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Hello,


The previous owners of my house had power ran into the backyard. I believe it was for an above ground pool pump and some lights, which are now gone. They ran 6 12-awg wires (1 blue, 1 red, 2 green, 2 white) underground through conduit.


I want to use this existing run to power the shed I built. I already routed the conduit into the shed and already have an overhead light (may switch this to a light/fan combo to cool it off when I'm in there), bench light, and a few outlets set up (lights on one circuit, outlets on another).


I am wondering how do I now use the existing run to safely power those two circuits. Should I install a small subpanel with 2 20 amp breakers? If so, how would I do that using the existing wire configuration? Would I twist the existing pairs (blue/red, white/white, green/green) to pull more amps to feed the subpanel? Or should I just power each circuit with their own set of line(blue/red), neutral (white), and ground (green) using the main panel they are tied into (20 amp breakers) on each already? I'm hoping to not have to replace the feed wires in but I do want it to be safe of course.



I would probably rate my experience level around or slightly below an intermediate, as I worked four or five summers for an electrician during high school and college; but it has been years that I have done any big projects other than normal wiring around the house. Any help would be appreciated. Thanks.
 

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A "Handy Husband"
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You are not allowed to run more than 1 circuit to an outbuilding. That can be a feed to a sub panel, a single circuit or a MWBC (multi wire branch circuit). With only #12 conductors a sub panel is not doing much for you. I would configure as a MWBC which effectively gives you two 20 amp circuits.

You are not allowed to parallel the #12s for a higher amperacity.

Or you could pull in larger conductors for a sub panel if the conduit is large enough. A lot depends how you will use the shed and how much power you need.

Sent from my RCT6A03W13E using Tapatalk
 
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This is comparable to normal wiring about and within a house.

You do not need a subpanel for the maximum 20 amps on each of the red and blue. Junction boxes may be used instead as needed.

The purpose of a subpanel is to provide circuits (or additional circuits) of suitable amperage for the intended equipment (loads). Ordinary lights and receptacles must have breaker protection of 20 amps or less.

You do need a master (double pole 20 amp) switch for the shed.
 

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Your subpanel needs a main breake--- no, that's not quite right. Your subpanel needs a disconnect switch. Given the stock of equipment readily available, the cheapest way to get a disconnect switch is to choose a panel with a main breaker, and just ignore the number on the main breaker and pretend it's just a switch.

A subpanel also needs grounding rods. One rod will do if it passes a test that requires a $5000 tester, otherwise you need 2 rods >6' apart (most people just go for that).

Wow, that makes a subpanel seem like pain, huh?

However rjniles is right that Code doesn't allow 2 separate 120V circuits out there... but there's a cheat... if one of them is on a switch (from the house), then it's legit.

Otherwise you could follow the multi-wire branch circuit approach: a MWBC gives you 2 usable 20A "sub-circuits" (one for saw, one for dust collector+lights, solves that piccadillo!) And a MWBC counts as 1 circuit, so that rule is dodged. To do that, take one white wire out of service (cap it off at both ends, don't destroy it) and use the other neutral with the 2 hots. You must tie the 2 breakers with a factory-approved handle-tie, or simply use a 2-pole breaker (which by nature has factory-tied handles. DO NOT use a twin/tandem/duplex/double-stuff 1-space breaker with 2 independent handles!)

Color wise, green and bare must be ground. White and gray must be neutral (and can't be re-marked to be a hot since you are in conduit). All other colors are hot.

Since you are in conduit, you are free to use any colors you want (within the above rules), even purple or pink. They even make color-striped-other-color, like white with blue stripe (blue's neutral obviously). You can't re-mark a neutral to a hot, but you can remark simply for identification purpose: I put blue tape on a white to say "this goes with the blue hot". Easy peasy.

You don't need 2 grounds in a pipe. Circuits can share grounds. THEY CANNOT SHARE NEUTRAL except in the abovementioned MWBC.

If you want a subpanel, the most important thing about subpanels is spaces. Nobody cares what the bus rating or main breaker is (as long as it's enough). Spaces are dirt cheap when you're buying, and priceless beyond jewels when you're trying to add something. So go absolutely bat-crazy and get yourself a 12, 16, 24, even 30 space panel. Seriously. This means the panel busing and the disconnect switch will be higher ampacity than your feed (currently 20A) and that's totally fine.

At some point in the future, I bet you'll pull three #6 and a #10 wire into that pipe, and you'll be glad your panel is 200A-bussed and 125A-disconnect instead of 60/60, because with that #6 you can feed it with a 70A breaker.
 

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A subpanel for a 20 amp mwbc is a waste.

On a side note the lugs on a main breaker panel will most likely not be rated for something as small as a #12.
 

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Not when OP has conduit. The subpanel allows you to wire out the circuits, and if tripping actually does become a problem (it might not), then at that point pull out the #12 and pull in #8 or whatever and a 50A breaker.
 

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Hello,I want to use this existing run to power the shed I built. I already routed the conduit into the shed and already have an overhead light (may switch this to a light/fan combo to cool it off when I'm in there), bench light, and a few outlets set up (lights on one circuit, outlets on another).
A couple of ideas.
Since you have conduit, how long is the run?
I ask that because you can certainly just put in two breakers and be done with it if you thing that will satisfy any future need.
And since you have conduit, you can easily pull larger wire and increase the capacity with a higher amperage breaker and wires.
What I would do is just get a small 6 breaker sub panel and put in your two breakers now. The fact that you can always upgrade the wire size if needed is a plus because of the conduit.
But for the existing circuits you only need 4 wires. Two hots, a neutral and a ground. As long as you stay with no more than 6 circuits you do not need a dis-connect.....unless that rule has changed.
 
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