Control Z-Wave heating recommendation

Setup, Configuration and Use Beginners
1

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.

  1. Controlling heating using temperature readings from the thermostat.
  2. Gas boiler hot water temperature control as I have a Z-Wave temperature sensor attached to the water tank.
  3. 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?

2

HI Michael,

I have the same setup as you, so I’ll be watching this thread with interest.

Presently I have a bunch of rules that control my heating automatically along with the manual override. For me this seems to work well, the house is always at the right temperature, I use outside temperature reported by my weather binding as the basis of my rules.

Anyway, it’s good to see I’m not alone in my setup.

Garry

3

Good to hear that others at least are trying to do the same as me with
OpenHAB, hopefully I can then get something which satisfies me.

To give a little bit of background, I have come from using a heat Genius
system, which is essentially a preconfigured system of Z-Wave devices
and their hub with their own control software. However I did find a few
limitations and things I was not keen on with the Heat Genius software
and thought I would give OpenHAB a go, at least I can reuse most of the
devices, really just a hub replacement.

I think getting the rules right is going to be the main task. I thought
I had got the hot water one worked out, until I had a realisation that I
was relying on it reaching a temperature before turning off. All fine if
erything works as planned, but what happens if the pump fails to start
for some reason? My guess was that it would just keep the boiler on, not
the best thing if the pump isn’t going. Probably should have something
to monitor whether the temperature of the water increases whilst
heating, or may be a more basic one to just turn off after a certain
time regardless of temperature.

To me OpenHAB seems to be providing the basic building blocks requiring
more work to put it together to get a working system. However there is
something in gaining that knowledge of what really is going on which I
like. In Home Assistant I came across some things not quite working as I
expected but its less clear why when you are working at a configuration
level.

4

I have a very basic setup that works at present. But its by no means very clever.

I have two Thermostats, one in the living room and one of the first floor landing. They are both associated with OpenHAB, so that I have full control. To start with I associated them with the boiler controller and that effectively bypassed OpenHAB, not what I was hoping for.

the rules I have in place at present are;

Outside temperature reported as being below x degrees - Change the SetPoint to y.
11:30pm, so off to bed - Change the SetPoint to 19.0 on both thermostats. Lower for Summer.
Sunrise - Change the SetPoint to Y. Depending on the time of the year depends on the SetPoint

I also have three ST814 environment sensor that report temperature and humidity. My idea was to find the average temperature and work out what SetPoint I need.

Very basic but a good starting point for my needs.