Sears air compressor throws breaker

I have come in possession of a Craftsman model 919.165200, 5 hp, 20 gallon air compressor that when turned on runs for a few seconds then throws a breaker in my shop. Anyone have a clue as to why or how to repair? Anyone come across this problem before?

TIA

Jerry

Reply to
Jerry8770
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What size breaker in on that line? 5h/p is a large motor.>

Reply to
Andy & Carol

I was given an old Craftsman AC a few years ago that gave me problems. Upon inspection I discovered the ground and neutral wires had been reversed. Fixing this stopped the GFI from tripping but it tstill tripped the breaker till I ran a 20 amp circuit.

Reply to
tom

Reply to
Robert Barr

How cold is your shop? Does the compressor have 30W oil or 20W? (default is 30W, which may be too thick in the winter)

Bob

Reply to
zxcvbob

What size breaker is that on? A real 5HP motor will probably need a #10 circuit and probably would like a 40A breaker.

Chris

Reply to
Chris Friesen

possession of a Craftsman model 919.165200, 5 hp, 20

Reply to
Jerry8770

Things that will cause the breaker to trip:

  1. using an extension cord with the compressor.
  2. other units running when the compressor kicks in.
  3. bad or under rated circuit breaker. (need 15-20A)
  4. a bad pressure switch on the compressor.
  5. a bad capacitor on the compressor motor.
  6. a bad motor on the compressor.

Bob

Reply to
Bob S.

  1. a bad unloader valve (maybe that's what you meant by the pressure switch)

Bob (no relation)

Reply to
zxcvbob

To many variables. What is the nameplate voltage and running amperage(fla)? Is the motor connected for 120 or 240 volts? Is the 20 amp circuit you're connecting it to, a dedicated circuit? Do you know that it is or was in working condition? Is the tank empty or is there compressed air in it?

Reply to
RBM

If all else is up to par, that would be my guess as well

Reply to
RBM

A compressor that size needs the motor set for 220 volts and 220 volt service plumbed to it to drive it. Even if it has a 120 volt setting, its foolish to run a motor that big on it. My craftsman in my garage is

220 volt. I had to run a special line out there to do it. I just stole the unused dryer AC feed and rewired it.

Bob

Reply to
BOB Urz

compressor oil low? That will put a tremendous load on the motor.

Reply to
Eric in North TX

Old breaker? Cycled too often? I would check if a true overload was happening.

Get an electrician, is shouldn't be expensive.

tom @

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Reply to
LayPerson Tom

Yup. If the extension cord is too long the voltage drop will trip the breaker.

Reply to
PaPaPeng

A single phase 5 HP motor at 115VAC draws 56 Amps. A single phase 5 HP motor at 230VAC draws 28 Amps. A five horsepower compressor is huge. Most garage 110VAC circuits are 20 amps at best. 230VAC circuits are usually 30.

Reply to
Eric9822

You're all forgetting the funny way they rate horsepower on compressor motors. A "5 HP" motor might really be 2 HP or less.

My current 6 HP compressor runs on a 20A 240V breaker, and it doesn't put out as much air as the ancient 1.5 HP compressor that it replaced when the old one finally bit the dust.

Best regards, Bob

Reply to
zxcvbob

I've got a THREE QUARTER horse motor that is probably 45 years old, runs fine on a 15 a circuit, and is probably 2 1/2 times the diameter of these so called modern 5 horse motors. It runs my compressor all day continuously and will still be cool to the touch. (In cool weather that is, it's outside) They've really fouled up the electric motor horsepower ratings. I'd like to see one of these yuppifed motors on a motor dyno.

Reply to
Steve Barker

My 5hp/20gal compressor draws 15A.

-Bob S.

Reply to
Bob S.

My CH compressor manual calls it a pressure switch. It's a pressure operated contactor that opens the ac line input when it gets to operating pressure. I once had a pressure switch go bad (weak spring & arcing contacts) and it would trip the breaker like the OP described.

-Bob S.

Reply to
Bob S.

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