Air compressor keeps tripping breaker

[wazzabie]

I have a 120v 15amp sears air compressor that keeps tripping the breaker. It is on a shared line.

I also have a dedicated 120v 20amp line. Can I run this on 20 amps?

 

[TuxThePenguin]

It is probably "15 amp" in that it's sized to be run on a 15 amp circuit. Probably more like 9-12 amps reality. Should run on a 20a circuit. Note that 120v products intended for circuits > 20A are rare because basically nobody has >20A 120v breakers in their house (they aren't suitable for general purpose circuits, and people who are putting in a dedicated air compressor circuit would use 240v, not 120v 30a).

If you're thinking the 20 amp circuit might deliver too much current, well the circuits have a maximum current, not a specific current.

Try it on the dedicated circuit for sure... if it still trips, you might have a bad capacitor or something like that.

 

[Chilliwack Murray]

Electric motors draw more current as voltage drops. If this is new issue you likely have a loose connection somewhere causing a voltage drop.

Step 1 is to measure voltage at the motor. If it’s low work back from there.

 

[engineer2]

If it was working before, but now it's not, your might have a bad motor capacitor. Easy fix.

 

[wazzabie]

It was tripping breakers before.

 

[sberry]

15 is the minimum circuit. It was made to run on 20.

 

[Blkhawk870]

What else is on the 15 amp shared circuit? Depending on your model, it may be right at the 15 amp threshold of your breaker and any other load could cause the circuit to trip. The 120v 20 amp dedicated circuit is the way to go. If it trips that breaker than you definitely have a problem with the compressor.

 

[Leaflessshadetree]

My sears compressor will trip 15A breakers as well. It runs for a minute or two then the breaketr trips..
It didn't trip the 15A fuse in the garage it came from (had been there for decades).
It also doesn't trip a 20A breaker (and yes I wired for 20A).

My guess is that circuit breakers are more sensitive than fuses and the compressor is running at the limit.

 

[wazzabie]

when the circuit breaker trips it is difficult to switch the breaker to the back on position.

also two outlets on the 15amp shared line are no longer working. that is a recent change.

 

[TuxThePenguin]

when the circuit breaker trips it is difficult to switch the breaker to the back on position.

How hard?

You are turning the compressor off before you try to switch the breaker back on, right? (This might seem obvious, and probably should be, but some people are pretty unfamiliar with this stuff and it never hurts to make sure)

Are you flipping the tripped breaker off before you try to flip it back on? This typically is what you would do and if you're trying to flip it straight back to on, maybe that would be excessively difficult.

What kind of panel (both brand and series e.g. Square D Homeline, Eaton/Bryant BR, Eaton/Cutler-Hammer CH, etc.) and what is the age of the panel?

Does it make any difference if you wait a minute after it trips (or are you already doing so)?

Have other breakers of yours tripped and are other breakers in your box easier to reset?

You said it's a shared line - what's on it? If you've got other stuff still hooked up, it'll be harder to reset. Turn off or temporarily unplug most or all of the stuff on the circuit before you reset the breaker and see if that helps.

 

[Citation]

Is the panel breaker a 15A or 20A? Second, is this a relatively new thing? My guess is either the starter cap, the run cap or the centrifugal switch. In general I think they design these compressors to be happy on a 15A breaker. If it was meant to need a 20A breaker it likely would have the 20A plug type (the one where the two prongs are perpendicular).

Also, if it starts then trips after building a bit of pressure that suggests a problem with either the centrifugal switch or the run cap. Both are fixable issues.

If it were tripping at start up (like the motor doesn't make a complete revolution) I would look at the oil weight (not really a summer issue), the starter cap or the unloader valve.

 

[wazzabie]

It trips the breaker not at startup but after the compression has built up past 60 psi.

I have not tried the air compressor on the 20 Amp yet.

The shared 15 Amp includes lights and outlets in the house.

The panel is a Sylvania non Zinsco design. The panel was installed in the early 80s.
https://inspectapedia.com/electric/Sylvania-Electrical-Panel-Identification.php

The other breakers have not tripped.

 

[Rinspeed]

After a while some breakers start to get weak and should be replaced. On another note anyone who owns a house or vehicle should own a multimeter. The Fluke T-5 is a great choice and is fairly cheap for the quality, don't guess when it comes to something electrical.

 

[Citation]

I would certainly try a different outlet to verify this isn't a problem with something else sharing that circuit and thus overloading the line.

Tripping at 60 psi means you are well past "starting" the motor. It might be the run cap. It also could just be a problem with a shared circuit and a high load compressor.

 

[wazzabie]

found out the gfci had tripped also

I ran it on the dedicated 20amp and no problems so far

 

[Citation]

found out the gfci had tripped also

I ran it on the dedicated 20amp and no problems so far

Have you tried it on a second 15A outlet? It's possible that the motor is drawing more current than it should. If you have iffy wiring somewhere in your system you might be seeing a voltage drop that results in excess current as the load on the motor rises. If the compressor came from the factory with a 15A plug I would expect it should be able to run on a 15A breaker if all the wiring between the breaker and outlet is in good condition.