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Thread: EvoHome - adding HW kit to combi boiler

  1. #1
    Automated Home Jr Member
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    Default EvoHome - adding HW kit to combi boiler

    Hi

    I've currently got EvoHome setup with just radiator / heating control, with hot water controlled by the built in timer on our Worcester oil fired boiler. The battery has packed up on the WB timer, so every time we have a power cut it reverts to defaults and we get heat / hot water at random times.

    I'm looking to add HW control to the EvoHome, and therefore do away with the built in timer entirely. As it's a combi type boiler, I don't need the hot water temperature controls, really all I need is the boiler relay on/off at set times functionality - so most of the bits that come in the hot water kit don't appear to be needed, just the BDR-91.

    Can I get away with just buying an additional BDR-91, or do I have to buy the HW kit (at double the price!) for some of the other components?

    Thanks!

    Jon

  2. #2
    Automated Home Ninja Dan_Robinson's Avatar
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    This won't work.

  3. #3
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    So the only option is to buy the full HW kit?

  4. #4
    Automated Home Legend top brake's Avatar
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    Quote Originally Posted by jonn View Post
    Hi

    I've currently got EvoHome setup with just radiator / heating control, with hot water controlled by the built in timer on our Worcester oil fired boiler. The battery has packed up on the WB timer, so every time we have a power cut it reverts to defaults and we get heat / hot water at random times.

    I'm looking to add HW control to the EvoHome, and therefore do away with the built in timer entirely. As it's a combi type boiler, I don't need the hot water temperature controls, really all I need is the boiler relay on/off at set times functionality - so most of the bits that come in the hot water kit don't appear to be needed, just the BDR-91.

    Can I get away with just buying an additional BDR-91, or do I have to buy the HW kit (at double the price!) for some of the other components?

    Thanks!

    Jon
    the hot water kit is for control of vented or unvented hot water cylinders

    Not possible to use this on a combi boiler
    I work for Resideo, posts are personal and my own views.

  5. #5
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    Quote Originally Posted by top brake View Post
    the hot water kit is for control of vented or unvented hot water cylinders

    Not possible to use this on a combi boiler
    Is there any solution? I would have thought turning a BDR-91 on and off on a HW schedule would be easy to implement...

  6. #6
    Automated Home Legend paulockenden's Avatar
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    I wonder whether adding the DHW kit but leaving the temp sensor in free air would work. In theory it should leave the hot water relay open permanently during the scheduled hours.

    Expensive way to do it though. Also, I can't understand why, if your boiler works in a combi-like way (i.e. hot hater heated on demand) you'd even want to put it on a timer?

    P.

  7. #7
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    Quote Originally Posted by paulockenden View Post
    I wonder whether adding the DHW kit but leaving the temp sensor in free air would work. In theory it should leave the hot water relay open permanently during the scheduled hours.

    Expensive way to do it though. Also, I can't understand why, if your boiler works in a combi-like way (i.e. hot hater heated on demand) you'd even want to put it on a timer?

    P.
    It's sort of like a combi - there's a small tank inside the boiler which is kept up to temperature when the DHW is turned on, but as soon as you open up a hot tap the boiler kicks in like a combi would, so the water isn't truly heated on demand. If you leave the DHW turned on all the time it will fire every now and then to keep the small tank up to temperature.

    I'll have a think about what you say about the DHW sensor left in free air - while the hot water kit is 80 vs. 40 for a BDR, it's not that much more than an external programmer would be...

  8. #8
    Automated Home Legend paulockenden's Avatar
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    The advantage over an external timer is that you'd have app-based control, too.

    The only bummer would be if Honeywell added functionality which noticed that the HW temp wasn't rising and raised an alarm.

    P.

  9. #9
    Site Sponsor The EVOHOME Shop's Avatar
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    I have done this on a Worcester Heatslave in the past and do a simailar thing on my buffer cylinder at home... Its not a recognised Honeywell application, but you could get this to work (but you will need the HW Kit).

  10. #10
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    Does the HW kit have any equivalent of frost protection that might kick in if the temperature sensor shows a value of less that a certain amount.

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