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CENTRIFUGAL LIQUID CHILLER
WITH ECONOMIZER COMPRESSOR
CONTROL CENTER OPERATION Form 160.77-02 (611) Form 160.77-02 (1111)
R-134a
Issue Date:
November 15, 2011
MODEL YKEP
2700 - 3200 TON
LD15301a
FORM 160.77-O2
ISSUE DATE: 11/15/2011
JOHNSON CONTROLS
2
This equipment is a relatively complicated apparatus.
During installation, operation maintenance or service,
individuals may be exposed to certain components or
conditions including, but not limited to: 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 respon-
sibility of 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
IMPORTANT!
READ BEFORE PROCEEDING!
GENERAL SAFETY GUIDELINES
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
operating/service personnel. It is expected that these
individuals possess independent training that will en-
able 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 this document and any referenced mate-
rials. This individual shall also be familiar with and
comply with all applicable 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:
Indicates a possible hazardous situation
which will result in death or serious injury
if proper care is not taken.
Indicates a potentially hazardous situa-
tion which will result in possible injuries
or damage to equipment if proper care is
not taken.
Identies a hazard which could lead to
damage to the machine, damage to other
equipment and/or environmental pollu-
tion if proper care is not taken or instruc-
tions and are not followed.
Highlights additional information useful
to the technician in completing the work
being performed properly.
External wiring, unless specied as an optional connection in the manufacturer’s product line, is
not to be connected inside the control panel cabinet. Devices such as relays, switches, transducers
and controls and any external wiring must not be installed inside the control panel. All wiring must
be in accordance with Johnson Controls’ published specications and must be performed only by
a qualied 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.
FORM 160.77-O2
ISSUE DATE: 11/15/2011
JOHNSON CONTROLS
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CHANGEABILITY OF THIS DOCUMENT
In complying with Johnson Controls’ policy for con-
tinuous product improvement, the information con-
tained 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.
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 litera-
ture is available from the owner of the equipment prior
to performing any work on the chiller.
ASSOCIATED LITERATURE
NOMENCLATURE
MANUAL DESCRIPTION FORM NUMBER
YKEP Installation & Re-assembly 160.77-N1
YKEP Unit Operation & Maintenance 160.77-O1
YKEP Control Center Operation 160.77-O2
YKEP Unit & Control Panel Renewal Parts 160.77-RP1
YKEP Installation Checklist 160.77-CL1
YKEP Startup Checklist 160.77-CL2
YKEP Wiring Diagram - Field Connections 160.77-PW1
YKEP Wiring Diagram - Unit Wiring and Field Control Modication 160.77-PW2
Liquid Cooled Solid State Starter - Operation 160.00-O2
Medium Voltage Variable Speed Drive (2300v - 6600v) - Operation 160.00-O6
Medium Voltage Variable Speed Drive (10,000v - 13,800v) - Operation 160.00-O8
Unit Mounted Medium Voltage Solid State Starter (2300v - 4160v) - Operation 160.00-O7
Long-Term Storage Requirements - General 50.20-NM1
Long-Term Storage Requirements - Field Preparation 50.20-NM5
Long-Term Storage - Periodic Checklist and Logs 50.20-CL5
* For both Primary and Economizer power supply: “-” = 60Hz and “5” = 50Hz
Primary Motor
Primary Power Supply *
Economizer Compressor
Primary Compressor
Economizer Motor
Economizer Power Supply *
Condenser
Modification LevelEvaporator
Special FeaturesModel
YKEP BD B5 K7 Q3 DL CF5 A S
-
LD15116
FORM 160.77-O2
ISSUE DATE: 11/15/2011
JOHNSON CONTROLS
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THIS PAGE INTENTIONALLY LEFT BLANK
FORM 160.77-O2
ISSUE DATE: 11/15/2011
JOHNSON CONTROLS
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TABLE OF CONTENTS
LIST OF TABLES
TABLE 1 - YKEP Control System Sensors .............................................................................................................18
TABLE 2 - Trend Pen Assignments .........................................................................................................................92
TABLE 3 - Modbus RTU Slot List ............................................................................................................................93
TABLE 4 - Status Line Messages and Colors ....................................................................................................... 109
TABLE 5 - LCSSS High Supply Line Voltage Thresholds ..................................................................................... 118
TABLE 6 - LCSSS Low Supply Line Voltage Thresholds ......................................................................................118
TABLE 7 - Over-Current Trip .................................................................................................................................123
SECTION 1 - YKEP CHILLER OVERVIEW ..............................................................................................................7
SECTION 2 - YKEP CONTROL CENTER INTRODUCTION ..................................................................................17
SECTION 3 - YKEP CONTROL PANEL OPERATION ........................................................................................... 21
Home Screen .................................................................................................................................................25
System Screen ...............................................................................................................................................28
Manual / Auto Stations Screen .......................................................................................................................32
Subcooler Screen ........................................................................................................................................... 34
Economizer Screen ........................................................................................................................................36
Evaporator Screen .........................................................................................................................................38
Hot Gas Screen .............................................................................................................................................. 40
Condenser Screen .........................................................................................................................................42
Primary Compressor Screen ..........................................................................................................................44
Primary Proximitor Calibration Screen ...........................................................................................................48
PRV Calibration Screen.................................................................................................................................. 50
Oil Sump Screen ............................................................................................................................................52
Primary Variable Geometry Diffuser Screen ...................................................................................................54
Primary Motor Screen (EM Starter) ................................................................................................................ 56
Primary Motor Screen (MV SSS) ...................................................................................................................58
Primary Motor Screen (MV VSD) ...................................................................................................................60
Capacity Controls Screen with Hot Gas (Fixed Speed) .................................................................................62
Capacity Controls Screen without Hot Gas (Fixed Speed) ............................................................................64
Capacity Controls Screen (Speed Option) .....................................................................................................66
Capacity Controls Screen (Vane Anti-Surge) .................................................................................................68
Primary Capacity Tuning Screen .................................................................................................................... 70
Primary Anti-Surge Screen ............................................................................................................................. 72
Capacity Limits Screen ...................................................................................................................................74
Economizer Compressor Screen ...................................................................................................................76
Economizer Motor LCSSS Screen .................................................................................................................78
Economizer Capacity Screen .........................................................................................................................80
Setpoints Screen ............................................................................................................................................82
