Johnson Controls YORK YVAM 0350 Troubleshooting guide

Form Number: 160.88-OM1 (122)
New Release
Operation and Maintenance
Issue Date: 2022-01-14
YVAM Control Center
Centrifugal Liquid Chiller with R-134a Refrigerant

2 YVAM Control Center

Contents
ContentsGeneral safety guidelines................................................................................................................................7
Safety symbols....................................................................................................................................... 7
Changeability of this document...........................................................................................................8
Associated literature..............................................................................................................................8
Conditioned based maintenance.........................................................................................................8
Nomenclature........................................................................................................................................ 9
System fundamentals.................................................................................................................................... 11
System components............................................................................................................................11
Compressor.................................................................................................................................................12
Motor........................................................................................................................................................... 13
Heat exchangers........................................................................................................................................ 13
Evaporator...................................................................................................................................................13
Condenser...................................................................................................................................................13
Waterboxes................................................................................................................................................. 13
Refrigerant flow control............................................................................................................................ 13
Variable speed drive.................................................................................................................................. 14
Power panel................................................................................................................................................ 14
Optional service isolation valves.............................................................................................................. 14
OptiView control center.............................................................................................................................17
System operation description............................................................................................................ 19
Capacity control..........................................................................................................................................19
Anti-surge minimum frequency............................................................................................................... 20
Smart Freeze...............................................................................................................................................20
Surge protection.........................................................................................................................................21
System operating procedures...................................................................................................................... 22
Pre-starting...........................................................................................................................................22
Start-up................................................................................................................................................. 22
Chiller operation.................................................................................................................................. 23
Chilled liquid control settings.............................................................................................................23
Temperature control setpoint.................................................................................................................. 23
Automatic temperature shutdown.......................................................................................................... 25
Automatic temperature restart................................................................................................................ 25
Operator setpoints quick reference.................................................................................................. 25
Stopping the system............................................................................................................................26
Safety stop............................................................................................................................................ 26
Operating logs..................................................................................................................................... 26
Fault shutdowns...................................................................................................................................27
Performing prolonged shutdown......................................................................................................27
Restart after prolonged shutdown....................................................................................................27
Freeze damage protection..................................................................................................................27
Physical data.........................................................................................................................................29
YVAM Control Center 3

