Wireless Link to Baxi Opentherm Combi-boiler (UK)
Hi,
I'm about to have a new Baxi (836) combi-boiler fitted. Due to the proposed location I won't be able to use any existing thermostat wiring and so I'm planning to use a wireless connection between the boiler and the smart thermostat. The boiler provides Openterm connectivity which, after a bit of research to understand its benefits, I certainly want to use.
I'm interested in a system that will allow multi-room control so the two systems that I'm looking at are the Honeywell Evohome & the Tado. I'm favouring the Tado but growing concerned if it can actually provide full Opentherm support or simple On - Off switching.
In particular I've seen this post which seems to imply that the Tado system does not support Opentherm:
Open Term vs Relay Connection to Boiler — tado° Community
To add to my confusion there seems to be a great deal of discussion around the wireless unit / expansion unit. Are they actually one and the same unit?
There also seem to be two versions of the wireless unit: with & without hot water control. I'm assuming that, for a combi-boiler I should be looking at the one without hot water control?
Thanks in advance for any help in understanding if, indeed, it is possible to fully setup Opentherm wirelessly on a UK combi-boiler with a Tado smart controller.
Comments
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To try and clarify things I would be pleased if you could elaborate on your previous comment within this post Open Term vs Relay Connection to Boiler — tado° Community that:
"It’s a technical limitation of Tado (and Nest). They will only do ebus OR relay switching."
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@JohnWH did you end up using Tado and figure out the situation with OpenTherm on this boiler?
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Yes, I did finally get it sorted with Tado wirelessly controlling my Baxi 836 boiler via Opentherm 😀
Unfortunately (& for reasons only known by Tado) their current UK wireless systems don’t provide the necessary digital control connectivity – only simple on/off relay control.
I initially ‘fell foul’ of this when I purchased a UK-supplied Wireless Starter Kit and discovered the complete lack of the necessary {A - +} digital terminals.
After checking with Tado’s technical support I was advised to buy the standard ‘wired’ UK thermostat kit. Alongside this I managed to get one of Tado’s Extension Kits which does have both digital plus switching terminals. Apparently Tado no longer supply these Extension Kits in the UK but fortunately they seem to be available occasionally on eBay.
My setup has the Extension Kit wired directly to the boiler (power and the pair of Opentherm connections). The Smart Thermostat is then located remotely & totally wirelessly – I use it to monitor & control the lounge temperature.
When I first installed the Extension Kit onto the boiler, the system failed to control the boiler. Tado’s technical team resolved everything by forcing a firmware update to the Extension Kit – something which apparently won’t happen automatically until a forced update from them.
Wired as such the Opentherm system completely over-rides the two temperature setting controls on the front of the Baxi boiler. Using the Tado App it is also possible to select the desired temperature of the hot water supply very simply. Additionally, the central heating system modulates as required including lowering the temperature of the circulating water to the radiators – I have around 12 of the Tado valves.
Initially the full flow central heating temperature was set at 80 degrees C which is too high for achieving best performance from a condensing boiler. Upon request Tado’s technical team set the maximum to 55 degrees C.
I hope this all makes sense but, should you require clarification of any points, please don’t hesitate to ask.
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What a mess!
There is an extension kit available in the tado store but it doesn't state if this is the UK or EU version:
https://uk.shop.tado.com/products/wireless-receiver
There's also the option to buy the EU wireless starter kit, though prices are much higher:
https://uk.shop.tado.com/products/wireless-smart-thermostat-starter-kit-v3-eu-version
The Wireless Starter Kit product page is very misleading as it states "OpenTherm Certified"
https://www.tado.com/gb-en/wireless-smart-thermostat-specifications-overview
Looks like I'll be returning my Wireless Starter Kit back to Amazon.0 -
Totally agree!
It seems that Tado want to force their UK customers to continue to use legacy on/off relay switching. Assuming a boiler is suitably enabled the use of modern digital control such as Opentherm is an absolute ‘no brainer’.