Factory Setup Screen .....................................................................................................................................84
Comms Screen ...............................................................................................................................................86
Alarm History Screen .....................................................................................................................................88
Active Alarms Screen ..................................................................................................................................... 89
Trip Status Screen ..........................................................................................................................................90
Trending Screen ............................................................................................................................................. 91
SECTION 4 - MODBUS RTU SLOT LIST ...............................................................................................................93
SECTION 5 - DISPLAY MESSAGES .................................................................................................................... 109
FORM 160.77-O2
ISSUE DATE: 11/15/2011
JOHNSON CONTROLS
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FIGURE 1 - YKEP System Component Identication ...............................................................................................7
FIGURE 2 - YKEP Chiller System Diagram ..............................................................................................................8
FIGURE 3 - YKEP Chiller Operation Sequence Timing Diagram .............................................................................. 9
FIGURE 4 - YKEP Chiller Oil Management System ................................................................................................ 11
FIGURE 5 - Capacity Control Model .......................................................................................................................13
FIGURE 6 - System Anti-Surge Map ....................................................................................................................... 15
FIGURE 7 - Logic Controller....................................................................................................................................17
FIGURE 8 - Control Panel ....................................................................................................................................... 17
FIGURE 9 - YKEP Control System Sensors ...........................................................................................................19
FIGURE 10 - Red Lion Touch-Screen Display ........................................................................................................21
FIGURE 11 - Security Manager ...............................................................................................................................22
FIGURE 12 - Username ..........................................................................................................................................22
FIGURE 13 - Password ........................................................................................................................................... 22
FIGURE 14 - Setpoint Program Dialog Box ............................................................................................................23
FIGURE 15 - Menu Screen .....................................................................................................................................23
FIGURE 16 - Navigation ..........................................................................................................................................24
FIGURE 17 - Home Screen .....................................................................................................................................25
FIGURE 18 - System Screen ..................................................................................................................................28
FIGURE 19 - Manual / Auto Stations Screen ..........................................................................................................32
FIGURE 20 - Subcooler Screen ..............................................................................................................................34
FIGURE 21 - Economizer Screen ...........................................................................................................................36
FIGURE 22 - Evaporator Screen .............................................................................................................................38
FIGURE 23 - Hot Gas Screen .................................................................................................................................40
FIGURE 24 - Condenser Screen .............................................................................................................................42
FIGURE 25 - Primary Compressor Screen .............................................................................................................44
FIGURE 26 - Primary Proximity Calibration Screen ................................................................................................ 48
FIGURE 27 - PrV Calibration Screen ......................................................................................................................50
FIGURE 28 - Oil Sump Screen................................................................................................................................52
FIGURE 29 - Primary variable Geometry Diffuser Screen ......................................................................................54
FIGURE 30 - Primary Motor Screen (EM Starter) ...................................................................................................56
FIGURE 31 - Primary Motor Screen (MV SSS) .......................................................................................................58
FIGURE 32 - Primary Motor Screen (MV VSD) .......................................................................................................60
FIGURE 33 - Capacity Controls Screen (Fixed Speed with Hot Gas) .....................................................................62
FIGURE 34 - Capacity Controls Screen (Fixed Speed without Hot Gas) ................................................................64
FIGURE 35 - Capacity Controls Screen (Speed Option).........................................................................................66
FIGURE 36 - Capacity Controls Screen (Vane Anti-Surge) ..................................................................................... 68
FIGURE 37 - Primary Capacity Tuning Screen .......................................................................................................70
FIGURE 38 - Primary Anti-Surge Screen ................................................................................................................72
FIGURE 39 - Capacity Limits Screen ...................................................................................................................... 74
FIGURE 40 - Economizer Compressor Screen .......................................................................................................76
FIGURE 41 - Economizer Motor LCSSS Screen ....................................................................................................78
FIGURE 42 - Economizer Capacity Screen ............................................................................................................80
FIGURE 43 - Setpoints Screen ...............................................................................................................................82
FIGURE 44 - Factory Setup Screen ........................................................................................................................ 84
FIGURE 45 - Comms Screen .................................................................................................................................. 86
FIGURE 46 - Alarm History Screen ......................................................................................................................... 88
FIGURE 47 - Active Alarms Screen ......................................................................................................................... 89
FIGURE 48 - Trip Status Screen .............................................................................................................................90
FIGURE 49 - Trending Screen ................................................................................................................................91
FIGURE 50 - System Status / System Details.......................................................................................................109
LIST OF FIGURES
FORM 160.77-O2
ISSUE DATE: 11/15/2011
JOHNSON CONTROLS
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11
CHILLER PRINCIPLE OF OPERATION
The YKEP chiller (Figure 1 on Page 7) consists
of the components of a standard high pressure single
stage centrifugal chiller plus the addition of a flash
economizer and a secondary compressor to draw flash
gas from the economizer when required and discharge
to the condenser. The secondary compressor is referred
to as the economizer compressor. A system diagram is
shown in Figure 2 on Page 8.
