"Stacked Raceways"

[augie47]

When multiple conduits are laid in a ditch how is "required" spacing determined.
Appendix B can be applied under engineering supervision and 310.15(B)(2)(b) states "Spacing between conduits..or raceway shall be maintained"

Another inspector asked me today about a trench which had (7) 4" conduits installed with (4) on the bottom and (3) laid on top of the (4)...no spacing...
Without going to Appendix B, does derating apply and if so, what spacing would be required without derating

 

[Cow]

Our inspector calls us on this. Of course, there is no recommended spacing. We always joke about sliding toothpicks between the conduits and then calling for reinspection.:roll:

We usually just slide small pieces of pvc between the conduits every so often. I wish they had a table for spacing for different size conduits, circuit size, whatever, instead of one big gray area with no hard and fast guidelines.

 

[chris kennedy]

Is this a 300.5 install, or a 300.50 install? If 300.5, I know of no spacing requirements other than the utility providers.

 

[augie47]

Is this a 300.5 install, or a 300.50 install? If 300.5, I know of no spacing requirements other than the utility providers.

300.5 and customer owned conductors.
300.15(B0(2)(b) is the only reference I can locate.

 

[chris kennedy]

300.5 and customer owned conductors.
300.15(B0(2)(b) is the only reference I can locate.

Even if the raceways look like they are touching each other, likely there is at least one atom of something else between them. Therefore I am maintaining a spacing of one atom.

 

[bluesmoke...oops]

Therefore I am maintaining a spacing of one atom.

And really atoms are mostly empty space right? So you have tons of room!

 

[cowboyjwc]

And really atoms are mostly empty space right? So you have tons of room!

I don't require any spacing. Someone told me I was wrong the other day and showed me in the code. I then pointed out that if he was running 600v to his building he was going to do a whole bunch of damge to his 120/240v equipment.