Range Tripping GFCI (210.8, 555.53)

[don_resqcapt19]

Just an observation:

An EGC provides protection against various single failures, e.g. a hot shorting against the frame.

A GFCI + EGC provides protection against various double failures, e.g. the frame becomes discontinuous, and the hot shorts to the part of the frame that isn't connected to the EGC.

Cheers, Wayne

The very reason that the original GFCI requirements were only for receptacles as the likelihood of a double failure for hard wired equipment is much less than for cord and plug connected equipment.

 

[wwhitney]

The very reason that the original GFCI requirements were only for receptacles as the likelihood of a double failure for hard wired equipment is much less than for cord and plug connected equipment.

But IIRC, the facts supporting the introduction of 210.8(F) involved such a double failure for hard-wired equipment. So they do happen, and it's a societal judgement call what level of safety is the appropriate tradeoff point. [I'm not taking a position on that question.]

Cheers, Wayne

 

[don_resqcapt19]

But IIRC, the facts supporting the introduction of 210.8(F) involved such a double failure for hard-wired equipment. So they do happen, and it's a societal judgement call what level of safety is the appropriate tradeoff point. [I'm not taking a position on that question.]

Cheers, Wayne

Those facts were skewed to make a point. The LFMC, in the cited incident, was not fastened in place as required by the code rules and because of that it was not suitable for use as the required equipment grounding conductor. There was no wire type EGC or bonding jumper. It should have had a wire type bonding jumper or a wire type EGC to be code compliant.
We can't make rules to cover all potential code violations.

 

[gene6]

Unless the leakage current is high enough to cause a huge amount of voltage drop on the EGC..

Interesting thanks

 

[tortuga]

A GFCI + EGC provides protection against various double failures, e.g. the frame becomes discontinuous, and the hot shorts to the part of the frame that isn't connected to the EGC.

Just to add my obligatory range observation ;
the code still allows existing range circuits to use a neutral as the equipment ground (or the equipment ground as a neutral depending on how you look at it), (250.140) and be mechanically connected to a gas pipe (combo gas cooktop / electric oven) and a water pipe (pot fillers).
Now consider all the double failure modes in these 3-wire range setups.

Rather than GFCI all new ranges, I'd prefer nudging range manufacturers make straight rated '208/240V' ranges and not use the neutral for the light and clock or whatever. That way all the existing 3-wire SE cable circuits could stay in place, and there would be cost savings on new construction as we could go back to running 2-wire + EGC for ranges like we did for the last century.
All NEMA would need to do is reclassify a 10-50 receptacle the same as a 6-50, job done.

 

[curt swartz]

Rather than GFCI all new ranges, I'd prefer nudging range manufacturers make straight rated '208/240V' ranges and not use the neutral for the light and clock or whatever. That way all the existing 3-wire SE cable circuits could stay in place, and there would be cost savings on new construction as we could go back to running 2-wire + EGC for ranges like we did for the last century.
All NEMA would need to do is reclassify a 10-50 receptacle the same as a 6-50, job done.

Ranges have never been wired with 2 hots + EGC. Prior to the 4-wire requirement is was 2 hots + Neutral. The neutral was permitted to be bare if part of an SE cable and originated in the service panel.

Allowing a 10-50 to be connected to an EGC instead of neutral would be hazardous. What happens when someone plugs something into it that requires a neutral and draws a significant neutral current? All the current will be on EGC system and undersized EGC wire or possible the metal raceway if used.

 

[tortuga]

Allowing a 10-50 to be connected to an EGC instead of neutral would be hazardous.

Thats a good point, it used to be done around here all the time for welders and farm equipment so much so that I never trust a 10-50 to have a neutral unless it in a residential kitchen.
So let me amend my 208/240 range suggestion to a NEMA 6-50.

 

[jap]

All good suggestions, but, what's the solution. when you install GFI protection for the range or anything else and it nusence trips?

We're required to install GFI protection, and, the customer wants to use their Range.

Who gives?

Jap>

 

[Fred B]

All good suggestions, but, what's the solution. when you install GFI protection for the range or anything else and it nusence trips?

We're required to install GFI protection, and, the customer wants to use their Range.

Who gives?

Jap>

The homeowner gets a handyman to change out to a standard breaker. They're usually uninsured, untrained, and "can do anything", and hold no liability, (so they think). And when it fails or an injury occurs you better have documentation that you installed the GFCI (if required by local or state codes) as the last person of record having worked on the system.

 

[tortuga]

All good suggestions, but, what's the solution. when you install GFI protection for the range or anything else and it nusence trips?

We're required to install GFI protection, and, the customer wants to use their Range.

Who gives?

Jap>

I'd say use 90.4(C) and get written special permission to either not use a GFCI or use a GFPE breaker

 

[don_resqcapt19]

I'd say use 90.4(C) and get written special permission to either not use a GFCI or use a GFPE breaker

I can't imagine any inspection authority taking on the civil liability that a written permission to eliminate a safety requirement of the NEC would result in. I know that in general that employees of a unit of government cannot be sued, but the unit of government can be, and maybe even the employee as I can see the courts saying this is well beyond simple negligence that sovereign immunity provides protection from.

