Compressor issue

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Forum topic by MedicKen posted 02-03-2009 08:51 PM 846 views 0 times favorited 8 replies Add to Favorites Watch
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1603 posts in 2245 days

02-03-2009 08:51 PM

I have a craftsman 33 gal, oil less, vertical compressor that I am having an issue with. I recently rewired the garage and added numerous outlets, both 110v and 220v, all 20amp, all the wiring is new and sized accordingly. When my compressor turns on it trips the breaker. It is rated at 15 amps and is plugged into a 20amp dedicated circuit. My first thought was I had a bad breaker, so I replaced the breaker. It didnt help the problem. So my question is, even though it is rated at 15 amps, does the initial amp draw exceed 20amps? Or, is there an electrical problem with the compressor? I havent tried running the compressor on a different circuit, thats my next step.

-- My job is to give my kids things to discuss with their

8 replies so far

View marcb's profile


762 posts in 2456 days

#1 posted 02-03-2009 09:00 PM

Sounds to me like the valve that allows a little air out during compression is stuck shut. I had that issue.

Its the valve that has a little hose that runs to the pressure switch. Compression pushes it open and allows a little air to escape so that the motor isn’t fighting pressure.

That’s what it was when my compressor did the same thing at least. Poped it out of the tank, took it apart and cleaned it up, poped it back in no issues.

View daveysprocket's profile


40 posts in 2190 days

#2 posted 02-03-2009 09:12 PM

I had the same issue and it turned out that the air valve that dumps pressure between the pump and the tank was not working. If I manually let all of the air out of the tank, it would work fine, but wouldn’t restart after that without tripping a breaker. You should hear a Psshh once pressure is reached and the motor shuts off. If not, there is still pressure in the manifold that the motor cannot compete against. I think you can get new valves at Tractor Supply. Also, run it off the heaviest rated ampereage you have available. I switched mine to 20A and it worked better, then I switched it to 220v and Wow.

View MedicKen's profile


1603 posts in 2245 days

#3 posted 02-03-2009 09:20 PM

It is currently being run on a 20 amp breaker. The pressure relief is working, at least when it shuts off I can hear the valve release the pressure. My compressor is not wired, nor capable, of being rewired to 220. I will take it apart and see if there is something stuck or broken in the pressure relief side. I should have known better than to buy craftsman.

-- My job is to give my kids things to discuss with their

View ajosephg's profile


1862 posts in 2344 days

#4 posted 02-03-2009 09:38 PM

Sounds like it’s time to take the belt off and see if you can turn the compressor over by hand. If not, the problem’s in the compressor, if so, it’s in the motor I’d think.

-- Joe

View Karson's profile


34925 posts in 3183 days

#5 posted 02-03-2009 09:57 PM

I assume that it pumps up fine when the tank is empty. It’s when it recycles that you are having the problem.

I understand that you hear the releaf valve open after shutting off, but it does sound like that kind of problem.

-- I've been blessed with a father who liked to tinker in wood, and a wife who lets me tinker in wood. Southern Delaware †

View bendisplays's profile


39 posts in 2183 days

#6 posted 02-04-2009 07:27 AM


Motors draw more when they are starting but I do not beleive that is the problem,

Now as some one stated the “off loader” valve may not be opening. It keeps the compressor from starting against pressure. This will definately cause the circuit breaker to blow.

I would also make sure that you do not have an long extension cord. The cord will cause a votage drop and the motor will slip and blow the breaker.

I would check the valve first and if you have a long extension cord that may also be the problem.



View MedicKen's profile


1603 posts in 2245 days

#7 posted 02-04-2009 08:33 AM

Ben…..The compressor is plugged directly into the wall outlet, no extension cord. I cant believe that it would draw more than 5 amps over the rating and trip the breaker. It seems that all of the valves are operating correctly. Guess I will start checking electrical connections, maybe the chinese forgot to tighen something?

-- My job is to give my kids things to discuss with their

View bendisplays's profile


39 posts in 2183 days

#8 posted 02-05-2009 08:12 PM


Okay that sounds good. If the off loader valve is good and your compressor is next to the outlet, I would suggest some heavy duty breakers.

I own a commercial shop and most of my machinery is 3 phase. The way this type of equipment is protected is through a thermal overload on the motor starter. This is just a device that wont trip on an initial starting of the motor “It will not trip on a initial spike”.

Some motors start hard and there are some heavy duty breakers that are available for motor applications such as yours (single phase). The availability is going to depend on the brand of your breaker panel but there are several ways that you could actually handle this.

If there is not a heavy duty breaker available, you could increase the capacity of the circuit and put in a larger breaker (This is if you have the proper ampacity wire). You can actually get a thermal overload circuit for your compressor and it could be installed in a box next to your compressor. Your compressor is going to likely have a thermal overload with a push button reset so if this is the case you will not need to get a new circuit.

I hope I am not adding a lot of effort and expense and causing another problem with the solution but it does sound like your compressor is starting hard and it is tripping the current breaker. If possible, you want to either get a more heavy duty breaker for motors (which is not availble on all brands of breakers) or up the breaker to 30 amps. If you get a larger breaker, then the ampacity of the wire to the outlet will have to be that which is code for 30 amps (this may already be the case). Also if you get a larger breaker, then you will need to have a thermal overload to protect the motor and the wiring of your house.

Also check your local code to see what the requirements are in your area.

Remember that most likely the motor is starting hard and it is “popping the breaker”. After a motor starts, the current draw goes down considerably.

I hope that this helps. If you have any questions please ask. I am an electrical engineer but not a electrician so I know what works but I am not up on residential code. Always check code in your area before you proceed.



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