Grounding conductor in FMC

[Rgraefen]

I am a municipal inspector and recently had a disagreement with a electrician. I am insisting that he install a grounding conductor within the flexible metal conduit which he installed for lighting whips for ceiling fixtures. He ran EMT to a 1900 box, put in a 6' whip to a control / transformer box for LED wafer light, then added another 6' whip to a second box, and so on. My understanding ( I am not an electrician) is that according to 250.116 (5)(c) of the 2011 NEC, the combined length of the 6' sections of flexible conduit exceeds the maximum of 6' and therefore requires a ground wire.
He insists that because each whip is 6' between boxes that it is not required. The Manufacturer's installation instructions do also specify to connect hot, neutral, and ground wires at each fixture.
I am not trying to be a hard guy, I am only trying to be safe, compliant, and fair. That is why I would love opinions from the members here.
Thank you in advance, the expertise on this forum has been invaluable to me in my occupation.

 

[tom baker]

You are correct that over 6 ft of FMC requires a wire type EGC. If the main run is EMT to each 1900 box, the EMT is the EGC. But the whips require an wire type EGC.

Over 6 ft the impedance is too high for FMC to operate the OCPD in a short circuit.

 

[al hildenbrand]

Welcome to the Forum.

My understanding ( I am not an electrician) is that according to 250.116 (5)(c) of the 2011 NEC, the combined length of the 6' sections of flexible conduit exceeds the maximum of 6' and therefore requires a ground wire.

2011 NEC
ARTICLE 348 Flexible Metal Conduit: Type FMC
348.60 Grounding and Bonding. If used to connect equipment where flexibility is necessary to minimize the transmission of vibration from equipment or to provide flexibility for equipment that requires movement after installation, an equipment grounding conductor shall be installed.
Where flexibility is not required after installation, FMC shall be permitted to be used as an equipment grounding conductor when installed in accordance with 250.118(5).
Where required or installed, equipment grounding conductors shall be installed in accordance with 250.134(B).
Where required or installed, equipment bonding jumpers shall be installed in accordance with 250.102.

250.118 Types of Equipment Grounding Conductors. The equipment grounding conductor run with or enclosing the circuit conductors shall be one or more or a combination of the following:
(5) Listed flexible metal conduit meeting all the following conditions:
a. The conduit is terminated in listed fittings.
b. The circuit conductors contained in the conduit are protected by overcurrent devices rated at 20 amperes or less.
c. The combined length of flexible metal conduit and flexible metallic tubing and liquidtight flexible metal conduit in the same ground-fault current path does not exceed 1.8 m (6 ft).
d. If used to connect equipment where flexibility is necessary to minimize the transmission of vibration from equipment or to provide flexibility for equipment that requires movement after installation, an equipment grounding conductor shall be installed.

I agree with you. Your summary of the rule is correct, except for the citation number from Article 250. If the ground fault current path goes through segments of FMC that have a combined length exceeding six feet, or a single length of FMC exceeding six feet, an EGC must be added.

 

[Rgraefen]

Thanks

Thanks

Thank you for your support. When possible, I like to be 100% certain with my interpretations of the code but we all know that sometimes there are opinions interjected into the text, consciously or not.
I never want to be the inspector who says "because I say so" in lieu of providing documentation to support my calls in the field.
In this particular case, while discussing the situation with the contractor, he said, "I can see I'm getting nowhere with you!" and he hung up on me. This prompted me to inquire here to guys who perform the work and take pride in their trade.
Thank you all!

 

[LarryFine]

Welcome to the forum!

I've often said that electricians and the inspector have (or should have) a common goal of a safe, compliant, and efficient electrical installation. It's nice to be able to say it to the "other side."

You're definitely on the right track by asking and by remaining civil, but you are the inspector and should never kowtow to bullying, just like you don't want to present such. You're correct here.

 

[david]

Thank you for your support. When possible, I like to be 100% certain with my interpretations of the code but we all know that sometimes there are opinions interjected into the text, consciously or not.
I never want to be the inspector who says "because I say so" in lieu of providing documentation to support my calls in the field.
In this particular case, while discussing the situation with the contractor, he said, "I can see I'm getting nowhere with you!" and he hung up on me. This prompted me to inquire here to guys who perform the work and take pride in their trade.
Thank you all!

Keep in mind from your description the last six ft whip in the chain of whips would not need a wire type equipment ground

 

[Rgraefen]

Keep in mind from your description the last six ft whip in the chain of whips would not need a wire type equipment ground

I will, thanks.