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Thread: Configuring BDR91 as central heating relay

  1. #1
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    Default Configuring BDR91 as central heating relay

    Hello. Would someone be kind enough to point me at instructions for configuring a BDR91 as a central heating relay? In the installation guide there are instructions for various configurations but not as a simple heating demand relay as far as I can see.

    I have a non standard installation with a gravity fed hot water tank, there is a single flow pipe from the boiler which is split via a T piece to HW and CH and there are two returns, there is a pump on the return from the radiators. I would like the pump not to come one when there is HW demand only.

    Currently the pump is connected to the boiler control BDR91 so it comes on when there is demand from CH or HW. I have a spare BDR91 I just need to know how to configure it to respond to CH demand only then I can move the pump to it. The only valve in the system shuts off the flow of hot water to the tank when there is no demand to prevent over heating, this is controlled by the BDR91 that came with the hot water kit.

    Apologies if this is covered elsewhere, I have searched high and low for the answer with no success.

    Other than this minor issue it all works perfectly.

    Thanks in advance

    Graham

  2. #2
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    That is a bit non standard. So how many BDR91's do you have in total counting your spare one - two or three ?

    What you ask can be done easily if you have three - you can configure one as a heating zone relay, one as a hot water zone relay and one as a boiler control relay.

    Wire the boiler control relay to fire the boiler, wire the heating "zone valve" relay to run your pump, and wire the hot water zone valve relay to open your hot water loop zone valve.

    If you only have two you can't directly do what you want because normally you would use the limit stop switches on both zone valves to fire the boiler, but you don't have a zone valve for your heating only a pump. Therefore either a third BDR91 is required as a boiler control relay or two other conventional relays configured to fire the boiler if either hot water zone valve or pump get power.

    When you have 3x BDR91 the heating one turns on only for heat demand, the hot water one turns on only for hot water demand, and the boiler control relay turns on for BOTH hot water and heating demand.

    Does that help ?

    By the way I used to have a gravity circulation system like yours before I had evohome but I recently opted to convert it (plumbing and all) to fully pumped S-Plan as I was finding it was too slow for hot water to heat up as well as not having good control over temperature.
    Last edited by DBMandrake; 23rd November 2016 at 12:58 PM.

  3. #3
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    Thanks for the quick reply. I have 3 BDR91s in total. Two are installed and working, one for boiler control and one for the motorised valve on the hot water. My third (currently unused) BDR91 I want to configure for heating demand only and this is where I have been struggling. I tried to bind it as a zone valve as you suggest but the controller does not bind to the BDR91, I have cleared the binding on the BDR91 and then put it in bind mode but the controller is asking me to press the bind button on the sensor device like it expects a HR92 or similar. To be clear I am:

    Adding a new zone with the heating type ‘zone valve’
    Once the controller says press BIND button on the sensor I am clearing the binding and putting the BDR91 into bind mode
    The controller does not bind to the BDR91

    The installation guide seems to suggest a sensor should be bound before the BDR91 which is why I did not try this route. Any ideas what I am doing wrong?

    The conversion to a standard configuration sounds like very good advice but it will be a few years away as I intend to do it as part of a kitchen refurb, then I intend to do exactly as you suggest and move to fully pumped S plan (at the same time as replacing the pump and moving the boiler to the utility room).

  4. #4
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    Ok I see where you're going wrong, you're trying to bind the heating zone valve to a zone, you actually want to bind it as a heating valve under the hot water setup.

    So given that your configuration is probably a bit confused and scrambled now, here is what I would suggest to start fresh on the relay bindings:

    1) If you created a completely new zone to try to bind your relay to you should delete the zone. You would only use a BDR91 to control a specific zone if your radiator was controlled by a 2 port zone valve instead of an HR92, and this requires a remote room temperature sensor. The normal heating zone valve that controls all heating zones (traditional S-Plan heating zone valve) is set up in the stored hot water section.

    2) Finish wiring up your 3rd BDR91 to power the pump rather than taking pump power from the boiler relay as I presume you are now. You can easily test each relay does what you want by pressing the manual override buttons.

    3) Remove all BDR91 bindings at the controller - to do this go into the installation menu, system settings, stored hot water configuration - change this to NONE then confirm. This will forget your hot water schedule and temperature as well so you'll have to set that again later. Then go into system settings boiler control and also set this to none to remove the boiler relay.

    4) Clear all bindings on all three BDR91's - hold down the button for 5 seconds until it starts flashing slowly, then continue to hold the button for another 10 seconds until it changes to a faster flash. This fast flash means all bindings are cleared from the relay. Repeat this on the other two relays until all three are flashing quickly.

    5) Technically not necessary but its often recommended to reboot the controller before rebinding the relays so lift it off the dock and pop out a battery for a few seconds then put it back so it boots up.

    6) Go into the installer menu, system settings, stored hot water. There will be choices for hot water relay only or hot water and heating relays - choose the latter two relay option. Follow the steps to rebind your hot water temperature sensor, I don't recall off hand exactly what you press on the CS92 - check the evohome install manual. When it asks you to bind the hot water relay/zone valve press and hold the button on your hot water BDR91 for 5 seconds until it changes from a fast flash back to a slow flash then choose to bind on the controller, when the bind is successful the red light will go out. When it asks for the heating relay/zone valve do the same thing with the new relay you installed wired to your pump.

    7) After those two relays are bound and configured you can go in and set your hot water temperature and differential again as it will be back on the default.

    8) In system settings go to boiler control and choose to bind your boiler relay which is wired to the boiler, again by holding down the button for more than 5 seconds but less than 15 seconds so that it goes back to a slow flash. After you choose to bind on the controller the red light should go out to indicate success.

    It should now be working properly and you can re-enter your hot water schedule.
    Last edited by DBMandrake; 23rd November 2016 at 04:17 PM.

  5. #5
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    Smashing, that makes perfect sense and explains where I was going wrong. Thanks again for the swift and detailed answer, that has no doubt saved me an awful lot of frustration. Very much appreciated.

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