Trane UCM-CLD, RLC-SVU02F-E4 Owner's Manual

UCM-CLD
Chiller Control System

Owner
Manual

RLC-SVU02F-E4

© 2009 Trane

General information

RLC-SVU02F-E4

Foreword

These instructions are given as a
guide to the operation of the
controller(s) mounted on Trane
RTAD/RTWB/RTRA chillers. They do
not contain full service procedures
necessary for the continued
successful operation of this
equipment. The services of a qualified
technician should be employed
through the medium of a
maintenance contract with a
reputable service company. Read
this manual thoroughly before unit
start-up.

Warnings and cautions

Warnings and Cautions appear at
appropriate sections throughout this
manual. Your personal safety and the
proper operation of this machine
require that you follow them
carefully. The constructor assumes no
liability for installations or servicing
performed by unqualified personnel.

WARNING! : Indicates a potentially
hazardous situation which, if not
avoided, could result in death or
serious injury.

CAUTION! : Indicates a potentially
hazardous situation which, if not
avoided, may result in minor or
moderate injury. It may also be
used to alert against unsafe
practices or for equipment or
property-damage-only accidents.

Safety recommendations

To avoid death, injury, equipment or
property damage, the following
recommendations should be
observed during maintenance and
service visits:

1. The maximum allowable pressures
for system leak testing on low and
high pressure side are given in the
chapter "Installation". Always provide
a pressure regulator.

2. Disconnect the main power supply
before any servicing on the unit.

3. Service work on the refrigeration
system and the electrical system

should be carried out only by
qualified and experienced personnel.

Reception

On arrival, inspect the unit before
signing the delivery note.

Reception in France only:

In case of visible damage: The
consignee (or the site representative)
must specify any damage on the
delivery note, legibly sign and date
the delivery note, and the truck driver
must countersign it. The consignee
(or the site representative) must
notify Trane Epinal Operations ­Claims team and send a copy of the
delivery note. The customer (or the
site representative) should send a
registered letter to the last carrier
within 3 days of delivery.
Note: for deliveries in France, even
concealed damage must be looked
for at deli

very and immediately

treated as visible damage.

Reception in all countries except
France:

In case of concealed damage: The
consignee (or the site representative)
must send a registered letter to the
last carrier within 7 days of delivery,
claiming for the described damage.
A copy of this letter must be sent to
Trane Epinal Operations - Claims
team.

Warranty

Warranty is based on the general
terms and conditions of the
manufacturer. The warranty is void if
the equipment is repaired or
modified without the written
approval of the manufacturer, if the
operating limits are exceeded or if
the control system or the electrical
wiring is modified. Damage due to
misuse, lack of maintenance or
failure to comply with the
manufacturer's instructions or
recommendations is not covered by
the warranty obligation. If the user
does not conform to the rules of this
manual, it may entail cancellation of
warranty and liabilities by the
manufacturer.

Maintenance contract

It is strongly recommended that you
sign a maintenance contract with
your local Service Agency. This
contract provides regular
maintenance of your installation by a
specialist in our equipment. Regular
maintenance ensures that any
malfunction is detected and corrected
in good time and minimizes the
possibility that serious damage will
occur. Finally, regular maintenance
ensures the maximum operating life
of your equipment. We would remind
you that failure to respect these
installation and maintenance
instructions may result in immediate
cancellation of the warranty.

Training

To assist you in obtaining the best
use of it and maintaining it in perfect
operating condition over a long
period of time, the manufacturer has
at your disposal a refrigeration and
air conditioning service school. The
principal aim of this is to give
operators and technicians a better
knowledge of the equipment they are
using, or that is under their charge.
Emphasis is particularly given to the
importance of periodic checks on the
unit operating parameters as well as
on preventive maintenance, which
reduces the cost of owning the unit
by avoiding serious and costly
breakdown.

