Gas boiler control

Hello everyone, i am new to this automated world and I’m starting my first project but I’m relatively lost…
Basically, what i want to do is use a dry relay to control my gas boiler and thus have a control over my house heating.
I want to use Zigbee as a connection between devices and i understand i also need a zigbee thermometer on the wall.
That’s all I know, i don’t know where to start… Can this be done with a sonoff wifi relay? My gas boiler is new, it was just installed, but i lack any kind of thermostat installation.

Any help would be appreciated.

On/off bang-bang control is pretty crude. If your gas boiler is new then it will very probably have an OpenTherm interface on it. Which would enable you to connect an OpenTherm thermostat which is rather more sophisticated. (And probably much more energy efficient too). And then you can put an OpenTherm gateway on the bus between the thermostat and the boiler, which would allow you to read boiler status and thermostat temperatures on one hand, and issue override commands to either.


I have been checking and my boiler has an EBUS protocol, I understand this is different from open therm.
Does it make it any more difficult?

But the problem is that if I install a thermostat, then it will have to be placed inside the room where the boiler is (I don’t have any wiring through the walls for boiler control), right?
I wanted to install everything using a raspberry pi


You probably have a Vailliant gas boiler ? You van buy a opentherm module.
As Andrew says, it’s a lot better to control it with Opentherm than use the old ON/OFF control.

And with the current gas prices efficiency will save a lot of money.

It’s a Hermann MicraPlus heater, a sub-brand from Saunier Duval.
What do I exactly need to install that module? How do I know if it’s possible

For a lot of brands you can buy a Opentherm module that you need to fit inside the gas heater.
Google for your gas heater exact type combine with opentherm and hopefully you get a hit.

It as a guess that u had a ‘Valliant’ gas heater as I know they also use E-Bus. But opentherm modules are brand specified.

There’s also an EBus binding and gateway you can buy (3rd party ie not from the vendor).
Search the forum for details.

Then again, sounds like you should properly revisit and understand your ‘project’ first.
A boiler without a thermostat ? Unlikely. Most also have dry inputs.

And when you’re new to automation, heating isn’t the first you should take on. It’s way more complex than it seems at first glance.

Yeah you are eight I should understand my project first. But the thing is I don’t even know where to start so that’s why I’m here.
My boiler has thermostat inputs but it’s not installed. I just bought this house and they didn’t care to install a controlled.
As for the complexity… I find this automation way more useful than trying to control Light switches in my house. I wouldn’t go through all this just to control a light switch.

El El vie, 9 sept 2022 a las 9:31, Markus Storm via openHAB Community <> escribió:

Helklo Vic,
I started with OH mainly because controlling of heating.
I have a very old Vailant gas heater but it regulates heating already by outside temp and is I guess one of the first calorific value heaters.

I let the heater do what it wants as it does a good job in general.
I have installed z-wave thermostats on the radiators in most of the rooms, so I am able to have heating plans for every single room depending on presence.

In my opinion this is a much easier solution as to regulate the heater directly.
As Markus stated, that would be a much more complex approach.

Excuse me but what is the point of turning radiators on and off in each room exclusively? The most sustainable way of saving on gas is regulating the gas heater itself, isn’t it? That’s what most thermostats do: they control the main source directly. Radiators are secondary.

El El vie, 9 sept 2022 a las 11:11, Christian via openHAB Community <> escribió:

No, gas heaters are heating the water until it reaches a max. temp where the heater shuts off automatically.
As more the valves on the radiators are closed as more hot water will return to the heater which causes the heater to shut off.

Regulating the heater itself would mean that some rooms will not get warm enough and some will be overheated.

The placed where I used to live last year was a newly built building and if I wanted the heating to be working, I had to turn on the heater… If I keep the heater on 24/7 during the winter and there’s no temperature control in any room (no thermostat), the heater will keep the water at say, 70 degrees… but it will do that constantly… that’s a waste of money.
Thermostats turn heaters on and off, not radiators. I really don’t get your point.
This wasn’t the point of this thread anyway… so far I haven’t got much help really

El El vie, 9 sept 2022 a las 12:23, Christian via openHAB Community <> escribió:

Okay, so you are looking just for a solution to control your heater where I cannot help you.

Just for completeness:
Modern heaters regulating heat depending on outside temp.
If it is not so cold the water has e.g. 35°C, if it is colder up to about 60°C are possible.
The valves on the radiators take care to have the wished temp in each room.

Why can’t a thermostat control a radiator?

If you just want your heater on at certain time then use a time clock.

You have technology and specified technology and are lost.

What do you want to do?

Maybe your question should be

I have a boiler 27525hjknfns link with EBUS protocol and want to control it using openHAB where should I start.

I want it so when I am not home and it is cold outside or predicted to be cold it will turn on automatically to RR deg because I have pets I don’t want to freeze. When I am home I want it set to TT deg in the day and EE deg at night because I like it like that. I also want a holiday mode so when there are no animals in the dwelling it will heat only to EE deg so the pipes don’t freeze. I would like to be able to override the settings with my voice when I want to.

Yeah it can all be done using openHAB


Yeah exactly, I probably started off on the wrong foot.

Basically what I have is a Hermann Micraplus 25 with EBUS protocol and I would like some help on how to control it with OpenHAN and a raspberry Pi, and I don’t know where to start or what componentes I need.
I have been checking dry relays but I don’t know what kind of relay I need, if it need to be a sonoff wifi relay, etc.
I just don’t know where to start!


El El vie, 9 sept 2022 a las 13:49, James Bowler via openHAB Community <> escribió:

Sure we can help

It depends on what control you want. If you just want to control when it is running you may be able to use the dry contacts. It will act like an electronic switch that you can control instead of the mechanical one.

I would use the EBUS as you can then control everything.

Okay so if I want to use the EBUS what kind of dry contact do you think I need? Also, those dry contacts require some power? Do I need extra wires for that?

El El vie, 9 sept 2022 a las 14:07, James Bowler via openHAB Community <> escribió:

You will need something to connect to EBUS like

Or build your own.

Ok this is pointless. You are showing me an adapter for my Raspberry that’s not even available to buy. Also, I don’t know what kind of relay I need to connect to my heater…
On the page you provided it says the heater needs to connect to the EBUS adapter that I have to buy an attach to my raspberry… I just don’t want to place the raspberry in the room where the heater is. It is somewhere else
This is exhausting. Thanks anyway.

Read the EBUS binding info. It gives a lot of information.