220.55 Note 3

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augie47

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Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
I have tried demonstrations for a class on the use of Note 3 using equipment in both Col A & Col B.
For example>: (8) 2.5kw units plus (9) 8.5 kw units (unless I made a mistake the result would be 34 kw). If I had the same number of units (17) at 12 kw the Col C result would be 32 kw/
Makes no sense.. 17 ranges all less than 12kw give you a higher number than 17 units at 12 kw.

Am I looking at this wrong ?
 

Smart $

Esteemed Member
Location
Ohio
I have tried demonstrations for a class on the use of Note 3 using equipment in both Col A & Col B.
For example>: (8) 2.5kw units plus (9) 8.5 kw units (unless I made a mistake the result would be 34 kw). If I had the same number of units (17) at 12 kw the Col C result would be 32 kw/
Makes no sense.. 17 ranges all less than 12kw give you a higher number than 17 units at 12 kw.

Am I looking at this wrong ?
I don't think you are looking at it wrong on the calculation side, but I do think you have speculated that the result of the lesser rated appliances should somehow have a lower demand. Maybe they should, maybe they shouldn't. I suppose one premise might be that lesser rated appliances are likely to be in use more often and/or have longer heating cycles than higher rated appliances.
 

augie47

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Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
I had (8) 2.5 kw so I used Col A for those 8 x 2.5 = 20 x .53 = 10.6 kw
(9) 8.5 Col B 9 x 8.5 = 76.5 x .35 = 26.8

37.4

I accidentally typed 34 but the confusion is still the same. Note 3 gives us 37 for 17 pieces of cooking equipment all less than 12 kw whereas if all 17 were 12 kw the load would be 32.
Maybe what Smart$ stated, but it just seems odd.
 

jumper

Senior Member
Whether $Smart is correct or it is some other reason IDK, but I tried something else and got similar results.

3 x 12kW (36kW total), Col C for 3 = 14kW
6 x 6kW (36kW total), Col B demand factor .43 = 15.48kW

~1.5kW different calculated load for the same total kW.:blink:
 

augie47

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Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
Note 3 states "In lieu of the method provided in Col C "..permissible"
would you take that to mean that you could elect to use either the Note 3 calculation or the Col C number for the equal number of ranges ?
 

jumper

Senior Member
Note 3 states "In lieu of the method provided in Col C "..permissible"
would you take that to mean that you could elect to use either the Note 3 calculation or the Col C number for the equal number of ranges ?

I would say yes.

For your 17 mixed ranges you get a smaller number using Col. C

For my 6 same ranges I get a bigger number using C over B.

I suppose you get to use the smallest given "in lieu of....".
 

Smart $

Esteemed Member
Location
Ohio
Note 3 states "In lieu of the method provided in Col C "..permissible"
would you take that to mean that you could elect to use either the Note 3 calculation or the Col C number for the equal number of ranges ?
I agree with jumper. You don't have to use Col A and/or B method and can opt to use Col C..
 
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