Compressor Trips The Breaker On Restart

You’ve got a full tank of air, start using your air tool, and as the pressure in the tank drops to the cut in pressure setting, the compressor trips the breaker on restart, or blows the fuse when attempting to restart.

What’s happening on our air compressor when this occurs and what can you do about it?

When the air compressor tank is drained down to the cut in pressure level, the compressor should start and run until the compressor tank pressure has reached the cut out setting at which time the compressor should stop.

At the cut in pressure setting the compressor pressure switch contacts will close and power will flow through the pressure switch to the motor start circuit, typically a start capacitor.

If for some reason the motor cannot start, it will continue to draw power, and may pull enough amperage to exceed the capacity of breaker and as a result the compressor trips the breaker on restart.

Compressor breaker trips on restart - tripped electrical breaker

 

Things to check when your air compressor trips the breaker on restart

Did the unloader valve work? – Sometimes the unloader valve fails, and as a result, some compressed air is trapped over the cylinder piston. That trapped air adds to the load the compressor motor experiences on start up, and that additional load may be enough to force the motor into pulling too many amps and popping the breaker, or blowing the fuse.

To test for this, unplug the compressor, open the tank drain and drain all the air out of the compressor tank (which you should do after every use of your air compressor as part of the regular preventive maintenance), plug the compressor back in and if your compressor has one, flip the ON/OFF switch to on.

Square-D compressor unloader valve

If the compressor starts this time and the breaker doesn’t pop, that suggests that your air compressor unloader valve is not working properly, one of which made by Square-D is shown in the image above, and you need to either fix it or replace it. To be sure, shut off the compressor, drain the tank again, and try to restart it with an empty tank. If the compressor starts easily again, then it’s pretty much certain that it’s the air compressor unloader valve failure that is causing your air compressor to trip the breaker on restart.

Are you plugging the air compressor into a power bar or extension cord? Home use extension cords are notorious for throttling power, as is a power bar. You may be under powering your compressor motor, and the resulting overheated motor may be contributing to the breaker tripping when the compressor starts.

Leave the compressor to cool for 15 minutes or so, and then try plugging the air compressor power cord directly into a wall socket, preferably one that has a 20 amp breaker, and has no other electrical devices using power at the same time as the air compressor is trying to start.

If the compressor starts this time, and after you have used some air and the compressor successfully restarts when the tank pressure drops to the cut in pressure setting, then you’ve nailed down the problem.

As a general rule we suggest that you add air hose to get the compressed air to your work station as opposed to using an extension cord to move the compressor closer to where you want to use compressed air. Nothing gets damaged if it doesn’t get enough air through a long hose. On the other hand, electrical devices are overworked if their power supply isn’t up to what is required leading to electrical maintenance issues.

Is it the pressure switch itself that has failed? Less likely, but still possible, that your air compressor trips the breaker on restart can be cause by a pressure switch that has shorted out.

When the air pressure in the tank drops, a diaphragm inside the pressure switch moves, and ultimately, that moving diaphragm forces the points inside the pressure switch to touch, a circuit is made, and power flows to the compressor motor starting it, and driving the pump to pump more air into the compressor tank.

Turn off or unplug the compressor.

Drain the compressor tank and then close the drain.

With due regard to the presence of live terminals inside the pressure switch, pull the cover off,  reset the breaker, and watch inside the pressure switch to see if there is any arcing or sparking when you turn the compressor back on.

Since the pressure switch points should already be touching with the absence of air in the tank, there should not be any arcs or sparks, and if there are, that’s a pretty good indication that you pressure switch may be the problem.

You will need to replace the pressure switch.

Capacitor Failure?

If the compressor has a start capacitor, or a start / run capacitor, or two capacitors, the failing of one may mean that the compressor will blow a fuse or circuit breaker when attempting to start.

The correction of the problem of when the air compressor trips the breaker on restart becomes increasing complex once these earlier tests have been made. One of the more complex tests is that of testing the capacitors.

Please see the pages on this site that describe what the capacitors are – if you don’t know – and those about how to test them.

Compressor motor windings shorting? In our opinion the next component that will be suspect when the compressor trips the breaker on restart are the motor windings shorting, or any of the electrical connections inside the motor that may be shorting and the sudden flow of electricity to ground pulls too many amps.

If you have reached this state in your compressor problem diagnosis, and you are not skilled in electrical motors or electrical circuitry, we suggest that you get your compressor motor to an electrical motor shop for a load test to try and determine what, if any, part of the motor is shorting.

