RHA - Defrost Problem / Outdoor Coil Frozen

Amana Heat Pump: RHA

Re: Defrost Problem / Outdoor Coil Frozen

The Amana RHA Heat Pump uses a Time & Temperature Defrost Board.

• A defrost thermostat mounted to the outdoor coil closes at approximately 30 deg. and opens at approximately 60 deg.
• An adjustable setting on the board allows adjustment of the time between defrost cycles to either 30, 60 or 90 minutes.
• When the board receives 24VAC on the "HOLD" and "24V" terminals the timer starts. When the compressor runtime exceeds the set defrost time a defrost cycle will be initiated.

CHECKOUT:

1. Check Operating Status

• Set the thermostat to call for heat.
• Ensure that the compressor and outdoor fan start and run properly.
  • No Outdoor Fan Operation → Step 2. Check Fan Motor
  • Compressor & Outdoor Fan Ok → Step 3. Check Defrost

2. Check Fan Motor

• With the compressor operating, use a multi-meter to check for 230VAC power between the motor's power wires (COM at the capacitor and Term#4 at the Defrost Relay).
  • No Power = Bad Defrost Board or In Defrost Mode
  • Power + No Fan Operation = Bad Fan Motor or Capacitor

3. Check Defrost

• Defrost Stat
• Check for 24VAC between "COM" and "24V" at the defrost board.
  • Power Present = Defrost Stat Closed (Ready for Defrost) ⇒ Defrost Board & Relay (below)
  • 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 "HOLD" and "24V".
• Defrost Board and Relay
• Speed-up the timer by jumping the Test pins on the defrost board (A defrost cycle should initiate within 5 seconds).
  • Defrost Initiates → Step 4. Check Refrigerant Charge
  • No Defrost Cycle = Bad Defrost Board or Bad Defrost Relay
    • Place a jumper between "COM" and "OUT" at the Defrost Board  (The Defrost Relay should energize immediately).
      • Relay Energizes = Bad Defrost Board
      • Relay Does Not Energize = Bad Defrost Relay

4. Check Refrigerant Charge

• Hook-up refrigerant gauges to the pressure ports on the unit.
  • Blue ⇒ "True Suction" (Not the Suction Line)
  • Red ⇒ High Pressure (either refrigerant line)
• Monitor pressures as the system operates.
• DO NOT ATTEMPT TO ADD FREON IF THE COIL IS FROZEN.

• Low Pressure Issues
  • Low Suction + Low Discharge + O/D Metering Device Frosting = Low Refrigerant Charge