How many amps do I have coming in?

[Aaron Fude]

Hi,

If my master breaker consists of two 100amp switches, does that mean I have 200amps to play with.

(When I was remodeling the bathroom, before I knew anything about all this, I had several electricians come in. Most of them said I don't have enough current coming in and that I should upgrade to 150 or 200 amps. Only one said "I have no idea what they are talking about, you have plenty of amps coming in." So now I'm intrigued if the rest were blantantly deceiving me or just a little bit, since the bathroom has been finished and I'm not having any problems with A/C running and a house full of guests.)

Many thanks in advance,

Aaron

[hallerb]

yeah you do have 200 amps total, but a upgraded 200 amp service gets you a total of 400 amps.

we have never tripped our old 100 amp main but ran out of spaces for breakers.... so upgraded.

remodel issue probably involved space capacity as much as amp capacity

[Joseph Meehan]

...

Not exactly. It means you have 100 amps at 240V or Two 100 amp circuits at 120V it does not mean you can put over 100 amps at 120V on one leg the service. If everything were on one side of the service and you were using 110 amps total at 120V it should blow the breaker.

You do have 200 amps to play with if your follow the rules.

[EXT]

Shortage of breaker space can be solved with a branch panel, get one that uses the same breakers as your main panel so that they can be moved as needed. A lot cheaper than upgrading your service entrance equipment.

yeah you do have 200 amps total, but a upgraded 200 amp service gets you a total of 400 amps.

we have never tripped our old 100 amp main but ran out of spaces for breakers.... so upgraded.

remodel issue probably involved space capacity as much as amp capacity

[dpb]

Depends on how they're arranged and supplied. Assuming they're each fed from the service feed, then there would be 200A combined load.

How and why that would be in a given panel is a wonder as there should be only a single-point disconnect afaik.

--

[RBM]

yeah you do have 200 amps total, but a upgraded 200 amp service gets you a total of 400 amps.

we have never tripped our old 100 amp main but ran out of spaces for breakers.... so upgraded.

remodel issue probably involved space capacity as much as amp capacity

The method of determining your service size has little to do with adding up the amperage of multiple main breakers, if that is what you're doing. It is determined by the service entrance conductor size. a 200 amp 120/240 volt service will be at least 4/0 aluminum or 2/0 copper, and a 100 amp 120/240 volt service will be at least #2 aluminum or #4 copper

[David Nebenzahl]

On 6/3/2008 6:33 AM dpb spake thus:

Huh? Far as I know, all main disconnects (at least in North America,

220-volt service divided 110-110*) require two switches, as there are two legs. How would you have a "single-point disconnect?"

• Or 240-volts divided 120-120, for the nitpickers ...

[Doug Miller]

200A at 120V, or 100A at 240V, or any combination totalling 24KVA. That's an oversimplification, but it's close enough for purposes of this question, I think.

Such a configuration is normally referred to as 100A service, since it's supplied at 240V.

One handle connecting the two sides of that duplex breaker.

[Joseph Meehan]

Those two switches should always be connected in such a way that the both go off and on at the same time. Other wise you can get some very undesirable results.

[pheeh.zero]

I have one 100A 2-pole breaker(on my panel). (3 phase would use a 3- pole breaker)