Inspector wants sand around conduit

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Rodney Koop

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I have an archetect telling me that I have to surround my service entrance cables, (400 amp in conduit) with sand, due to heat factors, has anyone heard of this. thanks.
 
Inspector wants sand around conduit

I'm still waiting on details from the field. This is an underground service from the transformer pad to the building. Archetects inspector is saying that the trenches need to be backfilled with sand and not dirt due to heat factors. I think the guy is probably a nut. But like always I try to do the research before I assume that someone is off base. RK
 
Inspector wants sand around conduit

OOPs. forget it, it turned out to be he was concerned about compaction not heat disapation, we took care of the problem with a wacker packer. thanks for the interest. RK
 
Is this a government job? I have seen government work that required sand around conduit. It was a job specification. Your tax dollars at work.
 
As it was an 'Architects inspector' the requirement for sand may well have been in the job specs.

If you accepted the specs you owe them the sand.
 
You can do the calcs yourselves, but sand will typically not provide any better heat dissipation then average soil. Concrete however will, and going closer to the surface.
 
If the requirement had come from an electrical engineer, I would say that the intent was to allow the use of a higher RHO factor, in order to get a higher ampacity. See, for example, Table B.310.7. But I would also say that just putting sand around the conduits, and not replacing all the dirt within a ten mile radius with sand, would not have been enough to justify a higher ampacity. So perhaps it's good that this turned out to be a civil engineering consideration, and not an issue of ampacity.
 
Another function of the sand is that it serves as a warning in the future to DitchWitch and backhoe operators that they are getting close to a live electrical conduit.
~Peter
 
Many inspectors around me ask for "sand" in the trench. They use the term "sand" as a sort of generic term for backfill free from rocks. Much of the digging here yields a lot of rocks, which of course shouldn't be used to backfill an electrical trench. If permitted to, most of the builders and excavators would just dump them back in the trench. A typical service trench inspection here consists of trench dug, conduit installed, around 6 - 12" of sandy backfill installed and caution tape laid out (or a roll on site). Some inspectors are different, though. One inspector does 3 inspections. 1. empty trench so he can see it. 2. conduit installed without conductors. 3. trench backfilled. I was amazed at his process, but then found out he is paid per inspection.
 
I'm with J and Peter on this but I always thought it was a POCO requirement and I believed it was to protect the wire. Of the three POCO's in my area, two always backfill with 2' of sand around the conduit or direct burial cable if they are installing the service. In addition they always install the tracable buried service ribbon just above the sand just for the backhoe or ditch-witch warning (But then again, isn't that why you call for a mark-out ?). We had a situation up in a condo development a few years ago where one of the direct burial cables got nicked by a sharp rock during installation. Boy did it burn up !!!
 
300.5(F) Backfill Backfill that contains large rocks, paving materials, cinders, large or sharply angular substances, or corrosive material shall not be placed in an excavation where materials may damage raceways, cables, or other substructures or prevent adequate compaction of fill or contribute to corrosion of raceways, cables, or other substructures.
Where necessary to prevent physical damage to the raceway or cable, protection shall be provided in the form of granular or selected material, suitable running boards, suitable sleeves, or other approved means.
Click to expand...
This code section can be used to require sand or other protection for burried cables if the original earth is not suitable.
Don
 
My opinion is that concrete encasement is a much better tipoff to a backhoe operator than sand anytime. I agree the sand is usually required to keep large rocks off the conduits before compaction and therefore protecting from physical damage.
 
How about caution tape as the tip off? Though that only works if it is laid directly above the conduit. I've seen it off a few feet and excavator's dug up the line.
 
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