400 amp meter installation

Status
Not open for further replies.
R

Rick Quarles

Member
We have an existing single family residence that has a 3wire 200 amp service. The electrician is going to put a 400 amp meter-disconnect combo and he wants to leave the existing panel that was originally in the middle of the house. Since the existing panel is 200 amp can he just install another panel in the residence with a 200 amp disconnect?? The reason for a 400 amp is he is building a detached garage so he wants enough power for future equipment.
 
as long as the feeder is fused correctly, there is no problem w/ a 400a meter feeding a 200a panel. we do it all the time, but usually w/ two 200a's parallel. we've also installed 400a services w/ 200a feed-through panels on each side to accomodate accessory structures.
 
Rick, if you place a disconnect ahead of the existing panel, you will have to re-feed that panel with a 4-conductor feeder, separate its supplied EGC's and neutrals, and re-feed any 3-wire major applicances with 4-wire cables and/or plugs and receptacles, separating their EGC's and neutrals as well.
 
The problem I see is there is a 400 amp service disconnect (fused or CB), that is supplying a 200 amp rated panel. NO GOOD!

If you were to have a 400 amp rated meterpan and supply the 2-200 amp panels (with Main breakers), that is permitted.

In order to supply the 200 amp panels from the 400 amp rated disconnect, you will need to install 500's to a trough by the 2-200 amp panels and then "tap" the 500's to the 200 amp panels. See 240.21(B)
 
Be sure to look at available fault current. Where I live a 200A service would typically be 10KAIC at the service, but a 400A would 22KAIC or more. With a typical residential feeder length the existing panel would either have to be series rated or would have to be upgraded to fully rated. Whether you can do either depends on the age of the panel and the breaker model.

Martin
 
400 amp

400 amp

Rick, you mentioned detached garage. In this area, in your situation, we have allowed the meter socket to be changed to 400, with one set of s/e feeding a 200 amp disconnect to pick up the existing panel and a seperate set of s/e to run from the meter socket underground to the derached garage.
That's a AHJ call here.
 
Status
Not open for further replies.
Top