HHP - Outdoor Coil Frozen/Won't Defrost

Heil Heat Pump: HHP

Re: Not Defrosting / Frozen

The HHP models use a Time & Temperature control board.

The board uses a Coil Thermostat and Timer to determine the proper conditions for defrost to occur (timer adjustable for 30, 60 or 90 minutes).

CHECKOUT:

1. Check Outdoor Fan

• Inspect the outdoor unit and make sure the outdoor fan is operating normally.
  • Fan Operating → Step 2. Test Defrost Cycle
  • No Fan ⇒ Check for 230VAC to the fan motor.
    • No Power = Bad Control Board or Unit in Defrost
    • Power + No Fan = Bad Condenser Motor or Capacitor ⇒ Check Capacitor

2. Test Defrost Cycle

• Jump the TEST pins to force the unit into defrost (hold TEST pins until the unit enters defrost then quickly remove TEST pins).
  • Defrost Cycle Initiates & Terminates Normally → Step 4. Check Refrigerant Pressures
  • Unit Will Not Initiate Defrost → Step 3. Check Defrost Stat

3. Check Defrost Stat

• Place a jumper across the two Black wires connected to "DF" on the defrost board.
• Use the TEST pins to force the unit into a defrost (remove TEST pins one defrost initiates).
  • Unit Enters Defrost Normally = Bad Defrost Stat ⇒ Confirm by removing the two Black wires from "DF" and checking resistance.
  • Unit Still Won't Enter Defrost = Bad Defrost Board or No 24V Power on Board ⇒ Check for 24V power between "R" and "C".

4. Check Refrigerant Pressures

• Hook-up refrigerant gauges to the pressure ports on the unit.
  • Blue --> "True Suction" Low Pressure
  • Red --> High Pressure (either refrigerant line)
• Monitor pressures as the system operates.

• Low Pressure Issues
  • Low Suction + Low Discharge + Expansion Valve Frosting = Low Refrigerant Charge or Bad O/D Expansion Valve
    • Try adding refrigerant through the Low Pressure gauge.
      • Suction and Discharge Pressures should gradually increase as refrigerant is added.
      • If the Discharge Pressure increases but the Suction Stays Low or Drops = Bad O/D Expansion Valve