Sub Panel with Aluminum or Copper

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  #1  
Old 01-15-06, 03:44 PM
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Sub Panel with Aluminum or Copper

Hello, I have a Fuse Sub Panel to re-wire and replace. It is a 60 Amp Panel that I plan to use a 100 Amp Breaker Panel board on 60 Amp breaker from the Main. There will be no additional circuits to throw this one over the 60 amps. My question is this:

This sub panel is roughly 50 feet away. I would like to run a new feed to address the fact that there is no Grounding on the present one. Due to the fact that I need to fish this cable over a finished ceiling and up a wall to the location of the sub panel. Would it be advisable to utilize 6/3 NM Romex with Ground #8 or since aluminum is cheaper right now, would SC Service be acceptable for this application. I have done alot of Panels and Sub Panels, but this one is farther from the Main then I have ever done. I was curious if I were to use Aluminum if this would be acceptable fished over ceilings and through a wall for a distance of 50'. Just a brainstorm, but would like some others input on this.
 
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Old 01-15-06, 06:52 PM
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Not only would you like to run a new supply cable, you have to. Code requires that that the new sub panel be wired properly. That doesn't meant he circuits from the sub panel have to be updated, but the new sub panel it self must be properly wired from the main panel.

Use NM-B.
 
  #3  
Old 01-15-06, 06:57 PM
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Aluminum type SE style SER (SER for short) is made as a 4 wire cable made to feed sub panels. For your purposes size 4-4-4-6 will work.

You are required to use the 60 deg rating of NM-B so #6 NM-B (copper) is only good for 55 AMPs.

Or, SER is available in copper as well, the size needed would be 6-6-6-6. Bring a home equity loan and any retirement funds with you to buy it.

UNK
 
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Old 01-15-06, 08:25 PM
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Yeah I figured leaving the old fraid sub feed cable wouldnt be the best practice. Too bad I am into following the code so strictly, the ceiling in the basement is now finished, so in addition to the work of replacing the panel, I have my work cut out for the surgical removal of ceiling where I have to get the cable fished around! I am not keen to the idea of using Aluminum for this job. Thanks for your input.
 
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Old 01-15-06, 09:52 PM
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Originally Posted by itsunclebill
You are required to use the 60 deg rating of NM-B so #6 NM-B (copper) is only good for 55 AMPs.

But, unless I'm mistaken, you are allowed to round up to the next standard breaker size and thus use a 60 amp breaker with #6 NM-B.
 
  #6  
Old 01-16-06, 06:17 AM
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Yes, you can round up. The question is why you would when the correct size and rated cable is available and is cheaper than the undersized one.

UNK
 
  #7  
Old 01-16-06, 08:24 AM
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Yes I have read according to code the round up on the breaker size is acceptable, but I have a tendency to agree with Uncle. I would rather go with the exact match or better. I dont think its wrong to take it a step farther thats for sure. My alternative is to bump up the copper to #4/#4/#4/#6 and run through Mettalic Flex and Emt. This would be more then adequate and more then I can afford too, but safe
 
  #8  
Old 01-16-06, 09:57 AM
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You cannot _simply_ 'round up to the next breaker size'.

You must calculate the load being served, and then if the load served is less than the ampacity of the wire, and only then round up to the next standard breaker size.

This means that a 55A cable may be used to serve a 50A load with a 60A breaker, but may not be used to serve a 57A load with a 60A breaker.

-Jon
 
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