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Compressor Motor Winding Thermostats (Standard)
A thermostat is embedded in the motor windings of each
Scroll compressor. Each thermostat is designed to open if
the motor windings exceeds approximately 221
mostat will reset automatically when the winding tempera-
ture decreases to approximately 181
of charge, abnormally high suction temperatures, or the
compressor running backwards could cause the thermostat
to open. During a request for compressor operation, if the
Compressor Module detects a problem outside of it's nor-
mal parameters, it turns any operating compressor(s) on
that circuit "Off", locks out all compressor operation for that
circuit, and initiates a manual reset diagnostic.
Low Ambient Compressor Lockout (Standard)
When low ambient compressor lockout is enabled, the com-
pressors are not allowed to operate if the temperature of
the outside air falls below the lockout setpoint. Compressor
operation is enabled when the temperature rises 5
the lockout setpoint. The setpoints and enable/disable op-
tion is programmable at the Human Interface inside the unit
control panel. The default setting is 30
Short Cycle Protection (Standard)
If compressor operation is interrupted by a loss of power or
by a manual reset diagnostic, a minimum of one minute
must elapse before the affected compressor(s) will be al-
lowed to restart for "Process" applications. A minimum of
three minutes must elapse before the affected
compressor(s) will be allowed to restart for "Comfort Cool-
ing" applications.
Hot Start (Load Limit) Control (Standard)
Each time the system is started and the control of the CGM
transitions from "Loop Stabilization" to either "Process" or
"Comfort Cooling", if the Leaving Solution Temperature
(LST) is higher than the programmable Hot Start Load Limit
Setpoint (HSLLS), the lag compressor on each circuit will
be prevented from operating until the leaving solution tem-
perature is lowered by 5
o
F below the HSLLS.
If the Hot Start Limit time interval elapses before the LST is
o
5
F below the HSLLS, the control will transition immediately
into the Hot Operation mode.
Hot Operation mode is programmable to:
1. Do not limit capacity, initiate an informational diagnostic
o
until the LST falls 5
F below the HSLLS.
2. Limit the capacity to 50 percent (one compressor per cir-
cuit), initiate an auto reset diagnostic until the LST falls
5
o
F below the HSLLS.
3. Turn "Off" and lockout all of the compressors and initiate
a manual reset diagnostic.
Loss-of-Flow (Solution) Protection (Standard)
All units:
Compressors are allowed to operate once the pump is run-
ning and the flow switch input is closed. If the flow switch
input opens during normal operation for longer than 6 sec-
onds, the compressors and fans will stop. If the switch input
is still open after 5 minutes, a auto-reset diagnostic (Evap
Solution Flow Proving Switch) will be generated. Once this
input is closed, the diagnostic will clear and the compres-
sors will be allowed to resume operation. If the flow switch
fails open or is not connected when the chiller starts up,
General Information
o
F. The ther-
o
F. Rapid cycling, loss
o
F above
o
F.
8
only the solution pump output will be energized. 5 minutes
later, an auto-reset diagnostic (Evap Solution Flow Proving
Switch) will be generated. Once the flow switch input
closes, the chiller will operate normally.
If the chiller controls the pump (Chiller solution pump
mode = AUTO):
If the pump is cycled off by the CGM or a power failure oc-
curs, and the unit is re-started, the flow switch input must
open and then close for proper operation. If the switch is
stuck closed or shorted, the pump will start but compres-
sors will not operate. Also, a manual resettable diagnostic
(Evaporator Solution Flow Loss) will be generated. To reset
the diagnostic, stop the pump and allow the flow switch to
open, then reset at the Human Interface (see Programming
Guide).
Note: There is a minimum "off" time of 60 seconds for the
pump output. This "off" time is overridden if the flow switch
opens.
If the chiller does not control the pump (Chiller solution
pump mode = ON):
Do not bypass the flow switch input! If the flow switch input
is bypassed, the unit will not have flow loss protection and
equipment damage may result.
WARNING
Equipment Damage!
Do not bypass the flow switch input! If the flow switch
input is bypassed, the unit will not have flow loss pro-
tection and equipment damage may result.
The flow switch input must be closed for compressor opera-
tion. If the flow switch input is open and a request for cool-
ing is given, compressors will not start and a auto-reset di-
agnostic (Evap Solution Flow Proving Switch) will be gener-
ated after 5 minutes. Once this input is closed, the diag-
nostic will clear and the compressors will be allowed to op-
erate.
Low Ambient Start (Standard)
Before first start of a compressor on a refrigerant circuit, the
CGM Low Ambient LPC Bypass output is closed which by-
passes the Freeze Protection Cutout (FPC) switch in the
MCM Low Pressure Cutout (LPC) input circuit for a period
of time that varies based on the prevailing ambient tem-
perature. The relationship between this variable time period
and the ambient temperature is linear from a maximum of 5
minutes at 0°F to a minimum of two minutes at 65°F. A fixed
three minute bypass time is initiated each time a subse-
quent compressor is started on a refrigerant circuit. No ad-
ditional compressors will be allowed to start within that cir-
cuit until the bypass time has expired.
Chiller Solution Pump Output Relay (Standard)
A Solution Pump binary output (Form C) relay is located on
the CGM which may be used to control the chiller solution
pump.
If the Chiller Solution Pump Mode, at the Human Interface
Module, is set to "On", the Solution Pump will run continu-
ously.
If the Chiller Solution Pump Mode, at the Human Interface
Module, is set to Auto, the Solution Pump will be turned
"Off":
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