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System Testing & Troubleshooting
DIAGNOSTIC DISPLAYED REASON FOR DIAGNOSTIC UCM’S REACTION RESET REQUIRED
Cond Temp Sensor Failure - Circuit 2
(Circuit #2 40-60 Ton units only)
Problem: The Saturated Condenser
Temperature Input is out of range for
Circuit #2.
Check: Sensor resistance between
830 ohms (200 F) and 345.7Kohms
(-40 F). If so,
The unit is reading a signal that is out
of range for the circuit #2 Saturated
Condenser Temperature sensor.
(Temp < -40 F or Temp > 200 F).
A “Lockout Circuit #2” request is
issued to the Compressor Staging
Control function. The Compressor
Relays, LPC Bypass Relay, and
Liquid Line Solenoid Relay for
Circuit 2 are all de-energized.
(PAR) An automatic reset occurs after
the #2 Condenser Temp input returns
to its allowable range within 10
seconds.
Current Sensing Module Comm Fail
Problem: The CGM has lost
communications with the Current
Sensing Module (CSM)..
Check: Check field/unit wiring between
CGM and CSM.
The CGM has lost communications
with the CSM.
No Change in unit operation
occurs. The Current Sensing
Module is used for monitoring
purposes only, and does not affect
unit operation. This diagnostic is
for information only.
(PAR) An automatic reset occurs after
communication has been restored.
Emergency Stop
Problem: The Emergency Stop input
on the CGM is open.
An open circuit has occurred on the
Emergency Stop input caused either
by a High Duct Temp T-stat trip, or the
opening of field-provided contacts,
switch, etc...
“OFF or “Close” requests are
issued as appropriate to the
following functions;
a. Compressor Staging control. (All
Compressor Relays, Liquid Line
Solenoid Relays, LPC Bypass
Relay, and HGBP Relay are
deenergized).
b. Evaporator Solution Pump
Control. (S
(PMR) A manual reset is required after
the Emergency Stop input recloses.
The Diagnostic can be reset by the
Human Interface or Tracer or by
cycling power to the CGM.
EST/LST Low Temperature Indication
Problem: Either the entering solution
temperature or the leaving solution
temperature has fallen below the heat
tape temperature setpoint.
An abnormal temperature reading of
the chilled solution exists.
No change in the unit operation.
This diagnostic is for information
only.
(INFO) An automatic reset occurs after
the EST and LST have both risen to
greater than 3oF above the heat tape
temperature setpoint.
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