Range Calc Question...prepping for exam

[xman1970]

I am little confused when comparing Col B and C of Table 220.55.

If I have (20) 6kW ranges; I calculate the product of 20(6kW) x .28 (per Col. B.)= 33.6kW. Do I stop there or do I need to compare the product of the Col. B. calculation to the value for 20 ranges in Col. C, which is 35kW? I appreciate your feedback. Jon

 

[RonPecinaJr]

Yes, I think you are right.

Note 3 says to add the sum (20 - 6kw ranges) and multiply by the demand factor of 28.

20 x 6kw = 120kw

120kw x 28% = 33.6kw

edit, and yes, you do need to compare to column C because on occasion the sum total in kw in column B is sometimes more than in the C column.

 

[xman1970]

Range calcs.....

Range calcs.....

Thanks Ron. Do I stop at 33.6kW or do I compare it with Col C?

 

[nakulak]

read note 3. you have complied with note 3, col C therefore does not apply (note the title at the top of the table)

 

[Dennis Alwon]

I believe in your case you may choose between the two methods. Not sure how one would answer this on a test if both answers were given as choices.

 

[xman1970]

Thank guys....

 

[augie47]

good luck with the exam
if you do well... atta boy! If not, balme the Forum.

 

[Dennis Alwon]

good luck with the exam
if you do well... atta boy! If not, balme the Forum.

Just remember it is Gus' fault if you don't do well.

 

[electricalperson]

range calculations are the most confusing part of service calculations for dwelling units. read the notes under 220.55 carefully. just remember col. C is in KW and not a percent

for example if you have one 12kw range you put 8kw in your service calculation instead of 12. it gets more confusing if you have multiple ranges of different wattages

its not too bad once you get the hang of it

 

[RonPecinaJr]

read note 3. you have complied with note 3, col C therefore does not apply (note the title at the top of the table)

Are you referring to:

(Column C to be used in all cases except as otherwise permitted in Note 3.)?


I believe that in Note 3 where it says "In Lieu of" that it means that if the total from Column B is greater than in Column C than you have the choice of either Column B or Column C.

 

[rhamblin]

I believe that in Note 3 where it says "In Lieu of" that it means that if the total from Column B is greater than in Column C than you have the choice of either Column B or Column C.

I am having problems with this also. If we are given the choice, on a master exam, are we to use the lowest possible demand factor calculation?

 

[mivey]

I am having problems with this also. If we are given the choice, on a master exam, are we to use the lowest possible demand factor calculation?

If the question asked for the lowest allowable, then yes. If it did not specify, either could be used becuase they are both allowable.

 

[Ken9876]

Try going to Electrial Contractor Mag. They have been running these calcs. for like two years now.

http://www.ecmag.com/index.cfm?fa=article&articleID=9958