The chiller operates in three configurations depending
on the lift required and the load.
1. The primary compressor can operate indepen-
dently with the economizer off, drawing suction
from the evaporator, discharging to the condenser,
with condensed liquid return to the evaporator via
ow through the idle economizer. The discharge
of the economizer compressor includes a check
valve to prevent backow from the condenser to
the economizer vessel in this operating mode.
2. When the calculated gas ow through the primary
compressor reaches a prescribed threshold as fol-
lows, the economizer compressor start is initiated.
The economizer compressor draws suction from
the economizer vessel and discharges to the con-
denser. The economizer compressor capacity is
controlled to maintain the economizer pressure at
a target value between the condenser and evapo-
rator pressures. In this mode the chiller is econo-
mizing to gain refrigeration effect for the primary
compressor and improve efciency.
Economizer compressor start criteria:
Primary Compressor Calculated Flow ≥ Flow Target de-
fined as a straight line between the points.
• Saturation Pressure of Subcooled Liquid - Evapo-
rator pressure = 64 PSID: 6000 CFM Required
• Saturation Pressure of Subcooled Liquid - Evapo-
rator Pressure = 30 PSID: 8200 CFM Required
Additionally:
• The Economizer Liquid Level must be below 90%
• The Leaving Chilled Liquid Temperature is not be-
low Setpoint
• The Economizer Saturation Temperature is not
below the Target Temperature
FIGURE 1 - YKEP SYSTEM COMPONENT IDENTIFICATION
LD15301
EVAPORATOR
CONDENSER
PRIMARY (K7)
COMPRESSOR
PRIMARY
OPEN-DRIVE
MOTOR
ECONOMIZER
OPEN-DRIVE
MOTOR
CONTROL
CENTER
ECONOMIZER (Q3)
COMPRESSOR
SUBCOOLER
VALVE
ISOLATION
VALVE
ECONOMIZER
COMPRESSOR
SOLID STATE
STARTER
ECONOMIZER
OIL PUMP
HOUSING
OIL PUMP
PANEL
SECTION 1 - YKEP CHILLER OVERVIEW
FORM 160.77-O2
ISSUE DATE: 11/15/2011
JOHNSON CONTROLS
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SECTION 1 - YKEP CHILLER OVERVIEW
Economizer Compressor Stop criteria:
Primary Compressor Calculated Flow ≤ the prescribed
Start criteria line minus 2000 CFM
3. When the primary compressor capacity reaches
full capacity dened by either 100% input cur-
rent FLA or fully open PRV and full speed (VSD
starter types), the economizer compressor switch-
es to Boost operating mode. In this mode, the
economizer compressor capacity is controlled
to maintain leaving chilled liquid temperature
at setpoint and the primary compressor is given
a leaving chilled liquid temperature target 1 de-
gree F below the chiller setpoint to keep it fully
loaded. The economizer compressor is then con-
trolled to maintain the chiller programmed leav-
ing chilled liquid temperature setpoint using its
PRV’s. As additional capacity is required, the
economizer compressor draws the economizer
pressure lower, increasing the refrigeration effect
PRIMARY COMPRESSOR
CONDENSER
ECONOMIZER COMPRESSOR
ECONOMIZER
EVAPORATOR
CHILLED
LIQUID
(OPTIONAL)
HOT GAS
BYPASS VALVE
ECONOMIZER
LEVEL VALVE
ECONOMIZER
LEVEL
SUBCOOLER
LEVEL
COOLING
LIQUID
PRV
VGD
VGD
CHECK
VALVE
PRV
SUBCOOLER
LEVEL VALVE
FIGURE 2 - YKEP CHILLER SYSTEM DIAGRAM
LD16021
FORM 160.77-O2
ISSUE DATE: 11/15/2011
SECTION 1 - YKEP CHILLER OVERVIEW
JOHNSON CONTROLS
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1
of the mass owing through the primary and in-
creasing chiller capacity. Upon unloading, when
the economizer compressor PRV closed switch is
activated, signifying the economizer compressor
is completely unloaded, or the economizer satu-
ration temperature is 0.5 Degrees F above what
the target saturation temperature would be for
economizing mode, the economizer compressor
switches back to economizing operation. Then
the primary compressor control returns to fol-
lowing the chiller programmed leaving chilled
liquid temperature and the economizer compres-
sor is following its target economizer pressure as
described in (2) above.
A timing diagram of the compressors’ start sequence
and shutdown is shown in Figure 3 on Page 9.
FIGURE 3 - YKEP CHILLER OPERATION SEQUENCE TIMING DIAGRAM
LD16023
0 10 13 45 50 110
(0.17) (0.22) (0.75) (0.83) (1.83)
VANES
CLOSED
MAN. OIL
PUMP
DISABLED
AUTO ZEROING DIFFERENTIAL
OIL PRESSURE TRANSDUCERS
** VANES CLOSING - TIME
DEPENDENT ON INITIAL
VANE POSITION
OIL PRESSURE CHECK
OIL PUMP ON
"SYSTEM
COASTDOWN"
"SYSTEM
SHUTDOWN"
TIME IN SECONDS (MINUTES)
DISPLAY
MESSAGE
"SYSTEM RUN"
"SYSTEM PRELUBE"
** "VANES CLOSING
BEFORE
SHUTDOWN"
ENERGIZE (OPEN)
LIQUID GEAR COOLING
SOLENOID (PRIMARY COMPRESSOR)
RESTART AFTER
ANTI-RECYCLE
(FOR EM STARTERS, 30 MIN)
(FOR VSD STARTERS, 5 STARTS THEN 10 MIN)
240 SEC
(4 MIN)
K7
Q3
150 SEC
(2.5 MIN)
FLOW
SWITCH
BYPASS
START STOP
FORM 160.77-O2
ISSUE DATE: 11/15/2011
JOHNSON CONTROLS
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SECTION 1 - YKEP CHILLER OVERVIEW
YKEP OIL MANAGEMENT
Figure 4 on Page 11 shows the layout of the chiller
oil management system. Each compressor has a dedi-
cated oil pump in a common oil sump with the other
pump. Oil for each is passed through its individual
oil cooler and filter set to the compressor bearings.
