EMT Corrision Resistance

[augie47]

In Art 358.10 where it addresses EMT in concrete and in direct contact with the soil, there seems to be some "judgment" involved.
Without additional corrosion protection, how is this addressed in your area ?

 

[Dennis Alwon]

I am not sure how it is addressed here anymore. One rarely sees EMT in the soil or in concrete unless it is an old install. All the emt I have pulled out of the soil had been rusted pretty badly and in some case all the way thru the conduit.

Basically around here it is PVC or rigid, not EMT. Not sure how to vote on the poll since it isn't done.

 

[jamesoftn]

I was looking at a job and questioned the EC about using EMT in above ground slabs (poured floor mulit-story office) in a building. He produced manufactures information that this was approved in above ground slabs only.

 

[iwire]

I run into EMT in slabs but never underground unless it was DIY work.

 

[augie47]

I run into EMT in slabs but never underground unless it was DIY work.

Bob, slabs above & below grade ?

 

[Buck Parrish]

I was looking at a job and questioned the EC about using EMT in above ground slabs (poured floor mulit-story office) in a building. He produced manufactures information that this was approved in above ground slabs only.

We have done it like this for a local iniversity . It's a 5 story building. We put duct tape around the compression couplings.
Underground rust very quickly in NC. It might be okay in AZ.

 

[iwire]

Bob, slabs above & below grade ?

Not sure if I have seen it slab on grade. But I suspect that the fact many EMT fittings say 'concrete tight when taped' suggests it is OK for cement encasement.

 

[don_resqcapt19]

From the UL Guide information for Electrical Metallic Tubing (FJMX).

Galvanized steel electrical metallic tubing installed in concrete on grade or above generally requires no supplementary corrosion protection. Galvanized steel electrical metallic tubing in concrete slab below grade level may require supplementary corrosion protection.
In general, galvanized steel electrical metallic tubing in contact with soil requires supplementary corrosion protection. Where galvanized steel electrical metallic tubing without supplementary corrosion protection extends directly from concrete encasement to soil burial, severe corrosive effects are likely to occur on the metal in contact with the soil.

 

[Dennis Alwon]

I just don't see why they don't just disallow emt in the soil. There are enough other methods that are better and cheaper (PVC) then emt.

 

[augie47]

don, foolishly I didn't think to look there. Thanks

 

[Volta]

I have no idea if EMT in soil would fly here, but I hope not.

 

[benaround]

In Arizona RMC is required to be 1/2 lapped 20mil taped when in the earth.

 

[www.assuredelectric.net]

Why would you anyway? Pvc will save you more money. Labor = $ Labor is the most expensive thing on your job. Pvc is light cheap and requires 0 hardware. Emt in a slab is a bad idea. MY .02

 

[jmellc]

I worked 1 govmt job with a large co. We put EMT in poured cinder block walls. I never thought to ask then how the EMT was protected. I have seen a lot of it corroded to pieces in concrete or soil, and seen a little that took it ok. We taped couplings too. I agree that PVC is best for such, or rigid if subject to severe damage somehow.

 

[Chamuit]

We have done it like this for a local iniversity . It's a 5 story building. We put duct tape around the compression couplings.
Underground rust very quickly in NC. It might be okay in AZ.

It ain't okay here. IMC or RGC wrapped in 20mil tape as benaround mentioned.

 

[hurk27]

I been on a few demo jobs where the EMT was exposed in the demolation, and for the most part the EMT in concrete that was at or above grade barely had any corrosion, but where the concrete was below grade there wasn't much left of it, also I have notice where EMT was strapped in direct contact with concrete or block it would corrode but if it is spaced away from the block by a ?" it would do just fine, even on a wood surface where dirt can collect would cause it to rust, so we use one hole clamps (mineral-lacs) so there is a space between the building and EMT.