York Heat Pump: YHJF
Re: Cooling - High Discharge Pressure / High Head Pressure
As the system runs in the cooling mode, the discharge pressure exceeds the normal operating pressure.
R410A System
- Normal Head Pressure = 225 - 350 psig
- High Head Pressure = Above 400 psig
Qty |
Possible Causes (From Most to Least Likely): |
|
Refrigerant Overcharge |
|
Dirty Outdoor Coil |
|
Bad Condenser Motor |
|
Bad Fan Capacitor |
|
Mis-Sized Fan Blade |
|
Bad I/D Expansion Valve |
CHECKOUT:
1. Check Refrigerant Pressures
- Hook-up refrigerant gauges to the pressure ports on the unit.
- Blue --> "True Suction" Port or Suction Line
- Red --> High Pressure (Liquid Line)
- Place an insulated temperature probe on the liquid line near the outdoor unit.
- Allow the unit to run for 5-10 minutes.
- Monitor pressures and temperature as the system operates.
Normal Pressure Range |
Refrigerant |
55-75 Deg O/D |
75-95 Deg O/D |
R410A |
- 110 - 130 Suction
- 225 - 300 Discharge
|
- 125 - 150 Suction
- 250 - 375 Discharge
|
- If the High 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 Sub-Cooling
- Record "Saturation Temperature" from the discharge pressure gauge.
- Subtract the Actual liquid line temperature reading.
- Saturation Temp - Liquid Line Temp = Sub-Cooling
- Normal Subcooling = 4 - 13 Deg
- High Sub-Cooling + High Discharge Pressure + High/Normal Suction Pressure = Overcharged
- High Sub-Cooling + High Discharge Pressure + Low Suction Pressure = Bad Indoor Expansion Valve
- Low Sub-Cooling + High Discharge Pressure + Hot Liquid Line = Dirty Outdoor Coil or Mis-Sized Fan Blade ⇒ Clean the coil, allow to dry 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.