Trane HORIZON ABDA User manual

Controls
Single and Two-Stage Steam and
Two-Stage Direct-Fired
Absorption Chiller
With Microprocessor Control Panel
Unit Models
ABDA, ABTF, ABSD
ABS-CTR-3B
HORIZON®
April 2004

2
Table of Contents
(1) Introduction - 3
(2) Absorption Cycle - 4
(3) Sequence of Operation - 11
(4) Control Panel Identification - 16
(5) Using the Control Panel - 22
•Operator Interface
• Report Menus
•Password
• Operator Settings
• Service Settings
• Field Startup Group
• Machine Configuration Group
•Service Tests
•Diagnostics
(6) Sensors and Controls - 55
(7) Control Strategy - 63
(8) Leaving Chilled Water Temperature
Control - 65
(9) Low Leaving Water Temperature Cutout - 66
(10) Concentration Control - 67
© 2003 American Standard Inc. All rights reserved.
(11) Control System Proportional, Integral, and
Derivative (PID) Control - 69
(12) Control System Limits - 70
(13) Crystallization Sensing Detection and
Recovery (SDR) - 71
(14) Absorber Entering or Low Condensing
Temperature Limit - 75
(15) Low Chilled Water Temperature Cutout
(LCWTC), Low Refrigerant Temperature Cutout
(LRTC), and Differential to Start and top - 76
(16) Interstage Pressure Limit - 81
(17) Generator Solution Temperature Limit - 82
(18) High Exhaust and Gas Temperature
Limit - 83
(19) Steam Control - 86
(20) Generator Entering Hot Water Limit
Control - 87
(21) Purge System - 88
This advanced model Absorption machine was
developed with the assistance of Gas Research Institute.

3
(1) Introduction
The following information describes the Trane
microprocessor based absorption control panel (UCP =
Unit Control Panel). This section details the control
strategies designed to ensure a more reliable and efficient
chiller operation. Limit modes provide functional but
limited machine operation to avoid any safety shutdown,
therefore; keeping the chiller on line. When a safety
condition is actually violated, the UCP safeties provide
protection to the machine and personnel by terminating
machine operation. Proportional, Integral, and Derivative
(PID) lithium bromide concentration control provides for
stable and efficient machine performance. Reduced cooling
water temperatures to 65°F, when available, can further
improve machine efficiency.
The controls discussion within the operation maintenance
manual has owner level information that is not repeated
here. The content of this section is service level oriented.
Therefore, knowledge of the operation and maintenance
material is important for a complete understanding of this
control system. Review and understand the information in
this manual before troubleshooting or startup is attempted.
Manual Layout
The table of contents outline the topics covered.
The following are the major sections:
Absorption Cycle (Section 2) - This section covers the
basics of the solution cycle; how the refrigerant and lithium
bromide flows through the chiller. An understanding of the
absorption cycle is necessary to follow how the lithium
bromide cycle is controlled by the Unit Control Panel (UCP).
Sequence of Operation (Section 3) - The microprocessor
has a programmed sequence for machine startup,
shutdown, operating limit and safety shutdown. This
section describes these events in the sequence.
Control Panel Layout (Section 4) - This section provides
control type and location information within the unit
control panel.
Clear Language Display (CLD) (Section 5) - The (CLD) is the
device that allows the operator to communicate with the
machine. The details include how to use it and information
on reports, settings and functional keys.
Sensors and Controls (Section 6) - Various temperature
sensors and machine-mounted controls connect to the
control panel. This section explains the type and purpose of
all sensors and controls that are connected to the UCP.
Control Strategy (Section 7) - The control system objective
and strategy is discussed along with limit and shutdown
methods.
Limits and Safeties (Sections 8 - 20) - These sections
explain the limit and safety function of the UCP and how
they may affect machine operation. The limits provide
protection for the chiller to overcome transient operating
conditions.
Purge System (Section 21) - This section explains the
theory and operation of the Purifier Purge including the
setpoints, inputs, outputs, operating modes, operation
status and timers.

