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Thread: Shop wiring

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    Shop wiring

    Yep, another question about electrical on a wood forum!

    I passed the inspection on my shed wiring today, but the inspector and I had a discussion about one item:

    I have two separate circuits running to two different outlets that are housed in the same box. Reason is for plugging in both a high amp power tool and my vacuum at the same location. Although hard to tell in the photos, one circuit is white, and the other is ivory color coded.

    Both circuits are GFCI protected:

    At present I have the breakers tied together. Code does not require it (two different "devices") nor does it prohibit it.

    The inspector said he would not tie the breakers together, because if one circuit causes a trip, I wouldn't be able to tell which one. I was thinking that in the instance of working in the box, I would want to make sure both circuits were de-energized. He agreed that was a view of it, but said I could go either way, but he would go single breakers.

    Upon thinking about it, another factor would be if I had my table-saw, router, etc running, and the vac tripped the breaker. After fixing the problem, there is the danger that I would forget to switch off the power tool before re-setting the breaker, causing it to come to life unattended. In reality, this is more probable than me having to go into the outlet box. With the GFCI, if someone did go into the box without tripping both breakers, that would provide some protection. I think it goes without saying that anyone messing around with the wiring should know enough to check the circuits, etc, but we all know the reality is that isn't a guarantee. As long as I am the owner, I don't see a problem, but my future crystal ball is on the blink. Right now, I am leaning toward the separated breakers.

    I remember someone else on here recently doing the same two-circuits-in-one-box (thanks for the idea!! but don't recall the name) and was wondering which way they decided, and if anyone has a view they would care to share.

    Thanks for any insight you can provide

    Go

    PS: In the top pic, it appears that there is a red and black wire going to the right outlet. That "black" wire is actually gray, and I also have it wrapped with a white tape tag to further denote it as neutral. I used different (NEC approved) color coding to keep me straight on the different circuits. Also, will be uploading more pics of the process in my gallery soon.
    Last edited by Gofor; 06-12-2018 at 12:49 PM.
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    Re: Shop wiring

    Mark, I wouldn't tie the breakers together. I doubt anybody but you will be working in those boxes anytime soon. If somebody with experience were to go into them, they would see quickly that they are two different circuits and that means they cannot count on both being off just because one is tripped. If they cannot see that they shouldn't be replacing outlets. It is also not a terrible thing to me to work in a box with the circuit still hot. I do it fairly often just because I don't have all my breakers labeled. It is easily possible to change outlets in a hot box without getting shocked.

    I do not put my tools, including my table saw which is rated to draw 15A, on a different circuit than my shop vac, however. I use the tool to trigger the shop vac through a switch sold for that purpose which avoids triggering both at the same time. I have both the vac and the tool on one 20A circuit and have never tripped the breaker. The tools actually go into a power strip with a 15A breaker. My table saw will occasionally trip that. But it is pretty quick and easy to reset. The auto on for the shop vac is very handy and it also avoids the need for two circuits.

    When I wired the shop I wasn't sure if this would work. So I have a 15A circuit in addition to my 20A tool circuit. The 15A is in separate boxes a couple inches higher on the wall than the 20A. I use outlets rated 15A too which look different than 20A (no horizontal bar). The thought was that I could use that circuit for the vacuum. But I did not need to.

    Another idea that makes sense to me and would reduce the tangle of wires going to my shop vac is to use one circuit to trigger the vacuum. Anything plugged into that circuit that you turn on triggers the vac. You still have to move hoses around (unless you also have piping and blast gates).

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    Re: Shop wiring

    The inspector makes a good point though as you have realized, it's just one of those stylistic issues rather than being a code one.

    I ran 20A 120 and 240 recepatcles around the shop. All you need is a little bit thicker wire (12g) which you want even at lesser amperages if it's a long way to the panel. I used to have a #### of a time with my little delta contractor saw in the garage on a 15A circuit because the voltage drop was pretty severe.

