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Thread: Multi room and optimum start

  1. #1
    Automated Home Sr Member
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    Oct 2020
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    Default Multi room and optimum start

    In a multi room configuration, what determines the start time if optimisation start is enabled? Is it the first sensor to be added to the zone (ie heating starts so that the first bound sensor is at the SP at the scheduled time), or something else?

    I ask because I have a zone with two HR91s. One takes significantly longer to come up to SP than the other, so the start time is a long time before the scheduled start time, and the second HR91 is at SP for a long period before the scheduled time.

  2. #2
    Automated Home Legend
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    Default

    That's a very good question which I don't think anyone has asked before or has a definite answer to.

    However based on what I know about how the system communicates I would say that optimal start - which is an algorithm performed in the controller, not the radiator valve - can only go by the temperature reported to it from the primary (first) radiator controller in the zone, as only one temperature sensor in a zone can ever be bound as the sensor to be displayed for that zone on the controller. (The controller itself ignores other temperature sensors in the zone even though they broadcast their measurement)

    In that case, the first bound radiator controller's measured temperature will be the one that optimal start optimises for. It is trying to get the reported measured temperature to the target on time and will adjust the optimal start period in an attempt to obtain that result.

    In the situation you describe if you were to make the other device the reported sensor for the zone (which you can do by re-binding the temperature sensor role without doing a full rebind of both devices) then you would be in a situation where the slower radiator would consistently fail to reach temperature on schedule and the controller would be unaware of this and therefore not adapt to the situation.

    The slowest warming "room" in a multi-room zone needs to be the one whose temperature is reported to the controller for optimal start to work properly.
    Last edited by DBMandrake; 23rd November 2020 at 03:55 PM.

  3. #3
    Automated Home Sr Member
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    Oct 2020
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    Default

    I think as an experiment I'll swap them over. They are both in the same room so I'm not sure if we'll notice it from a comfort perspective, especially as the biggest difference is in the morning when we are not sitting around.

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