Debate on over Flex as Grounding Conductor

[brother]

I just want to be sure Im not reading it wrong, as there is a debate going on. A flex (less than 6ft) was installed in patient care area, hospital, and also a ground wire was installed. The circuit is on a 20 amp breaker. The debate is that the 'flex' no longer qualifies as an egc because of the flexibility was necessary, so therefore because of the redundant grounding requirment in 2008 NEC 517.13, its a violation.

I say it (THE FLEX) does qualify as an egc, and just because the 'flexibility' was necessary that code section only means that the ground wire must be installed, not that the flex itself is not longer a ground path. This is my understanding of 2008 nec 250.118(6)e. Am I right??

 

[augie47]

excellent question. the notes in the handbook accompanying 517,13(A) seems to limit the use of flex in p.c. areas to areas where it's not used for flexibility

 

[nakulak]

I don't know the answer to your question (I believe it will be an interpretation), but since all the health care seems to be directed towards a fully functional grounded sheath (HCF, etc), I don't think that the flex complies. That doesn't mean your ahj won't allow it though.

 

[brother]

excellent question. the notes in the handbook accompanying 517,13(A) seems to limit the use of flex in p.c. areas to areas where it's not used for flexibility

notes are one thing, but NEC CODE is another, I cannot find anything that would 'disqualify' the flex in this scenerio. If you know of a code section, please specify.

 

[brother]

I don't know the answer to your question (I believe it will be an interpretation), but since all the health care seems to be directed towards a fully functional grounded sheath (HCF, etc), I don't think that the flex complies. That doesn't mean your ahj won't allow it though.

Then tell how the flex is 'disqualified' and is 'no longer a fully functional grounded' metal raceway according to section 2008 NEC 250.118

 

[brother]

I don't know the answer to your question (I believe it will be an interpretation), but since all the health care seems to be directed towards a fully functional grounded sheath (HCF, etc), I don't think that the flex complies. That doesn't mean your ahj won't allow it though.

Then tell me how the flex is 'disqualified' and is 'no longer a fully functional grounded' metal raceway according to section 2008 NEC 250.118. I'm sorry, but I just don't see how an AHJ can interpet it another way.

 

[augie47]

it seems to me that the requirement of an added EGC when flexibility is necessary indicates some unreliability in the flex under those conditions.
were the decision left up to me, I would not accept it,

 

[brother]

it seems to me that the requirement of an added EGC when flexibility is necessary indicates some unreliability in the flex under those conditions.
were the decision left up to me, I would not accept it,

I can only say that 'maybe' some degree of unreliability of the flex when the flexibility is necessary, but NEC doesn't say that.

If we use that same logic of 'if a ground wire is installed the the conduit is unreliable as an egc, in all conditions' is a gross missinterpation of the NEC.

If you fail, or would not accept the installation, what code section would you cite??

 

[augie47]

517.13, to me the need for the EGC indicates that when flexibility is involved the flex does not qualify by itself.
that is obviously an opinion, but it is supported by the handbook narrative, so it's not just my opinion.

 

[augie47]

brother, the other side of the coin is that I know of no other wiring method that would be acceptable where flexibilty is required. Hopefully we will get additional input.

 

[brother]

517.13, to me the need for the EGC indicates that when flexibility is involved the flex does not qualify by itself.
that is obviously an opinion, but it is supported by the handbook narrative, so it's not just my opinion.

So the 'handbook narratives and multiple opinions' are what you use to enforce code, even when the NEC actually permits it?? Im sorry to say but that sounds like you not being a 'fair' and good inspector when it come to electrical installations.

 

[jaylectricity]

I don't understand why it being necessary to flex changes the make up of a single piece of metal that just coils around itself to form a raceway?

 

[brother]

I don't understand why it being necessary to flex changes the make up of a single piece of metal that just coils around itself to form a raceway?

What??? having trouble understanding your question, can you rephrase it?

 

[Regularkevin]

IMHO you should refer to Article 348.60 which will refer you to 250.118(5)

I also agree that 517.13(B) is important to review which, in turn, will refer you to 250.118(5) & 250.122

 

[SG-1]

Liquidtight flexable Metal Conduit is a listed product, but it is not listed for grounding by any nationally recognizied laboratory.
It is allowed to be used many places with severe restrictions.

I think some have overlooked that 250.118(6)(e) says where flexability is necessary after installation.

The cable armor must qualify as an EGC.

There is a type AC & a MC "AP" cable with green coloured armor that also provides an EGC and clearly meets the requirements for a patient care area.

 

[infinity]

I agree with SG-1 that you need to include the words after installation in 250.118(6)(e) as part of the debate. The FMC is just fine as a ground path if the flexibility is not required after installation.

 

[augie47]

Agreed, Rob. I'm still at a loss as to what wiring method you would use is flexibility is desired after installation. MC-CAP ?
It would seem if you needed flexibility you would use cord, but not in a Art 517 install.

 

[roger]

It is allowed, 250.118(5) recognizes the FMC as an EGC itself when it meets the conditions of 250.118(5), which in turn meets the requirement of 517.13(A). When an insulated EGC is added into the FMC the requirement of 517.13(B) is met.

Roger

 

[jaylectricity]

I don't understand why it being necessary to flex changes the make up of a single piece of metal that just coils around itself to form a raceway?

What??? having trouble understanding your question, can you rephrase it?

I'm probably going off the beaten path, but what I'm wondering is what flexibility has to do with whether or not the metal jacket remains suitable for an EGC. It is all one long piece of metal strap spiraling along the conductors. Whether you flex it here or there, it's still a continuous path of metal.

 

[iwire]

I'm probably going off the beaten path, but what I'm wondering is what flexibility has to do with whether or not the metal jacket remains suitable for an EGC. It is all one long piece of metal strap spiraling along the conductors. Whether you flex it here or there, it's still a continuous path of metal.

There is a difference to the NEC, if you only need it to flex during installation it can be an EGC. However if it needs to flex after the installation, say some wiring going to a door that has to open and close once in a while, in that case the NEC requires a wire ground inside the flex regardless of length.