Compressor Cycling Repeatedly During Night?

6/6/2025

We have a condominium (3 story, 18 units), with an original 20-year-old Gast model 2LAF-12-M200X.

Complaint from the unit sharing an adjacent wall to the sprinkler room. The compressor repeatedly turns on and off only during the early morning hours, between 2 and 4 AM.

We have monitored and seen nothing but normal activity during the day.

Is this possible?

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11 Comments

Chad

6/6/2025 08:11:07 am

Yes…. Temperatures affect the system pressure. It may be colder at that time.

David Kendrick

6/6/2025 08:22:54 am

Find the leak.
Buy a quieter compressor and don’t find the leak.
Thermal effect is possibly valid when there’s a leak.

MELVIN MAGBANUA link

6/6/2025 08:25:21 am

The unit has been =identified to be 20 years old. When was the last time the pressure gauges/switch has been calibrated? I suggest to start from here before going to the next step.

Rob Stewart link

6/6/2025 08:30:24 am

I would suggest doing the 3 year air leakage test outlined at NFPA 25 2023 in Chapter 13 at 13.4.5.2.9. This will help identify if you have a piping integrity issue. Then you can then look closer at a possible thermal effect issue or a compressor issue.

Jody Aycock

6/6/2025 08:37:15 am

It could be a few things, first make sure there’s not an air leak in the system, second if no air leak check the low air turn on psi for the compressor, it could be set too low, or your pressure switch on the compressor could be going bad.

Bill Harvey

6/6/2025 08:45:07 am

I agree with the other comments, if the compressor is functioning properly and no air leaks are identified I'd suggest adding a riser tank kit and an AMD from General Air Products. This won't fix any psi drop but it will reduce the number of times the compressor kicks in.

Dan Wilder

6/6/2025 08:55:13 am

As this is occurring during the coolest part of the night, you likely have a leak. Thermal expansion through the warming day keeps the pressure up but as things cool down, the pressure sensor trips.

Maintenance on the compressor and verification of the pressure switch operational status is a great start.

Using a licensed FP company, they can check the following (if you have onsite maintenance trying to perform this, there is a chance to trip the valve so OP beware).

1. Isolate the air compressor from the valve and turn off the power to the compressor. If the compressor gauges lose air pressure you know there's a leak on that side. If the system loses air pressure, you have that answer as well.

2. Get some MegaBubble and spray all the joints between the air compressor and the trim of the valve, unions are typically trouble spots. This can be done at any time so no issue with who does this step. Same for couplings and other threaded joints downstream of the valve, any drum drips/aux drains/remote inspectors test locations, and don't forget to check any piping drain points as well (a plug/cap at this location to see if there is any buildup of pressure behind, bubble may not be as apparent at a larger diameter location).

3. As most of the system will be behind walls, items like a ultrasonic listening device to hear the leak if the attic is accessible or use an olfactory method (peppermint or pinesol) to get a possible general location of a leak can also be an option.

Jesse

6/6/2025 09:23:56 am

My guess is there's a leak somewhere. The wramer day leading to some thermal expansion of the air in the system, but then not so much in the cooler evening.

Douglas Krantz link

6/6/2025 03:02:08 pm

There is an air pressure switch on the pump, which is what turns it on. The compressor will not turn on unless the air pressure has decreased.

There are two problems. At night, the pipes are getting colder - the air is losing some pressure. That has been addressed in some of the earlier replies.

That's the cause of the nighttime occurrences,

However, that problem would be fixed because the air becomes warmer during the day, and should make up for the decreased pressure at night.

If there weren't any leakage, the pump would bring up the pressure at night, once, and not turn on again, ever.

There is a leak that is causing the pump to keep replacing the air.

One of the most common causes is pin-hole leaks, at least in older systems. These will gradually get worse, and because the pump isn't able to keep up with the leaks as the leaks get too bad, the system will flood. I've seen that.

Of course, it could be a leak around a bad joint, the pump is leaking, or the dry system valve could be leaking. Something's leaking.

In any case, someone needs to get into the attic, or wherever, and look for the leaks.

Jeff Edick

6/8/2025 06:38:03 am

Sometimes the fastest way to find a leak (after the a/c fittings have been checked), is to schedule a system full trip test. Once the I.T. runs clear close it. Close the control valve also, close off any trim that’s running water too. Get a bright flashlight and begin tracing every pipe, looking for drips. I usually find several on older systems. Mark them, make a stock list, place a quote for repair work,or T&M it. Good luck.

Jack G

6/19/2025 03:43:02 pm

It looks like it’s a quarter hp 50 psi air compressor.
I d check the air control switch ( disconnect and check the on off points say into a 10 gallon tank.
If the switch is bad I d replace it but with a tank mounted air compressor and it may run less if the dry system has no leaks. Also do a 24 hour air test at 50 psi to check how much it drops say from 3 pm to 3 pm so that the early morning temperatures are accounted for.

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Compressor Cycling Repeatedly During Night?

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