Load capacity of 200-amp panel

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This came up elsewhere and I am just curious about what the answer is.
If someone has a main service panel with a 200-amp main breaker, how many amps of service can that panel actually service?
I am probably not wording this correctly, but I thought that I remember something about a 200-amp main breaker actually being okay for 400 amps of service since there are two separate circuits coming in (a 240-volt service split into two 120-volt circuits in the panel box).
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It all depends on voltage. A 220 amp service can in theory (you are not supposed to use more than 80%) supply 200 amps at 240 volts OR 400 amps at 120 volts or any combination of the above.
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Not so. You misunderstand the 80% rule.

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On Oct 22, 1:19�pm, snipped-for-privacy@milmac.com (Doug Miller) wrote:

plus the 200 amp dual breaker can and will carry a percentage more indefinetely
I had a friend who had the largest outdoor light display in the area, the power company loved him:(
checking the legs of his main service, it exceeded 200 amps on either side.
he couldnt run his dishwasher, washer dryer, or even a hair dryer as his wife found out when the lights were on..........
her hair dryer blacked out the total home.
when his kids got bigger he quit decorating......... but geez it was beautiful
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Aside from the 80% rule, you can't get 400 amps out of a 200amp service. The service consists of two hots, and a neutral. That means with a 200 amp service you can get 200 amps at 240V flowing between the two hots. Or you could get say 150 amps at 240V plus 50 amps at 120V. /In the latter case you have 200 amps flowing on one hot, 150 on the other hot, and 50 on the neutral.
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snipped-for-privacy@optonline.net wrote:

Which doesn't apply...

Of course you can; it just depends on which circuits are in use. If you're using only 120V circuits, you can get 200A on *each* leg. 200A @ 240V is the same power as 400A @120V.

Ummm....no. You could have up to 150A at 240V plus *100A* at 120V -- and if the loads are distributed evenly across the two legs, the current in the neutral is zero.
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Doug Miller wrote:

snipped-for-privacy@optonline.net wrote:

And, to make it perfectly clear, _only_ the two "hots" are on overcurrent protection; the neutral is not.
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Thanks.
That's what I thought -- that 200 amps at 240 volts is basically 400 amps available at 120 volts. Or, for example, if 50 of the 200 amps were for a 240 volt circuit, that would leave 150 amps at 240 which could be 300 amps at 120 volts.

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JayTKR wrote:

One other complicating factor is the 125A max branch circuit limitation. Not an issue in normal residential application of course as few people have single loads over 125A, but something to keep in mind when feeding subpanels.
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The difference is that you can't run a single 120V load at a full 400 amps. But you could run two different 120V loads at 200 amps.

The only limitation here is in the breakers for your panel. Larger breakers may be available; they often take up more space than normal in the panel, so as to have multiple connections to the same busbar.
Cheers, Wayne
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People just playing with words!
Since: Power = voltage multiplied by amperage. For example if one has individual 20 amp 115 volt circuits the maximum power each could carry is 115 x 20 = 2,300 watts.
A 15 amp lighting circuit, 115 x 15 = 1725 watts.
Similarly (ignoring the 80% rule for the moment) the maximum power that a 200 amp (Standard North American 115 - 0 - 115) domestic service can carry is 200 x 230 = 46,000 watts.
It is not possible for all the power could be loaded 'all on one 115 volt leg/side', as 115 x 400 = 46,000 watts. This would be rather like saying one could put the total weight of a ten ton truck ALL on one set of wheels! Or hiring two taxis to carry ten passengers, but then putting all ten passengers in one taxi, with none in the other!
That's also why domestic loads are 'supposed' to be balanced/ distributed' across both legs. In practice rarely operating in most situations at anything close to maximum loading. So balance not often an issue.
A domestic service double pole main circuit protects both legs of the incoming service. Once the trip limit of the breaker (200 amps say) exceeded, on either leg it would operate thus disconnecting both 115 volt legs.
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On Oct 22, 4:10pm, snipped-for-privacy@milmac.com (Doug Miller) wrote:

200A @ 240V is the
Yes but physically, a current of 200 amps is all that is actually flowing. Put a meter on it and you will measure 200 amps, not 400. It's a simple matter of Kirchoffs law.
What you are arguing is like saying a resistor that has 1 amp flowing in it is actually carrying 2 amps, because 1 amp goes in and one amp goes out.

