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Thread: Evohome with multiple BDR91's, HR92's and UFH and NO boiler ?

  1. #1
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    Question Evohome with multiple BDR91's, HR92's and UFH and NO boiler ?

    Hello,
    Firstly, welcome and thank you for many good tips already from other threads.
    Unfortunately I was not able to find answers to all my concerns and that's why I'm starting separate thread. I would appreciate some help in planning my Evohome installation in my countryside house. For quite some time I'm planning to upgrade the current heating system with Evohome for remote control, however I have quite unusual set-up and I'm not sure how to handle it.
    Current system is as follows:
    I have a boiler room with 800l heat buffer. The buffer can be heated from several different sources (heat pump, electric, wood) and I don't want to control with Evohome this stage. Hot water from heat buffer is distributed over the house in 3 separate water circuits controlled by 3 separate circulation pumps (let's call them A,B,C). Each of the pumps is controlled by on/off thermostatic switche in 3 different areas of the house (currently with classic electromechanical thermostats):
    • Circuit "A" provides heat to underfloor heating in big living room (no zones or separately controlled loops)
    • Circuit "B" provides heat to radiators on the first floor. Here I have in fact only one master bedroom which requires separate temp control. All other radiators may stay with current mechanical thermostatic valves as they are in non-living parts of the house.
    • Circuit "C" provides heat to radiators on the second floor. Here I have two bedrooms and a bathroom. Thermostat controlling the pump is somewhere on the wall in the corridor.

    Here is what I was thinking about:
    • to place 3 BDR91's instead of each of 3 thermostats in all areas of the house to control on/off for all 3 circuit pumps.
    • The Evohome control panel would be in the living room and would also serve as a temperature sensor for this zone and switch on/off it's BDR91 for circuit "A"
    • For circuit "B" (master bedroom) either:
      (a) HR92 connected to BDR91 demanding the heat from circuit pump "B" or
      (b) DT92/T87 placed in the bedroom paired with the BDR91 for circuit pump "B", but with old mechanical TRV's. In such set-up the TRV would be usually set to "high" and the room temp would be controlled by switching on/off the pump.
    • For circuit "C" (upstairs bedrooms)
      (a) HR92 in each room. All of upstairs HR92 paired with BDR91 demanding the heat from circuit pump "C". I guess this requires setting BDR91 "C" as a boiler control, right?
      (b) alternatively, DT92/T87 placed in one of the bedrooms paired with the BDR91 for circuit pump "C" and simply controlling all the upstairs as one zone.

    After quite some research and discussions: here are my concerns/questions:
    • it looks like it's not possible to have HR92's TRV in two different heating circuits, controlling two different BDR91's - circuit B and C. Is this correct? That's why I have the alternative solution (b) for circuit "B" eliminating the HR92.
    • is it possible: to have 2-3 separate zones in circuit "C" each equipped with HR92; all HR92's demanding the heat from BDR91 "C", but at the same time keeping the circuit A and B independent? e.g. if there is a demand in circuit A and/or B, but no demand in circuit C the BDR91 A and/or B would be in "on" mode and BDR91 would stay in "off" mode? I'm under the impression this is possible if BDR91 A and B are in the "electrical heating" mode (no boiler demand) but not sure if this can be combined with the BDR91 C controlling the HR92's ?

    I would be grateful for clear indication what and how can be done in such set-up and of course all other feedback on this design is highly appreciated!
    Thank you!

  2. #2
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    I think the simplest solution is to replicate your current setup with a BDR91 as actuator and T87RF/EvoTouch as sensor for A, B, C. Evohome will apply TPI to each BDR91 independently.

    If you want to add HR92s I think you will actually require multiple controllers each with a BDR91 configured as boiler control.

    A: EvoTouch and BDR91
    B: EvoTouch, BDR91, HR92s
    C: EvoTouch, BDR91, HR92s

  3. #3
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    Thank you for your input. This is the last resort option for me, as I would like to have at least independent control over the upstairs rooms (C). Also I'm not considering having 2-3 EvoTouch. I'll stick to one even if this means I need to go for the simplest solution.
    What about the option with BDR91s programmed as "electrical underfloor" which in theory should not call for heat from boiler BDR91 at the same time?
    In theory this should allow to have two BDR91s (A and B) as "electrical underfloor" and one BDR91 as boiler controller for the C circuit? Is it doable?

