Lighting demand factor

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mparkstexas

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Hopefully someone can help me out on this,

I am a designer at an MEP firm and noticed that 220.42 list a demand factor for a restraunt (actually 'other') at 100%. However, almost every panel calculation or set of drawings I have ever seen has the lighting at 125%.

Can someone explain this? I asked around, and got acouple different responses.

Thanks in advance.
 
Lights are generally on all day. That is, if my math skills have not failed me completely (and this early on a Monday morning, it is hard to tell) :D more than 3 hours. So many will call this a continuous load. That brings the extra 25% to the party.

That said, I see a difference between counting up VA load by adding up the installed light fixtures, and using a value of 3 VA per square foot as taken from table 220.12. I would tack on an extra 25% in the first situation, but not the second.
 
charlie b said:
and using a value of 3 VA per square foot as taken from table 220.12.
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Does anyone actually use the 3VA/sqft in their designs? I've never encountered ANYONE who does. Glancing at the code it doesn't even seem as though this provision is optional, yet nobody is following it.
 
Caligula said:
Does anyone actually use the 3VA/sqft in their designs? I've never encountered ANYONE who does. Glancing at the code it doesn't even seem as though this provision is optional, yet nobody is following it.
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How many designs use less than 3VA/sqft actual? Those are the only designs in which the 3VA/sqft would appear in the calculations, as it is the minimum. Actual being over that value replaces it in the calculation.
 
I find most designs use way less than 3va/sqft for lighting. Most types of occupancies get stuck in the .8 to 1.2 va/sqft due to the various energy codes. I don't do residential or industrial so maybe it is different for those industries.
 
Caligula said:
I find most designs use way less than 3va/sqft for lighting. Most types of occupancies get stuck in the .8 to 1.2 va/sqft due to the various energy codes. I don't do residential or industrial so maybe it is different for those industries.
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I can't speak for those that don't use the NEC minimums in their calculations (not that I can speak for anyone who does either ;) ).

If the AHJ let's 'em slide, who am I to say they shouldn't :rolleyes:
 
I think the 3 watts a square is old school.The code should move to a lumens per square foot. It would be a much better reality check of what is needed for actual measurement of a safe minimum lighting standard. If you think about the new elctronic ballasts in fluorescents it is doubtful that any of them meet the 3 va standard, yet produce more light tthan is required to be safe.
 
Rockyd said:
I think the 3 watts a square is old school.The code should move to a lumens per square foot. It would be a much better reality check of what is needed for actual measurement of a safe minimum lighting standard. If you think about the new elctronic ballasts in fluorescents it is doubtful that any of them meet the 3 va standard, yet produce more light tthan is required to be safe.
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How would you use lumens in an Article 220 calculation?

3 VA/sq ft is a power calculation, not a light calculation. It has nothing to do with light levels.
 
3 VA/sq ft is a power calculation, not a light calculation. It has nothing to do with light levels.
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So how much power is neccesary for safe lighting? As the number would get smaller in regard to va required to power lighting, we go towards a "less is more concept". When was the last time the code actually gave any consideration to where the new "green" game is being played in regard to what the industry is doing?
 
The actual lighting fixtures are not selected.
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Granted, but the game is shifting to the "green" side, without getting political, I see it hitting the NEC.
 
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Rockyd said:
{quote]

Granted, but the game is shifting to the "green" side, without getting political, I see it hitting the NEC.
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It certainly will. I don't disagree with that. I am pointing out that services, feeders, etc. are calculated with VA. Without knowing the actual fixtures, there is no way to use lumens in an load calculation.

I also feel that light levels and efficiency belong more in the building code, not the NEC. JMHO.
 
Volta said:
And for residential purposes the 3 VA / sq ft provides for most receptacle outlet loads too.
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That is exactly what it is used for. That picks up the TV, radio, vacuum cleaner, etc. as well as all the lamps.

As far as using lumens, check out the lumens per watt on the incandescent lamps, fluorescent lamps, the CFLs, and now the LED lamps. There is no single calculation that can convert lumens to kW. Since the incandescent lighting is the most inefficient, why not use that as the base? :)
 
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