York Heat Pump: YEE

Re: Low Suction Pressure - Code 5 (Heating)

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

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