Thermostat Control Philosophy

I am about to install a CT100 Thermostat and have started thinking about how to design my rules.

So in an uncharacteristic move (right @dot850 ?) I am going to ask how others have done this.

On the one hand I like the CT100 being able to control the system in case my PI loses power (I mean OH or custom rules NEVER crash, right?) but it is hard for me to take actions ahead of the CT100

So the other way would be to have rules switch the MODE from Off to Cool or Heat as needed as well as turning on the Fan (while the system is Off and if that does not do enough THEN go to Cool), but then if something crashes I might be stuck in Off mode…

While writing this I realized that I likely could use the first method and look for 1/2 or 3/4 a degree (F) difference to decide when to take action…

So am I on the right track?

Are there any different (possibly better) approaches?


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What do you mean by take actions ahead of the CT100?

I do not know how the CT100 works, but I assume it can be programmed (via Zwave) to operate on it’s own schedule?
For example at 5pm everyday lower the temp (without OpenHab intervention). I would set it up this way so the device is independent. Then OpenHab could intervene when it sees fit. For example you come home early and you’d like the air to turn on at 4 today only.

I believe there are no scheduling capabilities on the CT100. I have it but haven’t installed it yet.

Yep. Looks like you are right.

If you can’t set a built in schedule. I don’t think there is any other way than use OpenHab (or some other zwave automation) to control the thermostat.

If anything fails, your thermostat will be stuck at the last setting you commanded.

Well, probably not what you want to hear if you have decided to go with the CT100, but the MAX! thermostats can do better.
They can be assigned a time schedule that they will follow without a need to communicate anywhere, and that’s what they’ll do in case your Pi fails (it’s always the Pi, isn’t it? custom rules can’t fail, we’re all perfect programmers :wink: ).
The schedule is about target temperatures, the thermostat keeps regulating room temperature automatically.
And of course you can still override that schedule from OH.

Now of course that just works for radiators, so if you have floor heating, well, you better get your rules right then. I have both, and for floor heating I just use OH-controlled temperature sensors and valve actors, so if my Pi fails, I’m about to be cold or sweating or both, trying to recover it. But that’s something you should prepare for anyway, so why not solve the issue with a reasonable redundancy/backup/recovery concept plus careful programming.

The more I think about it, I am trying to keep the family away from the thermostat by making them comfortable.

I can’t try to second guess the thermostat, but I can add extra sensors in the MBR and/or MBR Bath to turn on the fan to get rid of humidity from a shower, etc

Other things I might like to try is if the outdoor temp is lower than my set point or going to be dropping soon due to the sun going down, temporally raise the set point and run the fan to keep the people happy…

I also want to still allow people to use the thermostat on the wall to make adjustments without needing to use openHAB UI to control things…

I guess I’ll just have to dive in!

ps. I live in Florida, so cooling is my biggest electric expense

@w2vy I’ve just gone down this route after my Ecobee suffered an early death and the shipping on a replacement warranty item made it uneconomic. I now use OH on my Pi3 to control my heating. For Heating / Cooling changeover I use a combination of factors to steer its decision making.
I have 2 Switch items Morning Cooling Mode and Evening Cooling Mode which are used to remember the previous days setting. I then update the thermostat operating mode with these on scheduled startup.
I then change mode again if the temperature is significantly in the wrong direction, currently set to 2 degrees Centigrade. Or to put it another way, if the system is set to heating and its over 2 degrees C warmer than the set point, change to cooling.
Finally when the system goes off for the evening I update the Evening Cooling Mode / Morning Cooling Mode with the current mode.
I also delay system startup if the windows are open.