ECN Forum Forums General Topics of the Trade General Discussion Area 400 amp service

Tom I was wondering the same thing as Pierre.


Both panels contain a service disconnect, both panels must be bonded.

Here is a graphic that shows the bonding, of course you may not have a trough but you can ignore that part of it.



You can choose to run one GEC based on the 400 amp service conductors than tap it at the panels based on the 200 amp service conductors feeding each panel. 250.64(D)



[This message has been edited by iwire (edited 01-18-2005).]

I have installed a "400amp" underground service as we call it with two 2inch PVC conduits with a 4/0 URD aluminum triplex in each pipe. Come up to the 320 meter and use dual lugs to terminate. Then come out of the back of the meter can with two 4/0 aluminum SEU cables and drop into the basement into two 200amp main breaker 40 circuit panels.

For the GEC, I run #2 copper from 1 panel to the street copper water pipe.I then tap the #2 copper above where it enters the 1st panel with #4 copper and ground the 2nd panel. I also install 2 ground rods outside and run #4 copper into the meter can for the supplimental grounding electrode. Enclosure bonding is achieved by tighting the green bonding screw inside the main panels.

I have seen the above described installation with a #4 copper GEC run from each panel over to the water pipe.But I interpet Note #1 under table 250.66 to mean we are to add the circular mill area of the two sets of 4/0 URD feeding the meter can together and then base the size of the GEC by that figure.

So from table 8 in chapter 9, 211600 x 2= 423200 CMA...table 250.66 calls for a #2 GEC.

400amp service?...more like two 200amp services.

shortcircuit

My bad.

Thanks for pointing that out. My understanding was 1 bond screw per service but it's really service disco. I do remember having to take out the second panel screw to make an inspector happy a long time ago and just did it like that sence. I would say they were still bonded six ways to Sunday but it was missing the screw on the second.

Bob,

Here in NJ we do the same thing with the "400" amp meter pan.

BTW do you see Gary or Andy? The guys from Cedar Crest? If you do, tell them I quit that job.

You quit???

I hope all is well for you.

Gary is running another large housing complex close to home right now, I last saw him at the adult xmas party.

Andy? I can not think of who that is right now.

Sean is around I saw him at the Kids xmas party being a good Dad.


Bob

In my neck of the woods, for single phase services, anything 200A and less is straight through metered (usually with a 200A meter). Over 200A, a CT meter system is used (usually a pole system serving a farm, but I know of one residential CT metered service).

Shortcircuit


You don't want to call it two services, that NEC would not allow it.

Not two 200 amp services of the same characteristics. 230.2

Bob

Oops...your right Bob. How about 360amp service with two 200amp disconnects

shortcircuit

I am glad you knew I was just joking around, what you describe does sound very close to two services on one meter.

Bob