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Thread: EvoHome S-Plan heating relay operates with HW demand

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  1. #1
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    Question EvoHome S-Plan heating relay operates with HW demand

    Hello, I'm having issues with my EvoHome installation.

    When I see DHW demand only, the heater relay operates very quickly after the DWH one does.

    I have moved the two relays further apart; I've rebound both; I've run through guided setup again and I've even hit factory reset, all still performs the same still
    I dont think the relays are double bound - have followed the Evohomeshop guide on this.


    I"m wondering if I'm just making a silly mistake somewhere - any pointers much appreciated.

  2. #2
    Automated Home Legend paulockenden's Avatar
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    Definitely sounds like your heating relay is double bound as a boiler relay too.

    Did you do the 15 second button press to clear the original bindings? And have you definitely NOT set up a boiler relay for boiler control in the installer menu?

  3. #3
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    Quote Originally Posted by paulockenden View Post
    Definitely sounds like your heating relay is double bound as a boiler relay too.

    Did you do the 15 second button press to clear the original bindings? And have you definitely NOT set up a boiler relay for boiler control in the installer menu?
    Definitely done the 15s clear on both to clear them.

    However, when trying to fettle this I've also hit factory reset on the controller. After this, looking in system information I still see the two relays setup so I removed the config for CH and DHW. After rerunning guided setup for heating I'm in the same place again.

    If I must not add the boiler relay for heating control, what SHOULD I do, how would the boiler get a demand signal if not from this relay?
    Last edited by fysmd; 18th February 2018 at 09:42 AM.

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    I think you need to describe to us how your BDR91's are wired to your heating system.

    Do you have both a hot water zone valve and a heating zone valve ? And are the orange wires of both zone valves wired to fire the boiler ? In that case the two BDR91's should be wired to control the two zone valves, and you should bind these relays in the hot water configuration only. Leave boiler control relay set to none, because you do not have a BDR91 that is directly connected to your boiler. The boiler is being fired by the limit switches in the zone valves.

    If this is not your configuration, describe how your system is wired up.

  5. #5
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    Thanks DBMandrake, my setup is almost as you describe: I have replaced my old two channel timer with the two BDR91s and removed the old thermostat completely.

    The BDR91s are wired to the valves as you say and the orange wire from each is cabled to boiler demand.
    Surely if I bind both into hot water, I'll only get heating when there's hot water demand? I'm confused.


    I have a large house, currently with 6 rads which dont have control valves (towel rails, loos and vestibules). I don't mind heating these when there is heating demand (until I drain the system and add TRV valves) but it REALLY bugs me that a large space is being heated when I have only DHW demand.

  6. #6
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    Can you confirm you have a single zone for heating set up on the controller (as well as the DHW config which seems to be working OK)?

    The installation manual on page 20/21 tells you how to bind a BDR91, and an associated room thermostat, to a zone.

    http://www.honeywelluk.com/Documents...stallation.pdf
    Last edited by Jackthom; 18th February 2018 at 02:33 PM.

  7. #7
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    Quote Originally Posted by fysmd View Post
    Thanks DBMandrake, my setup is almost as you describe: I have replaced my old two channel timer with the two BDR91s and removed the old thermostat completely.

    The BDR91s are wired to the valves as you say and the orange wire from each is cabled to boiler demand.
    Surely if I bind both into hot water, I'll only get heating when there's hot water demand? I'm confused.
    Yes you are.

    From the pictures you posted later on you have your system set up incorrectly - you have added a boiler control relay when you shouldn't.

    In the stored hot water configuration it will ask you if you have a zone valve for both hot water and heating, say yes to having both valves.

    Then it will ask you to bind in order - hot water sensor, hot water relay, central heating relay. This is where you should be binding the central heating relay NOT as a boiler control relay, which must be set to none.

    Fully clear the bindings on both BDR91 with a 20 second button press then set boiler control to none and stored hot water to none to clear all the relay bindings at the controller end.

    The go into stored hot water and follow the prompts to bind hot water sensor, hot water relay and central heating relay.

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