ZEN17 and using inputs to detect 24V on/off state (UNRELIABLE)

Hi all, I am fresh on the Hubitat boat. I am a long-time SmartThings user and will be migrating everything to Hubitat. However, I decided to crack open the box to control an HVAC upgrade that I just installed.

So, I am using a Zen17 to control my Energy Recovery Ventilator (ERV).
I am controlling the run and boost switch with Hubitat and have integrated my Airthings View Plus sensor to help control the various states of operation of the ERV in response to air quality.

I need to be able to monitor when my thermostat is calling for the fan to run via the green wire, which will provide 24VAC when it calls for the fan. So, I need to configure input one of my ZEN17 as a Dry Contact (on/off) sensor. Makes sense to me; however, when I do that, I never get a sub-device for the dry contact sensor.

If I choose another sensor type, the sub-device will show up. In reading the forums here, I can see that others have successfully used this type, so I am not sure what I could be doing wrong. Any hints or suggestions?

[EDIT 11/13/22]
If anyone else is considering using the ZEN17 for its input sensing capability, be aware that it appears unreliable. I chose this device for an HVAC automation because it is advertised as capable of sensing voltage or dry contacts as an input. I am trying to have a piece of equipment follow the thermostat state and be enabled under specific circumstances. However, what I am finding is that the Zen17 will often get stuck sensing that the "contact" is open or closed when the opposite is true. I have even tried using a relay and the dry contact input rather than directly sensing the voltage and I am still seeing the same behavior. Just this afternoon, when the Tstat turned the fan off, the Zen 17 still showed the contact sensor as closed. Even after I removed the relay from the Zen17's ports, it still shows as closed. It has stayed this way now for 40+ minutes and I will likely have to power-cycle the Zen17 to get it to start sensing properly again. So for me, I find it unusable in its current state.

Are you using the Zooz driver?

I am using the default available ZEN17 driver that is built-in to the latest Hubitat software, which I assume is from Zooz. I have also tried out the companion driver that is just used to manipulate the settings and it verifies that I have selected stuff appropriately in the main driver.

If you want to monitor the 24VAC line a relay (first search result) will supply dry contacts to connect to your Zen.

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I think it can handle the 24v.

I just looked at my Zen16 page. I'm using the Hubitat system driver as well.
This is what my Zen16 looks like (I named those relays):


You know, Zooz has pretty good customer support. I sent an email the other day, and they responded the next day.


Aha, it sure can. :upside_down_face:

  • 2 Dry Contact or 12-24 V inputs to monitor HVAC systems, magnetic door sensors, or analog leak alarms (use either dry contact or 12-24 V input for R1 and R2 at a time, never apply voltage to the Sw terminals)

I believe 'dry contact' usually means no voltage. I don't think the 24 v terminals are 'dry contacts'.

I was looking at this: https://cdn.shopify.com/s/files/1/0218/7704/files/zooz-700-series-z-wave-plus-universal-relay-zen17-ver1.0-manual.pdf

Could you have been messing around changing the values for Parameter 2?

edit: Now that I look closer, I bet you changed Parameter 2 value to 10, meaning the yellowed out stuff will come into play.

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I did contact Zooz explaining that I want to monitor the G wire of my HVAC for 24 volts, and they want me to send them a PDF manual for my 22-year-old Goodman Furnace... HVAC wiring is quite ubiquitous, and I would think they would not need a manual to understand what I am contacting them about.

What do you think about that parameter thing?

The latest driver bypasses those old instructions via the configure button. That parameter gets changed for any sensor type and if I select any other sensor type, my sub-devices get created. So I am at a loss as to why it will create a motion sensor sub-device or a water sensor sub-device and just not the on/off dry contact sub-device. I am thinking there must be a bug in the code or something.

I replied to Zooz support with a generic HVAC wiring page. Hopefully, that will be good enough.

It really should not matter what sensor type I use, other than being confusing, so I tried motion and water and both of those would show dry or no motion until I applied voltage to the V1 port, at which point they showed motion and wet, the only problem is they stay that way even after voltage is removed.

Maybe support will be able to point out what I am doing wrong in the procedure or wiring.

the parameter above is to control a relay not monitor it.. maybe you have it connected to the wrong port.. you dont want it on a relay port.. relay is for when the zen acts like a relay and opens a garage door, gate etc.
i would try the low voltage alarm inputs as specified in the manual.. wires to c and vc..

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Then there's paramter 10:

Input Trigger for Relay 1
Parameter 10: Choose if you’d like the connected
input (switch) on S1 C / VC C to trigger the load
connected to R1 or if you want to use the input
reports for monitoring only and separate the
output from the input.
Values: 0 – input trigger disabled; 1 – input trigger
enabled (default).
Size: 1 byte dec.
Input Trigge

You could then do parameter 2 for something that worked.

They should really call that "Input type for port 1" as what you choose there will determine if you are setting up a control for the relay or a sensor along with parameter 10 which connects/disconnects that input to the relay for control. I have tried contact sensor, water sensor, and motion sensor, all exhibit the same behavior, they will trigger when they see voltage but never reset.

You're mixing concepts with this.
If you're supplying 24VAC to the Zen17 then you need it to be configured to sense the presence of voltage/current from your circuit.
If your Zen17 is configured for dry contact usage (e.g. via a relay) that would simply monitor whether a switch is open or closed.

Any chance of some pictures? :thinking:

Lucky you haven't fried the zen the inputs you appear to be using 24v on are not designed for that. you need to use the 2 inputs i mentioned above c and vc

Not the case and the inputs are totally designed for that. I am using V and C ports as specified in the documentation.

Not at all mixing stuff up, you folks are just reading the software labels too literally.
By selecting "Dry Contact On/Off sensor" I would simply be selecting an input sensor that would report on/off. If I then want to trigger that input with actual dry contacts, I would use the S and C port for the input. If I want to trigger that with voltage, I use the V and C ports. Which is what I am doing and I have no confusion about that. My post was specifically that when I select that input type the driver is not creating the sub-devices as expected.

Zooz support has already verified that this is due to a bug that they say is on the "Hubitat" side of the house, but that I should be able to use any other sensor type the same way, just the labeling would be off for what I am doing. However, as I noted above, doing that gets the desired trigger condition when 24V is applied and never resets when the voltage is removed. So I am now querying them on that issue. The input may need an external pull-down resistor, but that would be odd as I would expect that to be on-board already.