4
(2) Absorption
In the case of ABDA machines, a burner provides heat
energy input while the ABTF is a regulated supply of 115-
psig steam or 350°F hot water supplied to the high
temperature generator. In both cases refrigerant water
vapor is separated from the dilute lithium bromide solution
when it is boiled. The hot refrigerant vapor produced by the
high temperature generator is directed to the low
temperature generator tubes to further heat and boils the
lithium bromide and produce additional water vapor. This
vapor leaves the low temperature generator as condensed
refrigerant water that is piped to the condenser section. The
refrigerant vapor separated from the lithium bromide in the
low temperature generator passes to the condenser as
vapor where it also condenses. The entire condensed
refrigerant is then returned to the evaporator to replace the
refrigerant used by the evaporator. Using the refrigerant
vapor, that is produced in the high temperature generator
to produce additional refrigerant in the second stage
generator, provides the two-stage effect.
The lithium bromide cycle is reverse parallel. All the diluted
lithium bromide from the absorber is pumped through the
low temperature heat exchanger and then to the low
temperature generator where the lithium bromide is
partially concentrated.
When the partially concentrated lithium bromide solution
leaves the low temperature generator, part of the flow is
diverted to the high temperature solution pump, which
pumps the lithium bromide into the high temperature
solution and condensate heat exchangers, and then to the
high temperature generator. The lithium bromide that is not
diverted exits the low temperature generator and is mixed
with concentrated lithium bromide returning from the high
temperature generator, by way of the high temperature
heat exchanger and float valve. The resulting intermediate
lithium bromide solution passes through the low
temperature heat exchanger to the absorber spray solution
pump, for distribution over the absorber tubes completing
the lithium bromide cycle.
When the intermediate lithium bromide solution is sprayed
onto the absorber tubes, the solution is cooled from the
cooling tower water flowing through the tubes. The low
partial pressure created by this activity allows the lithium
bromide to absorb the refrigerant water vapor produced by
the evaporator section. The resulting dilute lithium bromide
solution falls to the bottom of the absorber, where it is
again pumped through the low temperature, high
temperature and condensate heat exchangers, before
entering the generators for refrigerant reclaim and
subsequent lithium bromide reconcentration.
The refrigerant pump circulates refrigerant that is stored in
the evaporator pan; to constantly wet the evaporator tubes.
As the refrigerant contacts the tubes containing warm
system water flowing through the evaporator tubes, the
refrigerant vaporizes, removing heat from the system
water. The resulting vapor is absorbed by the lithium
bromide in the absorber, to sustain the cooling process.
The fluid temperatures and lithium bromide concentrations
are illustrated in Figures 1 (Model ABTF) and 2 (Model
ABDA) and Tables 1 and 2, and are described in the
following text, are valid when the machine is operating at
the nominal design conditions of 44°F leaving evaporator,
85°F entering cooling water and 115 psig steam, or at
design burner input rate. The fluid temperatures and
concentrations will change if the cooling water drops below
design conditions, or the energy input are reduced for part
load operation. This machine is designed to operate
efficiently with an entering condenser water temperature of
95 to 54°F.

5
Condensate Heat Exchanger ABTF only
The condensate heat exchanger is used to recover heat
from the steam condensate, after it has passed through the
high temperature generator. Some lithium bromide
solution from the High Temperature Solution Pump (HTSP)
is supplied to one side of this heat exchanger, to reduce the
condensate temperature and preheat some of the lithium
bromide entering the generator.
Hot Water Heating ABDA only (Figure 1)
Heating only or simultaneous heating with cooling is
accomplished utilizing a heat exchanger. As system heating
water flows through the heat exchanger tube bundle a
relatively cool area compared to the hot refrigerant vapor is
created. This cool area draws hot refrigerant vapor (10
Items) through the heat exchanger where the vapor
condenses transferring heat to the system water (16 to 17
Items) within the heat exchanger tubes. The condensed
liquid refrigerant returns to the high temperature generator.
It should be noted that there is a trade off during
simultaneous heating and cooling; hot refrigerant vapor
consumed during heating of the system water is no longer
available for cooling loads. This creates the need to
establish a priority mode of operation, cooling priority or
heating priority. The control system will utilize the available
refrigerant to meet the needs of the priority mode of
operation. The priority is selected at the clear language
display under operator settings.

6
Figure 1. ABTF fluid cycle - (Ref. Table 1)
Steam-Fired Absorption Unit
Steam-Fired Generator
Condenser Heat Exchanger (HXER)
High Temperature Heat Exchanger (HXER)
Low Tem - perature Heat Ex- changer (HXER)
High Temperature Generator Pump
Low Temperature Generator
Evaporator
Condenser
Purifier Purge
Evaporator Spray Pump
Low Temperature Generator Pump
EDUCTOR
Absorber Spray Pump
Absorber Refrigerant
storage

