using a GFCI as a shunt trip, how creative?

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hurk27

Senior Member
Location
Portage, Indiana NEC: 2008
Ok I guess I have never thought of using a GFCI as a shunt trip for receptacles under a cooking hood in a commercial kitchen, but this is what I found today when called to trouble shoot a power outage for these same receptacles.

Not sure who thought of this or wired it this way but it does work, heres how I found it, two sets of multi-wire circuits feeding 4 duplex receptacles from two 20 amp two pole GFCI breakers in the panel, in the kitchen a white #12 THHN conductor ran from one each of the receptacles so that one receptacle from each GFCI breaker had this neutral wire connected to it's neutral, these two whites ran in EMT to the Ansel system micro switch box, which had two micro switch's in it, each neutral went to the NO. terminal on each and a green jumped to each common terminal and was bonded to the box.

Now I think there has got to be something in the code that wouldn't allow this yes it works simply because as soon as the neutral is grounded the GFCI trips, but I can't even put my finger on it as I have never seen any requirement for a listed way to shut off the power under a hood, we use shunt trips, contactor's, and never are they listed for this purpose, is this a possibly way to do this? not that I would:ashamed1:

Talk about being creative.:eek:
 
480sparky

480sparky

Senior Member
Location
Iowegia
The Ansul system is the fire suppression side of the equation. They usually come with nothing more than a contact or two which consist of a couple of microswitches. Sometimes hoods will come from the factory with a pre-fabbed control box. Otherwise, it's up to us to engineer a legal way to do what's needed when the system trips. Shut off power, turn on the exhaust fan, trip the fire alarm system......
 
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hurk27

Senior Member
Location
Portage, Indiana NEC: 2008
Well there spec's didn't help much either:

2.2.4 Regulated Release Mechanism: The regulated release
mechanism shall be a spring-loaded,
mechanical/pneumatic type capable of providing the
expellant gas supply to one or two agent tanks
depending on the capacity of the gas cartridge used or
three 3.0 gallon (11.4 L) agent storage tanks in certain
applications. It shall contain a factory installed regulator
deadset at 110 psi (7.6 bar) with an external relief
of approximately 180 psi (12.4 bar).
It shall have the following actuation capabilities: automatic
actuation by a fusible link detection system and
remote manual actuation by a mechanical pull station.
The regulated release mechanism shall contain a
release assembly, regulator, expellant gas hose, and
agent storage tank housed in a stainless steel enclosure
with cover. The enclosure shall contain knockouts
for 1/2 in. conduit. The cover shall contain an
opening for a visual status indicator.
It shall be compatible with mechanical gas shut-off
devices; or, when equipped with a field or factoryinstalled
switch(es), it shall be compatible with electric
gas line or appliance shut-off devices, or connections
to a building fire alarm control panel.
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Guess one could say it's compatible with a GFCI since it does what it's supposed to do:roll:
 
kwired

kwired

Electron manager
Location
NE Nebraska
ceb58 said:
I will say that it is creative. It was probably cheaper to do it that way than a shunt breaker.
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It would be cheaper yet to just fault the circuit to ground using a standard breaker, you would be replacing control switches often however:cool:
 
Rick Christopherson

Rick Christopherson

Senior Member
480sparky said:
Creative? Yes.

Legal? No.....110.3(B)
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This setup does not violate 110.3(B). The breakers are installed as per instruction. The shunt to ground is occurring in the downstream circuit. The GFCI is operating as it is designed. The switch is a device (load) not part of the supply, so even the fact that it creates an intentional shunt to ground is not an automatic violation.

It may not be the wisest thing to keep tripping a GFCI, but I don't believe there is any prohibition of it.
 
480sparky

480sparky

Senior Member
Location
Iowegia
Rick Christopherson said:
This setup does not violate 110.3(B). The breakers are installed as per instruction. The shunt to ground is occurring in the downstream circuit. The GFCI is operating as it is designed. The switch is a device (load) not part of the supply, so even the fact that it creates an intentional shunt to ground is not an automatic violation.

It may not be the wisest thing to keep tripping a GFCI, but I don't believe there is any prohibition of it.
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So where is it in the GFCI's instructions on how to install it to act as a shunt trip?
 
Rick Christopherson

Rick Christopherson

Senior Member
480sparky said:
So where is it in the GFCI's instructions on how to install it to act as a shunt trip?
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Right below the paragraph where it tells you not to. :D

I didn't say it was a good idea, but it is not correct to say it is prohibited based on 110.3(B). If you can locate a manufacturer's instructions that say the GFCI breaker is not intended to detect a neutral to ground short, then you could claim 110.3(B) as an effective prohibition. But without that, it does not fail on those grounds.

I have seen (I think) GFCI receptacle instructions saying do not short the outlet to test, but that is not applicable here on 2 counts--(1) it's not to test, and (2) it's not a receptacle.
 
Rick Christopherson

Rick Christopherson

Senior Member
480sparky said:
So I guess I can bury 1900 boxes in my yard to splice a cut UF cable, because the instructions don't tell me I can't.
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Is 110.3(B) the only section of code you are familiar with? Of course not. We all know you better than that. However, you can't blanket anything and everything under one section of code as though it works for every thing. If that was the case, the NEC book would be a lot thinner.

The listing for a leviton light switch does not say it is specifically listed for use with a Regal Ambassador model 7869 lamp, but does that mean it cannot be used for that application? Nope.
 
