How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Mike G. Your Own Question
Mike G.
Mike G., Master Electrician
Category: Electrical
Satisfied Customers: 7649
Experience:  Proven Professional 48 years Experience
Type Your Electrical Question Here...
Mike G. is online now
A new question is answered every 9 seconds

400 amp main disconnect panel. what size wire and how many

Customer Question

400 amp main disconnect panel. what size wire and how many for 50 foot run?
JA: I'll do all I can to help. Tell me a bit more about what's going on so we can help you best.
Customer: Installing new 400 amp service to bldg. in Georgia. I(1) main panel and (2) subpanels of 100A and 250A. MDP is 50 feet from transformer (u/g) and two sub panels are 100 feet from MDP. Thanks
JA: Anything else I can tell the Electrician before I connect you two?
Customer: 400A, 3ph, 208/120v
JA: I'm sending you to a secure page on JustAnswer so you can place the $5 fully refundable deposit now. While you're filling out that form, I'll tell the Electrician about your situation and connect you two.
Submitted: 1 year ago.
Category: Electrical
Customer: replied 1 year ago.
Can I get size of wire for both sub panels as well?
Expert:  Mike G. replied 1 year ago.
Hi, I'm Mike G and I'll be assisting you. The wire sizes are as follows;400A service = 400MCM copper100A sub feed = #2 copper250A sub feed = 4/0 copper
Customer: replied 1 year ago.
Thanks, ***** ***** mention this is (3) phase service to all three panels. Don't I need at least three wires to all panels. Also what about ground wire and size?
Expert:  Mike G. replied 1 year ago.
The sub feed should be 4 wires plus the ground, if 120/208V 3 phase. 3 wire plus a ground if only 208V 3 phase. Your 100A needs a #8 wire copper ground, your 250V needs a #4 wire copper.