GPH13 - Defrost Problem, Outdoor Coil Frozen

Goodman Heat Pump: GPH13

Re: Defrost Problem, Outdoor Coil Frozen

The Goodman GPH13 Heat Pump uses a Time & Temperature Defrost Board.

► There are two different defrost boards used on these models. 

• PCBDM101 = Simple Time & Temperature Defrost Board
• PCBDM133S = Advanced Time & Temperature Defrost Board with Extra terminals: "Cont" = Output to Contactor, "PS1" & PS2" = Pressure Switch Inputs.

CHECKOUT:

1. Check Operating Status

• Inspect the outdoor coil and condenser fan blade.
  • Make sure that ice has not built-up enough to hit the fan blades.
• If the unit is not already running, set the thermostat to call for heat.
• Ensure that the compressor and outdoor fan start and run properly.
  • Compressor & Outdoor Fan Ok → Step 3. Check Defrost Board and Stat
  • No Outdoor Fan Operation → Step 2. Check Fan Motor

2. Check Fan Motor

• With the compressor operating, use a multi-meter to check for 230VAC power between the motor's Red and Black wires.
  • No Power = Bad Defrost Board or In Defrost Mode
  • Power + No Operation = Bad Fan Motor or Capacitor

3. Check Defrost Board and Stat

• Check for 24VAC between "C" and "R" on the defrost board.
  • No Power = Mis-wired Low Voltage
• Check for 24VAC between "C" and "Y" on the defrost board.
• Check for 24VAC between "C" and "DFT" (not "R-DFT") on the defrost board.
  • Power Present = Defrost Stat Closed, Ready for Defrost
  • No Power = Defrost Stat Open, Not Ready for Defrost
    • Cold Coil + Open Defrost Stat = Bad or Disconnected Defrost Stat
    • Warm Coil + Open Defrost Stat ⇒ It may be necessary to temporarily bypass the stat by placing a jumper across "R" and "DFT".
• Speed-up the timer by jumping the Test pins on the defrost board.
  • A defrost cycle should initiate within 5 seconds.
    • Closed Defrost Stat + No Defrost Cycle = Bad Defrost Board
    • Initiates Defrost + Terminates Too Quickly = Wrong Stat Location (Should be on a coil feeder line between the metering device and coil)
    • Normal Defrost Cycle ⇒ Check refrigerant pressures in defrost mode: Should come-up to approx. 300-350psi (Head) and at least 100psi (Suction) to terminate.
      • If pressures are correct, check the Defrost Time setting: Should be on 30 or 60 (not 90).

4. Check Refrigerant Charge

• Hook-up refrigerant gauges to the pressure ports on the unit.
  • Blue ⇒ Suction Pressure Port
  • Red ⇒ High Pressure Port
• Monitor pressures as the system operates.
• Do Not attempt to add freon while the coil is frozen!

• Low Pressure Issues
  • Low Suction + Low Discharge + Expansion Valve Frosting = Low Refrigerant Charge 
    • 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 Expansion Valve
  • Low Suction + High Discharge + Expansion Valve Frosting = Bad Expansion Valve