Zooz ZEN51 Relay

Recently moved into a new old house. The light switches don't have a neutral in the box and thus I can't use a standard smart switch.

My thoughts are to use a ZEN51 relay at the light itself. What I don't quite understand is how the switch input will work if I wire in my existing dumb light switchs.

If I turn the dumb switch on, light(relay) goes on, If I turn dumb switch off light(relay) goes off. But if light is on from dumb switch and I trigger the relay remotely from my hub does the relay drop out even tho the dumb switch is still on? And then do I need to turn the dumb switch off and back on if I want it to turn the light back on using the dumb switch?

Hope that made sense.

That would be my guess but I cannot confirm, it might work better in a 3-way setup because there is no on/off position for the switch they are all toggles. But even in a 3-way it is either powered or not powered. I was thinking about putting one of these ZEN51 or a ZBMini in my basement lights (3-way) for the same reason, they wired the switch with a hot loop and the neutral is in the fixture. I will be interested if anyone can confirm how this would work.

Main reason I'm doing this is this is one place that should have had a 3 way. I plan on using a button or some such in the other location where it would be handy to turn the light on/off.

You could go lutron caseta and use the dimmer as prime (no neutral needed) and put a pico switch at the other box to create the 3 way. (Warning, batteries in the pico switch need to be changed around every 10 years)

Parameter 7 has the answer. " Parameter 7: Choose the type of wall switch connected to the relay and it’s on/off behavior.

Values: 0 – toggle switch (device changes status when switch changes status); 1 – momentary switch (one-button switch like the ZAC99); 2 – toggle switch with fixed actions (always toggle up for on, always toggle down for off); 3 – 3-way impulse control (for selected 3-way scenarios, refer to the notes in the wiring instructions for your set-up); 4 – garage door mode (simulates a momentary push button switch in the Z-Wave interface, used for garage door opener applications). Default: 2.

Size: 1 byte dec"

If you set this to "0" it will change the state of the relay whenever the any switch in the 3-way is changed. This works great. Now for the bad news. This works great in my "test setup" with the two 3-ways mounted in a single switch plate, 2 inches apart. In real life, there is an issue with the inductive voltage often found in 3-way circuits. Much of my home is wired like yours with switch loops with the neutral only at the fixture. The ZEN 51 seems to need 0 volts on the line for it to function using the existing switches. I was showing less than a volt on my cheapo meter and it was enough to hold the switch in its current state. I could remove and touch the .3 volts wire from the ZEN and it switched back and forth. The ZEN 51 always works when controlled from HE but won’t work with the existing switches. I did get it to work with a single switch that had the neutral in the box. There are a lot of uses for the ZEN if controlled by HE but in its current state I couldn’t use it for what I was trying to do. I had some brief back and forth with Zooz support but I put this one in the box to try again later. There was another post Zooz Zen51 and Zen52 - double relay & dry contact with some more info.

The existing installation is not 3 way. Therefore reason for doing this is to have control from another location also.

I don’t want dimming at all. Seems like all the non neutral switches are dimmers and also highly dependent on load.

This sounds like what I want. No matter where the existing switch is, up or down, changing it's state will change the relay, either off or on.

Is that a parameter that can be changed from the driver? Or how would that be done? I don't have the relay yet, so can't try it.

Well I suggested the dimmer as for me personally it's no big deal if a light ramps up for a second vs instant on. The pico's then can be mounted anywhere for remote and controlled by hubitat as well. I would think that would fit all your criteria