Digital Tado for a Vaillant Ecotec Plus 837 combi
Answers
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Firstly if you connect 230v wires to a low voltage connection you’ll fry the circuit board at the very least, so avoid doing that.
Secondly, check that Tado supports modulation on your boiler. Some vaillants use an incompatible version of ebus.
If you can use a digital connection it’s very simple, the + and - connections on the thermostat go to the digital connections on the boiler.
I agree the app should be encouraging modulating connections. It might be in your case that it isn’t supported, or that Tado doesn’t do it in the uk because it thinks no one uses opentherm here.0 -
I have the Vaillant Ecotec plus 937 which is exactly the same boiler as the 837 but with an added 20ltre hot water storage tank. It works perfectly with a digital connection. I didn't have to open my boiler as I was replacing a Vaillant digital wireless receiver that was mounted external to the boiler.
If you are connected to the 230Volt relay circuit it will involve taking the cover off the boiler to move the wires onto the ebus terminals.
You should get a Gas Safe engineer to do this part of the setup
https://www.manualslib.com/manual/1483186/Tado-Smart-Thermostat.html?page=17#manual
See pages 17-19 for configuring the thermostat to use ebus for Vaillant.0 -
Johnny and Kissarmy, I would like to thank you both for taking the time to reply and the advice is incredibly helpful. I had already checked with Tado that my Vaillant was supported before buying the Tado, so was surprised to find that the instructions did not cover such an important aspect. I am having an annual service on Friday so I hope that my gas service engineer will agree to move the boiler wires to ebus when he comes. I assume that doing this will drop the voltage to below 40V at the thermostat. I have a multimeter and will check the voltage before moving the wires. Tado really needs to get their instructions updated, there is a huge market for getting boilers and controllers set up properly.1
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Once it’s done, you can check the set up using the Tado pro app. If it’s an Opentherm connection you can also set the max flow temperature through it (and possibly ebus but not sure).0
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Oddly, the Vaillant technical department has messaged me to say that Ebus on Vaillant products only works with their own controllers, which contradicts the advice from Tado! Surely Vaillant must be incorrect.
Nevertheless I need to find assured instructions before moving the wires across.0 -
Bear in mind that Vaillant would like you to buy their equipment rather than use third party controls, which is why Tado has had to reverse engineer the ebus.0
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Yes, although it makes me less inclined to choose their equipment in future. Buying their controller would lock me into their boilers in future, and in any case their controllers have been unavailable for purchase.0
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They aren't backing down! "Vaillant boilers aren't opentherm compatible. eBUS is like Vaillant's version of opentherm, but it only works with Vaillant controls."0
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@Stephen_Hall If you use the professional installer instructions (https://cdn.brandfolder.io/607DGEMS/as/7k4rssnm8hbmr6mjf94qmck/104210-DIGITAL-ST01IB01-INSTALLER_MANUAL-TA-EN-00-V3.pdf) it does show you how to setup using eBUS. The likely reason it doesn't show on the consumer instructions is because you would have to open the boiler casing which isn't allowed by a normal person and so they show how to replace like for like.
Vaillant can say what they want but Tado does work with eBUS on a combi like yours.
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Thanks Gary. Yes, the wired Tado ships with instructions to set up on ebus on the controller, but as you say it doesn't cover the changes you have to make inside the boiler, which would normally need a professional. Luckily today my gas engineer who was doing a routine service did the wire change inside the boiler, and it was straightforward, although he wasn't sure whether or not to use the link cable (it turned out that he did). He also confirmed that by doing this the digital connection in the Tado would be within the ELV limit. So I now have a modulating set up, and hopefully it will go well. Tado needs to clarify it's installation instructions to make it clear that there are two ways to install the controller, one being the relay switch that the consumer can do on their own, the second way being digital that will give modulating benefits but needs a professional to open the boiler to change the wires there. Also it appears that digital connections are not commonplace in the industry - my gas engineer who has been in the industry for at least ten years had only ever done one before (at the start of his career) and I believe the stats are about 1 in 20 are done this way....0
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"Also it appears that digital connections are not commonplace in the industry -"
See also: tado UK receiver comes without digital connections...
