Johnson Controls YORK YHAU-CGN Installation and operating instructions

Form: 155.32-ICOM1.EN.GB (422)
Supersedes: 155.32-ICOM1.EN.GB (318)
Installation, Operation, and Maintenance
Issue Date: 2022-04-19
YHAU-CGN/H Double Effect Direct Fired
Absorption Chiller-Heater (Mod A)
120 ton to 1600 ton 422 kW to 5626 kW

2 YHAU-CGN/H Double Effect Direct Fired Absorption Chiller-Heater (Mod A)

Contents
ContentsGeneral safety guidelines................................................................................................................................7
Safety symbols....................................................................................................................................... 7
Changeability of this document...........................................................................................................8
Associated literature..............................................................................................................................8
Nomenclature........................................................................................................................................ 9
General chiller-heater information and safety...........................................................................................10
Introduction..........................................................................................................................................10
About this manual............................................................................................................................... 10
Warranty............................................................................................................................................... 10
Quality assurance................................................................................................................................ 11
High temperature and pressure cleaning........................................................................................ 11
Emergency shutdown......................................................................................................................... 12
Safety labels..........................................................................................................................................13
Product description........................................................................................................................................14
Chiller-heater components.................................................................................................................14
Control panel........................................................................................................................................14
How direct fired units work................................................................................................................ 15
Evaporator............................................................................................................................................ 17
Absorber............................................................................................................................................... 17
Two-step evaporator – absorber....................................................................................................... 17
Plate type heat exchangers................................................................................................................ 18
Parallel flow.......................................................................................................................................... 18
High temperature generator (HTG).................................................................................................. 19
Low temperature generator (LTG).................................................................................................... 19
Condenser............................................................................................................................................ 19
Crystallization.......................................................................................................................................20
Why crystallization occurs.................................................................................................................. 20
Handling, storage, installation and reassembly.........................................................................................21
Inspection............................................................................................................................................. 22
Inspection window.............................................................................................................................. 22
Installation guidelines.........................................................................................................................22
Hoisting the machine.......................................................................................................................... 24
Moving the machine on rollers..........................................................................................................24
Structural support and installation................................................................................................... 26
Indoor and outdoor installation........................................................................................................ 28
Electrical................................................................................................................................................28
Precautions for use..............................................................................................................................29
Leak testing.......................................................................................................................................... 30
Electrical shock cautions.....................................................................................................................31
Use of gas............................................................................................................................................. 31
YHAU-CGN/H Double Effect Direct Fired Absorption Chiller-Heater (Mod A) 3

Use of oil............................................................................................................................................... 31
Vibration and isolation details........................................................................................................... 32
Nozzle arrangements..........................................................................................................................32
Fuel gas and oil piping system...........................................................................................................35
Hot insulation or cold insulation procedure.................................................................................... 37
Pressure release valve and relief piping...........................................................................................39
Pressure release valve discharge pipe material.............................................................................. 40
Pressure release valve piping construction..................................................................................... 40
Rupture disk and relief piping (option).............................................................................................41
Rupture disk discharge piping material........................................................................................... 42
Rupture disk discharge piping construction....................................................................................42
Rupture disk discharge piping sizing................................................................................................43
Technical data.................................................................................................................................................46
Upper communication specification................................................................................................. 75
Upper communication system configuration.........................................................................................75
Modbus TCP protocol communication....................................................................................................75
Connection port for Ethernet communication....................................................................................... 76
Communication specification................................................................................................................... 76
Modbus RTU protocol communication................................................................................................... 76
User-created............................................................................................................................................... 77
Two-wire type cable diagrams..................................................................................................................78
Four-wire type cable diagrams.................................................................................................................79
Communication data................................................................................................................................. 81
Noise emission........................................................................................................................................... 83
Commissioning...............................................................................................................................................84
General guidelines for use................................................................................................................. 84
Before operation........................................................................................................................................84
Precautions for the use of water....................................................................................................... 85
Chilled or hot water outlet temperature controller........................................................................ 86
Liquid level gauges..............................................................................................................................86
Start the chiller-heater........................................................................................................................86
Stop the chiller-heater........................................................................................................................ 87
Interlocking procedure....................................................................................................................... 87
Operation........................................................................................................................................................ 99
YHAU-CGN/H Control Center............................................................................................................. 99
Common items.....................................................................................................................................99
Change numeric values.................................................................................................................... 100
Main screen........................................................................................................................................101
Operating status...................................................................................................................................... 102
Data screen........................................................................................................................................ 103
Solution analysis or control panel parts replacement screen............................................................106
Solution pump overhaul or refrigerant pump overhaul screen.........................................................107
YHAU-CGN/H Double Effect Direct Fired Absorption Chiller-Heater (Mod A)4

