York Heat Pump: Heating

Re: High Pressure Fault - Last Mode Heat Pump

The heat pump was running in normal heat mode (not in defrost) 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 Indoor Airflow

• Set the thermostat to call for heat.
• Confirm that the indoor fan is operating and air is blowing out of the supply registers
  • No Airflow → Step 2. Check Blower Motor
  • Airflow → Step 3. Check Refrigerant Pressures

2. Check Blower Motor

• The YZE & YZH heat pumps should be matched with a Variable Speed Indoor Blower.
• At the air handler, confirm that 240VAC is being supplied to the motor.
• Confirm that 24VAC is present between "C" and "G", "Y1" or "Y2".
  • No 24VAC Power = No signal from thermostat
  • 240V Power Present + 24V Power Present + No Blower Operation = Bad Blower Motor or Bad CFM Board

3. Check Refrigerant Pressures

• Hook-up refrigerant gauges to the pressure ports on the unit.
  • Blue ⇒ "True Suction" Low Pressure
  • Red ⇒ High Pressure (either refrigerant line)
• Place an insulated temperature probe on the liquid line near the outdoor unit.
• If the heat pump is in lockout (still flashing a code), reset by removing 24VAC power to the outdoor control board (remove "R" or cycle power to the air handler).
• Initiate a call for heat from the thermostat.
• 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 Indoor Blower → Step 6. Check Air Filter & Indoor Coil
  • 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 (Gauge) Temp - Liquid Line Temp = Sub-Cooling
    • Sub-Cooling > 13 deg. + High Discharge Pressure + Normal Suction Pressure = Overcharged
    • Sub-Cooling > 13 deg. + High Discharge Pressure + Low Suction Pressure = Bad Expansion Valve
    • Sub-Cooling < 2 deg. + High Discharge Pressure + Hot Liquid Line = Low Indoor Heat Transfer → Step 5. Check Heat Pump Temperature Rise
    • Sub-Cooling < 13 deg. + Normal Discharge Pressure + Normal Suction Pressure ⇒ Suspect a Failing Blower Motor, a Bad High Pressure Switch or a Sticking Contactor

5. Check Heat Pump Temperature Rise

• Check to make sure the indoor fan is operating.
• Disconnect auxiliary heat (remove "W" at the air handler or thermostat).
• Check the Return Air Temperature at the air handler (at the filter if possible).
  • High Return Air Temperature (more than 85 deg.) = Heat Recycling
• Check the Supply Air Temperature near the air handler (in a straight duct run if possible).
• Calculate the Temperature Rise = Supply Air Temperature - Return Air Temperature
  • Normal Heat Pump Temperature Rise = 15 - 20 deg.
    • High Temperature Rise = Low Airflow → Step 6. Check Air Filter & Indoor Coil

6. Check Air Filter & Indoor Coil

• Remove Air Filter and Check for a Dirty Indoor Coil
  • If Indoor Coil is OK ⇒ Re-Check Temperature Rise with the filter removed.
    • No Change = Restricted Ductwork or Low Blower Speed → Step 7. Check Duct Static Pressure
    • Temperature Rise Becomes Normal = Clogged Air Filter ⇒ Replace Filter & Re-check Pressures

7. Check Duct Static Pressure

• Check the return static pressure (between the air handler and filter if possible).
• Check the supply static pressure.
  • High Static = Above 0.5" w.c.
    • High Return Static + Low Supply Static = Restricted Return Ductwork
    • Low Return Static + High Supply Static = Restricted Supply Ductwork
  • Static Pressure Normal ⇒ Increase Blower Speed or Clean Blower Wheel