conductor derating/conduit fill

[bwyllie]

need to derate conductors because there are approx 30 current carrying conductors in a conduit, wiring is for workstations. when is it applicable to use Table B.310.11 in Annex B?

 

[jwjrw]

I believe the table in annex b is the same one in 310.15(b)(2)(a)
The annex is just for informational purposes only.

 

[jwjrw]

You use that table anytime you have more than that 3 CCC's in a raceway. Also when bored holes are fire caulked and I think when cables are bundled together.

 

[infinity]

For 4-6 or 7-9 conductor the derating factors are the same as 310.15(b)(2)(a). When you exceed 9 CCC's you can use this table where the load diversity is 50%.

I'm guessing that this table will not apply to your installation.

 

[jwjrw]

For 4-6 or 7-9 conductor the derating factors are the same as 310.15(b)(2)(a). When you exceed 9 CCC's you can use this table where the load diversity factor is 50%.

I'm guessing that this table will not apply to your installation.

Infinity will you define "load diversity factor" for me?

 

[480sparky]

Derating and fill are two separate issues.

Derating is reducing the ampacity due to a variety of issues. Fill is how many little circles will fit inside a big circle.

 

[charlie b]

Infinity will you define "load diversity factor" for me?

You could simply use the NEC's definition. But then again, it doesn't have one. :roll:

By the way, the term is "load diversity," not "load diversity factor."

 

[infinity]

You could simply use the NEC's definition. But then again, it doesn't have one. :roll:

By the way, the term is "load diversity," not "load diversity factor."

Yes, the correct term is load diversity not load diversity factor.
I will correct my earlier post.


Here's a definition from IEEE:

The difference between the sum of the maxima
of two or more individual loads and the coincident of combined maximum load usually measured over a specified period.

Here's a simpler version:

Diversity occurs in an operating system because not all loads connected are operating simultaneously or are not simultaneously operating at their maximum rating.

 

[jwjrw]

You could simply use the NEC's definition. But then again, it doesn't have one. :roll:

By the way, the term is "load diversity," not "load diversity factor."

I looked in the NEC and didn't see it anywhere so I thought I would ask. The wording is a little confusing. At least to me it is.