5mA vs. 30mA sensitivity GFCI breaker

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curious101

Senior Member
Location
Atlanta, GA, USA
Good morning,
GFCI breaker is causing nuisance tripping for a food warming equipment in a small commercial project, where customers can use this food warming equipment, but the the whole business is not about food, of course. To solve this problem, motor rated GFCI was selected. The 5mA sensitivity GFCI (which is good for personnel protection) was still causing nuisance tripping. Would it be acceptable by NEC to use a 30mA sensitivity (equipment protection) GFCI breaker for this food warming equipment?
Thanks, and have a great day!
 
augie47

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
GFCI protects people, GFP protetcs equipment.
GFP is not acceptable whwere GFCI is required.
 
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winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
Thus the next step is to analyze the reason that GFCI was used in the first place.

If GFCI is being used where the NEC doesn't require it, then 30mA GFPE can be used.

You should also determine what load characteristic is causing tripping. If it is real leakage then perhaps it should be fixed (though physics always requires some leakage). If it is transient leakage associated with motor starting, then a _different_ GFCI might solve the problem. The GFCI standard has a time/current curve that permits much higher than 5mA leakage for short time, but most GFCIs trip much faster than this curve.

-Jon
 
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curious101

Senior Member
Location
Atlanta, GA, USA
winnie said:
Thus the next step is to analyze the reason that GFCI was used in the first place.

If GFCI is being used where the NEC doesn't require it, then 30mA GFPE can be used.

You should also determine what load characteristic is causing tripping. If it is real leakage then perhaps it should be fixed (though physics always requires some leakage). If it is transient leakage associated with motor starting, then a _different_ GFCI might solve the problem. The GFCI standard has a time/current curve that permits much higher than 5mA leakage for short time, but most GFCIs trip much faster than this curve.

-Jon
Click to expand...
Thank you! Yes, it needs GFCI per NEC. So I have to talk to the GFCI manufacturer which 5mA GFCI trips a little bit more slowly, correct?
Do you know who can analyze problems like you described (it it's a real leakage or transient leakage problem)? Thanks again!
 
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winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
curious101 said:
Thank you! Yes, it needs GFCI per NEC. So I have to talk to the GFCI manufacturer which 5mA GFCI trips a little bit more slowly, correct?
Do you know who can analyze problems like you described (it it's a real leakage or transient leakage problem)? Thanks again!
Click to expand...

The tool you need is a peak reading clamp meter or an oscilloscope with a current probe that can reliably read in the milliamp range. My experience is more in the lab, not in the field, so I don't know who near you would do this sort of work, or what equipment to recommend.

-Jon
 
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curious101

Senior Member
Location
Atlanta, GA, USA
winnie said:
The tool you need is a peak reading clamp meter or an oscilloscope with a current probe that can reliably read in the milliamp range. My experience is more in the lab, not in the field, so I don't know who near you would do this sort of work, or what equipment to recommend.

-Jon
Click to expand...
Okay! Thank you so much!
 
synchro

synchro

Senior Member
Location
Chicago, IL
Occupation
EE
curious101 said:
Good morning,
GFCI breaker is causing nuisance tripping for a food warming equipment in a small commercial project, where customers can use this food warming equipment, but the the whole business is not about food, of course. To solve this problem, motor rated GFCI was selected. The 5mA sensitivity GFCI (which is good for personnel protection) was still causing nuisance tripping. ...
Click to expand...
Is this equipment portable such that it can be moved off site and check whether it trips a GFCI located somewhere else? That could help verify whether the equipment itself is the problem.
Also, are there other GFCI breakers in the panel (presumably not tripping)? Sometimes there can be loads that put noise on the panel bus and cause tripping of GFCI breakers on other circuits.
 
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jap

Senior Member
Occupation
Electrician
This brings up an interesting point.

If there was a ground fault leakage on a non GFI protected circuit in a commercial kitchen with stainless steel tables, sinks, etc..., and, that leakage energized all the metal objects in the kitchen, what would protect the person standing on the wet floor in contact with the energized metal objects?

The GFI circuit breakers or GFI receptacles would not sense that their output and return had a leakage since they would be monitoring the difference in the potential of the phases or phase to neutral conductors associated with what was connected to them.

Not the culprit that caused the leakage.

JAP>
 
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curious101

Senior Member
Location
Atlanta, GA, USA
synchro said:
Is this equipment portable such that it can be moved off site and check whether it trips a GFCI located somewhere else? That could help verify whether the equipment itself is the problem.
Also, are there other GFCI breakers in the panel (presumably not tripping)? Sometimes there can be loads that put noise on the panel bus and cause tripping of GFCI breakers on other circuits.
Click to expand...
Thank you! Yes, I think they tested that the food equipment worked correctly on other GFCI. They need somebody on the site to analyze the situation. Who is usually responsible for this? The manufacturer of the food equipment, the manufacturer of the breaker/panel or the engineer of record or all?
 
C

curious101

Senior Member
Location
Atlanta, GA, USA
jap said:
This brings up an interesting point.

If there was a ground fault leakage on a non GFI protected circuit in a commercial kitchen with stainless steel tables, sinks, etc..., and, that leakage energized all the metal objects in the kitchen, what would protect the person standing on the wet floor in contact with the energized metal objects?

The GFI circuit breakers or GFI receptacles would not sense that their output and return had a leakage since they would be monitoring the difference in the potential of the phases or phase to neutral conductors associated with what was connected to them.

Not the culprit that caused the leakage.

JAP>
Click to expand...
Thank you! They need somebody on the site to analyze the situation. Who is usually responsible for this? The manufacturer of the food equipment, the manufacturer of the breaker/panel or the engineer of record or all?
 
J

jap

Senior Member
Occupation
Electrician
I was simply posing this as a question to see if any more knowledgeable folks on this forum could chime in on their thoughts about this.

Your situation got me to wondering if a fault on a non gfi protected circuit could still be a hazard even on GFI protected piece of equipment.

I think there's a chance it could be.

JAP>
 
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