which one should I apply concerning Kitchen equipment

[Diaz. jesus]

I found this question in a Master electrician skills test(KJ Keller)

In an eight-unit apartment building, each kitchen contains a 3.5 kw, 240 v electric range.
The demand load for the electric service to the building MUST include an ALLOWANCE for the minimum demand load of all the ranges, which would be which of the following:
a) 28 b)21 c)14 d)7.5

According to the author the answer is 21 kva Reference section 220.17 ? and list a demand factor of 0.75 for four or more appliances
28x3x0.75=21, which I think relates to 220.53 Appliance load, that specifies OTHER THAN electric ranges, clothes dryers, etc.

But according to a Mike holt example on Electrical formulas with sample calculations When using the optional calculation method , the calculated load for the appliances that are fixed in place according to T 220.84, for 8 units we should use 43 %.

Finally, When we should use T 220.55 , if for 8 ranges, 3.5 kw , Column B we should use a Demand factor of 36 %.

Please, give me some explanation about the rules I must follow in order to get it right.

Jesus

 

[Smart $]

Appears to me you already have a correct understanding... :blink:

 

[Neal Burdick]

My 2008 or 2011 NEC does not contain a section 220.17.

You are correct that 220.53 would not apply to ranges as they are specifically exempt from that code section.

If an exam question does not specifically state "using the optional method" then IMO Table 220.55 should be used for any range calculation.

With that being said my answer would be 3.5 X 8 X 36% = 10.08 kW which is not among the choices given.

If the question read "using the optional method" then I would agree with Mike Holt's calculation of 3.5 X 8 X 43% = 12.04 kW

Neal Burdick
Electrical Plans Examiner

 

[Dennis Alwon]

Diaz the demand factor for 8 units at 43% according to mike holt is for service loads & feeder loads not ranges. I agree with Neal above that the answer should be 10.8kw for the ranges

 

[Smart $]

Diaz the demand factor for 8 units at 43% according to mike holt is for service loads & feeder loads not ranges. I agree with Neal above that the answer should be 10.8kw for the ranges

The OP problem referred to demand load for the electrical service. Table 220.84 only applies to service and feeder loads for multifamily dwelling units. I do not see where you felt the need to reiterate.

And I believe he is aware that all provided answer choices for the OP problem are incorrect, including the author's supposedly correct answer. He was looking for confirmation to his suspicions, or seeking a better understanding if he was incorrect. Only the former was necessary.