Air compressor motor keeps tripping breaker

[e40]

My Porter/Cable compressor (25 gallon, non-oiless) keeps tripping the circuit breaker when I turn it on. I have a dedicated 12AWG/20A non-GFCI circuit going to it. I took the AC motor into a shop to have it looked over, they checked the caps and they were OK. They replaced an electronic component saying it was faulty. (Diodes maybe? Sorry, I don't have the invoice with me now but can check it later)

It still trips the breaker. I brought the motor back and they replaced the same part again, saying it was bad. Perhaps from re-trying to start it over and over? Still does the same thing after getting it home. This happens with the tank empty, or partially charged, doesn't matter.

If I take the belt off, the motor starts fine. Sometimes if I turn the motor / pump over by hand a few revolutions it will start. (With the belt / load attached)

The pressure relief seems to be working, it hisses when the motor/pump stop running. I've also ruled out the pressure switch by directly connecting the AC cord to the motor.

Anything else I can try? It was last working in my old house, it was in storage for about 2 months during my move. It ran fine on a dedicate 20A circuit at the old house as well.

 

[Brian Barnhart]

I know they supposedly checked it, but it still sounds like a bad cap, or connection to the cap. If there is a centrifugal switch associated with the cap, that might be a possibility.

How easy is it to turn the pulley by hand (with the motor unplugged!)?

Might also check the receptacle wiring (for loose or burnt connections). That's important with heavy loads like starting an air compressor.

 

[Rand]

Is the breaker ok? try it on another outlet.

I had a weak breaker that kept popping early.

 

[HerrStig]

Can the motor wiring be reconfigured for 220 V?

 

[Donald]

Originally Posted By: e40
My Porter/Cable compressor (25 gallon, non-oiless) keeps tripping the circuit breaker when I turn it on. I have a dedicated 12AWG/20A non-GFCI circuit going to it. I took the AC motor into a shop to have it looked over, they checked the caps and they were OK. They replaced an electronic component saying it was faulty. (Diodes maybe? Sorry, I don't have the invoice with me now but can check it later)

It still trips the breaker. I brought the motor back and they replaced the same part again, saying it was bad. Perhaps from re-trying to start it over and over? Still does the same thing after getting it home. This happens with the tank empty, or partially charged, doesn't matter.

If I take the belt off, the motor starts fine. Sometimes if I turn the motor / pump over by hand a few revolutions it will start. (With the belt / load attached)

The pressure relief seems to be working, it hisses when the motor/pump stop running. I've also ruled out the pressure switch by directly connecting the AC cord to the motor.

Anything else I can try? It was last working in my old house, it was in storage for about 2 months during my move. It ran fine on a dedicate 20A circuit at the old house as well.


Capacitor? You can check it with an ohm meter (analog is best) or the $40 HF digital multimeter can check for microfarads. Disconnect one side to the capacitor and short across the capacitor before testing.

 

[Dave Sherman]

Originally Posted By: Donald

Capacitor? You can check it with an ohm meter (analog is best) or the $40 HF digital multimeter can check for microfarads. Disconnect one side to the capacitor and short across the capacitor before testing.


You check capacitance with a capacitance meter, not an ohm meter. Though some digital multimeters can do both resistance and capacitance.

 

[e40]

Originally Posted By: Brian Barnhart
How easy is it to turn the pulley by hand (with the motor unplugged!)?


Very easy to turn over..

Originally Posted By: Rand
Is the breaker ok? try it on another outlet


Tried it on at least three circuits. The dedicated 20A for the compressor, the 15A general garage outlet circuit, and I carried it inside to the laundry room and connected it to the 20A washer outlet. All the same.

Originally Posted By: HerrStig
Can the motor wiring be reconfigured for 220 V?


Yes, it can. I could give that a shot..

 

[Noey]

Most compressors need a dedicated 30amp switch. If you're running the house on less than 220, that's a problem. Easier to install a 30amp.

 

[kschachn]

Originally Posted By: Noey
Most compressors need a dedicated 30amp switch. If you're running the house on less than 220, that's a problem. Easier to install a 30amp.


Switch? You mean breaker? And are you suggesting he install a 30A breaker on the (presumably) 12-gauge circuit?