Each compressor has supervisory pressure monitoring
against the sump pressure to ensure sufficient supply to
its bearings. Refrigerant liquid flow to each oil cooler
is regulated with a thermostatic expansion valve sens-
ing oil temperature at the outlet of the cooler to 110° F.
Oil drains from the rotor support of each compressor
back to the sump. Oil to each compressor fills a drain-
down reservoir in the housing to provide coastdown oil
in the event of a power loss while running.
Oil temperature is maintained to a target 50° F above
condenser saturation temperature when the chiller is
not running. Electric oil heaters are operated by the
control system to accomplish this. At no time will the
control allow the oil heaters to continue to operate with
oil temperature above 160°F.
Oil return from the refrigerant system is accomplished
with a single eductor block. The block has three pas-
sages with eductor nozzles, all driven by condenser gas
from a common manifold within the block.
The venturi stream of each of the nozzles draws fluid
from:
• the evaporator
• the primary compressor PRV cavity in two adja-
cent locations
• the economizer compressor PRV cavity.
The outlet of the eductor sections goes to a common
plenum in the block and vented to the oil sump. The oil
sump is vented to the suction of the Primary compres-
sor behind the pre-rotation vanes.
The primary compressor is also supplied with liquid
refrigerant gear cooling that is initiated with a solenoid
valve that opens for compressor run.
FORM 160.77-O2
ISSUE DATE: 11/15/2011
SECTION 1 - YKEP CHILLER OVERVIEW
JOHNSON CONTROLS
11
1
FIGURE 4 - YKEP CHILLER OIL MANAGEMENT SYSTEM
LD16022
FORM 160.77-O2
ISSUE DATE: 11/15/2011
JOHNSON CONTROLS
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SECTION 1 - YKEP CHILLER OVERVIEW
CAPACITY CONTROL OPERATION
Chiller Applications
Much of the function of the YKEP Control System is
dedicated to chiller capacity control. Sensors register
system conditions that are used to infer the total cool-
ing load and make necessary adjustments to the system
components. A complete list of sensors is shown in
Table 1 on Page 18.
There are two primary mechanisms by which cooling
capacity is controlled: pre-rotation vanes, and the hot
gas bypass valve. The primary directive of the Control
System is first to maintain safe operating conditions,
then to keep the system online, and finally to efficient-
ly maintain setpoints.
The interaction of capacity control subsystems is com-
plex, and can be better understood by referring to the Ca-
pacity Control Model shown in Figure 5 on Page 13.
The Capacity Control philosophy of the York YKEP
chiller control system allows efficient, fully automated
control, without need for operator intervention. The
YKEP control system is designed for industrial process
applications. This control system also monitors and
displays all safety aspects of the chiller and provides
alarms and a shutdown if safety limits are exceeded. If
operator intervention is required, manual controls are
provided on the Electronic Operator interface, for all
electric actuators.
The Capacity Controls algorithm automatically seeks
out the most efficient operation of the YKEP chiller. The
pre-rotation vanes are automated to obey the tempera-
ture controller to maintain process water production. In
cases of low load, the pre-rotation vanes automatically
throttle and are limited to a minimum anti-surge posi-
tion, which is calculated from a head curve. To provide
light duty operation, the hot gas recycle valve is seam-
lessly throttled open according to temperature demands.
This keeps the centrifugal compressor out of surge and
maintains process water production.
In cases of high load, which exceeds the motor current
usage, the capacity controls algorithm automatically
unloads the system to maintain a restriction on power
consumption. In the same way, conditions of high dis-
charge pressure or low suction pressure override the
production of process water in the interests of keeping
the chiller system online.
In cases of light load and low head, the economizer
compressor is dropped offline and the unit will be run
with the primary compressor like a single-stage YK
chiller.
In cases of high load, the economizer compressor is
brought back online to perform the additional gas com-
pression. The unit runs in compound mode with the
flash economizer in the cycle.
Start Up
When the chiller is started from shutdown, until the
Leaving Chilled Liquid Temperature comes within 2
degrees F of the Leaving Chilled Liquid Temperature
Setpoint the Hot Gas Bypass valve is driven closed at
a programmed ramp rate. When the Hot Gas Bypass
valve reaches full closed, the Primary compressor pre-
rotation vanes are driven open at a programmed ramp
rate. These program points are set on the Primary Ca-
pacity Tuning screen. When either; 1) the pre-rotation
vanes reach full open or 2) the LCHLT comes within 2
degrees F of setpoint, the ramp control stops and con-
trol of the Hot Gas valve and pre-rotation vanes switch-
es to the capacity control PID and anti-surge controls.
High current, low evaporator pressure or high condens-
er pressure overrides are always applicable when their
thresholds are exceeded.
Role of Hot Gas Bypass
The natural solution on a centrifugal chiller applica-
tion is that when the surge line is approached with a
decrease in load, the mass flow cannot be decreased
without aerodynamic instability; therefore the hot gas
bypass is used to supplement mass flow. This supple-
mental mass flow creates a source of inefficiency in
the refrigeration cycle and allows the chiller to run at
lower evaporator loads than it could without hot gas.
