Home Automation Domotica Forum Europe, Bwired Forum

Due to an error on a (not specified) website, I have mistankenly assumed that the Atag BrainQ thermostat (and therefore also the Q38 boiler) uses the OpenTherm protocol. The usage of the OpenTherm protocol were the main reason to select this boiler above the Nefit Excellent boiler.

Does anyone have any experience with these proprietary protocols? It can hardly be rocket science, but once I have made my choice it's hard to go back if reverse-enginering the protocol turns out to be rather difficult.

Does anybody have any other solutions? I only want to change the setpoint and read the room temperature.

(I consider relays manipulating the buttons of an existing thermostat <b>not</b> to be a solution, not even a bad one. It's a (bad) work-around at most.)

In most houses only one zone heating (livingroom) is common – the thermostat will control directly the boiler either in on/off or modulation - In case of modulation mode will need a special thermostat – mostly based on the Opentherm protocol. Although some boiler manufacturers using their own protol and protecting their business. This is a two way protocol – the boiler will transmit information about activity, hot water, pressure low ,etc. The thermostat will provide the boiler with heating instructions –depending on actual and desired temperature.

Even if you install the Opentherm interface (the Elektuur article) it will not control the temperature – it is more a sniffer – you may use the information in the home control system – but you will not be able to manipulate the set points …. Of course it is possible but then you have to take over the thermostat function and it should be done by the home controller – so getting the reading of the temperature sensor (installed in the living room) and software to produce the right heating instruction to the boiler – this is not an easy task.

Back to multi-zone heating – first of all the heating system will work in a different way – the boiler control will be based on regulating the circulated warm-water temperature. All radiators should be equipped with a thermostat valve and one bypass valve should be installed – preventing damage to the circulation pump in case all valves are closed. It is common to have an outside temperature sensor what will control the temperature of the circulating warm water. (some boiler will support this feature and offer the outside sensor)
So no need for a thermostat in the living – although you may have a thermostat what will switch of the boiler during the nightly hours …. But be aware this kind of heating will require more energy – all the time hot water is running thru the backbone and the circulation pump is on.

In case an owner wants multi-zone mostly it will be done for only two zones – the living and either the study (office) or master bedroom. Also in case there is a (gas)/open fireplace in the living it may be a nice feature – providing heat in the rest of the house.

For the situation of a fireplace Honeywell has an option based on their Chronotherm thermostat family – you may switch temporarily from direct boiler-control to warm-water temperature control. This option will fit behind the wall mounted Chronotherm

An in between solution is implementing the manual controlled thermostat knob – controlling the set-points by a daily schedule – this may work special for rooms with a predicted usage like master bedrooms or even the bathroom.

In a large house – more zones will be required …. Or you are hooked on domotica and want to control everything in the house ….. so what are the options – have a look at www.honeywell.nl they are a major producer on control heating system

In case of a newly installation you may plan the topology of the warm-water distribution in such a way that you will have a central distribution point (or more points) where you can install motorized valves in the lines. This technique is common for the floor-heat systems where the tubes will run from a central point at each floor level
At least you will need in each zone a thermostat controlling the valve. In existing houses this is likely not possible and you should use motorized valves on the radiators. There are two kind of radiator valve – one with an integral temperature sensor, storing set-point and time schedules – either manual set of remote controlled by RF. The other one is without any control – only a motor opening or closing the valve on a remote command. Both types will require batteries to operate.

Again take a look at the Honeywell site – the have several systems based on the intelligent radiator valve – all valves are equipped with a temperature sensor – for types:

HR20 – manual – two set-points –schedule € 50 – Conrad is selling them !!
HR40 – manual – two set-points –schedule €89 (don’t know the difference with HR20)
HR50 – RF – controlled by Hometronics €105
HR80 – RF – controlled by CM67Z € 131

Those thermostats has different adapters – so they will fit on most valves producers on the market – no need to replace the whole valve.

Option 1: HR80 / CM67Z

The HR80 will require the CM67Z controller for the controlling of setpoints and time scheduling only two zones for each CM67Z (€ 174) Multi CM67Z are possible. This system has a nice feature it has an additional boiler relais – so in case no thermostat will require heating – the boiler will be switch off and saving energy. This is de HC60NG device € 148 …. They will offer you a bundle package …..

Option 2: HR50 / Hometronics

In case you want to have all your rooms equipped with an individual control based on the HR50 thermostat valves (living,kitchen,hall,bathroom,study,bedrooms 3x .. total 8 zones) the solution is may be the Honeywell Hometronics system with a capacity of 10 zones. It will have a different price tag – also you will get additional home control functions ……it is an integral part the Honeywell total home automation solution. … see Internet for more information and pricing.

Option 3: Conrad (for other people ….)

Even Conrad has a family of valves and thermostat controllers – their thermostat valves are only motorized and requires a wall thermostat FHT8B …. A combined package of one valve and a wall thermostat is € 80 (requires additional adapter) … They have also a master controller FHZ1000 controlling all installed wall thermostat € 80 . There is also a computer controller based on a USB connection € 129 (may be hacking the software ?) …. They offer packages also.
So I will not start a discussion on the quality – at least they are using a different prices level – I may mention the ugly Conrad logo on the wall thermostat – it looks like they subsidize the thermostat in exchange of advertising … or just spray-paint the thermostat housing

All options - systems are stand-alone and closed – no integration with external equipment is possible – information on the used protocols is not available and will be protected, even hacking information on Internet is not available.

In case you want to do reverse engineering go ahead – but you will need hands-on – even if you have the protocols you have to spend effort on producing the RF controller or may be writing thermostat control software. All my support !