These are a few of the typical reasons why an air compressor trips the breaker on restart. If you have experience with other scenarios, why not share them with visitors using the comment box below? If you see a comment and you would like to add to it, please feel free.

It is always helpful if you identify the make and model of your air compressor in any post.

 

Comments

  1. Charles Linn says:

    I have my Dad’s old Champion compressor, a two-cylinder, The sticker on the motor is too faded to read but I am guessing it is 3/4 hp to 1 hp. I have it on a 20 amp breaker and a 5′ 12/3 cord.

    It initially starts fine and goes up to 100 lbs when where I have it set to cut out. I can hear pressure being bled off the cylinders by the unloader valve after the compressor shuts off so that seems ok. But, when it is time to restart, the motor runs about 10 seconds and before it really gets up to speed the breaker kicks out.

    When the breaker kicks, the compressor pulley seems fairly easy to turn by hand–I don’t know what to expect but doesn’t make sense (to me) that the motor is too weak to turn it.

    So I started by replacing the check valve–which was completely shot and definitely needed it. No change. Next I did the pressure switch, which came with a new unloader valve. No change. Then I replaced the start and run capacitors. No change. New belts and they aren’t slipping.

    If I bleed off the pressure to about 30 lbs by turning the compressor off and running a tool for awhile, it will start up and fill the tank as it should. Seems like it could the unloader valve is not letting off all the pressure, but what are the chances of both the old and new unloader valve being bad?

    Any ideas would be appreciated. I hope it isn’t the motor!

    • Zeroing in on the capacitors was a good idea, as that would be my first thought based on your compressor symptoms. Your power supply looks good based on your description. Replacing the check valve was a good move. If I understand correctly, the compressor pump starts fine with the tank empty, but will not properly restart if there is air in the tank? Things that may be causing this are a faulty valve in the pump (don’t know where for sure, but maybe from the second cylinder to the tank if it’s a two stage or one of the cylinders if it’s just a twin) or the motor itself has an issue with the power on start up against load.

      • Charles Linn says:

        HI Willy
        Thanks for your reply.

        Yes, if I start with an empty tank the pressure will build up to 100 psi no sweat. But, when it is time to restart, the motor will run for about ten seconds and trip the breaker.

        If I just bleed off air pressure down to 30 pounds it will restart, but if I only bleed it down to 40 pounds when I flip the switch on it will kick off the breaker again.

        It isn’t a two-stage, just an ordinary twin. This is an old horizontal tank type on wheels.

        But I am afraid I don’t know what you mean by a faulty valve–could you explain how that would work? It does seem like if the check valve is working OK, and the unloader valve is OK there shouldn’t be any extra pressure that the motor is working against. But that motor just doesn’t quite get enough momentum to keep going.

        It would be too bad if it is something in the compressor–I doubt there are any parts for this thing–it is pretty old.

        I do have an another motor I think might fit that I could throw on there and see what happens. It is a 3/4 hp 3450 rpm, though I think the one that is on there now is a 1140 or 1725–it runs pretty slow.

        Any thoughts? Thanks again!

        • Could be the motor… which is easier for you. Swapping the motor or opening the pump head to have a look at the valves. It’s the valves inside the pump to which I referred earlier, Charles.

          • Charles Linn says:

            HI Willy–my question about the valves would be, what would I look for? Don’t these cylinders have something like a head gasket that has to be replaced once you open it up? As I mentioned, I doubt there will be any parts for this.

            I believe it would be better to try the motor–at least at this point the compressor will pump up!

          • I’ve not taken this model pump apart Charles, so my response is general. Yes, there will likely be a gasket inside the pump that will need changing. As far as the valves go, you would be looking for anything that looks wonky… broken part, sticking reed etc. I cannot be specific as I haven’t looked inside one. Yup, get the motor checked out first.

  2. I am sure its one of the two capacitors, please tell me where I can order them from?
    model number BTM56RB34D2M

    • As noted on this site: “You are here: Home / Is The Compressor Start Capacitor Working?
      Is The Compressor Start Capacitor Working?

      This is page three about troubleshooting a Craftsman air compressor that will not start and this page focuses on – is the compressor start capacitor working?

      If you want to review the steps from the beginning, here is page one on figuring out why your Craftsman air compressor will not start.
      What in heck is a start capacitor?

      It’s a device (or sometimes two) normally found on the exterior of a compressor motor, often covered in a metal shroud, near the shaft end of the motor. The purpose of the start capacitor is to help the compressor get going. If your compressor motor also has a run capacitor, that one helps to keep the motor running.

