0

It seems common to use 400amp (320 amp class) panels. Are there any 400amp panel rated as continuous 400amp on the market? If yes, why not use these panels?

For the 400amp (320 amp class) panel, are there 2 sub-panels and is max current for each panel 160amp? Is there a different configuration available where one panel might support max 200amp and a second panel supports 120amp?

I am in the process of upgrading to 400amp, required by the city for our addition because we are going all electric, so I want to understand a little bit before engaging the electrician.

6
  • A little bit of formatting and the proper use of capitalization would make this question much more readable. Additionally, the question(s) about solar ready panels should probably be asked on its own as a separate question.
    – FreeMan
    Sep 15 at 18:22
  • I think most electrical devices are only rated at 80% of their label.
    – crip659
    Sep 15 at 18:22
  • 1
    Asking for solar panel recommendations is off-topic. I would edit that out if I were you. The rest is on-topic
    – Machavity
    Sep 15 at 18:32
  • I think a reading of the question that assumes good intent is that it asks for recommendations on features and best practices for breaker panels that are solar-ready, not that it asks for brand recommendations or for recommendations on solar panels. If read in full, the question is about whether a 400-amp-ready-for-solar panel is a realistic expectation. The question could be written more clearly and explicitly.
    – jay613
    Sep 15 at 19:37
  • You have to also remember other than code 100-400 amp restriction by the NEC the arc flash rating. I have seen more than a few homes that the utility transformer was larger than actually allowed by code and exceeded the panels rating (the panel / meter that the utility required). Most residential inspectors don’t check but I did have one that caught it and made the utility change the transformer,, (Stay with the big names for service equipment)
    – Ed Beal
    Sep 16 at 0:04
6

You're thinking about it upside-down.

Your logic is start with a 400A panel, and then what can you put on it? Actually it works the other way round.

You start with the characteristics of your house, and major appliances... and punch that into a residential load calculation. The load calculation takes into account continuous use, equipment's ability to tolerate short overloads, and the tendency to not run all appliances full-out at the same time. That pops out a number like 274 amps, so you get a service that is larger than that, leading you to a 400A service since that's what that power company offers.

If you were using the industrial charts for continuous loads, then you derate any continuous load by 125%. So you claim to have 400A of continuous loads, OK that's 500A derated and you need a 500A service. 600A is the next size up the power company will offer, so that's what you get.

So there is no circumstance where you will have 400A of continuous loads and expect a 400A service to be involved in that.

A 400A main breaker and main panel? If cost is no object...

Imagine someone is looking for a job in this market, and they get told "we're working from home, so you'll need your own PC". They've never bought a PC before. They get sold an $8000 Alienware gaming rig with dual 3090s, and don't think anything of it, because they have no idea what PCs are supposed to cost.

The same thing can happen to novices who get "target fixation" on obtaining a 400A main breaker and panel. Yes, with enough persistence you will find vendors cheerfully willing to take $2000 for a 400A main breaker and $3000 for a 400A rated load center/service panel, all out of the industrial catalog with prices to match.

I would say this is "not common at all" owing to the extreme cost compared to the normal method.

Dual 200A panels. Cheap and simple.

Prior to NEC 2020, the typical 400A installation was a meter pan lugged for dual 250 kcmil lugs ($200), feeding two 200A main-breaker panels ($150 each) via very short, unfused service entrance wires. Through the wall, no further.

Note that this common form of 400A meter pan cannot be used any other way, since the lugs cannot accept the 600 kcmil wire required for a 400A panel, nor is it designed nor approved for paralleling dual 250 kcmil wire.

In NEC 2020 installations, that becomes a 400A meter-main ($300) which contains one 200A breaker with a slot for a second (+$150), which then feeds two 200A+ rated main-lug subpanels ($150).

Simple, straightforward, approved everyday, and uses kit stocked at local stores.

Each panel must have its own local load calculation which must fall within the rating of the panel. So you can't load them 250A and 150A, because panels with 250A bus rating are uncommon. 225A is common.

2

Residential services are listed as 100-400 amp see 310.12.A , Don’t want to read see table 310.12.

There are true 400 amp services but you will find these usually require CT cabinets and metering as 400 continuous falls into commercial.

This is the reason you don’t find larger than 400 amp residential service panels.

They do make commercial panels in 450, 500, 600 , but as I mention now you are in commercial level power.

0

Don't try to redefine standard terms! If you want 400 A continuous output, then calculate what that is 80% of, i.e. 500 A and buy a panel rated thusly.
This is similar to board measurements, where a "2 by 4" is understood to be (varies a bit by region or country) 1.5 by 3.5 , and if you want a board that's 2 inches by 4 inches, you specify "true dimension" wood.

0

The part of the question about rated vs continuous and about getting more than 320A continuous is answered well in the other answers.

To answer the part of your question about whether the rated 400 amps could be divided other than 50/50, I've seen 225A and 175A residential main breakers available. There are ways you could split the service between those, putting the 225A breaker into a suitably large main panel. I don't think there is any other way to unequally split two-phase 400A service. I don't think you can do 320/160.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.