In a print shop, the service entrance equipment has three 125A breakers. These feed three 120/208 breaker panels. There is a fourth space in the SE panel for another breaker.
We have need to power one new printing press which draws just under 150A. If the total load calculations work out, is there any reason we couldn't use a suitable-sized breaker in the SE panel to supply this one load rather than install another 120/208 breaker panel?
Thanks.
It depends upon what the SE panel is rated for. Yes the Panels them selves have ratings for the bus bars. Obviously your running 375A so far. Is it a 400A panel or .... If you pop the cover you should see a tag inside as to what the rating is. Be careful you got Niagara Falls behind that panel ;)
Cheers
As long as the load calc works, why not? What are you cruising at now?
It strikes me that this is not a do it yourself project. What is the size of your service? You need to contact your power company to find ot what they are delivering to the premies. How will they react to such an unbalanced load? If you have to ask this question, you should farm out the job.
Why do you think this is an unbalanced load? I have to think a 150a printing press is 3p.
It is 3-phase.
You didn't say how much current you are being supplied. If your SE can handle the extra breaker with safety margin then you may be fine. I agree about seeking a licensed electrician.
Tom
Ask your insurance company.
Thanks Tom and others for your comments.
Yes, we will consult with an electrician or the Utility to avoid any assumptions before we do the work.
Cheers!
Insurance is OK with anything within NEC.
IIRC, there was one extra slot available for the circuit breaker. How do you protect a three-phase load that way?
From the description I am assuming there is one three phase spot in the panel, not a single phase spot. I can't think of a panel arrangement that could have 3 3 phase breakers and a single phase slot. (would anyone even make a single phase 150A device?)
Again, IIRC there were three slots used, each with a breaker for a single phase load. To me, it seemed to be a typical arrangement for lighting. I don't think any of this was explicitly spelled out.
3-pole breaker.
Ah. OK, technically there's 3 slots available. There are only 3-pole breakers in this panel so I didn't count individual bus tabs, but 3-pole breaker locations.
From the original post: =============================================== In a print shop, the service entrance equipment has three 125A breakers. These feed three 120/208 breaker panels.
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A breaker can have more than one phase going through it.
mike
This another example where the problem is one of communication. It behooves a technical person to use unambiguous language. Too many engineers, as well as other professionals, do not value good communication.
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