      Start capacitor cover installed on electric motorThe start capacitor cover on your compressor motor may look the same as the one shown in the photo, or might differ slightly.

      As we have been trying to find out why our Craftsman air compressor will not start, in previous pages we’ve traced the power supply successfully to the motor circuit.

      If the compressor motor start capacitor has failed, the power supply to the motor stops there, and the motor will not start.

      If you are comfortable with doing so, remove the cover of the start capacitor. Your capacitor may look something like the one in the next photo.

      compressor motor start capacitorWhen you get the cover off, examine the capacitor. We are expecting that you have pulled the compressor power cord at this point. Please be careful not to touch the capacitor terminals as a capacitor is a high discharge device, and you could get quite a jolt from the power that’s stored in it.

      Look for discoloring, blisters on the outside of the capacitor body, connected terminals that don’t have a lot of corrosion on them, anything that would give you the impression that all is not right with the capacitor.

      Even if the motor capacitor looks good, you will still want to check it to make sure that it’s working properly. Please see the embedded video about “How to Check Motor Start and Motor Run Capacitors”

      Replacement compressor motor capacitor

      You will, unless the label is worn off, be able to see writing on the side of the capacitor. It will show a rating in MFD (mircro-farads) and a voltage range.

      As long as you acquire a replacement motor capacitor that has the same MFD rating as the old, and the same voltage range, and you can connect the terminals, then you can use that capacitor, regardless of the shape or size. It’s best to get one that fits inside the existing capacitor cover, of course.

      If you cannot see the writing on the side of the capacitor, then it’s time to check out the motor specs to find what capacitor is needed, and you can use your search browser to query what the capacitor is for such and such a motor HP, with xxx voltage etc.”

  3. I have a 5hp Devilbiss ProAir Model PRF5530, 30 gal tank. The compressor has worked fine for about 17 years with no problems. A couple of weeks ago it started throwing the breaker after running for about 3 seconds. I read your articles. Since it starts fine, I replaced the run capacitor and installed a rebuild kit for the cylinder while I was working on it. It still does the same thing. There is no pressure in the tank, no sparks at the rear when it is starting, everything is drained so it isn’t the release valve. The only thing I haven’t replaced is the start capacitor. Since it starts up fine, I didn’t think it was the problem. Any ideas? Thanks,.

    • Also, I ran another test after posting the above question. I loosened the top air line that connects to the head cylinder on top and moved the air line out of the way. I then attempted to crank it. I felt the air coming out but after 3 seconds it threw the breaker. I reset the breaker and placed my thumb over the head port and tried to crank it. It threw the breaker immediately. I’m guessing that is due to the back pressure my thumb caused.

    • “throwing the breaker after running for about 3 seconds.” this suggests the start cap is the issue. Check it out, will you, and let us know?

      • OK. I’ll order a new capacitor and install it and see if that fixes it. By the way, your video shows the start cap on the outside of the motor. Another site I was looking at said that the start cap was the one inside the rear cover. I replaced the one on the top of the motor. I thought that was the run cap. I’ll get a new one to replace the one in the rear of the motor and let you know what happens. Thanks.

        • Different compressor motors have different capacitor locations. Some fractional HP motors may even have the cap as part of a circuit board.

      • Robert Myers says:

        Finally got the start cap. I was only able to find ONE contractor that could get the start cap from A.O. Smith. No one else had it. I contacted at least 8 different supply houses. Finally found CSH Electric on-line. It cost about $33 which was a lot higher than the other caps I found. The running cap was only $9. Anyway, I put it in last night and it didn’t help at all. Everything else that I plug into that outlet works fine so I know it isn’t the outlet or the wiring to the breaker box. I’m really out of ideas. I’ll probably see if I can find a small-motor repair shop around town and see if they can track the problem down. Thanks.

  4. I have a Ingersoll rand 200 liter single phas. AAttached to a socket in the wall. Used it for good couple of jobs, now it just cuts power after a few seconds of starting and trips the breaker in the house. I use it for sandblasting. Is it possible that maybe the aluminum oxide has some how gotten into the movements?

    When the motor runs in the starts for few seconds its fine, then it starts to slow down and trips

    • Bill, see the troubleshooting page on this site about testing your motor capacitors, and please do so. The compressor symptoms suggest to me that this might be the problem.

  5. Garland Heart says:

    My Rigid electric wheel borrow type compressor circuit breaker trip’s around 60psi, any idea what the problem could be ?

