Question about Flexible Metal Conduit

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JJWalecka

JJWalecka

Senior Member
Location
New England
It states in 348.20 Size.
(A) Minimum FMC less than metric designator 16 (trade size 1/2) shall not be used unless permitted in 348.20(A)(1) through (5) for metric designator 12 (trade size 3/8)
(1) For enclosing the leads of motors as permitted in 430.145(B0
(2) In lengths not in excess of 1.8 m (6 ft)for any of the following uses:
a. For utilization equipment
b. As part of a listed assembly
c. For tap conductors to luminaries (lighting fixtures) as permited in 410.67(C)
(3) For manufactured wiring systems as permitted in 604.6(A)
(4) In hoist ways as permitted in 620.21(A)(1)
(5) As part of a listed assembly to connect wired luminaire (fixture) sections as permitted in 410.77(C)

Does it mean in (2c) "as part of a listed assembly" when you change from EMT to FMC using a change over fitting. I personally think that flex instead of EMT to FMC looks like crap. Though FMC does sometimes have its advantages for short runs. I have seen flex installed out of wire ways for thirty or forty feet instead of EMT changing to FMC. Is this legal. I am aware that over 6 ft a equipment grounding conductor must be installed. I personally don't trust any raceway as the equipment ground in itself. Thank you for your time in the misunderstanding of the wording used.

Justin
 
Re: Question about Flexible Metal Conduit

Article 348.20 (A) is stating that you must use half inch flex or larger, unless the 5 exceptions apply. 358.20 (A)(2)(c) is refering to 6" pre-assembled fixture whips. It is legal to change from EMT to FMC, in most applications. The 360 degree bending radius rule still applies.
 
Re: Question about Flexible Metal Conduit

I don't have my code book here so I'm working from
memory, but I think the 6' eq. grd. rule in flex
applies only to 20 amps or less. I'll check my aging memory at the office monday a.m. EMT can
also be used as your sole eq. grd. but who can watch every helper and tighten every locknut.
There is something to be said for "good ground"!!
Always Pull The Green Wire!!!!!!!
 
Re: Question about Flexible Metal Conduit

The above posted section is only an allowance to allow the use of FMC in a size smaller than ?"
For grounding requirments you need to read 250.118 (5), (6), and (8) for which type and size FMC that can be used for grounding.
 
Re: Question about Flexible Metal Conduit

That is absolutely correct. The code listed above has nothing to do with grounding.
 
Re: Question about Flexible Metal Conduit

Thank you Sparkslord, Magicdog and Hurk27. You can install FMC at any length(though I think it looks like crap) as long as you meet the requirments of 348.10 Uses permitted and 348.12 Uses not permitted. Thank you.


Justin
 
Re: Question about Flexible Metal Conduit

A good thing to remember with emt is that if you are only pulling a grounding conductor because of the possibility of loose set screws, you may be in trouble. What happens if a fault occurs in the raceway, how will it trip the breaker if it has a poor path to ground?
 
Re: Question about Flexible Metal Conduit

dnbob and hurk27 thank you. You are right about the loose fittings. I try to remember to tighten all fitting either set screw or compression. Thanks again.

Justin
 
Re: Question about Flexible Metal Conduit

dnbob and hurk27 thank you. You are right about the loose fittings. I try to remember to tighten all fitting either set screw or compression. Thanks again.

Justin
 
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