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

  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?

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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.

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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.

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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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    I feel I may be confusing matters (and myself!), I'll try to simplify my setup:

    One gas boiler (approx 12 yr old, Glow worm) with pump overrun (S-Plan terminal 9) and
    S-Plan wiring and plumbing ( CH and DHW valves)

    One BDR91 wired into the CH valve (switched output to S-Plan terminal 5),
    one more into DHW valve (switched output to S-Plan terminal 8) with one wireless CS92 Hot Water sensor,
    Orange wires from valves to boiler demand (S-Plan terminal 10)

    I have 9 Evohome zones, all controlled with various numbers of HR92 TRV heads.


    6 more rads with no TRVs - Towel rails, Hall, Vestibule, loos Which I'd rather only receive heat when there is central heating demand (until I fit valves to control them - though I'll likely leave the towel rails as-is).

    My issue is that with my current setup, when there is DHW demand, the BDR91 for the central heating is also switching, so opens the central heating valve and heats my uncontrolled radiators.

  8. #8
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    It does look like the BDR91 for heating is still set up as a boiler relay and should be configured and rebound as the heating relay.
    Last edited by Jackthom; 18th February 2018 at 05:10 PM.

  9. #9
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    Quote Originally Posted by fysmd View Post
    My issue is that with my current setup, when there is DHW demand, the BDR91 for the central heating is also switching, so opens the central heating valve and heats my uncontrolled radiators.
    Can you help others to help you by posting on here the configuration? Go into the installation menu (long touch on "Settings") then tell us what is in the "System Summary" and the "System Devices menus". The System Devices should show "Boiler Control" as "None". For reference, here are mine:
    System summary.jpg System devices.jpg

  10. #10
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    OK, here ae the settings screen from my controller but I don't understand how I add the CH BDR91 to the system?

    IMG_0862.jpgIMG_0863.jpgIMG_0864.jpg

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