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Nuisance Trip GFCI

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LT Sparky

Member
Location
Farwell, TX, United States
Occupation
Estimator Project Manager
Got called to a coffee shop that is having their gfci breakers on multiple machines tripping. Each is on a dedicated circuit. We don't see any problems with the wiring. Any ideas on what we can do?
 
tallgirl

tallgirl

Senior Member
Location
Glendale, WI
Occupation
Controls Systems firmware engineer
LT Sparky said:
Got called to a coffee shop that is having their gfci breakers on multiple machines tripping. Each is on a dedicated circuit. We don't see any problems with the wiring. Any ideas on what we can do?
Click to expand...
How many is "Multiple" and what percentage?

Fast way to rule out "bad machines versus bad wiring" is move them around.
 
GeorgeB

GeorgeB

ElectroHydraulics engineer (retired)
Location
Greenville SC
Occupation
Retired
Check for power strips for bad line-neutral, line-ground, neutral-ground MOVs. I've had 2 trip my GFCIs.
 
W

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
You say nuisance tripping, which implies that there is nothing wrong yet the GFCI trips.

A very real possibility is that there is a small amount of leakage inherent to the design of the machines and that the breaker is doing exactly what it is supposed to do.

We can argue that this small leakage is inevitable and should be permitted, or that higher leakage should be permitted if there is assured grounding, or that the manufacturers should build the machines differently.

I'd suggest measuring the leakage current of the machines in operation. If the leakage is excessive then go to the manufacturer for a fix.

Jon
 
tom baker

tom baker

First Chief Moderator & NEC Expert
Staff member
Location
Bremerton, Washington
Occupation
Master Electrician
The GFCIs are are tripping due to a ground fault over 6mA. Is the fault 10, 20 or more?
First generation GFCIs were more prone to nuisance tripping, UL standards for GFCIs and appliances have reduced that.
Take the machine that causes trips , move it, does the problem stay or follow?
 
R

ramsy

Roger Ruhle dba NoFixNoPay
Location
LA basin, CA
Occupation
Service Electrician 2020 NEC
Jraef said:
New machines with electronics on them?
Click to expand...

Leviton AGTR runs appliances that trip other GFCI's.

More appliances work on good wiring, however it's AFCI function is known to trip from utility issues, or typical equipment carbonization on existing wiring.
 
synchro

synchro

Senior Member
Location
Chicago, IL
Occupation
EE
It's conceivable to me that a transient overvoltage from to a poor connection upstream of the neutral bar could cause false tripping of multple GFCIs. In such a case, the line to neutral voltage feeding the GFCIs might be temporarily exceeding their operational range and causing them to false trigger. This is just a WAG. But measurements of the line to neutral voltages vs. loading applied on one phase could be used to determine if there is a bad neutral.
 
R

ramsy

Roger Ruhle dba NoFixNoPay
Location
LA basin, CA
Occupation
Service Electrician 2020 NEC
synchro said:
..measurements of the line to neutral voltages vs. loading applied on one phase could be used to determine if there is a bad neutral.
Click to expand...

Thanks for explaining this.

Never understood how line voltage occurs from Neutral to Grounding, much less how something in between occurs after shutting off the breaker.

Like a good knucklehead, if solenoid tester wont remove confusion we re-terminate replacements per 460.4(D) & 110.14.

Don't need to think about why crap won't work if we just remove it, like panel flippers, and builders that insist on re-wring the entire building.

But now I see, impedance from carbonized or broken Neutrals change N-G potential from near Zero to line voltage.

And for ~line voltages after shut down, my knuckle head can now visualize the cross-tied circuit.
 
mtnelect

mtnelect

HVAC & Electrical Contractor
Location
Southern California
Occupation
Contractor, C10 & C20 - Semi Retired
"Phantom Tripping" This is such a common problem ! The solution: 1. When installing a "GFI/AFI" circuit all the neutrals have to be dedicated to that circuit. 2. That means that at all junction boxes all neutrals need to be identified. 3. Do not mix neutrals ! 4. Problem solved !!
 
ptonsparky

ptonsparky

Tom
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
mtnelect said:
"Phantom Tripping" This is such a common problem ! The solution: 1. When installing a "GFI/AFI" circuit all the neutrals have to be dedicated to that circuit. 2. That means that at all junction boxes all neutrals need to be identified. 3. Do not mix neutrals ! 4. Problem solved !
Click to expand...
A good share of the time, Yes. There are other causes beyond a misplaced neutral.
 
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