Contents

3RLC-SVU02F-E4

General Information 2

Principles of operation
of the UCM-CLD module 4

General Information 4
Operator’s Interface 5
Operational Features 9

Diagnostics 16

Diagnostics 16
Default Description 17

Controller for hydraulic module/
free cooling / heat recovery / RTWB
heat pump applications 22

Hydraulic module control 23

Control logic 23
Module and outputs/inputs 24
Hydraulic module option 25
Data display menu 26
Configuration menu 27
Alarms messages - hydraulic module application 30
Mask and menu chart 31

Free cooling application 32

Heat recovery application 38

RTWB heat pump application 40

Principles of Operation of the
Module UCM-CLD

RLC-SVU02F-E44

General Information

This UCM-CLD chiller control is
composed of eight electronic
modules, which each have their
own 115V or 24V power supply and
communicate with each other via a
serial link. The names of the
modules are linked to their
functions.

Figure 1 : Operator’s interface

Compressor

Report

Refrigerant

Report

Chiller
Report

Custom

Report

Select Report Group

Diagnostics

Service

Tests

Service

Settings

Operator
Settings

Alarm

AutoEnterPrevious

StopCancelNext

Select Setting Group

ADAPTIVE CONTROL™

Module Functions

MCSP (Motor Compressor Start and Protection)

CPM (Chiller Protection and Management) Safety, protection, and control of the chiller
EXV (Electronic Expansion Valves) Control of both electronic expansion valves
CSR (Communication and Setpoint Reset) ,

Local CLD (Local Clear Language Display) Operator interface located in the front panel of the unit
Remote CLD (Remote Clear Language Display)

TCI IV, COM 3 (Tracer Communication Interface 4, COM 3)

Safety, protection, and control of the helical-rotary compressor and
its components

Control of the serial communication, unit external setpoints and
ice-making mode (optional module)

Operator interface located up to 1500m from the unit, able to
communicate with up to four units of the same type (optional module)

TCI IV, IPCB (Tracer Communication Interface 4, Inter Processor
Communication Buffer)

Protection of the internal communication bus in the unit from external
interferences (optional factory-mounted module, compulsory when
using a Remote CLD)

Interface between the control of the unit and a Building Management
System using Trane COMM 3 serial link

Principles of Operation of the
Module UCM-CLD

5RLC-SVU02F-E4

Operator's Interface

Digital Display

The display of control regulation and
operating parameters, diagnostics,
and error messages is a 2-line, 40­character, liquid-crystal display. The
display has a LED backlight to read
in low-light conditions and to warm
up the display under low ambient
temperatures. When powering up
the system, the display is not lit and
the message [SELF-TEST IN
PROGRESS] is displayed. The screen
can display error codes, settings of
various setpoints, specified
temperature and pressure values,
and the status of operating
parameters and options.

Keyboard

A 16-key touchpad allows both
navigation between menus and the
modification of parameters and
setpoints. The keys are divided into
two groups:

Individual Menu Keys Control Keys

Chiller Report Menu + key
Custom Report Menu

- key

Refrigerant Menu Previous key
Compressor Menu Next key
Operator Settings Menu Enter key
Service Settings Menu* Cancel key
Service Test Menu* Auto key
Diagnostics Menu Stop key

* Levels 2 and 3 of the Service Settings Menu and the Service Test Menu are protected by a

password and are reserved for Trane Service Engineers.

Figure 2 : Control panel mounted on a model RTWA unit

Principles of Operation of the
Module UCM-CLD

RLC-SVU02F-E46

Control Key Functions
[+] key If the information displayed

is read-only, pressing this key will
add it to the operator's menu. If the
information can be modified,
pressing this key will increase the
value without exceeding the
maximum possible value.

[-] key If the information displayed
is read-only, pressing this key will
remove it from the operator's menu.
If the information can be modified,
pressing this key will decrease the
value without exceeding the
minimum possible value.

[Previous] key Pressing this key
allows the operator to scroll up to
the previous information in the
current menu. Each menu is
looped, making it possible to scroll
from the first item in the menu to
the last item.

