400A 3ph 4w Service - Single 400A or Dual 200A Main Breaker - Best Practice

[Speed101]

I'm installing a 400A 3-phase 4-wire 240/120V Service.
Requires sub-feed, >= 36 single positions, outdoor cabinet.

There are lots of 200A main breaker / service cabinets outdoor rated.
Very few 400A. Pretty much have to build-up custom: interior+cabinet+sub-feed block.

Cost-wise dual 200A will likely be much less expensive.

Functionally single 400A has some load-balancing advantages after the sub-feed considered, but dual 200A most likely not a show-stopper.

Also very few 3 ph main breakers explicitly rated for 240/120V (w/ its 208V high-voltage leg). Square D NF does so, but regular 208/240 3ph breakers may be fine. Still need to see the rating.

Is there a good 400A product/solution here that won't break the bank?

 

[Robert Hutcherson]

Heres my 2 cents:

Install one 400amp service with K7XL meter. Install one set of 3-0thhn-cu from double lugs on the meter over to each panel.

Install (1) 200amp 3ph 4w MCB panel. Use this to only run your 2 and 3 pole loads due to the Hi-leg. Main 1 of 2.

Install (1) 200amp 1ph 3w MCB panel. (A and C phase) Use this to run your 1 pole 120volt loads and any overflow 2pole loads. Main 2 of 2.

Good luck!

 

[Speed101]

Thank you Robert! That's probably the best and most economical approach. My concerns (part that I must answer myself):

1. Need feed-through lugs on both main breaker panels - any 200A suited for that task you lean?

2. Concern w/ dividing the loads between the two 200A circuits and guaranteeing diversity will take care of the rest is (e.g. concern of a period with 250 A load on one panel while only 50A on the other will blow a 200 main whereas same be fine all on 400 A - there are several infrequent but singularly large 3-ph loads that don't leave much margin on a 200A panel).

3. If I go 400A, I'm leaning toward the Square D NQ panels with QO breakers and feed-thru kit, outdoor box, but suspect those are a pretty penny compared to familiar 200A boxes. Am I right or are there exceptions worth knowing about?

Seen many panels rated for 3 ph 208Y, but not sure if they are suited for the high leg on the 240/120 delta 4w. The NQ panels are explicitly rated for it.

Thanks again.

 

[Robert Hutcherson]

Install 400amp 3ph4w 120/240volt service to K7XL Meter.

Install 400amp panel with 400amp MCB(Main 1 of 1) circuited for loads and some future capacity.

Install one subfeed circuit breaker (in main panel) say maybe 100amp 2pole sized for capacity of 120volt or 120/240volt loads.

Install one subfed panel with phase A and C for circuits with neutral loads and/or small 2pole loads.

I would get a price from Square D and Siemens.