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Combi boiler, thermostat swap and wiring

Discussion in 'Plumbing and Central Heating' started by trickymicky69, 8 Apr 2018.

  1. trickymicky69

    trickymicky69

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    Hi,

    In my current CH set up I have a combi boiler in the garage, with a manual dial type timer attached to the combi.

    Currently I set the timer to constantly on, with the thermostat in the hallway controlling the temperature (don't use the timer at all) .

    I would like to swap the thermostat with a digital one as the analogue one is very slow to respond, looks old fashioned and cannot be programmed.

    So basically I would like to swap it for a programmable one if poss.

    I have taken a picture of the wiring from behind the faceplate, but terminology is confusing me.

    I have three wires including an earth, so would that count as a three wire or two wire?

    If you could recommend a basic programmable thermostat that would straight swap I could get my plumber to do it when he services our boiler

    Picture of wiring attached

    Thanks

    Mike
     

    Attached Files:

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  3. muggles

    muggles

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    Yours is a 2 wire, but a 3 wire would be an upgrade . What make/model boiler do you have?
     
  4. Jajodu

    Jajodu

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    Honeywell CM927 would work.
     
  5. trickymicky69

    trickymicky69

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    Thank you for your replies
    It's a main eco 25 combi
     
  6. gas112

    gas112

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    if you dont want to mess with the wiring a honeywell 901 will fit straight onto the two wires (snip earth) and just leave clock already on boiler at constant
     
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  8. trickymicky69

    trickymicky69

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    Hi,
    I can get a Honeywell CM907 from my local supplier but it says "volt free connections" would this still be suitable with my current wiring?
    Many thanks
    Mike
     
  9. JohnD

    JohnD

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  10. stem

    stem

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    Yes, the CM900 range will be fine. Your current thermostat has volt free connections. (The voltage comes from the wires that are attached to it.) So simply put the brown wire in A and the blue wire in B as below and insulate / isolate the earth. Ideally the blue wire should have a brown sleeve on it to identify it as a live.

    Capture.JPG

    Insulate / isolate the earth and tuck it our of the way. As Gas121 said the existing time control will need to be set to be permanently 'on' to stop it overriding the new programmable thermostat.
     
  11. Jajodu

    Jajodu

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    That's fine. It's basically just a switch with a timer and different temperatures. Set your existing timer to constant on and use the 907 for everything. Enable optimum start while you're programming it.
     
  12. trickymicky69

    trickymicky69

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    Perfect thanks guys
     
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