    • Whether or not it’s an electric compressor on a wheelbarrow or not, has no bearing on the circuit breaker tripping, I expect. Are you saying that the circuit breaker in the supply panel trips, and not the breaker on the compressor? If it’s the former, I’d wonder if your extension cord is under sized for the distance from the source to the compressor?

  6. Hi, my craftsman air compressor has worked fine for years and now it blows the fuse as soon as it starts to run. It’s a single cylinder oil free 5 hp max 1.7 hp running 30 gal compressor. 120V 15 Amp. It’s plugged into a receptacle in my garage. I have unplugged it and my fuse is fine so I know it’s the compressor. Where would I find the capacitor(s) and how do I test them? I love to tear stuff apart but I can’t afford to guess with this. I use it all of the time. Need it back up and running asap. Doesn’t matter if tank empty or full, it’s currently empty. Should I look at the motor part itself of first should I look where the electrical cord goes into the box. Model 919.165570

    • Boz, all the info you have asked for is already available on the pages of this site. No point in retyping it all here. Have a look, and if you have a specific question – other than those that are already answered, please add a comment here.

      • Capacitors tested fine. I was told by a technician that most likely the bearings are bad causing the inside to touch the windings grounding it out. Electric motors are far from cheap! Holy crap batman!!!! For the price of that I might as well spend a couple bucks more and get a whole new compressor and keep this old tank for storage.

  7. I have 25 gallon husky belt drive air compressor not sure old it is as it was given to me by a friend. It’s been plugged into an outlet with a 15 ft extension cord that runs my garage door and lights for 10 years which is a 15 amp breaker last weekend when tried to start back up it tripped the breaker so I took the belt to be sure it’s not the compressor itself and it still trips took the back cover off the motor and tried cleaning the contact in side still trips I’m at a loss. the motor does have two capacitors. Any suggestions?

    • See the page on this site about testing the start capacitor. That would be our first step… that, and losing the extension cord completely. Your power supply is marginal even when not being compromised by an extension cord. Move the compressor to the socket and plug it directly into the outlet. Use a longer air line to get air to your tools.

  8. I have a HuskyPro 26 Gal oil lube compressor, when the compressor starts to re-fill I hear the pump cycle about 3-4 times, then it will stall and trip the breaker. I have already replaced the unloader, but that didn’t help. I’m not using any extension cords, and when it is very low pressure, the motor will fire up (but struggle) but then continue to fill up the tank to 145psi or so. the motor already has been reconditioned once (I’m assuming, as the word recon is scratched into the larger of the 2 capacitor bulges on the motor)

    • If you are sure that the unloader valve is working, and you have not added any load to the power circuit that is feeding the compressor, our recommendation would be to check the start cap.

      • So, I’ve replaced the unloader, and both the start and run caps… sadly, it’ still stalling on refilling the tank. It will fill the tank from empty just fine, just refilling the tank is where it stalls out. when I let it fill all the way up without stopping it, I can hear the unloader release the pressure, I don’t think it does when I turn it off before it hits it’s full pressure. (I’ve never had an issue with it doing it this way in the past)

        • Is it fair to say that the compressor works well until there is back pressure from the tank? You’ve checked most of the necessary things to check, yet we wonder if the problem is caused by a wonky tank check valve that prevent free flow of air into the tank, thus overloading the motor circuit? We would remove, clean and / or replace the tank check valve next. If that doesn’t resolve the issue, then it’s pretty much got to be a high pressure valve that’s blocking flow into the tank line as back pressure grows, or it’s the compressor motor itself that has a problem.

  9. RICARDO says:

    I have a dewalt 30hp compressor it fills up fine then when I start to use it and it starts refilling the breaker power pops out and it’s not allowing me to use it again cause the air won’t fill back up please help

  10. i have a Mcquay unit and the compressor is very hot, i tried restarting it by flipping the breaker off for two hours per instructions from my super, when i re started it, it was on for about a few seconds and tripped the breaker again.

    • Please tell us about the power supply to the compressor. Extension cord? Amperage of breaker for the compressor circuit. What else is drawing power from the same circuit and so on. If your power supply is starving the motor, overheating and thermal cutout almost always results. If, however, the power supply is good, and the compressor problem is a new one, that suggests that your motor power supply is compromised, and typically that’s a start capacitor problem.

  11. Compressor pumps up to max air when pressure drops it will not come back on until empty was told 3 phase wasn’t big enough.

    • Well Ron, a bit hard to be specific as we have no idea of the make or model of your air compressor. The troubleshooting pages about air compressors that won’t come back on themselves will be helpful to you we think, and more specifically, can you tell us if the unloader valve works when the compressor reaches cut out?

