Sleeving through a foundation

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MNSparky

MNSparky

Senior Member
Location
Minneapolis, MN
Occupation
Electrical Contractor - 2023 NEC
Hi everyone,

I'm bidding on two very similar projects where they are adding onto a storage building. In both projects there are underground electrical lines passing through where the new foundations will be poured and it is in the EC's scope to deal with them. Project A has direct buried triplex and Project B has buried PVC conduit. Not sure how deep either is.

I've never had to deal with this so I'm looking for wisdom from those of you who have! What's the best way to do it? I'm assuming I'll need to dig them up and either disconnect & pull back or protect in place. I'd rather leave in place and protect which would involve some kind of 2 piece sleeve through the foundation.

My thoughts as of right now are shut them down, dig down to them where the foundation will cross them and expose them for the excavator. I will make sleeves out of PVC pipe split lengthwise and duct tape/pipe clamp them closed around the wires so the foundation can be poured over it.

Any other thoughts would be greatly appreciated! Thanks!
 
It seems to me that it is up to the concrete guy to figure this out. I sort of like the idea of just boxing around them where they pass under/through the new foundation if the structural engineer approves.
 
I have no experience, but I like your idea. Have you considered a non-perforated corrugated yard drainage pipe. It's very easy to cut long ways and snap it around the cable. Comes in 100 foot rolls, it's cheap, and big enough to allow someone to pull the cable out in the future without ripping up the foundation.
 
petersonra said:
It seems to me that it is up to the concrete guy to figure this out. I sort of like the idea of just boxing around them where they pass under/through the new foundation if the structural engineer approves.
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I also prefer that method. I'm checking with the architect/engineer to see if it's permissible. The plans call for me to disconnect and reroute but that would be a nightmare as I'd have to go all the way around the building.
 
GoldDigger said:
I suspect he means to terminate the cable in a box on both sides of the foundation footprint and pull/sleeve new wires between those points.
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Gotcha, I thought about that and there are several issues. The cable at project A is actually a service lateral. Project B is proposed to be paved all the way around so an in-ground box probably won't work unless I spec a concrete one (subject to vehicle traffic) and a wall mounted box will probably not be approved due to aesthetics. I'd really rather not bring them to the surface if I don't have to.
 
GoldDigger said:
I suspect he means to terminate the cable in a box on both sides of the foundation footprint and pull/sleeve new wires between those points.
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Mmmmm, "box out" means to create a void space, usually square or rectangular, such that when the foundation walls are poured there will be a clear space communicating from outside to inside. It's done in the formwork.

Boxing out is usually done when there is uncertainty regarding the number, size, and type of penetrations required. Otherwise, it's better to place sleeves as required and pour around them.
 
tom baker said:
Split duct is available. Splitting the pvc may alllow dirt, water, mud inside your conduit.
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I wouldn't be breaking the conduit, just providing a sleeve around it through the new foundation wall. The split duct is nice to know about though, I didn't know it existed.
 
Remembering and finding are two different things for me, but I seem to remember that service entrance conductors can't be run under a building. This may be a POCO rule which is why I dont' see it in 230. For your service lateral it would be wise to check with them on this
 
synchro said:
As Tom said there is split duct and conduit such as this:

https://conduitrepair.com/product/split-conduit/
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Here is the advantage the unique interlocking design of Split Conduit creates a smooth tight seal protecting the cable or fiber optics from weathering. No tape, plastic, or metallic straps are needed to seal or provide extra strength to the Split Conduit.
 
tom baker said:
Remembering and finding are two different things for me, but I seem to remember that service entrance conductors can't be run under a building. This may be a POCO rule which is why I dont' see it in 230. For your service lateral it would be wise to check with them on this
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It’s considered outside the building, so code doesn’t prohibit it, but the poco can.
 
hillbilly1 said:
It’s considered outside the building, so code doesn’t prohibit it, but the poco can.
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It's not an issue here, this particular service lateral actually already passes under about half of the building it feeds which is the same building the addition is going on. Here the customer actually owns and installs the everything on the secondary side of the poco transformer for commercial and industrial installations.
 
The reason for doing this is to allow the existing cables to be replaced if there is a problem, That means being able to pull out the damaged cable and pull in a new one. This is the concept. ( Or could be a theory in the real world, that is pulling out the damaged cable and pulling a new cable ) One option might include installing spare empty conduits ? Other wise pouring the new foundation over these existing conduits would never allow that. This is why we have electrical engineers. They are paid to address problems like this and provide practical detailed solutions. In my opinion the practical solution depends on the number of conduits involved. Concrete box out is practical and as is protective sleeves. What ever method SHALL and must be used should be a coordinated solution with owner and or engineering approval. Just what I think.
 
JEFF MILLAR said:
The reason for doing this is to allow the existing cables to be replaced if there is a problem, That means being able to pull out the damaged cable and pull in a new one. This is the concept. ( Or could be a theory in the real world, that is pulling out the damaged cable and pulling a new cable ) One option might include installing spare empty conduits ? Other wise pouring the new foundation over these existing conduits would never allow that. This is why we have electrical engineers. They are paid to address problems like this and provide practical detailed solutions. In my opinion the practical solution depends on the number of conduits involved. Concrete box out is practical and as is protective sleeves. What ever method SHALL and must be used should be a coordinated solution with owner and or engineering approval. Just what I think.
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Agreed, I've already reached out to the architect/engineer for approval. The service lateral may be in conduit for all I know, I haven't dug it up yet. It's just common around here to direct bury triplex and quadplex for services so that's what I'm guessing it is. The split duct would be a good solution if it is direct buried to allow for future replacement.
 
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