Burner parts replacement or burner combustion check screen....................................................... 108
Trend screen............................................................................................................................................. 109
Hourly operation history screen............................................................................................................ 111
Minutely operation history screen.........................................................................................................113
Failure history screen.............................................................................................................................. 115
Alarm history screen................................................................................................................................117
Failure and alarm screen..................................................................................................................119
Failure........................................................................................................................................................119
Alarm......................................................................................................................................................... 122
Setting screen.................................................................................................................................... 123
Control parameter................................................................................................................................... 123
Valve operation........................................................................................................................................ 125
Date and time...........................................................................................................................................125
Operation switch......................................................................................................................................126
Select language........................................................................................................................................ 126
Single loop controller........................................................................................................................127
Run mode..................................................................................................................................................128
Ready mode..............................................................................................................................................129
Alarm mode.............................................................................................................................................. 129
Alarm codes.............................................................................................................................................. 130
Operational display..................................................................................................................................131
Auto/manual mode (RHW only).............................................................................................................132
Operation mode changeover...........................................................................................................133
Changeover to cooling mode................................................................................................................. 133
Changeover to heating mode.................................................................................................................133
Use simultaneous residential hot water supply mode (option).........................................................134
Changeover to residential hot water sole supply mode (option)......................................................135
Maintenance................................................................................................................................................. 138
Exhaust duct inspection....................................................................................................................138
Valve inspection.................................................................................................................................138
Solenoid valves.................................................................................................................................. 139
Pump shut off valves (option)..........................................................................................................139
Air release valves and drain valves (option)...................................................................................139
Purge valves....................................................................................................................................... 139
Start the chiller-heater after it has been stopped for a long period...........................................139
Checks before operation starts..............................................................................................................139
Checks after operation starts...........................................................................................................140
Purge procedure................................................................................................................................140
Capacity check method of vacuum pump...................................................................................... 140
Manual method to purge non-condensable gas directly from absorber...................................144
Manual method to purge non-condensable gas from the purge tank...................................... 144
Automatic method to purge non-condensable gas from the purge tank..................................145
Refrigerant refining method............................................................................................................152
5YHAU-CGN/H Double Effect Direct Fired Absorption Chiller-Heater (Mod A)

Manual refrigerant blow down and diluting method................................................................... 152
Decrystallization method..................................................................................................................153
Indications of crystallization...................................................................................................................153
Decrystallization................................................................................................................................ 153
Precautions for decrystallization..................................................................................................... 154
Maintenance items............................................................................................................................154
Refrigerant pump manual stop..............................................................................................................156
Purge manual start and stop..................................................................................................................157
Lifespan for various parts.................................................................................................................157
Water quality control.........................................................................................................................159
Chemical water treatment................................................................................................................160
Replacement of water.......................................................................................................................160
Treatment for long stoppage of the absorption chiller-heater................................................... 160
Chemical treatment...........................................................................................................................160
Flow speed in tubes...........................................................................................................................161
Storage method of the chiller-heater............................................................................................. 164
Wet storage method................................................................................................................................164
Dry storage method................................................................................................................................ 164
Precautions against external damage............................................................................................165
Storage method of the cooling water during heating operation period................................... 166
Wet storage...............................................................................................................................................166
Dry storage............................................................................................................................................... 167
Troubleshooting...........................................................................................................................................173
Troubleshooting performance issues.............................................................................................177
Vacuum pump....................................................................................................................................178
Abnormal solution and refrigerant levels...................................................................................... 179
Actions to take against power failure............................................................................................. 182
Decommissioning, dismantling, and disposal..........................................................................................183
Optional applications...................................................................................................................................184
Low temperature chilled water supply (model EX(H/S)L and EXW(H/S)L).................................184
YHAU-CGN/H Double Effect Direct Fired Absorption Chiller-Heater (Mod A)6

