Shop electric

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Old 09-09-20, 08:38 AM
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Shop electric

Hello, I recently ran electricity from my house to my shop. The shop had its own service and I wanted to cancel it due to the high cost. I ran 100amp wire from the house main panel to the shop panel. The shop panel has a bonding screw in it. Should I remove the screw since it is now supplied by the main panel at the house? Also, my main panel has a lot of extra wire stuffed in it. Is it agood idea to cut the extra wire out then just re-attach them? Last question, on a square d qo main panel box, is it pretty easy to add a bus bar? All the bus bars are pretty full and some of the lugs have 3 wires in them. Thank you all for any help.
 

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09-10-20, 05:42 AM
pattenp
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Well guess what, that's the wrong size wire by NEC. #2 Al is only good to 90A as a branch subfeed. Plus being URD it is to be terminated outside the structure, so hope you didn't run it inside any distance to the panels. Also there needs to be 4 conductors, not 3. There needs to be an equipment ground run between panels.
 
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Old 09-09-20, 09:01 AM
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Since the shop panel is now a sub-panel, yes, you should remove the bonding screw. I assume your 100a cable includes a ground wire? That's needed for sub-panel.

You could trim the extra wire in the panel, but unless it's excessive, why bother. If you're sure you won't have to move or upgrade the panel in the future, then go ahead (you could extend wires in future if needed).

You mean a neutral bar? Someone with more knowledge can answer that. For a QO panel, it's easy to add a ground bar, and then you can land all the ground wires on that bar, freeing up spots on the neutral bars. Per code, you should only have one neutral under each screw.

 
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Old 09-09-20, 09:20 AM
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Thank you Cartman. Yes, it included a ground wire. You probably know this, but on my main panel it is all bonded. So when I add a ground bar, only put the ground wire in it, or are nautrals ok to put in it as well? Then I take that I will run a wire from the new ground bar to one of the exisiting? My electricity knowledge is limited.
 
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Old 09-09-20, 09:29 AM
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Right, your main panel should be bonded. Yes, only land grounds on that ground bar(s). That should free up enough space on your neutral bars for 1 neutral per screw. Unless the panel has multiple tandems or double-tapped breakers.

You don't need to run a ground wire from new ground bar(s) to neutral bar. The ground bar's mounting screw bonds it to the panel, which is bonded to your neutral, so they're all connected. Won't hurt anything if you want to run a ground wire connecting ground bar to neutral bar.
 
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Old 09-09-20, 09:49 AM
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Just curious, what size and type wire did you use for 100A? I see way too many times DIY'ers use the wrong wire for a subfeed to an out building.
 
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Old 09-09-20, 08:17 PM
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Ok thanks Cartman! I appreciate it.
 
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Old 09-09-20, 08:22 PM
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Hello Pattenp, we used #2AWG 2-2-2 urd. I had an electrician heading up the job. Thanks for checking.
 
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Old 09-10-20, 05:42 AM
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Well guess what, that's the wrong size wire by NEC. #2 Al is only good to 90A as a branch subfeed. Plus being URD it is to be terminated outside the structure, so hope you didn't run it inside any distance to the panels. Also there needs to be 4 conductors, not 3. There needs to be an equipment ground run between panels.
 
cartman, CasualJoe voted this post useful.
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Old 09-10-20, 08:13 AM
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Also there needs to be 4 conductors, not 3. There needs to be an equipment ground run between panels.
That's odd. I specifically asked if OP's cable included a ground wire since it's feeding a subpanel. The response:
Yes, it included a ground wire.
Perhaps he's got the cable designation wrong, and it actually does have a ground wire?

Either way, as you note, it's slightly undersized for what is presumably a 100A breaker on that subpanel. I guess that could be remedied by replacing with a smaller breaker? Interesting that his electrician didn't realize the cable rating varies depending on whether it's feeding a main panel or a subpanel.
 
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Old 09-10-20, 08:32 AM
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Sometimes folks think a ground from a ground rod at the detached structure is all that's need. Maybe he added an EGC to that 2-2-2.
 
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Old 09-10-20, 12:15 PM
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And some folks use the term "Ground" interchangeably with the term "Neutral". The OP should have used 4-wire Mobile Home Feeder (MHF).
 
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Old 09-10-20, 12:35 PM
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Wow friends, thank you very much for bringing this to my attention. An easy enough fix at this point in the project. Thanks again! I will also double check to make sure I gave accurate information.
 
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Old 09-12-20, 03:34 PM
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And some folks use the term "Ground" interchangeably with the term "Neutral".
Or common.
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