Status
System will shutdown if running to protect compressor and refrigerant circuit
Description
The high side pressure has exceeded the maximum allowed.
Expected Operation
Shutdown, will restart when pressure drops. If same fault occurs 3 times in a single call, unit will lockout for 4 hours.
Cause
1. The pressure switch input to the compressor drive is disconnected or the pressure switch output from the UODC controller is disconnected.
2. Low airflow at the indoor unit, too much refrigerant charge or closed expansion valves.
3. The pressure switch itself has failed.
Solution
1. Check for blocked or dirty indoor or outdoor coil. Clean, if necessary.
2. Check liquid/suction pressures and make sure system is NOT over-charged. Adjust charge/pressures, if necessary.
3. During operation, measure voltage to "HPS" terminal on UODC controller. 24VAC should be present at the start of the cooling or heating cycle. If no 24VAC present, check wiring. For legacy systems, 24VAC should be present on the Y1 input of the UODC controller. For communicating systems, 24VAC should be present on the "R" terminal of the UODC controller. If voltage is not present at these prescribed terminals, check system and repair wiring or other issues preventing 24VAC on the proper input.
4. Replace Compressor Drive Controller.