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YHE/YHG - Code 3 - High Pressure - Heating

Article ID: 596
Last updated: 29 Dec, 2021

York YHE / YHG 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.

High Pressure Lockout is indicated by a 3-Flash LED pattern on the outdoor unit control board.


X/L Output


Qty Possible Causes:
1 Refrigerant OverCharge
  Bad O/D Expansion Valve
Bad Blower Motor / Capacitor
Low Indoor Airflow
Refrigerant Restriction
Bad Pressure Switch


CHECKOUT:

1. Check Indoor Airflow


2. Check Blower Motor

  • At the air handler, confirm that 24VAC is present between "C" and "G", "Y1" or "Y2".
    • No 24VAC power = No signal from thermostat
  • Confirm that 240VAC is being supplied to the motor.
    • 240V Power Present + No Blower Operation = Bad Blower Motor 

3. Check Refrigerant Pressures

  • If the heat pump is in lockout, reset by removing 24VAC power to the outdoor control board.
  • 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 (small liquid 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 and kicks-off on Hi Pressure safety in the first 5 minutes = Bad Overcharge or No Indoor Blower
    • 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 Pressure + Normal Suction Pressure = Overcharged
      • Sub-Cooling > 13 deg. + High Discharge Pressure + Low Suction Pressure = Bad O/D Expansion Valve
      • Sub-Cooling < 2 deg. + High Discharge Pressure + Hot Liquid Line = Low Indoor Heat Transfer → Step 5. Check Heat Pump Temperature Rise

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

6. Check Indoor Airflow

  • 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
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Article ID: 596
Last updated: 29 Dec, 2021
Revision: 8
Views: 110
Comments: 0
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