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Residential service load question

Sifu

Sifu

SAWHORSE
Joined
Sep 3, 2011
Messages
2,813
I ran across this example and I am confused. The min. required ampacity for the conductors does not included the load from the continuous duty appliances. You see the min. size is derived from line 14, disregarding line 15. Is this correct? If so, why even ask for the data?
 

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  • Residential service load calc form inc. vehicle charger example.pdf
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What is the source of that worksheet? It seems not to be following the NEC on the lines you've identified.

First, my reading of the worksheet is that loads noted on Line 15 should already be noted above (this could be made more explicit). I.e. Line 15 should mean "of the load calculated on Line 14, this portion is continuous." It's not clear to me that is how the worksheet was filled out in this case.

Second, the portion of the service load which is continuous matters (other than the unusual case of 100% rated service OCPD). Then the service entrance conductors need an ampacity that includes an extra 25% of the continuous load, as does the service OCPD in the case of a single OCPD. So the line 16 formula on the worksheet is wrong.

Cheers, Wayne
 
The source is an AHJ. Many are being installed, and more and more are being required. I have been wondering how the increased loads affect the service and I happened across this. I don't know when it was produced, but it is identical in the data, albeit in a different order to this one from LADBS. Using the same data, the result without the load for the EV charger is the exact same on both, but when I fill in the field for the EV charger on the LA form, I get a larger service. Which is what I came up with when adding it in to the local form, only the local form seems to not use it.

1684347849109.png
 
For dwelling units, the optional method in NEC 220.82 usually gives a smaller result than the Standard Method.

If the 22,800 VA is an EVSE, then on the form in the OP it should have been listed on line 10. Line 14 is informative to note that some of the load incorporated in Line 13 is continuous. And the Line 15 formula should reflect that, as Line 13 plus 25% of Line 14.

But what sort of EVSE is 22,800VA? That's 95A @ 240V. An individual J1772 EVSE is limited to 80A, so it would have to be two or more EVSEs. Even so, I don't see any reasonable combination of standard size EVSEs that would give you 95A. The standard settings are 16A, 20A, 24A, 30 or 32A, 40A, and 48A, for installation on 20A, 25A, 30A, 40A, 50A, and 60A circuits, respectively. [I guess the 95A could be after the 125% factor, which would make it 76A, and that could be (1) 16A and (2) 30A, for example.]

Cheers, Wayne
 
This is a form I came across that was already filled out. I have no idea whether it is an EVSE or EVcapable, or EVready, or where they get the load, just using the example I found. My real question is how does it get incorporated into the load calc....where does it get plugged in? The LA form includes it in the "other loads" and employs no demand factor, the form in the OP apparently doesn't count it at all.
 
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