Different on the continent, although a lot of boilers are still using relay control too. Also it seems that generally speaking the boilers here have their wiring compartment set-up so you don't need to strip the housing off to connect a thermostat.1 -
I'm following what's said here as have just bought my first Tado wireless stat system. The instructions do not help me, too non-specific for the 837's wiring. Can someone point me to where I should fit the blue, brown and grey wires please. My Vaillant board and the wiring diagram attached.
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What kind of installation are you trying to do? Relay or bus?0
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Sorry I didn't do the bit inside the boiler so I can't help with it. Also I understand that it's essential to have the wired controller as the wireless one only works if it is an EU type?0
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Johnnyp78: Sorry, all new to me so I'm just trying to get my new wireless room stat to replace the previous wall mounted one. I was lead to believe it was straightforward and guided by the app. Is it possible to tell from the existing wiring if the wired stat is relay or bus? I can see two wires in the 24v RT, would they be coming from the wall stat?
Stephen_Hall: we have just the one wall stat. Does what you say mean the Tado wireless one will not work with a UK Vaillant ecoTec plus 837 boiler?
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Just had a reply from Tado. I thought the whole point of smart thermostats like Nest, Hive etc. is that you can control them remotely. And, if any professional installers can do it then why can't Tado up their game and explain how? 😣
Hello Stan, thank you for contacting us.
If you are not replacing the wired room thermostat directly with wired Smart Thermostat, we cannot provide instructions.
As an alternative, you can contact a local engineer to help you install your tado° devices. Please note that we don’t have a list of professional installers, but any of them can install tado° using our Manual for Professional Installers.
Kind regards,
Kristina
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Having read the Tado blurb a relay connection (on/off) is what our wired stat provides so a wireless relay connection is all I'm hoping for.
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I’m a bit baffled by Tado’s response but you haven’t said what device you’re trying to install, is it a wireless receiver or a wired thermostat?
In both cases for a relay connection you need the wires coming from the 24v block for a potential free connection to COM and NO. The wireless receiver needs power as well so you should be able to run a connection from L and N on the x1 block.
I would check the manual though. If you tell the Tado app you’re installing a wireless receiver without having anything previously installed you might get clearer instructions.
Just to add that you should be gas safe if you’re opening up the boiler or using a professional who is.0 -
Thanks JohnnyP. The app goes to great length regarding the install about making sure the power is off. It did strike me as quite invasive for the average Joe to be told to remove the front cover of the boiler, locate the appropriate terminals etc. As you say, I'm trying to connect the wireless receiver to the boiler so that the wireless thermostat can control it. A £99 kit from Screwfix which I thought was good value and, up to this morning, the whole install process has been pretty simple.
I think if I sat down and stared long enough at the diagrams i'd be able to work out what needs to go where. I've built full car wiring looms in the (distant) past so not totally daft with circuits but 230v and gas combi boilers is not something I want to take a chance on. The little professional guide in the box for combi boilers is also a clue and, I believe, is what you've just said.
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Follow the potential free wiring. If you’ve built a wiring loom you’ll be fine! Take n and l from x1 and com and no from the white block. I can’t really see any other way to do it.0
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Thanks. I also asked a local CH plumber who I did some IT work for a couple of years ago and he said the same thing. Meanwhile I've configured the receiver with a temp connection to a 13 plug and all fine so should be up and running tomorrow ✌️
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The three pairs of connectors (blue, white and red/pink) X100 on the top left of the first photo are key.
Probably they are readily accessible without really opening the innards of the boiler, to avoid needing gas-safe people to do the wiring for you.
Each of these unplugs easily, then you can unscrew the terminals, rewire, and plug them back in, without coming near to the dangerous/scary/magical gas/water/mains 'plumbing'.
Blue connector: used to override everything and prevent boiler from turning on when open. Notice this is currently bridged closed, just leave it like that, or you could put a timer there, or a 'panic' switch (or summertime switch-off switch)
The white block is for a Relay Thermostat, and is most likelt currently wired to a room thermostat. You could just replace that room thermostat with a Wired tado one, or even the wireless receiver (in relay node, using COM and NO connections), although for the latter it would make sense to not put it in a living-room, but just somewhere near the boiler, out of sight, but reachable via radio waves (so don't put it in the 'shadow' of for instance the metal boiler shroud). This is all very low voltage (24 V DC, like a truck battery) and power (not like a truck battery, just look at the thin telephone/network/model-trainset wires used, not going to melt a wrench if you short circuit them, just turn on the boiler), so you can just touch them and won't get shocked. (Don't lick them...)
