2002 Optional Calculations 220.34 & 220.36

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mweaver

Senior Member
220.10 :
"The computed load of a feeder or service shall not be less than the sum of the loads on the branch circuits supplied, as determined by Part I of this article, after any applicable demand factors permitted by Parts II, III, or IV have been applied."

Upon reading 220.10 it appears to me that in computing a commercial service (by the optional method as per 220.34 and 220.36) you would still apply Part I of Article 220 as well as 215.2(A)(1) and 230.42(A) in determining you connected load.

Specifically, The connected load would be made up of all of the requirements of Article 220 Part I and 100% of noncontinuous load and 125% of continuous load (215.2(A)(1) & 230.42(A) .

Am I interpreting this correctly?

Any feedback would be appreciated.

Thanks in advance

mweaver
 

charlie b

Moderator
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Location
Lockport, IL
Occupation
Retired Electrical Engineer
Re: 2002 Optional Calculations 220.34 & 220.36

Originally posted by mweaver:. . . The connected load would be made up of all of the requirements of Article 220 Part I and 100% of noncontinuous load and 125% of continuous load (215.2(A)(1) & 230.42(A).
First of all, optional calculation methods are available for dwelling units, schools, and restaurants. There is no optional method for a ?commercial service.? But to address your specific question, neither 215.2(A)(1) nor 230.42(A) comes into the picture, when calculating load. First you calculate the load, then add the extra 25% for the continuous portion just before you select the feeder or service conductors.
 

mweaver

Senior Member
Re: 2002 Optional Calculations 220.34 & 220.36

Charlie B,

Thanks for the reply,

What about Part I of Article 220 in the calculation of loads by the optional method for a school(220.34) and a new restaurant (220.36)?

Would Part I apply to the calculation of those loads?

Thanks

mweaver
 

charlie b

Moderator
Staff member
Location
Lockport, IL
Occupation
Retired Electrical Engineer
Re: 2002 Optional Calculations 220.34 & 220.36

Well, yes, sort of. Neither 220.34 nor 220.36 explicitly tells you to go to Part I to add up loads. Each gives you a table of demand factors that can be applied to that specific occupancy. 220.34 even muddies up the waters a bit by giving you a list of loads to add up: ?all of the interior and exterior lighting, power, water heating, cooking, other loads, and the larger of the air-conditioning load or space-heating load within the building or structure? I am sure that there is nothing in Part I that does not also fall into this list. But as you pointed out already, 220.10 tells you to start with Part I, to get the loads, then go to Parts II, III, or IV to get demand factors.
 

bob

Senior Member
Location
Alabama
Re: 2002 Optional Calculations 220.34 & 220.36

Charlie
Where does it say that you add 125% cont. load
to the service. I do not seem to be able to find it.

[ December 29, 2003, 04:08 PM: Message edited by: bob ]
 

charlie b

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Staff member
Location
Lockport, IL
Occupation
Retired Electrical Engineer
Re: 2002 Optional Calculations 220.34 & 220.36

The same articles cited in the original question: 215.2(A)(1) for feeders and 230.42(A) for service. Adding 25% of the continuous load (not 125%) is part of the process of selecting the conductor size.
 

mweaver

Senior Member
Re: 2002 Optional Calculations 220.34 & 220.36

Charlie b,

Thanks for the response. I just wanted someone to agree with my thinking regarding 220.10.

It seems very clear to me. To calculate with the optional method you must compute the loads as per Part I and add the applicable demands of Part III. Those loads (prior to demands) would be subject to continuous load scrutiny.

Thanks

mweaver
 
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