7
Point Concentration Temperature Temperature
% (°F) (°C)
1 Absorber Dilute Solution 58 95 35
258 180 82
3 Solution Leaving the Low Temperature Generator (LTG) 60 190 88
4 Solution Entering the High Temperature Generator (HTG) 60 300 149
5 Solution Leaving the High Temperature Generator (HTG) 65.5 325 163
665.5 240 116
763.5 215 102
863.5 125 52
961.5 112 44
10 – 300 149
11 – 190 88
12 Condensed Refrigerant – 100 38
13 Evaporator Pump Refrigerant – 42 6
14 System Chilled Water/Entering – 54 12
15 System Chilled Water/Leaving – 44 7
16 Absorber Cooling Water – 85 29
17 –9334
18 –9736
19 – 346 174
20 – 346 174
21 Condensate Leaving Machine – 210 99
Table 1. ABTF machine cooling cycle (See Figure 1)
Lithium Bromide Solution
or Refrigerant Water
Absorber Dilute Solution Entering the Low Temperature
Generator (LTG)
Solution Leaving High Temperature Heat Exchanger
(HTHX) and Flow Control Device
Mixed Solution (Intermediate with Concentrated)
Entering Leaving Temperature Heat Exchanger (LTHX)
Solution Entering Absorber Sump or Spray Pump
Absorber Spray Solution (Mixed with absorber dilute)
Absorber Leaving or Condenser Entering Cooling
Water
Condenser Leaving Cooling Water
Steam Entering Unit and 115 psig
Condensate Leaving Generator or Entering
Condensate Heat Exchanger
High Temperature Generator (HTG) Refrigerant Vapor
Low Temperature Generator (LTG) Refrigerant Vapor

8
Figure 2. ABDA fluid cycle - (Reference Table 2)
Direct - Fired Absorption Unit
Direct-Fired
Generator
High
Temperature
Heat
Exchanger
(HXER)
Low
Temperature
Heat
Exchanger
(HXER)
High
Temperature
Generator
Pump
Low Temperature
Generator
Evaporator
Condenser
Purifier
Purge
Evaporator Spray
Pump
Low
Temperature
Generator Pump
EDUCTOR
Absorber
Spray Pump
Absorber
Refrigerant
Storage
Hot Water Heater

9
Point Concentration Temperature Temperature
% (°F) (°C)
1 Absorber Dilute Solution 57 95 35
257 165 74
359 175 79
459 275 135
565.5 320 160
665.5 210 99
763 200 93
863 118 48
961.3 112 44
10 – 305 152
11 – 193 89
12 Condensed Refrigerant – 102 39
13 Evaporator pump refrigerant – 42 6
14 System Chilled Water - entering – 54 12
15 System Chilled Water - leaving – 44 7
16 System heating Water - entering – 130 54
17 System heating Water - leaving – 140 60
18 Absorber Cooling Water – 85 29
19 –9535
20 – 100 38
21 Exhaust Gas – 350 177
Table 2. ABDA machine cooling cycle (See Figure 2)
Note: Table 2 is a typical example of a machine operating at a
standard rating point. (for example, 85° tower, 44° leaving chilled
water at full load).
Lithium Bromide Solution
or Refrigerant Water
Absorber Dilute Solution Entering the Low Temperature
Generator (LTG)
Mixed Solution (Intermediate with Concentrated) Entering
Low Temperature Heat Exchanger (LTHX)
Absorber Spray Solution (Mixed
with absorber dilute)
Absorber Leaving or Condenser
Entering Cooling Water
Condenser Leaving Cooling
Water
Intermediate Solution Leaving the Low Temperature
Generator (LTG)
Intermediate Solution Entering the Low Temperature
Generator (LTG)
Concentrated Solution Entering the High Temperature
Generator (HTG)
Concentrated Solution Leaving High Temperature Heat
Exchanger (HTHX) and Flow Control Device
Mixed Solution Entering
Absorber Sump or Spray Pump
High Temperature Generator (HTG) Refrigerant vapor
Low Temperature Generator (LTG) Refrigerant Vapor

10
Machine Solution Cycle
The machine solution cycle is discussed in this section. Refer to the cooling cycle schematic, Figure 3, during the cycle
explanation and reference Table 3.
Figure 3. Single-stage absorption refrigeration cycle
Table 3. Machine cooling cycle (Ref. Figure 3) (Typical Temperatures)
Concentration Temperature Temperature
Point LiBr Solution or Refrigerant Water % (°F) (°C)
1 Absorber Dilute Solution 60.8 107 42
2 Absorber Dilute Solution Entering the LTG 60.8 185 85
3 Solution Leaving the LTG 64.4 216 102
4 Solution Entering ABS Sump/Spray Pump 64.4 129 54
5 ABS Spray Solution (Mixed w/abs dilute) 63.1 121 49
6 LTG Refrigerant Vapor NA 208 98
7 Condensed Refrigerant NA 110 43
8 Evaporator Pump Refrigerant NA 41 5
9 System Chilled Water/Entering NA 54 12
10 System Chilled Water/Leaving NA 44 7
11 Absorber Cooling Water NA 85 29
12 Absorber Leaving/Condenser Entering Cooling Water NA 94 34
13 Condenser Leaving Cooling Water NA 101.6 38.6
14a Steam Entering Unit @12 psig @ Sea Level NA 244 118
14b Hot Water Entering Unit @270°F (option) NA 270 132
15a Condensate Leaving Generator NA 244 118
15b Hot Water Leaving Generator (option) NA 222 106
1
9
7
13
5
11
3
8
2
14
6
12
4
10
15

