General Lighting Load Simplification

[bphgravity]

1. 220.12, 220.42, 220.52(A), 220.52(B), Annex D

2. Revise Text, Delete Text

3. Change "Unit Load" to 3.5 for Dwelling Units,

Change Table 220.42 "Dwelling Units", Under "Portion of Lighting Load" column, Change to "First 5000 or less at" and "Remiander over 5000 at". Under "Demand Factor" column, delete "35" leaving "100" for the first 5000...portion, and "25" for the remainder portion.

Delete 220.52(A) & (B) in total.

4. This change simplifies the General Lighting Load calculation. The resulting calculation is equivalent to the existing formula, without all the unecessary steps. The addition of .5 VA to the VA per Square Foot and the adjustment to Table 220.42 makes up the 4500 VA required for the sm app and laundry loads. For example:

"CURRENT CALCULATION"

1500 ft? at 3 = 4500 VA
2 sm app at 1500 = 3000 VA
1 laundry at 1500 = 1500 VA
TOTAL = 9000 VA

3000 VA at 100% = 3000 VA
9000 - 3000 = 6000 at 35% = 2100 VA
3000 VA + 2100 VA = 5100 VA NET LOAD

"PROPOSED CLACULATION"

1500 ft? 3.5 = 5250 VA
5000 VA at 100% = 5000 VA
5250 - 5000 = 250 at 25% = 62.5 VA
5000 VA + 62.5 VA = 5063 VA NET LOAD

EXAMPLE 2

"CURRENT CALCULATION"

6000 ft? at 3 = 18000 VA
2 sm app at 1500 = 3000 VA
1 laundry at 1500 = 1500 VA
TOTAL = 22500 VA

3000 VA at 100% = 3000 VA
22500 - 3000 = 19500 at 35% = 6825 VA
3000 VA + 6825 VA = 9825 VA NET LOAD

"PROPOSED CALCULATION"

6000 ft? at 3.5 = 21000 VA
5000 VA at 100% = 5000 VA
21000 - 5000 = 16000 at 25% = 4000 VA
5000 VA + 4000 VA = 9000 VA NET LOAD

 

[charlie]

Re: General Lighting Load Simplification

The resulting calculation is equivalent to the existing formula, without all the unnecessary steps.

Bryan, I don't agree and I don't see how the panel could agree either. Even your examples show different answers and you have no substantiation that shows you have a solid foundation for your calculations.

Sorry,
Charlie

 

[bphgravity]

Re: General Lighting Load Simplification

The slight reduction in net load resulting from this proposed change will not ultimately affect the final feeder or service calculation. In actuality, it makes the "standard" more in line with the "optional" method.

There is really no reason to line item the Small Appliance and Laundry loads when they can easily be incorporated back into the general lighting load.

In spirit with the current method, the larger the home, the more benefit you will recieve from the demand factoring. This is in line with the understanding that a larger home doesn't necessarily mean more general lighting load. A typical family of 4 will occupy and demand the same power requirements from the general lighting and appliance circuits whether they are in a 2000 ft? or 6000 ft? home. At least with this change, the increased loading of .5 VA per ft? will include the kitchen and laundry areas as they naturally grow as the home becomes larger. The only thing that typically changes is the heating and air conditioning loading.

So in reality, there is no change to the resulting calculation, its just a change on how you incorporate those loads. It reduces the number of steps. The 4500 VA are properly absorbed and demand factoring is simplified.

 

[charlie]

Re: General Lighting Load Simplification

Bryan, I suggest working more examples and going to extremes while comparing with both methods as they now stand. Along with that, include your second argument in the substantiation. In other words, how does this type of calculation compare with the loaded 12,000 sq. ft home and with the 800 sq. ft home that has the bare minimum amenities?

 

[George Stolz]

Re: General Lighting Load Simplification

But what if JW is right, and other (more than 2) SA circuits are to be included in the load calc?

That said, I like your proposal.

Edit: I like the idea - but it wouldn't hurt to write it clearer, and definutely include your second post in the substantiation.

[ September 15, 2005, 08:08 AM: Message edited by: georgestolz ]

 

[dillon3c]

Re: General Lighting Load Simplification

Originally posted by georgestolz:
But what if JW is right, and other (more than 2) SA circuits are to be included in the load calc?

That said, I like your proposal.

Well,I don't..(it suits me just fine.)

Hard enuff to recall most of these calculations,without having to open a book.

Bryan, *please* leave the calculations alone.. ( *please* )