3P Breaker feeding single phase breaker

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Npstewart

Senior Member
Have a existing 225A/3p breaker feeding a existing 225A panel in a tenant space (no feeder is existing). We want to remove the panel and use the 225A/3p service from the meter center to feed a single phase 200A enclosed circuit breaker which will feed a piece of medical equipment.

Is it legal to not use the 3rd leg and only pull two legs from the breaker to the enclosed circuit breaker?

Alternatively my idea was to remove the breaker in the meter center and stab on a new 200A/2p breaker onto the side of the meter center and feed the 40KW single phase load that way.

Any help would be great!
 

Npstewart

Senior Member
I like the second idea better too but the EC says its more expensive. Im looking for a code violation to prove we shouldnt do it.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
I am sure there is someone somewhere that will find fault with it but there is no reason that a 3P breaker will not work well with only 2 phases connected. I would not buy another breaker.
 

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
Do you still have the 3rd cable running out to where you want to install the 2P device? If not, no problem. If so, abandoning a live conductor poses some issues, but you could just disconnect it at the feed end too.

Newer European design 3P circuit breakers would pose an issue because they would trip on phase imbalance, so you would have to loop one conductor through 2 of the 3 poles. But older NEMA design breakers don''t have that issue, there is no problem with one of the poles not seeing any current.
 

nollij

Member
Location
Washington
I have used 2p of a 3p breaker when the 3p was already available and there was not enough time to wait for ordering a 2p. I did not find fault within the NEC for the installation at the time and the inspector did not disagree with the installation.
 

Npstewart

Senior Member
My square D rep said that she cant put a 2p breaker in the 3p meter center. Which means my only solution would be to not connect the 3rd phase, or stab on the single phase meter on the side.

I think im just going to go with not running the 3rd leg. To me it seems rigged, but I cant come up with any code issue, I dont like it but I cant condemn it I suppose.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Is the source 208Y/120 or 240D/120 with a high leg?

If it's the latter, it's perfect for what you want to do.
 
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