I'm unsure of what size wiring trough to use . I'm coming into the trough from the meter pan with 500 MCM (320 amp single phase service) I'll be coming out to two 200 amp service disconnects and using 3/0 wire. An electrician neighbor of mine recommended a 12" X 12" X 48" trough but the electrical supply house believes that a 8" X 8" X 48" trough will do . The electrician says that the extra room in the 12" X 12" X 48" wiring trough will make it much easier to work the heavy cables in.

Thanks Mr. TK Russell for all the questions that you've answered

amiteman

The cross sectional area of the sum of the wires cannot exceed 20% of the cross of a wireway. Assuming 3-#500MCM, 3-#3/0, and 3-#4, all THHN/THWN totals 22.92 sq in, so a 5"x5",if it existed, would work The next size is 6"x6".

AN 8"x8" = 64sq in.Electricians like to have extra room when working with these large wires, they, quite frankly, are a pain in the a** to manhandle. Your neighbor may have had a bad experience, or is guessing wrong.

An 8x8 will offer plenty of work room. . Just remember to stagger the large wire connectors. Best to use the insulated connectors, can come with multiple ports in the proper sizes, each lug is a allen wrench bolt with a little insulating plug to cover the screwhead, made by Ilsco, NSI, and several others.

Be sure connect a grounding pigtail to the metal wireway, use #4 with a lug and a machine screw.

I'm going to do a service 3 phase 250 amp what wire do I have to use

I'm gointo do a service 3 phase 250 amp what size of wire
Do I have to use

A) You should start a new thread with this completely unrelated question to a three year old existing thread.

B) If you have to ask this question in this manner you should really hire an electrician. Considering this is a 3 phase commercial job cements that fact.

He should ask the guy at home depot. They seem to have all of the materials needed so even an ameteur can try to go and kill himself.
Wonderful what home depots have done to the small contractors.

Hiwire, please note the date on the threads your answering.

Besides, hardware stores do not sell three phase equipment.