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tom31415926 08-23-2012 09:47 AM

distribution panel amperage rating

I'm changing my electrical service to underground, and will have a new location for my meter panel. To simplify the change-over, we will put a new distribution panel near the location of the old meter panel. The new meter panel will have a 100A breaker for the feed to the distribution panel. (The new meter panel also has some distribution likely to be used for the "heavy" loads.)

The new service will be 200A, the old service was 100A.

My electrician is on vacation, but I am to pick up the distribution panel. This is not time-critical right now, since the trenching is not done yet.

My electrician suggests that the distribution panel have a main breaker and 20 spaces, 40 circuits (20/40) capability. I can only find such number of spaces/circuits in a 200-Amp panel with main breaker.

Can a distribution panel be installed with a 200A main breaker that is feed through a 100A breaker upstream? I can certainly see that the wire to the distribution panel (awg 2, 3 conductor with ground) is protected and that the 200A main breaker in the distribution panel would become nothing more than a convenience switch. But would this cause confusion or problems later on?

If the distribution panel has a 100A main breaker, then there would be two 100A breakers in series, leading to some uncertainty as to which breaker would trip first - but is that a problem?

Anyone know of a good choice for a distribution panel with many circuits (approaching 20/40) and with a main breaker of appropriate size?

BTW, I have considered replacing the 200A main breaker in the distribution panel (if that's what I get) with a smaller-rated breaker (maybe even 100A). I know that such smaller breaker may not fit in the space provided for the main breaker, but that it could reverse-feed the bus if it occupies two "regular" spaces. I sort of prefer the main breaker to be set apart and so labeled, and not to use up two spaces doing the reverse-feed.

Any thoughts?


kevinp22 08-23-2012 09:56 AM


Strikes me as a bit odd to have an electrician have the customer buy some of the equipment (he's the one whosse name is on the permit, right?). Id wait for him to come back from vacation.

That isnt the answer you were looking for, so here are my thoughts on the rest of your question.

1. the breaker in the distribution panel (official name is sub panel) is just a disconnect, so it can be 200A

3. Buy a larger panel (say 40/40). Its not that much more expensive and gives flexibility later. I like Cutler Hammer CH but find out what is common in your area


tom31415926 08-25-2012 06:31 PM


I'll pick out a 200A panel with more spaces, then check with electrician upon his return. I guess he just wanted to work and not deal with materials in my case.

BTW, my maim breaker panel is CH series.


k_buz 08-25-2012 07:54 PM

It is a little difficult to follow what you are putting where.

You are installing a new 200A meter/main outside and feeding a new 100A panel at the old location? Is this correct?

If so, the 100A breaker outside feeding the sub panel will be the overload protection. You can install a typical 200A main breaker panel at the old location without any problem at all. The 200A main breaker at the old location will only serve as a disconnect, not as overcurrent protection.

tom31415926 08-25-2012 11:26 PM


Yes, you have stated my situation correctly.

I think the need to get many circuits arises from a desire to separate lights and plugs, as well as to align with new codes that require specific dedicated circuits.

Anybody have a link to a good discussion on typical household circuits and which ones have to be dedicated? e.g., does each bathroom need to have its own dedicated 20A outlet with GFCI? How many 20A kitchen counter top outlets are required? etc.


kevinp22 08-26-2012 09:42 AM


1. you dint have to separate lights and plugs (receptacles). however, I understand your desire to do so (I would if i were starting from scratch)

2. get a couple very good books on wiring (I really like Wiring a Houyse by Rex Caulfield if you are doing "above code". Wiring Simplified (sold at Home Depot) is great for code guidelines

3. use the search function to find old threads


k_buz 08-26-2012 09:46 AM

Is this a complete rewire? Do you already have a permit? Are you (personally) going to be installing the new wiring? Have you contacted your local inspection department about what is required? I think you are going to find that you will need AFCI protection for many of these new circuits along with tamper resistant receptacles.

California has its own code. They don't go directly by the NEC. The current CEC is based off the 2008 NEC, but that is as much as I know about your state. I do know, that other codes do affect electrical work such as vapor barrier boxes and such.

Jim Port 08-26-2012 12:41 PM

There is no way I would try and sell a customer a 20/40 panel unless space was an issue. A double pole breaker would take up the spaces of 4 potential 120 circuits. Tandems are also more expensive than a full size single pole breaker.

If it were my money I would install a 40 circuit panel. If you are keeping the old panel too I might consider a slightly smaller panel depending on the cost difference.

tom31415926 08-26-2012 12:56 PM

We have a permit for the new electrical service, the trenching, and moving the existing circuits to a distribution panel. I was thinking of future remodels where I'd like to add/move outlets or create new circuits. At those times, I would consider getting a permit and doing the work myself. But the present job is too bit for me and I'm relying on the electrician. We are awaiting the approval of the trench and conduit by the utility company, then we' can make the switch.

I guess I'm asking code questions now just because I'm interested in it and it impacts the number of spaces I need in the distribution panel for the future.

I've been wanting to upgrade to new code, but my old panel would not accommodate the new breakers - the new one will.


andrew79 08-26-2012 01:56 PM

Refreshing to see someone actually do things the way they should be done. My advice is ask if you can watch or even help the electrician with the install and pick up some pointers.

Your the exact type of person that should be doing DIY. Learning how to do it it right so the next time you can do it yourself.

tom31415926 08-26-2012 04:09 PM

It helps that I'm an EE. I normally work in integrated circuit design with much lower and safer voltages!


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