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Old 11-23-2016, 11:34 PM
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Default Wiring question

I'm running some 2-2-4 aluminum URD wire, plus a 4 ought ground, about 275' to my new temporary shop.

I'm starting at a 200 amp panel with a 100A breaker. I bought a 125A load center to mount in the shop, mostly because it was a complete kit, with a handful of breakers included.

But now I'm wondering...
Can I start with a 100A breaker and end with a 125A breaker?
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Old 11-23-2016, 11:45 PM
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I am no electrician but I don't see any problem, your 125 breaker will just be a disconnect and you need one anyway.
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Old 11-23-2016, 11:54 PM
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Electrically there isn't anything wrong with it.

If it's to be inspected, sometimes inspectors get weird and you have to argue with them. Depends on the inspector and his bosses as to how that goes. Sometimes they are quick to listen. Other times you play it by ear how much of a stink you raise about it (factoring in the cost of just "doing it his way," and sometimes only while he's there, then parts get returned and my parts go back in.)
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Old 11-24-2016, 09:27 AM
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No issue, but as mentioned it is only a disconnect at that point. Other thoughts are to be aware that aluminum has a higher torque requirement for connections and over time is more likely to loosen and need re tightening to avoid issues.
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Old 11-24-2016, 10:42 AM
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Okay excellent. I have a habit of over thinking stuff like that
Happy Thanksgiving fellas!
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Old 11-24-2016, 11:53 PM
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#2 AL is not suitable for 100A, in the OP's situation 90 amperes maximum. The only way 100A is OK is under 2011 NEC editions and earlier when it handles the ENTIRE load of a dwelling service, feeders to outbuildings, subpanels do not comply with the rules allowing someone to undersize the conductors, it's one of the misused code sections.Table 310.15(B)(6) was removed in the 2014 NEC and now load calculations are required to undersize the conductors for a dwelling services, that table is where most people get the mistaken idea #2 AL is OK for 100A sub feeds.

Last edited by Norcal; 11-25-2016 at 12:03 AM.
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Old 11-25-2016, 09:57 PM
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FWIW, the inspector suggested the #2 aluminum. He won't be inspecting it though.
But I do want it safe.
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Old 11-27-2016, 04:27 PM
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What about my ground at the sub panel? Does it need a ground to earth as well as a separate bar in the panel?
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Old 11-27-2016, 04:42 PM
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I don't know. I put a 100A breakered panel in the garage and used 3 conductor 2/0 aluminum with a #1 ground on about a 75 foot run. Per my sparkie's advice.
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Old 11-27-2016, 05:15 PM
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Quote:
Originally Posted by Bender View Post
What about my ground at the sub panel? Does it need a ground to earth as well as a separate bar in the panel?
I was required to put in 2 rods 8' apart with a single conductor back to the sub panel I have in my shop. I'm not sure if that was required by code but that's what the inspector wanted and that's what I gave him.

Even when an inspector is clueless and totally wrong, arguing with them usually winds up with you getting mad and a failed inspection.
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