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Old 06-03-2012, 07:57 PM   #1
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Adding two circuits, pros/cons to using same box?


I'm adding two circuits to a room, one to support a "craft table" which will draw no more than 500W max in expected configuration. The other to seasonally support either a window a/c or space heater. The location of the outlets vs. the things they are running mean that the outlets could exist in the same box, and if they didn't, the two single boxes would end up being quite close to either anyway.

My Q's
- I'm planning to run 20A for both, it's a bit overkill, but I don't really see a disadvantage to having 20A vs. 15A available? It's an unfinished basement and the room is directly over the breaker box, we're talking about 10-12' of romex tops with easy access, so pulling stiffer wire, or the additional costs, are not a concern. The craft table is wired with its own outlets--it's an old lab bench from my work--I've checked inside the panels and it is wired with #12.

- Besides the two circuits shutting down in unison when the breaker is thrown, is there any disadvantage in this situation to using a MWBC and putting two duplex outlets into a double gang box--one for one circuit and one for the other? Conversely, besides separating the ability to shut down the circuits, is there any advantage to keeping them separate? Example, will the a/c cause any additional issues with equipment plugged into the craft bench where it's a shared neutral? The craft bench will be running computer equipment, and possibly some slightly more sensitive stuff like an oscilloscope.

thanks

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Old 06-03-2012, 08:52 PM   #2
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Adding two circuits, pros/cons to using same box?


The only issue would be if your area requires AFCI protection for the new circuits. If you need AFCI protection you will need two cables so the neutral is not shared. Being inone two gang box is not an issue. The grounds would need to be connected.

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Old 06-03-2012, 09:15 PM   #3
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Adding two circuits, pros/cons to using same box?


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Originally Posted by Jim Port View Post
The only issue would be if your area requires AFCI protection for the new circuits. If you need AFCI protection you will need two cables so the neutral is not shared. Being inone two gang box is not an issue. The grounds would need to be connected.
Good point, I didn't think about AFCI.

It was apparently not required when my electrical was updated in late 2010, but then again it seems like my electrician followed older rules because he did not put handle ties on the MWBC's he created--he would cut two old circuits and tie into a junction box, then run 14/3 to that junction box. Those circuits don't have handle ties. There is also no handle tie on the new MWBC's which go under the sink to handle dishwasher & disposer.

A friend who had the same work done (updated panel, few new circuits added) at the same time, but in another town, did need AFCI breakers.

I think my town follows NEC 2008.
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Old 06-04-2012, 07:09 AM   #4
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Adding two circuits, pros/cons to using same box?


Without a local amendment to delete the AFCI's, the national code would require AFCI unless it was for certain areas like a kitchen or bathroom receptacle. It does not sound like this applies to your situation.
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Old 06-04-2012, 07:30 AM   #5
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Adding two circuits, pros/cons to using same box?


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Without a local amendment to delete the AFCI's, the national code would require AFCI unless it was for certain areas like a kitchen or bathroom receptacle. It does not sound like this applies to your situation.
Hi Jim,

Yes, I believe you're correct, so in my case I'd want to keep them separate so that they can be protected by AFCI breakers--that's pretty much what I was looking for, some reason to choose one vs. the other.
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