200 amp service
- Thread starter tadziu
- Start date
- Status
- Location
- Lockport, IL
- Occupation
- Retired Electrical Engineer
Re: 200 amp service
You need to start with the Article 220 load calculations. The panels and the conductors must be sized to handle the calculated load.
You need to start with the Article 220 load calculations. The panels and the conductors must be sized to handle the calculated load.
rod
Member
- Location
- North Carolina
Re: 200 amp service
Tad,
You're supplied with 200A, you're providing one family unit with the capacity to draw 200A and the other family unit to draw 100A. That's a total of 300A potential demand on a 200A service. I think that if you simply replace the main on the 200A panel with a 100A main, you'll be good.
For multi-family dwellings 100A per unit tapped from a 200A service is pretty common here in the northeast. CharleyB, correct me if you think I'm off base here.
Tad,
You're supplied with 200A, you're providing one family unit with the capacity to draw 200A and the other family unit to draw 100A. That's a total of 300A potential demand on a 200A service. I think that if you simply replace the main on the 200A panel with a 100A main, you'll be good.
For multi-family dwellings 100A per unit tapped from a 200A service is pretty common here in the northeast. CharleyB, correct me if you think I'm off base here.
- Location
- Lockport, IL
- Occupation
- Retired Electrical Engineer
Re: 200 amp service
Rod: You?re not off-base. It is just that there is no meaning to a discussion of a 100 amp panel or a 200 amp panel or any other panel, until you know the calculated service load. Step 1 is Article 220.
Rod: You?re not off-base. It is just that there is no meaning to a discussion of a 100 amp panel or a 200 amp panel or any other panel, until you know the calculated service load. Step 1 is Article 220.
Re: 200 amp service
Maybe I wasn't clear with my question. I would like to upgrade the existing service which is presently a standard 200 service with 2 100 Amp panels per floor. The first floor is having an addition put on, and AC is being installed. The two existing panels are 100 Amp Main CB. I would like to change both panels (to get more circuits). The load for the building will only increase aprox 30 amps for the AC. 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 have never done it this way, and maybe I'm way out there, but is it possible? or do I ned to go to a 300 Amp service. I can avoid the whole senerio by using Main Lug panels and 100 Amp CB's. But it's a question I wanted to ask.
Maybe I wasn't clear with my question. I would like to upgrade the existing service which is presently a standard 200 service with 2 100 Amp panels per floor. The first floor is having an addition put on, and AC is being installed. The two existing panels are 100 Amp Main CB. I would like to change both panels (to get more circuits). The load for the building will only increase aprox 30 amps for the AC. 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 have never done it this way, and maybe I'm way out there, but is it possible? or do I ned to go to a 300 Amp service. I can avoid the whole senerio by using Main Lug panels and 100 Amp CB's. But it's a question I wanted to ask.
- Location
- Lockport, IL
- Occupation
- Retired Electrical Engineer
Re: 200 amp service
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.
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.
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.
russ
Senior Member
- Location
- Burbank IL
Re: 200 amp service
I agree with charlie b. on the use of article 220.
Read 230.90(A) Exception No.3
I agree with charlie b. on the use of article 220.
Read 230.90(A) Exception No.3
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