GFI question - from a master

[wyreman]

har har that must get some attention =0

so i have made "all" the mistakes with gfi's that i can think of :angel:
but this one has me scratching my emojicon:?

tea shop with two circuits only on the countertop
report is that the gfis keep tripping

i go there and cant replicate the fault

further investigation says they mostly trip in the morning when certain appliances are bringing the water up to temp

but i ran all the appliances really hard when i was there and couldnt replicate the fault - tripped the 2p breaker before the gfis [middle pair on 25quad]

mwbc feeds the counter and the gfis are pigtailed to the shared neutral and one power leg

so my thinking is
that the water heating appliances may exhibit some internal fault mostly in the morning when they come up to temp
or
that some voltage imbalance is bothering the gfis at a certain time of day being there are a bunch of mwbc at that counter -
powering the undercounter fridges
but i originally ruled that out because i had steady power off the pigtail [shouldnt care much about beyond the pigtail]
or
in the morning they are doing some water cleaning action at the counter and that is getting in the plug connection

action takenI replaced the gfis with new WR and TR units

Here is the bizarre key: the 2nd GFI [leviton] i replaced failed immediately out of the box - a very rare occurance- [[in the last 20 years was the last time that happened]]
right out of the box it would would trip immediately - BUT only when connected to the ground
### so i thought "ahha! must be some bootleg ground touching here"
but i didn't see that in the box - so i tried replacing the unit [troubleshooting for people in a hurry] and it "seemed ok to me"
so i chalked up the erratic behavior to a bad device - but i didnt really trust that judgemnet
###and now i have a callback in the morning - want to get some consensus on my way there

there was no voltage between N-G during the interval i measured
any idears?

I need to be able to replicate the fault where the gfi opens

<B>Fig. 1.</b> All 15A and 20A, 125V receptacles located in an area with a sink and permanent facilities for food preparation and cooking must be GFCI protected.

 

[just the cowboy]

Put tea pots in fridge

Put tea pots in fridge

Put the tea pots in the fridge to bring them down to first startup temperature. A element may be bad but when it heats up the fault clears and stays clear till it gets cold again

 

[Dennis Alwon]

If it is tripping the breaker you have an issue with overload, short circuit, or ground fault.

 

[Dennis Alwon]

Also I would not trust the reports. Make sure it is the gfci that is tripping and not the breaker. It may be that the fault or short did damage to the gfci and that is why you had to replace it. Problem seems to be in the equipment

 

[JFletcher]

Any way to get there first thing in the morning when they start up? I think your first thought is likely the correct answer.

Just curious, if you have 2 GFCI on a MWBC, and lose/have problems with the neutral upstream (line side), what would happen to the GFCIs? Would they not see it, still work w/o GFCI protection, or both simultaneously trip?

The last two pics; the neutral wire was out of the pigtail, wrapped around one GFCI screw, then continued to the other? Never have thought to install them that way, would have just run two jumpers from the wirenut, one to each. Interesting.

 

[al hildenbrand]

I think your first thought is likely the correct answer.

I agree. The GFI device replacement is the equivalent of taking the appliance to a different GFI, and with the same trip behavior, that leaves a fault in the appliance itself. (Bad luck on the bad-out-of-the-box device, though.)

Just curious, if you have 2 GFCI on a MWBC, and lose/have problems with the neutral upstream (line side), what would happen to the GFCIs? Would they not see it, still work w/o GFCI protection, or both simultaneously trip?

Interesting question. IMO, As the amount of load increases on any one of the GFI load side connections, the voltage across the OTHER GFI will swing closer and closer to full line to line voltage. At some voltage level the electronics of that GFI will fry.

 

[GoldDigger]

Just curious, if you have 2 GFCI on a MWBC, and lose/have problems with the neutral upstream (line side), what would happen to the GFCIs? Would they not see it, still work w/o GFCI protection, or both simultaneously trip?

Since the only point where current from L1 can cross over to return on L2 will be upstream of the two GFCIs they will both still see a balanced current on their L and N terminals. The fact that the N voltage shifts does not change the current balance.
If the GFCI has circuitry which tries to sense N to EGC stray connections it might be damaged by the offset voltage and there is also is a very good chance that one GFCI will see an undervoltage condition and fail while the other may see an overvoltage from L to N and be damaged.

 

[mopowr steve]

Maybe this will help you determine problem.

I had a church report that a gfi would trip in a kitchen while making coffee. They had a 2 burner Bunn coffee maker that I wound up taking back to shop to investigate.

What I found was that a silicone washer between the filling tray and heating tank would leak allowing water to lay on top of the heating tank (usually shortly after filling and unit coming up to temp) and then drip down onto the thermostat and also lay around a high limit snap disc.
I could also see evidence of leaking because of the white calcium deposit on the tank.

Makes things hard to find when water from filling or steam or leaks within these type of appliances trip GFCI's when your not there to catch it.

 

[Rick Fitz]

Split the neutrals pull a neutral for each phase

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[jason414]

I'm siding with mopower steve. That's some great investigation my friend! Can't tell who said it but the neutral being jumpered is not proper, pigtailing it is definitely the answer. Because to me, that would cause nuisance tripping when jumpered. So when one trips both would trip. What brand is the equipment and where is it made? As much as things are regulated there is still sub-par equipment that we assume is adequate and rule it out when it might actually be the culperate.


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[FionaZuppa]

what type of tea pot machines are they? are they inductive by any chance?