Load calcs, service conductors, breakers

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wawireguy

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After reading some of the recent posts I realized I don't full understand a few things about smaller services. What I'm not clear on is taps at the meter and sizing breakers.

Lets take a detached shop and a small house. Load calc on shop is 60amps. Calc on house is 100amps. Going to put in a 200 amp service. Going to meter at shop. Going to put a 100 amp panel in shop. Also will be putting in a 200 amp panel in the house. Both will be tapped in the meter can.

Load calc says 160 amps but potential draw is 300. If it was a overhead mast and you sized your conductors for 200amps you could pull 300 on them in the future if load was added. I'm just a little confused as to if that is legal and if 230 covers this in a way I'll be able to understand. Some code references or online docs would be helpful to get me pointed in the right direction. Thanks!
 
Basically it's like this.

If there is only one service disconnecting means the service conductors must be rated at least as high as the over current protection. 230.90(A).

If there is more then one service disconnect the conductors need only be rated as high as the calculated load, not the total of the over current protective devices. 230.90(A) Exception 3.

Yes that could mean the service conductors could be overloaded in the future but that is the responsibility of the electrician adding more load to make sure that will not happen.
 
I think this is a good example of the one of the reasons for exception 3.

Dennis8.jpg


Each of those meters supply a 100 amp main breaker panel, but the riser is obviously not good for 600 amps
 
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