Dryer trips washer GFCI

[pipe_bender]

Here is a mystery for the gang;
Installed some GFCI's in a basement laundry room in a older apartment building one dryer is gas the other is electric.
Got a call that now whenever a dryer runs the GFCI for the washer next to it trips.
Each washer was on its own breaker I did not do anything to the dryers.
It even happens if the washer is not running, these are commercial coin operated units.
The lighting is on a different circuit and got converted to LED around the same time, nothing else changed.
Panel is older SQD QO.
Any ideas what the issue is?
Thanks

 

[CoolWill]

So which dryer causes it, the gas or the electric? The gas dryer is usually plugged into a 120 volt receptacle, so I'd be looking to see if that receptacle is protected by the GFCI. If so, it could be fault in the dryer or the cord. Or there could be a neutral mixed up between receptacles.

 

[pipe_bender]

So which dryer causes it, the gas or the electric? The gas dryer is usually plugged into a 120 volt receptacle, so I'd be looking to see if that receptacle is protected by the GFCI. If so, it could be fault in the dryer or the cord. Or there could be a neutral mixed up between receptacles.

Thanks for the reply its the electric dryer. On one side there is just a washer and electric dryer wedged right next to each other probably added later from the looks of it. My plug cheap tester said the wiring was ok and I tested the GFCI.

 

[Elect117]

There might be a neutral to case bond on the old gas dryer?

Is the gas dryer and the new electric dryer on the same branch circuit?

Are the GFCI breaker type or receptacle type?

It could be a nuisance trip due to VFD or similar effects.

What are the voltages? All units 120V? or are they 240V or 208V?

 

[hillbilly1]

Maybe a fault in the washer, and the ground is not connected, and either the dryer is touching by vibration, or someone is touching both the dryer and washer when they start the dryer making it appear the dryer is tripping the washer. Try a temporary jumper between them to see if it trips.

 

[pipe_bender]

There might be a neutral to case bond on the old gas dryer?

Is the gas dryer and the new electric dryer on the same branch circuit?

No they each have their own breakers.

Are the GFCI breaker type or receptacle type?

Receptacle

It could be a nuisance trip due to VFD or similar effects.

What are the voltages? All units 120V? or are they 240V or 208V?

The washers and gas dryer are 120V
The electric dryer is 208.
Thanks

 

[hillbilly1]

There might be a neutral to case bond on the old gas dryer?

Is the gas dryer and the new electric dryer on the same branch circuit?

Are the GFCI breaker type or receptacle type?

It could be a nuisance trip due to VFD or similar effects.

What are the voltages? All units 120V? or are they 240V or 208V?

I thought about the neutral to ground bond on the dryer, but that should only trip the gfi if the dryer is on one, shouldn’t affect the washer.

 

[pipe_bender]

Maybe a fault in the washer, and the ground is not connected, and either the dryer is touching by vibration, or someone is touching both the dryer and washer when they start the dryer making it appear the dryer is tripping the washer. Try a temporary jumper between them to see if it trips.

Good call, I'll try this thanks.

 

[Elect117]

Are any of these a multiwire branch circuit?

Is the EGC shared from the Dryer to the GFCI receptacle? Is the EGC pulled from a splice or does it run through the GFCI?

Are the water and gas piping metal? Or is the water line plastic?

I am trying to see if there is a wiring reason for the GFCI to see an imbalance.

 

[pipe_bender]

Are any of these a multiwire branch circuit?

Yes they all are, but the electric dryer is on its own 2-pole 30.

Is the EGC shared from the Dryer to the GFCI receptacle? Is the EGC pulled from a splice or does it run through the GFCI?

There is no ground wire its all metal conduit (EMT or Flex) as the ground, my cheap plug tester said the grounding was correct.

Are the water and gas piping metal? Or is the water line plastic?

All the water and gas piping is metal
Thanks

 

[AC\DC]

Could the element be damaged. I hear story’s of the stoves causing issue when there fresh from the overseas slave camps.