General safety guidelines
Important: Read before proceeding.
This equipment is a relatively complicated apparatus. During rigging, installation, operation,
maintenance, or service, individuals may be exposed to certain components or conditions including,
but not limited to: heavy objects, refrigerants, materials under pressure, rotating components, and
both high and low voltage. Each of these items has the potential, if misused or handled incorrectly,
to cause bodily injury or death. It is the obligation and responsibility of rigging, installation,
and operating or service personnel to identify and recognize these inherent hazards, protect
themselves, and proceed safely in completing their tasks. Failure to comply with any of these
requirements could result in serious damage to the equipment and the property in which it is
situated, as well as severe personal injury or death to themselves and people at the site.
This document is intended for use by owner-authorized rigging, installation, and operating or
service personnel. It is expected that these individuals possess independent training that enables
them to perform their assigned tasks correctly and safely. It is essential that, before performing
any task on this equipment, this individual reads and understands the on-product labels, this
document and any referenced materials. This individual must also be familiar with and comply
with all applicable industry and governmental standards and regulations pertaining to the task in
question.
Safety symbols
The following symbols are used in this document to alert the reader to specific situations:
DANGER
Indicates a possible hazardous situation which will result in death or serious injury if proper care is not
taken.
WARNING
Indicates a potentially hazardous situation which will result in possible injuries or damage to equipment
if proper care is not taken.
CAUTION
Identifies a hazard which could lead to damage to the machine, damage to other equipment and/or
environmental pollution if proper care is not taken or instructions and are not followed.
Note: Highlights additional information useful to the technician in completing the work being
performed properly.
7YHAU-CGN/H Double Effect Direct Fired Absorption Chiller-Heater (Mod A)

WARNING
External wiring, unless specified as an optional connection in the manufacturer’s product line, is not
to be connected inside the control cabinet. Devices such as relays, switches, transducers and controls
and any external wiring must not be installed inside the micro panel. All wiring must be in accordance
with Johnson Controls’ published specifications and must be performed only by a qualified electrician.
Johnson Controls will not be responsible for damage/problems resulting from improper connections
to the controls or application of improper control signals. Failure to follow this warning will void the
manufacturer’s warranty and cause serious damage to property or personal injury.
Changeability of this document
In complying with Johnson Controls’ policy for continuous product improvement, the information
contained in this document is subject to change without notice. Johnson Controls makes no
commitment to update or provide current information automatically to the manual or product
owner.
It is the responsibility of rigging, lifting, and operating or service personnel to verify the
applicability of these documents to the equipment. If there is any question regarding the
applicability of these documents, rigging, lifting, and operating or service personnel must verify
whether the equipment has been modified and if current literature is available from the owner of
the equipment before performing any work on the chiller-heater.
Associated literature
Manual description Form number
Absorption Chiller-Heater Long Term Storage 50.20-NM11
Long-Term Storage Checklist - Absorption Chiller-Heater 50.20-CL10
Long-Term Storage Requirements - General 50.20-NM10
Chiller - Heater Start-up and Commissioning Checklist 155.32-CL1
YHAU-CGN/H Double Effect Direct Fired Absorption Chiller-Heater (Mod A)8

Nomenclature
9YHAU-CGN/H Double Effect Direct Fired Absorption Chiller-Heater (Mod A)

