I went to replace a light switch last night and there was a single NM cable in the box. Ground is connected to the metal box. I confirmed white is always hot and black is switched. This is a non-neutral configuration, right?
Can I use an LZW30-SN in a non-neutral configuration or do I need to use a LZW31-SN?
Yes, that is a non-neutral. As you suspect, you’ll have to use a dimmer because the switches require a neutral.
You need the LZW31-SN. On/off switch doesn’t work with non neutral setup.
Keep in mind if this goes to an outlet, you can’t use a dimmer there and you are stuck with either keeping the dumb switch or otherwise running a neutral to the box (not allowed to dim an outlet).
Switch only controls an overhead light as far as I know.
Then get the LZW31-SN, it will work for you. If you don’t want it to dim the light, set Parameter 1 to 0 (no ramp time, instant on/off), and set Parameter 9 and 10 to be 99 (default to 99% when turned on). Then you essentially have an on/off switch.
I had this situation with an outlet. Easy fix here, wire outlet to be hot all the time and send neutral and power to switch. Switch now has power all the time and can be associated with smart bulbs in a lamp. Turn off the internal relay of course.
Not sure about WAF if I configure the dimmer as on/off. Maybe I can snake a new cable from the basement.
Um, would you believe it’s a switch with a really big LED??? 
Ha. Or put white tape over 3/4 of the LED.
Why not? Functionally the only difference is the switch will have a bigger LED on it. I’ve got a switch working like that right now- I find it’s easier to just put Red dimmers everywhere, hardwire the switched outlets (as @djordan2112 suggested), and wherever I don’t want dimming just program the dimmer for 0 ramp time.
Don’t ever,I repeat ever do firmware upgrades when she is home!
Just had an idea. Could I connect the white(hot) to line and black to load, and disable local control and use an illumin bulb?
Not exactly, but you can do something like this.
First, white is almost always neutral.
What you would do is go up in the light fixture, tie all the whites together and all the blacks together. What that does is make the light fixture always on, and feed hot (black) down to the switch as a raw power feed. If you do this you should put a Dymo label or something in the box that says HOT & NEUTRAL - NO LOAD CONTROL or something, so someone in the future doesn’t try to wire in a dumb switch and cause a short circuit when they turn it on.
Then on the switch you have, wire it to hot and neutral (nothing on load). Associate the switch to an iLumin bulb and you will be good to go.
I still say the dimmer is easier though…
No. At the fixture, you will need to wire it to be hot all the time, and send power and neutral to the switch. Then you could use Smart bulbs in the fixture and control them from the switch.
I know white is almost always neutral. I was surprised when I pulled the switch out and touched the non contact meter to the white. With the switch off, white is hot and black and off. With it on both are hot.
Thanks for clarifying the wiring.
I’ve seen it done that way a lot in 3 wire setups. I think the reasoning was to make it easier to replace the fixture. Black to black, white to white. It doesn’t matter as much at a dumb switch, if the lights come on when the switch is down just reverse it.
That is exactly how it should be wired for a dumb switch. The hot and neutral are at the light box. The neutral connects to the light. The black incoming hot is wired to the white conductor going to the switch. It’s returned to the light, switched, via the black.
This was the first switch I’ve pulled out that didn’t have a neutral so it was unexpected.
No worries. Just letting you know that’s how it’s done so you don’t think it’s incorrect as-is.
Got it. Thanks.