Hi, all. I recently received two Zooz Zen51 dry contact relays, and installed one of them in an outdoor flood light fixture with a motion sensor. I thought I’d share my thoughts on the device in case anyone else is thinking about it. Note, I’m in the US and only familiar with US electrical wiring.

1. I didn’t notice until after I installed it that the recommended temperature is 32-100 F (0-38 C), and it’s marked for “indoor use only”. Well, it’s safely in an electrical box with a gasket and won’t get wet, so I’m too worried about the latter thing, but I am curious if I’ll have issues with temperature with it. It’s supposed to get really cold here in a few days, so we’ll see then!

2. Size - it’s pretty small, but won’t fit in every box, especially smaller switch boxes. There was plenty of room in the box behind the motion sensor light, but that’s not surprising.

3. It gives HA a control to turn the light on and off via a switch entity, which is what I expected.

4. I was surprised that the “switch” function (in my case, the motion sensor is the switch, but it could also be a regular light switch) status is not reported, unlike the Shelly 1 I have. Instead, there’s an event that is fired when the motion sensor turns on or off. So I can’t (directly - I could program a template sensor) see what the current status of the motion sensor is (i.e., is it calling for light or not?).

5. Pairing - the directions are a little sloppy on this point. To start the pairing mode, you have to hit the button on the device VERY quickly three times. The slowly blinking green light is the normal operating mode. This is clear when you look up the HA directions on their website, but it’s not really in the directions that come with it. The directions that come with it imply it’ll automatically connect once you hit the pairing mode in HA. (I installed Zooz’s smoke detector sensor a few weeks ago and had the same gripe then…but I forgot when I went to install the Zen51.)

(Note this also means you want to pair before you reassemble everything!)

6. There are a bunch of configuration options that can do interesting things. For example I could have it automatically shut off the light after a few seconds or minutes. Or I could “reverse” the operation of the motion sensor - turn off the light when it senses motion, and turn it on otherwise. (I can’t think of a use case for that latter situation, but the possibility exists, and I’m sure someone can find a use for it.)

7. Configuration is very easy through HA. Go to the device, click configure, then …configure it. Most options are explained well, but a few aren’t clear enough to use without looking it up. For an example of the latter, the “Auto timer unit” setting lets you choose seconds or minutes for the automatic turn off/turn on features…but it doesn’t say whether “1” is minutes or seconds. But this is a minor issue; once you have it configured once, you’ll probably not need to worry about it again.

8. The configuration option “External switch type” was interesting. I set mine to “Toggle switch”…then discovered, the next morning, that the light was on all night. In that mode, any state change of the connected switch (either on to off, or off to on) prompts a flip in the on/off status of the device. So what happened was that I had the light shut off when I went to bed, then the motion sensor turned off, and the Zen51 interpreted that as me wanting the light to come on.

“Toggle switch with fixed actions” was what I actually wanted (and is the default). Motion sensor comes on: light comes on. Motion sensor tells the light to turn off: light turns off if it’s on.

I haven’t tried the other three modes - Momentary Switch (seems self-explanatory), Split 3-way, and Garage door mode momentary (also seems self-explanatory). Split 3-way lets you use the Zen51 when there’s a 3-way switch setup (two switches controlling one light, usually).

9. Without any special actions in HA, the light works normally. But I now have the ability to turn it on for reasons other than motion, or turn it off manually when triggered by motion (i.e., I trigger it while walking the dog, then go to bed - my “bedtime” scene will turn it off, if it’s still on at that point). I’m planning an “all outdoor lights on” mode that will turn on, well, all outdoor lights, and this will fit right into that plan.

10. The other reason I wanted to install this was to provide a point that is closer to the detached garage in the hopes that the Z-wave switch I installed there would now be able to connect to the network. No go on that front, though. :( It should act as a relay but that switch might still be too far away. I might pull that other Z-wave switch back out and put a standard light switch in, and use the second Zen51 to control a different set of lights in the garage (it’s a long story as to why I’d do this).

11. The secure pairing failed. I didn’t retry it, so I don’t know if that was a fluke or something more; it did connect in insecure mode. Unfortunately to retry it, I would have had to exclude the device, then re-include it, and I was running short on daylight to finish this installation.

That’s all I have, I hope that helps someone who is thinking about these.