Mains 3-phase wiring question

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.
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wrote:

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
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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!
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On 12/4/2011 1:09 AM, Mike Cook wrote:

Ask your insurance company.
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Insurance is OK with anything within NEC.
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wrote:

As long as the load calc works, why not? What are you cruising at now?
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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
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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.
--

Sam

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On Sun, 04 Dec 2011 09:04:53 -0800, Salmon Egg

Why do you think this is an unbalanced load? I have to think a 150a printing press is 3p.
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It is 3-phase.
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snipped-for-privacy@aol.com wrote:

IIRC, there was one extra slot available for the circuit breaker. How do you protect a three-phase load that way?
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Sam

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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.
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3-pole breaker.
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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?)
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snipped-for-privacy@world.std.spaamtrap.com (Michael Moroney) wrote:

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.
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Sam

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Salmon Egg wrote:

From the original post: ==============================================In a print shop, the service entrance equipment has three 125A breakers. These feed three 120/208 breaker panels.
============================================== A breaker can have more than one phase going through it.
mike
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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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Sam

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