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Thread: Can I use weather compensator on Vaillant with evohome?

  1. #1
    Automated Home Sr Member
    Join Date
    Jan 2018

    Default Can I use weather compensator on Vaillant with evohome?

    Actually I lied. But I have two related questions.

    I have a Worcester Greenstar at home with a Honeywell evohome system (via a BDR91) and I'm about to install a Worcester external air temperature sensor.

    My understanding is that I can attach the sensor, and configure the compensation curve etc. whilst continuing to use the evohome controller.

    Question one: is that right?

    I am also about to commission a Vaillant ecoTEC plus 630 system boiler, but using heat genius (based upon danfoss LC-13 TRVs) rather than evohome (because heat genius has occupancy sensors on a per room basis).

    I also want external weather compensation, using a VRC 9535.

    Question two - this is my main question: can I get weather compensation using the VRC 9535, without needing a VRC 700 controller (it seems in the UK, you can only buy then together).

    It is a bit late to switch from the Vaillant, but I could if I really had to...


  2. #2
    Automated Home Lurker
    Join Date
    Mar 2017



    I was just browsing, looking to see how others got on with Heat Genius/Genius Home/Genius Hub or whatever it's called today. I've had my system for 3 years with loads of issues and was thinking of abandoning the hub and adopting a more generic controller with open-source software. Anyway, that's another discussion entirely. Regarding weather compensation, Genius does this in the following way. For each zone (room) you can enable a pre-heat period. This can be a fixed period set by the user or "automatic". In automatic mode it works out how long the room takes to heat up from historic data, and takes account of the external temperature (provided from 3rd party weather data.) I do NOT use this automatic feature as the time period calculated was pretty erratic. I think this was due to the way the system controls room temperature by setting a temp on the TRVs but measuring with a separate sensor.


    Last edited by reasonrj; 28th March 2018 at 10:43 AM.

  3. #3
    Automated Home Sr Member
    Join Date
    Jan 2018


    Hi @reasonrj, thanks for your input.

    I use evohome at home (_very_ happy with it), but went for a Genius solution for a 7-bed HMO I am refurbishing.

    The main reason I chose Genius is that it appears functionally equivalent to evohome, but with occupancy sensors per room (I suppose a bit like a Nest per room) - whether it is just a effective/efficient is a matter to see. Having the occupancy sensors (and footprint mode) appeared the best solution, given that it would be unworkable to keep an eye on everyone's work schedule, etc. (e.g. some people would be working nights).

    On the Internet, opinions appear divided about the Genius system, where people are more universally impressed with evohome.

    At home I have tested a Danfoss LC-13 TRV (which doesn't report room temperature), a Popp OEM version of the LC-13 (which does), and (obviously) the HR92 TRVs, and I can say that the HR92 appears superior in it's accuracy, whilst the others appear to be adversely affected by heat coming from the copper pipework (they are mounted vertically at floor level). Nonetheless, the evohome system does benefit from room thermostats, of which I have a few.

    In any case, my Heating Engineer has no experience with either, and that has caused/is causing big issues so far with the commissioning of a system, hence the question above.

    For the benefit of others, I think the answer is 'yes' with a VRC430 controller (for the external weather sensor) mounted on the Vaillant boiler, but the specific wiring is unknown to me. FWIW, I also understand that a VR33 (bought from the Netherlands) can be used to convert eBus to OpenTherm...

    ... however, finding a local Heating Engineer who has experience with the above is a great difficulty. In fact, I have problems just finding a plumber who I'd use a second time! This is a sad fact, I guess, of supply & demand!
    Last edited by zxdavb; 28th March 2018 at 01:23 PM.

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