motor just hums and then blows fuse

by jim
(herrin il.)

This is a sears vertical 33 gal recipacating compressor. The motor and pump turn free by hand. No bad bushing or bearings.


___________________
Bill says...

Three things come to mind immediately, Jim.

One, make sure you are not using an extension cord, or if you must, it is an industrial, large gauge cord. Two, your unloader valve is not working. To test, unplug the compressor, open tank drain to void tank, close drain, plug in and start. Does it? If so, your unloader valve may have failed, and the motor cannot overcome the additional load. Check out UNLOADER VALVE from the site map for details.

Three, your start capacitor may have failed. One day I'll have a page here to explain how to test one, once I get an electrician buddy to tell me how. If you don't know how, take the compressor to an electric motor shop to have the capacitor and motor tested.

Cheers,

Bill


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sears 30 gallon 2 hp compressor - Blowing breaker

by Jeff
(Louisville,KY.)

I've got a sears 30 gallon 2 hp compressor, approx 2 years old. When it comes on it blows the breaker about 50% of the time. Even when it only has a few pounds in it. I changed 20 amp breaks with no change. It is a 15 amp GE commercial motor. model #5KCR49TN2450AX Ser #UYFP29. Whats my solution??

______________________
Bill says...

Jeff, good question! :-)

For sure you've got either a too great amp draw or a fault to ground.

That it doesn't happen every time is interesting.

Do you have any other electrical appliance in the circuit that might cycle on when the compressor is starting? If there isn't enough current to go around, that might be an issue.

You say, "When it comes on it blows the breaker about 50% of the time." Does this mean that it starts and runs for a while then pops the breaker, or does it mean that it pops the breaker while it's trying to start?

If the latter, I think it could be a failing pressure switch.

Post bit more info to this thread, and we'll continue trying to figure it out with you.

Cheers,

Bill

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sears 921.153102 3 gallon 1 hp - overload reset switch?

does this unit have overload reset switch

_________________________
Bill says...

If there isn't one visible around the on / off or panel, then there may be one on the motor, but I do not know for sure.

I have examined the manual for the model 153100 ( I don't have the manual for your model ) and it does not specifically refer to a motor reset or motor thermal reset, so I would need to see the motor to see if there was one.

Cheers,

Bill



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Sears Compressors ~ breaker trips after about 2 seconds

by Tim
(Ashburn, VA)

Compressor is a Sears 25 gal 5 HP portable (electric). Had been working fine, but after using for about an hour the other day, the compressor kicked in automatically to fill the tank, and blew the breaker.

Compresssor runs slowly for a few seconds, then trips the breaker. With no pressure in the tank, it runs a second or two longer but still trips the breaker. I have tried several different outlets with the same result, including a dedicatd 25 amp circuit, so it's not that. I have also tried turning the pump by hand it it rotates freely. Compressor is about 10 years old.






Bill answers...

Check your unloader valve. I think that it has failed, and as a result, the motor can't overcome the additional load on start up.

Not sure what that is? Go to the sitemap page, and look up Unloader Valve for more info.

Cheers,

Bill

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compressor will not start.. Is there a reset button...


(chapel hill, nc)

My compressor is a sears 6hp-2hp, 30 gal., 8.6scfm @ 40 psi, 6.4 scfm @ 90psi, 120 V/15 amp, single cylender/oil free unit.

Compressor will not start.. Is there a reset button somewhere inside the housing???

____________________
Bill says...

Usually if there is a motor thermal overload or reseit button, it is readily available from the outside of the housing. Doesn't make much sense that it would be hidden.

What is, or is not happening when you turn it on / plug it in?

Cheers,

Bill

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Sears air compressor problem - just putt putts for 10 seconds and the blows the breaker

by john y
(fairport,ny)

The motor does not appear to be shorted--I am an electrician and have tested the winding and capcitors.

The compressor appears to free wheel nicely--strange--when it was running right it would start off loudly with a lot of torque--now it just putt putts for 10 seconds and the blows the breaker.
____________

Hi Johny:

If the compressor is blowing the breaker, then as an electrician, you know that it's either a short of some kind, or the electrical motor is pulling more amps than the circuit can handle.

If you are sure that it's not a short, and the motor actually starts (it's not the capacitor), and the motor shaft turns easily (meaning that the power train into the compressor head is not binding in some way and overloading the motor) then it's got to be the motor that's at fault.

Bill

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Sears Compressor kicks breaker after a few seconds

5 up 25 gallon sears

______________________
Bill says...

Not a lot of info to go on here.