The red block is for the digital bus, if you have the wired thermostat, or version of the receiver that speaks digital, you could wire it up there instead of on the relay connector. If tado speaks the digital dialect of this boiler, it can then control it over the bus. You can probably cheat (unless the plugs are keyed) and not re-wire the connectors on the boiler-side, just put the white plug in the red socket for your first tests.
For wiring you could use some old telephone cable, left-over wiring from a model-trainset hobby, or a networking cable; the little connectors might even fit on heavy mains flex, but that would be overkill, and make it look scary for no reason.
The thermostat/receiver diagrams may look scary with their 'live' and 'neutral', but it's just because it can be used with boilers that need to be switched with mains. I'd keep it simple and clear by /not/ chaining the tado receiver to the boiler mains, but just run the two thin communication wires between the relay or bus connectors, and plug (or wire) the tado in separately, so you can easily (re)move it if reception is bad or you decide to flog it off later on. Local rules or lack of outlets may force you to do it differently.1 -
@luteijn in the Uk you need to be gas safe if you break the combustion seal - if you take the front panel off for example, which needs to be done to get to the wiring.
Also you should take power from a fused spur, not wire to a plug.1 -
Yeah, so hopefully those connections are placed in a sensible location so you only have to open a hatch, just reach underneath, or only remove a 'decorative cover'. Anyway, since the picture of the board could be made, it is already accesible, so the proverbial cat is out of the bag.
From what I could find online for this type of boiler, removing the outer/front cover is needed to get to the electronics, but one could argue it is just a 'decorative cover', as it looks like there are no seals broken by removing it, it is just two retaining clips and one screw that secure it. So, luckily, even if it actually were/is illegal or a 'gray area' and thus not advisable for the average Joe to open that cover, it would probably not be actually dangerous from a gas safety perspective, unless one were to take the trouble to then muck around with the burner, heat-exchanger etc. that do have seals.1 -
No you’re completely wrong. Regardless of whether it’s dangerous in terms of gas safety, the boiler cover is an integral case, not decorative and it’s breaking UK law to remove it if you’re not gas safe. https://www.gassaferegister.co.uk/media/1449/who-can-legally-work-on-a-gas-appliance-factsheet.pdf0
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This is why I worded my previous answers the way I did. We basically agree: to both of us it is 'not clearly legal' for everyone to open this part, so it wouldn't be advisable to open itin the uk without being gas safe. It's 'clearly not legal' to you; 'arguably legal, and if not legal not more dangerous than say crossing a street diagonally' to me, but not clearly legal to either of us.
I'm just pointing out that since this cover for this boiler is not going to be air- or even watertight anyway, it is quite unlikely tomorrow's headlines are going to read something like 'Homeowner DIYs new thermostat, dies of CO poisoning' (or '...suffocates in methane cloud', '...fireball could be seen across the county'), even if they would bungle the refitting of the cover, and it was only resting on one top hook and the little retaining screw fell down a crack.
Dura lex, sed lex. Laws here are different, but maybe we'd also be better off with some harsher laws.0 -
Just to conclude this by saying that it's all working fine now. I ended up with the switched live arrangement; purple bridge wire between L & CH COM and single connection from CH NO on receiver to the single active RT (SL) connector on the Vaillant boiler. Mains feed by slipping the Tado blue and brown wires from the receiver into the matching 230v connector on the boiler (blue on right in picture above. As it happens, this is much along the lines of the Tado instruction when going through the app install guidance but so badly worded that I ended up confused and seeking help here.
Things were being made more complicated than necessary due to a flaky wifi connection to the receiver. It would lose connection after 3-4 hours and not reconnect. Simply using a longer RJ45 cable from my hub 2m closer to the rear of my house (hub is upstairs, 1st floor front and boiler is downstairs at the rear) has been enough to achieve a reliable (so far) connection.
Thanks everyone for contributions.
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