High Head Pressure

Air Conditioner

Re: High Discharge Pressure / High Head Pressure

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

The YCD units typically use an orifice at the indoor coil instead of an expansion valve. Therefore, the sight-glass and sub-cooling readings cannot be used to determine proper charge.

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 --> Suction Line
  • Red --> Liquid Line
• Place an insulated temperature probe on the "suction" 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 or kicks-off on Hi Pressure safety in the first 5 minutes = Refrigerant Overcharge or No Condenser Fan Operation

2. Check Superheat

• Check and Record the Return Air "Wet Bulb" Temperature at the furnace or air handler.
• Check and record the Outdoor Air Temperature.
• Use the Superheat Chart to determine the proper Superheat.
• Record "Evaporation Temperature" from the suction pressure gauge.
• Record the actual suction line temperature.
  • Suction Temperature - Evaporation Temp = Superheat
    • Actual Superheat < Chart + High Discharge Pressure + High/Normal Suction Pressure = Overcharged
    • Actual Superheat > Chart + High Discharge Pressure + Hot Liquid Line = Dirty Outdoor Coil or Re-Circulating Heat --> 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.