Question on Calculation on Heaters, Mike Holt Books

[brother]

I was looking at mike holts NeC exam Prep 2008 BOOK, page 319 on commercial calculations. I noticed they had a heater at 10kw, but the minimum he gives is 15,000 VA. Where is this found where it has to be a minimum of 15,000 VA ??? I check the code articles 220.51 and 220.60 and theres no mention of it that I see.

 

[Smart $]

I was looking at mike holts NeC exam Prep 2008 BOOK, page 319 on commercial calculations. I noticed they had a heater at 10kw, but the minimum he gives is 15,000 VA. Where is this found where it has to be a minimum of 15,000 VA ??? I check the code articles 220.51 and 220.60 and theres no mention of it that I see.

Can't say offhand because I don't have the book....

Perhaps it has to be a minimum of 15kVA to exceed that of the AC (only the greater of the two is generally used in the calculations).

 

[radiopet]

I do have that book and I was in the Video as well....I will have to look as I simply can't remember and it was probably a BOOK thing and not discussed during the actual video filming of the DVD's. I will have to pull the book from my library and see....

 

[brother]

Ok, let me ask it this way. Is there a MINIMUM for fixed heating equipment in VA when doing calculations??

 

[Smart $]

Ok, let me ask it this way. Is there a MINIMUM for fixed heating equipment in VA when doing calculations??

None that I'm aware of.

 

[radiopet]

Ok, I looked at the book and it simply appears to be a type as the image gives the load as 10KW and it appears it was missed and 15KW should have been in the image. Either way it appears to simply be an editorial error. I believe the image was probably not changed when Mike determined he wanted to use 15KW instead of 10KW.

I don't see anything (on page 319 ) that implies any minimum sizing. Those values are simply for the examples being shown.

 

[brother]

Ok, I looked at the book and it simply appears to be a type as the image gives the load as 10KW and it appears it was missed and 15KW should have been in the image. Either way it appears to simply be an editorial error. I believe the image was probably not changed when Mike determined he wanted to use 15KW instead of 10KW.

I don't see anything (on page 319 ) that implies any minimum sizing. Those values are simply for the examples being shown.

Thanks for ressponding back. I just wanted to make sure I wasnt missing anything in the code for minimum volt amps for heaters, because I couldnt find it. So its my understanding so long as multiply the 125% for the current sizing of the heaters, is all I really need to be concerned about.

Is there a place to send info to Mike Holt about the errors??

 

[Smart $]

Thanks for ressponding back. I just wanted to make sure I wasnt missing anything in the code for minimum volt amps for heaters, because I couldnt find it. So its my understanding so long as multiply the 125% for the current sizing of the heaters, is all I really need to be concerned about.

Is there a place to send info to Mike Holt about the errors??

For the purpose of service or feeder calculations, fixed electric space heaters are generally only calculated at 100% [ref: 220.51]. It is only for branch circuit sizing they are considered at 125% [ref: 424.3(B)]. Because 220.51 does not permit a service or feeder conductor to have a rating less than the largest branch circuit supplying a heater or heaters, you'd have to check to make sure the service or feeder conductor meets the 125% of the largest branch circuit.

Given an example of one fixed electric space heater having a connected load of 10kVA, the service or feeder conductor cannot be calculated to be any smaller than 12.5kVA.

Again without having Mike's book, I cannot tell if perhaps this might be the minimum being referred to.