11
(3) Sequence of Operation
The sequence of operation illustrates time and events that
occur at initial power-up, at startup when auto is selected,
or auto off cycle, or manual stop operation. The time line
sequence of operation follows the events that are
discussed in the following text.
The time line illustration indicates time and corresponding
event. The operator interface displays the time and events
that are referenced in the sequence as they occur.
Familiarization with the sequence helps to understand
when external and internal control devices are cycled on or
off. The time line provides information that may not be
obvious when watching the display. Additionally, this
information can be used for abnormal operation
troubleshooting purposes.
Operational Diagnostics During Machine
Startup.
During the machine start sequence, the chiller relies on
external devices to successfully start and provide correct
feedback. Specifically, the devices and diagnostics include
the chilled water and condenser pump starter, flow switch
confirmation, and ventilator fan operation. The appropriate
message will be displayed on the operator interface as the
start sequence progresses.
The UCP2 waits up to four minutes and fifteen seconds for
proof of chilled water flow, after a water pump start
command output is enabled. Failure to receive chilled
water flow confirmation within the allotted time results in a
message stating “Diagnostics -auto.” This is a MAR-auto
restart diagnostic where the chiller will start once the
chilled water flow switch logic is satisfied.
Failure to receive condenser water flow or ventilator fan
confirmation within the time period’s results in an MMR-
Manual restart diagnostic where the chiller must be reset
before continued operation is allowed.
ABDA Burner Sequence
The burner start sequence is the same for cooling or
heating operating. Always refer to the burner manufacture
literature and the actual sales order which may have
inclusions for special devices. A typical burner sequence of
operation is provided in the burner section of this manual.
The burner has a flame safeguard device that controls the
burner when there is a call for heat from the chiller panel.
The flame safeguard controls burner startup, shutdown,
and monitors burner operation. After confirmation of
combustion, the chiller sets the burner-firing rate via an
analog signal from the burner module. The fire rate signal
is proportional to the energy input as determined by the
chiller control.

12
Sequence of Operation
(Continued on Next Page)
Sequence of Events from a Stop or Auto condition through Start
(No intervening Power Ups or Software Resets.).
Starting Absorber or Condenser Pumps
Time
Line 1
Standard Mode
Display:
Events
:
Go to
Time
Line 2
(Below)
Chilled Water Pump Off
Condenser Water Pump Off
Solution Pumps Off
Absorber and Refrigeant Pumps Off
Energy Input Closed
Ignore Interstage Pressure
Sensor Failure Diagnostics.
All Other Diagnostics are
active.
Ventilation Off
Refrigerant Drive Valve (RDV1) Open
Stop Auto
Wait for Chilled Water Flow,
If flow not established
in less than 4 minutes and
15 seconds then issue:
Chilled Water Flow not Est.
MAR
Differential to Start
is Reached. (Cooling Required)
Ventilation Started
Condenser Water Pump Started
High Temperature Solution Pump
Started (Across the line )
Low Temperature Solution Pump
Started (Adaptive Frequency Drive
(AFD) at Min Speed)
Chilled Water
Pump Started
Wait for a
Call for
Cooling
(See Note 5)
Wait for Condenser Water
Flows,
If flow not established
in less than 4 minutes and
15 seconds then issue:
Condenser Water Flow not
Est.
MMR
Chilled
Water
Flow
Established
Point of Re-Entry if the Operator
Hits AUTO From Dilution Cycle
or
Reset from Diagnostic Auto
or
Waiting for Differential to Start
(System in AUTO Mode)
Variable 6 second to 4
minutes, 15 seconds
Variable 6 seconds to 4 minutes,
15 seconds
Variable
Time
Line 1a
START
AUTO Selected
Time Line 2
Events
:
Go to
Time
Line 3
(Next Page)
Standard Mode
Display:
Ignore Interstage
Pressure Sensor
Failures until the Solution
Leaving Low Temperature
Generator (LTG) is 120°F
Command Flame
Safeguard to Begin
Start Sequence.
(See Note 3)
Starting - Pre-Heating Solution
Sequence of Events from a Stop or Auto condition through Start
(No intervening Power Ups or Software Resets.).
If no Combustion
Confirmation after Variable Timer
Expires Issue: Combustion Overdue - MMR
ABDA Combustion
Confirmed
Waiting to Establish
a Mixed Concentration
of 54% Lithium Bromide
Modulate Energy to
Satisfy Low Temperature Heat
Exchanger (LTHX) Crystallization
Margin via Concentration
of Mixed Solution.
Modulate Low Temperature
Solution Pump AFD to
satisfy Leaving Water
Temperature.
Refrigerant Pump
Started
Unit is Running
Starting - Waiting for Combustion
ABDA Only
IF Ventilator Option Installed,
Verify Ventilator Operation
If Not Verified Issue MMR.
Var. Based on Concentration
Hold 40% of
Energy Allowable
Range and Cont.
Pre-Heat with
Refrigerant Pump On
Hold for 3
minutes
to Stabilize
System
Energy Input to 40% of
allowable range and Begin
Pre-Heat with Absorber and
Refrigerant Pumps Off
(See Note 1 and 6)(See Note 6)
(See Note 3)
Pre-Purge
90+ Seconds
Absorber Pump
Started
Indicates Time Line (1, 2, 3 or 4) Location
Enable Steam
Supply
Pressure
Diagnostic

