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Thread: New home, mammoth Evohome install

  1. #21
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    Quote Originally Posted by bruce_miranda View Post
    I've attached two graphs which might explain how a normal BDR91 works.
    The first step graph is the Heat Demand the controller is sending the BDR91. Notice how the Heat Demand required, doesn't switch on and off, it goes from 100% down to 0% in stages.
    The second graph is actually tracking the time the BDR91 stays on and off. I have a Cycle Rate set to 6 per hour. Notice how the amount of time the BDR91 stays on within a particular hour reduces as the Heat Demand required reduces.
    My guess is that it's this part that must differently when it's paired as a Heat Pump Relay.
    Nice!
    Ok, that explains a lot. Curious how you can catch the signal send from Evohome to the BDR91
    Last edited by Fmb; 25th November 2020 at 08:47 PM.

  2. #22
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    Turns out I have odd twin pipe manual micrometric valves (flow+return+single rad pipe) for 2 thin vertical panel radiators, that I canít fit HR91s to, for my 4 towel rad circuit.

    I donít want those rads heating with the UFH, so no point replacing their NC zone valve with NO.

    So Iím thinking of connecting a BDR91 to the NC zone valve, so I can schedule when that zone is heating.

    But what should I use for the sensor? I guess I canít bind one of the HR91s as a zone valve sensor.

    Can you double bind a DTS92? Can I bind one of the UFH DTS92s, where the rads are, as an HCC80 UFH zone sensor and also as the towel rads BDR91 zone sensor?

    Or can I use my second Evotouch DHW zone, without a cylinder sensor, just to heat the towel rads for a short time twice per day?
    Last edited by kevinsmart; 12th December 2020 at 11:37 AM.

  3. #23
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    Quote Originally Posted by kevinsmart View Post
    Just placed a huge order with the EvoHome Shop for my new house, after getting to grips with the existing set up (Danfoss controls).

    Comprises of:
    16 x DTS92E Room Thermostats (I chose these as they will cover removed Danfoss thermostats better than T87RF)
    4 x HCC80R UFH Controllers
    1 x HCS80 Extension Module
    1 x HR914 Radiator Multi Zone Kit (Kieran recommended these over HR92s for towel rads)
    2 x ATF600 Wall Mount Kits
    1 x Evohome Connected Modulation Pack
    1 x Evohome Connected Thermostat Pack
    1 x ATF500 Hot Water Kit
    1 x Honeywell High Limit Pipe Thermostat
    2 x Honeywell 28mm N/O Motorised Zone Valves


    Going to have 2 controllers handling 23 zones: 19 UFH via 4 manifolds, 4 towel rads. OpenTherm with weather compensation implemented by my custom firmware on an OpenTherm monitor, reading external temperature sensor.

    DHW priority, closing N/O valves on UFH and radiator circuits.

    Removing existing Thermostatic Mixing Valve, which was set at 75C when I moved in (!) as I will limit the max OpenTherm flow temperature. Install a High Limit Pipe Thermostat to cut the UFH pump on over temperature, just in case.

    I learned from Kieran at the EvoHome shop that the controller was updated this year, requiring a different wall mount kit, ATF600 vs. ATF300 before.

    Looking forward to having Evohome again!
    Hey Kevin how are you setting up zones across dual controllers? THere's no clever trickery available right, you just have two distinct systems?

    I'd always wondered what Evo could control other than radiator TRVs, motorised zone valves, etc. Sounds a fun install, has this all been completed now?

  4. #24
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    Both controllers still talk to common zone valves and boiler controls.

  5. #25
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    Quote Originally Posted by MrBoy View Post
    Hey Kevin how are you setting up zones across dual controllers? THere's no clever trickery available right, you just have two distinct systems?

    I'd always wondered what Evo could control other than radiator TRVs, motorised zone valves, etc. Sounds a fun install, has this all been completed now?
    I was hoping it was going to be installed last week, but my installer needed to come round and get his head around what was required first.

    I still have an open question above in terms of how to best handle my radiator circuit where I can't fit HR91s to two of the rads.

    Hopefully he will be able to fit me in later this week.

    The 2 controllers will bind to the same OpenTherm gateway, which I think will map their highest percentage demand to a flow temperature.

  6. #26
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    Do the motorised valves pair with Evohome so you can just put them under the floorboards? I remember looking at that as a nice option for a room with multiple radiators, but wasn't confident it would work

  7. #27
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    Ideally no part of the heating system should go under floorboards, and certainly no electrical components

  8. #28
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    Unfortunately my installer got sick one day into the install, so not done yet, but I decided to help by pre-binding everything.

    So it turns out you can use an unmounted HR91 as a zone valve sensor.

    Also if you now order the HCC80R UFH controller, youíll find an HCE80R with an external HRA80 antenna in the box. Apparently due to component supply issues.

  9. #29
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    That's the install completed, and I've updated my OTGW weather compensation firmware.

    My inherited Vokera boiler has some limitations versus the Intergas I had before. Its minimum flow temperature is 40C unless switched with a jumper to an underfloor heating mode. On the other hand, it does report back the return water temperature, the Intergas HRE did not, so there is maybe some further optimisation I can do with that.

    Independent of Evohome, in OpenTherm mode, it also appears to briefly fire once per hour to heat to 40C.

    To determine that DHW is heating I had to fit a relay which open circuits the outside temperature sensor when the DHW BDR91 closes. When DHW is heating the OpenTherm outside temperature read request is invalid.

    So the changes I made to the OTGW firmware.

    Report the Max CH water setpoint as 60C rather than 80C reported by the boiler.
    Report the Max CH setpoint boundaries as 40-60C, rather than 40-80C. Evohome appears to ignore the lower bound, I see control setpoints in the 20Cs, but it limits its requests to within the max setpoint (100%->60C).

    Implemented a simple UFH weather compensation heating curve, TMax = 50C-outside temperature, capped at 60C. So at -10C: 60C, 0C: 50C, 10C: 40C.
    If the control setpoint is below the calculated TMax, it is not modified.

    When DHW heating is detected, increase the control setpoint from 60C to 70C.

    I now have a DHW priority setup. The UFH pump which receives demand from the 4 HCE80s is stopped and the NO UFH 2-port valve is closed.

    I'll continue to monitor, but it's all working great so far.
    Last edited by kevinsmart; 25th January 2021 at 07:45 PM.

  10. #30
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    Some observations from monitoring.

    This is apparently how the OpenTherm bridge converts a % demand into a Control Setpoint temperature:

    Control Setpoint = 20 + % x (Max CH Setpoint - 20)/100 Celsius

    I have two Evotouch controllers. The % demand converted is the highest of the two controllers.

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