Even more frustrating is the Smart Controller supplied in the UK Wireless Starter Kit is very much ‘cut back’ from the ‘normal’ wired one in that it doesn’t have any terminals which could be directly wired to the boiler inputs. Hence why I was advised by Tado’s technical that I purchase the Wired Starter Kit which will allow the controller to be wired directly to the boiler and does include the necessary digital terminals. Alongside one of their Tado Extension Kits this does provide the wireless Opentherm control capabilities that I require.
I’m not sure what the exact differences are between the UK & EU Wireless Starter Kits. Based upon some previous details from @jelockwood here ( Open Term vs Relay Connection to Boiler — tado° Community ) I suspect the EU variant might offer Opentherm control but not simple relay switching whereas the UK clearly offers only on/off switching.
The Extension Kit does have both types of control – both digital plus relay on/off switching although I suspect it’s only possible to use one type at a time. However, I really don’t see this as a problem given the advanced nature of the Opentherm control.
My Extension Kit is labelled DBU01-TA-04, FX 1910 and it’s currently running firmware v81.1
Physically the Extension Kit is slightly different to the UK Wireless Receiver in that it is a little bit ‘taller’ (dimensions 15cm (W) x 10cm (H)) and it only has a single circular button in the top of its casing.
Hope this helps?
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Here is a picture of the rear of my Tado Extension Box showing the relay & digital connection options:
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Thanks for the information, really helpful.
I'm returning the wireless starter kit to Amazon UK and considering ordering the EU version from an Amazon EU country.
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To add some clarity:
Our old Extension Kit (as pictured above by @JohnWH ) had 2 relays (heating + water) plus a digital bus. Serial numbers starting with BU.
We received a lot of feedback from the UK that professional installers struggled with primarily the setup of the Extension Kit. Our numbers showed that, in the UK, the digital bus control for Opentherm/eBus and so on was hardly ever used.
In continental Europe there are roughly zero setups requiring 2 relays, digital adoption is way higher and we didn't get the professional installer feedback we got from the UK. The demands of the markets are thus very different.
The result is that we replaced the old Extension Kit (BU....) with two different models:
- Wireless Receiver with a serial number starting with BP. UK only (maybe Ireland, not sure). Not available in continental Europe. This device has 2 relays and no digital bus. Easy setup for installers.
- Wireless Receiver with a serial number starting with BR. Continental Europe only. Not available in the UK. This device has 1 relay (heating only, no relay for hot water) and a digital bus.
The devices are optically similar, with the exception of the number of LEDs. The EU one has no hot water LED. If you order one you always get the same one; the one meant for your country. There's no unclarity there. If you want the other one, you'd have to go out of your way to order from abroad. Or maybe find an old Extension Kit.
The wired Smart Thermostat offered in the UK does offer digital bus compatibility. This device is identical to the ones we sell in the EU.
Edit:
I walked passed a little test setup in the office. With a UK version on the left, and an EU version on the right.
In both cases the heating is set to off, so the heating LED is off too. You'll notice on the left there is a water tap symbol as well. Additionally, the UK version has two test buttons; one for heat, one for water. The EU version has neither.
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can i just say, I have one of the old Extension Kits, and I have it wired into my Baxi 800 series boiler via OpenTherm, and it's been great. it controls the burner and radiator water temp, plus I can control the Hot Water temp via schedules, so during the day when we just need water for washing up etc, I have it set to 47c and laster on at Night when we have our showers it set to 50c, even this 3 dec change does make a difference to my gas usage.
I saw a major difference to my GAS Bill after swapping to OpenTherm, the GAS Engineer only setup the link to my boiler using the relay, when I purchase the new boiler, but after reading up on OpenTherm I decided to do the swap myself, it been on 2 years now, and the GAS Engineer even wanted to see how it was done, when he came to service the boiler, so he could advise his other customers that use Tado.
