Table Saw Motor Keeps Tripping Circuit Breakers

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  #1  
Old 09-09-11, 08:37 PM
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Table Saw Motor Keeps Tripping Circuit Breakers

Our 40 year old Sears Craftsman table saw is now unusable. It started tripping the circuit breaker of whatever circuit outlet it's plugged into. I'm guessing something is causing it to draw too much current, which trips the breaker?

It's motor model no. 113.12170, 1 hp., capacitor start, 115 volts, 60 cycles, 3450 rpm.

Over the years it has had little use. At Sears website they don't have many parts listed as available for this motor because of it's age. I wonder if a shop could repair it?
 
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  #2  
Old 09-09-11, 08:56 PM
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You could check the amps being drawn with a clamp on ampmeter.

You could probably replace the motor fairly easily.
 
  #3  
Old 09-09-11, 09:12 PM
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Amps

I agree with pcboss. Check the amperage of the motor. It should be listed on the motor ID plate or the owner manual. Make sure you are not using a 15 amp device on a 10 amp circuit. If the saw has not been used much, I doubt the motor is broken. Are you using a grounded outlet?
 
  #4  
Old 09-09-11, 09:48 PM
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I forgot to mention it is a 14 amp motor. The circuit breakers are 20 amps. I've tried it on more than one circuit. It never tripped breakers in the past.
 
  #5  
Old 09-10-11, 12:45 AM
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At forty years of age I would suspect dry bearings are placing a huge starting load on the motor.

Is this a direct drive saw or does it have a belt drive? Does the blade turn easily (Unplug before trying!) and if it is a belt drive try removing the belt and starting just the motor. It could also be a stuck centrifugal starting switch.
 
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Old 09-10-11, 04:12 AM
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Aren't these older motors cap starts, as well? I'm leaning toward a physical thing rather than an electrical malfunction.....bearings, either in the motor or on the mandrel....anything that can cause a drag.
 
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Old 09-10-11, 06:47 AM
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Very common is a stuck start switch. If the motor hums and doesn't turn, even a little, the start switch or open capacitor are suspect. Either of these will cause high currents, even though there is no motion. If, on the other hand, the motor does turn but maybe not full speed, but still trips the breaker, more likely shorted windings, and cause to toss the motor.
 
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Old 09-10-11, 07:41 AM
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What you have is an Emerson motor (and Emerson table saw). Just curious, does the saw have a cast iron table or stamped steel table? Are the motor end bells cast iron? If so, your motor and saw could be much older. A good motor repair shop can probably fix it. A new motor might be the easiest way to address your problem.
 
  #9  
Old 09-10-11, 11:56 AM
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The saw table is cast iron. The motor end caps are cast metal. The motor has oil plugs at the end of the motor caps and has a plate with printing that recommends using a few drops of 20 weight motor oil to lube the wick pads for the bearings. I did that yesterday and blew the dust out of the motor as well.

The motor starts and runs but trips the circuit breaker within a minute or so. It turns very freely by hand with or without the drive belt on it. I noticed the motor housing gets quite hot. Yesterday I started it and as soon as I began making the first cut it tripped the breaker so I unplugged it.
 
  #10  
Old 09-10-11, 12:26 PM
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I think the centrifugal starting switch is stuck in the closed position which is keeping the starting winding in the circuit. That would definitely cause overheating and excessive current draw.

Are you willing to take the motor apart? You may be able to fix this with just some spray solvent and a tiny amount of grease. Or you could take just the motor to a motor repair shop and they could fix you up for (probably) considerably less than a new motor.
 
  #11  
Old 09-10-11, 02:12 PM
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I have the exploded view of the motor in the motor parts list. It doesn't label anything "centrifugal starting switch". It does show something called a "Actuator Assembly, Centrifugal". The small illustration doesn't show any springs or anything. I'm not sure I feel up to taking the motor apart, but maybe I'll give it a try and photograph everything along the way so I can get it back together.

As an option I found this replacement motor, a Grizzly G2533, which a number of people have used to replace their Craftsman table saw motors with.Amazon.com: Grizzly G2533 Motor 1 HP Single-Phase 3450 RPM TEFC 110V/220V: Home Improvement
 
  #12  
Old 09-10-11, 03:40 PM
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The "centrifugal actuator" is what operates the switch. It could be that is is all gummed up and not moving (to open the switch) or it could be that the switch contacts are "welded" together. I'd say go ahead and take the motor apart, you can't hurt it as it doesn't run anyway. At the very worst you will see how a motor and centrifugal switch are constructed.
 
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Old 09-10-11, 04:45 PM
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If you can get the motor to a repair shop and if they can fix it (I am sure they can), your original table saw motor will likely last longer than a "Grizzly" replacement motor.
 
  #14  
Old 09-10-11, 05:38 PM
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I just disassembled/reassembled the motor (thank goodness I bought an inexpensive camera last year with good macro capabilities, a Canon A495). The centrifugal starter assembly works perfectly from what I can tell. When you push on its front plate it slides back on the shaft spreading two thingies along with the coil springs, then snaps back.

I cleaned out about a pound of fine saw dust that was packed into the motor - blowing it out with an air compressor doesn't do anything. You have to disassemble the motor. I was unable to see anything burnt or damaged inside.

Getting the capacitor out of its housing on top of the motor was the hardest part. I don't see any leaking on it. Since the motor starts okay and doesn't make any weird noises I don't think it would be that, or maybe so? Maybe it's worth trying a replacement?
 
  #15  
Old 09-10-11, 07:24 PM
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The centrifugal assembly will push on a contact plate fastened inside the endbell of the motor when it comes up to speed. Pushing on this contact plate should open the switch connecting the starting winding. Check carefully that the switch contacts are not fused together and that they open and close properly.

(image courtesy of alibaba.com)
 
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Old 09-10-11, 08:41 PM
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Thank you for the photo, it helped me understand what you were referring to. It has just one metal tang for the switch. The switch contact opens and closes freely so it's not fused.
 
  #17  
Old 09-10-11, 09:55 PM
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Now I will state that the motor most likely has an internal short circuit in the windings. Rewinding small motors is rarely cost effective if the motor is a standard frame size and replacement is probably the best answer.
 
  #18  
Old 09-11-11, 03:54 PM
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Thank you for your help. I have a feeling you're probably right about replacing the motor now, although I might try a new capacitor just to be certain before I go there. They're only about ten bucks.
 
  #19  
Old 09-12-11, 01:06 AM
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Red face Old Craftsman motor

I just had a capacitor replaced in my 37 yo Craftsman 10 inch radial. The shop said it was something to do with the start switch. I stupidly jammed it by cutting too deep. It didn't trip any circuit breakers though.When I took it apart I couldn't see anything wrong so took it to "hospital". It cost me about $100, but remember I'm using it at 240v 50 cycles (Australia) and the shop was unfamiliar with the motor. They said it was full of sawdust too. I think you could buy a new motor in the US at quite reasonable cost. Horrendous here.
Now I have to reconnect the power plug. Our "hot" wires are not normally black (neutral here) and our 3 prong is Earth/Neutral/Hot so I have to be a bit careful how I connect the neutral. Being an old phart I naturally did not notice how the black and white wires were hooked up to the 3 pin plug before I undid them to get the motor out!.
 
  #20  
Old 09-12-11, 01:58 PM
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I photographed the wiring connectors before I unplugged them so I could get things back together. Anyway, the motor's toast. I ordered a new one. Thanks for suggestions and help.
 
  #21  
Old 09-12-11, 02:55 PM
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It was worth a try! Hope you get your saw back in working order soon.
 
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