Major Capacity Control Devices
1. Compressor Pre-rotation Vanes
The compressor pre-rotation vanes (PRV's) are
internal guide vanes in the suction flow path to
the impeller wheel. The PRV's are used to throttle
the refrigerant flow through the system as a means
of controlling capacity in response to the leaving
chilled water temperature. If the leaving chilled
water temperature falls below the setpoint, the
PRV's are partially closed until the net cooling is
reduced and the leaving chilled water returns to
setpoint.
In the event of high motor power, the capacity
control signal is over-ridden and the compressor
PRV's are closed to keep the motor power down.
FORM 160.77-O2
ISSUE DATE: 11/15/2011
SECTION 1 - YKEP CHILLER OVERVIEW
JOHNSON CONTROLS
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1
On start-up, the PRV's are closed to reduce the
starting load torque of the compressor.
The compressor pre-rotation vanes are closed on shut-
down to reduce backflow of high-pressure gas from
the condenser, which might otherwise cause the com-
pressor to spin backwards at a high rate of speed.
A shaded pole motor operates the mechanical
pre-rotation vane linkage, at the compressor. The
shaded pole motor is operated by a contact closure
to either open or close the vanes. A pre-rotation
vane position potentiometer senses the position of
the vanes and reports it to the controller as a per-
centage open value.
2. Hot Gas Bypass Valve
The hot gas bypass valve is used primarily at low
loads to maintain a minimum suction gas flow re-
quired by the compressor for stability. When the
compressor has reduced capacity to its minimum
flow (via pre-rotation vane throttling), further ca-
pacity reductions are accomplished by opening
the hot gas bypass valve. This maintains the flow
to the compressor by bypassing the discharge gas
back to the compressor suction.
However, the hot gas flow replaces the useful
evaporation in the cooler since the compressor
flow is at minimum. Thus, the net chilling capac-
ity is reduced (albeit not efficiently).
The minimum suction flow or minimum com-
pressor PRV position will vary. As the differential
“head” pressure is lowered (due to colder con-
denser water) the compressor is capable of stable
operation at lower loads. The programming in the
chiller panel thus uses the differential “HEAD”
pressure to establish when the hot gas may be
needed.
• On a water chilling application, this valve
goes open on shutdown.
FIGURE 5 - CAPACITY CONTROL MODEL
CHILLED WATER
TEMPERATURE
CONTROLLER
>
GREATER
THAN
SELECTOR
RATIO CONTROLLER
= 100-(100*LESS THAN
SELECTOR)/ANTISURGE)
HOT GAS
RECYCLE
VALVE
COMPRESSOR
PRE-ROTATION
VANES
ANTISURGE VANE
POSITION FOR A
GIVEN LIFT
CONDTION
<
LESS THAN
SELECTOR
MOTOR CURRENT LIMIT
CONTROLLER
(DOES NOT UNLOAD
LESS THAN ANTI-SURGE)
EVAPORATOR
PRESSURE
OVERRIDE
CONTROLLER
CONDENSER
PRESSURE
OVERRIDE
CONTROLLER
FORM 160.77-O2
ISSUE DATE: 11/15/2011
JOHNSON CONTROLS
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SECTION 1 - YKEP CHILLER OVERVIEW
The hot gas valve is a disc type control valve with
an electric actuator. The control signal is a modu-
lating direct current signal, which is converted to a
position by an electric actuator. The valve will be
fully closed at low signal and open at high signal.
Refer to YKEP Wiring Diagram - Unit Wiring and
Field Control Modification (Form 160.77-PW2)
to see the 0-10 VDC Control Signal wiring. The
Output Scaling screen allows factory selection of
the proper output signal.
3. Subcooler Liquid Level Valve LCV-114
The subcooler liquid level valve controls the re-
frigerant liquid level in the subcooler located in
the bottom of the condenser to maintain the prop-
er amount of subcooling and provide the most ef-
ficient operation at all loads.
This valve is opened after shutdown to allow a
slow change in pressure between evaporator and
condenser. The pressure in the condenser forces
the liquid out of the condenser into the economiz-
er and the evaporator. It opens at start-up and then
slowly closes until it reaches the position dictated
by the liquid level control PID instruction in the
chiller controller.
The liquid level valve is a disc type control valve
with an electric actuator. The control signal is
modulated direct current, which is converted to a
position by an electric actuator. The valve will be
fully closed at low signal and open at high signal.
4. Economizer Liquid Level Valve LCV-116
The Economizer liquid level valve controls the
refrigerant liquid level in the economizer to main-
tain a good liquid seal between the flash gas in the
top of the economizer and the liquid to the evapo-
rator, this provides the most efficient operation at
all loads.
The liquid level valve is a disc type control valve
with an electric actuator. The control signal is
modulating direct current, which is converted to a
position by an electric actuator. The valve will be
fully closed at low signal and open at high signal.
Programmed Capacity Control Functions
Chilled Temperature Control
Using the input signal from a temperature sensor in the
leaving chilled water line, this control provides an out-
put signal, which decreases as water temperature drops
below set point to reduce the capacity of the chiller.
When override and anti-surge conditions are satis-
fied, the temperature control subsystem may dominate.
Since temperature control is the highest function as-
sociated with capacity control, its task must be con-
current and compliant with all other subsystems and
subsystem directives. It controls the hot gas valve, and
pre-rotation vanes in its attempt to maintain the chilled
water temperature setpoint while keeping the compres-
sor out of surge.
