So, this is what I found out as I changed the Thermostats to Celsius and then back to Fahrenheit…
When I go to the XR524’s setup and change it’s base unti to Celsius, without changing anything in OpenHAB, like magic it starts to report more frequently or with better granularity. See the Grafana chart below. I flipped it to Celsius close to midnight on 27/Jan. Visible change.
I did the same with the second unit, and, same behavior.
Then, after a day or so I flipped it back to Fahrenheit around 23:00 of 28/Jan, and look what happens, I lost granularity again:
Flipped it later back to Celsius and got granular measures again.
So… I don’t know, but, based on my experience I think the Trane XR524 operates internally in Celsius, and then converts to Fahrenheit with zero decimal point math. That is a plausible explanation why Celsius has such granularity (1 decimal point precision) whilst Fahrenheit doesn’t.
I am going to keep these Thermostats because family is Celsius-enabled, it might even be good for the kids to practice their Celsius, and I like the clean looks.
But if you’re wanting a thermostat for OpenHAB and Fahrenheit only operation, I think Trane XR524 is not for you.