 

[tortuga]

But IIRC, the facts supporting the introduction of 210.8(F) involved such a double failure for hard-wired equipment. So they do happen

Those facts were skewed to make a point. The LFMC, in the cited incident, was not fastened in place as required by the code rules and because of that it was not suitable for use as the required equipment grounding conductor.

Id be interested to read that and pass it along, if you have a source for that information?

I can't imagine any inspection authority taking on the civil liability that a written permission to eliminate a safety requirement of the NEC

Perhaps here its the state and they modify the NEC and removed that GFCI requirement, and as you said its a flawed code section.

 

[don_resqcapt19]

Id be interested to read that and pass it along, if you have a source for that information?

Perhaps here its the state and they modify the NEC and removed that GFCI requirement, and as you said its a flawed code section.

Just the pictures of the installation that were on line at the time of the Public Input. No idea if they are still out there.

The adoption modification of a rule in the NEC is much different from the use of 90.4.

 

[ptonsparky]

I've been advocating some arrangement where the GFCI permits greater leakage if the EGC is detected to be intact.

That would be easy. Include the EG in the sensing coil and determine an acceptable imbalance. Simple.

 

[wwhitney]

That would be easy. Include the EG in the sensing coil and determine an acceptable imbalance. Simple.

If you have just one sensing coil and put the EGC through it, then you could have an arbitrary amount of current flow from hot to EGC and not trip the GFCI. You could have two separate sensing coils, one with EGC through it and one without, and use a tripping criterion that depends on both measurements.

Cheers, Wayne

 

[ptonsparky]

If you have just one sensing coil and put the EGC through it, then you could have an arbitrary amount of current flow from hot to EGC and not trip the GFCI. You could have two separate sensing coils, one with EGC through it and one without, and use a tripping criterion that depends on both measurements.

Cheers, Wayne

As long as the EG is intact and carrying the entire fault current why would it matter? The breaker would eventually trip at OC or SC levels.

 

[wwhitney]

As long as the EG is intact and carrying the entire fault current why would it matter? The breaker would eventually trip at OC or SC levels.

Well, that fault carried by the EGC could be a person between hot and EGC. So such a mechanism would provide a level of safety lower than what a GFCI provides. I would think you'd still want to trip on 20 ma or 30 ma of hot to EGC fault current.

Cheers, Wayne

 

[ptonsparky]

Well, that fault carried by the EGC could be a person between hot and EGC. So such a mechanism would provide a level of safety lower than what a GFCI provides. I would think you'd still want to trip on 20 ma or 30 ma of hot to EGC fault current.

Cheers, Wayne

Details. Dang.

 

[kwired]

This has been my attitude for years. I wish that it would catch on more. We would all be safer.

I kind of agree, but it is NEC that needs to pick up that concept. I'm not planning to shell out the cost for GFPE breakers for something that isn't supposed to be prone to leakage other than when something is wrong on something that isn't really prone to losing the EGC either. If oven element fails to ground and draws significant current one of two things or even both will happen: it won't heat up like it should when using it, it will still continue to put out some heat even when it has been turned off. Either of those should be prompting the owner to get it looked at, meanwhile the current is carried by the EGC keeping touch voltages around the appliance in check. If no other grounded objects within reach you never have any shock hazard anyway, but a range hood is pretty common and does introduce that possibility.

 

[kwired]

I think your pointing the finger at the wrong party there, you should be looking at the clown who sold you a 10k fridge that can't run on a GFCI.
I have been visiting family with young kids this weekend, a 1, 3 and 5 year old, in this house the fridge is right next to the dishwasher so the young kids can touch the frame of the fridge and the frame of the dishwasher at the same time. They have alphabet and number magnets they move between the two.

When I worked commercial one of the companies did fast food & institutional kitchen builds in the early to mid 2000's and at some point early on every one had GFCI for all the kitchen equipment, including fridges, not sure if it was a code thing or what, but tons of GFCI in commercial kitchen for a long time.
So why then can whoever makes fridges and freezers for a commercial kitchen that have worked fine on a GFCI for over 20 years not make a ten thousand dollar fridge to work on a GFCI where a young child can sit there and touch it and another grounded appliance?

appliances that have variable speed controllers that are know not to play well with GFCI's are more of a recent thing. Been fighting with customers for years over freezers in garages, unfinished basements, and other areas that required GFCI protected receptacles over providing that GFCI protection. Majority of cases is tripping from surges and they never knew it tripped until a freezer full of food had spoiled, nothing wrong with the freezer otherwise. I have mixed feelings about removing the GFCI like they want and normally do not do that, but will admit I have removed it in some instances.

Have also seen cases where there is a ground fault and did either repair or point out what the problem actually is, on non variable speed driven appliances. Sometimes just a failing defrost heater or one time more recently an internal lamp holder developed an intermittent ground fault.

FWIW a two wire to three wire cheater cord adapter does normally eliminate the high frequency leakage of variable speed driven motor so the GFCI doesn't trip, you still have GFCI protection just no EGC connected to the frame of the appliance anymore. Something to think about even though not really the ideal thing to do either.