Refrigeration Control?
Using A High Pressure Control?

Using a high pressure refrigeration control?

High pressure controls on refrigeration equipment safeguard the equipment.

In the event the pressure rises above a preset limit, the control contacts open stopping the compressor.

Some controls must be manually reset. Others automatically reset when the pressure returns to a safe level.

I use manual reset high pressure controls on all condensing units. If the unit trips out on high pressure, I want to know why.

Automatic high pressure controls continue to cycle on and off. Damage to the system can result.

What are some common problems I've encountered with high pressure controls?

1. Blown Bellows: If you remove the cover from a high pressure control and find refrigerant oil, you have blown bellows. Replace the control. Blown bellows cannot be repaired.

2. Broken Cap Tube: Vibration over time can cause the cap tube to crack or break. Once again, look for refrigerant oil.

3. Corrosion: If the control is exposed to the weather or a harsh environment, the trip mechanism can become corroded.


I never repair an older control. When it fails, I replace it. I've had too many repeat service calls because of repaired pressure controls.

What about newer controls? It depends on the problem.

If the cap tube cracks or breaks, find out why. Is it rubbing against another cap tube? Is the compressor vibrating badly? How about a condenser fan off balance?

After finding the problem, I repair the leaking cap tube.

Newer controls with switch mechanism problems are replaced.

What about setting the control to properly monitor the high side pressure?

I set the high pressure control around 100 psi above the normal operating pressure. This lessens the possibility of nuisance trips while assuring protection of the equipment.

Remember, resetting the high pressure refrigeration control usually indicates a problem.

What should you look for?

Check the condenser coil for dirt or trash.

Is the condenser fan motor running correctly? Correct amperage? Correct rotation? Correct fan blade?

Is the control set correctly?

A properly installed high side pressure control is a must. It protects and extends the life of the refrigeration equipment!

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