# Need help sizing circuit and breaker for aotomotive paint booth



## Dennis Alwon (May 9, 2009)

That would work fine for the feeder however you don't use 175% because 430.52 is for individual motors. 

I would stop at 71.7 amps and use an 80 amp breaker unless exception 1 in article 430.24 applies.


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## telsa (May 22, 2015)

[email protected] said:


> Hi all,
> 
> I am currently trying to size my circuit conductors and breaker for a paint booth.
> The electrical in the booth consists of:
> ...


Your entire wiring philosophy is odd.

The norm around here would be:

One circuit just for the lighting and its own 20A breaker -- the smallest we set in a panel.

One (3-phase?) breaker just for the 10hp motor -- to hit a disconnecting safety switch very close to the point of utilization.

One (3-phase?) just for the 7.5hp motor -- to hit a disconnecting safety switch very close to the point of utilization.

These might all travel in the same pipe most of the way, perhaps terminating in a 4x4 guttter above the two safety switches -- or some such -- where the loads would be broken out.

Your OP reads like you're setting a sub-panel -- very weird for just a painting booth.

Your thinking would leave anyone to believe you've never spent a day around a practicing electrician.


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## telsa (May 22, 2015)

If ALL of your experience is strictly Residential -- then stay away from Commercial work until you've been cross-trained by a journeyman.

You're not going to pick up the required skills via the Internet.


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## [email protected] (Jan 25, 2013)

telsa said:


> If ALL of your experience is strictly Residential -- then stay away from Commercial work until you've been cross-trained by a journeyman.
> 
> You're not going to pick up the required skills via the Internet.


I have worked on many different projects over the years. I am currently helping a family friend with his auto body shop. 
The one thing I am not familiar with is motors, getting more so now. 
I'm only using this site as a resource to make sure my calculations are on par so I don't have any issues with inspections. I thought that's what this type of platform is intended for....
If you don't agree with how I am using this site, sorry, just keep scrolling.

Thanks


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## [email protected] (Jan 25, 2013)

telsa said:


> Your entire wiring philosophy is odd.
> 
> The norm around here would be:
> 
> ...


No, I am not planning on setting a sub panel...
The booth is a engineered modular unit. It comes factory wired and assembled. It has a control panel on it with all of the overloads transformers and relays already wired and in place. Also, all the light fixtures and motors are wired and in place. 
It requires one 3phase circuit to power the unit....
I wanted to make sure I was going about my calculations for the motors, while including the lighting load as well.

Thanks for the help


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## ponyboy (Nov 18, 2012)

If all you need to do is provide primary to a main controller then look for the fla or kW rating on the unit. This is all the info you should need if everything is factory wired.


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## telsa (May 22, 2015)

[email protected] said:


> No, I am not planning on setting a sub panel...
> The booth is a engineered modular unit. It comes factory wired and assembled. It has a control panel on it with all of the overloads transformers and relays already wired and in place. Also, all the light fixtures and motors are wired and in place.
> It requires one 3phase circuit to power the unit....
> I wanted to make sure I was going about my calculations for the motors, while including the lighting load as well.
> ...


It's best if such details pop up in your Original Post.

I've seen, we've all seen, every variation known to man. 

I could not count the number of assemblies that demanded that I field wire just about everything.

And I've seen plenty of factory-wired get-ups, too.

Hence, my perplexity.

Cheers. :thumbsup:


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