EMT Below Grade? 358.10(A)(1)

Status
Not open for further replies.
L

Lbartowski

Member
Location
MN
The 2017 revisions to 358.10 (A)(1) for EMT state that it could be used: "in concrete, in direct contact with the earth...."

For Healthcare construction the "redundant ground" requirement for patient care areas has always prevented the use of below grade PVC for homeruns, but can EMT be run in the dirt now? It would save us from either the large conduit home-run racks routed above ceiling, or having to use rigid if we go underground.
 
Emt has been allowed in grade depending on soil conditions for quite a while. IMO, it is not a good way to go but hey it is compliant
 
From your experience, does aluminum EMT hold up any better? It's easy to work with. The ceilings of these hospitals get so busy, that trying to do things in a "work-man like manner" makes me want to get them in the dirt.
 
Lbartowski said:
From your experience, does aluminum EMT hold up any better? It's easy to work with. The ceilings of these hospitals get so busy, that trying to do things in a "work-man like manner" makes me want to get them in the dirt.
Click to expand...

I think if you put it in the dirt you have to paint it or do something else to give it extra corrosion resistance, but I am not 100% sure.
 
EMT buried below grade

EMT buried below grade

Looking at the UL white book (2014) page 173 Electrical Metallic Tubing (FJMX) ...In general, galvanized steel EMT in contact with soil requires supplementary corrosion protection....... Aluminum EMT.........in contact with soil requires supplementary corrosion protection...
 
I live in the 2/3 of Washington state that's in the rain shadow of the Cascade mountains. It's dry here. 5 to 7 inches of total precipitation per year dry. Much, much drier than MN. If there's a place you can get away with direct bury EMT this is it. But I still wouldn't do it on one of my projects.

I've yanked EMT out that had been in the ground here for a long time. The systems it served were still functional, but the EMT was just a suggestion of conduit. It came out in many pieces.
 
There's no way in the world I would bury EMT under any circumstances, no matter how much labor is saved initially. Ok, maybe if it was in a slab deck above grade, but never in contact with the earth. :happyno:
 
Provided by the Steel Tubing Institute website -

Question: Can electrical metallic tubing (EMT) be installed outdoors?


Answer: Yes. Section 358.10(B) allows the use of EMT “in concrete, in direct contact with the earth or in areas subject to severe corrosive influences where protected by corrosion protection and judged suitable for the condition.”


The galvanizing on EMT provides corrosion protection. If necessary, supplementary corrosion protection can be added by taping or painting the tubing. Appropriate fittings must be used.
 
MasterTheNEC said:
Provided by the Steel Tubing Institute website -

Question: Can electrical metallic tubing (EMT) be installed outdoors?


Answer: Yes. Section 358.10(B) allows the use of EMT “in concrete, in direct contact with the earth or in areas subject to severe corrosive influences where protected by corrosion protection and judged suitable for the condition.”


The galvanizing on EMT provides corrosion protection. If necessary, supplementary corrosion protection can be added by taping or painting the tubing. Appropriate fittings must be used.
Click to expand...

What I often see from existing installations, even when not buried but not arranged to drain, is it will rust from inside out. Adding additional corrosion protection to the exterior will do nothing for that.
 
kwired said:
What I often see from existing installations, even when not buried but not arranged to drain, is it will rust from inside out. Adding additional corrosion protection to the exterior will do nothing for that.
Click to expand...

You do know they galvanized both inside and out right. No doubt I have seen it as well (job security), just relaying the manufactures info and current language of the NEC.
 
MasterTheNEC said:
You do know they galvanized both inside and out right. No doubt I have seen it as well (job security), just relaying the manufactures info and current language of the NEC.
Click to expand...
Yes, but also always wondered if done to same standards for both. Some brands/product lines seem to be better then others as well, not just in corrosion protection, but some bend better then others.
 
kwired said:
Yes, but also always wondered if done to same standards for both. Some brands/product lines seem to be better then others as well, not just in corrosion protection, but some bend better then others.
Click to expand...
More than likely Chinese EMT....:angel:
 
MasterTheNEC said:
More than likely Chinese EMT....:angel:
Click to expand...
This is even more common today, but has always been that way for as long as I have been in the trade, certain ones are just better to work with and seem to withstand the environment better as well. I have run a lot of EMT outdoors, condensation drainage is always something you need to think about when installing in such places with any raceway type. If you create a "trap" where condensation don't drain away, it will freeze in winter months and split your raceway open.
 
So in your opinion it's more an installation issue than a manufactures issue.

Sent from my SAMSUNG-SM-G935A using Tapatalk
 
MasterTheNEC said:
So in your opinion it's more an installation issue than a manufactures issue.

Sent from my SAMSUNG-SM-G935A using Tapatalk
Click to expand...
More like a design/selection issue. The cheapest stuff out there is supposed to still meet listing standards for the product. More expensive stuff out there possibly exceeds the minimum listing standards.
 
Lbartowski said:
The 2017 revisions to 358.10 (A)(1) for EMT state that it could be used: "in concrete, in direct contact with the earth...."

For Healthcare construction the "redundant ground" requirement for patient care areas has always prevented the use of below grade PVC for homeruns
Click to expand...

In my area we run pvc in healthcare applications underground or in the poured slab if we are above grade and pull two individual egc's in the conduit. One green and one green with a yellow tracer.
 
plumb bob said:
In my area we run pvc in healthcare applications underground or in the poured slab if we are above grade and pull two individual egc's in the conduit. One green and one green with a yellow tracer.
Click to expand...
You may get away with that, but NEC says we need a wiring method that qualifies as an EGC which means metal raceways, metallic sheathed cables... plus a wire type EGC within that method.
 
kwired said:
You may get away with that, but NEC says we need a wiring method that qualifies as an EGC which means metal raceways, metallic sheathed cables... plus a wire type EGC within that method.
Click to expand...
I agree. Personally I would just run the RMC and be done with it. Just run it to the wall and then switch over the hospital grade cable.
 
Status
Not open for further replies.
Top