Boiler Heat demand

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  • matchu
    Automated Home Lurker
    • Oct 2019
    • 5

    Boiler Heat demand

    Could someone clarity the operation of heating demand when using evohome on a combi boiler.. Will the evohome controller cycle the boiler defined "under cycle time" if there is no demand, or will a demand for heat have priority regardless of the cycle time?

    Basically will the boiler come on cause there is a demand or by cycle time

    Thanks in advance
  • DBMandrake
    Automated Home Legend
    • Sep 2014
    • 2361

    #2
    If there is no heat demand the boiler relay will remain off continuously. If there is 100% heat demand the boiler relay will be on continously. In either case the cycle time is not applicable.

    If there is a partial heat demand then the cycle time will be applicable and the heat demand percentage becomes a duty cycle. So for example if it's configured for 6 cycles per hour and the current heat demand is 30%, the cycle period will be 10 minutes, and the relay will be off for the first 7 minutes of each 10 minute cycle and on for the last 3 minutes of each cycle.

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    • matchu
      Automated Home Lurker
      • Oct 2019
      • 5

      #3
      Originally posted by DBMandrake View Post
      If there is 100% heat demand the boiler relay will be on continously. In either case the cycle time is not applicable.
      Is this the same operation if one was using opentherm?

      I ask as I originally configured boiler with opentherm but had to use a converter.. at first the boiler seemed to fire up when demand was 100% but I'm sure there was occasions where this wasnt the case. I have now swapped the opentherm with a relay and the boiler fires up alot more, especially when demand is at 100%. It could be that the opentherm/ converter configuration is not working correctly but I was not sure if the correct operation.

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