Exam Question

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Dennis Alwon

Dennis Alwon

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Location
Chapel Hill, NC
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Retired Electrical Contractor
I have always wondered why sometimes when a question on lighting and receptacle load for a dwelling is asked it is often different than what I am thinking.

I guess what I am looking for is when to determine to use small appliance branch circuit & laundry and when not to.

For example
What is the calculated load for the lighting and receptacle load of a 2000sq. ft dwelling?

2000 x 3 = 6000 then 3000 at 100 % & the rest at 35%

OR

2000 x 3 = 6000
2 small appliance branch circuit = 3000
1 laundry at 1500

Now we have 10,500 watts then 100% and 35%....

Which is correct. I believe I have seen this answered both ways. How would you word it to clarify
 
I just want to mention that in article 220 it says that the small appliance branch circuit & laundry loads are to be used in the lighting and appliance load

220.52 Small-Appliance and Laundry Loads — Dwelling Unit.
(A) Small-Appliance Circuit Load. In each dwelling unit, the
load shall be calculated at 1500 volt-amperes for each 2-wire
small-appliance branch circuit as covered by 210.11(C)(1).
Where the load is subdivided through two or more feeders, the
calculated load for each shall include not less than 1500 voltamperes
for each 2-wire small-appliance branch circuit. These
loads shall be permitted to be included with the general lighting
load and subjected to the demand factors provided in Table
220.42.
Exception: The individual branch circuit permitted by 210.52(B)(1),
Exception No. 2, shall be permitted to be excluded from the calculation
required by 220.52.
(B) Laundry Circuit Load. A load of not less than 1500 voltamperes
shall be included for each 2-wire laundry branch
circuit installed as covered by 210.11(C)(2). This load shall be
permitted to be included with the general lighting load and
shall be subjected to the demand factors provided in Table
220.42.
Click to expand...
 
ptonsparky said:
Shall be ‘Permitted to’ not just ‘shall be’.
Click to expand...


I know that but it is always used in the lighting & recep. load. Why wouldn't you... But that is not my point-- how does one tell what the correct answer would be. I am quite sure I have seen this answered both ways
 
I have always done it as you described in your second example. The calculation is based on the combined load of 10,500. Probably because its just easier to lump it all together as oppose to break it out. Its the same. Your taking the first 3kva @100% and the remaining at 35% either way its 5625. I think its just a math preference.
 
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I don't think so. In some questions the answer is given as either the way I did it first and other times the answer is done the other way.

My question is how is someone to know which way to do it so they are correct. Should the question be worded differently, if yes, then how would you word the questions
 
Dennis Alwon said:
I have always wondered why sometimes when a question on lighting and receptacle load for a dwelling is asked it is often different than what I am thinking.

I guess what I am looking for is when to determine to use small appliance branch circuit & laundry and when not to.

For example
What is the calculated load for the lighting and receptacle load of a 2000sq. ft dwelling?

2000 x 3 = 6000 then 3000 at 100 % & the rest at 35%

OR

2000 x 3 = 6000
2 small appliance branch circuit = 3000
1 laundry at 1500

Now we have 10,500 watts then 100% and 35%....

Which is correct. I believe I have seen this answered both ways. How would you word it to clarify
Click to expand...
I've always done it the 2nd way only because I mimicked the example in Annex D
 
There is a big difference between the way most of us would actually calculate the load for a real project (i.e., your second method) and what the author of the test question had in mind. For that, there is no way to guarantee getting a "correct" answer.
 
charlie b said:
There is a big difference between the way most of us would actually calculate the load for a real project (i.e., your second method) and what the author of the test question had in mind. For that, there is no way to guarantee getting a "correct" answer.
Click to expand...
Which is why test questions need to be more specific on exactly what they are asking, unless maybe they are multiple choice answers and only one of the choices is a possible legitimate outcome.

Use of proper NEC terminology in a question and in answers is a start in the right direction.

What is the calculated load for the lighting and receptacle load of a 2000sq. ft dwelling?

Could maybe be better written: what is the minimum general lighting load....
 
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