# Motor tripping GFCI



## mrbc (Apr 9, 2014)

The recent thread on motor start capacitors, and link to a motor maintenance thread by Chaincarver Steve jogged my memory...

So I have a Dayton 1/2 HP cap start motor on my drill press. I had to put a new power cord on it and replaced a 2-wire cord (which was long ago cut anyway.. it got it used) with a 3-wire cord. I wired the ground to the ground point on the rear end bell. When I buttoned everything up and tested it, it tripped the GCFI my garage outlets are on when I tried to turn it on.

Its not too too old, maybe from the 90's, certainly not as old as the 1/4 HP Galvin I have. No visible internal damage, etc. Would the spike/draw from startup be the cause? The house is a year old so I doubt it's a bad GFCI. Some posters from Chaincarver's motor repair thread from a few years ago mentioned that they did electrical repair as part of their careers, so I thought I might get good opinions... Thanks.

Bob


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## GeorgeC (Jul 30, 2008)

Have you tried the saw on a non GFCI outlet?

I assume that you tried it more than once??

George


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## Steve Neul (Sep 2, 2011)

That is a very common problem with GFCI outlets. The only real solution is to put the motor on a non-GFCI outlet. When an electrician wires a house they have to put GFCI outlets in wet locations. Since the garage has the potential of water or having someone attach an extension cord and go outdoors with it the GFCI outlet is used. The circuit breaker won't help you, it will only trip when the wire heats up beyond the amp rating. The GFCI is sensitive to a sudden surge of power which the motor provides. As far as the GFCI knows you are standing in water and grabbed a hot wire and suddenly there is current going to ground. If the GFCI is just at the outlet just change the receptical to a non-GFCI one. Just be aware you run more of a risk of electrocution if there is ever water on the floor. Sometimes the GFCI is at the breaker box and you would have to change the breaker.


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## m.n.j.chell (May 12, 2016)

Of course, there's also the possibility that, if it only had a two wire cord before, your not really grounding "just the case" with your three wire cord. If it runs without popping a circuit breaker, on a non GFCI outlet, then you're good. If it pops the circuit breaker, then you can't attach the ground wire to the case!


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## TomCT2 (May 16, 2014)

when I ran a new circuit as part of my basement shop rebuild, I thought to put a GFCI breaker in the box.

the local supply house guy 'warned' me, not all motors play well with circuit breaker type GFCI - he suggested a "at the outlet" type - with all the outlets "wired through"

putting on my best mule imitation, I did the circuit breaker anyway.
I have a drill press and joiner from the 60's - they work fine.
a radial arm saw from 1975 trips the breaker instantly (3 prong)
all the other (newer) stuff works....including hand tools - some 2 prong, some three prong.

so, like the man said, some motors don't play nice. 
I kept the GFCI, I'll need it when the place is sold, but put a std breaker in for me....
it's is a basement, GFCI is required by code, but since I'm smart enough to know splashing around in (non-existent) water is not a good idea, I'll take the risk.


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## woodnthings (Jan 24, 2009)

*search ... isolation circuit for 120 volts ...*

http://www.a-seamarine.com/volt.php

It may be that the ground and neutral wires are interchanged within the motor? at the outlet? Get a circuit tester from Home Depot and check your polarity:

http://www.homedepot.com/p/Commerci...0;jsessionid=807A2A663B67DBA6AB4F2FE17CC53C72


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## mrbc (Apr 9, 2014)

I have a circuit tester. I'll double check that and I have now tired in my garage and my new detached garage/shop and it trips in both places. I might run a dedicated non-GFI circuit for inside or just a dedicated outlet for that tool. My table saw doesn't trip anything and that's a 1.75 HP. 

I'm going to try and check for continuity between the windings and the case (It'd be nice if I had a megger). When I got the motor (used), I had to swap the wiring so it would spin the correct direction. I have all the correct colored leads on the correct terminals per the diagram on the label, I wonder if . Some of the winding leads had dried out insulation and I had to splice a replacement for one since it's insulation crumbled when I manipulated it. I suppose is stronger evidence for an internal problem, but I'll also try it on a non-GFI to see if it trips a breaker.

