I have a Secure SRT321 thermostat and Secure SSR302 dual channel boiler controller. The one channel controls heating and the other controls hot water. I would like some advice on how best to control it from OpenHAB.
I have seen recommendations to directly associate the thermostat with the controller using the thermostat mode association group. I see two advantages to this, thermostat and heating continue to work should the OpenHAB controller fail and the other being that the SRT321 has TPI software for better and more efficient control of the boiler.
I though see two problems with the above. Firstly as the SRT321 is a battery device it will only receive updates from OpenHAB whenever it wakes up, so there will be a delay when OpenHAB tries to change the setpoint temperature. The other problem is that ideally I think you are meant to associate the thermostat to the specific end point rather than just the top level Z-Wave node and I do not see any option in habmin to associate with anything other than top level nodes. I have read that may be this is done in a development version though, so may be it will soon come to a release version. However I can make the association using other software such as OZWCP, will this association continue to exist when running OpenHAB or will OpenHAB revert it back to the settings in OpenHAB?
I can see other reasons why to run it through OpenHAB, things like greater control as rules can then decide what to do (eg. rules may ignore attempts to alter the setpoint from the thermostat dial at certain times and just choose to use a value set within OpenHAB). However I would guess then things like the TPI feature will be lost and I may need to implement my own thermostat algorithm for when to turn on and off the heating. When I had a look at Home Assistant I see it has a Generic Thermostat component (inspecting source code says it is simple and has no TPI). Does OpenHAB have such a component? My searches seem to say no and all I find is people writing rules to solve this.
If I have to write the thermostat feature myself, is rules really the best way to do it? I possibly have three instances where this could be used and rules don’t seem that reusable.
- Controlling heating using temperature readings from the thermostat.
- Gas boiler hot water temperature control as I have a Z-Wave temperature sensor attached to the water tank.
- Electric hot water temperature control, the tank temperature probe is connected to a Secure SIR321 electric switch controlling an immersion heater.
My thought is may be a binding with a virtual thermostat thing. This would work a little like the expire binding taking input from changes of an item, another item for setpoint and then output on a third item which is a switch. I would imagine the virtual thermostat thing to have configuration values for min/max temperatures, setpoint tolerence, cycle duration, etc. May be in time it could be extended to include TPI features.
Is the binding approach a good way to go for a virtual thermostat?