General chiller-heater information and safety
Introduction
Hitachi YHAU-CG/H absorption chiller-heaters are manufactured to the highest design and
construction standards to ensure high performance, reliability, and adaptability to all types of air
conditioning installations.
This chiller-heater is for air conditioning or cooling a manufacturing process. Use this chiller-heater
after installing the chilled or the hot water pump, the cooling water pump, the cooling tower,
valves, strainers, pressure gauges, thermometers, or other relevant pumps and gauges, according
to the water quality information contained in Maintenance.
About this manual
This manual and any other document supplied with the unit are the property of Johnson Controls
which reserves all rights. This manual may not be reproduced, in whole or in part, without prior
written authorization from an authorized Johnson Controls representative.
In addition, this manual:
• Should be read thoroughly before attempting to operate or service the unit.
• Includes suggested best working practices and procedures, that are issued for guidance
only, and they do not take precedence over the stated individual responsibility or local safety
regulations.
• Contains all the information required for correct installation and commissioning of the unit,
together with operating and maintenance instructions.
• Contains detailed procedures, including installation, commissioning, and maintenance tasks
that must be performed by suitably trained and qualified personnel.
• The manufacturer will not be liable for any injury or damage caused by incorrect installation,
commissioning, operation, or maintenance resulting from a failure to follow the procedures
and instructions detailed in this manual.
Warranty
Johnson Controls warrants YHAU-CG/H chiller-heaters in accordance with the Limited Warranty
Engineered Systems Equipment Procedure. Refer to the Limited Warranty (Form 50.05-NM2).
Johnson Controls warrants all equipment and materials against defects in workmanship and
materials for a period of 18 months from the date of shipment or 12 months from the date of start-
up, whichever comes first, unless a labor or extended warranty has been purchased as part of the
contract.
The warranty is limited to parts only replacement and shipping of any faulty part, or subassembly,
which has failed due to defects in workmanship and materials. All claims must be supported by
evidence that the failure has occurred within the warranty period, and that the unit was operated
within the designed parameters specified.
All warranty claims must specify the unit model, serial number, order number, and run hours/
starts. Model and serial number information is printed on the unit identification plate.
The unit warranty will be void if any modification to the unit is carried out without prior written
approval from Johnson Controls. For warranty purposes, the following conditions must be satisfied:
• The initial start of the unit must be carried out by trained personnel from an authorized
Johnson Controls Field Service Office.
YHAU-CGN/H Double Effect Direct Fired Absorption Chiller-Heater (Mod A)10

• Only genuine Johnson Controls approved spare parts, oils, solutions, chemicals, and
refrigerants must be used.
• All of the scheduled maintenance operations detailed in this manual must be performed at
the specified times by suitably trained and qualified personnel.
Failure to satisfy any of these conditions will automatically void the warranty. Refer to Limited
Warranty (Form 50.05-NM2) for complete details.
Quality assurance
Units comply with the following directives:
• GB/T 18362-2008 Direct fired lithium bromide absorption water chiller-heater
• GB 18361-2001 Safety requirements of lithium bromide absorption water chiller (heater)
The unit must be grounded. No installation or maintenance work should be attempted on the
electrical equipment without first switching the power off, then isolating and locking-off the power
supply. Servicing and maintenance on live equipment must not be attempted. No attempt should
be made to gain access to the control panel or electrical enclosures during normal operation of the
unit.
Components may also have sharp edges. Reasonable care should be taken when working in
contact with any components to avoid risk of minor abrasions and lacerations.
High temperature and pressure cleaning
Do not use high temperature or pressure cleaning methods, for example, steam cleaning, on any
part of the pressure system as this may cause operation of the pressure relief device(s). Avoid
detergents and solvents, as these may cause corrosion.
11YHAU-CGN/H Double Effect Direct Fired Absorption Chiller-Heater (Mod A)

Emergency shutdown
In case of emergency, the control panel is fitted with an incoming supply circuit breaker with a red
handle. Turn the handle counter clockwise to shut down the chiller.
Figure 1: Emergency shutdown breaker
YHAU-CGN/H Double Effect Direct Fired Absorption Chiller-Heater (Mod A)12