Alternative solutions …. All the Honeywell thermostats has three buttons and one rotating knob …..Even if you don’t like the classic trick ----- but you can bypass them …

There is one other solution you may consider ….. a very low cost ….. get some resistors with power ratings likes 2-3 watt – so fit those resistors together with a trafo – controlled by X10 inside normal thermostat valves – touching the sensor – do some testing what kind of current is required to fool the set-point in the right way …… Please don’t laugh this technique was seriously offer by the early generation X10 controlled thermostat …. And why not retro-fit ??

Good luck and let us know !

PS: I’m working on a domotica publication – the content above in some other format (less product specific information) should be part of it … additional information will be added so a total view on heating your home and what is possible … including some tips on integration with home control for the freaks …… so feedback is welcome

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Henk</i><br />
In most houses only one zone heating (livingroom) is common – the thermostat will control directly the boiler either in on/off or modulation - In case of modulation mode will need a special thermostat – mostly based on the Opentherm protocol. Although some boiler manufacturers using their own protol and protecting their business. This is a two way protocol – the boiler will transmit information about activity, hot water, pressure low ,etc. The thermostat will provide the boiler with heating instructions –depending on actual and desired temperature.<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">
After my extensive research, I think I've got a pretty good overview of what's available on the market. I will definetly avoid On/off-systems , even though most zoning systems (like CM67Z) use it to control the boiler. The efficiency is just too low in my opinion.
I'm also trying to avoid the proprietary protocols as Atag and Nefit use. Not because I'm planning to tap into the OpenTherm bus (don't have such plans), but because the changes of an externally controllable OpenTherm thermostat hitting the market is much bigger than an externally controllable Atag procol thermostat coming out. So my decision for OpenTherm is based upon future expansion, not for the 'Open' protocol, which isn't open at all, as in Open Source software.
<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Henk</i><br />
Even if you install the Opentherm interface (the Elektuur article) it will not control the temperature – it is more a sniffer – you may use the information in the home control system – but you will not be able to manipulate the set points …. Of course it is possible but then you have to take over the thermostat function and it should be done by the home controller – so getting the reading of the temperature sensor (installed in the living room) and software to produce the right heating instruction to the boiler – this is not an easy task.<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">
I fully agree with you here: Building your own modulating thermostat is close to madness because the algorythms required are very complicated and largely underestimated. The Elektor OpenTherm device is not much more than a toy that's listening in on the bus. Talking on the bus is useless in my context because I don't want to control the boiler; I want to control the thermostat. Even if there are OpenTherm commands to set the thermostat's setpoint and to read it's temperature, I doubt if there are any manufacturers who have implemented them. These standards usually contain subsets of 'required' and 'recommended' functionality.
<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Henk</i><br />
Back to multi-zone heating – first of all the heating system will work in a different way – the boiler control will be based on regulating the circulated warm-water temperature. All radiators should be equipped with a thermostat valve and one bypass valve should be installed – preventing damage to the circulation pump in case all valves are closed. It is common to have an outside temperature sensor what will control the temperature of the circulating warm water. (some boiler will support this feature and offer the outside sensor)
So no need for a thermostat in the living – although you may have a thermostat what will switch of the boiler during the nightly hours …. But be aware this kind of heating will require more energy – all the time hot water is running thru the backbone and the circulation pump is on.<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">
Thank you for clearing that up! I was already suspecting this, but I couldn't imagine it was working in this (energy wasting) way because it's a bit contradictive to using HR boilers.
<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Henk</i><br />
In case an owner wants multi-zone mostly it will be done for only two zones – the living and either the study (office) or master bedroom. Also in case there is a (gas)/open fireplace in the living it may be a nice feature – providing heat in the rest of the house.
.... snip ...<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">
I am definetly looking at the Honeywell hometronics system. If I could integrate it with my X-10 system it would be perfect. I've also been looking at the HR80 knobs; They're real gems. Perhaps these two could work together.

What I most definetly don't want is my boiler to burn gas when my room thermostat is set to 15 degrees, just to check if an of my HR80's are requesting heat. This information should be available for the boiler, instead of the boiler figuring it out itself by comparing incoming and exiting water temperatures an thereby burning gas.

The way I see it, there are 2 situations:
1. I am heating my living room (and possibly some other room(s))
In this scenario the room thermostat is controlling the temperature in my livingroom according to it's temperature. The HR80's in the livingroom should either be set to 'fully open' so they won't counteract the roomthermostat, or better, set to a temperature slightly about the room thermostat's setting to balance the radiators within the room. The radiators in the other rooms will just piggy-bag along with the heat the livingroom requires. Making sure the radiators in the other rooms receive enough heat is just a matter over overdimensioning them (more than those in the living room).
2. I am heating one or more rooms, but not the living room
In this scenario the boiler must be turned on if any of the HR80 knob's is requesting heat. The difference in temperature of incoming and outgoing water of the boiler should control the boiler's modulation percentage. If no knob is requesting heat, the boiler should be off.

It would be perfect if the HR80's automatically follow the setting of the room thermostat and that the system automatically switches to scenario 2 of the room thermostat is set to 15 degrees while one (or more) HR80 is requesting heat through it's radio.

Of course I also want to be able to request each HR80's room temperature and alter each HR80's setpoint remotely.

The way it looks now, I'm going to control my HR80 knobs by a homebrew tranceiver connected to a microcontroller. A Remeha Quinta with Celcia 20 OpenTherm room thermostat and a Remeha Gateway will be connected too. I hope I can find some information about the protocol this gateway uses...