Section 5 – SR-2 Diagnostics
24 HEATING CYCLE FAULT
Page 1 of 1
Alarm Type
Shutdown Alarm
Associated Alarm
Codes
Alarm Code 21 Heating Cycle Check
How Alarm is Set
Alarm indicates that the unit was operating with a cooling ∆T while operating in heat mode. This alarm is preceded
by Alarm Code 22 Heating Cycle Check.
How Alarm is Cleared
This alarm is cleared manually. It is typically preceded by Alarm Code 22 Heat Cycle Check alarm.
If restarts are disabled Alarm Code 24 will be set as a shutdown alarm on the first occurrence of the alarm.
Considerations
1. This is a Shutdown alarm. It is typically preceded by Alarm Code 23 Heating Cycle Check alarm.
2. If restarts are disabled Alarm Code 24 will be set as a shutdown alarm on the first occurrence of the alarm.
Diagnostic Procedure
Download and review the ServiceWatch data logger using Technician Level to determine the conditions at the time
the alarm was set.
1. Check temperature differential by displaying the temperature differential, or by checking the difference
between the control return and control discharge sensors.
2. Check refrigerant level.
3. Attach gauges and evaluate unit refrigeration system performance.
4. Verify that sensor grades are set correctly.
5. Check for proper air flow. Short cycling, caused by a blocked air flow path, may generate this code.
6. Check the three-way valve. A defective valve that does not shift to the heating position may cause this
alarm.
7. Check the pilot solenoid valve. A defective valve will prevent the three-way valve from shifting to the
heating position.
5-34
02 February 2005
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