York Heat Pump: Cooling

Re: High Pressure Lockout - Last Mode Heat Pump

The heat pump was running in cooling mode and the high pressure switch tripped.

A High Pressure Lockout is indicated by the following LED pattern on the outdoor unit control board:

• Green = Off
• Red = 2 Flashes

X/L Output

• 2 Flashes at Thermostat = Soft Lockout
  • Switch opened two times in 6 hours.
  • Reset by cycling thermostat or jumping Test pins.
• 3 Flashes at Thermostat = Hard Lockout
  • Four Soft Lockouts in 12 hours.
  • Reset by cycling 24VAC power to the board.

CHECKOUT:

1. Check Unit Operation

• Set the thermostat to call for cooling.
  • If the heat pump is in lockout (flashing a code) ⇒ Reset by removing 24VAC power to the outdoor control board (Remove "R" or cycle power to the air handler).
  • Allow 5 minutes for the anti-short-cycle delay or jump the Test pins to bypass the timer.
• Observe the outdoor unit to ensure that the compressor and condenser fan motor start.
  • Unit Starts and Runs Normally → Step 3. Check Refrigerant Pressures
  • Unit Doesn't Start ⇒ Check Control Board Diagnostic Light
    • Flashing a Fault Code = Still Locked-Out
      • Reset by removing and reconnecting "R" and "Y" at the o/d unit control board for at least 5 seconds.
  • If the control board re-enters Code 2 without starting the compressor = Bad Pressure Switch

2. Check O/D Motor & Capacitor

• The YZH unit has an ECM outdoor fan motor, the YZE has a standard PSC motor with a capacitor.
• YZE
• Check Capacitor
  • Turn off power to the unit by pulling the service disconnect or by turning the breaker off.
    • Use a multi-meter to confirm that voltage is not present.
  • Remove the capacitor wires (short terminals before touching).
  • Move Multi-Meter leads to COM and MFD.
  • Set Meter to 200 MFD.
  • At the capacitor, place one meter lead on "C" or "Com" and the other meter lead on "Fan".
  • Confirm MFD reading with capacitor rating.
    • Less than 80% of rating = Bad Capacitor
  • SWITCH METER LEADS BACK TO COM AND V BEFORE PROCEEDING!
• Check Motor
  • Re-apply power to the heat pump.
  • Set the thermostat to call for cool.
  • When the compressor contactor energizes, check for 230V to the motor between "C" or "COM" at the capacitor and the Black motor wire.
    • Power + No Motor Operation = Bad Motor or Capacitor
    • No Power = Bad Control Board 
• YZH
• Re-apply power to the heat pump.
• Set the thermostat to call for cool.
• When the compressor contactor energizes, check for 24V to the motor module between the Blue wire on the contactor coil and the Yellow wire on "ODF" at the control board.
  • Power + No Motor Operation = Bad Motor/Module
  • No Power = Bad Control Board 

3. Check Refrigerant Pressures

• Initiate a call for heat from the thermostat.
• Hook-up refrigerant gauges to the pressure ports on the unit.
  • Blue ⇔ "True Suction" Low Pressure
  • Red ⇔ High Pressure (liquid refrigerant line)

• Place an insulated temperature probe on the liquid line near the outdoor unit.
• 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 = Bad Overcharge or No Outdoor Airflow 
  • If the compressor never kicks on & the control locks-out on Hi Pressure ⇒ Suspect a Bad Pressure Switch

4. 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 Indoor Expansion Valve
    • Sub-Cooling < 2 deg. + High Discharge = Low Outdoor Heat Transfer (Airflow).