OptiView control center functions and navigation.................................................................................... 30
Display only.......................................................................................................................................... 30
Programmable..................................................................................................................................... 30
Access level................................................................................................................................................. 30
Change setpoints....................................................................................................................................... 30
Programming setpoints............................................................................................................................ 31
Manual controls......................................................................................................................................... 31
Free cursor..................................................................................................................................................31
Navigation............................................................................................................................................ 31
Languages............................................................................................................................................ 32
Analog input ranges............................................................................................................................32
OptiView screens................................................................................................................................. 34
Home screen...............................................................................................................................................34
System screen.............................................................................................................................................36
Evaporator screen......................................................................................................................................37
Condenser screen...................................................................................................................................... 39
Compressor screen....................................................................................................................................40
Magnetic bearing controller screen........................................................................................................ 42
Magnetic bearing controller details screen............................................................................................44
Surge screen...............................................................................................................................................46
Variable geometry diffuser screen.......................................................................................................... 48
Power panel screen................................................................................................................................... 49
Capacity control screen.............................................................................................................................51
Variable speed drive screen......................................................................................................................53
Variable speed drive (VSD) details screen...............................................................................................55
VSD cooling screen.................................................................................................................................... 57
Motor details screen..................................................................................................................................58
Setpoints screen.........................................................................................................................................60
Remote control screen.............................................................................................................................. 62
Setup screen............................................................................................................................................... 64
Schedule screen......................................................................................................................................... 66
User screen................................................................................................................................................. 68
Comms screen............................................................................................................................................69
Printer screen............................................................................................................................................. 70
Sales order screen......................................................................................................................................71
Operations screen......................................................................................................................................72
History screen.............................................................................................................................................73
History details screen................................................................................................................................ 74
Custom screen............................................................................................................................................75
Custom setup screen.................................................................................................................................76
Trend screen............................................................................................................................................... 77
Trend setup screen.................................................................................................................................... 79
Common slots screen................................................................................................................................82
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Master slot numbers list.....................................................................................................................83
Display messages................................................................................................................................ 88
Status messages........................................................................................................................................ 88
Run messages............................................................................................................................................ 89
MBC startup messages..............................................................................................................................90
Start inhibit messages...............................................................................................................................90
Warning messages.................................................................................................................................... 90
Routine shutdown messages................................................................................................................... 93
Cycling shutdown messages.................................................................................................................... 94
Safety shutdown messages.................................................................................................................... 101
Drive operation.............................................................................................................................................111
OptiSpeed compressor drive overview...........................................................................................111
OptiSpeed compressor drive features............................................................................................111
Smart sensor system.........................................................................................................................112
OptiSpeed compressor drive details (0490B amp drive).............................................................. 114
Harmonic filter benefits.......................................................................................................................... 114
Harmonic filter general information..................................................................................................... 115
OptiSpeed compressor drive and chiller operation (0490B amp models)................................. 120
Maintenance................................................................................................................................................. 121
Preventative maintenance................................................................................................................121
Renewal parts.................................................................................................................................... 122
Operating inspections.......................................................................................................................122
Weekly....................................................................................................................................................... 122
Monthly..................................................................................................................................................... 122
Semi-annually...........................................................................................................................................122
Annually.....................................................................................................................................................123
Checking system for leaks................................................................................................................123
Leak testing...............................................................................................................................................123
Vapor connection locations.................................................................................................................... 123
System pressure test.........................................................................................................................124
Conducting the gas pressure hold test.................................................................................................125
Conducting the soap visual gas leak test..............................................................................................126
Conducting the optional trace gas leak test.........................................................................................127
System evacuation.............................................................................................................................128
Vacuum dehydration.........................................................................................................................128
Conducting the dehydration process....................................................................................................131
Conducting the final evacuation............................................................................................................ 131
Refrigerant charging.........................................................................................................................132
Removing the refrigerant charge for service....................................................................................... 134
Checking and trimming the refrigerant charge...................................................................................135
Checking the refrigerant charge during unit shutdown.....................................................................135
Compressor and motor maintenance.............................................................................................135
Evaporator maintenance.................................................................................................................. 136
5YVAM Control Center

Chemical water treatment...................................................................................................................... 136
Cleaning evaporator tubes..................................................................................................................... 137
Tube fouling..............................................................................................................................................137
Tube cleaning procedures...................................................................................................................... 137
Evaporator tube leaks............................................................................................................................. 138
Testing for evaporator tube leaks..........................................................................................................138
Condenser maintenance.................................................................................................................. 139
Cleaning requirements of microchannel heat exchangers................................................................ 139
Cleaning Standard and Environment Guard MCHX coils....................................................................139
Cleaning Environment Guard Premium MCHX coils............................................................................140
Electrical controls...............................................................................................................................140
Unit heater operation verification...................................................................................................140
Testing evaporator waterbox heaters WBH1 and WBH2....................................................................141
Testing evaporator shell heaters EVH1 and EVH2................................................................................141
Testing heat trace for drive coolant HT1 and HT2............................................................................... 141
Testing the VGD actuator heater mat....................................................................................................142
Testing the MBC heater mat...................................................................................................................142
Testing the drive internal heater............................................................................................................142
Testing the OptiView control panel heater........................................................................................... 143
Testing the OptiView control panel cooler............................................................................................144
Testing UPS panel heating......................................................................................................................145
Automatic battery health test during shutdown...........................................................................145
Printing..........................................................................................................................................................147
Printing overview...............................................................................................................................147
Acceptable printers........................................................................................................................... 147
OKI Data.................................................................................................................................................... 148
Brecknell....................................................................................................................................................149
Control center setup......................................................................................................................... 150
Downloading system prints to a laptop..........................................................................................151
Unit conversion............................................................................................................................................ 162
YVAM Control Center6

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 improperly,
to cause bodily injury or death. It is the obligation and responsibility of rigging, installation, and
operating/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/service
personnel. It is expected that these individuals possess independent training that will enable them
to perform their assigned tasks properly and safely. It is essential that, prior to performing any
task on this equipment, this individual shall have read and understood the on-product labels, this
document and any referenced materials. This individual shall 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.
7YVAM Control Center