    Gray is a perfectly acceptable color for grounded conductor (netural), without remarking and is prohibited for any other purpose.
    No job is worth doing unless you can get a new tool out of it.

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    Re: Shop wiring

    Quote Originally Posted by Gofor View Post

    I remember someone else on here recently doing the same two-circuits-in-one-box (thanks for the idea!! but don't recall the name) and was wondering which way they decided, and if anyone has a view they would care to share.
    Mark, that might have been me.

    I have previously posted that all of the double receptacle boxes in my wood shop are wired into two separate breakers. I did this to not only have two 20A circuits available at each box, but also because it gave me the flexibility of converting any location to a 20A 240V circuit or a 3 phase outlet w/o having to pull additional wires.

    I did not opt to tie the breakers together. Among other reasons I always check all circuits in a box with a multimeter before doing work on them, so if one side is still hot I'll know to follow up on it before sticking my hands in there.

    Scott

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    Re: Shop wiring

    Thanks all so far. All the 120 circuits (six) are wired with #12, and the 240v I have planned for the A/C is #10, although I now have a 20A receptacle and breaker on it.

    Thanks, Scott, for the realization that it will be relatively easy if I want to convert any of the six boxes I have wired this way to 20A 240v (in which case I would have to tie the breaker). If I later find I need a 30A circuit, I have the one with #10 wire, and can convert one of the others for an AC unit. Hadn't thought of that option.

    I also check with a multimeter before working an installed box/device (although I now also have one of those magic wand type sensors that detect energized circuits. It came with the polarity checker I bought to verify I have all the outlets properly wired. With 26 outlet devices, doing my best to make sure "old-timer's disease" didn't strike when I was connecting everything up in the 100 degree temps in the shop the past few weeks.) Electricity earned my respect back around age 10 when I was messing around with an old radio chassis (plugged in) and managed to contact the transformer. Probably have never danced as well before or since. LOL

    Go
    Last edited by Gofor; 06-12-2018 at 07:56 PM.
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    Re: Shop wiring

    The only place I can think of the Code requiring two separate circuits (whether in the same box or not)to be tied together is when they have a shared neutral. In this instance, the tripped circuit, if not tied together, would create a hazard in that the neutral would still be operational for the other circuit if it is energized. You have individual neutrals back to the panel, I assume, so it wouldn't be required, and it would mean that you would have to test both circuits to see which one tripped in either case were they tied together.
    WHAT BOX?

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    Re: Shop wiring

    Quote Originally Posted by Gotcha6 View Post
    The only place I can think of the Code requiring two separate circuits (whether in the same box or not)to be tied together is when they have a shared neutral. In this instance, the tripped circuit, if not tied together, would create a hazard in that the neutral would still be operational for the other circuit if it is energized. You have individual neutrals back to the panel, I assume, so it wouldn't be required, and it would mean that you would have to test both circuits to see which one tripped in either case were they tied together.
    Yes, the neutrals are individual and run all the way back to the panel. One reason I did this was to avoid problems with GFCI. (which was your recommendation earlier on a different thread IIRC. Thanks) In the event I did convert one box to 220, I would have to rethink the GFCI or run a separate neutral to that box. Will deal with that only if and when necessary. Currently, I have all six 120v circuits GFCI protected, but only the one that includes an outside receptacle requires it.

    Go
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    Re: Shop wiring

    If by shed you fit into the description of "accessory building with floor at or below grade level" then yes all the 120V 15/20A receptacles need GFCI protection. If it's not going to get wet, then you don't need the waterproof cover.
    No job is worth doing unless you can get a new tool out of it.

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    Re: Shop wiring

    Quote Originally Posted by FlyingRon View Post
    If by shed you fit into the description of "accessory building with floor at or below grade level" then yes all the 120V 15/20A receptacles need GFCI protection. If it's not going to get wet, then you don't need the waterproof cover.
    It is above grade:
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