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    Quote Originally Posted by Wojtek View Post
    Thank you for your input. This is the last resort option for me, as I would like to have at least independent control over the upstairs rooms (C). Also I'm not considering having 2-3 EvoTouch. I'll stick to one even if this means I need to go for the simplest solution.
    What about the option with BDR91s programmed as "electrical underfloor" which in theory should not call for heat from boiler BDR91 at the same time?
    In theory this should allow to have two BDR91s (A and B) as "electrical underfloor" and one BDR91 as boiler controller for the C circuit? Is it doable?
    Yes, I think that should work, good thinking.

    A configured as electric underfloor, BDR91 and EvoTouch sensor
    B configured as electric underfloor, BDR91 and T87RF
    C with BDR91 boiler control and HR92s.

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    Also do you have an auto-bypass on C, required if all HR92s close?

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    Quote Originally Posted by kevinsmart View Post
    Yes, I think that should work, good thinking.

    A configured as electric underfloor, BDR91 and EvoTouch sensor
    B configured as electric underfloor, BDR91 and T87RF
    C with BDR91 boiler control and HR92s.
    Thanks! Are you certain it's allowed configuration and I can mix the "electric underfloor" BDR91's with "boiler" BDR91 in the same EvoTouch system?
    Also, will configuring BDR91 for water UFH as an "electric" will have any other influence on the system? Like different way of operating or "learning" pattern?

    Quote Originally Posted by kevinsmart View Post
    Also do you have an auto-bypass on C, required if all HR92s close?
    No, I don't think there is a bypass for circuit C. Maybe it's a stupid question, but why would I need one? The pump C should be running only when there is a demand for heat from one of the HR92'w right? If all close, they will also stop demanding the heat from the "boiler" BDR91 which operated the pump. What am I missing?

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    Quote Originally Posted by Wojtek View Post
    Thanks! Are you certain it's allowed configuration and I can mix the "electric underfloor" BDR91's with "boiler" BDR91 in the same EvoTouch system?
    Also, will configuring BDR91 for water UFH as an "electric" will have any other influence on the system? Like different way of operating or "learning" pattern?



    No, I don't think there is a bypass for circuit C. Maybe it's a stupid question, but why would I need one? The pump C should be running only when there is a demand for heat from one of the HR92'w right? If all close, they will also stop demanding the heat from the "boiler" BDR91 which operated the pump. What am I missing?
    You can definitely mix electric heating zones with boiler controlled zones. I think preheating learning should still work correctly.

    There can be systemic delays resulting in HR92s closing before the pump is stopped. But I guess this could be a problem in your current setup. What happens if you close all your TRVs while the thermostat in C is still calling for heat?

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    Quote Originally Posted by kevinsmart View Post
    You can definitely mix electric heating zones with boiler controlled zones. I think preheating learning should still work correctly.
    Thanks for confirming. This is good news for me!

    Quote Originally Posted by kevinsmart View Post
    There can be systemic delays resulting in HR92s closing before the pump is stopped. But I guess this could be a problem in your current setup. What happens if you close all your TRVs while the thermostat in C is still calling for heat?
    Honestly, I'm not sure what happens in such situation, but I'm sure it happened many times in the past without any bad consequences. My assumption so far, was that there is a heating loop and all radiators are peripherally connected to it. So if all radiators are closed and the pump is running, water would just circuit in a big loop. But now I wonder if this is the case...
    What happens to the circulation pump if it pushes the water to the closed circuit for longer time?

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    You will dead head the pump, possibly reducing its life.

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    Thank you for all the help.
    For anybody who might be interested in this thread in the future here is what I did.
    Finally, after some thoughts I decided to go for the simplest set-up:

    1. Evotouch in Zone A with BDR91 (as zone valve) to control UFH. No Boiler control set-up in the system at all.
    2. circuit "B" (master bedroom) with DT92 placed in the bedroom paired with the BDR91 (as zone valve) for circuit pump "B". With old mechanical TRV's, no HR92. In such set-up the TRV would be usually set to "medium/high" and the room temp would be controlled by switching on/off the pump.
    3. circuit "C" (upstairs bedrooms) with T87 placed in one of the bedrooms paired with the BDR91 for circuit pump "C" and simply controlling all the upstairs rooms as one zone. No HR92s.



    I decided to go this way, as I was told by Evohome tech person that setting-up my zone circuit pumps as electrical heating might not work as expected. Also, this way it's much cheaper and in most cases will allow me to do what I want anyway. Finally, after some time, if I find it not suiting my needs, I can always add HR92s and reprogram Circuit C to boiler control + A and B to electrical.

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