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Thread: Evohome HR92s not sending demand for heat.

  1. #1
    Automated Home Jr Member
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    Default Evohome HR92s not sending demand for heat.

    Hi all,

    After months of trying to get someone to install my evohome system I finally got it in last weekend.

    Downstairs is underfloor heating with a singlezone thermostat in each room
    Upstairs are 4 radiators with HR92 TRVs.

    Downstairs heating and hot water are both working properly, however the upstairs radiators are not sending a call for heat when needed.

    The HR92s are bound to the controller and show the current temperatures and set temps, the motorised valves open and close when the set temp is changed either from the controller or on the TRVs themselves but the boiler does not fire up when needed. If the underfloor heating is on then the upstairs radiators will heat up as required but if all the zones downstairs are off then the boiler is off and there is no heat going to the radiators.

    I have done RF checks and got signal strength 5.

    Any ideas what is wrong or what checks I can do?

    Thanks

  2. #2
    Automated Home Legend
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    Default

    We'd probably need to know a bit more about how your system is set up to help.

    What kind of boiler do you have, and how is the Evohome system configured to fire the boiler ? Are you using the OpenTherm bridge, or the BDR91 relay box ?

    You have a mix of underfloor heating, radiator valves and hot water - so how many BDR91's do you have in total ? I'm assuming the system is S-Plan - are the zone valves wired to fire the boiler ? Do you have the HCC80 underfloor mixing controller ?

    The issue it not going to be the HR92's not calling for heat, it will be how the Evohome is wired up to fire the boiler.

    One thing you could check is in the installer menu (long press on settings) go into system summary where you will see the current heat demand for each zone - take a picture of this when your upstairs radiators are turned on but your boiler is not firing.

  3. #3
    Automated Home Ninja
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    Since you've described upstairs and downstairs operating differently, have you got separate zone values for each floor, and has your boiler been configured to fire off the orange wire from only one of the zone valves?

  4. #4
    Automated Home Jr Member
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    Thanks for the replies, was a busy week so only just getting round replying. Below a description of my setup with some pictures to help identify where the issue is.

    The boiler is oil fired with 2 x BDR91 relays wired in (1 for heating, 1 for hot water).
    20180318_115609.jpg

    The hot water kit is installed and working fine.

    Heating upstairs is by radiators (total of 4), each with a HR92 TRV.

    The underfloor heating has 6 zones, each with a T87RF2033 single zone thermostat linked to the underfloor heating controller (HCC80R with extension module).
    20180318_120252.jpg
    20180318_115708.jpg

    You can see in the above photos that there is another pump for the heating system and 2 x zone actuators, 1 for the underfloor and 1 for the upstairs heating (I think!). Im guessing there is nothing telling this pump to go on when the upstairs radiators need heat.

    Thanks for any advice how to sort this.

  5. #5
    Automated Home Jr Member
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    Quote Originally Posted by dty View Post
    Since you've described upstairs and downstairs operating differently, have you got separate zone values for each floor, and has your boiler been configured to fire off the orange wire from only one of the zone valves?
    dty, Im not sure about this as I didnt do the wiring. Is there an easy way to check?

  6. #6
    Automated Home Legend paulockenden's Avatar
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    BDR91s are *much* too close together.

  7. #7
    Automated Home Lurker
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    Does the green light on the BDR91 relay box come on when the upstairs HR92s call for heat ?

  8. #8
    Automated Home Jr Member
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    Quote Originally Posted by rarrarrar View Post
    Does the green light on the BDR91 relay box come on when the upstairs HR92s call for heat ?
    Yes, just checked, all heating off and it goes off, 1 radiator upstairs on and it goes on.

  9. #9
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    Quote Originally Posted by paulockenden View Post
    BDR91s are *much* too close together.
    Care to elaborate? How far apart should they be and why? Interference?

  10. #10
    Automated Home Lurker
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    Quote Originally Posted by Ozzx View Post
    Yes, just checked, all heating off and it goes off, 1 radiator upstairs on and it goes on.
    Therefore the Evohome controller is calling for heat and sending the signal to the BDR91 relay box which is receiving it (Green light).
    That would suggest the Evohome system is working fine, but the wiring of the Relay into the boiler to fire it up is wrong or possibly the BDR91 is faulty and the actual relay inside is not being activated.
    Relay operation easy to check, wiring not so easy as the underfloor heating and HW control are all involved.

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