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 owner. Updated
manuals, if applicable, can be obtained by contacting the nearest Johnson Controls Service office or
accessing the Johnson Controls Knowledge Exchange website at https://docs.johnsoncontrols.com/
chillers/.
Operating/service personnel maintain responsibility for the applicability of these documents to the
equipment. If there is any question regarding the applicability of these documents, the technician
should verify whether the equipment has been modified and if current literature is available from
the owner of the equipment prior to performing any work on the chiller.
Associated literature
Table 1: Associated literature
Manual description Form number
Installation and Reassembly 160.88-N1
Unit Installation Checklist and Request for Startup 160.88-CL1
Unit Startup Checklist 160.88-CL2
Field Connections Diagram 160.88-PW1
Field Control, Wiring, and MBC Diagrams 160.88-PW2
Centrifugal Chiller Long Term Storage 50.20-NM5
All Products - Replacement Parts Electrical Connectors 50.20-RP1
All Products - Replacement Parts Fittings 50.20-RP2
Conditioned based maintenance
Traditional chiller maintenance is based upon assumed and generalized conditions. In lieu of
the traditional maintenance program, a Johnson Controls YORK Conditioned Based Maintenance
(CBM) program can be substituted. This CBM service plan is built around the specific needs for
the chiller, operating conditions, and annualized impact realized by the chiller. Your local Johnson
Controls Branch can propose a customized Planned Service Agreement that leverages real time
and historical data, delivering performance reporting, corrective actions required and data enabled
guidance for optimal operation and life cycle assurance. The program will include fault detection
diagnostics, operation code statistics, performance based algorithms and advance rules based
rationale delivered by the Johnson Controls Connected Equipment Portal.
YVAM Control Center8

Nomenclature
Figure 1: System nomenclature
Figure 2: Compressor nomenclature
Figure 3: Vessel nomenclature
9YVAM Control Center

Figure 4: Variable speed drive nomenclature
YVAM Control Center10

System fundamentals
The following section contains information about the system components and operation of the
YORK® Model YVAM™ Centrifugal Liquid Chiller.
System components
The YORK Model YVAM Centrifugal Liquid Chiller is completely factory-packaged and includes the
following components:
• Evaporator
• Condenser
• Condenser fans
• Condenser fan variable speed drives
• Compressor
• Motor
• Variable speed drive (VSD)
• Battery power panel
• OptiView™ Control Center
• All interconnecting unit piping and wiring
See Figure 5, Figure 6, and Figure 7 for YVAM chiller components.
Figure 5: Control panel side view
Callout Component Callout Component
A Control panel B Signal box for condenser fan variable speed
drive, typical both sides
C Condenser sections, typically ten with two fans
each
D Evaporator water nozzles, inlet at the bottom
and outlet at the top
E Waterbox heater power connections F UPS power panel
11YVAM Control Center

Figure 6: Compressor side view
Callout Component Callout Component
A Evaporator B Motor cooling filter drier
C Expansion valve D Cooling piping for variable speed drive
E Eaton® surge suppressor F Direct drive motor and MBC
G Compressor
Figure 7: Variable speed drive end view
Callout Component Callout Component
A Variable speed drive B UPS power panel
C Single point power panel
Compressor
The compressor is a single-stage centrifugal type powered by a hermetic electric motor, on a
common shaft with a cast aluminum, fully shrouded impeller. The compressor has no inlet guide
vanes and uses a variable geometry diffuser (VGD) for capacity control.
YVAM Control Center12

