# Does this exception apply?



## Honestly (Feb 3, 2011)

230.90 Exception 1

I am installing the service on a pump house that will supply a 50hp motor at 480V (FLA 65). There will also be a 6kva transformer for a light and a few receptacles. I plan on a 200A service- would I need to size service entrance conductors according to 310.16 @ 3Ø or would the above exception apply, leading me to 125% of 65 = 81.25 + 12.5 =93.75, or #3 CU?


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## Chrisibew440 (Sep 13, 2013)

Yes correct. Size your conductors at 125 percent. If you go by 310.16 you will get #4's. when that fifty horse kicks on those #4's will be clapping. I'd send #2s that's a little heavy but safe and you won't have to explain to the customer what that clapping noise was. Side question do you have a soft start/ part winding start motor. What do you got? At any rate I'd still run #2's.


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## Chrisibew440 (Sep 13, 2013)

Remember, the code is just the minimum. And motors like a ground fault can draw thousands of amps. With a motor, on start up. With a ground fault, until it is cleared or the ocpd does its job.


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## Honestly (Feb 3, 2011)

Due to my lack of experience with large motors, I think I may just contract with him for the service only. He said he knows someone that could do everything for the motor. Since you mentioned inrush, I would imagine the trip curve on a common 200A panel main would allow for that inrush without tripping? The motor is on a water pump for golf course irrigation.

I would love to do everything for this one, but I don't want to screw something up!


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## Chrisibew440 (Sep 13, 2013)

Off the top of my head a 200 amp main should hold but section 430 on motors will tell you how to size your ocpd's. By the way I think you should do the project. My experience in motor control and plant service work was priceless knowledge. If you have questions I'd be happy to take a stab at it. If not that's cool too.


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## chicken steve (Mar 22, 2011)

Honestly said:


> Since you mentioned inrush, I would imagine the trip curve on a common 200A panel main would allow for that inrush without tripping? The motor is on a water pump for golf course irrigation.
> 
> I would love to do everything for this one, but I don't want to screw something up!


Couldn't a serv rated 480 3ph disco w/TD's be used?

~CS~


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## Honestly (Feb 3, 2011)

Chrisibew440 said:


> Off the top of my head a 200 amp main should hold but section 430 on motors will tell you how to size your ocpd's. By the way I think you should do the project. My experience in motor control and plant service work was priceless knowledge. If you have questions I'd be happy to take a stab at it. If not that's cool too.


One of the best parts of electrical work is learning new areas. Thanks for the offer, I will probably send you a pm.


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## Chrisibew440 (Sep 13, 2013)

chicken steve said:


> Couldn't a serv rated 480 3ph disco w/TD's be used?
> 
> ~CS~


Yes you could but using just fuses is an old method of protecting a motor. You want all conductors to be broke in case of an issue. Single phasing a motor can lead to buying a new one in a hurry.


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## Chrisibew440 (Sep 13, 2013)

Honestly said:


> One of the best parts of electrical work is learning new areas. Thanks for the offer, I will probably send you a pm.


Your welcome and what's a pm?


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## Honestly (Feb 3, 2011)

Chrisibew440 said:


> Your welcome and what's a pm?


Private message


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## Chrisibew440 (Sep 13, 2013)

Honestly said:


> Private message


Aaaah! got it


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