Safety labels
For safe operation, read the instructions first.
WARNING: This machine may start automatically without prior warning.
WARNING: Hot surface.
WARNING: Safety relief valve may discharge gas or liquid without prior warning.
WARNING: Risk of electric shock.
WARNING: General attention symbol.
WARNING: On isolating the supply it may take up to 300 seconds for the capacitor voltage to fall
below 50 volts.
WARNING: Risk of fire.
WARNING: Risk of gas poisoning.
WARNING: Rotating object.
CAUTION: Prohibited.
CAUTION: Risk of fall.
CAUTION: Risk of getting hand caught in machinery.
CAUTION: Risk of electrical arc.
13YHAU-CGN/H Double Effect Direct Fired Absorption Chiller-Heater (Mod A)

Product description
The principle of refrigeration is the exchange of heat. In absorption liquid chilling, there are four
basic heat exchange surfaces: the evaporator, the absorber, the generator, and the condenser. See
Figure 2.
Like any refrigeration system, absorption chilling uses evaporation and condensation to remove
heat. The absorption cycle uses water as the refrigerant and lithium bromide (LiBr) as the
absorbent. It is the strong affinity that these two substances have for one another that makes the
cycle work. The entire process occurs in almost a complete vacuum.
Chiller-heater components
The absorption chiller-heater consists of the following components:
• Evaporator
• Absorber
• Condenser
• Generators
• Solution heat exchangers to heighten the cycle efficiency
• Pumps to circulate the refrigerant and solution in the cycle
• Purge unit to remove non-condensable gas from the machine
Control panel
The absorption chiller-heater comes with a factory mounted and pre-wired control system. The
control panel enclosure is equipped with a hinged access door with lock and key. The control panel
includes a touch panel showing all system parameters in various languages with numeric data in
metric units. For details of the control panel, see Operation.
Note:
• Confirm the main power switch is within 2 m from the ground. If It is not, install the
operation platform.
• When opening the control panel, turn off the power supply by using the handle breaker.
The unit is also equipped with two methods to start and stop operations:
• Touch panel
• External signal
YHAU-CGN/H Double Effect Direct Fired Absorption Chiller-Heater (Mod A)14

Figure 2: Main components of direct fired absorption chiller-heater
Callout Component
A Chilled or hot water outlet
B Absorber
C Cooling water outlet
D Condenser
E Low temperature generator
F High temperature generator
G Burner fan motor
H Natural gas inlet
I Burner fan
J Control panel
K Solution pump
L Cooling water inlet
M Chilled or hot water inlet
N Evaporator
How direct fired units work
The double effect or direct fired absorption chiller-heater uses water as the refrigerant and lithium
bromide (LiBr) as the absorbent. It is the strong affinity that these two substances have for one
another that makes the chiller-heater cycle work. The vapor pressure of the lithium bromide
solution is lower than the vapor pressure of the refrigerant. The vapor pressure of the LiBr solution
15YHAU-CGN/H Double Effect Direct Fired Absorption Chiller-Heater (Mod A)

is directly related to the amount of refrigerant, or water, present in the solution with the LiBr salt
and the solution temperature. The entire absorption process occurs in almost a complete vacuum.
Figure 3: Two step direct fired absorption chiller-heater cycle diagram (cooling mode) for
model EX(H/S) or model EXW(H/S)
Note: Temperatures and pressures on this graphic are representative, actual values may
differ.
YHAU-CGN/H Double Effect Direct Fired Absorption Chiller-Heater (Mod A)16

