calculations

[mannyb]

It only has exisitng lighting. I am taking a stab at the calculations

This is Existing at The warehouse is basically empty.
22-1000w fixtures lighting EXISITNG
20-120v recptacles ( new ) Non cont ADD
4- welding 12.3kw each 230v 33a 3p Non ADD
air compressor 230v 25a 3p motor load ADD
MORE TO BE ADDED

Attempt at calculation (Let Me know What I am doing wrong Please )

general lighitng 22,000va
receptacles 20x180va = 3600va
compressor motor 25ax 230v x 1.73 = 9,930VA
Welders 12.3 VA x4 = 49200VA
Total VA = 84730/240x1.73= 204A

The general lighting is only thing original. I would like to also figure load. Am i going in right direction with Calculations

 

[mannyb]

calculations

I have a building with lighting only thing exisiting.
22-1000w fixtures lighting EXISITNG
20-120v recptacles ( new ) ADD
4- welding 12.3kw each 230v 33a 3p ADD
air compressor 230v 25a 3p motor ADD
MORE TO BE ADDED

Attempt at calculation with info on equipment (Let Me know What I am doing wrong Please )

general lighitng 22,000va
receptacles 20x180va = 3600va
compressor motor 25ax 230v x 1.73 = 9,930VA
Welders 12.3 VA x4 = 49200VA
Total VA = 84730/240x1.73= 204A

The general lighting is only thing original. Am i going in right direction with Calculations. The amperage seems little high.

 

[JFletcher]

It only has exisitng lighting. I am taking a stab at the calculations

Existing The warehouse is basically empty.
22-1000w fixtures lighting EXISITNG
20-120v recptacles ( new ) Non cont ADD
4- welding 12.3kw each 230v 33a 3p Non cont ADD
air compressor 230v 25a 3p motor load ADD
MORE TO BE ADDED

calculation (Let Me know What I am doing wrong Please )

general lighitng 22,000va
receptacles 20x180va = 3600va
compressor motor 25ax 230v x 1.73 = 9,930VA
Welders 12.3 VA x4 = 49200VA
Total VA = 84730/240x1.73= 204A

Your load calc is way high due to the fact you have calculated 4 welders running wide open at a 100% duty cycle. Dunno what they are fabricating, but I think it would be unlikely that you'd see even the equivalent of one welder running continuously wide open... or 2 running wide open (max amp setting) 50% of the time, or all 4 welders running 50% amperage half the time...

Not sure what demand factor you can use for multiple welders but I'd think it down around 25%.

 

[jumper]

It only has exisitng lighting. I am taking a stab at the calculations

This is Existing at The warehouse is basically empty.
22-1000w fixtures lighting EXISITNG
20-120v recptacles ( new ) Non cont ADD
4- welding 12.3kw each 230v 33a 3p Non ADD
air compressor 230v 25a 3p motor load ADD
MORE TO BE ADDED

Attempt at calculation (Let Me know What I am doing wrong Please )

general lighitng 22,000va
receptacles 20x180va = 3600va
compressor motor 25ax 230v x 1.73 = 9,930VA
Welders 12.3 VA x4 = 49200VA
Total VA = 84730/240x1.73= 204A

The general lighting is only thing original. I would like to also figure load. Am i going in right direction with Calculations

Just off the top of my head:

Lighting is first figured by sq ft per T220.12(?) and then compared to actual.

Actual will be off ballast info, not bulb wattage.

Largest is used and is considered continuous.

Yeah, 180VA per duplex.

Lighting and receptacles then get calced per 220.42 and maybe 220.44 also. Depends.

Welders usually have duty cycles allowing for a reduced calc, but 4 x max works.

Compressor-is 25A FLA or MCA?

These are just the first things that popped into my head.

 

[jumper]

Your load calc is way high due to the fact you have calculated 4 welders running wide open at a 100% duty cycle. Dunno what they are fabricating, but I think it would be unlikely that you'd see even the equivalent of one welder running continuously wide open... or 2 running wide open (max amp setting) 50% of the time, or all 4 welders running 50% amperage half the time...