Motor
The compressor motor is a hermetic permanent magnet high-speed design with magnetic
bearings. The compressor impeller is overhung from the end of the motor shaft and has no
bearings of its own.
The motor includes angular contact ball bearings only engaged with the rotor shaft during
shutdown after rotation is stopped or during shutdown due to loss of power to the magnetic
bearings.
The bearing control center maintains correct shaft position in the magnetic bearings.
Heat exchangers
The evaporator shell is fabricated from rolled carbon steel plates with fusion welded seams. Heat
exchanger tubes are internally enhanced type.
Evaporator
The evaporator is a shell and tube, hybrid falling film, and flooded type heat exchanger. A
distributor trough provides uniform distribution of refrigerant over tubes in the falling film section.
Residual refrigerant floods the tubes in the lower section. Suction baffles are located above the
tube bundle to prevent liquid refrigerant carryover into the compressor. A 2 in. liquid level sight
glass is located on the side of the shell. The evaporator shell contains dual refrigerant relief valves.
Condenser
The 10 condenser sections are microchannel design and consist of a tube and fin design. Each
condenser section has two cooling fans that are speed controlled from the chiller control panel
and use VSD technology to operate the fans. Refrigerant sub-cooling is accomplished in the
condenser section. Refrigerant relief valves are located on the system discharge piping that feeds
the condenser sections with refrigerant isolation valves as standard options.
Waterboxes
The removable compact waterboxes are fabricated of steel. The design working pressure is 150
psig (1,034 kPa) and the boxes are tested at 225 psig (1,551 kPa). Integral steel water baffles
provide the required pass arrangements. Stub-out water nozzle connections with grooved
connections, which are a standard option, are welded to the waterboxes. These nozzle connections
are suitable for groove type couplings, welding, or flanges, and are capped for shipment. Plugged
3/4 in. drain and vent connections are provided in each waterbox.
Refrigerant flow control
Refrigerant flow to the evaporator is controlled by the condenser drain valve. The control panel
monitors the condenser subcooling value as the control point for the condenser drain valve.
Under program control, the control panel modulates the condenser drain valve to control the
condenser refrigerant level to the programmed subcooling setpoint. Other setpoints modify the
control sensitivity and response. Only a qualified service technician can change these settings. The
subcooling setpoint must be verified at chiller commissioning by a qualified service technician.
While the chiller is shut down, the condenser drain valve is pre-positioned to anticipate run. When
the chiller is started, if the subcooling value is less than the setpoint, a linearly increasing ramp is
applied to the subcooling setpoint. This ramp causes the setpoint to go from the initial subcooling
value to the programmed setpoint over a programmable period of time. If the actual subcooling
value is greater than the setpoint upon run, it immediately begins to control to the programmed
setpoint.
While the chiller is running, the refrigerant level is normally controlled to the subcooling setpoint.
13YVAM Control Center

Variable speed drive
The variable speed drive is factory packaged with the chiller. It is designed to vary the compressor
motor speed by controlling the frequency and voltage of the electrical power to the motor. The
control logic automatically adjusts motor speed as required to suit lift and capacity requirements.
Power panel
The power panel includes the uninterrupted power supply and power storage battery. These work
together to feed essential electrical loads if the chiller shuts down due to the loss of main chiller
power.
Optional service isolation valves
Optional service isolation valves include two on the discharge lines to each condenser section
and one on the liquid line to the evaporator. If your chiller is equipped with these optional service
isolation valves, they must remain fully open during operation. These valves are used for isolating
the refrigerant charge in the condenser to allow service access to the evaporator and compressor
side of the system. A refrigerant recovery unit is required to isolate the refrigerant.
CAUTION
Isolation of the refrigerant in this system must be performed by a qualified service technician.
YVAM Control Center14

