Nothing in the NEC states to use the next largest if omitted, but 220.60 states "Where the motor is part of the noncoincident load and is not the largest of the noncoincident loads, 125% of the motor load shall be used in the calculation if it's the largest motor." It appears you can still use the AC as the largest motor load.
Oops. I meant "no heat, just a/c" vs "no a/c, just heat." With non coincident loads, either one case or the other always applies. So by choosing the larger load, you guarantee that all cases are covered.
Logic does. If the A/C is largest, and you are omitting it because it's non-coincident with some other larger load, then the next largest motor is the largest motor that is being included in the calculation.
OK, that's the 2020 NEC version, the 2017, 2023, and 2026 First Draft versions are all different from that. I don't even know exactly what the above means. Here's a rational method:
Only for the case it is operating. For the case it is not operating, its presence obviously doesn't affect the loading.
It's not deleted altogether, it is just contributing to the possibility of being the largest motor and thereby getting an extra 25% only for the case when it is operating.
Simply Electrical has a duplex calculations video and he omitted the AC against the heat and used the AC as the largest motor load x 25%. It makes sense but it would be nice if the NEC stated a rule on this.
Which makes sense, "Simply Electrical's" method or my method? "Simply Electrical's method" gives a slightly higher value, so it's conservative. But I'd say my method obviously makes more sense.
It appears to me that list item (2) should only be for branch circuits. Keeping feeders and services in item (2) creates a different standart for services and feeders as compared to the standard set in item (1).
That's not a problem, just a case of unnecessary overlap. "One of the following" means that either condition alone suffices. The fact that for a feeder or service, condition (2) implies condition (1) doesn't change anything.
I think I disagree. For example with smart panel apps and such, it's possible that two loads on different branch circuits could be prevented from being used simultaneously. It might be redundant with 220.70 but perhaps not, if it can be accomplished with listed equipment that happens not to be a listed EMS.
I think Don's point is just that including feeders and services in (2) is redundant, as if the following clause in (2) holds, then the clause in (1) would certainly hold, so it's already covered.
I see a conflict.
It says "one of the following" not "both of the following". It's OR, not AND. No conflict.
What if the non-coincident loads actually are "both of the following" ? Say, heating and cooling that are unlikely to be used simultaneously, and two EVSE branch circuits controlled by an EMS. All on the same feeder.
Well, if there's an EMS, for the EVSEs we don't need to consort with 2026 NEC First Draft 120.6. A different sections covers that. That leaves the heating and cooling, which would be on different branch circuits, so (2) would not apply. And if the heating and cooling are unlikely to be in use simultaneously, then (1) applies, and they are non-coincident. So we use 120.6 for the heating and cooling.
If it is truly an OR, then (2) is redundant and not needed when speaking of just feeders and services, complying with (2) means you have automatically complied with (1), therefore (2) is simply verbose text.