[Next] key Pressing this key allows
the operator to scroll down to the
next information in the current
menu. Each menu is looped, making
it possible to scroll from the last item
in the menu to the first item.

[Enter] key Pressing this key allows
the operator to validate a value after
modification.

[Cancel] keyThis key should be
pressed if a modified setting should
not be saved.

[Auto key] Pressing this key allows
the unit to be in Auto mode if it was
previously placed in Stop mode
with the [Stop] key. The unit cannot
be forced into Auto mode if an
external contact or the serial link
has stopped it. When the unit is
stopped by the remote interface
(Remote CLD), the local mode order
has priority.

[Stop] key Pressing this key allows
the unit to be in Stop mode. In
every case, and whatever the origin
(except a local stop), the stop order
and stop status have priority over a
run order. The stop generated is a
soft stop - the unit unloads before
stopping.

Whether a [Stop] or [Auto]
command will be accepted and
stored is based on the following
hierarchy:

1. Local Stop will always replace
Local Auto, Remote Auto, and
Remote Stop.

2. Local Auto will always replace
Local Stop, Remote Auto, and
Remote Stop.

3. Remote Stop will always replace
Local Auto and Remote Auto. It
will not replace Local Stop.

4. Remote Auto will always replace
Local Auto and Remote Stop. It
will not replace Local Stop.

Pressing the [Stop] key twice within
five seconds will result in an
Emergency Stop. The chiller will not
unload.

Principles of Operation of
the Module UCM-CLD

7RLC-SVU02F-E4

Parameters and setpoints within each menu

Menu Parameters/setpoints Range

Minimum/Maximum

Chiller Report Menu Active Chilled Water Setpoint

Evaporator Entering/ Leaving Chilled Water Temperature
Condenser Entering / Leaving Chilled Water Temperature
Active Ice-Storing Setpoint
Active Hot Water Setpoint
Entering/Leaving Hot Water Temperature
Current Active Setpoint limits -17.8°/18.3°C
Evaporator/Condenser Waterflow
Ambient Air Temperature

Sources of setpoints (Tracer, local CLD, external)
Custom Report Menu Custom-built by the operator (Can contain up to 20 settings)
Refrigerant Report Menu Condenser/Evaporator Refrigerant Pressures

Refrigerant Temperature in Condenser

Refrigerant Temperature in Evaporator
Compressor Report Menu Compressor Status

Time and Start Counters

Amps (% RLA)

Oil Temperature (GP compressor only)
Operator Settings Menu Setpoint Source

External Chilled Water Setpoint

External Hot Water Setpoint

Chilled Water Pump Operation

Chilled Water Pump Off Delay 1 min/30 min

Ice Machine Control*

Panel Ice Termination Setpoint -6.6°/-0.5°C

Low Ambient Lockout

Low Ambient Lockout Setpoint -28.8°/15.5°C

Front Panel Current Limit Setpoint 40%/120%

Front Panel Hot Water Setpoint 25°/60°C

Front Panel Chilled Water Setpoint -17.8°/18.3°C

Design Delta Temperature Setpoint 2.2°/16.6°C

External Current Limit Setpoint

Differential to Start Setpoint 1.1°/16.6°C

Chilled Water Reset Type

Type Reset Ratio

Type Start Reset Setpoint

Type Max Reset Setpoint 0.0°/11.1°C

Principles of Operation of
the Module UCM-CLD

RLC-SVU02F-E48

Service Settings Menu** LEVEL ONE-Information adjusted by customer

Unit Line Voltage
Over/Undervoltage Protection
Restart Inhibit Time 30/120 sec
Balanced Compressor Starts and Hours
Display Language and Units
Programmable Relay Set-up 1/12
External Circuit Lockout