Figure 8: System piping and instrumentation diagram (P&ID)
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Table 2: Legend for system piping and instrumentation diagram
Device Description
ABV-1 Actuated butterfly valve - VSD cooling valve
EEV-1 Condenser liquid line drain valve - motorized butterfly valve
FS-1 Evaporator water flow switch
FST-1 Fluid strainer - VSD cooling strainer
HPS-1 Compressor high pressure cut-out switch
HTR-1 Cartridge heater - evaporator on waterbox
HTR-2 Cartridge heater - evaporator off waterbox
HTR-3 Evaporator to VSD water supply heater 1
HTR-4 Evaporator to VSD water supply heater 2
PE-1 Evaporator pressure sensor - OV
PE-2 Discharge line pressure sensor - OV
PE-3 Condenser liquid line pressure sensor - OV
PE-4 Suction pressure sensor - OV
PSV-1 Pressure safety valve - evaporator
PSV-2 Discharge line pressure safety valve - condenser section 1
PSV-3 Discharge line pressure safety valve - condenser section 2
PSV-4 Condenser liquid line pressure safety valve
PSV-5 Condenser liquid line pressure safety valve - condenser section 1
PSV-6 Condenser liquid line pressure safety valve - condenser section 2
PUMP-1 Coolant pump - VSD
PUMP-2 Coolant pump - power panel
QDDB-1 Quick disconnect dry break - power panel on coolant
QDDB-2 Quick disconnect dry break - power panel off coolant
SST-1 Educator strainer
SST-2 Motor cooling liquid supply strainer
SV-1 Discharge service valve - condenser section 1
SV-2 Discharge service valve - condenser section 2
TE-1 Evaporator water on thermistor
TE-2 Evaporator water off thermistor
TE-3 Discharge line temperature sensor - OV
TE-4 Motor housing temperature thermistor
TE-5 Evaporator refrigerant temperature thermistor
TE-6 Condenser liquid line temperature thermistor
V-1 Ball valve - evaporator water on VSD cooling
V-2 Ball valve - evaporator water off VSD cooling
V-3 Ball valve - VSD cooling glycol valve
V-4 Angle valve, power panel coolant
V-5 Angle valve, evaporator pressure sensor
V-6 Service valve - motor cooling educator suction
V-7 Educator motive solenoid valve
V-8 Service valve - motor cooling educator discharge
V-9 Discharge isolation valve - condenser section 1
V-10 Discharge isolation valve - condenser section 2
V-11 Service valve - discharge line pressure sensor
V-12 Condenser liquid line service angle valve
V-13 Condenser liquid line service isolation valve - condenser section 1
V-14 Condenser liquid line service isolation valve - condenser section 2
V-15 Condenser liquid line service valve - condenser section 1
V-16 Condenser liquid line service valve - condenser section 2
V-17 Condenser liquid line pressure transducer isolation valve
V-18 Compressor motor cooling isolation valve 1
V-19 Compressor motor cooling isolation valve 2
V-20 Angle valve, suction sensor pressure
YVAM Control Center16

OptiView control center
The YORK OptiView control center LCD graphic display and keypad is the interface for starting,
stopping, configuring, monitoring, and commanding the chiller controls. The control center
is a microprocessor-based system for centrifugal chillers. It controls the leaving chilled liquid
temperature (LCHLT) and maintains safe operation. It is factory-mounted, wired, and tested.
The graphic display presents the operating parameters in logical groups on screens and can
trend data to show a graphical representation of present or historical operation of the chiller. The
locations of various chiller parameters are clearly and intuitively marked. Instructions for specific
operations are provided on many of the screens. For information on the screens and navigation,
see OptiView control center functions and navigation.
Eight buttons on the right side of the panel are primarily used for navigation between the system
screens. Five additional buttons are located at the base of the display. The button functions are
redefined based on the currently displayed screen. The area to the right of the keypad is used for
data entry and a standard numeric keypad is provided for programming system setpoints and
limits.
Figure 9: OptiView control center
Table 3: OptiView™ control center buttons
Button Description
The decimal button provides accurate entry of setpoint values.
Use the ± button to enter negative values and select AM/PM during
time entry.
In order to accept changes made to the chiller setpoints, the check
button is provided as a universal Enter button or Accept symbol.
In order to reject entry of a setpoint or dismiss an entry form, the X
button is provided as a universal Cancel symbol.
Cursor arrow buttons are provided to allow movement on screens that
contain a large amount of entry data. In addition, these buttons can be
used to scroll through history and event logs.
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The graphic display also allows numerical information to be represented in both English
(temperatures in °F and pressures in psig) and Metric (temperatures in °C and pressures in kPa)
mode. It can also display many languages.
The control center continually monitors the system operation and records the cause of any
shutdowns (Safety, Cycling, or Normal). This information is recorded in memory and is preserved
even through a power failure condition. The user can recall it for viewing at any time. During
operation, the user is continually advised of the operating conditions by various status and warning
messages. In addition, it can be configured to notify the user of certain conditions using alarms. A
complete listing of shutdown, status, and warning messages is provided in Display messages.
The control center includes capabilities for remote control and communications. Common
networking protocol through the Building Automation System (BAS) allows increased remote
control of the chiller, including 24-hour performance monitoring by a remote site. An optional
circuit board called the SC-EQUIP provides Johnson Controls and YORK mechanical equipment such
as the YVAM chiller with BAS networking connectivity.
The chiller also maintains the standard digital remote capabilities. Both of these remote control
capabilities allow for the following standard Energy Management System (EMS) interfaces. The
actual connection details are in the Field Connections section of the Wiring Diagram (Form 160.88-
PW1 and 160.88-PW3):
• Remote start
• Remote stop
• Remote Leaving Chilled Liquid Temperature setpoint adjustment: BAS coms, Analog signal,
(0 VDC to 10 VDC, 2 VDC to 10 VDC, 0 mA to 20 mA, or 4 mA to 20 mA), or pulse width
modulation (PWM)
• Remote Current Limit setpoint adjustment: BAS coms, Analog signal, (0 VDC to 10 VDC, 2 VDC
to 10 VDC, 0 mA to 20 mA, or 4 mA to 20 mA), or pulse width modulation
• Remote ready to start contacts
• Safety shutdown contacts
• Cycling shutdown contacts
The OptiView panel can be used to control the customer chilled and condenser liquid flow. A set
of contacts exists to initiate flow for each shell. Details are in the Field Connections section of
the Wiring Diagram (Form 160.88-PW2 and 160.88-PW4). The chilled water pump contacts close
immediately upon execution of a chiller start command. They open coincident with the receipt of a
stop command or a fault other than the following faults:
1. LEAVING CHILLED LIQUID - LOW TEMPERATURE cycling shutdown.
2. MULTIUNIT CYCLING - CONTACTS OPEN or SYSTEM CYCLING - CONTACTS OPEN (Only if
Chilled Liquid Pump Operation is set to Enhanced)
3. LEAVING CHILLED LIQUID FLOW SWITCH OPEN cycling shutdown
The condenser pump contacts close immediately upon execution of a chiller start command. They
open coincident with receipt of a chiller stop command or fault other than CONDENSER-FLOW
SWITCH OPEN cycling shutdown.
If the chiller is stopped and the condenser pump contacts are open (flow off), the contacts close
when saturated condenser temperature is less than 35.0°F (1.67°C). This helps mitigate condenser
freeze due to plant issues in brine applications.
If the contacts are closed only due to the saturated condenser temperature, they are opened when
saturated condenser temperature returns above 40.0°F (4.44°C). If the existing logic calls for them
to be closed, they remain closed.
YVAM Control Center18