Not sure what demand factor you can use for multiple welders but I'd think it down around 25%.

Welders are a combo of duty cycle and how many, regardless, as you said- 4 x max is overkill.

 

[JFletcher]

See your last thread starting at post #25 for answers to this question:

http://forums.mikeholt.com/showthread.php?t=188850&p=1883986#post1883986

Unless there are 4 guys simultaneously laying fill in 1" steel, all day long, I'd use maximum of what one welder uses, or ~12,500VA. That frees up 37,000VA from your calculation right there. Talk to the owner to see what he is planning on welding is another approach.

 

[jumper]

See your last thread starting at post #25 for answers to this question:

http://forums.mikeholt.com/showthread.php?t=188850&p=1883986#post1883986

Unless there are 4 guys simultaneously laying fill in 1" steel, all day long, I'd use maximum of what one welder uses, or ~12,500VA. That frees up 37,000VA from your calculation right there. Talk to the owner to see what he is planning on welding is another approach.

OP actually should go to 630 and do it correctly, not guess.

OP just needs to know if these are arc or resistance welders and duty cycle.

 

[JFletcher]

OP actually should go to 630 and do it correctly, not guess.

OP just needs to know if these are arc or resistance welders and duty cycle.

True. I dont have the 17 NEC, nor mine in front of me... is this page accurate?:

http://www.codebookcity.com/codearticles/nec/necarticle630.htm

"You can apply standard diversity factors; you know, for example, the tenant is never going to have more than 3 welders on the premises so you can base your calculations on intended use and intended duty cycles and get the AHJ to sign off on it.


But it's unlikely you'll have that exact scenario. More typically, you will have to use the "group of welders" calculation specified in 630.11(B). That means you add together the amperage of the two largest welders, 85% of the third largest, 70% of the fourth largest, and 60% of the remaining welders."

 

[jumper]

Posts from other thread were moved here.

Manny please do not ask a question in one thread and then start a new after people have replied. It creates confusion.

 

[jumper]

True. I dont have the 17 NEC, nor mine in front of me... is this page accurate?:

http://www.codebookcity.com/codearticles/nec/necarticle630.htm

"You can apply standard diversity factors; you know, for example, the tenant is never going to have more than 3 welders on the premises so you can base your calculations on intended use and intended duty cycles and get the AHJ to sign off on it.


But it's unlikely you'll have that exact scenario. More typically, you will have to use the "group of welders" calculation specified in 630.11(B). That means you add together the amperage of the two largest welders, 85% of the third largest, 70% of the fourth largest, and 60% of the remaining welders."

I am getting way too tired to do welders tonite. It seems to be correct, but I am not committing.

If no one else replies, I will look at it in morning.

 

[mannyb]

Manny please do not ask a question in one thread and then start a new after people have replied. It creates confusion.[/QUOTE]


I understand. I apologize. i didnt want thread to get off track by me asking one question then veering off track with another. On the same note. The 1000w MH are existing and they wish to keep. Where on ballast would i find the VA needed to calculate the general lighting. The building is 19ooo Sqft Would that be warehouse at.25 or ?? The welding machines are 100 duty with 230/26a 3 phase I am not sure the usage but I could use the table on 630 correct? 100/100/85/75 I really dont know and customer is sure either. sometimes yes sometimes no

 

[jumper]

Manny please do not ask a question in one thread and then start a new after people have replied. It creates confusion.

I understand. I apologize. i didnt want thread to get off track by me asking one question then veering off track with another. On the same note. The 1000w MH are existing and they wish to keep. Where on ballast would i find the VA needed to calculate the general lighting. The building is 19ooo Sqft Would that be warehouse at.25 or ?? The welding machines are 100 duty with 230/26a 3 phase I am not sure the usage but I could use the table on 630 correct? 100/100/85/75 I really dont know and customer is sure either. sometimes yes sometimes no[/QUOTE]

No need to apologize, it is better to start a new thread with a different question.

The problem is leaving the question in the other thread, I moved the replies here.

If your edit time expires, simply contact me or another mod and we will be glad to help.

As far as the questions above, gimme a sec or someone else will answer.