I added a toggle switch which is in a metal gang box, the box is safety grounded. The motor is a resilient mount and isolated from the bracket. My switch box ground, the power cord ground and the ground in the pigtail between the switch and the motor are tied together. Could I be creating a ground loop by hooking up the ground at the case as well?


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## Pineknot_86 (Feb 19, 2016)

Had a refrigerator that did the same thing. Kept tripping the circuit breaker in the panel. Scrapped it.


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## mrbc (Apr 9, 2014)

Well it doesn't trip the breaker on a regular circuit. A quick check of the windings seems to show fine with no obvious issues. Looks like it's a nuisance trip of the gfci. 

Sent from my SM-G920V using Tapatalk


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## woodnthings (Jan 24, 2009)

*OK, then ...*

Here's what I would do. I would enlarge the opening to accept a 4" square box and install a regular outlet ahead of the GFI. Then wire the GFI in parallel on the other side of the standard outlet. That way you still have protection for code and safety reasons, but you have an outlet that you can use for the machine. 0






mrbc said:


> Well it doesn't trip the breaker on a regular circuit. A quick check of the windings seems to show fine with no obvious issues. Looks like it's a nuisance trip of the gfci.
> 
> Sent from my SM-G920V using Tapatalk


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## ryan50hrl (Jun 30, 2012)

While I agree the solution is likely a non gfci outlet, just putting one in parallel is no more to code than just removing it.


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## Steve Neul (Sep 2, 2011)

The OP should know if the area where his equipment is happens to be a wet location or not. If it's dry and causing trouble I would get rid of it. It might only have to be up to code if the house is being sold and could be replaced at that time.


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## mrbc (Apr 9, 2014)

Yea it's a dry area. Because of where it plan to put the press, and where that is in relation the the panel, and where the builders put through gfci, I think I'll run a dedicated circuit for that tool. Then I'll just put a gfci on that circuit if we ever sell the place. I might just make that recepticle the first on the new circuit and put a new gfci after it if I decide I need more outlets.

Sent from my SM-G920V using Tapatalk


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## TimPa (Jan 27, 2010)

you replaced a power supply cord with a grounded style, it trips the gfci. it does not make sense to remove any safety measures provided by gfci circuits in the basement, and breaking code no less, because a new power cord/connection manifested the issue.


have you tried removing the ground wire from the connection at the dp? likely the gfci trip will stop. 


use an ohmmeter to check resistance between the black wire at the dp with respect to the ground point, and the white wire with respect to the ground point. they should be infinity. it may mean opening the motor up and ensuring there is no frayed wire strand touching the housing.


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## ryan50hrl (Jun 30, 2012)

Is rather have a grounded saw than a gfci if it's one or another.


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## Brian(J) (Feb 22, 2016)

Steve Neul said:


> Since the garage has the potential of water or having someone attach an extension cord and go outdoors with it the GFCI outlet is used. The circuit breaker won't help you, it will only trip when the wire heats up beyond the amp rating. The GFCI is sensitive to a sudden surge of power which the motor provides. As far as the GFCI knows you are standing in water and grabbed a hot wire and suddenly there is current going to ground. If the GFCI is just at the outlet just change the receptical to a non-GFCI one. Just be aware you run more of a risk of electrocution if there is ever water on the floor. Sometimes the GFCI is at the breaker box and you would have to change the breaker.


Hi,
with respect, this isn't an accurate description of how circuit breakers and GFCI's work. All CB's react to the heat as stated, almost all also have a device that reacts to sudden spikes in current. A GFCI reacts to the imbalance between current going out and current coming back and does not detect the amount of power on any level. Your example, standing in water and getting a shock means current is going into the ground and not back to the Ground Fault device, so it trips. 
Opinion, if the tool is operated in a dry area, remove the GFCI. If the tool is used in a wet area, really should replace with a double-insulated tool, will come with a two-prong plug.