Dynamic Override Controls
Three operating parameters are primarily concerned
with the safe operation of the system: evaporator pres-
sure, condenser pressure, and motor load. If any of
these parameters were to exceed the limits defined by
the setpoints, it could lead to a shutdown of the chiller
by the safety setpoints. Maintaining chiller operation is
the function of the Dynamic Override subsystem.
The power override control function uses the motor
power input signals to limit capacity. When one of the
motor powers exceeds the setpoint, the control puts out
a decreasing signal. The Less Than Selector will then
pass this lower signal on to close the compressor pre-
rotation vanes, thus reducing the demand on the mo-
tor and returning the motor demand limit to below the
maximum threshold.
The pressure override systems prevent a system opera-
tion condition from shutting down a chiller premature-
ly. The pressure override loop controllers maintain the
chiller operation just within the safe operational limits
of the vessels, until system conditions return to design.
The condenser pressure override produces an unloading
effect on the chiller if the cooling water to the chiller
goes above design. If the chiller were not unloaded in
this condition, the discharge high-pressure cutout would
shut the chiller down, and no cooling would be done.
The low evaporator pressure override is a key override in
preventing the unit from either freezing or going down
on low evaporator conditions. A system overshoot, or a
low temperature transition in process water can result
in a low suction pressure condition. During startup, the
condensing pressure may initially be low. This can cause
low level in the evaporator, thereby reducing the heat ex-
changer performance, and lowering the evaporator pres-
sure. The low evaporator pressure override unloads the
chiller rapidly, and often opens the hot gas valve to try
to maintain a suction pressure in the chiller. As the fault
condition subsides, the override backs off and returns
the chiller to normal temperature controlled operation.
FORM 160.77-O2
ISSUE DATE: 11/15/2011
SECTION 1 - YKEP CHILLER OVERVIEW
JOHNSON CONTROLS
15
1
ANTI-SURGE, PRV
Keeping the compressor out of surge is the function
of the anti-surge subsystem. The anti-surge system is
based on a straight-line approximation of the compres-
sor surge curve (Figure 6 on Page 15).
The anti-surge line is biased to the right of the actual
surge line. When the compressor needs to move left on
the map, and move less mass flow, the vanes can only
be reduced so far, before a lack of mass flow causes
a surge condition. The anti-surge system supplements
mass flow to the compressor by using the Hot Gas By-
pass valve. This allows the chiller to be unloaded with-
out surge.
Once the anti-surge system has been set for the maxi-
mum head condition, and the minimum head condi-
tion, the compressor is restricted from surge. The point
represented by the intersection of VPD1 and MVP1 is
the worst case operating condition of the compressor,
with high head and low load. The other condition that
defines the anti-surge line is at low head and low load,
represented by the intersection of VPD2 and MVP2.
The shaded area of the left side of the map is the surge
area.
The vanes cannot close more than a given percentage
for a given head condition, defined by this line. As the
capacity control system unloads the chiller, the Hot
Gas Bypass valve is opened proportionally to maintain
stable operation and control the process.
SYSTEM ANTI-SURGE MAP
H
E
A
D
200
150
100
50
0
0 25 50 75 100
MVP2 MVP1
% VANES
VPD1
x
VPD2
FIGURE 6 - SYSTEM ANTI-SURGE MAP
LD15231
Anti-Surge (PRV) Calculation
The anti-surge tuning values are based on estimated
part load conditions and minimum vane signals re-
quired at these conditions to prevent unstable opera-
tion (surging):
Compressor
Differential
(Head) Pressure
Minimum PRV Signal
Setpoint for
Stable Operation
High Head
(PD1)
70 psid MVP1 = 8% Open
Low Head
(PD2)
30 psid MVP2 = 2% Open
It is very important that this control be
adjusted to suit chiller operating condi-
tions to achieve maximum efciency of
operation.
Anti-Surge (PRV) Tuning
• With the chiller running in automatic, take the
condensing conditions to the highest inlet tem-
perature attainable in the system (without tripping
on high discharge pressure). Increase tower inlet
temperature or reduce tower ow.
• At the highest condensing temperature, start re-
ducing the load on the chiller, by reducing the
ow, or decreasing the inlet temperature. This
will cause the capacity control system to back the
vanes in an unload sequence.
• If the chiller surges before the Hot Gas valve be-
gins to open, then the anti-surge line must move
right on the map.
• If the chiller never surges down to minimum load,
then the anti-surge parameters are adequate for
protection, but may not be most efcient.
• During the unload sequence, record the operating
head as VPD1.
• Increasing and decreasing the parameter MVP1
will move the anti-surge line right and left on the
map. Listen for a surge, and move the anti-surge
line right several percent, to increase refrigerant
ow, by supplementing hot gas.
• Repeat the procedure for low head operation.
• At the lowest condensing temperature, start reduc-
FORM 160.77-O2
ISSUE DATE: 11/15/2011
JOHNSON CONTROLS
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SECTION 1 - YKEP CHILLER OVERVIEW
ing the load on the chiller, by reducing the ow, or
decreasing the inlet temperature. This will cause
the capacity control system to back the vanes in
an unload sequence.
• If the chiller surges before the Hot Gas valve be-
gins to open, then the anti-surge line must move
right on the map.
• If the chiller never surges down to minimum load,
then the anti-surge parameters are adequate for
protection, but may not be most efcient.
• During the unload sequence, record the operating
head as VPD2
• Increasing and decreasing the parameter MVP2
will move the anti-surge line right and left on the
map. Listen for a surge, and move the anti-surge
line right several percent, to increase refrigerant
ow, by supplementing hot gas.
The plant condenser water control system will deter-
mine the actual high and low head conditions depending
on the range of condenser water temperature allowed.
