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).
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.
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.
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.
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.
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.
Since: Power =3D 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 =3D 2,300 watts.
A 15 amp lighting circuit, 115 x 15 =3D 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 =3D 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 =3D 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.
griswald is what my neighbor was called reportedly by everyone he knew.
he lit up the neighborhood, and his power bill:( collected donations for salvation army and created sometimes massive traffic jams, after his display was featured on news.
i alwasys expected him to blow the local transformer..........
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.
As Doug has probably been saying, the 80% limit is for continuous loads (over 3 hours). Major loads in a house are not likely continuous. A circuit breaker can operate at its full capacity, but may trip if at full capacity for over 3 hours.
Incorrect. You do not understand the "80% rule". The rule applies only to "continuous loads" which is defined by the Code as maximum current for a period of three hours or more.
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