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Posted (edited)

I've got a horse and a half motor that has been sitting in the corner of one of my dusty buildings for the past 20 years. It's on an old electric power washer.  Pulled it out today to see if it worked.  It runs for about 10 seconds and then kicks the breaker.  (20amp)  I've blown the dust out of the motor to see if that helped and it didn't.  I'm not using an extension cord, just the original cord on the power washer.  I disconnected the shaft from the pressure pump portion to see if that might be causing the problem and it wasn't.  I've greased the pump and it turns by hand.  Motor turns easily.  Starts just fine so it's not the starter capacitor.

 

Any thoughts from you motor gurus?????

 

 

Edited by Chris Christenberry
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First, try it on another circuit. If it runs fine then that means you need a new breaker.  But if it keeps tripping the breaker, that means that it is pulling more power than the breaker is rated for. So, lets ask a few questions. Is it a single phase or three phase. If its three phase, that could mean it needs 240 instead of 120.

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Good chance it has a starting cap that has gone bad, or a centrifugal switch for a start winding that is stuck.

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On 5/2/2020 at 7:29 PM, Brian Myers said:

First, try it on another circuit. If it runs fine then that means you need a new breaker.  But if it keeps tripping the breaker, that means that it is pulling more power than the breaker is rated for.

This is a good start at trouble shooting.

When ever you are trouble shooting electrical, start at one end and move through the power track to the other. If the new breaker/plug does the same thing, I would check the 20 year old

On 5/2/2020 at 5:23 PM, Chris Christenberry said:

original cord on the power washer.

 

Chances are good there's a soft short in that thing that takes about 10 seconds before it builds up enough charge to arc and trip the breaker. Replace the cord.

If that doesn't work, it's internal to the motor.

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Thanks.  Just got home from running errands.  Will get out and try the motor on the 30 amp circuit.

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Posted (edited)

Okay, the motor bogged down but didn't kick off the 30 amp breaker.  The cord got pretty warm for having only been pulling juice for only about 30 seconds.  So I'm going to replace the cord all the way to the motor and see if that corrects the problem.  If not, then it's time to take the motor to a motor doctor. :D

Edited by Chris Christenberry
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I get why everyone is jumping on the breaker and the cord, but I think something else is going on here.

 

A 1.5hp 120VAC motor will only draw 10 to 12 amps at full load.  Running at no load will be an amp or less.  Motors that small get through the start-up surge in less than a second.  If it is drawing that much current several seconds after starting, with no load, something is wrong with the motor.

 

If it is easy to turn by hand, it must be something electrical.

 

Most obvious possibility is that it is wired up wrong.

 

I have a drill press with a motor that has a start winding rather than a capacitor.  These motors use a centrifugal switch.  The switch in mine is dirty, and I have to listen for it to click out once the motor comes up to speed.  If it doesn't click out, and I don't catch it, the motor will get screaming hot in about 30 seconds.

 

There are things that can go wrong with start caps that may cause the motor phases to run out of balance and get hot.

 

If you can, post a pic of the nameplate on the motor, the wiring diagram in the connection box (If there is one), and a pic of the motor.

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Will do that in the morning, Brian. 

 

However, the power washer was used for several years with no problems.  It was used with this cord and with the motor wired the way it presently is.

I just don't understand why, after setting idle for the past 20 years, it's decided to act up?

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Sitting idle for 20 years is a great way to gum up a centifugal switch...

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..........................and what is a good way to "un-gum" a centrifugal switch?

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Well, if you can get to it, you can zap it with some WD-40 followed by a rinse with alcohol, but they're usually hard to find and/or potentially catastrophic to disassemble.  I always end up with parts left over and it never works again, for instance...:unsure:

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I kind of doubt I'd have the courage to open the motor up considering the knowledge level for that sort of thing I have.  It sure couldn't hurt to try the WD-40 route.  As a side note, years ago when my brother and I owned a manufacturing facility, a salesman walked in our front door lugging a 5-gallon bucket of liquid.  He asked us to bring a dirty, poorly operating motor to the front office so he could show us how to clean it.  We plugged the motor into an outlet and lowered it into the bucket of liquid and the danged thing started purring like a kitten!  Pulled it out and blew out the excess liquid.  I don't think we ever had a problem with that motor again.  I wonder, now that I'm having this problem, just what that liquid was and what it was called.

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Probably carbon tetrachloride, which is illegal now.  It was good for that process, though!  

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Just located an aerosol product called Lectra-Motive Parts Cleaner that's supposed to accomplish the same thing.  I'm headed to Home Depot to pick up a can to see if it solves the problem.  Hope it does because I'm in no position to replace the motor.

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Brake cleaner is a kissing cousin to spray electrical cleaners. 

 

Part of my misspent youth was racing RC cars.  Between every race, I would pull the motor out of the car, and dunk it while running in a motor cleaner like you described.  Usually slung the stuff all over me.  Might explain a few things...

 

  • Haha 1
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