NAC - High Pressure/Low Cool/Outdoor Fan Not Running

ICP/Heil Air Conditioner: NAC

Re: High Head Pressure / Low Cooling / Outdoor Fan Not Running

Especially during high ambient temperature conditions, the air conditioner exhibits the following conditions:

• High head pressure
• Hot liquid line
• Low cooling output

CHECKOUT:

1. Check Outdoor Fan

• Check the fan motor on the outdoor unit.
  • Many of these units require a "short-body" condenser fan motor.
  • If a "short-body" motor has been replaced with a standard motor, it may place the fan blade too low in the coil and cause high pressure issues.
• Set the thermostat to call for cooling.
• Inspect the outdoor unit and make sure the outdoor fan is operating.
  • Fan Operating → Step 2. Check Pressures
  • Fan not Operating ⇒ Check for 230VAC going to the fan motor.
    • No Power = Bad Contactor or No Call for Cool
    • Power Present + No Fan Operation ⇒ Check for Bad Capacitor
      • Power Present + Capacitor OK + No Fan Operation = Bad or Mis-Wired Fan Motor

2. Check Pressures

• Hook-up refrigerant gauges to the pressure ports on the unit.
• Monitor pressures as the system operates.

High Pressure Issues

• Place an insulated temperature probe on the liquid 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
• Check Sub-Cooling
  • Record "Saturation Temperature" from the discharge pressure gauge.
  • Subtract the Actual liquid line temperature reading.
    • Sub-Cooling = Saturation Temp - Liquid Line Temp
      • Sub-Cooling > 13 deg. + High Discharge + High Suction = Refrigerant Overcharge
      • Sub-Cooling > 13 deg. + High Discharge + Low Suction = Bad Metering Device
      • Sub-Cooling < 2 deg. + High Discharge = Low Outdoor Heat Transfer ⇒ Clean Condenser Coil & Recheck Sub-Cooling after 10 min.
        • Improved conditions = Dirty Condenser Coil
        • Same Conditions = Wrong Motor or Wrong Fan Blade