GEC allowed in FMC?

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solarpower

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Hello electrical gurus

I had a discussion recently with an inspector about the use of FMC over a GEC.
We ran a combination GEC/EGC sized to the GEC spec in EMT out of our solar inverter and bonded it at the entrance to the conduit run and transitioned from the conduit to an LB to FMC for about a 2 foot run inside a closed wall and then into the main service panel. We bonded the FMC connector with a grounding bushing in the box per GEC requirements.
The inspector said the GEC annot be in FMC even under a 6' run. is this correct? I can't find anything in the GEC section or FMC section of the code to disallow it.
thanks
K
 
solarpower said:
Hello electrical gurus

I had a discussion recently with an inspector about the use of FMC over a GEC.
We ran a combination GEC/EGC sized to the GEC spec in EMT out of our solar inverter and bonded it at the entrance to the conduit run and transitioned from the conduit to an LB to FMC for about a 2 foot run inside a closed wall and then into the main service panel. We bonded the FMC connector with a grounding bushing in the box per GEC requirements.
The inspector said the GEC annot be in FMC even under a 6' run. is this correct? I can't find anything in the GEC section or FMC section of the code to disallow it.
thanks
K
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I'm not sure there is even a requirement that the GEC be in conduit at all.
 
I am not reading this clearly - are you running a conductor in the fmc, or are you trying to use the fmc as the egc ?
 
Look at 250.64(B)

There is a list of what type of raceways can be used for a GEC. FMC is not in the list. However, cable armor is. Would FMC be considered cable armor? Or is this directly referencing armored ground type cable?

There are also some variations based on size. What size is your GEC? If it is #4 or larger, I think FMC is okay.

I had never really paid close scrutiny to 250.64(B). In my opinion, FMC should be in the list as acceptable racewyas for a GEC.
 
crossman said:
Look at 250.64(B)

There is a list of what type of raceways can be used for a GEC. FMC is not in the list. However, cable armor is. Would FMC be considered cable armor? Or is this directly referencing armored ground type cable?

There are also some variations based on size. What size is your GEC? If it is #4 or larger, I think FMC is okay.

I had never really paid close scrutiny to 250.64(B). In my opinion, FMC should be in the list as acceptable racewyas for a GEC.
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I never looked much at it either. FMC is not on the list of so if it is smaller than #6 you are out of luck.
 
Seems we should be able to use FMC where the GEC enters a transformer. I see it done all the time. Yet if it is #6 or smaller, it may be a technical violation?
 
This is puzzling. 250.64 allows the installation of conductors in "cable armor". I cannot find a definition for what cable armor is. I cannot find where the term is used elsewhere in the code. I suspect that it was meant to cover FMC, Liquidtite FMC, etc., but with no definition, who knows?
 
Interesting question in the OP.

Flexible metal conduit (FMC) is not on the list of things suitable for physical protection of the Grounding Electrode Conductor (GEC).

Cable armor is included, but what is cable armor/ "Cable armor" appears 25 times in the NECH, yet it is not defined.

If I consider a single conductor cable type AC with a steel sheath, then I can imagine something like FMC, except for the drain wire that is inside the sheath and in intimate contact with it.

The important distinction, seems to me, is that armor on cable is allowed, but flexible conduits are not allowed.
 
Thanks for all the responses and insight, I'm relieved to know I wasn't missing something commonly known.

to furthur explain:
We ran the GEC in question in EMT and FMC with the AC output wires of the inverter back to the main service, making them the equivalent of a branch circuit as far as the code goes. The GEC acted as the EGC and was bonded like a GEC would be everywhere.
We ocassionally have to do this with FMC to make a tough transition from an external conduit run into a recessed main service without opening a large piece of the finished exterior wall.

The armor sheathed GEC is required in our LA branch AFAIK and is run the same way we would do a bare solid #6 GEC here.

