You can use the case statement to determine the temperature range
Case 77-999 set fan speed to high
Case 74-76 set fan speed to medium
Case 68-73 set fan speed to low
Case 0-67 turn fan off
Then you can add additional qualifiers such as thermostat operating state is on off and have the cases adjust accordingly. I.e. if the thermostat turns on a/c you can adjust the fan speed above to lower speed or turn off depending on what you prefer.
You can also add lots of additional things like:
How to turn off when you want (when you don’t want them to automatically turn on again)
Manage multiple fans
Different parts of the day
Perhaps only some months of the year depending on where you live.
And account for home/away if you want them to turn off when you are away.
I have my pistons working using if then else statements. And it seems to function the way I expect however I’m looking to elaborate on the art as it were so for example if we the humans are going to be out of the house for longer periods I want to bump the temperature up a couple of degrees for each fan speed I do want to keep the pets comfortable shile we are there and of course I don’t want to keep them running full tilt during the Winter.