Feeder Wire Size

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  #1  
Old 11-12-06, 08:21 PM
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Feeder Wire Size

I'm installing a 300amp sub panel from a 600 amp service panel.

The distance between the panels is less than 50ft., so the wire size calculation appears to be #2.

This seems too small maybe? I'd like a second opinion from others.

Also, I'd like any opinions on the grounding conductor size between the panels.

Thanks!
 
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  #2  
Old 11-12-06, 08:35 PM
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Rd these figures do not add up for a single family dwelling how are you getting these panel amperages?
 
  #3  
Old 11-12-06, 09:07 PM
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Hi Roger,

You are correct, it's not residential. The space being remodeled and electrified is in the basement of a commercial retail building. The building has service from the street and a main panel at 600 amps.

Does this help?

Thanks!
 
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Old 11-12-06, 09:32 PM
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Rd we need to ask a lot of questions on this one but its late and I'm needing a bit of sleep. So I'll start the questions by asking if we are dealing with a 3 phase panel or single phase panel. A very common 3 phase panel would be a 208Y120 but its hard to say so can you clarify?

Also working on a commercial building as a Diy is probably not acceptable in most juristictions. Have you checked to make sure you can do this work?

Hopefully someone will pick this up in the morning if not it will be late afternoon before I can get back to this.

Roger
 
  #5  
Old 11-12-06, 09:49 PM
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I can answer both questions.

The service is single phase. The building is strictly retail/office, and there are no industrial type applications (heavy machinery, etc.), so permits and electrical work are allowed under the auspices of the building owner, who I will be working with.

It's actually a straight forward project. Several offices, two bathrooms, a small kitchenette, and a few meeting rooms. The owner wants a 300amp panel to accommodate additional build-out in the future.

The current project will account for only about 150amps tops.

thanks!
 
  #6  
Old 11-13-06, 03:53 AM
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I would totally be against giving any further advice.
ANYONE doing this kind of electrical work SHOULD NOT have to ask these questions. If you have to ask such basic questions you have NO place doing this work. Period.
Commercial work, especially of this scope, is NO PLACE for a DIY. And any electrician doing such work should get some field guidance, not simply going to a DIY site and asking questions.
600A switch gear is no place for the untrained to be messing around.

Since the OP has absolutely no information in his profile we can only assume he is a DIYer.

rdn2113, are you a licensed electrician with the proper insurance to do commercial work?
There is more at risk here than running #2 to feed a 300A panel.


Sorry for the blunt opinion, I just feel very strongly about this.
 
  #7  
Old 11-13-06, 08:36 AM
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Originally Posted by rdn2113
I'm installing a 300amp sub panel from a 600 amp service panel.

The distance between the panels is less than 50ft., so the wire size calculation appears to be #2.

This seems too small maybe? I'd like a second opinion from others.
Also, I'd like any opinions on the grounding conductor size between the panels.Thanks!
I'll answer one question. If you are planning to install a 300 amp
breaker to feed the 300 amp panel, you are about 8 wire sizes
too small.
 
  #8  
Old 11-13-06, 11:48 AM
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No need to apologize Speedy, I appreciate bluntness and the intent behind it. I stand corrected.

Having done a number of 200 amp installs, I felt comfortable with doing the 300, but as I had not done one before, I wanted to double-check the feeder size issue.

As you pointed out, however, under these circumstances, it will be better to allow a pro with commercial credentials and experience do the panel installation.

I'll be meeting with the building owner today and that is exactly what I will insist be done.

Thanks everyone!
 
  #9  
Old 11-13-06, 07:35 PM
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Hello Rd

Well... I am not going to have to tell you that in order to open and get inside that 600 amp panel requires arc flash protective equipment...which aint cheap. Speedy is someone I highly respect so heed his advice.... 600 amps aint childs play. Anyway excellent decision to get a pro in there to do that install.

Roger
 
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Old 11-14-06, 12:13 AM
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Thanks Roger. I respect his opinion too, as well as yours and many others in this forum.

We have a pro coming in this Sunday when the building is closed. He is going to upgrade the main building panel to bring it up to code. He will also install a 200amp and a 100amp breaker for us to tap when we are ready to install subpanels in the new space. This arrangement will actually work out better for us and the way we need to distribute power.

And yes, we are pulling permits for all the work. I've already spoken with the inspectors for our area.

Thanks again Roger.

Best wishes!
 
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