13
Sequence of Operation
(Notes - Reference Next Page)
Events: Stop Low Temperature Solution Pump
Stop High Temperature Solution Pump
Stop Absorber Pump
Ventilation Stopped
Chilled Water
Pump off delay
Go to
Time
Line 1
Monitor Strong Solution Temperature Leaving Heating,
If <= 200°F then 3 Minute Dilution Cycle.
If > 200°F then 15 Minute Dilution Cycle
Time Line 3
Dilution Cycle
Local or Remote Stop
Standard
Mode Display:
Sequence of Events: From Running through Dilution Cycle
(No intervening Diagnostics or Software Resets.).
Unit is Running
Unit was Running
For an indeterminate
amount of time.
Open Refrigerant Dump Valve (RDV1) to Dilute Solution
Stop Refrigerant Pump
Stop Condenser Water Pump
Command to Low Energy to Low Fire
and Stop Burner (ABDA)
Command Low Temperature Solution Pump
AFD to 75% of Allowable Speed Range
Dilution
Timer
(See Note 4)
15 Seconds
Post
Purge
(Note 3)
While Running all
Limits are Active
Loss of Power During
This State will Result
in a Unit Start When
Power Returns if There
is a Need to Cool.
If There is no need to
Cool when Power Returns
a Dilution Cycle
Will be initiated.
(See Note 1 and 6) (See Note 7)
Go to
Time
Line 1a
(Previous Page)
Auto
Stop Chilled
Water Pump
Completes Dilution Cycle After Satisfying Load
Sequence of Events: Panic Stop
Stop Stop
Auto
Chilled Water Pump Off
Condenser Water Pump Off
Solution Pumps Off
Refrigerant Pump Off
Absorber Pump Off
Energy Input Off
Ignore HPC Sensor Failure
Diagnostics.
All Other Diagnostics are
active.
Ventilation Off
Refrigerant Dump Valve
(RDV1) Closed
All Stop Modes
All Running Modes
Operator Hits
Stop Twice
within 5 Seconds
This State May
Only be Exited
by Pressing Stop
or Auto Keys
The Auto or Stop switch is
set to Stop. Unit will Enter
a Dilution Cycle.
The Unit will Not start unless
the Auto key is pressed.
The Auto/Stop switch is
set to Auto. Unit will Enter
a Dilution Cycle.
Operator
Presses
Stop
Operator
Presses
Auto
Events:
Power Off
During AUTO
or Dilution
Cycle
Power On
Time Line 4
Interstage
Pressure
Sensor
Open/Short
Diagnostics
Disabled
See Note 2
(Next Page)
Blank Reset (Hard)
START
(Previous Page)
Stop Selected or AUTO Differential to Stop Occurs
(Cooling Satisfied)
Standard Mode
Display:
See Note 9
(Next Page)
1 Second

