Problem with air compressor

[frugalangler]

Not sure where this should be posted, but I'm needing some help from the great minds here. I've got a typical oil-less 20Gal compressor (C-H IIRC) that when it reaches top pressure and shuts off, it pops the circuit breaker - and it's virtually the only thing on that branch which is a 20A.

IIRC, if I shut if off manually it will not pop the breaker, but if I let it try to with the pressure switch, it does. Anyone have any ideas on this?

Attached image of similar 13Gal unit, virtually the same as mine, but mine is 25 years old.

 

[M5farms]

bad pressure switch. Should be able to replace it , the points are probably worn to the point they are sticking

 

[Sawyer Rob]

How many amps on the motor does it say it draws??

It may be maxing out your breaker and an old breaker will trip before a new one does.

SR

 

[MH8675309]

"and an old breaker will trip before a new one does." my thoughts exactly

 

[frugalangler]

If the pressure switch has a valve that closes before the switch opens then that could be it, putting back-pressure on the compressor and stalling it before the switch opens, I'll see about replacing the switch. I doubt it's the breaker since it will do it on numerous 20A circuits on a couple different panels.

 

[Sawyer Rob]

I'd still like to know how many amps it says it draws, on the motor plate...

SR

 

[frugalangler]

I'd still like to know how many amps it says it draws, on the motor plate...

SR

Sorry took so long to update, since last post, I've changed the run and start caps - no help. I really expected that to help. Still pops the 15A breaker. What's interesting though, it wouldn't reach full pressure and shut off on it's own accord, I had to manually shut it off - or it would run essentially forever getting hotter and hotter in the compressor head.

Now I've finally got the unit back to my 'big' shop. It's labeled at 15A/120V.

I tore into the plumbing on it, found a degraded seal on the unload valve, changed that and corrected all leaks and it will /almost/ reach full pressure now, and doesn't pop a breaker (but I'm on a 20A circuit in the 'big' shop) so progress (I think). At this point, I'm suspecting either the flap valves in the head are degraded or worse yet the cylinder and piston are trashed from lot's of use over the years. At any rate, next I'm gonna pop the head off and inspect the flap valves, if they look deteriorated I'll replace and try again, otherwise I'm torn as to whether it's economically practicable to replace the cylinder and piston (and valves) for just shy of $100 for parts. It's a 3.5HP motor and the compressor being a high RPM kicks a decent CFM compared to current day units.

My other option is to yank it apart, build a frame for mounting the motor sideways on top of the tank, and driving a standalone compressor belt driven. Would be a little work, but in the end w/ this motor I think I can get an even better CFM using a HF replacement two stage compressor.

Opinions?

 

[George2615]

Before you yank it apart have you done an amp draw test with it running. If the compressor runs fine on a 20A circuit but trips on a 15A circuit it may be simply drawing too much current. You need to test to find out if that 15A rating is starting amps or continuous duty running amps. Also check the voltage on the 15A circuit. I had a Porter Cable compressor with a 120V motor and an 8 gallon tank that would not start if voltage was lower than 115V. If Volts were 120-124 it would start and run fine. I had to replace the motor.

 

[frugalangler]

Before you yank it apart have you done an amp draw test with it running.

I actually did that, but forgot to post. Running is 14.8A, it starts fine and will run 'forever' on the 15A circuit, can't catch the starting surge really accurately, but appears to not be excessive. That's why I initially swapped the run and start caps, wanted to make sure that something simple like that wasn't the culprit. As I posted, starts and runs and builds pressure, but just doesn't now get to the trigger point to shut it off, gets just shy at about 108PSI where shutoff on this one is 115PSI.

I'm just not thrilled about sinking more money into a 20 year old oil-less, (and, btw, the pic I posted is not the exact model I just noticed, corrected one is: ) the repair parts are nearly what a new HF oil-less of similar CFM (slightly less, but close) would cost. But, this motor is a heavy one, not anything like the little mouse motors in the new ones, and the tank is good, so I'd rather retrofit it w/ a new traditional pump - at least I think?

 

[George2615]

If your continuous running amps are 14.8 you are maxing out a 15A circuit which will cause premature breaker failure. The FLA of the motor are probably higher than the 15A breaker is rated for. I am not an electrician but I'd run that compressor on a 20A circuit.

 

[not2old]

What else is about to quit? I'm aware of more than one old compressor where the tank sprung a leak and they aren't worth repairing. I recently repaired an old compressor using a propane tank as a replacement and won't do it again as I didn't save enough money to bother with. I'd save the motor and buy a new compressor.

 

[PILOON]

FYI, oil less compressors use a plastic or perhaps Teflon rings that wear out rather in short order.
Generally they consider the lifespan to be 500 hrs vs oil sump with steel rings are quoted at about 2000 hrs.
Otherwise stated the 'oil less' are not a HD compressor, ok for casual homeowner projects and tire inflation etc but not what any contractor or busy shop should consider.

LOL, then there was the early 'handyman' compressors that actually used a rubberized diaphragm that rarely could get decent pressures and would wear out in rather short order. (you only can flex rubber so much)