Flexible Metal Conduit

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edomurat

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I have a question about flexible metal conduit. After searching the Code, I think there is a restriction on using 3/8" flex metal conduit (most applications) to a limit of 6 feet. With additional searching, I don't see this 6 foot limitation when using MC metal-clad cable. Since the two seem so similar (MC vs. Flex with drawn through conductors), why does the code restrict the length of one but not the other?

Appreciate any help and thanks.
 
They may seem similar, but they are not. Articles 330 and 348 list uses permitted vs not permitted for each type. There's a reason flex and MC each have their own articles and rules, and I'm sure there's a reason 3/8" flex is limited to 6'.

But when you get right down to it, it doesn't matter what the reasons are. The AHJ enforces the rules, and my experience is that they only allow exceptions rarely and in very narrow circumstances where there's a good reason for the exception.
 
I`ve always been under the assumtion that the 6 ft rule applied to free whips of these items.As long as installed and secured within the applicable codes they are in essence a conduit system.A 6 ft. rule allowed them to be that long as long as they are installed within the allowed guide lines for the particular system
 
Why is 3/8 FMC limited to 6'? I don't know. There is a limitation of 6' for any size FMC when used as an EGC. I don't know what the cross sectional area of 3/8" FMC is but I would venture a guess that pulling circuit conductors into a long run of it would violate the 40% fill rule.
 
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