How To Encase Conduit In Concrete

[FOFE a.munoz]

I have a project where we changed out the service panel and we had to run the service conductors, in rigid conduit, under the house for about 5 feet before they were terminated in the panel. The city inspector is requiring that we encase the conduit in at least 2" of concrete for the 5 feet of conduit that is under the house.

We've never been required to do this before, but the inspector won't pass us unless we do it. I'm totally at a loss as to how we'd go about getting 2" of concrete to encase the conduit.

Have any of you had experience in encasing conduit in concrete?

 

[kwired]

Build a frame of some sort around the conduit and fill it with concrete. The "form" only needs enough strength/durability to hold the concrete long enough to set. Only encasing 5 feet will only need maybe two or three bags of ready to mix concrete from a building supply store at the most, probably less then $20 plus whatever you use to form it with for materials.

If it is a horizontal run but not on grade, forming it may become a little challenging. If it is strapped directly to floor joists it gets somewhat easier, but becomes impossible to get 2 inches of concrete on top side at each floor joist so you will likely need to re-route the conduit to gain that clearance.

If you can't figure it out get a contractor that does concrete work to do it for you.

My guess is he wants at least 2 inches of concrete totally encircling the raceway in question when it is completed - that is the general thickness needed to consider the raceway to be technically considered "outside of the building"

 

[steve66]

I believe 230.6 would be the reference. I assume the conduit is not under 18" of dirt as allowed in one of the subparagraphs.

Even if its not 18" deep, 5' seems like a really short distance to worry about. I've heard many jurisdictions adopt a 10' rule, where the service conductors can run 10' inside the building before hitting the disconnect. In fact, I believe so many areas have adopted this distance that many people think that's the official NEC rule.

Anyhow, 230.6 just says it has to be under 2" of concrete, so I don't think you need any concrete under the conduit. I'm not a contractor, but if its in an unfinished crawl, and if it were me, I'd just take 2" of dirt off the top of the conduit, and replace with concrete. I wouldn't bother forming anything.

 

[kwired]

I believe 230.6 would be the reference. I assume the conduit is not under 18" of dirt as allowed in one of the subparagraphs.

Even if its not 18" deep, 5' seems like a really short distance to worry about. I've heard many jurisdictions adopt a 10' rule, where the service conductors can run 10' inside the building before hitting the disconnect. In fact, I believe so many areas have adopted this distance that many people think that's the official NEC rule.

Anyhow, 230.6 just says it has to be under 2" of concrete, so I don't think you need any concrete under the conduit. I'm not a contractor, but if its in an unfinished crawl, and if it were me, I'd just take 2" of dirt off the top of the conduit, and replace with concrete. I wouldn't bother forming anything.

OP did not give any details of exactly how this service raceway was run within the crawlspace. We once had a building with about 4 feet of crawlspace under it, and of course service came up into a central room in the building. Here we can only have 5 feet of service conductor within the building before hitting the service disconnect. On that one we encased a vertical section of raceway within the crawlspace and had less then 5 feet of non encased raceway that started just below the the floor and run into the service disconnect which was a main breaker panel with bottom feed main breaker, so only maybe 4 feet of service conductor was technically inside the building.

Also done a commercial garage or two (before they added definitions for major and minor repair garages) where we encased underground PVC service raceway up to 18" above the floor to get it "outside the building" and outside the classified area that ends 18" above the floor.

 

[drcampbell]

The Odjob (not a typo) mini-mixer is perfect for small jobs like this. No need to call in a concrete subcontractor.



http://www.scepterconsumer.com/sites/scepter_consumer_02/files/Scepter_Catalogue_2014.pdf , page 15 (page 27)

 

[kwired]

The Odjob (not a typo) mini-mixer is perfect for small jobs like this. No need to call in a concrete subcontractor.

View attachment 17851

http://www.scepterconsumer.com/sites/scepter_consumer_02/files/Scepter_Catalogue_2014.pdf , page 15 (page 27)

Wheelbarrow and simple gardening tools work great as well, and many times you may already have those.

