Strange Motor Problem Instantly Trips Breaker When Plugged In

[willf650]

There may be something wrong with your unit. But with what you described you have the hot and neutral crossed in your cord setup would be my guess as a starting point.

There should be no path for the current and gfi to trip if the switch is off unless you have wires crossed.

 

[Cruzan80]

Can someone explain how, with his switch OFF, it's still tripping the GFCI?

If the switch is single-pole, and switching the neutral, not the hot, then he could be losing current to ground past the switch (either broken wires inside the yellow cord, or in the motor itself). That would trip the GFCI, even with it "off". It could easily be low enough that his meter didn't catch it, depending on what mode he was in (no load=phantom readings)

 

[Maui]

Given the second unit has a black wire coming out of the motor, it means that all you have identified is that from the white round plug onwards is good. Anything from the yellow prongs back on the first is suspect.

It could be the yellow cord is miswired, broken inside, or a bad connection inside the motor, or grinding dust, or... You need to take the meter out of continuity mode and start checking for resistance, etc, just like you would on any other given suspect motor.

There were several questions about the GFCI being faulty as well as the switched power cord that I wired up being incorrectly wired. This one test should demonstrate that this is not the case. The yellow cord is brand new, and has not been miswired.

I will be happy to provide photos of the opened plug as Frank Lee requested.

 

[Cruzan80]

There were several questions about the GFCI being faulty as well as the switched power cord that I wired up being incorrectly wired. This one test should demonstrate that this is not the case.

No, actually it just showed the GFCI outlet and switch/plug can work with a known good motor. If the switch is wired to break the neutral and not the hot, it would still have the issues described.

I wasn't saying the yellow portion was definitely miswired, but anything from a "known good point" back is suspect. There still could be an internal break in the yellow wires insulation, or theconnections at the motor, or the windings, or dust, or... That was my only point.

 

[signcrafter]

As it turns out I have another Hook-eye unit that I purchased several years ago. I just dug it out and even though it wasn't required, I used the same switched extension cord that I used previously with the other Hook-eye unit to plug in into the outlet. When I flipped the switch on the machine it sprang to life immediately with no issues. I turned it off and then turned it back on again. It ran again without any issues whatsoever. It is obvious that the motor on the other Hook-eye unit has some sort of electrical problem that has yet to be conclusively diagnosed.

But the 1st unit trips the gfi even with the switch off? I'm not an expert but the gfi works by monitoring the current of the hot and neutral so if the switch is off there shouldn't be current to monitor right?

 

[paulsomlo]

How are you "checking continuity"? If you just have a meter that beeps when there's a short, you aren't going to see a high impedance somewhere. It'll just not be a dead short.

Agreed - instead of checking for continuity, go back and do all the same checks with an ohm meter. Your readings should be in the megohm range. If that checks out, the only thing left is a large capacitance between hot and neutral.

 

[PCustoms]

If the switch is single-pole, and switching the neutral, not the hot, then he could be losing current to ground past the switch (either broken wires inside the yellow cord, or in the motor itself). That would trip the GFCI, even with it "off". It could easily be low enough that his meter didn't catch it, depending on what mode he was in (no load=phantom readings)

Ok, this is exactly what I've been thinking.

To start, he's got something wired wrong. With the switch OFF, whatever issue he has should not trip the GFCI

 

[Maui]

No, actually it just showed the GFCI outlet and switch/plug can work with a known good motor. If the switch is wired to break the neutral and not the hot, it would still have the issues described.

I wasn't saying the yellow portion was definitely miswired, but anything from a "known good point" back is suspect. There still could be an internal break in the yellow wires insulation, or theconnections at the motor, or the windings, or dust, or... That was my only point.

The switch is wired to break the hot connection, not the neutral.

 

[Maui]

But the 1st unit trips the gfi even with the switch off? I'm not an expert but the gfi works by monitoring the current of the hot and neutral so if the switch is off there shouldn't be current to monitor right?

If the switch is turned off then there shouldn't be any current flow, correct. It appears that there is some current bleeding from neutral to ground inside the motor with the switch in the off position that is causing the GFCI to trip.

 

[signcrafter]

If the switch is turned off then there shouldn't be any current flow, correct. It appears that there is some current bleeding from neutral to ground inside the motor with the switch in the off position that is causing the GFCI to trip.

That is my thinking. And the gfi monitors the difference between the hot and neutral so if the switch is off there shouldn't be any current flowing so there shouldn't be any difference in between the hot and neutral. Even if the neutral and ground are touching. That shouldn't matter until you turn the switch on and the current flows.

Not sure if it's been said but your switch is switching the black hot wire right?

 

[PCustoms]

Anyone else starting to understand why I asked if OP had an outlet tester?

Switching "black" doesn't mean much if upstream is backwards...

 

[signcrafter]

The switch is wired to break the hot connection, not the neutral.

