Load capacity of 200-amp panel

Posted by Doug Miller on October 22, 2009, 4:10 pm

trader4@optonline.net wrote:

>Aside from the 80% rule,

Which doesn't apply...

> you can't get 400 amps out of a 200amp
>service.

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.

> 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.

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.

Posted by dpb on October 22, 2009, 4:29 pm

Doug Miller wrote:

> In article

trader4@optonline.net wrote:

>> Aside from the 80% rule,

>
> Which doesn't apply...
>

>> you can't get 400 amps out of a 200amp
>> service.

>
> 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.
>

>> 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.

>
> 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.

And, to make it perfectly clear, _only_ the two "hots" are on
overcurrent protection; the neutral is not.

--

Posted by JayTKR on October 22, 2009, 9:36 pm

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.

> In article
> trader4@optonline.net wrote:

>>Aside from the 80% rule,

> Which doesn't apply...

>> you can't get 400 amps out of a 200amp
>>service.

> 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.

>> 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.

> 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.

Posted by Pete C. on October 22, 2009, 10:17 pm

JayTKR wrote:

>
> 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.

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.

Posted by Wayne Whitney on October 23, 2009, 12:24 am

> JayTKR wrote:

>> That's what I thought -- that 200 amps at 240 volts is basically 400 amps
>> available at 120 volts.

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.

> One other complicating factor is the 125A max branch circuit
> limitation.

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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Load capacity of 200-amp panel - Page 2