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Thread: BDR91 is not following PTI

  1. #1
    Automated Home Lurker
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    Default BDR91 is not following PTI

    I set my BDR91 for underfloor heating 6 times per 1 hour with minimum run time 5 min. BDR91 is not following command, it starts and runs less than 5 min, sometimes 2 or 3 minutes and stops. Does it has something to do with Opentherm relay for boiler? if boiler goes to st-by mode ( request temp reached set point) the BDR91 stops?

    If BDR91 stops for the underfloor pump, does boiler with opentherm relay should go to st-by mode directly? if not, how to achieve it?

  2. #2
    Automated Home Jr Member
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    The min run time parameter only applies to the boiler relay, not UFH relay.

    With the OpenTherm gateway the boiler will continue to run even when the UFH pump has stopped.

    I changed my UFH BDR91 to an HM80 for better control of a single zone. But even with this, Evohome can show e.g. ~20% demand when the HM80 has decided to stop the mixer pump. If no other zones are calling for heat, water will be pumped through the auto bypass valve.

  3. #3
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    Does not looks like very energy efficient. Hm80 gives more better control, but still boiler is running and pump is off. Heating going away through the primary loop. Does it possible to connect opentherm and on/off relay at same time?

  4. #4
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    Quote Originally Posted by Mindaugas View Post
    Does not looks like very energy efficient. Hm80 gives more better control, but still boiler is running and pump is off. Heating going away through the primary loop. Does it possible to connect opentherm and on/off relay at same time?
    As you have both radiators and UFH, I can't think of an easy way to do this with Evohome. You could detect when the UFH pump is not running and stop the boiler, but there could still be a demand from one or more radiator zones. You would probably need to use something like Domoticz with an HGI80 to monitor demand from all zones.

  5. #5
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    I can see zones demand from evohome interface. but manual operation i believe is not solution, because i just made system fully automated.

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