There has to be something going on with the wiring and not just an issue with the motor. My guess is that there is an issue with the motor, maybe dust or something allowing the neutral and ground to make contact. This would create an imbalance between the hot and neutral. But that shouldn't matter until the switch is flipped. Not sure what the issue is but in my head the gfi should not trip until you turn the switch on, even if there is an issue with the motor. Like mentioned it sounds like the hot and neutral are reversed somewhere. If that is the case then you have hot going to motor even with switch off and guessing flowing back on the ground since the neutral would be broke with switch off, thus creating your imbalance between the hot and neutral. Not sure why the other motor works fine with the same switch. Are the hots hooked to the same spot on both motors?

 

[PCustoms]

Not sure why the other motor works fine with the same switch. Are the hots hooked to the same spot on both motors?

The other motor works fine because it doesn't have a leakage to ground.

OP needs to probe the receptacle on his switch cord to see if he has voltage with the switch OFF

 

[Cruzan80]

The switch is wired to break the hot connection, not the neutral.

If the switch is turned off then there shouldn't be any current flow, correct. It appears that there is some current bleeding from neutral to ground inside the motor with the switch in the off position that is causing the GFCI to trip.

So something is incorrect. You could put a jumper tying neutral and ground together and it wouldnt trip a GFCI if the hot line is off/not connected to anything.

Something is letting hot current pass to another wire. Either the switch is faulty, mis-wired, there is a intermittent break in one of the lines, the incoming wire to the outlet is mixed up, or something. But as it sits, something is incorrect leading hot to be live when you think it isn't (switch off). So you need to figure that out first, then diagnose the motor afterwards. The motor has issues that are revealing the problem with the switch, not that the motor is the only issue.

The easiest way is the outlet tester @PCustoms mentioned above (they are under $20). You could also probe with a meter carefully if you need to to diagnose. But either way, you should fix the wiring first.

 

[Dagny]

motor leaks neutral switched

 

[Maui]

That is my thinking. And the gfi monitors the difference between the hot and neutral so if the switch is off there shouldn't be any current flowing so there shouldn't be any difference in between the hot and neutral. Even if the neutral and ground are touching. That shouldn't matter until you turn the switch on and the current flows.

Not sure if it's been said but your switch is switching the black hot wire right?

The switch is wired to break the hot connection, not the neutral.

There has to be something going on with the wiring and not just an issue with the motor. My guess is that there is an issue with the motor, maybe dust or something allowing the neutral and ground to make contact. This would create an imbalance between the hot and neutral. But that shouldn't matter until the switch is flipped. Not sure what the issue is but in my head the gfi should not trip until you turn the switch on, even if there is an issue with the motor. Like mentioned it sounds like the hot and neutral are reversed somewhere. If that is the case then you have hot going to motor even with switch off and guessing flowing back on the ground since the neutral would be broke with switch off, thus creating your imbalance between the hot and neutral. Not sure why the other motor works fine with the same switch. Are the hots hooked to the same spot on both motors?

The hots are connected to the same spots on both motors, yes.

 

[Shoreline_]

Shouldn't matter if the switch is off though right?

Depends if you're switching neutral or hot. If it's switching hot, I would replace the cord. But they should really check each leg to the case. Before and after the switch.

 

[Maui]

So something is incorrect. You could put a jumper tying neutral and ground together and it wouldnt trip a GFCI if the hot line is off/not connected to anything.

Something is letting hot current pass to another wire. Either the switch is faulty, mis-wired, there is a intermittent break in one of the lines, the incoming wire to the outlet is mixed up, or something. But as it sits, something is incorrect leading hot to be live when you think it isn't (switch off). So you need to figure that out first, then diagnose the motor afterwards. The motor has issues that are revealing the problem with the switch, not that the motor is the only issue.

The easiest way is the outlet tester @PCustoms mentioned above (they are under $20). You could also probe with a meter carefully if you need to to diagnose. But either way, you should fix the wiring first.

I removed the extension cord shown in the photos I already posted that has the switch wired into it and just plugged the yellow wire directly into the outlet (so there was no switch in the circuit at all). What happened was interesting. The GFCI tripped almost immediately yet again, but not before the motor was able to rotate for maybe a revolution or two. I could hear it move.

For the record, the yellow wire was taken from a large coil of brand new wire that I have been using for over a year to repair other motors over that time period. It has worked flawlessly. I checked each wire in that power cord I just made from it this morning several times from the plug to the connectors that attach to the motor. They all show continuity like they should. And in the photos you can see which wires are connected to what prongs on the connector, and how those same wires are connected to the motor.

The problem must be inside the motor.

 

[PCustoms]

@Maui

STOP

You have 2 issue:

1) your motor is leaking current to ground
2) something (your switch or outlet) is wired wrong.

You should diagnose #2 first. You cannot rely on the wire color, you will have to do some testing. With the switch plugged in and OFF, set your meter to check voltage and probe the outlet coming out of the switch:

Hot to ground
Neutral to ground
Hot to neutral

Now turn the switch ON and repeat. Report values back

 

[Cruzan80]

Yes, the motor has something that is leaking current.

The bigger and scarier issue is the the switch box or GFCI itself must have something wrong with it as well, which you only noticed because of the bad motor. Otherwise, the switch (when OFF), would not trip the GFCI, regardless of good or bad motor.