And it's a nominal 240v, not 220. It hasn't been 220 volts in the US, ever.

 

[Donald]

Originally Posted By: Dave Sherman
Originally Posted By: Donald

Capacitor? You can check it with an ohm meter (analog is best) or the $40 HF digital multimeter can check for microfarads. Disconnect one side to the capacitor and short across the capacitor before testing.


You check capacitance with a capacitance meter, not an ohm meter. Though some digital multimeters can do both resistance and capacitance.


With an analog ohm meter you can watch the meter "count up" going slowly from 0 to full scale. Or full scale to 0. While not showing the specific capacity in microfarads, it gives a general idea of whether the capacitor is working.

 

[Chris142]

20a is not enough. It probly pulls 30+ when starting. Been through this with mine.had to have the garage wired for 220.the wiring in the new place may be too small as was mine

 

[pcoxe]

Low voltage will cause excessive current. You have tried it on different circuits with the same result, but It could be a loose power or neutral connection problem with the main panel itself. Plug a 60w lamp in on a different circuit and see how it reacts when the compressor tries to start. It should not have much of a reaction to the compressor starting.

 

[440Magnum]

Did this setup (same compressor, same circuit, same breaker) used to work OK and then started tripping? If so- there's still some fault in the motor, probably the "start" capacitor not disengaging (either due to a bad centrifugal switch or a bad potential relay, which are the two most common ways to kick out a start cap once the motor is running). If its a new setup, then I'd say it needs to be wired for 240, and is just too large a motor to run on a 120 circuit.

 

[e40]

Originally Posted By: 440Magnum
Did this setup (same compressor, same circuit, same breaker) used to work OK and then started tripping? If so- there's still some fault in the motor, probably the "start" capacitor not disengaging (either due to a bad centrifugal switch or a bad potential relay, which are the two most common ways to kick out a start cap once the motor is running). If its a new setup, then I'd say it needs to be wired for 240, and is just too large a motor to run on a 120 circuit.


It's never worked since moving to the new house. But I am wondering if something happened to the compressor motor while in transit / storage from moving? It was in my aircraft hangar over a couple of hot, humid months. As above, it's been fine for 13 years on a 20A / 12AWG supply at my two previous homes. To further eliminate the wiring as a culprit, I could roll it over to my neighbors garage and give it a shot.

I'll also look into testing the potential relay, caps, etc..

 

[Dan55]

What kind of circuit breakers do you have. And is there a ext cord involved.

 

[e40]

New construction, Square-D homeline series breaker. No extension cord, using the direct cord that the compressor came with. Home run to the panel is probably under 5 feet, it's on the other side of the wall.

 

[e40]

I'll also add that the trip occurs before the motor even gets a chance to turn a full revolution. If I recall, it doesn't even move 45 degrees.

 

[440Magnum]

Originally Posted By: e40
I'll also add that the trip occurs before the motor even gets a chance to turn a full revolution. If I recall, it doesn't even move 45 degrees.


That's weird.

Do you have one of those clamp-on inductive ammeters with a "peak hold" function? You could clamp it around the hot wire, set for peak hold, and then let the motor try to start and see what its really drawing. Almost sounds like a dead short somewhere, except for the fact that it starts when not loaded.

Color me a little suspicious of Square-D "homeline" though. Their standard stuff is great, but "homeline" is on the cheap end. Never actually had a problem with it, but then I never have used it in my own home either.

 

[Clevy]

If it's snapping the breaker before making a full revolution you've got a problem with the motor itself.
Electric compressors have a relief valve that is open when the compressor starts up. It reduces initial drag. Once the pump builds a few pounds of pressure this relief closes.
If that relief is stuck closed the motor would have to overcome that resistance which its unable to do and draws too much current blowing the breaker.
Once these breakers snap a few times they get weak.

 

[another Todd]

Is this a new problem on a compressor you have used in this configuration for a while or a new compressor?

Motor checked out good, so check the following.

New compressor: undersized wiring and or breaker, too long of a wiring run from breaker to motor (might require up sizing the wiring), defective circuit breaker, loose or corroded connection, defective start and/or run capacitor if equipped.

New Problem on old compressor: Defective circuit breaker, loose or corroded wiring, defective start and/or run capacitor if equipped.

Good luck.