CHECKOUT

1. Check Outdoor Unit

• Make sure the outdoor coil is not iced-over.
• Unit Operating --> Step 3. Check Compressor Operation
• Unit Not Operating -- Step 2. Check Power

2. Check Power

• Disconnect power to O/D unit by pulling disconnect or turning off breaker.
• Open the electrical compartment cover. 
• Inspect for burnt wiring or burnt contactor contacts.
• Re-apply power to the unit.
• Check for 200 - 240VAC power on the contactor inlet.
  • No Power = Tripped Breaker or Bad Wiring
• Check for 24VAC between "R" and "C" on the defrost control board.
  • No Power = Blown Low Voltage Fuse or Bad Transformer
• Set the Thermostat to call for heat.
  • Check for 24VAC between "Y" and "C" on the defrost control board.
    • No Power = No Call from the Thermostat --> Check Thermostat
    • Power --> Compressor and Condenser Fan should start within 5 minutes --> Step 3. Check Compressor Operation

3. Check Compressor Operation

• Check Compressor Amperage to ensure that the compressor is operating.
  • Amperage --> Step 4. Check Refrigerant Pressures
• Compressor Does Not Try to Start = Safety Lockout or Bad Contactor
  • Check for 24VAC between the Yellow wire on the Y terminal and "C" on the defrost board.
  • Check for 24VAC between both sides of the contactor coil.
    • Power at the defrost board but not the contactor = Open Hi or Lo Pressure Switch
    • Power on both but contactor not pulled in = Bad Contactor
• Compressor Hums but Doesn't Run = Bad Capacitor, Locked-up Compressor, or Burnt Compressor Wiring

4. Check Refrigerant Pressures

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

• Low Pressure Issues
  • Low Suction + Low Discharge + Metering Device Frosting = Low Refrigerant Charge
    • Try adding refrigerant through the Low Pressure gauge.
      • Suction and Discharge Pressures should gradually increase as refrigerant is added.
  • High Pressure Issues
    • Place an insulated temperature probe on the liquid line.
    • Allow the unit to run for at least 10 minutes.
    • Monitor pressures and temperature as the system operates.
      • If pressure exceeds Normal Range or kicks-off on Hi Pressure safety in the first 5 minutes = Refrigerant Overcharge or No Indoor Blower
    • Check Sub-Cooling
      • Record "Saturation Temperature" from the discharge pressure gauge.
      • Subtract the Actual liquid line temperature reading.
        • Saturation Temp - Liquid Line Temp = Sub-Cooling
          • Sub-Cooling > 13 deg. + High Discharge + High Suction = Overcharged
          • Sub-Cooling > 13 deg. + High Discharge + Low Suction = Bad Expansion Valve
          • Sub-Cooling < 2 deg. + High Discharge = Low Indoor Heat Transfer --> Step 6. Check Air Temperature Rise

5. Check Compressor Discharge Temperature

• Use a multi-meter to check the temperature of the compressor discharge line.
• Normal Temperature = 120 - 150 deg.
  • Low Discharge Temp = Inefficient Operation

6. Check Air Temperature Rise

• With the auxiliary heaters disconnected (remove "W1" and "W2" form the air handler terminal block):
  • Check the Return Air Temperature near the unit or in the filter compartment.
  • Check the Supply Air Temperature.
  • Normal Temperature Rise = 15-20 deg.
    • Abnormally Low Return Air Temperature --> Check Return Ductwork for Cold Air Infiltration
    • Low Temperature Rise = Inefficient Operation
    • High Temperature Rise = Low Airflow
  • RE-HOOK "W1" AND "W2" WIRES ON THE AIR HANDLER!