Evaporator
Liquid refrigerant enters the evaporator and is distributed over the top of the tube bundle. As the
refrigerant droplets cover the outside surface of the tubes, the heat from the returning chilled
water passing through the tubes causes the refrigerant to flash from a liquid to a vapor. The
temperature at which this happens depends on the evaporator shell pressure which is dictated
by the absorber section of the chiller-heater. The refrigerant vapor passes through the mist
eliminators and into the absorber section of the chiller-heater. As the liquid refrigerant passes
down through the bundle of evaporator tubes, more and more of the refrigerant vaporizes. The
refrigerant remaining in a liquid state at the bottom drains into the refrigerant tank and is pumped
back up the top of the tube bundle where the process is repeated.
Absorber
Concentrated LiBr solution enters the absorber section of the chiller-heater and is sprayed over
the absorber tube bundle. Because the vapor pressure of the concentrated solution is very low,
the refrigerant, or water, vapor from the evaporator flows into the absorber and is absorbed into
the LiBr solution. This mass transfer process lowers the concentration of the LiBr solution as the
refrigerant, or water, is absorbed into the solution. This dilution process generates heat and, if
not cooled, would eventually stop as the solution temperature would rise with a corresponding
rise in vapor pressure. This would be similar to closing the vanes or slowing down a centrifugal
compressor on a centrifugal chiller where the load was constant. The water flowing inside the
absorber tube bundle comes from the cooling tower and serves to cool the LiBr solution as it
flows down over the tube bundle. This allows the absorption process to continue and the solution
becomes more diluted as it absorbs more refrigerant vapors. When the LiBr solution reaches the
bottom of the absorber section, it goes into the suction of the solution pump. The liquid is then
pumped to the generators.
The following section describes the unique two-step evaporator-absorber design of the YHAU-CG
direct fired absorption chiller-heater.
Two-step evaporator – absorber
The evaporator and the absorber are each split into two sections. This design, similar to a series-
counter-flow chiller-heater arrangement along with the parallel flow cycle, enables lower LiBr
solution concentrations. This reduces pressure, the potential for corrosion, and the risk of
crystallization as well as improves efficiency in conjunction with other advanced components
described later in this section.
The two evaporators are in series with respect to the chilled water flow through the tubes. In other
words, the chilled water flows through the lower evaporator tubes first and then to the upper
evaporator tubes. Each evaporator operates at a slightly different temperature and pressure.
The refrigerant in the lower evaporator boils at a slightly higher temperature than in the upper
evaporator, consequently cooling the chilled water in two steps.
The two absorber sections are split as well, with the strong solution first entering the top of the
uppermost absorber and flowing down through the top absorber bundle. It then flows into the top
of the lower absorber section. The strong solution entering the upper absorber takes advantage
of its lower vapor pressure allowing the upper evaporator to operate at a lower pressure and
temperature.
When the LiBr solution enters the lower absorber section it is somewhat diluted from the
refrigerant vapor that boiled off in the upper evaporator. At this lower concentration the solution
vapor pressure would normally not be sufficient to provide an evaporator pressure low enough to
satisfy the leaving chilled water design. However, the lower evaporator is the first step of the chilled
water cooling cycle, and the dilute solution’s vapor pressure is adequate to maintain the required
temperature and pressure in the lower evaporator.
17YHAU-CGN/H Double Effect Direct Fired Absorption Chiller-Heater (Mod A)

The cooling tower water enters the lower absorber section first, keeping the vapor pressure of the
weaker solution as low as possible.
Both the refrigerant, or water, and the LiBr dispersion system are gravity fed and made of stainless
steel.
Plate type heat exchangers
The diluted, or weak, LiBr solution that leaves the absorber section is pumped through various
plate type heat exchangers, such as the low temperature heat exchanger, LTG refrigerant
condensate heat exchanger, and high temperature heat exchanger, before it enters the high
temperature generator and low temperature generator sections. These plate type heat exchangers
provide cycle efficiency by preheating the dilute solution. Preheating the dilute solution reduces
the consumption of the driving heat source in the high temperature generator section. The
concentrated solution flows out of the generators and back through the various heat exchangers.
The relatively high temperature solution streams from the two generators are used to pre-heat the
weak solution stream leaving the absorber.
Parallel flow
The unique parallel flow divides the solution between the low temperature generator and the high
temperature generator sections into two parallel, balanced paths. The result is a safer and more
efficient operation at a much lower pressure than conventional series-flow designs. The various
solution-to-solution plate type heat exchangers optimize efficiency by enabling effective heat
transfer between the diluted, or weak, and the concentrated LiBr solutions.
YHAU-CGN/H Double Effect Direct Fired Absorption Chiller-Heater (Mod A)18