14
Sequence of Operation Time Line
Referenced Notes (See pages 11 & 12)
1) See “Using the Control Panel” for a listing of valid
modes that may occur during “Unit is Running.”
2) Upon power up, refrigerant dilution valve 1 (RDV1)
remains off for thirty seconds.
3) Model ABDA Only - For the specific flame safeguard
sequence see the appropriate burner literature.
4) When a “need to cool” exists, an incomplete dilution
cycle can be exited by pressing the Auto key. The chiller will
proceed with a new startup sequence.
5) The “Auto, waiting for a need to cool” can be exited by
pressing Stop.
6) Power loss at this point will result in a dilution cycle
upon re-establishing power, if there is no need to cool.
7) Power loss at this point will result in the remainder of a
dilution cycle being completed upon re-establishing power.
8) Chilled water pump will be stopped after the dilution
cycle is completed for all Machine Shutdown Auto Reset
and Machine Shutdown Manual Reset except in the case of
chilled water pump flow overdue where the chilled water
pump signal remains on.
9) Panic stop; operator presses the stop key twice within 5
seconds. This state may be exited by pressing either the
stop or auto key.
Startup/Shutdown
Startup Pre-heat
Solution pumps are started before energy is input.
The controls execute a pre-heat sequence upon startup to
establish an adequate concentration level before releasing
to closed loop control. Pre-heat sequence consists of the
energy input command held at a reduced rate. (40%) until
the Lithium Bromide solution concentrations reach 54%.
Service Tests: Manual energy input is allowed during this
pre-heat sequence.
Control of Leaving Water Temperature and concentration
are overridden.
Limits and safeties are active.
Shutdown Dilution Cycle
When the chiller cycles OFF a dilution cycle mixes the
strong lithium bromide solution with refrigerant water to
reduce solution concentrations and minimize the potential
for solution crystallization. The dilution cycle is performed
on all shutdown modes with one exception. The exception
is a “Panic Stop” which consists of an operator depressing
the stop key twice) within a 5 second period. This will stop
the machine without the normal dilution cycle. A restart can
be initiated at anytime by pressing the auto key. A dilution
cycle is initiated by pressing the stop key.
Terminating the energy input, opening the refrigerant
dump valve, and running the solution pump for 3 to 15
minutes dilutes the solution. This dilution cycle duration is
determined by the solution temperature when the dilution
sequence is initiated.
The refrigerant valve (RDV1) dumps refrigerant from the
evaporator into the absorber on command to dilute the
lithium bromide solution. This action occurs when a
dilution cycle or safety shutdown is initiated by the
machine control.
Dilution Time
Less than 158°F Less than 200°F 3 minutes
Greater than or Greater than or 15 minutes
Equal to 150°F Equal to 200°F
Solution Temperature Leaving High
Temperature Generator (HTG)
Solution Temperature Leaving LT6 +

15
During the dilution cycle Refrigerant Dump Valve 1 (RDV1)
opens. Once opened, RDV1 remains open until the dilution
cycle is completed, or the machine is restarted after power
failure, or
control reset.
The operator can abort the dilution cycle to restart the unit
by pressing the auto key to restart. The chiller will restart if
the LEAVING WATER TEMPERATURE is greater than the
differential to start set point.
If a reset is performed during the dilution cycle, and there is
dilution time remaining the dilution cycle will be continued.
Normal Stop
Press the stop key for a machine stop mode. The alternate
methods to stop are the External stop input and remote
clear language display (CLD) “Stop”. Reaching the
differential to stop chilled water setpoint is another
condition that results in a shutdown sequence and is
followed by a restart when the differential to start chilled
water set point is reached.
The stop mode shutdown sequence is as follows:
When the CLD stop command is initiated, the burner is
driven to low fire. A 30-second run unloaded delay, allows
the burner to move to low fire, from a high fire position,
before the burner start command is removed.
The solution pumps are automatically adjusted to 75% of
their allowable operating range during the dilution cycle.
The condenser water and evaporator refrigerant pumps are
cycled off.
The chilled water pump remains on through the dilution
cycle and until the CLD adjusted CHWP time delay expires.
When the dilution cycle is complete, the machine solution
pumps and ventilation fan are stopped. The RDV1, which
opened when the dilution cycle started, remains open until
the machine is restarted. The CLD displays stop with the
completion of the dilution cycle.
Panic Stop
Panic Shutdown (Pressing the Stop key twice within 5
Second Interval initiates a machine panic stop)
NOTE: This is not to be used unless absolutely necessary.
Failure to properly dilute lithium bromide can crystallize the
chiller.
Panic stop can only be exited at the local CLD. When a
panic stop is initiated the following events occur:
- The machine solution pumps are stopped immediately
and without a DILUTION cycle.
- The chilled water pump (CHWP) and cooling water pump
(CWP) are also commanded off immediately.
- The Refrigerant Dump valve (RDV1) is opened to dilute the
lithium bromide in the absorber with refrigerant.
- The Ventilator fan is stopped.
- The Energy input start command is removed, stopping
the burner.
- The CLD will display “Panic Shutdown”
To exit Panic Shutdown either press AUTO or STOP.
Pressing the STOP key will initiate a dilution cycle. Pressing
the AUTO key will allow a chiller restart.
The chiller will then resume normal operation assuming
that the panic condition was corrected prior to restart.
Safety Reset
If the operator performs “Reset” during the dilution cycle,
the control remembers the amount of time remaining in
the current dilution cycle. Once the reset is complete, the
dilution cycle will be re-entered automatically. If the
machine was operating when a safety shutdown occurred
the machine will resume normal operation after resetting
the CLD.

