3 way wiring w/o neutral

rotormonkey · February 20, 2021, 2:55am

So in the interest of not blowing up any more switches I just wanted to make sure I’ve got all my ducks in a row and that we 100% understand each other etc, etc. sooo…

I ventured into the attic after work tonight, and found the junction box. It was pretty much what I expected to find:

So, here’s a full diagram of everything that’s going on in the circuit and how I plan to wire it:

Here’s photos of everything wired up.

Box A:

Box B:

The light box will be wired exactly as it was originally except this time I’ll use a different/new dimmer bypass.

If all goes well when I turn the power on, then I’ll do this:

This time I’ll use a different/new Aux switch.

Are we on the same page? This should all 100% work right?

Bry · February 20, 2021, 4:26am

Take another look at the wiring in the light box. You’ll notice that the hot is being fed to the junction box via the WHITE conductor:

It looks like in the junction box that hot is transferred to the black conductor. Is that going to Box A? So is the hot in Box A the black?

So I think your concept is correct but the wire colors in your drawing may be off. Your drawing has the hot entering the j-box on the white. Unless you’ve re-wired the light fixture, that’s not correct. If the colors in your drawing or off, that may affect the logic so I would double-check those connections. It’s a bit hard to tell without the Romex in the j-box labeled. I’d meter those conductors in the j-box as well.

rotormonkey · February 20, 2021, 5:27am

Hey good catch!! I actually did the drawing before I went and looked at the junction box. The white wire in box A is definitely the hot wire, not the black (I metered it). So here’s a revised drawing to show the colors accurately:

So the way the switches are wired should be correct. Correct?

harjms · February 20, 2021, 6:34am

Looks good to me.

Bry · February 20, 2021, 2:36pm

Looks good to me too.

rotormonkey · February 20, 2021, 6:47pm

Mystery solved!

So I was still pretty hesitant to just hook everything back up the way I had it in the first place… So I took a bit of time this morning going over everything one more time before I hit the power and I noticed this:

Those screws line up exactly with the line and load terminals on the switch! And totally explains why everything worked until I put everything back together the last couple times.

So after screwing them in a little more and taping the switch everything is working as expected now!

I can’t believe I missed this the first two times, but happy it’s all sorted now.

I can’t thank you guys enough for your time and patience. Even if the wiring itself wasn’t the cause of the problem, it was worth the price of admission just having you guys validate that nothing was wrong on that front. And the suggestion of using the ground as a return for continuity testing is gold. Thank you again!

Eric_Inovelli · February 20, 2021, 7:22pm

What a rollercoaster ride! Glad you got it figured out

Thanks @harjms and @Bry for the help!

Bry · February 20, 2021, 7:33pm

Glad you got it working! I saw those but didn’t realize they stuck out that far. There are retrofit boxes that have side screw mounts, but that’s not one of them lol.

Also, an electrical tape wrap to cover the screw terminals never hurts!

stu1811 · February 20, 2021, 7:51pm

Every time I work on a switch/outlet

Eric_Inovelli · February 20, 2021, 8:44pm

Is this something you think we should put in our instructions? Maybe as a strong suggestion?

Bry · February 20, 2021, 10:22pm

Meh. It’s not a bad practice but the devil’s advocate will say that tape will decompose over time.

All the NEC says is that the energized contacts shouldn’t come into contact with anything, but doesn’t specify how. This was a practice that is/was more common with metal boxes than plastic ones.

Moreover, that box wasn’t designed to be installed that way.

harjms · February 20, 2021, 11:02pm

Could be a recommendation. I wrapped all mine as good practice when I did it. Personal preference I suppose.