craftsman 5hp 20gallon compressor trips my breaker at start-up

craftsman 5hp 20gallon compressor trys to start up but trips my 15amp breaker. it will run a second or two before doing it. unloader valve seems to be working, it moves in and out while trying to start, turning the regulator to o or max makes no difference, check valve works in and out, motor fan turns the piston without any snags, what could be the problem?


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Bill says...

Is this a new condition? What has changed in the power supply? My first check would be to see what else is pulling power from the same supply circuit.

When you say that it runs for a second or two, does it actually pump air, or is the motor trying to start for a second or two, and then the breaker pops? If this is the case, then I would consider your capacitor suspect. It may not be supplying enough boost power to get your motor going, the motor pulls too many amps for the circuit without the capacitor boost, and the breaker pops.

If neither of these are the cause send me a note as a comment on this thread telling me what you have done, and I'll respond further.

If you haven't looked at the page about BLOWS BREAKER OR FUSES from the troubleshooting page, I'd suggest that's a good read.

Cheers,

Bill

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Craftsman compressor Blows breaker

by Steve
(Massapequa PK N.Y.)

Craftsman 33 gal 6hp motor compressor, when turned on runs for 3-5 sec. then blows breaker. Motor turns free and I seperated motor from pump and still blows breaker when turned on. Some one told me maybe because the piston wore out and the motor is freewheeling or free spinning and the amprage is going up to high?

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Bill says...

Hi Steve:

Ummmm... it doesn't make sense to me that a motor with no load will draw too much amperage. Just the opposite I would think.

That it starts and runs for 3-5 seconds suggests it's a motor problem, and not the capacitor starter which can be a culprit when motors blow breakers.

And that you are still blowing the breaker with no load on the motor suggests that the motor is somehow generating a short, this pulls too many amps, and the breaker pops.

If it were me, I'd pull the motor and take it to an electric motor rebuild shop for a test.

Cheers,

Bill

Comments for Craftsman compressor Blows breaker

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Nov 15, 2010
just a thought
by: Anonymous

you may wish to check the circuit breacker. they also get week.

Nov 01, 2010
919.165500(craftsman 33gal 6hp) exact same problem
by: Dave

Please post a follow up as this motor is nearly $300. I'd like to get this thing running myself without spending anywhere near that. I have narrowed it down to the motor and want to know if you or anyone else has solved and fixed this problem, also how much time and money was spent doing so.

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craftsman model # 921.152150 blows the fuse on restart

by zane
(medford oregon usa)

craftsman 125 psi 3/4 hp 4 gallon pancake compressor model # 921.152150

compressor builds pressure shuts off when the pressure drops and it kicks back on it blows the fuse
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Hi Zane...

It's typically a few of things.

One - your unloader valve is not working, and that's causing a motor overload on startup

Two - you are using a too small extension cord and there isn't enough power for motor inrush on start up

Three - other appliances on the same circuit are pulling power at the same time your compressor is trying to start (see two)

Four - your motor start capacitor is failing

Could be other things too. See the troubleshooting section on the sitemap page for links.

I'd guess number one and I would check that first.

Bill

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5KCR48TR2GS motor just hums and does not turn

by Michael Samson
(Los Angeles CA)

Motor pumps air with the valve open and no load on the compressor (just pumping air out the valve)

When an airline is attached the motor just humms and does not turn.

Brushes? or switches?
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An open air line from the pump means no load. No load means that the motor is easier to start.

Reattaching the line adds load.

First thought... attach the line and empty the tank. If the compressor starts, let it run up to cut out and make note to ensure that the UNLOADER VALVE works.

If it does, then I'm thinking your start capacitor is weak or has failed.

Cheers,

Bill

Comments for 5KCR48TR2GS motor just hums and does not turn

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May 14, 2012
capacitors
by: greg

i have a craftsman air compressor with the same motor model no. 5KCR48TR2GS, i need both capacitors for the motor but can not find the part number and do not have the size capacitors need, if you have them and could help me out i would greatly appreciate it. thank you.

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