Maybe the humidity in the dryer causing it.
I would say it’s something with the element the fact that the other one is not tripping.

 

[Elect117]

Yes they all are, but the electric dryer is on its own 2-pole 30.

There is no ground wire its all metal conduit (EMT or Flex) as the ground, my cheap plug tester said the grounding was correct.

All the water and gas piping is metal
Thanks

Are the dryer(s) and the washer(s) run in the same conduit?

Can you recreate the trip while you are there? With the washer running and without? Is this the customer's wording or first hand seeing it?

It is kinda hard to tell from here what the issue might be. On your next visit, if you could take photos of the connections / wiring from the gas dryer, electric dryers and the GFCI receptacle to the washer(s) that would help.

I am guessing there is some kind of residual or leakage current on the EGC from either the new electric dryer or from a neutral to equipment connection on an old piece of equipment. And if they are all bonded by touching, same conduit systems, gas pipe bonded to water pipe, then there could be some parallel pathing back to the panel they are all feed from. One of the parallel paths could be the connection through the GFCI and it is registering the imbalance and tripping.

Could the element be damaged. I hear story’s of the stoves causing issue when there fresh from the overseas slave camps.

Maybe the humidity in the dryer causing it.
I would say it’s something with the element the fact that the other one is not tripping.

Also good advise to investigate.

 

[winnie]

Total spitball guess here: There dryer neutral is tied to the washing machine neutral downstream of the GFCI, _and_ the GFCI neutral-ground fault detection isn't working. When the dryer runs it injects enough current on the neutral to trip the residual current detection of the GFCI.

 

[pipe_bender]

Thanks for the tips everyone I went back and here is the update,
Short piece of wire touching washer and dryer triped GFCI.
checked the cords, washer cord ohmed out ok no ground faults replaced it anyway, gfci still tripped when washer touched dryer.
Checked dryer cord it was very stuck in the receptacle, plastic around neutral pin slightly melted.
Replaced that with a 4-wire cord/ and recept and the problem is solved.
So a weak neutral to the dryer, but whats weird is dryer was working, and the problem was only with a GFCI.
Thanks again for all the tips.

 

[Elect117]

The weak neutral and the physical touching of the dryer to the washer was creating a parallel path for the neutral current through the case of the washer and into the EGC and tripping the GFCI.

 

[wwhitney]

The weak neutral and the physical touching of the dryer to the washer was creating a parallel path for the neutral current through the case of the washer and into the EGC and tripping the GFCI.

I don't follow this explanation, nor do I see a scenario where a "weak neutral" is relevant.

If I understand the OP, the work done that led to (or perhaps revealed) the problem was installing GFCIs on the washers (which I assume are 120V), with no change to the dryers. If the GFCI on the washer was tripping, there was a current imbalance on the hot/neutral. Another circuit's neutral current returning on the washer's neutral conductor would certainly cause that.

But what is the path from the dryer circuit's neutral to the washer circuit's neutral? The two chassis' touching each other can certainly be a connection between the two circuits' EGCs, but those EGCs are already connected elsewhere. And to get a path between the two circuits' neutrals via the EGC would require neutral/ground faults on each circuit. Any neutral/ground fault on the washer circuit should trip the washer GFCI, certainly during washer operation, independent of what the dryer is doing.

So I'm not seeing the mechanism for the dryer to be putting current on the washer's neutral only when the dryer is running. Is it possible there was some other miswiring that got fixed when the dryer cord and receptacle were replaced?

Even if the dryer previously had a 3-wire cord, so that its chassis was connected to neutral, and its neutral current could return via its chassis touching the washer's chassis and thus through the washer's EGC, that should not trip the washer GFCI.

Cheers, Wayne

 

[winnie]

There is still something not quite clear.

Current from the dryer to the washer frame should not trip the GFCI. The GFCI is monitoring the hot and neutral conductors, not the EGC.

If something external to the washer touching the washer frame is tripping the GFCI, then there has to be some sort of connection from either the hot or the neutral to the frame.

What exactly do you mean by:

Short piece of wire touching washer and dryer triped GFCI.

