Mike's Residential load calc spreadsheet

[Scott K]

I did a residential load calc on Mike's spreadsheet on his site here. When I enter the info for the standard calc it calls for a 400 amp service. When I select the optional calc it changes to a 250 amp service. Am I missing something?

 

[jumper]

Optional method is almost always smaller.

Here is an example: http://www.ecmweb.com/code-basics/dwelling-unit-feederservice-conductor-calculations

 

[Scott K]

Thanks Jumper, I know the optional calc is usually lower, but 150 amps lower? I feel like that's too much of a spread. I guess it's time to break out the calculator and do both manually. Thanks again for the assistance!

 

[jumper]

Thanks Jumper, I know the optional calc is usually lower, but 150 amps lower? I feel like that's too much of a spread. I guess it's time to break out the calculator and do both manually. Thanks again for the assistance!

Does not really surprise me. Look at the example I posted. It went from 143A to 106.5A.

 

[lielec11]

This is an excerpt from the sample calculations provided. It appears to be from 2005:

Feeder and service conductor size. 400A and less: For 3-wire, 120/240V, single-phase systems, size the feeder or service conductors according to Table 310.15(B)(6). For all others, use Table 310.16. Size the grounded (neutral) conductor to the maximum unbalanced load (220.22) per Table 310.16.

Is this still part of the current code? If so, which table is Table 310.15(B)16 now? In 2004, Table 310.16 is the CURRENT 310.15.(B)16 so what is this other table they are referring to for services under 400A? I don't see where a 1 AWG CU feeder is good for 150A.