Heat Pump - High Pressure (Cooling)

Heat Pump: Cooling

Re: High Discharge Pressure / High Head Pressure

As the system runs in the cooling mode, the discharge pressure exceeds the normal operating pressure.

R22 System

• Normal Head Pressure = 175 - 250 psig
• High Head Pressure = Above 275 psig

R410A System

• Normal Head Pressure = 225 - 350 psig
• High Head Pressure = Above 400 psig

CHECKOUT:

1. 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 between the outdoor coil & indoor expansion valve.
• 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 Condenser Fan Operation

2. 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 + High/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 = Dirty Outdoor Coil or Mis-Sized Fan Blade --> Clean the coil and re-check.

3. Check Condenser Motor & Capacitor

• Disconnect power to the outdoor unit by pulling the service disconnect.
• Test the fan capacitor.
  • Replace the capacitor if less than 20% of rated capacity.
• Re-apply power and check the fan motor amperage.
• Observe the motor operation and check for unusual noises (bad bearings) or excessive temperature.