But at this point, you have multiple people telling you the same thing. I am out.

Edit: cross-posted with @PCustoms .

 

[Maui]

@Maui

STOP

You have 2 issue:

1) your motor is leaking current to ground
2) something (your switch or outlet) is wired wrong.

You should diagnose #2 first. You cannot rely on the wire color, you will have to do some testing. With the switch plugged in and OFF, set your meter to check voltage and probe the outlet coming out of the switch:

Hot to ground
Neutral to ground
Hot to neutral

Now turn the switch ON and repeat. Report values back

When I had the inspection done on this house before buying it it was discovered that the Jacuzzi tub had been wired improperly and represented a serious potential safety hazard. I had them bring in a pro to wire it correctly before purchase. As it turns out, the previous owner had done the wiring job himself and got it wrong. It would not shock me if he wired this outlet up himself, and got that wrong too. Best to check. I'll let you know what I find.

 

[RTM]

When I had the inspection done on this house before buying it it was discovered that the Jacuzzi tub had been wired improperly and represented a serious potential safety hazard. I had them bring in a pro to wire it correctly before purchase. As it turns out, the previous owner had done the wiring job himself and got it wrong. It would not shock me if he wired this outlet up himself, and got that wrong too. Best to check. I'll let you know what I find.

The outlet thingie posted above is a quick and relatively cheap test $20ish I imagine, vs bringing in an electrician. When my last two houses were inspected, the guy poked one into every outlet.

 

[Maui]

I just found the very outlet tester PCustoms included in his post on Amazon for about $10. It should arrive some time next week.

 

[Higgins]

I have a vintage 1/4 horsepower single phase motor that is used to power a Hook-Eye knife sharpener. The guy I bought it from told me that it doesn't work, but everything is there. It doesn't appear to be missing any parts, and the motor shaft turns freely. You can spin it with your fingers easily. When I plugged it in it with the switch in the "OFF" position it immediately tripped the in-line breaker on the outlet. I checked the connections between the power cord and switch, found a few loose connections, squared everything up, and the same thing still happened. I removed the power cord and switch that came with it and put them aside, and wired up a brand new power cord, plug and switch that I know is wired correctly and works properly - and I verified this with my ohm meter. Again, I plugged it in with the switch in the "OFF" position so there should not be a completed circuit, and it immediately tripped the breaker again. To make sure the outlet wasn't the problem I plugged my bench top drill press into the same outlet and when I turned it on it fired right up like normal. I checked for connections to ground from the common lead and the hot lead and found none.

I am truly puzzled. How can a motor trip the breaker with the properly wired switch turned OFF??

Brushed are probably gone! See if placements are available!

 

[OccupantRJ]

I just found the very outlet tester PCustoms included in his post on Amazon for about $10. It should arrive some time next week.

They are well worth having for diagnostics. I was at the beach last week and made $100 tip with one checking outlets in a nearby beach house during the time I was there doing a repair for a relative. One receptacle had a bad connection and was intermittently working.

 

[whateg01]

Brushed are probably gone! See if placements are available!

Yeah, I bet that's it!

 

[Hannahranga]

Are you plugging it directly into the GFCI that's tripping? If there's other loads also on that GFCI they'll provide the current flowing back through the ground to trip when someone plugs in a faulty item with a neutral to ground short.

 

[john.k]

I had an issue at work with 300 amp fuses blowing ocassionally. on a compressor......I thought maybe undersized, so I tried some 600 amp I had ........the explosion blew the door off the starter box ,and vaporized the switch gear...........I quickly removed the evidence ,and reported the incident to the new manager ......the compressor motor had shorted windings to earth caused by paint overspray lodging in the cooling ducts ......anyhoo, motor cleaned and rewound ,switchgear replaced ......good as new

 

[FrankLee]

Brushed are probably gone! See if placements are available!

No brushes in that motor.

Those are Emerson-made sleeve bearing motors very similar to this one. @Maui, if you must open that one up, it's very easy.

 

[Shoreline_]

I had an issue at work with 300 amp fuses blowing ocassionally. on a compressor......I thought maybe undersized, so I tried some 600 amp I had ........the explosion blew the door off the starter box ,and vaporized the switch gear...........I quickly removed the evidence ,and reported the incident to the new manager ......the compressor motor had shorted windings to earth caused by paint overspray lodging in the cooling ducts ......anyhoo, motor cleaned and rewound ,switchgear replaced ......good as new

Haha good story. The other week a tech was using the top of a 250hp drive as a shelf and he was missing a 1/2-13 washer on a cooler reinstall. Needless to say we found where it went when we threw the breaker and sent a huge explosion to the back of the compressor room. 25k later drive replaced.

 

[MacMcMacmac]

Could a neutral be bonded to ground somewhere in the house?

 

[PCustoms]

Could a neutral be bonded to ground somewhere in the house?

I hope so!

 

[MacMcMacmac]

I'm not talking about the box. I've seen ground wires sparking when I disconnected them because someone was using ground for a neutral.