A021_A: Restricted Airflow-Possible Frozen Coil
Status
This is a critical alarm, it can occur on both air handlers or furnaces
Description
At the start of cooling, the air handler suction temperature will be monitored. If the air handler suction temperature is not available because this is a gas furnace, the outdoor unit suction temperature will be used. If it remains less than or equal to 37°F for 900 seconds (15 minutes), a filter check will be performed.
Cooling will be turned off, and the indoor fan will be driven to the filter check speed.
The static pressure will then be compared against the last static measured for the filter check. If it has risen 0.2 inches above the last filter check, a frozen coil will be declared and an Alert will be set.
Cooling will remain off for 15 minutes while fan is running, the suction temperature will be checked to see if it is greater than 42F. If so, cooling will resume. If not, the fan will continue to run for up to 1 hour, where cooling will resume. If the static pressure has not risen the 0.2 inches, cooling will resume after the short cycle timer has expired.
Cause
Change in suction temperature and airflow static.
Solution
Defrost indoor coil and determine cause of freezing.
