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Honeywell T45 to Drayton wiser 2 channel

Discussion in 'Plumbing and Central Heating' started by MrBishop, 15 Sep 2021.

  1. MrBishop

    MrBishop

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    Hello,

    My Honeywell T45 has stopped working and so I thought I'd replace it with a smart device. I have bought a Drayton Wiser unit and need to wire it in. Can anyone advise on how the wiring should go please?!
    Additional info: I have a conventional Baxi boiler with a pressurised water tank. 2 valve (HW and CH) and there is a pump (which i replaced recently when the previous one died)
    The house doesn't have a thermostat and I won't want to add one other than the TRV units.

    I am happy to rewire the unit and install the new one, but just can't make head nor tail of the diagrams I have seen.
     
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  3. oldbutnotdead

    oldbutnotdead

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    Which Wiser did you buy- the WT724R?
    One irritant with the Wiser is that the common contact on both HW and CH is tied to 240v rather than being volt free. Do you have a multimeter- if so, check on your existing backplate that there is 240v between pin 8 and N and also between pin 5 and N.
    Provided there is, it's a simple swap.
    L goes to L on the Wiser.
    N goes to N.
    8 and 5 are redundant. Mark and make safe (terminal block) or remove if they're links to L.
    6 (Honeywell) goes to 3 (wiser)
    3 (Honeywell) goes to 4 (wiser)
    You'll need to bridge out and remove any existing room thermostat (presumably you're using the room stat that comes with the hub) or just set the old one to 30 degrees.
    Cylinder stat will still function.
    Done.
     
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  4. CBW

    CBW

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    The Honeywell states on the white sticker, that a supply of 220-240ac is required, I’m guessing it won’t work without. Also OP states no existing thermostat? Although, I think the Wiser will have one built in.
     
  5. oldbutnotdead

    oldbutnotdead

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    Yes the controller runs on 240v but the control relays are volt free....much more flexible but a potential beartrap when swapping out for the Wiser
     
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  6. MrBishop

    MrBishop

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    So I've finally built up courage to have a go at this after much procrastination...

    My multi meter shows 8 and N as being 240v but 5 and N being zero.

    I knew it wouldn't be straightforward!
     
  7. CBW

    CBW

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    Did the heating work? If so, then could just be wired differently?
     
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  9. MrBishop

    MrBishop

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    Yes. To clarify I've only checked the volts as suggested - on the basis if that info was correct for mine then I'd have a go. It wasn't so the old unit is still in place and I'm back to pondering...
     
  10. CBW

    CBW

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    You won’t know unless you swap it though :)
     
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  11. MrBishop

    MrBishop

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    So I've installed it and thermostat etc.

    Now.... when I tell it to turn on heating you can hear it click etc and it's as if boiler wants to fire up but then the pump etc don't kick in.

    Any ideas?

    The Old honeywell has a link wire from live to heating com and hot water com.

    I followed the instructions above and all seemed perfect. Just not getting the pump etc firing
     
  12. CBW

    CBW

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    Does the hot water work?
     
  13. MrBishop

    MrBishop

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    It works!!! Oh wow. I've done a thing!!

    Thank you @oldbutnotdead for the initial instructions and also to you @CBW for your continued support today. Greatly appreciated

    Thank you!

    (Now I just need to remortgage to buy all the extra trv thermostats to save a fortune on my energy )
     
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  14. oldbutnotdead

    oldbutnotdead

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    Excellent. Yeah the TRV heads aren't cheap, I've been buying them when I see offers on (amazon had a good one over Easter, saved about £15/head)
    Things to watch- does your boiler have an Opentherm control input- if yes then the Wiser you have can control the boiler more subtely than turning it on and off. If your boiler doesn't modulate you may find it cycling on and off it only 1 or 2 rads are calling for heat.
    The WiFi TRVs are a bit of an all or nothing- once you start scheduling individual rads to call for heat on their own timetable, any non-WiFi rad will also get heat (until their manual TRV reaches setpoint).
     
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