Re: Main Panel Disconnect
John my numbers are based on a 400 amp service.
A 320 meter socket is rated 320 continuous, 400 max.
I do not believe you can use table 310.15(b)(2)(a) for parallel conductors.
Table 310.15(b)(2)(a) is not the rating of conductors it just modifies how conductors can be used in certain situations.
However after looking at this again 4/0s do seem to fit the bill.
For derating purposes 310.16 rates 4/0 copper as 260 amps.
260 x 2 x .8 = 416 amps.
You might even be able to use 3/0s
225 x 2 x .8 = 360
Using 240.4(B) this could be protected at 400 amps
if the calculated load was less than 360 amps.
I would be more comfortable with 4/0 then you do not have to worry about future loads exceeding 360 amps.
This would change if this was an underground service, then you would have to consider it a wet location and you would have to derate from the 75 C column instead of the 90 C column as I did above.
But the inspector might want to call the conductors in the raceway down the side of the house as wet location.
A lot of thought to this when in the end
Charlie's guys will come along with 1 AWG or 1/0 aluminum to feed these conductors.
(And it will work fine
)