So....reading the posts, it isn't allowed? or is there still a question about it?

thanks
 
augie47 said:
Interesting. Wonder how much they sell ?
250.64(E) also mentions cable armor in the bonding requirement.
One would wonder if it's worth the trouble compared to non-ferrous.
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I have only seen in in old installs - #8.
I personally would just install #6 or #4, to avoid using something like this, unless I had to protect the GEC somehow.
 
solarpower said:
Thanks for all the responses and insight, I'm relieved to know I wasn't missing something commonly known.

to furthur explain:
We ran the GEC in question in EMT and FMC with the AC output wires of the inverter back to the main service, making them the equivalent of a branch circuit as far as the code goes. The GEC acted as the EGC and was bonded like a GEC would be everywhere.
We ocassionally have to do this with FMC to make a tough transition from an external conduit run into a recessed main service without opening a large piece of the finished exterior wall.

The armor sheathed GEC is required in our LA branch AFAIK and is run the same way we would do a bare solid #6 GEC here.

So....reading the posts, it isn't allowed? or is there still a question about it?

thanks
Click to expand...

I believe there is still a question. Since the term "cable armor" is not defined, the AHJ will need to interpret what is meant. If they interpret this to mean FMC or Liquidtite FMC, I would say it would be allowed. If they don't, it is not. Someone has to decide on the definition, since it is not given in the NEC, it will be up to the AHJ. If "the inspector" is the AHJ (or acts on behalf of the AHJ) in your area, you have your answer; he has decided it is not acceptable. If someone else is the AHJ, youwill need an interpretation from them. Remember that "approved" means "acceptable to the Authority Having Jurisdiction".
 
haskindm said:
I believe there is still a question. Since the term "cable armor" is not defined, the AHJ will need to interpret what is meant. If they interpret this to mean FMC or Liquidtite FMC, I would say it would be allowed. If they don't, it is not. Someone has to decide on the definition, since it is not given in the NEC, it will be up to the AHJ. If "the inspector" is the AHJ (or acts on behalf of the AHJ) in your area, you have your answer; he has decided it is not acceptable. If someone else is the AHJ, youwill need an interpretation from them. Remember that "approved" means "acceptable to the Authority Having Jurisdiction".
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I see no way to claim the armor on FMC is cable armor as FMC is not cable.
 
But does cable armor mean "the armor for a cable". When I install conductors in FMC, have I created an armored cable assembly? Without a definition, it means whatever the AHJ wants it to mean. I am not arguing that it is acceptable. If it was acceptable I think it should have been included in the list of acceptable methods. I am not sure what the rationale is for it NOT being acceptable if that was the panels intent. But without a definition I have no idea what cable armor is or where to buy some. It is sort of like the requirement for AFCI's. The code gives a list of specific areas where GFCI's are required, bedrooms, hallways, living rooms, etc., and then tells us that they are also required in "similar rooms and areas". The code does not define what a living room or a bedroom is. We have one inspector in this area that is trying to require AFCI's in kitchens, claiming that this is a "similar area". I maintain that kitchens, bathrooms, and now closets are the only rooms that are defined by the NEC. If the panel had wanted to include these rooms they would have said so, as we have definitions for them. Undefined terms lead to misunderstandings.
 
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haskindm said:
But does cable armor mean "the armor for a cable". When I install conductors in FMC, have I created an armored cable assembly?
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I don't see how you can create a cable. The only cables the NEC recoginzes are those in the various chapter 3 articles.

All you have done is put some conductors in a raceway, not created a cable.
 
haskindm said:
Without a definition, it means whatever the AHJ wants it to mean. I am not arguing that it is acceptable.
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But there is a definition.

Remember:
2008 NEC Definitions
Article 100
Scope This article contains only those definitions essential to the proper application of this Code. It is not intended to include commonly defined general terms or commonly defined technical terms from related codes and standards. . .

(and from the NEC Handbook commentary directly after the "Scope") -- Commonly defined general terms include those terms defined in general English language dictionaries and terms that are not used in a unique or restricted manner in the NEC. Commonly defined technical terms such as volt (abbreviated V) and ampere (abbreviated A) are found in the IEEE Standard Dictionary of Electrical and Electronic Terms.
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Take your dictionary down and look up "cable". My little one shows the #2 definition of cable as:
a number of wires for conducting electricity, bound together in a cylindrical sheath.
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Yes, but cable armor is speaking of cable armor not cable. Cable in this instance is an adjective, not a noun.

Definition of "armor" is - a tough, protective outer covering

Cable armor to me is a jacket that provides armor for cable.

250.64 doesn't mention armored cable. It mentions cable armor.
 
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