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Replacing Drayton Digistat SCR with Honeywell BDR91

Discussion in 'Plumbing and Central Heating' started by DaPanda, 11 Dec 2017.

  1. DaPanda

    DaPanda

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    Hi, I'm looking to replace my current Drayton Digistat SCR with a Honeywell system. The wiring on my SCR is:

    N - Blue (1st cable)
    L - Brown (1st cable)
    1 - Blue (2nd cable)
    2
    3 - Brown (2nd cable)
    4

    [​IMG]

    What should the wiring for the Honeywell BDR91 unit be? Should it be:

    N - Blue (1st cable)
    L - Brown (1st cable)
    L

    A - Blue (2nd cable)
    B - Brown (2nd cable)
    C

    Should I also connect the 2nd L connector to the 1st L one?

    I'll get to it only in the new year as I don't have the time to order a Honeywell system before going on holidays, but I'd like to figure out exactly what I'll need to do.
     
  2. stem

    stem

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    You have pretty much worked it out, so I can confirm as follows:

    N - Blue (1st cable) - This goes to the BDR (N)
    L - Brown (1st cable) - This goes to one of the BDR (L) terminals (doesn't matter which one, they are both connected together internally)
    1 - Blue (2nd cable) - This goes to the BDR (A) terminal
    2
    3 - Brown (2nd cable) - This goes to the BDR (B) terminal
    4
     
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  4. D_Hailsham

    D_Hailsham

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    I hope you are not thinking of keeping the Drayton Digistat+RF and replacing the SCR with a BDR91. It will not work.

    Main reason: the SCR is 433MHz; BDR91 is 868MHz.

    PS Why wasn't this added to your original "neighbour" topic?
     
  5. DaPanda

    DaPanda

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    Thank you very much.

    No. I was thinking of replacing both units. The BDR91 and CM927 seem to have good reviews and go for cheap on ebay. (Though I'll delay the replacement as Drayton has offered to send me another thermostat, so I'll test that first.)

    Because it is a different topic! This question is of potential interest to many (who likely have little interest in my other thread). It would even be helpful for moderators to collect all these basic wiring questions in a sticky thread/FAQ. I searched for a previous question/answer addressing this replacement and couldn't find any. As both these two systems are common, replacing one with the other must be a common occurrence and this thread may be helpful to others.
     
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