LEVEL TWO- Information adjusted by Service Engineer

Address of Serial Link 0/64
Display Lock Feature
Leaving Water Temperature Setpoint
Low Refrigerant Temperature Cutout Setpoint
Low Water Temperature EXV Air Compressor
Condenser Limit Setpoint 60/120%
Phase Unbalance Protection
Phase Reversal Protection
Superheat Setpoint 2.2°/11.1°C
EXV Control Response Circuit 1 2/200
EXV Control Response Circuit 2 2/200
Leaving Water Temperature Control Response Setpoint
Fan Control Deadband bias Circuit 1 -50/50
Fan Control Deadband bias Circuit 2 -50/50

LEVEL THREE-Configuration/Protection Information

Compressor Model Number Prefix
Number of Compressors
Oil Loss Differential Setpoint
Compressor A Ton
Compressor B Ton
Compressor C Ton
Compressor D Ton
Fan Control
Variable Speed Fan Circuit 1
Variable Speed Fan Circuit 2
Number of Fans Circuit 1
Number of Fans Circuit 2
Reduced Inrush Starting
Current Overload Compressor A
Current Overload Compressor B
Current Overload Compressor C
Current Overload Compressor D
Low Ambient Unit Half Air Flow Fan
Low Ambient Unit Two-Speed Motor
Night Noise Setback
Number of EXV Circuit 1
Number of EXV Circuit 2
Refrigerant Type

Service Tests Menu Perform Expansion Valve Test

Perform Circuit locking or Pump-out Test
Perform Compressor Test

Diagnostics Menu Current Diagnostics

History of Diagnostics
Manual Reset of Diagnostics
Erase History of Diagnostics

* Option
** This menu has three access levels. The control has a display lock feature that can be locked at request after level one.

Principles of Operation of
the Module UCM-CLD

9RLC-SVU02F-E4

Operational features

Entering evaporator water
temperature

When one or both compressors are
running, the UCM continually
monitors and compares the
entering and leaving evaporator­water temperatures. If the
temperature of the entering water
drops more than 1°C below the
leaving water temperature for more
than
55°C- seconds, the UCM uses this to
indicate a loss of water flow
through the evaporator. This will
shut down that circuit's compressor
and will display MMR diagnostic.

Current Limit Setpoint (CLS)

The current limit setpoints for the
system are entered through the
Clear Language Display menus. The
current limit Setpoint for each
compressor is shown in Table 1.

Table 1 – Compressor current limit

Setpoint versus Chiller current
limit Setpoint

System

CLS One Two
120% 120 120
100 % 120 100

80% 120 80

60% 120 60

40% 80 40

Based upon current levels received
at the UCM, the compressor slide
valve is modulated to prevent the
actual chiller current from
exceeding the CLS.

When a compressor is turned off,
the CLS for the remaining running
compressor shall be reset upward
immediately. When a compressor is
added, the CLS for the running
compressor shall be ramped
downward at a rate not less than
10% RLA per minute to the new
Setpoint.

Numbers of compressor in

operation

Electronic expansion valve
(EXV) test

This test can be performed only when
the “Stop“ key has been pressed. It
will confirm proper operation of the
electronic expansion valve and the
EXV module.

After the test has been initiated at
the Clear Language Display, the
UCM will:

1. Overdrive the EXV closed
(25 seconds)

2. Overdrive the EXV open
(25 seconds)

3. Overdrive the EXV closed
(25 seconds)

4. Reset the display to disable and
end the test

The EXV produces an audible
clicking sound when it is driven
against its end stops. Step 1 drives
the EXV to its closed position,
during which time service personnel
can move from the CLD to the EXV.

Note: A tool may be needed to aid
in hearing the clicking of the EXV,
such as a screwdriver held between
the EXV and the ear.

Current overload protection

The UCM continually monitors
compressor current to provide unit
protection in the event of an
overcurrent or locked-rotor
condition. Protection is based on
the phase with the highest current
and, if limits are exceeded, the UCM
will shut down the compressor and
will display an MMR diagnostic.

