Attached Garage Sub Panel

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  #1  
Old 06-09-05, 03:31 PM
noteasilydistra
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Attached Garage Sub Panel

Hi Folks, I want to install a 70 amp sub panel in my attached garage. The Breaker panel is 125 ft away located on the outside of the house at the far end. I have purchased a sub panel and breakers but the question I have is: Since I'm running the cable through the attic I chose 6/3 nmb, can I run the 6/3 nmb with ground into conduit the 12ft distance I have to go to reach from the main to the attic area on the outside of the house (12ft conduit) and from where I drop the line through the ceiling to the sub panel in the garage? (about 3.5 ft) Your thoughts please? Phoenix,AZ
 
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  #2  
Old 06-10-05, 07:53 AM
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Yes, short conduit runs of conduit are okay for protection so long as the ends are unsealed.

However, 6 gauge wire is not large enough for 70 amps; you need 4 gauge for 70 amps. The #6 should be breakered at 50 amps for 60 degree terminations or 60 amps for 75 degree terminations.
 
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Old 06-10-05, 10:54 AM
noteasilydistra
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Conduit open ends.

I was told that 6/3 nmb copper is fine up to 75 amps but alum. would be less. Was I wrongly informed? When you say unsealed, do you mean the conduit ends are not water tight as in air can flow from the main through the conduit into the attic? One more thing, when the cable enters the conduit do I remove the sheathing on the wire or do I leave it on until it enters an inch into the panel? Thanks for your help.
 
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Old 06-10-05, 11:49 AM
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You were wrongly informed. Also at this distance you want larger wire anyway, to account for voltage drop.

Do not remove the sheathing on the wire.
 
  #5  
Old 06-10-05, 12:24 PM
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The 75A rating for #6 only applies for 90 degree C terminations, are only allowed in some commercial and industrial applications -- never in residential.

The wire menu at Lowes, for example, lists only the 90 degree ratings next to the prices which is extremely misleading to customers in my opinion.
 
  #6  
Old 06-10-05, 12:42 PM
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Furthermore, NM-B cable is never, ever rated above its 60-degree rating (which for #6 is 55 amps, which can be breakered at 60 amps).

And Phoenix attics are ovens in disguise, so you may need to compensate for temperature too. Check with your building department to see if temperature compensation is required.
 
  #7  
Old 06-10-05, 01:05 PM
noteasilydistra
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Thanks for the advice. I'll check into the local codes furthur before proceeding. I want to do it right the first time.
 
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