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## jdonhowe (Jul 25, 2014)

+1 on TimPa's comments. As Brian said, a GFCI detects differences between current coming in through the hot (black) lead, and exiting by the neutral (white) lead; it trips if there's a difference.

I suspect that there's a short between the neutral wire and the ground wire inside the motor, so current is passing through both, and thereby tripping the GFCI. Don't bypass codes- check out the motor!


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## ryan50hrl (Jun 30, 2012)

You might try a different brand of gfci outlet. I have one fairly inexpensive gfci outlet on a lighting circuit that trips from time to time when both switches are shut off simultaneously. 

I've narrowed it down to a crappy outlet.


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## mrbc (Apr 9, 2014)

TimPa said:


> have you tried removing the ground wire from the connection at the dp? likely the gfci trip will stop.
> 
> 
> use an ohmmeter to check resistance between the black wire at the dp with respect to the ground point, and the white wire with respect to the ground point. they should be infinity. it may mean opening the motor up and ensuring there is no frayed wire strand touching the housing.


You mean at the switch, run the ground straight to the motor? I thought of that, but I believe the switch housing needs to be grounded since it's a metal box. 
@jdonhowe: Yea, hopefully I'll have some time when I get off duty tomorrow to open up the end bell, pull out the terminal board and get a better look at the leads, check the windings better, and maybe repair some insulation.
@ryan50hrl: I'll try another GFCI. It's new construction, but I know that doesn't always mean too much...

@ anyone: When I checked it on a non-GFCI outlet I had the wiring cover off, so I got a decent view in the rear end bell. The centrifugal switch made an arc/flash when it disengaged. Is that itself an indication of dirty, or otherwise imperfect, contacts in the switch, and thus a possible reason (thought maybe not the only one) the GFCI is tripping?

Thanks for all the opinions!! 

PS: Anyone know if it's practical to try and get the stator out of the casing to see if it's a problem with a winding???


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## mrbc (Apr 9, 2014)

Ok. I have a pic of the motor label, and I tracked down a wiring diagram. The schematic reads "start - run" beneath terminal 4, and reads "ungrounded side" beneath 1, 2 and 3. So do I read correctly to have the Hot from the power cord go to lug 1 and the neutral to lug 4 (which is also the centrifugal switch)? I'll need to double check they're in the right place. The old power cord (which was cut and without the plug) was like a lamp cord (where you peel the two halves or the rubber sheath apart) so there was no white and black.

EDIT: I think I see it now, L2 is lug 4. L1 is lug 1. The diagram (schematic) is hard to read, like a scan of an old paper....


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## mrbc (Apr 9, 2014)

Turns out I had the neutral and hot on the wrong terminals. It ran fine a few times then started popping real bad and tripping the gfi. Opening up the motor I see that I should really replace some winding leads. The insulation is old and crumbly. And, it looks like burn Marks on my L1 terminal from the arcing. I can't see anything wrong there other than very old solder on the back of the terminal going to the klixon. Maybe it's a bad connection that flowing new solder can fix.

This cheap old motor is getting involved. I have another to put on so now I can tinker with this and figure out how to fix it. I hope to fix it since it's a dual voltage. Seems like it ought to come in handy at some point if not back on my ancient drill press.

Sent from my SM-G920V using Tapatalk


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## woodnthings (Jan 24, 2009)

*I was close ....*



woodnthings said:


> http://www.a-seamarine.com/volt.php
> 
> It may be that the ground and neutral wires are interchanged within the motor? at the outlet? Get a circuit tester from Home Depot and check your polarity:


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## mrbc (Apr 9, 2014)

woodnthings said:


> woodnthings said:
> 
> 
> > http://www.a-seamarine.com/volt.php
> ...


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## TimPa (Jan 27, 2010)

not many 120v motors will have a problem when the hot and neutral are reversed to the motor. nice catch on the ungrounded note.

if the conductors themselves are good, you can slip a piece of heat shrink tubing over the bad insulation, if the replacement is too difficult.


good luck


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