The washer frame should be solidly grounded. Connecting the washer frame to some other grounded metal shouldn't trip the GFCI

-Jonathan

 

[winnie]

I don't follow this explanation, nor do I see a scenario where a "weak neutral" is relevant.
[...]
But what is the path from the dryer circuit's neutral to the washer circuit's neutral? The two chassis' touching each other can certainly be a connection between the two circuits' EGCs, but those EGCs are already connected elsewhere. And to get a path between the two circuits' neutrals via the EGC would require neutral/ground faults on each circuit. Any neutral/ground fault on the washer circuit should trip the washer GFCI, certainly during washer operation, independent of what the dryer is doing.

Here is another 'out there' scenario: The washer has a neutral to chassis fault, but it is corroded and semiconductive, sort of an accidental Zener. Measure with a multimeter and it is an open circuit. Measure with a resistance tester and it is a short. Or perhaps there is an intentional L-G filter/TVS of some sort.

The 'weak neutral' energized the frame to a couple of volts, high enough to overcome the breakdown voltage of the corroded fault, allowing current to flow from dryer to washer neutral, tripping the GFCI.

I know I'm grasping at straws, but I also don't see a fault in the dryer tripping a properly functioning GFCI on a separate circuit with no other issue (or no other current path between washer frame and washer circuit conductor) present.

-Jonathan

 

[wwhitney]

The washer frame should be solidly grounded. Connecting the washer frame to some other grounded metal shouldn't trip the GFCI

If that grounded metal (EGC) is in fact carrying current (because the dryer was on a 3-wire cord and its chassis was touching the washer chassis, which current would be increased if the cord neutral connection was compromised), can that current induce enough current on the neutral to cause a GFCI to trip?

Or putting it another way, say I have a 12/3 cable which is carrying the hot and neutral of a GFCI protected circuit, and the nuetral only of some other circuit, whose hot is routed through another cable some distance away (obviously a bad design, although for non-metallic wiring methods, allowed by the NEC). Is there a risk of the GFCI tripping due to the unbalanced current carried in the same cable as the two GFCI protected conductors?

Cheers, Wayne

 

[Elect117]

I don't follow this explanation, nor do I see a scenario where a "weak neutral" is relevant.

If I understand the OP, the work done that led to (or perhaps revealed) the problem was installing GFCIs on the washers (which I assume are 120V), with no change to the dryers. If the GFCI on the washer was tripping, there was a current imbalance on the hot/neutral. Another circuit's neutral current returning on the washer's neutral conductor would certainly cause that.

But what is the path from the dryer circuit's neutral to the washer circuit's neutral? The two chassis' touching each other can certainly be a connection between the two circuits' EGCs, but those EGCs are already connected elsewhere. And to get a path between the two circuits' neutrals via the EGC would require neutral/ground faults on each circuit. Any neutral/ground fault on the washer circuit should trip the washer GFCI, certainly during washer operation, independent of what the dryer is doing.

So I'm not seeing the mechanism for the dryer to be putting current on the washer's neutral only when the dryer is running. Is it possible there was some other miswiring that got fixed when the dryer cord and receptacle were replaced?

Even if the dryer previously had a 3-wire cord, so that its chassis was connected to neutral, and its neutral current could return via its chassis touching the washer's chassis and thus through the washer's EGC, that should not trip the washer GFCI.

Cheers, Wayne

Replaced that with a 4-wire cord/ and recept and the problem is solved.

I take this to mean that the cable might not have had it's wire type EGC bonded properly to the box / conduit. I was assuming that the cases were a parallel path back to their shared neutral / to the panelboard and the GFCI saw a current on the conduit/EGC/neutral with nothing on the phase and tripped.

And from his earlier statements, there shouldn't be a neutral to the dryer since he said it was 2 pole 208V but maybe it is a 2 hots and a neutral run to the dryer. Which is why when he changed it to a 4 wire cord it should have fixed it and became Equipment grounded rather than neutral bonded.

It has been kind of hard to follow. I am still operating on assumptions lol.