computing the service load for a house what method do you use and why?

[zappy]

I used the common method in art.220 and got 176 amps. I then used the optional method and got 118 amps. I'm not sure if I did something wrong, it just seems like that's too much of a difference? I know using the optional method gives you a lower calc. but that much? I don't know which one to trust.

[bphgravity]

That sounds reasonable to me. In most (not all) cases th optional method will provide a lower load calculation. Many times, it can result in a reduced service size as it has in your case.

Since both (somehow) are considered to be acceptable methods to produce the minimum permitted service size, the use of one or the other is purely a design consideration.

[LarryFine]

Zap, the decision these numbers leave you is whether to install a 150 or 200a service. I find that it costs almost nothing more for the 200a.

I suggest basing this particular choice on your gut feelings, the quantity of circuits, and the nature of the electrical loads.




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