as described in the following section.

88 OMM WMC-3 OITS

Evacuation

After it has been determined that there are no refrigerant leaks, the system must be evacuated using a
vacuum pump with a capacity that will reduce the vacuum to

at least 1000 microns of mercury.

A mercury manometer, or an electronic or other type of micron gauge, must be connected at the farthest
point from the vacuum pump. For readings below 1000 microns, an electronic or other micron gauge must
be used.

The triple evacuation method is recommended and is particularly helpful if the vacuum pump is unable to
obtain the desired 1 millimeter of vacuum. The system is first evacuated to approximately 29 inches of
mercury. Dry nitrogen is then added to the system to bring the pressure up to zero pounds.

Then the system is once again evacuated to approximately 29 inches of mercury. This is repeated three
times. The first pulldown will remove about 90% of the noncondensables, the second about 90% of that
remaining from the first pulldown and, after the third, only 1/10-1% noncondensables will remain.

Charging the System

1. McQuay water chillers are leak tested at the factory and shipped with the correct charge of refrigerant as
indicated on the unit nameplate. In the event the refrigerant charge was lost due to shipping damage, the
system should be charged as follows after first repairing the leaks and evacuating the system.

2. Connect the refrigerant drum to the gauge port on the liquid line shutoff valve and purge the charging
line between the refrigerant cylinder and the valve. Then open the valve to the mid-position.

3. Turn on both the cooling tower water pump and chilled water pump and allow water to circulate through
the condenser and the chiller. (It may be necessary to manually close the condenser pump starter.)

4. If the system is under a vacuum, stand the refrigerant drum with the connection up, and open the drum
and break the vacuum with refrigerant gas to a saturated pressure above freezing.

5. With a system gas pressure higher than the equivalent of a freezing temperature, invert the charging
cylinder and elevate the drum above the condenser. With the drum in this position, valves open, water
pumps operating, liquid refrigerant will flow into the condenser. Approximately 75% of the total
requirement estimated for the unit can be charged in this manner.

6. After 75% of the required charge has entered the condenser, reconnect the refrigerant drum and charging
line to the service valve on the bottom of the evaporator. Again purge the connecting line, stand the
drum with the connection up, and place the service valve in the open position.

IMPORTANT: At this point, the charging procedure should be interrupted and prestart checks
made before attempting to complete refrigerant charge. The compressor must not be started at
this time. (Preliminary check must first be completed.)

NOTE: It is of utmost importance that all local, national, and international regulations concerning
the handling and emission of refrigerants are observed.

OMM WMC-3 OITS 89

Maintenance Schedule

I. Compressor

A. Performance Evaluation (Log & Analysis) * O
B. Motor

• Ampere Balance (within 10%)

• Terminal Check (tight connections, porcelain clean)

• Motor Cooling (check temperature)
C. Vane Operation

• Compressor Loads:
Operate Manual Switch X
Record Motor Amps X

• Compressor Unloads:
Operate manual Switch X
Record Motor Amps X

• Vanes Will Hold (place manual switch in "hold")
Observe Water Temp and Record Amps X
D. Internal Compressor Check X

II. Controls

A. Operating Controls

• Check Settings and Operation

• Check Vane Control Setting and Operation

• Verify Motor Load Limit Control

• Verify Load Balance Operation
B. Protective Controls

• Test Operation of:
Alarm Relay X
Pump Interlocks X

III. Condenser

A. Performance Evaluation O
B. Test Water Quality X
C. Clean Condenser Tubes X
D. Eddy current Test - Tube Wall Thickness X
E. Seasonal Protection X

IV. Evaporator

A. Performance Evaluation (Log Conditions And Analysis) O
B. Test Water Quality X
C. Clean Evaporator Tubes (as required) X
D. Eddy current Test - Tube Wall thickness (as required) X
E. Seasonal Protection X

V. Expansion Valve

A. Performance Evaluation (Superheat Control) X

VI. Compressor - Chiller Unit

A. Performance Evaluation O
B. Leak Test:

• Compressor Fittings and Terminal

• Piping Fittings

• Vessel Relief Valves
C. Vibration Isolation Test X
D. General Appearance:

• Paint and Insulation

VII. Electrical

A. Capacitors, Replace every 5 years from startup, include bus

bar. Consult McQuay for parts and instructions.

Key: O = Performed by in-house personnel X = Performed by McQuay Service personnel

X
X
X

X
X
X
X

X
X
X

X

90 OMM WMC-3 OITS

Service Programs

It is important that an air conditioning system receive adequate maintenance if the full equipment life and full
system benefits are to be realized.

Maintenance should be an ongoing program from the time the system is initially started. A full inspection
should be made after 3 to 4 weeks of normal operation on a new installation, and on a regular basis thereafter.

McQuay offers a variety of maintenance services through the local McQuay service office, its worldwide
service organization, and can tailor these services to suit the needs of the building owner. Most popular
among these services is the McQuay Comprehensive Maintenance Contract.

For further information concerning the many services available, contact your local McQuay service office.

Operator Schools

Training courses for Centrifugal Maintenance and Operation are held through the year at the McQuay
Training Center in Staunton, Virginia. The school duration is three and one-half days and includes
instruction on basic refrigeration, MicroTech controllers, enhancing chiller efficiency and reliability,
MicroTech troubleshooting, system components, and other related subjects. Further information can be
found on

www.mcquay.com or call McQuay at 540-248-0711 and ask for the Training Department.

W arranty Statement

Limited Warranty

Consult your local McQuay Representative for warranty details. Refer to Form 933-43285Y. To find your
local McQuay Representative, go to www.mcquay.com.

OMM WMC-3 OITS 91

This document contains the most current product information as of this printing. For the most up-to­date product information, please go to www.mcquay.com.

[phone] • www.mcquay.com OMM WMC-3 OTIS (4/06)