Leaving chilled-water temperature
control

If the Auto key is pressed and a
remote chilled-water Setpoint has
been communicated, the UCM will
control to that Setpoint. Otherwise,
it will control to the front-panel
Setpoint. Control is accomplished
both by staging compressors and
by modulating the slide valves on
each compressor.

Upon start-up, if the leaving chilled­water temperature is dropping 0.8°C
per minute or faster, the chiller will
not load further.

Principles of Operation of
the Module UCM-CLD

RLC-SVU02F-E410

Chilled-Water Reset (CWR)

As an option, the UCM will reset the
chilled-water temperature setpoint,
based on either the return water
temperature or the outdoor air
temperature. The CSR module is
necessary to perform CWR.

The following are selectable:
One of four reset types, from top to

bottom in order of reset:
no CWR
RETURN WATER TEMPERATURE

RESET
ZONE TEMPERATURE RESET
OUTDOOR AIR TEMPERATURE

RESET

Leaving-water temperature cutout

This temperature cutout provides
protection against freezing caused
by low leaving-water temperature.
The setpoint is both factory-set and
adjustable from the Service Setting
Menu. Temperatures below the
setpoint will cause the UCM to
accelerate reduction of chiller
capacity, even to the point of
compressor shutdown. A non­latching diagnostic will be
generated if the LWT is below the
cutout for more than 16°C-seconds.

There must be a minimum of 2.7°C
between the cutout temperature
and both the front-panel and active­chilled-water setpoints. The Clear
Language Display will not permit
setting of either the front-panel or
active-chilled-water temperatures
less than 2.7°C above the cutout
temperature. The second line will
state:

Limited by Cutout Setpoint (+)

to change

If the leaving-water temperature
cutout is set upward, the Clear
Language Display will maintain the

2.7°C minimum and will
automatically raise the settings on
the front-panel and active-chilled­water setpoints, if necessary.

If the front-panel or active-chilled­water setpoints were adjusted, the
display will show the following
when the “enter“ key is pressed:

FRONT PANEL CHILLED WATER

SETPOINT HAS BEEN

INCREMENTED DUE TO CUTOUT

SETPOINT CHANGE

If the leaving-water temperature
drops below the cutout setpoint
while the compressors are de­energized, it will produce an IFW
diagnostic. If the leaving-water
temperature drops below the cutout
setpoint while the compressors are
energized for 16°C-seconds, the unit
will shut down on an MAR
diagnostic.

Principles of Operation of
the Module UCM-CLD

11RLC-SVU02F-E4

Low refrigerant temperature cutout

Both circuits are protected from a
saturated-evaporator refrigerant
temperature that goes below this
setting. The cutout Setpoint must be
at a minimum of 8°C lower than the
front panel or active chilled-water
setpoints. See Table 2 for proper
settings.

There must be a minimum of 8°C
between the cutout temperature
and active chilled-water setpoints.
The Clear Language Display will not
permit setting of the chilled-water
temperature less than 8°C above
this cutout temperature, and the
display will flash the last valid
temperature.

If the leaving-water temperature
cutout is set upward, the Clear
Language Display will maintain the
8°C minimum and will raise the
settings of the chilled-water
setpoints, if necessary.

If the chilled-water setpoints were
adjusted, the display will show the
following when the “Enter“ key is
pressed:

FRONT PANEL CHILLED WATER

SETPOINT HAS BEEN

INCREMENTED DUE TO CUTOUT

SETPOINT CHANGE

If the saturated-evaporator
refrigerant temperature for a circuit
drops below this Setpoint for longer
than 16°C-seconds, the circuit will
be shut down and a CMR diagnostic
will be displayed.

