I'm adding a workshop needing its own 200A panel, and power company (TEP) is requiring me to move the service entrance from the house to the workshop (and upgrade to 400A panel) the house is to be backfed as a feeder 100' to its original (old) 200A panel, moving the entrance from the overhead meter to from below (see pic). The bond between neutral and ground will be removed in the house panel. the entrance feeder will carry 4 wires in a 2.5" conduit (Al250 Al250 Al4/0 and a #6cu ground wire). ground rods will be kept at the house and tied to the incoming #6 ground (there is also a big ground rod at the shop where it is tied to the neutral leg) I finally Found an affordable box approved for 400A by TEP on a waiver, don't know why they are so expensive...
There is a bunch of space in the old 200a house box behind the breakers (the box is 5.5" thick, and the insulators just stand off 1.5" all the way up to the main breakers on top. Can I run the new entrance below the breakers in the box straight up to where they tie to the lugs? (ive never seen this on any other box... and I plan to run in the gutters as normal otherwise)
Does anyone see anything wrong with my plan (I wont remove the N-G tie till the day service is cut off)?
Edit: Proposed new 400amp all-in-one meter panel Is a Siemens MC0816B1400SC . Old panel is something from GE. Shop will need 200a, and Tucson Electric Power directed us to drop the service into the shop and customer (me) run back feeder to power the house box. Rationale was, they didn't have any more capacity on the pole at the house and the shop is closer to another pole (even though its just 100'). I had proposed the update recommended (320 service to house with sub at shop, they said "nope, no more capacity")
Here are the current knockouts on the existing House 200A box...I cant find the label on it with the make and model. I do have some moving around to do for a couple of the existing conduits -out- to make room for the giant feeder into the center.