Some screens, displayed values, programmable setpoints, and manual controls exist for service
technician use only. They are only displayed when logged in at Service access level or higher. The
setpoints and parameters displayed on these screens are explained in detail in YORK YVAM Service
Manual (Form 160.88-M2). These parameters affect chiller operation and must never be modified by
anyone other than a qualified service technician. The advanced diagnostics and troubleshooting
information for service technicians is included in YORK YVAM Service Manual (Form 160.88-M2). Also
included in the Service manual are detailed descriptions of chiller features, such as capacity control,
refrigerant level control, variable geometry diffuser, and magnetic bearing controller.
The chiller operating program resides in the OptiView Control Center microboard. Software
versions (C.OPT.20.xx.yzz) are alphanumeric codes that represent the application, language
package, and revision levels as follows. Each time the controls portion or language section is
revised, the respective revision level increments.
•C: Commercial chiller
•OPT: OptiView
•20: Chiller model (for example, YVAM)
•xx: Controls revision level (for example, 00, 01)
•y: Language package (0=English only, 1=NEMA, 2=CE, 3=NEMA/CE )
•zz: Language package revision level (for example, 00, 01)
Software upgrades must only be performed by a service technician.
System operation description
In operation, a liquid to be chilled (water or brine) flows through the evaporator tubes, where its
heat is transferred to low pressure liquid refrigerant sprayed over and pooled outside the tubes,
boiling the refrigerant. The chilled liquid is then piped to air conditioning or process terminal units,
absorbing heat. The warmed liquid is then returned to the chiller to complete the chilled liquid
circuit cycle.
The refrigerant vapor that is produced by the boiling action in the evaporator is drawn into the
suction of the compressor. The rotating impeller increases its pressure and temperature and
discharges the vapor into the condenser. Cooling air flowing through the condenser sections
absorbs heat from the refrigerant vapor and causes it to condense. The cooling air is always
at ambient conditions and requires correct installation for reliable operation. The condensed
refrigerant drains from the condenser into the evaporator liquid line and is controlled by the
condenser drain valve. This control valve causes the condensed liquid to stack in the lower portions
of the condensing sections creating the subcooling effect. The condenser drain valve meters the
flow of liquid refrigerant to the evaporator to complete the refrigerant circuit. The condenser
drain valve continually adjusts position as load changes to meet the changed mass flow rate of
refrigerant required to keep the system balanced. It does this by maintaining a constant subcooling
temperature, enough to maintain a liquid seal to the condenser liquid outlet.
Capacity control
The major components of a chiller are selected to handle the required refrigerant flow at full load
design conditions. However, most systems are required to deliver full load capacity for a relatively
short time while the unit is in operation. A means exists to modulate capacity for other loads.
The speed at which the compressor rotates establishes the pressure differential that the chiller can
operate against. This is referred to as lift. Speed must always be maintained above the minimum
necessary to create the lift required for the pressure difference between the condenser and
evaporator, regardless of load. Below that speed, gas surge occurs. That pressure difference is a
function of the LCHLT and the condensing temperature and the heat transfer between those two
systems and the refrigerant.
19YVAM Control Center