High temperature generator (HTG)
YHAU’s high temperature generator section has the unique liquid tube design in which the dilute
Lithium Bromide solution coming from the high temperature heat exchanger is inside the tubes.
The products of combustion, or exhaust gas from burning of natural gas, are on the shell side.
The hot refrigerant vapor boiled off is sent to the low temperature generator. This leaves behind a
strong solution which is returned through the high temperature heat exchanger.
The liquid tube design is efficient and compact with lower pressure drop as compared to the
conventional smoke tube type design in which the exhaust gas is inside the tubes while the Lithium
Bromide solution is on the shell side. Being more efficient, the exhaust gas leaving temperature is
lower than the smoke tube design.
The liquid tube design also has a lower volume of Lithium Bromide solution resulting in a faster
start-up time. It does not require any ceramic refractory compared to the conventional design,
resulting in increased reliability.
Low temperature generator (LTG)
The hot refrigerant vapor from the high temperature generator heats up the dilute solution coming
in from the low temperature heat exchanger. This vapor then condenses into hot refrigerant liquid
and is sent to the condenser through the drain heat exchanger. The additional vapor produced in
the LTG by heating up the dilute solution is sent to the condenser.
The LTG is of a falling film design, ensuring superior heat transfer and enhanced life by eliminating
wear and tear at the tube supports.
Condenser
The cooling water from the absorber section enters into the condenser section. This helps
condense the refrigerant vapors produced in the LTG as well as the condensed refrigerant from the
drain heat exchanger. The liquid refrigerant is then sent back to the evaporator section through a
U-pipe, or liquid seal.
This completes the cooling cycle.
Figure 4: Condenser
19YHAU-CGN/H Double Effect Direct Fired Absorption Chiller-Heater (Mod A)

Crystallization
All absorption chiller-heaters that use lithium bromide and water as the solution or the refrigerant
pair are subject to crystallization. This is due to the fact that some areas of the unit operate with
solution liquid concentration levels that are only possible at higher than the normal ambient
temperature surrounding the unit. For example, the solution concentration in the generator of a
single effect absorption unit is typically 64.3% lithium bromide by weight. LiBr begins to crystallize
at 43.3°C.
Crystallization is the result of the LiBr solution temperature going too low or the concentration too
high. The LiBr solution becomes like slush. At this point the LiBr solution cannot absorb any more
water and starts to solidify (crystallize).
Crystallization occurs in the solution heat exchanger and sometimes even in the generator. It also
occurs in pipes not well insulated where room temperature can affect the solution moving through
the pipes.
You can prevent crystallization by making sure you keep the solution temperature high and the
concentration at the optimum percentage (64%).
Since the solution temperature in the generator is normally high enough in most load conditions,
no crystallization occurs as long as the higher solution temperatures are maintained. Special
measures do have to be taken before the unit is shut down so that the solution is sufficiently
diluted in all areas of the unit to prevent crystallization during the off cycle, since the solution
temperature eventually equals the surrounding ambient temperature.
All units employ some sort of dilution cycle, which fulfills this requirement. As long as the unit
is allowed to dilute itself during an orderly shutdown sequence, the unit must be able to sit idle
at fairly low plant room ambient temperatures for extended periods of time without any threat
of crystallization. Typically, after a dilution cycle, the average solution concentration within the
chiller-heater is below 45% lithium bromide by weight and has no tendency to crystallize at normal
ambient temperatures.
Why crystallization occurs
The most common reason for crystallization is due to power failures. If a chiller-heater is running
at full load and power is interrupted for a sufficient length of time, the concentrated solution in
the high side of the unit, or the condenser section, eventually cools down. Since no dilution cycle
was performed, the solution concentration in some areas of the unit may still be relatively high. If
the temperature of this concentrated solution is allowed to fall low enough, the solution reaches
its crystallization point. Plant room temperature, insulation quality, and the solution concentration
all play a part in determining how long it takes before the unit crystallizes. See Maintenance for
information on water quality control and crystallization. The Duhring Diagram / PTX Chart shows
the specific temperatures and pressures of the crystallization area. See Figure 93 and Figure 94.
YHAU-CGN/H Double Effect Direct Fired Absorption Chiller-Heater (Mod A)20