Zen thermostats broken in 2.4.x

dJOS · July 4, 2025, 10:10pm

My 2 Zen thermostats have not been working right since 2.4.x, and I’ve finally found the issue, the drivers are not seeing the “mode” changes even with command retry enabled.

After checking the logs, I’ve confirmed this. You can see that operating state is working “pending heat”, but the driver thinks the thermostat mode is off.

@bobbyD @gopher.ny @mike.maxwell

If I manually set the thermostat to off from the device itself, and then to heat, Hubitat recognises the state again. This is the only way to get it to resync tho, taking the batteries out and reinstalling them doesn’t work like it would normally.

dJOS · July 4, 2025, 10:28pm

My upstairs thermostat driver is even more confused, I manually put it on heat, but Hubitat thinks it’s in cooling state, despite the logs showing it was put in heat mode.

dJOS · July 4, 2025, 11:54pm

I was able to fix the operating state on my upstairs thermostat by pressing the “heat” command button in the driver.

Weirdly it doesn’t show in the logs that I sent that command.

mike.maxwell · July 5, 2025, 10:47am

Does it work correctly if you disable command retry?

dJOS · July 5, 2025, 10:58am

Hi Mike, Good question, I’ll turn it off and see if it behaves. Previous to 2.4.x it made the Zen’s much more reliable.

dJOS · July 5, 2025, 11:01am

Ok, it does appear to be working normally with command retry off.

I was able to turn the thermostat off, back on again, and change the set point without issues.

mike.maxwell · July 5, 2025, 11:20am

Ok with command retry enabled it gets into a funky state after the off command is issued?
So off works, then no other commands are sent through?, is that accurate?

dJOS · July 5, 2025, 11:26am

As far as I can tell yes that is accurate - it seems like it'll turn off the thermostats, but when it turns them back on, the mode doesnt get reported back to hubitat.

eg this morning, the downstairs thermostat was in heat mode, but hubitat thought it was off, even tho it was RM commanded it to heat and the 22.5c setpoint.

The upstairs thermostat behaviour had extra oddness, I was cycling through the modes via hubitat, and then from the unit, to try and get it to sync up, and it thought cooling state was active at one point while in heat mode. I suspect that is just a side effect of the states not updating correctly.

dJOS · July 5, 2025, 10:14pm

Just to confirm, everything worked normally this morning with command retry off.

dJOS · July 8, 2025, 9:27pm

Hi @mike.maxwell Is this issue fixed in the latest releases?

mike.maxwell · July 9, 2025, 11:22am

There haven't been any changes in the latest related to this issue

dJOS · July 9, 2025, 11:33am

No worries, just though I'd ask.

mike.maxwell · July 9, 2025, 2:13pm

I'm not sure where my zen tstat is, but I tested command retry with a virtual thermostat and I'm not seeing any issues, of course the virtual stat reports immediately.
Of note command retry for thermostats only uses command retry for the following commands:
"setThermostatMode"
"setThermostatSetpoint"
"setCoolingSetpoint"
"setHeatingSetpoint"
The individual Heat, Cool, Off commands are not supported and are ignored.
I don't know if this is related to the issue or not.
I'll try to find my zen thermostat and see if I can replicate the issue

dJOS · July 9, 2025, 9:20pm

Thanks Mike. It's odd because command retry made the Zen's more reliable prior to 2.4.2.x - the main issues were not responding to mode changes and setpoints.

I dont have common wires on my systems, and no-one in Australia knows how to support 24AC control systems anymore. All the popular systems here are from Japanese/Korean companies with proprietary low voltage DC thermostats. So I'm stuck with my battery powered Zens.