Replacing dimmer with white wire on line / load?

Hello everyone,
I’m probably going to call an electrician to install in these locations, but I thought I’d post here if anyone had some insight. I inherited a house with two Lutron Maestro switches in the same room that independently control two sets of recessed lights. I figured they would each be a 2-way switch and I’d be done in 20 minutes, but I was wrong.

The light switches are flanked on both sides by electrical outlets, not sure if that matters. Here are pictures of the wiring, first the left switch and then the right: Imgur: The magic of the Internet

The left switch seems normal, but I have no idea what’s going on with the right switch. After some googling I thought maybe they repurposed the white wire for hot, but I tested it with a multimeter and got weird readings. Line-side the white wire is at 20v above ground potential, and load side it’s at 0v. The left side switch has a bundle of white wires capped in the back which I assumed was neutral, but on further inspection it looks like those white wires are also tied to the white wires that feed the right switch. Indeed, the black wires in the left switch are tied to a cap in the right switch as well, though I’m realizing now I should have done continuity testing while I had the power off.

I’m not an electrician but I haven’t seen anything like this while prepping to install my switches; so far I’ve got three in the house and they were all pretty straightforward. Does anyone know what’s going on with these?

Can’t diagnose much just from pictures, sadly (can’t see to the back, can’t see what cables each wire enters from, etc.). Getting professional help on electrical circuits you’re not understanding even after some work is probably the smart choice!

It’s common to drive some outlets off the same circuit as lights, that could come off from either switch. When using a “switch loop” it’s common (and accepted in the code) to re-purpose the white wire in an NM cable as a hot–but, when doing that, you’re supposed to wrap some black tape around each end of it, to make it clear, and I don’t see that here. Of course, no strong reason to believe the previous installer followed code compulsively.

Those outlets near these switches; you would have mentioned if they were switched, right? They’re hot all the time? Still, normal enough to power them off the hot in any convenient box. I do try to keep the lights in a room on separate circuits from the outlets so that you don’t lose the overheads and the floor lamps at the same time, but it’s not required last I checked.

The bizarre voltage measurements bother me; they suggest something is going on that’s wrong, or at least that I don’t understand.

If I were doing this I think I would take more photos, and label some wires, and then disconnect everything. Then it should be easy to figure out what’s input and what’s output at least!

But, again, messing with wiring you don’t really understand is something that one can, without loss of honor :-), refer to a professional!

Don’t get too far down into the weeds with the voltage testing. If you’re starting with a working configuration, you’re really only differentiating hot or not. It’s not unusual to see ghost voltage, sometimes referred to as phantom voltage, caused by capacitive coupling . . . particularly in multi-way configurations. Most commonly used meters can’t tell the difference between phantom voltage and real voltage.

So while there are not absolutes, seeing voltage substantively less than 120VAC on conductor that isn’t supposed to be energized is likely benign.

Given your situation, probably best that you are consulting with an electrician.

Also, make sure your voltmeter is on “AC”, not “DC”. Measuring AC with a the meter on DC will give unreliable results.

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