Electrical Wiring - New Circuits (Added pics)

Question

I have run two 12/2 Romex “Home Runs” to a junction box, each for 120V to Circuits A and B.

T-off at the junction box, two 12/2 Romex lines split to one 2-gang box, and two more 12/2 Romex lines split to a second 2-gang box. So each 2-gang receptacle box gets 2 Romex inputs, each feeds a 120V 20A GFCI receptacle. (40A available in each box on Circuits “A” and “B”).

Four GFCI’s (Line inputs only), leaving load outputs taped-off.

(NOTE: I understand I could have eliminated the junction box and daisy-chained the GFCI’s to downstream standard receptacles, but I didn’t because I’m feeding the 4x4x2 metal boxes through a single rear-hole and I didn’t have 12/3 Romex to run a MWBC and couldn’t evacuate another pair of Romex 12/2 from each box. The junction box also happens to be located between the two receptacle boxes which are in different opposite directions.)

Question 1: Even though these are two distinct circuits, can I use a “2-Pole Breaker” to power the “HOT” conductors for each circuit such that opening the one breaker removes power at both receptacles in each box?
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In the (4x4x2) junction box, I intend to make the following connections:

• Wire-nut 3 “Circuit A” Hot wires together
• Wire-nut 3 “Circuit A” Neutral wires together
• Wire-nut 3 “Circuit B” Hot wires together
• Wire-nut 3 “Circuit B” Neutral wires together
• Wire-nut 6 Ground Wires together; connected through-wire to junction box chassis

Question 2: My Grounding Wire Nut connector is rated for 5 #12 wires but I need to join 6. Can I use a greenie to reduce 3 wires from Circuit A to one wire, and another greenie to join the one reduction wire to the remaining 3 wires from Circuit B, and then connect to the chassis? Or get a bigger wire nut that doesn’t have the hole in it and do a pigtail to chassis (7 #12’s)?

Thanks, Rich

Answer 1

"I think we're gonna need a bigger box!"

If it's not too late, change out the 4x4 box that will have the GFCI receps for a 4-11/16" box, with appropriate domed cover or 2-gang mud ring. Two GFCIs in a 4x4 will be a very tight fit with almost zero side room... but 4-11/16" are a comfortable fit.

No, we're definitely gonna need a bigger box.

I now realize you're bring six 12/2 cables into the box. And also having 2 GFCI receps there. Aside from the GFCI-crowd problem, which you will find heinous, you also have a statutory (by the law) over-fill problem. That is far too much for a 4x4 box. Let's crunch the numbers.

• Hot and neutral wires entering the box = 12
• Grounds entering the box = 6, but you get 4 for the price of 1", so 2.
• For all cable clamps together, 1 count
• 2 counts per receptacle, so 4

That is a total of 19 counts. Uh oh. Now we multiply that by 2.25 cubic inches for #12 wire. Result is 42.75 cubic inches. This is way too big for a 4x4 box, even a deep one, which is 30 cu.in. A 4-11/16" box is 42 cubic inches, and presumably you'll have a mud ring or domed cover that will get you over the top.

The ground wires go to the metal box first!

They do not ground to the receps. Or to be more precise, cable grounds must be attached to the metal box first. If you remove all receps, ground to the metal box cannot be interrupted!

That means all cable grounds must go to the box. You are trying to wire them to the receps and ignore the box, and that's wrong.

So you must - always with metal boxes - you must get a #10-32 screw and put it in the pre-tapped hole made specifically for grounding. You then pigtail off of that.

"But that's now 7 wires I have to get on a nut!" Not quite. There are several ways for receptacles to take ground from the box. With switches, it's automatic!

Or, feel free to drill more holes and use self-tapping screws, as long as they are -32 thread pitch or finer. You can have as many ground screws as you want, just don't put them on knockouts!

In many cases the receptacles do not need a ground wire. They can pick up ground several ways:

• They are making hard, flush metal-metal contact with box parts (i.e. screw bottomed out, not floating on a drywall ear). Doesn't work if there's rust or paint or those little paper squares that capture the screw.
• Some receps have a scraper that touches the screw thread; these are called self-grounding and can pick up ground off the screw thread even if the screw isn't tightened down hard flush. You may find that feature on many GFCI receps.
• You can also have a pigtail from the recep to a ground clip that grabs the edge of the box.
• Switches can ground via the screw heads even if they're floating up on the drywall ears.

Use gray tape to distinguish the neutrals.

Here's the trick. In cables, white wires can be remarked to be hot, but that is the only remarking allowed (can't do black to neutral) until you get to #4 wire size. So...

On the second cable, enthusiastically mark the neutrals on both ends with gray tape (e.g. spiral down the whole wire). That is the allowed "alt" color for neutral. Also lightly mark the hots with gray tape (e.g. a wrap the width of the tape). This does not make black into a neutral, because it can't. This clearly identifies the pairs.

The metal boxes must have proper cable clamps

I thought I heard you say you were feeding all 4 cables through a knockout. I could see where four 12/2 Romex could be crammed through a 3/4" knockout, but not legally. Every Romex cable entering the box needs to do so at a listed cable clamp, whose purpose is to prevent the wire from taking damage from the sharp box edge.

Don't use LOAD unless you are meaning to protect onward outlets.Almost every GFCI (except the dangerous Chinese cheapies sold on Amazon) will support 2 wires under the Line screws via the "screw-and-clamp" back-wire technique.

Question 1: A 2-pole breaker is totally fine

Yeah, go for it. Obviously the common trip functionality is unneeded and might be annoying, but there's no harm at all in this.

Question 2: Daisy chaining wire nuts is fine.

Yes, you can handle large numbers of wires on a nut by "daisy chaining" 2 nuts with a pigtail in between. Remember the stuff I said up top about "Ground the box FIRST" so for instance have the box pigtail run through a Greenie where it picks up the 4 cable grounds, and then goes onward to a regular nut where it picks up the recep grounds (if those are even needed... if you have self-grounding receps or flush contact, don't even worry about that).

Answer 2

Yes you can use a 2p breaker for individual circuits (the neutrals must remain separate), and you can daisy chain wire connectors in order to connect all grounds.

Answer 3

Note that you may not have realized but the safety ground wire in 12-2 Romex is sometimes a smaller AWG than 12. In situations where this is allowed by code it may be a 14AWG bare copper wire.

Knowing this you can re-check the wire nut capacity for more conductors.

If I was addressing this I would bundle the three safety grounds from Circuit A together with a pigtail so that wire nut just has 4 conductors in it. Then bundle the three safety grounds from Circuit B together with another pigtail and the other end of the first pigtail so that wire nut just has 5 conductors in it. That second pigtail connects to the green screw in the back of the junction box.