Specifications
Table Of Contents
- Form 150.72-NM1 (908)
- GENERAL SAFETY GUIDELINES
- CHANGEABILITY OF THIS DOCUMENT
- TABLE OF CONTENTS
- LIST OF FIGURES
- LIST OF TABLES
- SECTION 1 – GENERAL CHILLER INFORMATION & SAFETY
- SECTION 2 – PRODUCT DESCRIPTION
- INTRODUCTION
- GENERAL SYSTEM DESCRIPTION
- HIGH AMBIENT KIT
- BUILDING AUTOMATION SYSTEM INTERFACE
- MILLENIUM CONTROL CENTER
- POWER PANEL
- ACCESSORIES AND OPTIONS
- UNIT COMPONENTS
- CONTROL / POWER PANEL COMPONENTS
- PRODUCT IDENTIFICATION NUMBER (PIN)
- BASIC UNIT NOMENCLATURE
- REFRIGERANT FLOW DIAGRAM
- PROCESS AND INSTRUMENTATION DIAGRAM
- SECTION 3 – HANDLING AND STORAGE
- SECTION 4 – INSTALLATION
- INSTALLATION CHECKLIST
- HANDLING
- INSPECTION
- LOCATION AND CLEARANCES
- SPRING ISOLATORS (OPTIONAL)
- COMPRESSOR MOUNTING
- REMOTE COOLER OPTION
- CHILLED LIQUID PIPING
- PIPEWORK ARRANGEMENT
- DUCT WORK CONNECTION
- WIRING
- COMPRESSOR HEATERS
- RELIEF VALVES
- HIGH PRESSURE CUTOUT
- SINGLE-POINT SUPPLY CONNECTION – TERMINAL BLOCK, NON-FUSED DISCONNECT SWITCH OR CIRCUIT BREAKER
- USER CONTROL WIRING INPUTS
- USER CONTROL WIRING OUTPUTS
- SECTION 5 – TECHNICAL DATA
- OPERATIONAL LIMITATIONS (ENGLISH)
- HEAT EXCHANGER FLOW, GPM
- PHYSICAL DATA (ENGLISH)
- ELECTRICAL DATA
- ELECTRICAL NOTES
- ELECTRICAL DATA W/O PUMPS
- ELECTRICAL DATA W/ PUMPS
- ELECTRICAL NOTES AND LEGEND
- WIRING DIAGRAMS
- DIMENSIONS (ENGLISH)
- TECHNICAL DATA – CLEARANCES
- WEIGHT DISTRIBUTION AND ISOLATOR MOUNTING POSITIONS
- ISOLATOR INFORMATION FOR UNITS SHIPPED ON OR AFTER JUNE 15, 2008
- ISOLATOR INFORMATION FOR UNITS SHIPPED BEFORE JUNE 15, 2008
- SLRS Seismic Isolator Specifications
- SLRS Seismic Isolator Installation and Adjustment
- One Inch Deflection Spring Isolator Cross-reference
- Installation of 1” Deflection Mounts
- Neoprene Isolator Cross-reference
- Two Inch Deflection, Seismic Spring IsolatorCross-reference - SLRS
- SLRS Seismic Isolator Installation and Adjustment
- SECTION 6 – COMMISSIONING
- SECTION 7 – UNIT CONTROLS
- SECTION 8 – UNIT OPERATION
- CAPACITY CONTROL
- SUCTION PRESSURE LIMIT CONTROLS
- DISCHARGE PRESSURE LIMIT CONTROLS
- LEAVING CHILLED LIQUID CONTROL
- LEAVING CHILLED LIQUID CONTROLOVERRIDE TO REDUCE CYCLING
- LEAVING CHILLED LIQUID SYSTEM LEAD/LAG AND COMPRESSOR SEQUENCING
- RETURN CHILLED LIQUID CONTROL
- RETURN CHILLLED LIQUID SYSTEM LEAD/LAG AND COMPRESSOR SEQUENCING
- ANTI-RECYCLE TIMER
- ANTI-COINCIDENCE TIMER
- EVAPORATOR PUMP CONTROL & YORK HYDRO KIT PUMP CONTROL
- EVAPORATOR HEATER CONTROL
- PUMPDOWN CONTROL
- STANDARD CONDENSER FAN CONTROL
- LOAD LIMITING
- COMPRESSOR RUN STATUS
- ALARM STATUS
- REMOTE BAS/EMS TEMPERATURE RESET USINGA VOLTAGE OR CURRENT SIGNAL
- SECTION 9 – SERVICE AND TROUBLESHOOTING
- SECTION 10 – MAINTENANCE
JOHNSON CONTROLS
144
FORM 150.72-NM1 (908)
Unit Operation
RETURN CHILLED LIQUID CONTROL
(Can be used on Dual System 4, 5 & 6 Comp
Units Only)
Return chilled liquid control is based on staging the
compressors to match the cooling load. The chiller will
be fully loaded when the return water temperature is
