Re: 200 amp service
Originally posted by tadziu:Maybe I wasn't clear with my question.
Maybe I wasn?t clear with my answer. My answer wasn?t clear because it didn?t address the question you asked. Rather, it addressed the other question that you didn?t ask, but should have asked.
So I will now give my answer to the question you did ask, and then I?ll return to the other question.
You can change both panels to get more circuits, so long as you don?t go beyond 42 circuits. But that has nothing to do with either panel being 100 amp or 200 amp. If you plan on using a 200 amp main breaker on the one panel and a 100 amp breaker on the other, then Rod is right. You could draw more current than the meter is capable of supplying, and there would be no protection for the overcurrent condition. So my answer would be, ?No, you cannot do this.?
Now back to the ?other question.? I?ll start with, ?Why do you think you need a 200 amp for one of the panels? Why not use a 100 amp MCB panel for both units? Do you think the load on the first floor will be more than 100 amps? Why do you think that??
Please look at 220.3(C). You say there will be ?an addition? to the first floor. Is it more than 500 square feet? If so, you have to go through the entire load calculation process. That was the message I tried to give in my previous responses.
If you wish, you can also start with 220.31(B), and use the optional method for an existing dwelling unit. You cannot use the optional method of 220.32 for multi-family dwelling units, because that applies to more than two units.
The bottom line: Until you know the load, you cannot tell whether you need more than a 100 amp panel.
So I was wondering if I could run a 100 Amp panel and a 200 Amp panel on a standard 200 amp service, using derating techniques for multi family houses.
I don?t know what you mean by ?derating techniques for multi family houses.? If you mean ?use the optional method of 220.32 for multi-family dwelling unit,? that is not an option, as I mentioned above.