Table 220.42: Lighting Load Demand Factors

17202 Views 8 Replies 5 Participants Last post by Gary Arthurs, Dec 23, 2015

paulgarett

Discussion Starter · Dec 18, 2013

I teach electrical construction. I have load calculation worksheets for residential service panels. These worksheets are calculated as follows:

The Lighting Load Demand Factor (Table 220.42) is calculated AFTER adding together the General Lighting Load per Table 220.12 and Small Appliance Circuit Load per 220.52(A) and (B).

Article 220.42, however, states: "The demand factors specified in Table 220.42 shall apply to that portion of the total branch circuit load calculated for GENERAL ILLUMINATION. They shall not be applied in determining the number of branch circuits for general illumination."

I interpret "General Illumination" to be the load calculated according to 220.12; not 220.12 plus 220.52. I can not find in the code book where "General Illumination" is defined. According to my load calculation worksheets, "General Illumination" includes the Small Appliance and Laundry Loads (220.52).

I think article 220.42 applies only to 220.12; not 220.12 plus 220.52.

Any suggestions or comments?
Thank you.

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Gary Arthurs

· #7 · Dec 22, 2015

Thank you!

Thank you!

I am working through Tom Henry's book "2014 NEC Calculations Exam Questions and Answers" and got stuck on page 193. Made no sense until I saw your post referencing 220.52(A) and (B)

Even still, while 220.52(A) and (B) indeed exist, the Code leaves the reader to "find" this. It seems a reference under Table 220.12 pointing to these sections would be helpful.

itsunclebill said:
You may be an expert, but the language in 220-52 (A) and (B) is pretty plain - add laundry and small appliance circuits to the general illumination calculation to calculate demand factors.

Most confusion in understanding a lot of the code book is people quit reading too soon.

220-52 is part of the section on calculations and as an "expert" you should be going over this with your students. How come you don't know about it? Like I said in the first response, it's pretty basic stuff.

I've been at this over 40 years and don't know it all yet. Swallow a little humble pie and admit you don't either - it'll go better.

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Gary Arthurs

· #9 · Dec 23, 2015

Thank you Barjack

Barjack said:
You are making this more complicated than it needs to be.

You get your lighting load from T.220.12 based on square footage and occupancy type.

Then, you get your SABC load from 210.11C.

Then, you apply the demand factors in T.220.42.

I think you're getting hung up on the fact that T.220.42 says "Lighting Load Demand Factors" but that you are allowed to include SABC's in it.

Your comments are helpful and appreciated.

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