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
| Qty |
Possible Causes: |
| 1 |
Bad Cond Fan Motor/Capacitor |
|
Dirty Condenser Coil |
|
Wrong Cond Fan Motor |
|
Wrong Fan Blade |
|
Bad Metering Device |
|
Refrigerant Over-Charge |
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.
| Normal Pressure Range |
| Freon |
55-70 Deg O/D |
75-90 Deg O/D |
| R-22 |
- 55-70 Suction
- 150-225 Discharge
|
- 70-85 Suction
- 170-260 Discharge
|
| R410A |
- 100-125 Suction
- 250-320 Discharge
|
- 130 -150 Suction
- 250-375 Discharge
|
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