EMT in concrete?

[ih8shorts]

2005 NEC, EMT, Uses permitted, 358.10(B)"EMT shall be permitted to be installed in concrete".
358.12(3) EMT, Uses not permitted, 358.12(3)"In cinder concrete or cinder fill".
1) What is "cinder"concrete? 2) If I install EMT in concrete can I use EMT where the conduit stubs up from the concrete. 3) Does the code require the use of raintight connectors or can I just use set screw connectors on the EMT thats in the concrete? Thanks.

 

[tom baker]

Re: EMT in concrete?

EMT does not hold up well in concrete. Fittings have to be listed concrete tight. The conduit will "rot" where it comes out of the slab. In Washington State we can not install EMT in concrete on or below grade.

 

[esox39]

Re: EMT in concrete?

1) "cinder concrete" and "cinder fill" is made from the by-product of steel mills. This is found is areas around steel mills such as the Chicago and Northwest Indiana area. It has a high steel content which causes galvanic action and eats the pipe away very quickly.
2) Yes, emt can emerge from concrete.
3) Most set screw and compression fittings are UL Listed concrete tight. Check with the manufacturers spec. It might say "Concrete tight when Taped". Then use duct tape around the fitting and your good to go.

 

[sceepe]

Re: EMT in concrete?

Try painting the conduit with "asphaltum" before the slab is poured.

 

[slipknotbmg]

Re: EMT in concrete?

3) Most set screw and compression fittings are UL Listed concrete tight.

Does anyone else remember a Mike Holt newsletter saying that even emt compression fittings are not UL listed for wet locations? I keep thinking it said something about only 1 manufacturer in the U.S. made listed compression fittings for wet locations, and they had a sealing ring in them. I would think concrete would be considered a wet location while curing.

 

[ryan_618]

Re: EMT in concrete?

Slipknot: Yes, the UL standard for wet location fittings was revised, however, most manufacturer's make fittings that are listed now. For quite some time there was only one, and I beleive it was bridgeport.

 

[roger]

Re: EMT in concrete?

There are 5 manufacturers in compliance now

Roger

 

[russ]

Re: EMT in concrete?

Set screw couplings are concrete tight if you tape them. Bridgeport I know only has concrete tight on there boxes. But I believe this is a miss labeling, that I asked UL to look into. Iv 'e been told (haven't seen it myself) Steel City also has the same thing on their boxes and that is being looked into also.

 

[jimwalker]

Re: EMT in concrete?

I thought emt was not allowed in concrete.
Why would anyone use emt in concrete

 

[russ]

Re: EMT in concrete?

Its common to use EMT in high rises. First the metal deck is installed with reinforsment wire, then conduit is installed, before a four inch or deeper concrete floor is poured.

[ December 09, 2004, 07:00 PM: Message edited by: russ ]

 

[russ]

Re: EMT in concrete?

It's also used in low rise building with flexicore (spelling?) floors.

[ December 09, 2004, 07:03 PM: Message edited by: russ ]

 

[jimwalker]

Re: EMT in concrete?

ok i guess i missed something.I thought emt could no longer be in concrete

 

[russ]

Re: EMT in concrete?

UL web site.

Electrical Metallic Tubing


Guide Information for Electrical Equipment for Use in Ordinary Locations

GENERAL
This category covers electrical metallic tubing manufactured in trade sizes 3/8 to 4 (metric designators 12 to 103) inclusive for installation of conductors in circuits rated above or below 600 V, nominal, and in accordance with ANSI/NFPA 70, "National Electrical Code."

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.

Aluminum electrical metallic tubing used in concrete or in contact with soil requires supplementary corrosion protection.

UNEVALUATED FACTORS
Supplementary nonmetallic coatings presently used have not been investigated for resistance to corrosion.

ADDITIONAL INFORMATION
For additional information, see Electrical Equipment for Use in Ordinary Locations (AALZ).

[ December 09, 2004, 07:28 PM: Message edited by: russ ]

 

[iggy2]

Re: EMT in concrete?

"I would think concrete would be considered a wet location while curing."

But it's not a wet location once the slab cures, which is probably when conductors are installed.

 

[hank1]

Re: EMT in concrete?

My last resort would be to install emt in concrete, my 2nd to the last would be rigid. I have seen both rusted, and filled with mud, and corrosion after a number of years. I have seen both just rusted away at the exit point. UL might say OK, and that's fine, but I'm thinking about down the road. If posssible, depending in the application I run PVC.

Hank

 

[royta]

Re: EMT in concrete?



Edited to remove my post. I mentioned the use of RMC or IMC in fuel stations, due to an EYA or EYS needed at each end of the conduit run.

[ December 14, 2004, 11:59 AM: Message edited by: royta ]

 

[George Stolz]

Re: EMT in concrete?

Originally posted by hank1:
My last resort would be to install emt in concrete, my 2nd to the last would be rigid. I have seen both rusted, and filled with mud, and corrosion after a number of years. I have seen both just rusted away at the exit point. UL might say OK, and that's fine, but I'm thinking about down the road. If posssible, depending in the application I run PVC.

How icky would it look to run PVC to a few inches above ground, then switch to EMT? That would still be legal, wouldn't it?