16
(4) Control Panel Identification
The following information explains the details of chiller
control. The details include hardware identification and
location, control strategies, limits and operating sequences.
Control Panel Location and
Internal Hardware
Component Description
The main control panel (Figure 3) has two sections. The left
side (control side) includes clear language display
(mounted through door), chiller, circuit, purge, stepper, and
optional communications modules, a terminal block, and a
115Vac-control voltage to 24Vac transformer. The right side
(power side) consists of a main line voltage terminal block
or disconnect service for line power connections, line
voltage to control voltage transformer, relays, transformers,
starter module and purge module. Line voltage is restricted
to the right-hand side.
The inner control panel components are illustrated in
Figure 4. Modules are stacked in a top, bottom or middle
configuration.
Voltages in Panels
Voltages present within the unit control panel includes:
• Three phase line voltage (power side only)
• 115Vac control circuits
• 24Vac module power supply
Low voltage, low power (30Vdc or less — Class II) circuit
connection points are located on the left side of modules.
High voltage, high power (greater than 30Vdc — Class I)
circuit connection points are located on the right side of
modules. All 115Vac circuits are Class 1. See Figure 5.
The stepper drive uses less than 30Vdc however, the output
signals are Class 1 due to its output current (amps).
Class 1 and Class 2 wiring must not be routed together
without shielding.
Figure 3. Machine control panel
Control Side Power Side

17
Figure 4. Panel layout
or Less
Bot-
tom
Top
Top
Top
Bot-
tom
Bot-
tom
1U1 - Starter Module
1U2 - Circuit Module
1U3 - Chiller Module
1U4 - Purge Module
1U5 - Stepper Module
1U7 - Options Module *
1U8 - Tracer Communication Module *
1U9 - Remote Clear Language Display *
IPC Buffer Module
1U10 - Printer Communication Module *
1T1-2-3 - Phase Current Transformer
1T4 - Line Voltage Transformer
1T5 - Control Voltage Transformer
1T6-7-8 - Under-Over Phase Voltage
Transformers *
L1-2-3 - Main Power Entrance
1TB2 - Pump Motor Terminal Block
1TB3 - UCP2 Control Panel Mounted
Terminal Strip
* Not Standard
1S1 - Line Voltage Fused Disconnect
Switch *
1K1 - Refrigerant Pump Abnormal Relay
1K2 - High Temperature Solution Pump Abnormal
Relay
1K3 - Interstage Vapor High Pressure
Cutout Relay
1K11 - Refrigerant Pump Contactor
1K12 - HT Solution Pump Contactor
1U11 - Refrigerant Pump Overload
1U12 - HT Solution Pump Overload
1F1, F2 - Line Voltage Transformer Fuses
1F3 - Phase Voltage Transformer Fuse *
1F4, F5, F6 - Refrigerant Pump and
Absorber Solution Pump Motor Fuses
1F7, F8, F9 - High and Low Temperature Solution
Pump Motor Fuses
Panel Layout Legend

18
Control Modules
Microprocessor control modules are mounted on the left-
hand and right-hand side of the main unit control panel
and in the burner control panel.
Figure 5. Location of microprocessor control modules within the main unit control panel and burner panel
Comm 3 & 4
IPCB
Printer Intf
Purge
Stepper
Class II Wiring Class I Wiring
Left Hand Side of Unit Control Panel Right Hand Side of Unit Control Panel
Backplane
Options
Chiller
Starter
Circuit
Burner
Remote Mounted Burner Control Panel
(ABDA only)
Class II Wiring Class I Wiring
Class II Wiring Class I Wiring

