Vaillant ecotec plus 835 & evohome & opentherm compatible?

1 Feb 2016
Reaction score
United Kingdom
Hey all.
I've been researching "smart" room stats and TRVs for my new Vaillant ecotec plus 835 boiler.
The boiler is a brand new ERP compliant boiler.

I've come across two products that appeal to me.
Tado & Evohome.

Both (Tado coming soon) offer "Smart" zoning using replacement TRVs without the need to alter any pipework.

At the moment I'm leaning towards Evohome because the scheduling and warmup learning is done by the controller in the house, where as Tado requires a constant internet connection and relies on Tado's servers to do all the work even for basic scheduling, this also assumes that they remain supported for years to come.
I asked Tado support about this and they basically confirmed without the internet connection the system goes into manual mode & is no smarter than my current T6060.

Anyway I digress.
Essentially I'm wondering is the Evohome system with TRVs compatible with my Vaillant ecotec plus boiler?
I believe it might be possible to connect the evohome opentherm R8810 unit to the Vaillant system using an eBus adapter to control flow rate and improve efficiency further is it worth the extra cost and complexity would additional boiler programming be required for a UK boiler?

Thanks for your time.
Last edited:
Sponsored Links
evohome is bloody brilliant for heating control. every room at the temp you want when you want it, the learning does work. I wanted to buy something from a company with a recognised background in heating controls, all my previous stats (e.g. CM67) have been honeywell, so stuck with them. Didn't fancy any of those coming at it from the "cool connected home startup" angle.

In standard config, with the evo sending on/off to the boiler just like a room stat, it should be compatible with pretty much any boiler. however, I also have opentherm (with a viessman heat-only boiler) and my experience of the OT aspect has been rubbish so far, in particular for DHW. I have a thread ongoing about it for the details . so my counsel is be very wary of opentherm.
Your boiler is totally different to the OP's Sandy.

Not only is it a combination boiler, Vaillant UK don't want us playing with OpenTherm, although you can get them to work if you know how ;).

The OP would be better using EvoHome with a BDR91 and just turn his heating flow temperature dial down to 50 degrees.

That way he maintains his warranty on the boiler.
Sponsored Links
You can link Evo on a Vaillant combi and their own weather comp.....
Unless they have changed their minds in the last 6 months.
i see but surely its like any other ebus controller as far as theyre concerned.
the boiler software is built to work with it.
have you had issues in the past?
It is a non supported product in the UK.
obviously i wouldnt expect them to support the module however this still have a 2 year warrenty from the retailer thanks to the 1999/44/EC directive.
i would nonetheless expect vaillant to still warrenty the main boiler just like they would if the system was used with any other controller.
i appreciate the advice and may well go with the BDR91
Last edited:
i would nonetheless expect vaillant to still warrenty the main boiler just like they would if the system was used with any other controller.

It is only a contact closure to the boiler. Could be any type of contact, a manually operated switch or a relay controlled by a complex computorised building management system. The boiler cannot tell the difference between them.

That said maybe the manufacturers of the boiler have set requirements for minimum periods of contact closed and contact open. They may say that if the contact opens and closes without compliance with these minimum periods then the boiler may suffer harm. This would then provide them with a way to void the warrenty.

The controller they recommend ( and may have financial interest in ) will be programmed to ensure the requirements for minimum open and closed periods are complied with
the evohome controller has a setting for cycle count which is i thinks controls what you describe, this is by default set at 6 times per hour which my installer said is below limits.

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Sponsored Links