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Thread: Leaning towards Evohome but....

  1. #1
    Automated Home Lurker
    Join Date
    Nov 2020

    Default Leaning towards Evohome but....

    I need some help please with info on Evohome before deciding to invest.

    I have an existing S Plan+ I think It's called with two heating and one hot water valves with the micro switch live firing the boiler/pump. It's a sealed system with new condensing boiler and modulating pump located remotely in garage from existing controller, valves and tank with stat and high limit stat in one. The boiler requires a permanent and switched live for post purge, pump overrun etc but I only have a switched live with jumper to permanent live temporarily done at boiler. It's not feasible at the moment to run second mains feed.

    After looking at many different control systems the Evohome may look best fit for me, but there's one major hurdle to clear first, and is the essence of this first query. Does anyone know for definite if the Evohome controller can activate a valve BDR91 and the boiler BDR at the same time. My thinking is that if it could I can use the existing switched live cable as a permanent live from the existing controller fused spur and split in garage to power boiler and provide live for boiler BDR. This way I'm on the same RCD and breaker from main consumer unit. I can't have a separate supply from garage consumer unit with it's own RCD as I'd have separate neutrals.

    The only other option I see is to install something like a mains link RF switched live but assume this works at 860 MHz ish and may interfere with Evohome. I see from other posts that the Evohome can be particular with rf levels and unit placements etc and may only give myself another headache.

    I have other questions on this but feel that unless I can do something like the above I may have to think the whole thing through again. I don't work at heating/plumbing but have looked after the basics of my own system for years, mostly successfully !

    I did see some reference maybe from DBManrdake about some of what I'm trying to do but can't remember for sure. I'm sure someone might know about the switched live problem anyway and I can work from there.

    Many thanks in advance.

  2. #2
    Automated Home Lurker
    Join Date
    Nov 2020


    I may have found an answer in a reply to another post by DBMandrake.

    Option 2 - three BDR91's - the same as above except the orange wires from the zone valves are not used. Instead the third BDR91 is connected directly to the boiler and is bound as "boiler control" in the Evohome system, in addition to the other two relays being bound in the hot water config as before.

    If I can bind a boiler relay BDR and have my 2 heating zones combined into one and have a hot water BDRs, so three in total I may have what I need to start with. I would hope to add HR92s in future but have a total of 18 rads and 2 towel rails so would only have some rads controlled.

    I assume the above might work. I had forgotten that the controller activated the BDRs, and especially the remote boiler one so should negate the switched live cable.

    Any help with the above would really be appreciated and any more info available if needed.

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