5hp Saylor Beall motors Safety Switch Trips A Few Seconds After Cut In

by Ben Stikeleather
(Durham NC)

Compressor is a 5hp Saylor Beall 700 series. Apologies for the following being long winded.

I purchased this compressor used and worked fine for a few months and then started tripping the breaker at cut in. Instead of having a tech come look at it right then I just started using my shopmates compressor and eventually forgot to have mine looked at-until.......

Recently I moved into a new shop space having to leave the working compressor behind.

Once the new electrical service was in place the compressor filled the tank no problem so I assumed whatever had been wrong had worked itself out.

I soon discovered that it hadn't and when it tried cut in when it dropped to 90 psi the motor's safety reset tripped. Call compressor tech #1.

He finds a bad cap and replaces it but still is not fixed as the motor still bogs down and trips at cut in.

He suspects because of the age of the building that I'm not getting a full 240 volts. My electrician already had told me the building was only getting 208 volts but that the 220V motors on the machines I had were fine to run as low as 190V. Tech #1 leaves and I call my electrician.

He comes back to check the motor. We disconect the belts and it turns on with no problem. All meter reading look normal as well. We both assume something is up with the pump. Call tech #2.

Tech #2 also is convinced that the problem is with the buildings low voltage and also the length of the wire run from the panel to the compressor which is maybe 100 feet saying that it just doesn't have enough current to turn the pump when it's under load. I try to explain it was doing the same thing at my other shop when it was right next to the electrical panel. So......

Call my electrician to come and install a boost transformer. Meter reading says that should do the trick, also added a larger 50A breaker for good measure. Switch it on
with about 100psi in the tank-same old story, it tripped.

I drain the tank completely and it starts and runs fine to its 150psi cut out. Meter shows voltage in the 220's while running and drawing 18-19A in the lower psi's, 21-22A in the higher psi range. I then bleed the tank to it's 90psi cut in and it works fine. Confused but happy I repeat this 4 more time to make sure it isn't a fluke and the meter shows the amperage draw a little lower with each subsequent cycle. So all's well right? No.

I go back about 90 minutes later and bleed the tank to 90 psi-the motor bogs and trips at cut in. I drain the tank and it starts fine at 0psi and fills to the 150psi cut out but when it tried to cut in at 90psi it was back to square one.

So.....why in the world would it seemingly work fine and then an a little over an hour later not?

Also it will cut in fine starting at around 60psi so I guess if worse comes to worse I could adjust the pressure switch for that and be done with it.

I'm only running one spray gun and one d/a sander and not at the same time but I'd really like to know what's going on. From what I've read about unloader valves I think it's doing it's job? Could it really be something that easy?
Ben it might be the unloader. Dump all the air from the tank, start the compressor, and ensure that the unloader valve works when the compressor reaches cut out and stops.

That doesn't explain why it works sometimes and other times not.

With an empty tank, remove and thoroughly clean the tank check valve too. That might be a contributing factor.

If the caps are fine, and the compressor doesn't start easily under load, and the pump is working properly then it might be just that the motor is tired.

I hope other Saylor Beall air compressor owners can chime in here with suggestions.

Good luck.


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