ECN Forum Forums Code Related Discussion NEC & other Code issues 400 Amp Service

I recently did a service that someone else started where I had to relocate the service head. I used 250 kcmil from POCO service drop to a 320 amp rated meter. From out of the meter there were two sets of feeders, each going to 200 amp main breaker panels fed with 2/0 copper. So this is considered a 300 amp service based on the size of the feeders going to the POCO drop. Correct?

Could someone tell me what article permits using (2) 200 MB panels for a 300 amp service?

#2 copper was run to H20 meter and #4 copper was run for the Ufer. Also, #2 jumper was installed to bond both ground busses in either panel.

Just want to clear up that I have done mostly residential,not that the garage is residential. It is non-residential. Thanks

Services are popularily sized per the combined ratings of the service disconnects, despite 250.66 requiring the GEC based on the size of the SEC.
230.23(A) sizes the SDL, 230.42(A) sizes the service entrance conductors, 230.71(A) allows up to six service disconnects, and 230.90(A) requires the OC device to be rated no greater than the ampacity of the service entrance conductors.

Schockme, I wouldn't call your service 300 amps, unless you installed two 150 amp mains.
2/0 copper is good for 200 amps per 310.15(B)(6) for residential services, you have two 200 amp mains and panels, for a combined 400 amps of capacity. I'd call that a 400 amp service.

230.90(A) exception #3 allows the sum of the ratings of the 2-6 circuit breakers to exceed the ampacity of the service conductors, provided the calculated load does not exceed the ampacity of the service conductors.

George, you may be correct as to the calculated load not being continuous.

Services are an area where the NEC changes places with the local PoCo rules. It is the practice of our PoCo to treat the calculated load as if it were continuous, and change over to a CT type meter at that point.

Likewise, and service upgrade 200 amps or larger must be approved by their planning department. Again, they need to know what loads theit transformer will be facing.

SInce local PoCo rules vary greatly, I really have to stress the need to talk to them when a job like this one comes around.

Thanks Earl.

Earl IMO To determine the ampacity of a service requires more than adding up the combined rating of the service disconnects.

If you do that you stand a good chance of overloading the service conductors.

230.90(A)Ex. 3

Here is a common example of using Ex.3 This is a service a buddy of mine did.



Notice the size of the riser, it has a capacity of about 200 amps. If you add up the six main breakers inside you would get 600 amps.

This is not a 600 amp service, this is an approximately 200 amp service with six 100 amp service disconnects.



[This message has been edited by iwire (edited 01-01-2007).]

So those are sill plates, I always wondered what the were used for, pictured where the SE enters the building. Is that last meter allowed. I know that on some 2-gang meter sockets there is a label stating that the other set of lugs are not meant for feed thru.

[This message has been edited by HCE727 (edited 01-01-2007).]

[This message has been edited by HCE727 (edited 01-01-2007).]

iwire, where are the disconnects for those meters? And is that se at the bottom of each meter? Don't you have to protect wire from physical damage? Sorry for all the questions.

[This message has been edited by texassparky (edited 01-01-2007).]

HCE727, My buddy could have bought a gang socket but the units only needed 100 amp sockets and the power company requires a 200 amp socket for the landlord panel even if it is a 100 amp panel.

So you see a 5 gang 100 amp socket with a single 200 added on the end.

And yeah those are sill plates, kind of hard to use and not exceed the bend radius of cables. But that is an accepted practice in this area.

Bob

The Panels are all main breaker type located on the inside of the wall behind the sockets in the basement. The longest SE inside is about 5'


Yes.


That is up to the AHJ if they feel they are subject to damage.

These are not on a driveway so SE is generally accepted. If this was the driveway side the inspector would likely want PVC 80 or RMC.

This service as you can see is new, but I could drive down any multifamily street in most any city and town in MA, RI, CT, NH etc and take pictures of thousands of identical services.

As matter of fact here is the service he was replacing.





Notice the original services had no mains.


No problem, that is what this place is about.

We all do things differently, I know that all this SE is surprising to electricians in many areas.