@tado If my Extension Kit ever fails I hope you could provide a Digital Link version to the UK?
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Like you I've seen a huge reduction in my gas usage following the installation of a new Baxi 836 boiler which is OpenTherm controlled (modulated) via a Tado Extension kit and equipping all the radiators (except bypass ones) with Tado smart thermostatic valves. In fact my gas consumption is now running at approximately 40% of what the previous, simple on/off switched boiler was using - even in the depths of a UK winter 😀
It does seem bizarre that plumbers are slow to recognise the benefits of digital control of boilers - particularly as the traditional wiring setups can involve several connections (sometimes powered) rather than a pair of very low voltage digital wires - which are also polarity independent.
The only thing that I would like to see is the ability to set the maximum flow temperature of the central heating system (I am aware this has been added by another user as a 'wish-list' item). Fortunately Tado's excellent support folks very quickly set mine to the requested 55 Deg C (from the default 80 Deg C).
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@andyblac
Yes I submitted a request to Tado’s support team using the online form. I was extremely impressed when less than 10 minutes later I received an email to say they had changed it.
As you are probably aware condensing boilers are most efficient below the dew point of water which is around 55 Deg. When quoting boiler efficiency manufacturers always use figures in the condensing range. For the Baxi 800 range the efficiency is quoted at around 93% when in the condensing mode.1 -
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not sure about the Viessmann, but on the Baxi, it shows the flow rate temperature on the boiler display, so if you have cold room (it has to be a cold room or set the target room temp way above the current temp, else OpenTherm will only set a Flow rate Temperature what it thinks is efficient) turn on a TRV as if to heat the room, go look at your boiler display if it has one, and watch the temperature rise, when it stops rising that should be the MAX Flow rate Temperature.
But if you mean what your boiler most efficient flow rate is, sorry I can't hope John can.
Hope this helps.
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@GrayDav4276
Like @andyblac I'm not familiar with the Viessmann boiler range.
As Andy states the Baxi boiler shows the flow rate temperature to the radiators. This is the temperature of the outlet flow from the boiler, the incoming temperature is lower once it's passed through the radiators. The lower the incoming water temperature is the more efficient a self-condensing boiler becomes.
Baxi combi-boilers have two manual 'dial' controls - one for setting the temperature of the radiator flow, the other for setting the temperature of the hot water supply. When set up with OpenTherm control (from the Extension Kit) both of these controls become 'redundant' and turning them simply results in the temperature display flashing for a few seconds to indicate the corresponding set temperature.
For my system the maximum output temperature to the radiators is now 55 Deg C (to be honest 80 Deg C also made the radiators dangerously hot to touch!). Once the rooms heat up and there is less demand on the boiler it then automatically lowers the circulating water temperature.
Hope this helps - makes sense?1 -
since I have tweaked my MFT to 55c, my main rad SRV is still throttling the rad like it was on 80c, ie the boiler is at max flow rate temp 55c, and the icon in Tado˚ room has 3 wavy lines, but when it gets to 9:30am (that was at the point the room was almost at target temp) I hear the SRV motor adjust the valve and it reduce's water flow to the rad (if that makes sense), and that then stops the room from heating up, as the target temp has not been reached. Will it just take a few days for the SRV relearn or should I reset the SRV? would that help ?
Andy.
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Given the reduction in the maximum temperature of the radiators the room will now take longer to reach the set temperature and I guess your Tado system will now need to 're-learn' the characteristics of the area. I haven't noticed similar behaviour in my main area but I'm using the smart thermostat as a wireless temperature controller to provide more accurate regulation than provided by the SRV's which, due to their proximity to the warm radiators, can be several degrees 'out'.
I don't think resetting the SRV will be necessary since the calibration that runs when first mounted on the actual valve is only to measure the distance of travel of the control pin. This will remain the same and, once measured, the SRV will then be able to make the necessary small step changes required to regulate the flow.
