Underground Duct Bank Ampacity Calculation

[budhiman]

Hello All,

I will be using software (etap) for underground duct ampacity calculations. I was wondering what all information for cable is required to use Neher-Mcgrath equation. I will be requesting information for cables from the cable manufacture, want to make sure I request the correct items.

 

[BlackJackJacques]

The NEC cable section used to show the Neher-Mcgrath equation and defines its parameters - however, in 30+ years I have yet to see an actual example of this formula used. For duct bank ampacity deration, etc, you will probably better off using the NEC figures and tables.

 

[7anoter4]

For low voltage cable [up to 2000 V rating] you need:
-conductor diameter[it could be different for class B stranded, compressed or compacted]
- insulation thickness[or insulated core diameter]
- jacket [if any] thickness or diameter
- it could be a nylon overjacket sometime.
For shielded cable [up to 35 kV] you'll need more. See-for instance:
Calculation of Underground Cable Ampacity by Francisco de Leon

https://pdfs.semanticscholar.org/bd96/48cef655edbe119ccab8defd67b26973dd6e.pdf

 

[7anoter4]

 

[RonShap]

ETap takes care of the conductor info for you, just tell it the size.

The more important info is the installation characteristics. rho of the surroundings, spacing between cables/ducts, load factor, current