Don't try to mix more then one premixed bag at a time, it gets much more difficult to get good consistency. Too watered down mixes easier but doesn't make as good of concrete.

 

[petersonra]

I don't recall what the actual rule is but if it only has to be under 2 inches of concrete why not just leave the conduit buried as it is and put a 2 inch concrete block over top of it.

 

[ptonsparky]

Bags of sackcrete laid over the conduit. Might be hard to do if nailed to the underside of a the floor joist.

 

[GoldDigger]

I don't recall what the actual rule is but if it only has to be under 2 inches of concrete why not just leave the conduit buried as it is and put a 2 inch concrete block over top of it.

I don't think that concrete blocks count. Unless they are solid and continuous without seam for the length of the pipe.

 

[petersonra]

I don't think that concrete blocks count. Unless they are solid and continuous without seam for the length of the pipe.

Where does it say that in the code?

 

[GoldDigger]

Where does it say that in the code?

It doesn't.
But I am willing to bet a substantial amount of money that an inspector will not count the air space in a hollow core block as part of the 2".
Nor will he agree that the open space between blocks, even if just a small crack, constitutes a concrete covering at that point.

There is a general implication in English usage that covered in concrete and covered with concrete blocks are not synonymous.

 

[petersonra]

It doesn't.
But I am willing to bet a substantial amount of money that an inspector will not count the air space in a hollow core block as part of the 2".
Nor will he agree that the open space between blocks, even if just a small crack, constitutes a concrete covering at that point.

There is a general implication in English usage that covered in concrete and covered with concrete blocks are not synonymous.

personally I was not thinking of a concrete block that was Hollow but even so a hollow concrete block on its side has at least two inches of concrete even though it's got a hollow in the center. I had more in my mind the solid concrete blocks that are like 3 inches thick you could lay them on edge over top of the conduit you would certainly get 3 inches of coverage that way. If there's a claim that there's no coverage where the ends of the block are you could just put another block there. Or you can mix up a little grout and grout the blocks together.

 

[truck41trouble]

This entire thread is the reason I try to install a service disconnect on any new construction I do.

Sent from my VS987 using Tapatalk

 

[adnj]

Have any of you had experience in encasing conduit in concrete?

Unfortunately, I have.

If the conduit is a straight run that is on the ground:
- Elevate the conduit so that it is at least 2" off the ground using small pieces of concrete block.
- Use planking or plywood to to form the sides by securing the form with stakes driven into the ground about every foot.
- nail some straps across the top of the form work every foot or so.

Pour your concrete and let it set for three days and then remove the form work.

If the conduit is elevated then you will need to build a gutter with a bottom and two sides that is supported below the conduit.

If the conduit runs vertically, you will need to build a column form with four sides and pour the concrete from the top.

You can mix with a garden hoe and a tub or wheelbarrow. You can mix on a concrete floor with a shovel, too (but that can be tricky).

Concrete weighs about 150 lbs per cubic foot. You may need about 4 cubic feet. Keep that in mind when you're planning your form work.

Good luck.

 

[steve66]

I don't recall what the actual rule is but if it only has to be under 2 inches of concrete why not just leave the conduit buried as it is and put a 2 inch concrete block over top of it.

If the concrete block is just laid on top of the conduit, I would object to it not being permanent. Nothing to stop the home owner from saying "what the heck is this here for?", and removing it.

 

[petersonra]

If the concrete block is just laid on top of the conduit, I would object to it not being permanent. Nothing to stop the home owner from saying "what the heck is this here for?", and removing it.

where is that requirement in the code?

 

[drcampbell]

Wheelbarrow and simple gardening tools work great as well, and many times you may already have those. ...

The Odjob mixer fits in the truck a lot more easily than a wheelbarrow.

 

[kwired]

The Odjob mixer fits in the truck a lot more easily than a wheelbarrow.

Probably does. If I wanted to mix some concrete today, I already have the wheelbarrow

 

[petersonra]

Probably does. If I wanted to mix some concrete today, I already have the wheelbarrow

can you still buy cement in a can?

 

[kwired]

can you still buy cement in a can?

I always buy PVC cement in a can.