honeywell cm921 wired to worcester bosh 28i

Discussion in 'Electricians' Talk' started by no idea.., Sep 11, 2010.

  1. no idea..

    no idea.. New Member

    Hi, i am trying to set up the honeywell cm921 wireless thermostat to my worcester bosch 28i boiler, but the wiring instructions are confusing, in the receiver i have the connections:
    N,L,L / A,B,C
    in the boiler i have LR,LS,NS,N,L

    so far i have a unswitched spur (fused at 3amp), please can someone guide me from there onwards,
  2. This is Fairly Simple, the combi boiler requires a permanant live which is connection L a neutral N and a earth. ls is live supply lr is live return . other boiler connections should be left. the stat reciever also requires a permanant live neutral earth which is N and L take the permanant suplies from the fused spur , from memory A should be connect to ls on boiler and B LR
  3. no idea..

    no idea.. New Member

    cheers, ill givew that a try.
  4. no idea..

    no idea.. New Member

    tried that but still not successful,it lights up on the reciever(green)but doesnt activate the boiler. when i put it in override or on a time clock.

    any other ideas?
  5. when you put the stat/programmer on constant and turn the stat to 0 does the boiler activate then? if so change the LR wire to C instead of B

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