Rick Christopherson

Rick Christopherson

Senior Member
480sparky said:
99.999% of the rest of the Code doesn't apply to the discussion, does it?
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When the words of the NEC are originally hammered out on a computer keyboard, they are nothing more than the contents of a simple document created by a private company. However, for those jurisdictions where the NEC was promulgated into law by an act of the local legislation (most of the United States), it becomes a full legal document. As such, you cannot simply read its words willy nilly. Those words now have legal meaning and legal interpretation.

The fact that no aspect of the code applies to this situation means just that....It's not covered under any law. Please forgive the implication, but something like "Designer Drugs" is a perfect example of how the law works. At the time some idiot comes up with the recipe for some new designer drug that does not already fall under an existing law regarding its contents, that drug is not illegal to make or sell. (Extacy fell under this problem years ago.) New laws had to be passed specifically for these designer drugs before it became illegal to manufacture or distribute them.

Because the NEC is enacted by law in most jurisdictions, you cannot simply blanket any situation by citing 110.3(B) on the basis that nothing else fits the situation. 110.3(B) does not fit the situation either, so blindly claiming it as grounds for an interpretation is not applicable. If the manufacturer's instructions do not prohibit the application, then 110.3(B) cannot be applied to prohibit that use either.
 
480sparky

480sparky

Senior Member
Location
Iowegia
Rick Christopherson said:
When the words of the NEC are originally hammered out on a computer keyboard,..
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In 1897?

Rick Christopherson said:
...they are nothing more than the contents of a simple document created by a private company. ...
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Not a private company. A conglomerate of industries with ties to the electrical trades.


Rick Christopherson said:
.......it becomes a full legal document. As such, you cannot simply read its words willy nilly....
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Nothing new here for me. But tell me, how does anything in Chapter 8 apply? Article 702? Article 410? Is raceway fill an issue here? Conductor derating? Ambient temperature? Classified locations? PV systems? Electric vehicles? What Codes do you propose apply to the discussion?
 
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Volta

Senior Member
Location
Columbus, Ohio
'Course, we need to know what version was in effect when this was installed, per 2011 you could call it on:

200.4 Neutral conductors shall not be used for more than one branch circuit, for more than one multiwire branch circuit, or for more than one set of ungrounded feeder conductors unless specifically permitted elsewhere in this Code.

250.24(A)(5) Load-Side Grounding Connections. A grounded conductor shall not be connected to normally non?currentcarrying metal parts of equipment, to equipment grounding conductor(s), or be reconnected to ground on the load side of the service disconnecting means except as otherwise permitted in this article.

and I guess,

300.20(A) Conductors Grouped Together. Where conductors carrying alternating current are installed in ferrous metal enclosures or ferrous metal raceways, they shall be arranged so as to avoid heating the surrounding ferrous metal by induction. To accomplish this, all phase conductors and, where used, the grounded conductor and all equipment grounding conductors shall be grouped together.

Though the last two could have been overcome by simply connecting the two neutrals together through the microswitch rather that regrounding. Also I think the first is new this cycle. All-in-all, pretty minor code issues, except I would prefer to see the devices open the neutrals as well as the hots. Else we have rebonded the neutral until the Ansul is reset. My way, we have simply paralleled the two, and the EGC is left alone.
 
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hurk27

Senior Member
Location
Portage, Indiana NEC: 2008
Volta said:
'Course, we need to know what version was in effect when this was installed, per 2011 you could call it on:
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Had to be around 2003-4 which could have bee still on the 1999 here in Indiana

Volta said:
200.4 Neutral conductors shall not be used for more than one branch circuit, for more than one multi-wire branch circuit, or for more than one set of ungrounded feeder conductors unless specifically permitted elsewhere in this Code.
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under normal conditions the neutrals would be separate since they are only connected together when the Ansul system has tripped, Not sure if GFCI breakers also disconnect the neutrals but I know for a fact receptacle GFCI's do as well as blank face ones.

Volta said:
250.24(A)(5) Load-Side Grounding Connections. A grounded conductor shall not be connected to normally non?current carrying metal parts of equipment, to equipment grounding conductor(s), or be reconnected to ground on the load side of the service disconnecting means except as otherwise permitted in this article.
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same answer as above

Volta said:
and I guess,

300.20(A) Conductors Grouped Together. Where conductors carrying alternating current are installed in ferrous metal enclosures or ferrous metal raceways, they shall be arranged so as to avoid heating the surrounding ferrous metal by induction. To accomplish this, all phase conductors and, where used, the grounded conductor and all equipment grounding conductors shall be grouped together.
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I don't think this would ever be a problem since there is no normal load through these neutrals before or after the Ansul system has tripped.

Volta said:
Though the last two could have been overcome by simply connecting the two neutrals together through the micro switch rather that re-grounding. Also I think the first is new this cycle. All-in-all, pretty minor code issues, except I would prefer to see the devices open the neutrals as well as the hots. Else we have re-bonded the neutral until the Ansul is reset. My way, we have simply paralleled the two, and the EGC is left alone.
Click to expand...

Again they are not connected together at anytime under normal conditions as the GFCI's would never reset if they were, they only connect together when the Ansul system is tripped which then the two micro's take both neutrals to ground causing the GFCI's to trip under the grounded neutral sensor system built into every UL listed GFCI, this is a second current transformer injected at a higher frequency (120hz) then the main one (60hz) for the sole purpose of detecting grounded neutrals and mis-wiring of GFCI's, again I'm not sure a breaker GFCI disconnects the neutral but I do know for sure that a receptacle or blank face ones do.
 
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