Building over underground primary

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Montanaboy

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My client's project proposed to build a cafeteria on concrete piers over 13.8kV underground primary. The client is primary metered and the utility wants nothing to do with this (work, materials, labor, liability, etc.).

Common-sense wise, it doesn't seem like the best idea, but I'm sure it is done all over in large cities where space is a premium. Code wise, I only see NEC table 300.50 as a guide. Any experience with this or guidance?
 
Certainly it's done all the time. Just don't dig into it and there are no issues. If this was my work, however, I'd want to put that primary in pipe at least for teh section under the new building just so I don't screw myself down the road 20 years when it starts to go bad.
 
the relevant questions are
1) does the utility have a right of way, or require the right of way to gain access to their equipment
2) should the utility line be moved as a portion of the project (and for what reasons)

if the above doesn't apply, then I suppose it will fly
 
Montanaboy said:
Any experience with this or guidance?
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I would be a better choice to relocate the feeder if room is available on the property.If something happens during construction or later on, you'll have to relocate it anyway.This would be a good time to install a pad mount switch and transformer to feed the new cafeteria and relocate the feeder and any other underground utilities.
Rick
 
chris kennedy said:
I'll see your 300.5(C) and raise you a 90.2(B)(5).:smile:
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Re-raise with NESC 2007-351C2 (Buildings and Other Structures)

"Cables should not be installed directly under the foundations of buildings or other structures. Where a cable must be installed under such a structure, the foundation shall be suitably supported to limit the likelihood of transfer of a detrimental load onto the cable."
 
I am not sure where the problem lies.

13,800V is installed in/under buildings pretty regular around here. I am sure some extra precautions may be taken for the school, but I would not be too worried.

How high will the piers be over the grade? How deep do they plan on installing the 13,800V below grade?


The issue I could see that may arise and be a problem, would be if someone took Gauss meter readings. Some parents could get real agitated if the readings were high enough.
 
Pierre C Belarge said:
The issue I could see that may arise and be a problem, would be if someone took Gauss meter readings. Some parents could get real agitated if the readings were high enough.
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I suspect you will get more from the stuff in the building (unless the neutral was corroded away).
 
Mincing Words

Mincing Words

I re-reviewed NEC 300.50. The wording is uses is that underground cables shall be installed in accordance with 300.50(A)(1) or (A)(2), etc.

This addresses when you are installing an underground circuit, not when you are placing a building on top of an existing underground circuit.

Is does this seem like a loop-hole? Is there another section of the code (outside of NEC 300.50 or NESC 351-C2) that might address this?
 
You said it was primary metered but who actually owns the cable? The meter point does not necessary serve as the demarcation point.
 
Montanaboy said:
The client owns the cable 100%.
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Which explains why
the utility wants nothing to do with this (work, materials, labor, liability, etc.).
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I just don't see a major problem with it. I might be inclined to suggest it should be installed so it can be more easily replaced or repaired later, if needed, but that is solely a design consideration.

Since you are building over top of it, it seems possible that you might be able to accommodate future access in some way. Maybe slide a big pvc pipe around it. Or maybe some kind of crawl space.
 
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Which came first?

Which came first?

What do you think about the wording of "Building over primary" versus "installing primary under a building"? Does it matter? Probably not, but NEC is specific to installation under a building and not building over an installation.
 
Montanaboy said:
What do you think about the wording of "Building over primary" versus "installing primary under a building"? Does it matter? Probably not, but NEC is specific to installation under a building and not building over an installation.
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I would guess in most such installations the cable is installed first and then the building built over top of it. A whole lot easier that way.
 
Montanaboy said:
What do you think about the wording of "Building over primary" versus "installing primary under a building"? Does it matter? Probably not, but NEC is specific to installation under a building and not building over an installation.
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I don't agree. I don't see anything in the code that specifies the order of construction. It is under the building in either case.
 
300.5(C) Underground Cables Under Buildings. Underground
cable installed under a building shall be in a raceway that is
extended beyond the outside walls of the building.
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I don't see how you get around putting it in a raceway. Presumably, a crawl space of some sort would be part of, and thus not under the building.
 
petersonra said:
I don't see how you get around putting it in a raceway. Presumably, a crawl space of some sort would be part of, and thus not under the building.
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Please refer to NEC 300.50, not 300.5
 
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