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400 Amp Service #100555 12/01/06 07:53 PM
Joined: Mar 2003
Posts: 92
G
gserve Offline OP
Member
Hi,I am an electrician that has done mostly residential work up to 200A service.I have a job that will require 400Amp service.Seeing I have never done one I am seeking any advise that you could give me.I have read that most of the time 2 200A panels are used.This project is a garage and I would like to use just 1 main panel.Is this impractical? Just looking for some guidance. Thanks in advance.

2017 / 2014 NEC & Related Books and Study Guides
Re: 400 Amp Service #100556 12/01/06 08:44 PM
Joined: Jan 2003
Posts: 4,391
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iwire Offline
Moderator
If you use a single 400 amp panel in place of two 200s you will pay more money and have half the circuit space when it's done.

The last 400 home service I did I used a single 400 only because I had not yet seen a double 200 set up. If it comes up again I am going with double 200s.


Bob Badger
Construction & Maintenance Electrician
Massachusetts
Re: 400 Amp Service #100557 12/01/06 09:10 PM
Joined: Apr 2001
Posts: 449
F
Fred Offline
Member
I use either a 320A metermain with (2)200A breakers installed to feed (2)200A 40ct ML panels or if they can be back to back with a 320A meterbase I use (2) 200A 40ct MB panels. I am currently upgrading a 320A service at a house to an 800A due to a 6500 sq.ft. addition. The PoCo is hitting my CT cabinet at the addition where it will feed a 800A ML panelboard with (1)400A CB to feed the old service and (2) 200A CBs to feed (2) 200A 42ct ML panels in the new addition. Houses around here keep getting bigger and stupider.

Re: 400 Amp Service #100558 12/02/06 12:30 PM
Joined: Jul 2004
Posts: 9,541
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gfretwell Offline
Member
I always wonder how much of that 400a actually gets used. What are these people's electric bills? Average 60a 24/7 is over $1000 a month here.


Greg Fretwell
Re: 400 Amp Service #100559 12/02/06 01:11 PM
Joined: Jul 2004
Posts: 625
S
SolarPowered Offline
Member
Quote
I always wonder how much of that 400a actually gets used. What are these people's electric bills? Average 60a 24/7 is over $1000 a month here.

Generally speaking, in many places 400A service is the next step up if the load calc exceeds 200A. And, of course, the load calc is interested in making sure that the probable sustained peaks are covered; it's not about the average draw. So one might need a 400A service when the current draw averaged over the course of a month is only a few dozen amps or less.

Re: 400 Amp Service #100560 12/03/06 06:55 PM
Joined: Mar 2003
Posts: 92
G
gserve Offline OP
Member
So it looks like I need a 1/O GEC for 400A service based on 600 kcml conductors. Do you normally parallel them with smaller conductors? Any help on the conductor size please. Also do they make a rebar clamp for the 1.5" rebar for the 1/O conductor size?

Re: 400 Amp Service #100561 12/03/06 07:04 PM
Joined: Jan 2003
Posts: 4,391
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iwire Offline
Moderator
4 AWG CU is the largest conductor you ever have to run to a concrete encased electrode.


Bob Badger
Construction & Maintenance Electrician
Massachusetts
Re: 400 Amp Service #100562 12/03/06 07:11 PM
Joined: Mar 2003
Posts: 92
G
gserve Offline OP
Member
Thanks Iwire. How about help with the service conductor sizing.If 600 kcml is required what 2 sizes do I need to parallel to make up this size?

Re: 400 Amp Service #100563 12/03/06 08:51 PM
Joined: Jan 2005
Posts: 5,316
renosteinke Offline
Cat Servant
Member
Just a reminder to pay extra attention to your load calcs. If the calculated load is over 320 amps, then a different type of service - one with a current transformer- will be needed.

Re: 400 Amp Service #100564 12/03/06 09:38 PM
Joined: Jan 2004
Posts: 1,507
G
George Little Offline
Member
Reno- I believe that would be true if the 320a. were a continious load. He stated that this was a residential installation and residential is not continious. He could do the calc and come up with 400a. and if the equipment were rated for 400a. he's good to go.


George Little
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