3 phase distribution to single phase sub

[bobbymari]

we have a 120/240v 3 phase set up meter/main/distribution panel for apartment elevator which will also feed a sub for house lighting/laundry room.
Question , is it permissible to feed the single phase sub using 2 poles of a 3 pole breaker?
No single 120v loads just a 240v sub feed using 2 poles of the 3 pole breaker.

Reason being is our 3 phase plans have us using the exception to 408.3 using c phase as the wild leg at the distribution point
Didnt want to cause confusion by installing a 3 phase panel in laundry room and switch the wild leg to b phase since it would not fall under the exception as being in the same switch board or panel board
prefer to leave laundry/lighting sub as is , single phase sub

 

[JFletcher]

You could, tho I dont see why you wouldn't use a 2 pole breaker across AB legs; it can be slash rated. Also, the switch of the high leg from C phase in the main panel to B phase in the sub panel isn't that confusing imho.

 

[bobbymari]

You could, tho I dont see why you wouldn't use a 2 pole breaker across AB legs; it can be slash rated. Also, the switch of the high leg from C phase in the main panel to B phase in the sub panel isn't that confusing imho.

Reason for the 3 pole is I have one and the breakers are pricey as aic rating is 65k
also save me some wire as its a long run

Confusion meaning when we leave and property management starts using their "service techs"

 

[JFletcher]

Reason for the 3 pole is I have one and the breakers are pricey as aic rating is 65k
also save me some wire as its a long run

Confusion meaning when we leave and property management starts using their "service techs"

Gotcha on the breaker, not sure how it will save wire (unless it's by deletion of pulling the high leg)?

and if there is a high leg anywhere, eventually one of their maintenance guys is gonna shift around or add a breaker and send 208V to a 120V load. There's only so much idiotproofing you can do.

Are you using a 1 or 3 phase subpanel?

 

[bobbymari]

Gotcha on the breaker, not sure how it will save wire (unless it's by deletion of pulling the high leg)?

and if there is a high leg anywhere, eventually one of their maintenance guys is gonna shift around or add a breaker and send 208V to a 120V load. There's only so much idiotproofing you can do.

Are you using a 1 or 3 phase subpanel?

yes save wire by deleting the high leg to a single phase sub
there is currently one there, I was just wanting to make sure I can go from 3 phase distribution on a 3 pole breaker to single phase sub using "normal legs" a,b in this case or if I had to swap it with a 3 phase sub.
This part of the project isnt on the plans

 

[ActionDave]

yes save wire by deleting the high leg to a single phase sub
there is currently one there, I was just wanting to make sure I can go from 3 phase distribution on a 3 pole breaker to single phase sub using "normal legs" a,b in this case

Yes, you can do this.

 

[electrofelon]

we have a 120/240v 3 phase set up meter/main/distribution panel for apartment elevator which will also feed a sub for house lighting/laundry room.
Question , is it permissible to feed the single phase sub using 2 poles of a 3 pole breaker?

Sometimes it is even required: some manufacturers don't make straight rated 2 pole breakers in certain lines, so you must use a 3 pole.