It's after 5 so i can't call the supply house to see what kind of products are carried. If it were a residential application, I'd just get a 320 class meter and double tap each phase for each panel. However, we are talking about a commercial site, and the owner wants a 400A service. The panels are going on an exterior wall, and the meter will be right behind them outside. Do the same principles apply? Does a 3 phase meter base that can be double tapped exist? I've been looking all over the net to no avail. If not I'm planning to get a 400A meter base with (2) 200A breakers in it. As long as there 400 amps of power, the owner doesn't care how many electrical panels there are. I don't think a 400A single panel, if it exists, would be cost efficient. I'm looking for a small amount of guidance here. I'll be calling the supply house when it opens, just trying to get ahead of this thing a little.
What is the calculated load? You said owner wants 400 amp service - any particular reason why? Non electricians do not always understand these things. Total kVA capabilities means more than how many amps the main breaker has marked on it. If it is 208 volt 3 phase 400 amps gives you around 144kVA, if it is 240 single phase it is only 96kVA, if it is 480 volt 3 phase it is 332.5kVA.
As far as knowing what supply house carries after 5 --- you can get arrested if you try to find out:happyyes:
A 320 or 400 amp meter base will have room for 2-200 amp feeds, some have lugs already, some just have studs and you put in your own lugs based on what you need.
You can also get (400 amp main breaker in your case) panel with up to 84 circuits from some manufacturers now that the 42 circuit rule is gone, I know Square D has them. They are pretty tall and with 1 inch wide breakers like most others have they will be even taller (if they make 84 circuit versions)
I will add that 200 or 225 amp panels are likely stock items and if you are in a rush may be stuck with that option. There may be limited 400 amp panels in stock at some suppliers, the rest will usuallyt order them as requested - they often are a build out of standard components item anyway. You determine bus and number of spaces, add main breaker kit if it is needed, subfeed lugs or other accessories, then based on what you have, select the enclosure and trim that it all fits in.