Table 2 – Leaving fluid temperature setpoints

°C °C °C % °C

5 1.5 -3.9 0 0
4 1 -4.4 10 -4
3 0 -5.4 13 -5
2-1 -6.416-7
1-2 -7.418-8
0-3 -8.420-9

-1 -4 -9.4 22 -10

-2 -5 -10.4 24 -11

-3 -6 -11.4 26 -13

-4 -7 -12.4 27 -13

-5 -8 -13.4 29 -15

-6 -9 -14.4 31 -16

-7 -10 -15.4 32 -17

-8 -11 -16.4 33 -18

-9 -12 -17.4 34 -19

-10 -13 -18.4 36 -20

-11 -14 -19.4 36 -20

-12 -15 -20.4 37 -21

Leaving

chilled-water

temperature

Leaving-water

temperature

cutout

Low refrigerant

temperature

cutout

Recommended

%EG

Solution

freeze

point

Principles of Operation of
the Module UCM-CLD

RLC-SVU02F-E412

Balanced compressor starts
and hours

This feature is enabled/disabled in
balanced starts and hours (service
setting menu). When enabled, the
UCM will start the compressor with
the fewest starts and stop the
compressor with the greatest number
of operating hours, as determined by
the “compressor starts“ accumulator
and the “compressor hours“
accumulator. This will tend to balance
out hours and starts equally over both
compressors.

Phase imbalance protection
The Clear Language Display

monitors the current in each phase
and calculates the percentage of
imbalance as follows:

% imbalance = (Ix - I average)

I average
I average = (I1 + I2 + I3) / 3
Ix = phase with greatest difference

from I average (without regard
to sign).

If phase-unbalanced protection
(service setting menu) is enabled
and the average three-phase current
is greater than 80% RLA, and the
percent of imbalance is calculated
to exceed 15%, the UCM will shut
down the compressor and display a
CMR diagnostic.

Reverse rotation protection

The Clear Language Display
monitors incoming current during
start-up and will shut down the
compressor within one second if
phase reversal is detected.

CCAAUUTTIIOONN

Phase relationship during
installation of unit power must be
carefully controlled to ensure
compressor protection against
reversed rotation.

Oil failure protection

The logic of the UCM uses a
comparison of the entering oil
temperature at the compressor, to
the saturated-condenser
temperature, to determine if there is
an oil line restriction.

The differential between the
entering-oil and the saturated­condenser temperatures is referred
to as the “oil loss differential
setpoint“ in the service settings
menu.

If the entering oil temperature drops
2°C below the saturated-condenser
temperature for more than
30 minutes, the circuit will shut
down on a CMR diagnostic. The
diagnostic will be presented as:

OIL SYSTEM FAULT - CKT X

DIP switch settings
Compressor overload DIP switches.

IPC address

The IPC address sets the address for Inter-Processor Communications of the
Clear Language Display modules. The following are the IPC DIP switch
settings for the modules.

Module

IPC DIP A20-1 A20-2 A52 A9

Switch SW1 SW2 SW1 SW2 SW1 SW1

1 OFF Based OFF Based OFF OFF
2 OFF On OFF On OFF OFF
3 Motor Motor
4 RLA RLA
5

Principles of Operation of
the Module UCM-CLD

13RLC-SVU02F-E4

2-10 V (dc)/4-20 mA input for External
Chilled-Water Setpoint (CWS) or
Current limit Setpoint (CLS)

When either external CWS or
external CLS is used on the optional
module A9, DIP switch SW1
positions 1 and/or 2 must be set to
accommodate the type of of signal
source the customer has chosen,
either 2-10 V (dc) or 4-20 mA.
Position SW1-1 sets 2-10 V (dc)/4­20 mA for external CLS. The “OFF“
setting configures the external input
for 2-10 V (dc)/4-20 mA for external
CLS. The “OFF“ setting configures
the external input for 2-10V (dc), the
“ON“ setting configures the
external input for 4-20 mA.

Leaving Condenser-Water
Temperature control option ­Model RTWB

If the machine is delivered with the
LCWT control option (digit 49
position 3), the DIP switch on the
module A9 must be set at position
“ON.“ This option controls the
condenser (CDS) leaving-water
temperature (LCWT) based on a Hot
Water Temperature setpoint (HWSP).

