Isolated Conduit in Air

[roger]

Isolated Conduit in Air

What does "Isolated Conduit in Air" mean as used in 310.73 thru 310.76.

In a 12470v installation where XLP 15kv shielded conductors (MV-105) are used for assorted feeders inside a facility, and are run in RMC, what table or section for ampacity is used?

Are conduits inside a building "Isolated in Air", or are they just conduits on supports?

If these conductors are not in duct banks, and there is something special about "Conduits Isolated in Air", then there is no specific table for an installation of 2001v and higher conductors run in conduit inside a building.

Considering this, how would the ampacity of a given conductor be figured except under engineering supervision?

Roger

 

[steve66]

Re: Isolated Conduit in Air

Re: Isolated Conduit in Air

They are definately not conductors in a duct bank. That is defined in 310.60 as embeded in earth or concrete.

I take the lack of any other table to mean these would be considered in free air.

Hopefully, someone else will know for sure.

Steve

 

[charlie b]

Re: Isolated Conduit in Air

Re: Isolated Conduit in Air

Originally posted by roger:Are conduits inside a building "Isolated in Air" . . . ?

Yes. Presuming you are talking about single copper conductors, run three side-by-side in conduit, with the conduit open to the atmosphere of the building (i.e., not buried in the slab or hidden within walls, then Table 310.73 applies. I read the phrase "isolated in air" to mean that heat can be dissipated from conductor to conduit, and from conduit to atmosphere, without having to pass through another barrier to heat transfer (i.e., dirt, concrete, or wall covering).