If actual operating conditions are different than those
shown above, you must enter the new values for the an-
ti-surge parameter calculation to produce the required
output signals.
The “ANTI-SURGE MIN PRV POS” output (Y%) is
calculated based on the actual calculated differential
pressure (head) as follows:
PD (Head) = (Compressor Discharge Pressure) – (Evaporator Pressure)
Y% = (PD-PD2) x (MVP1-MVP2) / (PD1-PD2) + MVP2
Hot Gas Control Tuning
The “HOT GAS CONTROL” operates to open the
valve as a decreasing load causes the “CHILLED WA-
TER TEMP. CONTROL” output to drop below the
“ANTI-SURGE MIN. PRV POSITION”.
ANTI-SURGE, SPEED
Chillers which employ a variable speed drive for the
primary compressor motor also use a speed anti-surge
subsystem. This system is based on a 4-segment line
approximation of the compressor full-open PRV surge
curve. The specifics can be visualized on the Primary
Anti-Surge Screen. Any required adjustments to the
speed anti-surge tuning should be performed before
adjusting the PRV anti-surge line.
Anti-Surge (Speed) Tuning
• With the chiller running in automatic, take the
condensing conditions to the highest inlet tem-
perature attainable in the system (without tripping
on high discharge pressure). Increase tower inlet
temperature or reduce tower ow.
• At the highest condensing temperature, start re-
ducing the load on the chiller, by reducing the
ow, or decreasing the inlet temperature. This
will cause the capacity control system to back the
primary compressor speed in an unload sequence.
• If the chiller surges before the PRV’s throttle
closed, then the anti-surge line must move right
on the map.
• If the chiller never surges down to minimum load,
then the anti-surge parameters are adequate for
protection, but may not be most efcient.
• During the unload sequence, record the operating
head as SPD1
• Increasing and decreasing the parameter MSP1
will move the anti-surge line right and left on the
map. Listen for a surge, and move the anti-surge
line right several percent, to increase speed.
• Repeat the procedure for low head operation.
• At the lowest condensing temperature, start reduc-
ing the load on the chiller, by reducing the ow, or
decreasing the inlet temperature. This will cause
the capacity control system to back the primary
compressor speed in an unload sequence.
• If the chiller surges before the PRV’s throttle
closed, then the anti-surge line must move right
on the map.
• If the chiller never surges down to minimum load,
then the anti-surge parameters are adequate for
protection, but may not be most efcient.
• During the unload sequence, record the operating
head as SPD5.
• Increasing and decreasing the parameter MSP5
will move the anti-surge line right and left on the
map. Listen for a surge, and move the anti-surge
line right several percent, to increase speed.
• Repeat the process as needed for head and mini-
mum speed points SPD2, SPD3, SPD4 and MSP2,
MSP3, MSP4 between the endpoints to further
dene the surge line.
FORM 160.77-O2
ISSUE DATE: 11/15/2011
JOHNSON CONTROLS
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22
SECTION 2 - YKEP CONTROL CENTER INTRODUCTION
YKEP CONTROL CENTER
The YKEP Control Center is a fully integrated system
that monitors and controls all aspects of the chiller’s
components (see Figure 1 on Page 7) and opera-
tion. It provides all the necessary controls and control
logic to facilitate automatic start-up, automatic opera-
tion, capacity control, and safety protection. The Con-
trol Center has two components - the Logic Controller
and the Human-Machine Interface (HMI):
Logic Controller
The logic controller is a stand-alone Allen-Bradley
1769-L35E Compact Logix Programmable Automa-
tion Controller (PAC) (see Figure 7 on Page 17).
• The PAC controls all aspects of machine operation
by monitoring vital parameters and making real-
time adjustments as necessary to ensure safe and
efcient operation of system components.
LD15302
FIGURE 7 - LOGIC CONTROLLER
Control Panel
The control panel is a RedLion Controls Model
G310C230 10.4” color active matrix touchscreen dis-
play with seven front-panel push-buttons and three
front-panel LEDs (see Figure 8 on Page 17). The
control panel is a factory wired, unit mounted, NEMA
12, gasketed enclosure.
• The panel displays real-time chiller sensor data
via the PAC and allows for manual adjustments to
operational parameters.
FIGURE 8 - CONTROL PANEL
LD15303
OPERATOR INTERFACE
Operators access the chiller control system through
full-color screens that display real-time data from all
control system sensor points (see Figure 9 on Page
19) and are equipped with both sensor history log-
ging and complete alarm/system trip history features.
YKEP CONTROL CENTER FEATURES
The Control Center for YKEP is a Programmable Au-
tomation Controller (PAC) based control system for
YORK R134a centrifugal chillers. It controls the leav-
ing chilled liquid temperature and maintains required
pressure to avoid surge via pre-rotation vane controls,
motor drive speed and optional hot gas bypass. It has
the ability to limit motor current and shell pressures.
The Control Center comes configured with a full 10.4”
screen LCD touchscreen Graphic Display. The graphic
display allows the presentation of several operating pa-
rameters at once. In addition, the operator may view a
graphical representation of the historical operation of
the chiller as well as the present operation. For the nov-
ice user, the locations of various chiller parameters are
clearly and intuitively marked. Instructions for specific
operations are provided on many of the screens.
The graphic display also allows information to be rep-
resented in both English (temperatures in °F and pres-
sures in PSIG) and Metric (temperatures in °C and
pressures in BAR) mode. The advantages are most
FORM 160.77-O2
ISSUE DATE: 11/15/2011
JOHNSON CONTROLS
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SECTION 2 - YKEP CONTROL CENTER INTRODUCTION
apparent, however, in the ability to display many lan-
guages.
