question on self automation

[arjan_m]

Hello I'm a software engineer and like to be able to control my heating remotely.
Using the manufacturer solution exposes my data, and I I'd like to avoid this.

What I have now
---------------------
Below is preinstalled in my house. This is a working setup
-Intergas HRE boiler
-Honeywell wireless round modulation thermostat
-(presumably) a honeywwell accompanied boiler interface plugged into the boiler internally.

For remote control, Honeywell (H) offers an internet gateway + App though which you can control your heating remotely.
The gateway can be connected wireless to the thermostat. I cannot find how this works (blue tooth, wifi, else) but it doesn't use my local Wifi that's for sure.
To use the App, I need to create an account on the H server and connect it to the mac address of the internet gateway.
=>This means that all my data goes through the H servers, and their privacy policy is pretty unreadable. It does contain many combinations of the words "3rd party" and "sharing".

Such a deal is not acceptable, luckily I'm a programmer
--------------------

My plan
---------
-install a Rasperry PI,
-Write some backend code (dotnet core) interfacing with the thermostat, to set the temp.
-Next to that, I can run a web server on the Pi,
-here I can develop my own frontend, to display and control a growing list of home automation devices

Great, however there is a problem: I cannot find any info on how to interface with the H thermostat. I heard that H's frequencies and protocols are proprietary.

Questions
---
Can I use your gateway to get such a setup? I'd prefer to keep using the H thermostat modulation, as developing my own thermostat code looks like a large project.

The only setup I can think of is
-replace my H boiler interface with your OpenTherm gateway
-connect the H thermostat to your gateway
-My code code then talks to your gateway (serial port?)
-Your gateway might be able to wireless set the temp on H thermostat (is it able to do this?)
-Then we can leave it to H thermostat to instruct your gateway to tell my boiler to reach the desired temp smoothly

Is this possible like this?
.. or do I need to create my own thermostat (including temp sensor? on a board like Arduino?)
.. is there another way to do this?

My main goal is to have remote heating control and to get started on a basic platform for home automation, while avoiding data exposure.
I am a software developer but never did any embedded programming.

Thanks for any advice
Arjan

[hvxl]

Normally an RF interface wouldn't be inside the metal enclosure of a boiler, as that would attenuate the RF signal quite a lot. The general configuration of an opentherm boiler with an RF thermostat is:

• Boiler --OT--> RF interface --RF--> thermostat.

To use the OTGW, you would connect it between the boiler and the RF interface. It doesn't replace any of the existing equipment.

However, experiences I have heard from other people are that the data exchanged on the RF interface is very limited. Many times the interface reports a fixed room temperature and room setpoint on the Opentherm interface, presumably because it doesn't receive this information via RF. I have not heard of an RF thermostat that supports changing the room setpoint via Opentherm.

There are wired thermostats that should allow you to do what you described.

[arjan_m]

hmm ... I checked again (on outside) but I don't see any wires going into the boiler ... so I wonder where this RF interface is then

The schematics of the boiler show two connection points, and wires should be plugged in there to feed it OT commands.

Are you saying that the thermostat might not even communicate the room temp using RF to the RF interface?
But the thermostat reports a room temp on display, so I assume it has a temp sensor.
But boiler might use the temp from another sensor of RF interface? ...sounds strange as in the kitchen it is definitely 2 degrees colder than in my room.

Also, when placing OTGW between RF interface and boiler, what would be it's function?
After all: In a working setup, the RF already speaks OT to the boiler.

It seems all very vague, this is prob due to the closed engineering, I guess I'm looking for an open system.
Arjan

[hvxl]

The room temperature is just a parameter the thermostat is using as an input to its control algorithm for the boiler. Another parameter is the room setpoint. The output of the control algorithm is the desired water temperature. So yes, obviously the thermostat will have a temperature sensor. But the boiler doesn't need to know the room temperature nor the room setpoint. Not sending unnecessary information over the RF link will extend the thermostat's battery life.

So I'm not saying the boiler gets the air temperature from somewhere else. It doesn't get it at all. Because it only needs to be informed of a desired water temperature. It has its own sensor (or two) to measure the actually produced water temperature. It modulates the flame based on those two values.

If the setup works as desired, then you don't need the OTGW. But you indicated that you wanted a way to externally influence the system. That's the function of the OTGW: It can modify or inject opentherm messages.

[arjan_m]

makes sense about the room temp, the boiler doesn't need to know it .. lol.

So the OTGW can inject OT messages, or or modify OT messages from the thermostat.

Does this mean I can write code to
-prevent the thermostat from telling the boiler to heat
-make the boiler heat when the thermo doesn't see the need?

That would do the trick for me. Then i can
-correct remotely when I forgot to turn thermo down.
-turn up the boiler provisionally 30 min before I get home...

When I'm home, i just leave temp regulation to the developed code of the thermo

I assume I need to feed these messages into the OTGW through a serial link? I prob can use a raspberry for that ..
Where can I find the spec of the messages I need to inject?
Sounds interesting, thanks
Arjan

[hvxl]

I made a web site to provide lots of information about the OTGW so I wouldn't have to answer everyone individually. Maybe you should read it some time. You may particularly be interested in the CS and CH serial commands.

[arjan_m]

Well .. I did read your site upfront but just didn't get it ..realize that I'm not familiar with the particular context at all.

Your site is full of tech specs but the context is assumed known and the functional setup should be distilled from text.
Realize these are a big steps for someone unfamiliar to the field.

What helps people like me is a higher level functional design graphic. I attached an first draft of such a diagram.
I can't attach the opendraw document for you to expand or correct errors. If you want it, let me know a way to get it to you.
Thanks for you patience
A