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YEE - Fault Code 5 (Heating)

Article ID: 714
Last updated: 30 Apr, 2024

York Heat Pump: YEE

Re: Low Suction Pressure - Code 5 (Heating)

CODE 5 = Low Pressure Switch Opened (2x in 6 hours)

Qty Possible Causes:
2 Low Refrigerant Charge
Bad Expansion O/D Valve
Bad Pressure Switch
Not Defrosting

CHECKOUT:

1. Check Refrigerant Pressures

  • Pull the service disconnect.
  • Make sure the outdoor coil is not frozen-over.
    • Frozen coil = Not Defrosting
  • Hook-up refrigerant gauges to the pressure ports on the unit.
    • Blue  True Suction (Not Suction Line)
    • Red Liquid Line Pressure Port
      • Low Standing Pressure (both sides) = Loss of Charge
      • Normal Pressures ⇒ Continue
  • Start the unit.
    • Re-Insert the service disconnect.
    • Reset the lockout (if necessary) by pulling "R" and "Y".
    • Bypass the Anti-Short-Cycle Delay by jumping the Test pins.
      • Normal Pressure + Code 5 Again = Bad Pressure Switch
  • Allow the unit to run for 5-10 minutes.
  • Monitor pressures as the system operates.
    • Normal R410a Suction Pressure =  100 - 150 psig

2. Check Suction Pressure & Sub-Cooling

  • Sub-Cooling
  • Check the Liquid Line Temperature near the outdoor unit.
  • Record "Saturation Temperature" from the discharge pressure gauge.
    • Sub-Cooling = Saturation Temp - Liquid Line Temp
      • Normal Sub-Cooling = 3 - 12 deg. (Sight-Glass Clear)
  • Low Suction Pressure + High Sub-Cooling (Clear Sight Glass) = Bad O/D Expansion Valve
  • Low Suction Pressure + Low Sub-Cooling (Bubbles in Sight Glass) = Low Refrigerant Charge 
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Article ID: 714
Last updated: 30 Apr, 2024
Revision: 4
Access: Public
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