Sub Panel Install

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  #1  
Old 12-15-06, 10:43 PM
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Sub Panel Install

Hello All....

Couple quick questions, I have a service panel that is currently full it is 100 amp. I have another service panel that is 70 amp.

I want to use the 70 amp as a sub panel (even though it has a main breaker and used to be a main panel). Is there a problem with using this as a sub? What size breaker do I need to put in the main panel to run the sub? What type of wire do I need to feed the sub?

Thanks in advance.....
Craig.
 
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Old 12-16-06, 05:19 AM
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Will the sub be mounted next to the main? Does the new sub have a separate ground bar? If not you will need to install one. Is the neutral bonded to the case? If so it will need to be isolated. I'd suggest a 100 amp breaker in the main but a 70 would do and save you a bit on wire cost. Wire size to some extent depends on distance from main also. What loads will be on the sub?
 
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Old 12-16-06, 05:36 AM
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70 amp is a rather strange size sub panel, but whatever, If it is truly a 70 amp sub panel then you need no larger than a 70 amp breaker in the main panel. You need a four wire feed to the sub panel and the ground and neutral MUST be separated at the sub panel.
 
  #4  
Old 12-16-06, 09:48 AM
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Originally Posted by racraft View Post
70 amp is a rather strange size sub panel, but whatever, If it is truly a 70 amp sub panel then you need no larger than a 70 amp breaker in the main panel. You need a four wire feed to the sub panel and the ground and neutral MUST be separated at the sub panel.
The breaker on the "to be" sub panel is 70 amp, that is where I got that number from.

The sub will be mounted right next to the main.

The neutral is connected to the frame of the box. How do I go about separating the neutral from the box?

thanks!
 
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Old 12-16-06, 11:20 PM
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without seeing the specific panel, it's hard to advise how to isolate the neutral and ground.

In newer panels, there is sometimes a "bonding" screw that goes through the neutral bus bar and into the panel box. Or, there is a removable segment of metal that connects the neutral bus bar to the grounding bus bar. In either case, the bonding between the neutral and ground must be broken so they are isolated from each other.
 
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Old 12-17-06, 06:21 AM
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If the existing neutral bar is mounted to the metal of the enclosure you will need to buy a neutral bar with insulated standoffs. This won't be available at a big box store. You may find it will be cheaper to buy a new panel than to set up the one you have correctly as "list price", which you are likely to have to pay at a supply house, is a lot higher than the pricing you may be used to seeing.
 
  #7  
Old 12-17-06, 09:10 AM
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Are you saying your exsisting service is exceeding it's limits or are you saying the panel is just out of physical room?
 
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Old 12-18-06, 08:53 PM
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I was just out of physical space in the box.

Thanks for all of the advice, you guys were dead on about the box. There was a thin piece of metal grounding the neutral bar to the box. Just had to remove that metal ribbon and it worked like a charm!

thanks again!
 
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