Vaillant Ecotec Plus 630


I’m about to upgrade my ancient Potterton boiler to a Vaillant Ecotech Plus 630 system boiler.

I’ve been a Tado user for the past 4 years and want to carry on using my Extension Kit and TRVs.

The extension kit is a V3 not a V3+.

I’ve done a lot of reading and can’t find a definitive answer as to whether I’ll be able to use Tado properly (ie with modulation and ebus) on the new boiler or whether I’ll have to make do with a simple on/off relay setting.

It was looking like it wasn’t going to work but then I came across some more recent posts in this thread that sounded more promising (eg the post by @scgf)

Can anyone confirm the current compatibility status please for a V3 extension with a Vaillant system boiler?

Will the boiler work with Tado as-is?

Will it work if I buy a VR65 controller?

If it won’t work, would I have any more joy if I went for a Worcester Bosch boiler instead?



  • johnnyp78
    johnnyp78 ✭✭✭
    edited August 2022
    Have you spoken to Tado support? It’s unlikely you can use Opentherm with a system boiler unless the hot water tank is wired directly through the boiler but there’s a chance you could use ebus. I think in general hot water controls need to be connected by relay though.
  • Spoke to Tado support today. They simply said that Tado only supports relay mode when it comes to system boilers.

    Even if I could use modulation for the CH and stick to relay for HW that would be a help.

  • I’ve got a feeling it’s one or the other - if you look at how the extension kit is set up it looks like you can only tell it to operate in digital or relay. Might be worth getting the Tado to control the heating and keeping a separate hot water programmer? Otherwise I think (but don’t know) it’s possible to have both with something like evohome or genius.
  • @johnnyp78 how do you set it up to control just the heating in digital mode? Most of what I've read suggests it's relay only, even if you only want it to control the heating and not the HW...

  • It depends what you’re referring to. The old extension kits are digital/relay, the current uk wireless receivers are relay only and the EU ones are digital/relay (I think). This is how you set them up for digital connections
  • Thanks for the PDF. I'd not seen that before.

    So page 12 of that PDF suggests that the Tado can talk to the Vaillant boiler via eBus. Does that actually work, though?

  • I don’t see why not, you should be able to tell it you don’t want hot water support and control that separately. The only way it would work for hot water is if your tank was connected to the boiler digitally too, which I think is quite uncommon.
  • The hot water tank won't be connected to the boiler other than by pipes. :-)

    So, if I've understood correctly, you reckon that I could use any old controller for the HW and then control the CH with Tado, either via eBus or via OpenTherm?

    Note that for OpenTherm it appears you need to add the VR33 module to the boiler and that's not supported in the UK without invalidating the warranty. Therefore eBus is the only real option.

    Has anyone here had that working in the way Johnny describes?

    And will it then do modulation or is it just going to do basic on/off but via the 36V DC digital channel rather than through AC switching?

    Forgot to say in reply to the earlier post - I have an older V3 (not 3+) non-wireless extension kit.

  • Your V3 extension kit is fine, if it’s a digital connection (ebus/Opentherm etc etc) Tado will modulate output, though you should set the max flow temp to 55c or lower to run the boiler at its most efficient.

    I haven’t tried it myself as I have a combi but should be very easy to try out - you only connect two wires with a digital connection. Obviously there may be some esoteric wiring that hasn’t been taken into account but I don’t see how. I think with ebus the extension kit doesn’t even need a separate power line.
  • Thanks.

    Interestingly, I went back to Tado support and pointed out that their own PDF says you can connect Vaillant boilers via eBus. And their response was that that only applies to combis - even though the PDF doesn't make any distinction between boiler types.

    So maybe what they mean is that eBus will work with system boilers but only for the heating side of things.

    I wonder what would happen if I connected the eBus terminals of the EK direct to the boiler eBus terminals and then connected the hot water relay terminals of the EK to the hot water zone valve...

  • Tado is very much geared toward combi boilers, which are standard in the rest of Europe. If you install a digital connection you’re basically running your system boiler as a combi - Tado won’t be able to ‘see’ the hot water tank or programmer. Pretty certain if you connect digital and relay to the extension kit what will happen is it will set itself to digital and ignore the hot water relay connection, but you’re welcome to try.
  • So perhaps this is where the VR65 comes into play:

    If I've understood correctly, I could wire it up as per the diagram on page 8, but replacing the Vaillant's VR360 controller with the Tado extension kit instead. The EK would then send an eBus message saying to turn on HW or CH and the VR65 unit would convert that into a digital message to the boiler and a relay message to open the HW or CH valves.

  • johnnyp78
    johnnyp78 ✭✭✭
    edited August 2022
    Assuming your boiler is wired like that, yes. As I understand it most system boilers simply pump hot water to a motorised valve, which then decides whether to send it to the hot water tank or the radiators according to which way it’s switched. That’s what Tado controls in hot water relay mode. However, yours may be different.

    Edit: I’ve just had a look at the manual you posted - in both the standard system layouts (s or y plan) it looks like the hot water is still controlled by relay, it’s only the heating that’s controlled by ebus. I don’t think you’re going to get around this with Tado but I might be totally wrong, there’s a chance it might work how you said, assuming the boiler is sophisticated enough.

    Thinking about it again it can’t work like this - digital connections don’t control hot water by turning it off and on, they tell the boiler to set a temperature. In your case you need a relay connection to move the valve(s) between the boiler and hot water tank and Tado can’t provide that as well as a digital one.
  • I forgot the other factor - the water in your tank needs to be heated to 60c and Tado wouldn’t be able to do that if it was modulating output temperature levels. I think even with a separate hot water programmer you’re going to have to trouble with this, unless it can override the Tado and get the boiler to pump water to the tank at a high temperature. Basically I think it’s going to be much easier to stick with relay on the Tado. It can imitate modulation by cycling on and off in relay mode so you’ll still get some of the energy savings.
  • Thanks @johnnyp78. I think if I can get hold of an old VR65 that might be worth doing and it sounds like that device always requests 80 degrees for HW heating - for the reason you've said.

    Failing that, it looks like I'll have to stick with relay mode. To be fair, that's been fine for me for the past 26 years of home ownership and, even in relay mode, my new boiler will be a lot more economical and efficient than the one from the year 2000 that it's replacing.

    Thanks for all your help.

  • If you’re willing to give it a try with the VR65 it’s worth a go. Not sure how you can get the Tado to give you a simple on off hot water control in digital mode but there may be a way, or the control box may be clever enough to interpret the hot water temperature. There’s only one way to find out… Just make sure you’re getting hot water above 60c in the tank or flushing it regularly.
  • @autolycus did you ever get anywhere with this? We have an Ecotec plus 630 too and a HW tank. I’ve been running it on relay for 12 months but with ever rising energy costs I would prefer ebus if possible.
  • I’m also very curious about how this went for you? I have a 630 and tank, and early extension kit. I currently only have single channel (ie heat) on my 630, as far as I can tell all that happens for hot water is a valve is opened to the tank heat exchanger and the boiler is fired. What’s frustrating is the boiler modulates low so it can take ages to heat up a tank. If you managed to separate hot water and heating with the above setup that would be great.
  • It seems someone has managed to, even with a VR66:

    Has anyone here managed to get Tado to modulate their Vaillant System boiler via the vr33 OpenTherm module?