  12. My compressor keeps tripping the breaker at cut in. Starts fine after I completely empty the tank. I changed the pressure switch, the unloader valve and the check valve. Still trips breaker. Any other ideas? Again starts fine with an empty tank.

    • Welcome back, Simon. That the compressor starts fine with the tank empty is pointing to a load issue. You replaced the unloader valve, and you confirmed that it is working, which is a good check to make. As long as the power supply is good, and pump pulley turns easily (indicating that there is no mechanical lock up), then it comes down to only a couple of things. One is that you’ve got a valve in the pump that’s locking up under back pressure, or the motor start capacitor isn’t sufficient for the job, or the motor itself is failing.

  13. I have a 4 hp compressor that starts fine when pressure is low but once it has full pressure and it tries to restart it sounds like it is running fast enough but then blows a 20 amp breaker. It seems to make a vibrating noise on and off, then blows. I already changed the starter compacitor, not the run one.

    • Not knowing the make or model makes diagnosis a bit more difficult, Kevin. If the compressor starts and runs up to cut out when the tank is empty, and only has problems restarting when the tank has air pressure at the cut in level, we wonder if you have checked to ensure that the unloader valve is actually unloading? Not sure what that is? It’s covered on a page on this site.

  14. I have a 120v 6.3amp 1/2hp compressor with a sf of 1.25. I have a 15amp breaker with a 12/2 ran to the motor starter which is operated by the pressure switch on the compressor. The starter has a relay with and overload set at 8.6amps, with a range of up to 20.2amps. The operating pressure is 60psi and when the compressor drains to be refilled it trips upon start-up. What is happening? Do I need a higher amperage breaker? Change the overload amperage? Compressor screwed?

    • willyr says:

      Well, it may not be totally screwed! 🙂 What we think you may have a problem with is the starting capacitor, or the start run capacitor if it only has one. See the page on how to check the caps on this site, and let us know if that was the problem if you would.

  15. TIM NESSLER says:

    I have a 220v air compressor that has been out of service for over ten years. The electric motor was bad so I replaced it with a new one. It will start off and build to under 20psi and trip the circuit breaker. I can slowly build the air pressure to 80 psi after about a half dozen trips of the circuit breaker. If the discharge tube is disconnected from the compressor, it will run fine under no load and not heat up the compressor or the electric motor. Once I start loading the electric motor the circuit breaker trips. It has a Telemechanique XMP pressure regulator with an unloader valve. The compressor does put out a lot of head pressure, so and ideas what I should check next? It ran fine before I took it out of service and never had any problems. It has been and will be stored in a garage.
    Thank you.
    Tim

    • Tim, we are assuming that you’ve drained the sump and added the correct amount of fresh oil? The air intake filter is clean? The tank check valve has been removed an tested? That being the case additional causes could be a motor capacitor failing, the valves inside the pump are failing, or a possible mechanical issue with the pump itself. You can see the page on this site about testing the capacitor, and that’s what we would do next.

  16. Stefano says:

    I wonder if someone can suggest me about a problem i having with my 2hp induction motor air compressor. Last week the compressor shotted down the 15 amps circuit breaker, I turned on the circuit breaker then the compressor did run for few minutes then the circuit breaker shotted down again. Since the compressor can run on 20 amps circuit I connected the compressor to 20 amps circuit and then when the compressor did reach 80 psi shotted down, this time by the protection on the motor itself (the red button on the back of the motor) . I called the compressor company and they told me that it was a problem with the motor and they sent me the motor that i installed today but I have the same problem. The pump turn freely by hand so I, don’t think is a pump problem, the compressor turn of to 80 psi all time but it isn’t a problem from the regulator because any time the compressor stop still has the electric power coming from the regulator (I call ”regulator” the device that stop the compressor when the compressor reach the max. pressure )
    Thank you
    Stefano

    • Please tell us about the new motor, Stefano. Did it come with a start and run capacitor? Or, are you using the older ones. We think that it could be an issue with the run capacitor on this motor. Please see the page on this site about how to check them.

  17. My new compressor was tripping the breaker on kick-in pressure. My garage only has 2 outlets making an extension cord necessary until I re-wire (although the book says avoid extension cords). My New Porter Cable belt driven compressor filled from 0-135 (kick off pressure). I read this tip page and after going to the hardware store and purchasing a new 25′ 10 gauge contractor extension cord (the big thick ones) everything worked perfectly. Thank you so much for this web page! Hope this helps anyone else who has this issue.

Speak Your Mind

*

Fix My Compressor Privacy Policy   |  
cookieassistant.com