That is not true. If you have 150A running at 240V then you have 150A coming in on one hot, 150A going out on the other hot during each half cycle and zero flowing through the neutral. The next half cycle, it reverses. If you now add another 50 amps between one hot and neutral, you now have 200A running through one hot, `150 amps through the other hot, and 50 amps through the neutral. There is nowhere for your extra 50 amps to come from to give you 250amps The max current flowing is still limited to 200 amps.
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snipped-for-privacy@optonline.net wrote:

200 amps on _each leg_. It's a total of (up to) 400 amps at 120V.

It's not at all the same. You are failing to consider that the two legs of a residential service can be treated as two *separate* parallel 120V circuits.

Right so far...

Sure there is: the other hot leg still has an extra 50A capacity.

Ahh, _there_ is the source of your misconception.
The neutral carries only the unbalanced current. When the other hot leg carries 200A as well, the current in the neutral _drops to zero_.

Suppose that the residence has no 240V loads of any sort -- gas furnace, gas WH, gas dryer, gas stove, no large power tools, no double-pole breakers, every circuit in the panel is a 120V circuit.
Do you maintain that the maximum power that could be drawn from this service is 200A @ 120V = 24kVA?
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On Fri, 23 Oct 2009 19:54:26 GMT, snipped-for-privacy@milmac.com (Doug Miller) wrote:

200A on each leg. Where's the 400A?
Being able to add to numbers* doesn't mean reality works that way.
[snip]
* - Actually, that's incorrect too. The addends are out of phase, so 200 + 200 = 0.
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200A @ 120V on leg 1, 200A @ 120V on leg 2.

Actually, it does.

Oh, you mean that if both legs are fully loaded, there's no current being drawn at all?
Sorry, but you don't understand. The current in the neutral is in fact zero, if both legs are loaded exactly equally -- and if all the loads supplied are 120V loads, then it is in fact drawing 400A @ 120V.
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[snip]

That current is 200A. That 400A is obviously not in the neutral. WHERE is it?
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There's no current in the neutral if the loads are balanced.
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On Sun, 25 Oct 2009 18:46:17 GMT, snipped-for-privacy@milmac.com (Doug Miller) wrote:

No current. I was replying to the person who claimed 400A.
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Assume you are using one leg at 200 amps, that is all the breaker will handle that is 120 volts X 200 amps or 24,000 watts. If you again max out the breaker with 200 amps flowing on both sides that is 240 volts x 200 amps or 48000 watts. Thats the same as 120 X 400 amps. I think the OP wanted to know if he could get a total of 400 amps at 120VAC. Lets rephrase that to could he power 400 1 amp 120 VAC loads from this box under residential conditions. The answer is yes but that sounds a lot like a commercial installation to me where the answer would be NO. I think this is a case of getting the right answers to the wrong question.
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On Sun, 25 Oct 2009 18:46:17 GMT, in alt.home.repair, snipped-for-privacy@milmac.com (Doug Miller) wrote:

How can people get this so wrong? It's basic electricity, you all should have learned this in high school.
In a 200A 240V split phase service, any SINGLE 120v load can draw up to 200A, no more. Because it is split phase, you can have two such loads. Now the math. 200A@120V + 200A@120V = 200A@240V, NOT 400A@120V. Because two 200A 120V loads on a single split phase panel are in fact operating in series (whether you deliberately wired them that way or not), presenting a de facto 200A 240V load on the panel. And, yes, in that case the neutral conductor current is zero.
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