A recent Mike Holt article on load calculations part 1 says not to take 125% for continuous loads when using table 220.12 (refers to Note 1 in this table). The article is based on the 2020 NEC, is this a code change ? I don't have a note 1 under table 220.12, unless it's in another spot.
Lighting @ 125% using table 220.12
- Thread starter cppoly
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- Lockport, IL
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- Semi-Retired Electrical Engineer
I have always treated the w/sf in that table as though any impact from continuous loading was already factored into the values shown in the table. I'll check my 2020 later, but I don't think this is a change.
- Location
- Lockport, IL
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- Semi-Retired Electrical Engineer
I don't think the code will say that explicitly. You have to read between the lines. Early in the design process, I will use the w/sf values to get an idea of the service size. Towards the end of the design process, I will have laid out all the light fixtures and I can actually count light bulbs. I use the 125% factor for the later, but not for the former. My reasoning is that the notion of w/sf is a hypothetical load, an estimate of what the load might eventually prove to be. It is not, in and of itself, a load. It is a number, a guess, and does not reflect any actual installation. It is an allowance that the code calls upon us to include, so that the final service will be sufficient for the user. They gave us the allowance, we use the allowance, and we don't treat the allowance as though it were a continuous load.
jaggedben
Senior Member
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- Northern California
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- Solar and Energy Storage Installer
Yes, it is a code change.
The new note in the 2020 reads:
It appears to me to be an actual clarification of rule, not just restating what used to be elsewhere in the code. But what charlie said is explicitly stated now in the 2020 NEC.
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