[paulgarett]

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.

 

[itsunclebill]

There is an excellent residential calculations Excel spreadsheet available at Mike Holt's website - look under "free stuff".

Looking this over should answer your questions.

Also, look at the examples for calcs in the code book - example D1(a) in the 2011 NEC

The square foot calc for lighting, small appliance branch circuits, and the laundry circuit are lumped together to get the "general lighting demand load".

This is pretty basic stuff and if you aren't up on it I'd suggest you go through a review class yourself if you're teaching people.

 

[wildleg]

what he said ^. or better yet, buy a mike holt cd - it walks you through the entire section step by step

 

[paulgarett]

I am an expert at what I do. I am interpreting the code book as I read it. So maybe Mike Holt (I've read many of his books) may be wrong; or is simply following the example in the Annex of the NEC.

Read Article 220.42. The title of this code is "General Lighting." It states, "The demand factors specified in Table 220.42 shall apply to that portion of the total branch-circuit load calculated for general illumination.

The code does not define "General Illumination." The only place in the code where General Illumination is defined somewhat is Table 220.12, footnote 'a', see 220.14(J), which states general lighting load includes all general use receptacles, outdoor outlets, and basement/garage/accessory building outlets.

So......I am interpreting the code just as it says. I believe Table 220.42 does not include Small Appliances and Laundry load.

I see the examples in the Annex of the code. The demand factors include the small appliance and laundry load.

I think the code should be revised or edited to be more clear. Article 220.42 should state the demand factors include the small appliance load, not just "General Illumination."

I should write the code making panel. Need to find that form.

 

[itsunclebill]

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.

 

[paulgarett]

Dang, your right. Most students don't have the patience to read this stuff; so they probably are rubbing off on me a little. But thanks for your humble response.

 

[Gary Arthurs]

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.

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.

 

[Barjack]

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.

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.

 

[Gary Arthurs]

Thank you Barjack

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.