Try this. Unplug the compressor, drain the tank all the way down to no PSI on the gauge, close the tank drain, and plug it back in / start the compressor.

Does it start?

If so, let me know by posting a comment here so I can follow the thread.

Cheers,

Bill



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Breaker pops on Sears 6 hp. / 33 hp. / 150 p.s.i. air compressor

by Michael
(Floral City, Florida)

When I try to use my compressor, it will run for about two seconds the trip the electrical breaker that it is plugged into. I have tried four different circuits with the same results. What can I do to remedy this problem?






Bill answers...

Hey Michael, real nice to hear from Florida.

That you have tried four different electrical supply circuits with the same results clearly indicates a problem with your compressor and not the supply circuit.

The breaker trips because the compressor circuit is drawing more amperage than the circuit can provide, and that's caused by a fault of some sort in the compressor itself.

I think we can assume that there's not a short in the power supply to the compressor (power cord) as if there were, the breaker would pop instantly.

The compressor turns on when you plug it in because the pressure in the tank is below the pressure switch cut-in pressure setting.

Since the compressor pressure switch reacts to system pressure, in your case it's already switched and "calling" for power to flow to the electric motor when you plug the compressor in, since you indicate that the compressor starts and runs for two seconds before popping the breaker.

Now, does the motor actually start, or does it just try to start? I ask this because if your unloader valve hasn't "dumped" the air over the piston when the compressor last stopped, that trapped air might overload the motor to the point that the breaker pops.
It seems to me that your pressure switch is OK, since if there were a short in it, the breaker would pop immediately you plugged in the power cord, not wait 2 seconds.

That your compressor starts and runs for two seconds suggests that your motor capacitor is OK, else the motor wouldn't start at all.

I think you've got a motor problem.

Though it could be the motor itself that's failing, drawing too much power as it tries to start and overcome whatever is ailing it, it could also be that there's a mechanical issue with the compressor power train, and that mechanical issue is overloading the motor shaft, creating additional load on the motor and starting circuit, and forcing the motor to draw too much amperage which pops the breaker.

So, if the compressor unloaded the last time it ran (it goes psssshhhttt for a second or so to let the air out over the piston when it stops), and if the motor actually starts and runs for 2 seconds, and assuming this is a new condition and the compressor ran with these electrical supplies before (the motor amperage normally doesn't exceed the circuit) then your problem is likely from the motor to the actual compressor pump, somewhere in there.

Hope this helps.

Cheers,

Bill

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sears compressor blows breaker after prolonged use

by patrick
(ohio)

I recently bought a blast cabinet and my compressor blows the 120V breaker. every time i use it the breaker blows in a shorter amount of time than it did before. my compressor has always worked fine prior to this and has always run off of the same outlet. the blast cabinet requires 5.0 CFM and my sears compressor (4hp 15gal.) claims 6.9SCFM at 90psi. Before i bought the blast cabinet i was able to run it as long as i wanted.






Bill answers...

Hello Patrick from Ohio. Very nice to hear from you.

From what you've told me, I think you're running into a little issue with your compressor's duty cycle.

Here's info on the compressor duty cycle.

I suspect either you are overheating your compressor to the point where it starts to seize (thus drawing more amps and popping the breaker) or you've already damaged the motor and it's cycle gets shorter and shorter before it's overheated to the point of seizing.

Makes me wonder, though, why it doesn't shut off on thermal overload.

Regardless, I think you've got a compressor motor problem.

Cheers,

Bill

Comments for sears compressor blows breaker after prolonged use

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Feb 02, 2016
Oil less craftsman compressor
by: Anonymous

mine kicks out almost every time it runs. if I reset the breaker it continues to run until tank is pressurized and then it kicks off normal. ...

(Please start a new thread so we can address this compressor problem directly. Thanks)

Dec 31, 2013
Air compressor tripping breaker
by: Raymond

I have a30 gal, 6 hp upright craftsman air compressor tripping breakers within 3 - 6 seconds. I have replaced the starter capacitor with no change. I tested the run capacitor and it tested good. Then I took the start switch completely apart and cleaned the contacts and still no change. The tank is completely empty so the pressure switch is not the problem. When I try running the compressor sometimes it acts like it wants to start but again trips the breaker. I have a dedicated line for the compressor, nothing else is on this circuit.
Any ideas what I may be missing, what about the pressure overload switch mounted on the rear of the motor?
Thanks, Raymond

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