Head pressure follows condensing temperature, which rises with outdoor temperature, a dirty condenser coil, a failed condenser fan, overcharge or non-condensables in the system. High head pressure costs capacity and amps and cooks compressors. In cold weather, head pressure can fall too low for the metering device to feed properly, so commercial systems use fan cycling, fan speed control or flooded condensers to hold it up.
Head pressure's 450 on a 90 degree day, the condenser fan isn't spinning, check the cap.
Also heard as
- head
- discharge pressure
- condensing pressure
- high side pressure
Related terms
Condenser
The heat exchanger where hot, high-pressure refrigerant gives up heat and condenses back to a liquid.
High side
The high-pressure half of a refrigeration system, from compressor discharge through condenser to the metering device.
Non-condensables
Air, nitrogen or other gases trapped in a refrigeration system that will not condense at operating conditions.
Cap
Short for capacitor, the part that gives compressor and fan motors the phase shift they need to start and run.