Lighting Diversity

[ctrane]

I am in the design of a church with classrooms. The architect has declared the building a "Place of Worship." Under this classification, can I apply any diversity to my lighting load? Right now the load is at about 14kVA, and it would be most helpful to lighten this number. Any help will be most appreciated.

 

[petersonra]

Re: Lighting Diversity

Just curious. why would you want to reduce your calculated load? The only reason I can think of is to reduce your service size, and the plain facts are that no matter what you start with you will need more down the road. if you cheat yourself going in you will pay much more later to upgrade.

 

[ctrane]

The reason is is that originally there were two buildings on site. For these two buildings, the utility place a 150kVA Transformer to feed these two buildings. Then, one of the buildings burned down, and is now being replaced. I was hoping that the load would be low enough so that the original transformer could service both these buildings again. That is the reason I am trying to find some diversity on the lighting.

 

[bob]

Thr utility will use its own method to size the transformer. Your caculations
are not used to size the transformer. You say the load is 14 kva. Thats a long way from a 150 kva.

 

[ctrane]

Yes 14kVA is a long way off from 150kVA, but I also added that this transformer is serving two buildings. The other building is an existing 600A service, which leaves me roughly another 600A for the building in question. I am fast approaching 600 as is, and some HVAC is still to be added, that is the reason I am asking to find some diversity on the lighting.

 

[charlie b]

Re: Lighting Diversity

Right now the load is at about 14kVA, and it would be most helpful to lighten this number.

I infer that interior area of the building is 14,000 square feet. Is that right? Did you get the 14kVA from Table 220.12, using 1 VA per square foot?

If you did, I think there is nothing you can do to lower (I'll avoid your pun of saying "lighten" ) this number. There are no demand factors for this type of building.

 

[steve66]

I agree there is no way to reduce the 14000VA lighting load, but 600 amps may be higher than you need to use for the other building. If it has a demand meter, you might be able to use the actual demand from the last year as its load.

I also agree with a previous post - around here, the transformer is usually owned by the utility, and they usually have no problem sizing it at about half the load the NEC requires.

 

[ctrane]

Here is another question of the same style. Suppose you have Panel 1, and it feeds Panel 2 (which is MLO). Do you add the receptacle load from Panel 2 to Panel 1 and then apply diversity, or do you apply diversity to Panel 2 exclusively, and then size the breaker accordingly in Panel 1, and count that load from Panel 2 at 100%?

 

[charlie b]

Please don't ask the same question in more than one place. The topic of demand factors for subpanels should be addressed in your other thread:
http://www.mikeholt.com/codeForum/viewtopic.php?t=25782

Let's restrict this thread to its original topic of lighting calculations.

 

[bob]

I am fast approaching 600 as is, and some HVAC is still to be added, that is the reason I am asking to find some diversity on the lighting.

You should not try to reduce the demand of any of you electrical loads. Caculate it the way the code requires. The loading on the utillity transformer should not be a reason the search for methods to reduce your caculations. The NEC is clear about how you are to proceed in caculating your load. What are you trying to achieve by holding the loads down? As Steve said, you may be able to get the actual maxium demands for the other buildings from the utility.