equal to the Cooling Setpoint plus the Range. The chiller
will be totally unloaded (all compressors off) when the
return water temperature is equal to the Cooling Setpoint
(See sample in Table 14). At return water temperatures
between the Cooling Setpoint and Cooling Setpoint
plus Range, compressor loading and unloading will be
determined by the formulas in Table 15.
RAnGe -
Normal loading will occur at intervals of 60 seconds
according to the temperatures determined by the formulas.
Unloading will occur at a rate of 30 seconds according
to the temperatures determined in the formulas used
to calculate the on and off points for each step of
capacity.
The return chilled liquid setpoint is programmable from
40 °F to 70 °F (4.4 °C to 21.1 °C) in water chilling mode
and from 10 °F to 70 °F (-12.2 °C to 21.1 °C) in glycol
chilling mode. In both modes, the cooling range can be
from 4 °F to 20 °F (2.2° to 11.1 °C).
As an example of compressor staging (refer to Table 14),
a chiller with six compressors using a Cooling Setpoint
programmed for 45 °F (7.20 °C) and a Range Setpoint
of 10 °F (5.56 °C). Using the formulas in Table 15, the
control range will be split up into six (seven including
hot gas) segments, with the Control Range determining
the separation between segments. Note also that the
Cooling Setpoint is the point at which all compressors
are off, and Cooling Setpoint plus Range is the point
all compressors are on. Specically, if the return water
temperature is 55 °F (12.8 °C), then all compressors
will be on, providing full capacity. At nominal gpm, this
would provide approximately 45 °F (7.2 °C) leaving
water temperature out of the evaporator.
If the return water temperature drops to 53.4 °F (11.9
°C), one compressor would cycle off leaving five
compressors running. The compressors would continue
to cycle off approximately every 1.7 °F (.94 °C), with
the exception of hot gas bypass. Notice that the hot
gas bypass would cycle on when the return water
temperature dropped to 46.25 °F (7.9 °C). At this point
one compressor would be running with hot gas.
Should the return water temperature rise from this
point to 46.7 °F (8.2 °C), the hot gas bypass would shut
off, still leaving one compressor running. As the load
increased, the compressors would stage on every 1.7
°F (.94 °C).
Also note that Table 15 not only provides the formulas
for the loading (ON POINT) and unloading (OFF
POINT) of the system, the “STEP” is also shown in the
tables. The “STEP” is the increment in the sequence
of the capacity control scheme that can be viewed
under the OPER DATA key. Refer to the section on the
DISPLAY/PRINT keys for specic information on the
OPER DATA key.
TABLE 14 – SAMPLE COMPRESSOR STAGING FOR RETURN WATER CONTROL
*Unloading only
Unit Operation
Compressor Staging for Return Water Control
4 Compressor
Cooling Setpoint = 45 °F (7.2 °C) Range = 10 °F(5.6 °C)
# of Comp
ON
0 * 1+HG 1 2 3 4
RWT
45 °F
(7.2 °C)
46.25 °F
(7.9 °C)
47.5 °F
(8.6 °C)
50.0 °F
(10.0 °C)
52.5 °F
(11.4 °C)
55.0 °F
(12.8 °C)