John
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@JohnWH,
Thanks for that, I too have had my Smart Thermostat converted in to a Wireless Temperature Sensor by Tado (it no longer shows as a Zone Controller). I guess it is just going to take a while for the SRV to relearn the new MFRT.
Andy.
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When you reconfigured your Tado as part of the installation, did you specify the Opentherm protocol (D1) or the BS-BUS protocol (D62)? Did you enable hot water control?
Ever since installing my Tado on the Baxi 836 I'm getting regular error 128 ("Flame loss") error. When I stop all heating/hot water, and push the reset button, it goes back to normal.
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Hello, I was looking for help on how you wire the extension kit (BU33226144272) to our Baxi 836 boiler.
Our plumber has concerns that the 240v 2 core cable will blow the low voltage board. Also what is inside doesn't match up to Tado's install guide. Thanks0 -
Your plumber doesn’t seem to understand what a low voltage connection is. Sounds like he thinks a switched live connection from Tado should go to the digital connections in your boiler, which would blow the circuit board. I don’t know your specific boiler model but the low voltage connections on the Tado extension kit are on the right, marked + and - . You’ll need to look in your boiler manual to find out where the digital connections are on the circuit board, assuming it has them. Then you can run pretty much any two core cable between the digital connections. You’ll also need a separate power source for the extension kit.0
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I've attached below the relevant details taken from the Baxi Installation & Service manual which show the low voltage OpenTherm connections. These are the ones which connect to the Tado Extension kit corresponding low voltage connections which are marked + and -.
As explained by @johnnyp78 these are low voltage connections and must not be confused with switched live connections.
OpenTherm is not polarity sensitive.
Hope this helps / makes sense?
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Hello.
You guys all understand a lot more about how eBus works with boilers. I have a Worcester Greenstar 27 Ri boiler which is controlled from a Greenstar Wiring centre upstairs. I have read that Tado is compatible with the type of eBus this system uses but I know I need to buy the EU version of the wireless stat or wired with extension, but I don't know how I would wire it up. I had a heating engineer come and have a look who had no idea either and wanted to swap the whole thing out with relay controls.
If any of you are willing to help me remotely, even to see if it's likely to work that would be great. Obviously happy to pay for your services.
Thanks,Simon
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Unfortunately I don't have first hand knowledge of the Worcester Greenstar 27 Ri boiler but from what I can see online the electrical connections are covered in section 5.6 (page 28) of the INSTALLATION, COMMISSIONING AND SERVICING INSTRUCTIONS - see below
Assuming the eBus is compatible with Tado OpenTherm (hopefully Tado's technical support team can verify this) then I would assume the connections go to the two EMS terminals (#6 in the diagram above).
OpenTherm connections are not polarity dependant so I assume that EMS aren't either.Clearly all low voltage control connections must only be made to the 24V connectors and the mains supply power made by a competent electrician.
For some reason plumbers do seem to love the complexity of Y, S & W plan wiring for boilers using relay switching instead of a pair of low voltage digital control wires.
I hope this helps.
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Thank you for your reply. I have read Tado is compatible with this t type of eBus.The EMS bus connection from the boiler is already connected to a Greenstar Wiring Centre next to the hot water cylinder upstairs. At this point I get lost :). Thanks, Simon.
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@simo_newm
Hi Simon,
Yes, I can see the twisted pair (it looks like white & green) wires at the far right hand of the picture which are connected to the BUS terminals. I suspect that these would need to be removed and the digital (low voltage) control wires from a Tado Extension kit connected instead to the BUS terminals.
Hopefully there's someone on this forum with a similar setup who can confirm that this is correct.0 -
@JohnWH. Thats true, that pair of wires does handle E-bus communications, in this instance between the Greenstar wiring centre and the boiler. Almost all controls are connected to the Greenstar wiring centre, with one exception from what I can see in the other photos- the boiler's programmer! That seems to also run on another E-bus ribbon hidden behind it.0
