Trane Package Heat Pump: 4WCC

Re: Heating - Flashing Code 4

Code 4 = 4 Low Pressure Switch openings 

► This is a Hard Lockout condition that must be reset by cycling power to the board.

CHECKOUT:

1. Check Refrigerant Pressures

• Hook-up refrigerant gauges to the pressure ports on the unit (in the compressor section on the front-left corner of the unit).
  • Low Pressure = Loss of Charge
• Reset the unit if necessary by cycling power to the unit.
• Allow the unit to run for 5-10 minutes.
• Monitor pressures as the system operates.
  • Normal R410a Heating Suction Pressure =  90 - 150 psig

2. Check Sub-Cooling

• Sub-Cooling
• Check the Liquid Line Temperature near the outdoor coil.
• Record "Saturation Temperature" from the discharge pressure gauge.
  • Sub-Cooling = Saturation Temp - Liquid Line Temp
    • Normal Sub-Cooling = 3 - 12 deg.
• Low Suction Pressure + High Sub-Cooling = Bad O/D Expansion Valve
• Low Suction Pressure + Low Sub-Cooling = Low Refrigerant Charge 

3. Check Discharge Temperature

• Connect a temperature thermistor to the compressor discharge line.
• Allow the system to run for about 10 minutes and watch the actual discharge temperature.
  • Normal Discharge Temperature = 120 - 180 deg F.
  • High Discharge Temperature = Low Refrigerant Charge or Bad O/D Expansion Valve

4. Check Defrost

• Run the unit through a defrost cycle by jumping the Test pins on the defrost board.
• Monitor refrigerant suction pressure through a defrost cycle.
  • Normal Heating Pressure + Low Defrost Pressure = Bad I/D Expansion Valve