# Use of 3/8" FMC in dwelling



## Southeast Power (Jan 18, 2009)

I took over a remodel and found the person before me used 3/8 FMC as a wiring method.
They kinda used it as MC in some places. With that, I mean that they have more than 360 deg of bends.
I have never concealed 3/8 and considered using it as a "raceway" with the same limitations as EMT would have.

Question:
Can 3/8 FMC be concealed with the 360 deg limitations and used like this or does it have to come out and be replaced with MC?


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## drumnut08 (Sep 23, 2012)

jrannis said:


> I took over a remodel and found the person before me used 3/8 FMC as a wiring method.
> They kinda used it as MC in some places. With that, I mean that they have more than 360 deg of bends.
> I have never concealed 3/8 and considered using it as a "raceway" with the same limitations as EMT would have.
> 
> ...


Chances are , you've already got 3 to 4 # 14's , 12's , or 10's in the flex now , which doesn't lend itself to adding new circuits down the line anyway . If it were 1/2" or 3/4" , you could pretty easily change things down the line , if you wanted . I wouldn't rip anything out unless the AHJ made me . Most of the inspectors I see around here would think it was mc anyway and not think twice about it .


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## Southeast Power (Jan 18, 2009)

Inspection this morning


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## BBQ (Nov 16, 2010)

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 (A)(5) for metric designator 12 (trade size 3⁄8).

(1) For enclosing the leads of motors as permitted in 430.245(B)

(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 connections to luminaires as permitted in 410.117(C)

(3) For manufactured wiring systems as permitted in 604.6(A)

(4) In hoistways as permitted in 620.21(A)(1)

(5) As part of a listed assembly to connect wired luminaire sections as permitted in 410.137(C)


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## HackWork (Oct 2, 2009)

I've used it to sleeve romex for protection. I assume 348.20 doesn't apply if used as a sleeve. But now that I think about it, 3/8" is probably too small for the romex.


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## ponyboy (Nov 18, 2012)

HackWork said:


> I've used it to sleeve romex for protection. I assume 348.20 doesn't apply if used as a sleeve. But now that I think about it, 3/8" is probably too small for the romex.


I think it is too small for romex. The table in 348.22 only lists single conductors.


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## MHElectric (Oct 14, 2011)

The only place I ever used 3/8" flex was controls for HVAC. It would have never crossed my mind to use it on anything more than motors & control devices.

My old boss used to tell us that a roll of 3/8" flex was more expensive than 1/2". I don't know if thats true or not, but we tried to use 1/2" as much as we could.


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## Southeast Power (Jan 18, 2009)

Complete fail. :laughing:

the last guy stripped Romeo and installed in in the 3/8" FMC. this also included the bare ground.
Inspector called it out.
I thought green or bare was acceptable, not that it mattered.

He wants arc faults in the existing panel.


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## MTW (Aug 28, 2013)

I ignore the code rules that apply to 3/8" FMC and do what I want.


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## Southeast Power (Jan 18, 2009)

MTW said:


> I ignore the code rules that apply to 3/8" FMC and do what I want.


We're you on vacation in Florida this summer?


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## MTW (Aug 28, 2013)

jrannis said:


> We're you on vacation in Florida this summer?


As a matter of fact, I was there back in June. :thumbup:


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## manchestersparky (Mar 25, 2007)

jrannis said:


> Complete fail. :laughing:
> 
> the last guy stripped Romeo and installed in in the 3/8" FMC. this also included the bare ground.
> Inspector called it out.
> ...


The issue is not with the insulated vs bare ground wire. The issue is NEC 310.11.
The conductors inside romex are not marked thus they can not be stripped out of the NM jacket and used as separate conductors.


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## Southeast Power (Jan 18, 2009)

manchestersparky said:


> The issue is not with the insulated vs bare ground wire. The issue is NEC 310.11.
> The conductors inside romex are not marked thus they can not be stripped out of the NM jacket and used as separate conductors.


He said that if he knew they were from Romex he would accept it but wanted an insulated ground.


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## Celtic (Nov 19, 2007)

manchestersparky said:


> The issue is NEC 310.11.


310.120 in 2011 :thumbsup:


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## manchestersparky (Mar 25, 2007)

Celtic said:


> 310.120 in 2011 :thumbsup:


Thanks for the correction:thumbsup:
I was posting from the laptop in the car at work. Only had the 2008 with me as that's the cycle we're still on!


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## MTW (Aug 28, 2013)

If the code says I can run 3/8" FMC only 6 feet, I run it 6.000000000000000000000001 feet just to spite the NEC.


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