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Thread: BDR91 and R8810A problems

  1. #1
    Automated Home Lurker
    Join Date
    Dec 2019
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    Default BDR91 and R8810A problems

    Good day to everyone. Seeking for help regarding relays BDR91 and R8810A.

    I have installed just newly Honeywell Evohome system at my home. short explanation regarding my current heating system. First floor has underground heating, second floor radiators and kombi kompact Hreco 36 boiler.
    Radiators are equipped with 3xHR92 valves and they work perfectly. Underfloor heating is controlled with turning On/Off circulating pump with BDR91 relay(binded to main interface), and boiler is fired by opentherm R8810A relay.

    1) The first problem I encounter is that by choosing on interface heat demand control "Open-therm" it fires boiler as should be, but he try to control BDR91 also by stages, BDR91 starts when heat demand is 100% and stop straight away it demands goes to 80%. Second time will start if demand goes to 100%. at same time boiler is running and circulating in the primary loop. I choose all available option as binding mixing vave, zone valve ... I changed Heat demand from open therm to on/of and the problem went away. Boiler is still controlled as opentherm. for me looks strange because it looks like that BDR91 for circulating pump interface is seeing as main boiler relay.
    2)At same time on R8810A relay I have 2xred ligth shot time on all the time. Hard turn of done times and it goes back after some while, but still keeping his job good and regulating boiler as I see in proper way.
    3) BDR91 controls my circulating pump PTI, so its starts and stops 6 times per hour and runs minimum 1 minute. Then the pump is off for short time, the boiler still On and circulating in primary loop. In meantime i loose energy via pipeping from 3rd to first floor. Would be possible to turn of PTI and run pump just on and off as longer demand is or not?

    4) can be pump damage of constant on and off?
    Last edited by Mindaugas; 30th December 2019 at 01:59 PM.

  2. #2
    Automated Home Lurker
    Join Date
    Dec 2019
    Posts
    5

    Default

    Also I noticed that if bd92 valve calls for heat, the all primary loop become hot, from 3rd floor to first floor. Bathroom radiator is small, so to heat it i need to heat entire 22mm size loop. I believe I loose a lot energy like this.
    Would be possible to install motorized 3 way valve with bdr91 relay close to boiler. It means the primary loop will become around total 2 m length + radiators piping if they are open. I could use one bdr91 for pump and valve .

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