Unmetered secondary depth

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POWER_PIG

POWER_PIG

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Hi ya'll!
Any of you guys ever heard of burying secondary feeders (in pvc) 36" deep?
I know of installs where we are contracted to install the utility conduit say for a underground lateral to a house that has to be that deep as per the POCO specs, but this particiular situation is a commercial job and the secondary lats. have nothing to do with the local power co. it's all customer owned. Only thing I can find in the code is the chart in table 300.5.... I say it only has to be 18" of cover unless under a parking lot in which it would be 24".
Am I mistaken here? Thanks everyone!
 
Yes sir I agree that deeper is better in most cases, just saying for the sake of argument that table 300.5 is the NEC minimum requirement.
 
Deeper not always better

Deeper not always better

From a safety standpoint, deeper can be better. 42" of cover for utility primary lines is common. If you can afford to go with 36" cover, use it. Remember that a 36" deep trench is not the same as 36" cover.

However, thermal performance for large feeders that are heavily loaded is worse at greater depths. You are saved if the water table is higher. In dry soil, closer to the surface provides better heat dissipation.
 
We keep it uniform be requiring a 36" deep trench for both primary and secondary conductors. We also random lay with both telephone and CATV. The end result is 30" of cover for the primary conductors and 24" for the secondary (the primary goes into the trench first). We are also covered by the NESC and not the NEC but the depth requirements are the same for direct burial (cable in conduit is a different matter and not part of this response). :)
 
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