The Control Center continually monitors the system op-
eration 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 may recall it for viewing at any time.
During operation, the user is continually advised of the
operating conditions by various status and warning mes-
sages. In addition, it may be configured to notify the
user of certain conditions via alarms. A complete listing
of shutdown, status, and warning messages is attached
in the Display Messages section of this book.
There are certain screens, displayed values, program-
mable Setpoints and manual controls shown in this book
that are 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 YKEP Unit Service
(Form 160.77-M1). These parameters affect chiller op-
eration and should never be modified by anyone other
than a qualified Service Technician. They are shown in
this book for reference only.
Advanced Diagnostics and troubleshooting information
for Service Technicians are included in YKEP Control-
Center Service (Form 160.77-M2). Also included in the
Service manual are detailed descriptions of chiller fea-
tures, such as the Refrigerant Level Control, Hot Gas
Bypass, Remote Setpoints, and Variable Geometry Dif-
fuser.
The control center expands the capabilities of remote
control and communications. By providing a common
networking protocol through the Modbus RTU, YORK
Chillers not only work well individually, but also as a
team. This network protocol allows increased remote
control of the chiller, as well as 24-hour performance
monitoring via a remote site. In addition, compatibility
is maintained with the present network of BAS commu-
nications. The chiller also maintains the standard digital
remote capabilities as well. Both of these remote control
capabilities allow for the standard Energy Management
System (EMS) interface:
1. Remote Start
2. Remote Stop
3. Remote Leaving Chilled Liquid Temperature
Setpoint adjustment (4-20mA)
4. Remote Current Limit Setpoint adjustment
(4-20mA)
5. Remote “Ready to Start” Contacts
6. Safety Shutdown Contacts
7. Cycling Shutdown Contacts
TABLE 1 - YKEP CONTROL SYSTEM SENSORS
SENSOR DESCRIPTION
FSLL-100 Evaporator Chilled Liquid Flow Switch
FSLL-103 Condenser Water Flow Switch
LCV-114 Subcooler Level Valve Actuator
LCV-116 Economizer Level Valve Actuator
LE-114 Subcooler Refrigerant Level Sensor
LE-116 Economizer Level Sensor
PCV-112A Open/Close Primary Compressor VGD
PCV-112B Open/Close Primary Compressor VGD
PE-111 Evaporator Refrigerant Pressure
PE-113 Condneser Refrigerant Pressure
PE-116 Economizer Refrigerant Pressure
PE-140 Oil Sump Pressure
SENSOR DESCRIPTION
PE-141A Primary Compressor Oil Pump Pressure
PE-141B Economizer Compressor Oil Pump Pressure
PE-149A Primary Compressor Discharge Pressure
PE-149B Economizer Compressor Discharge Pressure
PSHH-113A
* Primary Compressor High Discharge
Pressure Cutout
PSHH-113B
* Economizer Compressor High Discharge
Pressure Cutout
PWM1 Primary Compressor Oil Pump Speed
PWM2 Economizer Compressor Oil Pump Speed
RST-100 Leaving Chilled Liquid Remote Setpoint
RST-160 Remote Demand Limit
FORM 160.77-O2
ISSUE DATE: 11/15/2011
SECTION 2 - YKEP CONTROL CENTER INTRODUCTION
JOHNSON CONTROLS
19
2
FIGURE 9 - YKEP CONTROL SYSTEM SENSORS
LD15304
CONDENSER
ECONOMIZER
EVAPORATOR
MOTOR
JUNCTION
BOX
PE-141A
TE-100
TE-101
PE-141B
ZS-142B
ZS-100B
TCV-100B
VSDA
VSDB
PWM1
PWM2
ZS-100A
TCV-100A
PE-111
PE-113
TE-111
ZE-100A
PE-149B
PE-149A
TE-113
TE-112
FSLL-100
ZE-100B
PCV-112B
ZE-149B
PCV-112A
ZE-149A
PE-116
LE-116
LCV-116
LCV-114
TE-114
LE-114
TE-102
PE-140
TE-140
TE-103
FSLL-103
* Not Shown
SENSOR DESCRIPTION
TCV-100A Open/Close Primary Compressor PRV
TCV-100B Open/Close Economizer Compressor PRV
TCV-100C * Hot Gas Valve Actuator (Optional)
TE-100 Leaving Chilled Liquid Temperature
TE-101 Entering Chilled Liquid Temperature
TE-102 Entering Condenser Water Temperature
TE-103 Leaving Condenser Water Temperature
TE-111 Evaporator Refrigerant Liquid Temperature
TE-112 Primary Compressor Discharge Temperature
TE-113
Economizer Compressor Discharge
Temperature
TE-114 Subcooled Refrigerant Liquid Temperature
TE-140 Oil Sump Temperature
VSDA
Primary Compressor Main Oil Pump Drive
Faulted
SENSOR DESCRIPTION
VSDB
Economizer Compressor Main Oil Pump
Drive Faulted
XE-149A
* Primary Compressor VGD Stall Board
Signal
XE-149B
* Economizer Compressor VGD Stall
Board Signal
ZE-100A Primary Compressor PRV POT
ZE-100B Economizer Compressor PRV POT
ZE-142A Primary Compressor Axial Thrust Position
ZE-149A Primary Compressor VGD Position Pot
ZE-149B Economizer Compressor VGD Position Pot
ZS-100A Primary Compressor PRV Closed Limit Switch
ZS-100B
Economizer Compressor PRV Closed Limit
Switch
ZS-142B Economizer Compressor Thrust Switch
FORM 160.77-O2
ISSUE DATE: 11/15/2011
JOHNSON CONTROLS
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