FMC allowed to penetrate concrete?

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elecshop

Member
Location
FL, USA
Occupation
Electrical Engineer
According to 348.12(6) FMC shall not be used underground or 'embedded' in poured concrete or aggregate.
Does this translate into FMC not being allowed to penetrate concrete?

Assume after penetrating it runs horizontally under the concrete slab then penetrates upward. Sealing and concrete slab infill will be provided after. I assume this is not allowed by code?
 
E

elecshop

Member
Location
FL, USA
Occupation
Electrical Engineer
That concrete slab which the FMC pokes through is on a second floor and open to the exterior (lower level is smaller in area than the second floor). So that FMC, not allowed to be exposed, will be run horizontally under the slab and there will be concrete infill to cover it. Is this allowed?
 
J

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
It would not be allowed anywhere there is going to be more concrete poured around it, which seems to be what you're describing.

If it's just an issue for a few inches, one could install EMT in that location and use a transition coupler to change to FMC for the rest of the run.
 
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Eddie702

Licensed Electrician
Location
Western Massachusetts
Occupation
Electrician
You can run it through existing poured concrete after drilling a hole but can't pour concrete around it. There may be protection requirements if coming up through a floor in an exposed location.
 
JoeStillman

JoeStillman

Senior Member
Location
West Chester, PA
Is this a furniture feed? I would put RMC in the poured concrete, to a concrete floor box, then transition to FMC coming out of the box. But if it's existing construction, you could do the same thing with RMC or EMT in the soffit and core a hole big enough for a poke-through box.
 
E

elecshop

Member
Location
FL, USA
Occupation
Electrical Engineer
JoeStillman said:
Is this a furniture feed?
Click to expand...
Yes.

It is an existing soffit that the FMC will penetrate through a hole. Will it be allowed to continue with FMC along the soffit if there will be a new concrete trench around it? (concrete "corridor" to pass the FMC a couple of feet then up to the feed, i.e., not pouring concrete around it) but I'm not sure how much it can withstand temperature in this little trench with concrete around it.

Maybe the answer is no I have to use EMT in that trench then transition up to FMC after poking the floor again to enter the new feed? I'm just trying to understand the implications of the code sentence "embedded in concrete".
 
J

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
"Embedded in concrete" to me means that you are pouring concrete directly around the raceway. If you build concrete forms to keep the concrete off the raceway somehow that would be code compliant for FMC. That said, such an approach seems like extra work and prone to error compared to using EMT, if there's going to be concrete in the near vicinity.
 
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