Retaing for underground Service

[inspector 102]

A contractor wants to know what size wire he needs to run from a service beside the road with 100 Amp disconect, then 1450 feet to a garage building with underground lines. I would treat this as a feeder but how would I calculate any derating for that distance. I am reading in 215.2 that service entrance sizing applies which would mean #4 copper or #2 AL for feeder with no derating for distance. Is that correct. Need to give an educated answer so I don't look stupid, knew you guys could help as always. Thanks

 

[480sparky]

Why is a 'contractor' doing an electrician's job?

 

[Pierre C Belarge]

The NEC does not require ampacity adjustment for the purpose as you stated in your post.

Also, as an inspector, it is not your job to engineer the installation. The contractor or engineer can perform this.
If you were to provide calculations and they are incorrect, you may be on the hook for the installation not being proper.

 

[Dennis Alwon]

Voltage drop is based on the load. Figure what the load is then use this online calculator for VD

 

[M. D.]

http://www.elec-toolbox.com/calculators/voltdrop.htm

Here is an online calculator

edit to add;

dennis beat me to it

 

[M. D.]

I thought I could post the actual calculator

 

[inspector 102]

I should have stated that the contractor was simply bidding to place the wire for the electrician to hook up the eventual service. Price comparison on private line vs. Utility placing the line - no contest. By the time 600 mcm placed with trenching cost, ulitity can do it cheaper at $8000. Thanks for the quick responces and making me think more about questions that do not get asked very often. I am also not in the practice of designing a project for anyone, but try to give intelligent answer when I am asked the questions. Thankfully I have alway received helpful comments on this site.