Reduced speed also reduces the available capacity of the chiller, when speed reduction is possible.
If speed is reduced, the chiller power use is reduced. As a result, at reduced capacity requirements
where condenser pressure is also reduced, the motor speed is reduced as much as possible
while maintaining chilled liquid temperature and sufficient lift. When the speed cannot be further
reduced due to lift required for the specified leaving chilled water temperature setting and
available cooling to the condenser and capacity must be further reduced, a mechanism called
variable geometry diffuser (VGD) at the exit of the impeller is used to reduce refrigerant gas flow.
The VGD not only controls capacity, but serves to mitigate stall. Stall is an effect caused by slow
refrigerant gas passing through the compressor at reduced flow rates needed for low capacity
operation.
The YVAM chiller uses these mechanisms in a controlled order to maintain best efficiency.
The YVAM chiller controls capacity by adjusting the compressor VGD position, the compressor
motor variable speed drive, and optional hot gas bypass valve (HGBP) position, if equipped, in
a specific sequence depending on whether loading or unloading is required to keep Leaving
Chilled Liquid Temperature at setpoint. Motor speed is additionally and simultaneously adjusted as
necessary to maintain the minimum compressor lift required to prevent surge. The sequence for
operation of the control devices to achieve the best chiller efficiency is as follows:
• Conditions that require capacity increase: HGBP, if present, is driven toward closed. When
the HGBP is fully closed, the VGD is driven toward open. Then when the VGD is fully open, the
speed of the variable speed drive is increased.
• Conditions that require capacity decrease: The drive speed is decreased to the minimum
speed for the lift required. When the drive speed is at the minimum limit to avoid surge for
the lift, the VGD is driven toward closed. When the VGD reaches closed or the minimum
position allowed for the operating condition, the HGBP, if present, is driven toward open.
Also, High Condenser Pressure, Low Evaporator Pressure, High Motor Current, and High Input
Current limits and overrides limit or reduce the output to the appropriate devices (HGBP, VGD, or
variable speed drive) to mitigate the condition to keep the chiller online. When any of these physical
thresholds are approached, the control proportionally limits the amount of capacity increase
permitted. If exceeded, it issues unloading into the capacity control command.
Anti-surge minimum frequency
In order to maintain sufficient compressor lift to overcome condenser pressure and prevent surge
throughout operation, the control maintains and continuously updates a minimum limit for VSD
speed. This limit is the Active Anti-Surge Minimum Frequency. It is calculated and applied to the
speed each cycle of the capacity control routine.
Smart Freeze
The Smart Freeze feature prevents nuisance chiller shutdowns due to brief periods of chilled liquid
flow fluctuations or other brief operating conditions that would normally cause Low Evaporator
Pressure Safety shutdowns. With this feature enabled and activated, the chiller can ride through
these temporary conditions. Also, this feature allows the Leaving Chilled Liquid Temperature
Setpoint to be set as low as 36.0ºF (2.2ºC). Smart Freeze protection can be enabled or disabled at
the keypad by a service technician. It cannot be used in brine cooling mode.
Smart Freeze protection uses the Evaporator Refrigerant Temperature as one of the variables to
determine when freezing is imminent. The basis of this feature is that the chilled liquid contains an
amount of heat that cannot be eliminated immediately. As a result, it requires a certain amount of
time for the liquid to change to a solid. During this period of time, those parameters that determine
when solidification occurs are evaluated and the shutdown is based on accumulated time below the
freeze temperature.
YVAM Control Center20