Dwelling unit demand load calculation based on 220.82

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julianov

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Hello everyone,

I have conducted demand load calculations using sections 220.42 to 220.56, resulting in a total of 157 A from the service entrance box. However, when applying section 220.82, the calculation yields 105 A.

Given that the house is located 500 feet from the service entrance box, it was decided to utilize (2) sets of wires: 3#400MCM+2/0G - 3"C.

My question is, since we are employing 2 sets of wires, is it permissible to apply the provisions of 220.82?

Feeder and Service Load. This section applies to a
dwelling unit having the total connected load served by a
single 120/240-volt or 208Y/120-volt set of 3-wire service
or feeder conductors with an ampacity of 100 or greater.
Click to expand...
 
It does say a "single set". I'm not sure why. An AHJ would have to clarify, you never know what they're going to get picky over.
Personally, I'm not sure why it would matter electrically for a load calc. Odd language or I'm missing something.
The 3w just means it has two hots and a neutral, not that it's exactly 3 wires; contrasts to 4w - 3ph with a neutral.
The real question is to upsize or to transform. Someone else would have to chime in on that.
 
That's the reason it says 'single set,' but I don't see any difference. Electrically, it's the same to have 1, 2, 3 or N sets.
 
You are not utilizing 220.82 for the conductors you mention; they are way oversized for either load calc method. However I think that doesn't prevent you from utilizing 220.82 for any other part of the installation, such as a breaker at either end or a panelboard fed by the circuit.
 
jaggedben said:
You are not utilizing 220.82 for the conductors you mention; they are way oversized for either load calc method. However I think that doesn't prevent you from utilizing 220.82 for any other part of the installation, such as a breaker at either end or a panelboard fed by the circuit.
Click to expand...
I believe he's sizing for Vdrop, it's a long run.
 
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