Mechanical control settings

The settings for the High Pressure switch are shown below:

Pressure Switch Approval Close Open
B51 PED 19-20 bar 22-23 bar
High Pressure Czech republic

Poland
B23 PED 1.5 bar 0.5 bar
Low Pressure Czech republic

Poland

-4°C<LWTE<+15°C
B23 PED 1.2 bar 0.2 bar
Low Pressure Czech republic

Poland

-12°C<LWTE<-4°C

Figure 3 - Water Temperature Sensor Installation - Model RTWB

Compression

Fitting

Clamping Nut

Fitting Body

1/2" NPT x 1-1/2" Large Coupling

Limitations

In the heating mode, the chiller is
not able to provide chilled water for
a process. The leaving chilled-water
temperature is not controlled. The
UCM will only take care of safeties
(water flow and freezing).

The option will provide contact to
start/stop the evaporator and the
condenser pumps. Any other devices
such as valves (2 ways/3 ways), heat
exchangers, variable-volume pumps,
or other equipment will have to be
controlled by another system.

Condenser Water Temperature
Sensors - RTAD Total and Partial
Heat Recovery

UCM-CLD will not display leaving
and entering water temperature
above 70.1°C, whereas on Total Heat
Recovery units, the temperature on
the additional controller could be
higher. These conditions would
appear in cooling mode only. This is
not harmful to the operation of the
chiller.

Principles of Operation of
the Module UCM-CLD

RLC-SVU02F-E414

Hot-Water Mode Control
Module - Option Model
RTWB

Scope of Supply

The following parts will be installed
in the control panel of the unit:

• One Additional Board A70 with
display

• One CDS LWT sensor + immersion
well to be installed by the customer

The sensor will be connected to
terminals B3 and GND on terminal
block J2 of the A70 module.

Sequence of Operation

• Cooling Mode

The unit will operate as a standard
chiller (i.e., the chiller controls the
leaving chilled-water temperature).
The condenser pump will be driven
by the UCM relay. The chiller uses
the cooling setpoint defined in the
A70 Module.

• Heating Mode

In the heating mode, the chiller will
control the condenser leaving-water
temperature. The temperature sensor
connected to the A70 Module should
be located in the condenser leaving­water connection downstream from
the condenser. The control is done by
loading or unloading the chiller. To
load or unload the chiller, a chilled­water setpoint reset is applied (i.e.,
setpoint decrease = load; setpoint
increase = unload). The condenser
pump is always in operation. The
evaporator pump is still controlled by
the UCM and is always in operation.
The chiller uses the heating setpoint
defined in the A70 Module.

The chiller will be stopped if the
condenser leaving-water
temperature is greater than the
setpoint + the “differential to stop”.
The chiller will start if the condenser
leaving-water temperature is lower
than the setpoint - the “differential
to start”.

• Sensor Failure
In the heating mode, and if the CDS

leaving-water temperature sensor
fails, the chiller is stopped and the
alarm relay of the A70 Module is
energized. The chiller can operate in
the cooling mode if the CDS
leaving-water temperature sensor
has failed.

A70 Module and UCM interaction
Chilled-Water setpoint: The A70

Module drives the chilled-water
setpoint using a linear signal from
an Analog Output of the A70
Module to the external chilled-water
setpoint input of the UCM.

Chiller Enable/Disable: The A70
Module drives the chiller (on or off)
using a dry contact from the A70
Module to the external start/stop
input of the UCM.

CDS pump relay: The A70 Module
drives the condenser pump relay.

In heating mode, the chiller controls
the condenser leaving-water
temperature. The A70 Heat Pump
Module sends an external chilled­water setpoint to the UCM. This
analog signal (factory set at 4­20mA) is constantly reset to match
the heating load.

• Setpoint decreases Æ load the
chiller

• Setpoint increases Æ unload the
chiller

Note that the UCM still operates as
a chilled-water controller.

On the UCM-CLD, the parameter
“External Chilled Water setpoint”
has to be enabled.