19
Signal Block Diagram
The following block diagram illustrates the interrelationship
of the interprocessor communications (IPC) link. These
connections allow the individual microprocessors to
communicate. All standard control modules are mounted
in the chiller control panel with the exception of the burner
module, which is mounted in the burner control panel. The
option modules (shaded box) are present only when
specified. The Tracer, printer, and remote CLD are optional
components that provide communications outside of the
unit control panel. The remote CLD is the only
communication device that is installed outside of the
machine control panels.
pumps are electrically controlled and interlocked to the unit
control panel. This interlocking arrangement provides
protection from improper system water pump control or
loss of flow conditions, which can damage the machine.
This module communicates with the stepper module to
control machine energy input, the starter module to start or
stop solution pumps, control solution flow, and the
operator interface to display operation status information to
the operator.
Setpoint Communication and Storage
The machine setup information selected at the operator
interface is stored in the chiller module memory. This
module contains non-volatile memory that is retained when
the panel is not powered. The
Note: The Tracer and Printer are not expected to exist
together in an installation.
The Chiller Module (1U3) serves as the master control for
the unit. It is responsible for implementing the Leaving
Water Temperature control algorithms that control chiller
capacity. The chiller module manages machine safety,
operating limits, and chilled water temperature by
monitoring unit-mounted sensors and information from
other modules on the interprocessor communications (IPC)
link.
When machine-operating conditions change, the chiller
module initiates communications to the other panel
modules to manage that change. The input or output ports
on the chiller module monitor and/or control-chilled water
and cooling water pump operation. The evaporator and
condenser water
module is responsible for verifying that the setup
memory is not corrupted, and for substituting default
settings if the stored settings become corrupted.
1U1 Starter Module
The starter module controls pump operation and provide
an interface to the adjustable frequency variable speed
drives for lithium bromide solution flow control.
1U2- Circuit Module (standard)
The circuit module is located in the lower portion of the
control panel beneath the Chiller module. The main
purpose of the circuit module is to control and manage the
Lithium Bromide. The circuit module is responsible for
implementing the concentration control algorithm. Also,
the circuit module collects input data from unit temperature
and pressure sensors, and switch inputs, and makes this
information
Burner
Panel
Options
Module
(Optional)
IPC
Remote CLD
(Optional)
IPCB
(Optional)
Tracer
(Optional)
TCI IV
(Optional) Comm 4
Comm 3
To Other UCMs
ICS Proprietory
Unit Proprietory
To Other Tracer
or Other BAS
Printer
(Optional)
Printer Interface
Module (Optional)
Burner
Module
Unit Control Panel with Modules Burner
Purge Module
ABDA Only
Local CLD Chiller
Module
Circuit
Module
Stepper
Module
Starter
Module

20
available to the chiller module via an interprocessor
communications link This module also provides output
contact closures for control devices.
1U4_ Purge Module
The purge module manages the purge system logic. In
auto mode, the module monitors a sensor located on the
condensing unit suction line to determine when pumpout
is required. A module output then turns on the pumpout
cycle. The pumpout cycle data is monitored and stored.
This information is available from the clear language
display (CLD).
1U5 Stepper Module (standard)
The stepper module 1U3 receives input from unit sensors
and binary input devices. This information is provided to
other modules as needed on the IPC link. The stepper
output is used to control the hot water valve when the
heating option is specified and the energy value for steam
or hot water indirect fired units.
1U6 Local Clear Language Display (LCLD, or
Operator Interface)
The LCLD is mounted on the control panel door. The
module has connecting wiring accessible on the door
backside. The LCLD is used to communicate with the chiller
module in order to change various machine-operating
parameters and monitor machine data. See the operator
interface for complete details.
1U7 Options Module
When optional functions are specified that required
additional input or outputs (I/O) option modules are used.
Some of these options are standalone, such as Generic
BAS interface; other options support other additions to the
chiller control. Features supported by the options module
are external chilled water and hot water setpoint and other
hot water simultaneous heating requirements.
1U8, 9,10 Optional External Communications Modules
•IPC Buffer Module - Used to communicate to
external devices.
•Printer Communications Interface - required for
printer compatibility.
The printer interface module provides a pre-
formatted chiller log to a printer. The printer
interface can be programmed via the LCLD to
print a chiller log on command, at the time of a
diagnostic, and/or on a periodic basis.
•Tracer Communications Interface Module -
Required for Tracer compatibility.
Comm 4 are an optional module that provides
a 9600-baud non-isolated communications link
to SUMMIT. Comm 3 is an optional module
that provides a 1200 baud isolated
communications link to TRACER 100.
3U3 Burner Module (ABDA only)
The burner module serves as an interface to the burner and
flame safeguard control. Some of these functions include
burner start, reset, and fuel select, alarm feedback, and
combustion confirmation and provides an interface for
burner firing rate modulation output. The burner module
also houses the simultaneous heating water control
algorithms providing control output for the heating system
water valve located on the optional auxiliary heat
exchanger. The burner module has other input or output
(I/O) capabilities used to support I/O expansion.
Terminal Blocks
Terminal blocks are utilized for various connection points
within the control panel as identified below.
• 1TB1 Main power terminal block (standard).
• 1TB2 Pump Motor Terminal Block - Line voltage
distribution point for the three phase solution pump
motors.
• 1TB3 Control Panel Mounted Terminal Strip - Provides
termination points for internal wiring, and also for field
wiring interface points. See the electrical connection
points on the typical unit schematics.