Light branch circuit demand factor

[hhsting]

I have commercial car wash facility light is going to be more than three hours operational. Engineer calculated total connected load of branch circuit light in facility to be X fed from panel A. He is saying demand load for panel A is (X)(100%) with 100% demand factor. He is using that calculation to see if the main breaker and bus in the panel board A is not overloaded and to size feeder to panel A.

Two questions:


1. Is their a code section that say connected load has to be multiply by 125% to get light demand load anywhere to see if panel A bus or main breaker is overloaded?

2. Is their a code section that say connected load has to be multiply by 125% to get light demand load for sizing feeder to panel A?


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[tom baker]

Yes there is a code section and I would suggest you start with the definition of load, continuous and then go to Art 220.
More importantly, is to understand why a continuous load is multiplied by 125%

 

[hhsting]

Ok more than three hours operational load is continuous section 100 definition of continuous so my light load is continuous. I have X kVA of light connected load panel A. According to 220.40 calculated load of feeder or service shall be not less than the sum of the loads on the branch circuits supplied as determined by part II of this article after any applicable demand factors permitted by part III or part V.

So part III section 220.42 and table 220.42 says 100% demand factor for all other occupancy for light branch circuits which is my car wash facility.

So feeder to Panel A is sized 100% per 220.40 and 220.42. I don’t see 125% as you say it’s in code.

Only sections found was 210.19(A), 210.20 and 215.2, 215.3 to size based on continuous load but not 220.

Is 220 contradicting 210, 215? Can you please elaborate on where in 220 is light demand factor is 125%? Please

All references above are from NEC 2014

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[tom baker]

Feeder is not 125% this is in the load calc, based on the lighting tables in Art 220 I made a mistake, so just take the lighting load and multiply by 125%. The 2020 NEC has changes for energy efficiency. Lighting loads, can be significant! In Washington State are based on energy codes, example 1 W/sq ft instead of 3

 

[hhsting]

Ok but One article says based on demand factor while other says based on continuous and non continuous load. If my demand for light is 100% based on 220.42 then how come I have to look at continuous load and take 125%. One section say 100% the other 125%. Why is discrepancy between 220.40 and 215.2(A)(1), 210.19(A)(1), 230.42(A)(2)(A)(1)?


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[david luchini]

Ok but One article says based on demand factor while other says based on continuous and non continuous load. If my demand for light is 100% based on 220.42 then how come I have to look at continuous load and take 125%. One section say 100% the other 125%. Why is discrepancy between 220.40 and 215.2(A)(1), 210.19(A)(1), 230.42(A)(2)(A)(1)?

That's not a discrepancy. It's two different sections telling you two different things. You have to apply them both.

 

[kwired]

Ok but One article says based on demand factor while other says based on continuous and non continuous load. If my demand for light is 100% based on 220.42 then how come I have to look at continuous load and take 125%. One section say 100% the other 125%. Why is discrepancy between 220.40 and 215.2(A)(1), 210.19(A)(1), 230.42(A)(2)(A)(1)?


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This has always been somewhat confusing. But keep in mind art 220 lighting load - especially from tables is a conservative estimate and also includes other loads in some instances. So if you happen to be using a table value of 3 VA per square foot - that is an NEC estimate and not necessarily your actual load. Those values have been around for some time and actual lighting these days is normally more efficient than when those values were determined - though as mentioned apparently 2020 NEC is finally recognizing that, haven't check into it yet.