wiring of honeywell cm900 roomstat

Discussion in 'Electricians' Talk' started by Gman34, Nov 29, 2015.

  1. Gman34

    Gman34 Member

    im trying to wire one of these up to a combi boiler
    fused spur next to boiler taken feed into receiver and then flex up to boiler
    boiler has l n e and switch live

    receiver has n l l a b c

    boiler on there drawing has n l t1 t2

    they have linked t1 to a
    t2 to B

    They show a link between l and l
    i only have one switch live
    im guessing i need to also link from L to A (is t1 a perm live )
    then put the switch live into B (t2)

    on their instructions they also show a direct burner control diagram where L and L are linked and also linked to A
    then the burner switch live goes into B
    https://www.google.co.uk/webhp?sour...=UTF-8#q=wiring honeywell wireless thermostat
    in the above link the diagram can be found in the first link
     
  2. Gman34

    Gman34 Member

    ok i will unplug it from the boiler and see if the switch live becomes live when connected in this way then i will know this forum doesnt get much of a response these days lol
     
  3. Jitender

    Jitender Screwfix Select

    Is this the wireless version with the BDR91 relay box?
     
  4. Gman34

    Gman34 Member

  5. Gman34

    Gman34 Member

    im guessing wire it as per the direct burner diagram
     
  6. Jitender

    Jitender Screwfix Select

    You need to wire it as it is shown for a combi Boiler.

    T1 = Permanent Live

    T2 = Switched live

    If you only have a switched live at the boiler.

    Then as you mention you need to link in the Relay Box (BDR91) L to A.

    The link L to L is an internal link so you dont need to link again.

    What is the make and model of the boiler?
     
  7. Jitender

    Jitender Screwfix Select

    It should look something like this:


    Comi Boiler - CM927.jpg

    It would be easier to wire in 3 core cable 1mm, as the terminals in the relay box struggle to take any larger.

    You can take the 3 core supply from the boiler terminal, just put brown insulation on the earth wire to indicate that it will be switched live.
     
  8. Jitender

    Jitender Screwfix Select

    Plus you will only need to run one length of flex, if the supply is taken from the combi boiler terminal block. Most manufactures accommodate this.
     
  9. DNR Plumbing

    DNR Plumbing Active Member

    Don't use an earth wire as a switched live you can buy twin red cable for switches and 4 core wire for just this purpose,
    I don't mind the odd neutral taped as a live but never an earth
     
  10. Jitender

    Jitender Screwfix Select

    Insulation tape isn't a good idea as I mentioned earlier, brown sleeving is better, as the tape can sometimes come off.
     
  11. Gman34

    Gman34 Member

    Hey thats exactly how i connected it i used 1mm solid stripped from t&e for my links and of course i used brown and blue sleeving and 4 core flex up to the boiler lol come on i am a spark :) Jitinder nice drawing did you do that?
     
  12. Gman34

    Gman34 Member

    was a glow worm and i wired it at 5:40am in the morning lol :) Im going to keep that drawing though it makes it allot easier to remember thanks .
    I had figured it though too
    why dont honeywell say combi boiler on their drawing on the direct burner one they show in instructions

    On glow worm boiler also had to remove the 24v switch link
     
  13. Gman34

    Gman34 Member

    i only linked it between l and l as their is no continuity between the two without a link .
     

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