LIGHTING LOAD DEMAND FACTOR

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vkvgpal

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We all know lighting load is considered as one of continuos loads, and we have to design the branch circuit and the over-current protection at 125% of design load(NEC 210.19.A.1).I know the fact in it, and I can understand the practicality. But I fail to observe in the NEC or IEEE standards, stipulating that, the lighting load demand factor to be considered or written down at 125%, while calculating building or part of the building load, contrary to Table 220-11 of NEC 2002 OR Table 220-42 of NEC 2005. I was told that most of the counties are requiring this for permit issue. May anyone help me to have the NEC or any appropriate mandatory building codes reference or National/International standards that specifically stating the demand factor of 125% to be used for lighting loads calculations? Thanks
 
Re: LIGHTING LOAD DEMAND FACTOR

Originally posted by vkvgpal:
We all know lighting load is considered as one of continuos loads...
We do? That's a judgement call by the electrician or Authority Having Jurisdiction, depending on the area and type of occupancy.

May anyone help me to have the NEC or any appropriate mandatory building codes reference or National/International standards that specifically stating the demand factor of 125% to be used for lighting loads calculations? Thanks
There isn't one, that I know of, in the NEC. :)
 
Re: LIGHTING LOAD DEMAND FACTOR

I don't know that bathroom lights would be considered a continuous load unless it takes you three hours to read the sunday paper.
 
Re: LIGHTING LOAD DEMAND FACTOR

Originally posted by petersonra:. . . unless it takes you three hours to read the sunday paper.
LMAO :D :D

NEC 220.12 gives us the minimum allotment that we must include for lighting loads. We are not required by any NEC rule to "biggie size" that allotment by 125%.
 
Re: LIGHTING LOAD DEMAND FACTOR

I think you are confusing branch circuit calculations with feeder and service calculations.

My kids often leave the bathroom lights on for 3 hours (even if nobody is home:), but it would be very rare for them to leave every single light in the house on for 3 hours.

Depending on the size and nature of a business, I think the entrie lighting load could go either way (continuous or non-continuous).

Steve
 
Re: LIGHTING LOAD DEMAND FACTOR

Originally posted by steve66: I think you are confusing branch circuit calculations with feeder and service calculations. . . . Depending on the size and nature of a business, I think the entire lighting load could go either way (continuous or non-continuous).
You get the lighting load from the Branch Circuit calculations. When you include that load with the feeder or service loads, you may be able to reduce the number by using the demand factors of Table 220.42. But nowhere in the process do you factor in 125% of the general lighting load.

To be specific, in a residence you take 3 VA per square foot, and call it "general lighting load." My take on this is that the fact that lights might be on all day is taken into account, in the selection of "3 VA per square foot" as the general lighting load. We are allowed to add that value to certain receptacle loads (e.g., Small Appliance and Laundry loads). But you do not multiply the total by 125%, before you look at the demand factors in Table 220.42. You don't even multiply the lighting portion by 125%, before adding in the SA and laundry loads.
 
Re: LIGHTING LOAD DEMAND FACTOR

Hi guys,

While I am thanking for your enthusiastic participation in this discussion, I am bound to clarify that when I mentioned 'continuous load', I preciously mean commercial, Institutional, and Industrial lighting loads.(Not residential). Go on please. Thanks.
 
Re: LIGHTING LOAD DEMAND FACTOR

Originally posted by charlie b:
My take on this is that the fact that lights might be on all day is taken into account, in the selection of "3 VA per square foot" as the general lighting load.
Given the lack of text regarding continuous loads in these related sections, I would tend to agree.

While I am thanking for your enthusiastic participation in this discussion, I am bound to clarify that when I mentioned 'continuous load', I preciously mean commercial, Institutional, and Industrial lighting loads.(Not residential).

I kinda figured. But the reasoning holds.

Pal, welcome to the forum. :)
 
Re: LIGHTING LOAD DEMAND FACTOR

When I said "branch circuit calculations", I should have said "actual connected load on a branch circuit". I didn't mean to imply you multiply any Article 220 calculation by 125%. I simply meant you limit the actual connected load to 1920VA on a 20A circuit.

Steve
 
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