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Thread: Underfloor heating with Evohome

  1. #21
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    Found some additional info on that little box bottom-left in the image. It has three main functions:
    1. it will shut down the motor when the input temperature is lower than inside the UFH (so there is no cooling after the main thermostat shuts down the boiler)
    2. it will shut down the motor when the UFH temperature reaches a set limit
    3. when the motor is switched off it will still run it for a few minutes every two days to prevent it becoming stuck

  2. #22
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    Thanks for gathering this info Gordon, very useful. Are you running this via an Evohome? From your initial description I was taking the electronics to mean a management centre such as the Honeywell ufh controller... Rather than an additional piece of hardware, which this looks like, below the motor...

  3. #23
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    Quote Originally Posted by 1animal1 View Post
    Thanks for gathering this info Gordon, very useful. Are you running this via an Evohome? From your initial description I was taking the electronics to mean a management centre such as the Honeywell ufh controller... Rather than an additional piece of hardware, which this looks like, below the motor...
    Well, yes and no. I have a loose HR92 lying in a cupboard that is configured in the Evohome controller to operate the UFH, so if I turn up the temperature in the living room there will be a heat demand and the BDR91 will open the main valve to the city heating (i.e. fire up the boiler). Since currently there is no actual Evohome controlled valve towards the UFH the heating will also be on in the living room if any other zone generates a heat demand.

  4. #24
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    Bear with me on this. If the UFH is controlled by the BDR, then surely the pump will only be running ad hoc throughout the day, therefore negating the protection and constant 'on' time causing the high electric bills. My thought is that the Honeywell will cycle it at least one every couple of hours.... Unless I'm completely off the point here? I am still at the research phase so open to being shot down

  5. #25
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    Quote Originally Posted by 1animal1 View Post
    Bear with me on this. If the UFH is controlled by the BDR, then surely the pump will only be running ad hoc throughout the day, therefore negating the protection and constant 'on' time causing the high electric bills. My thought is that the Honeywell will cycle it at least one every couple of hours.... Unless I'm completely off the point here? I am still at the research phase so open to being shot down
    Ehhh... yes. If you use a BDR to control the UFH pump then you will automatically save on your electricity bill. This comes with the risk that the pump may no longer function if the heating has been off for an extended period of time, so you should have a secondary method for letting the pump run periodically. At say 3 minutes every 2 days a 60W pump will use 1kWh per year, which is seriously little money compared to needing to buy a new pump.

  6. #26
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    Thanks Gordon, that makes sense. I wonder if the Honeywell controller has any such function or whether it can be added as an addition...

  7. #27
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    Hi Gordon, update on this.... Still designing my system and collating the equipment.

    In the interim...

    Your point on the protection mechanism has had me thinking and searching for a similar solution - it then hit me, with the Evohome, I can simply set the system to cycle for a few minutes when ever I like, via the electronic programming! For info, Honeywell have also confirmed that their ufh controller does this automatically every 24 hours too, although I can't see any reference to this anywhere, so remain sceptical.

  8. #28
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    Going off the original theory of this thread. I have a slightly different set up, can someone confirm it'll work?

    I will be going for a single zone at the start using a BDR91. However together with this, because I'm using OT, the zone valve will be always open, therefore cannot be wired into the BDR along with the pump. Question is, can the pump and a thermal actuator 230v be wired into the BDR to control the flow on and off

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