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Replacing a Satchwell TLX-2356 room thermostat with a Honeywell DT90e

Discussion in 'Electrics UK' started by Spencer1984, 6 Nov 2017.

  1. Spencer1984

    Spencer1984

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    Hi all,

    I'm replacing an old Satchwell (or Sunvic) TLX 2356 mechanical room stat as it only "clicks" on above 25C.

    New stat is a battery powered digital Honeywell DT90e.

    TLX wiring as follows (as I understand it):

    Terminal 1: Demand (or "Switched Live") - Yellow
    Terminal 2: Satisfied - Brown
    Terminal 3: Common - Red
    Terminal 4: Neutral - Blue

    Am I right to wire the new Honeywell stat as follows:

    Terminal A: Common - Red
    Terminal B: Demand - Yellow
    Terminal C: Satisfied - Brown
    Isolate and insulate Neutral - Blue

    HW & CH both heated by a (very) old Vulcan Continental floor-standing boiler, circulator pump, 3-port valves, etc...on a gravity fed system.

    Thanks,

    Spencer
     
  2. flameport

    flameport

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    Correct, but it is very unusual to have a system which requires 'satisfied' as in the brown wire.

    Is the brown wire separate, or part of the same cable as the other 3? Is it bare copper?
     
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  4. Spencer1984

    Spencer1984

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    The system is very old and a bit mis-matched. 13 rads in a 3-bed semi...half on 15mm, half still on microbore and I believe Vulcan actually stopped making the boiler before I was even born! So I'm not surprised the system is "unusual" in needing a satisfied line!

    I'll need to double-check the satisfied to see if it's part of the same cable as the others or not. From memory, it's brown-sleeved and definitely not bare copper. I'll try and upload some pics too...
     
  5. Spencer1984

    Spencer1984

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    Ok, so this is the old Satchwell on the wall with the dial removed to show the wiring instructions...

    [​IMG]


    Plastic cover removed to expose actual wiring...

    [​IMG]
    "Brown" wire is actually more black in colour and is a separate cable from the other 3 colours.


    But the plot thickens! The 3 colour cable is actually a 4-wire cable, as when I've loosened the stat away from the wall, I've revealed an additional bare-copper wire which is attached to (what I presume is) an earth at the back of the thermostat...

    [​IMG]
    Not a great pic, but you get the gist.

    So now I'm thinking my original wiring plan was correct, but I know have to isolate and insulate the bare-copper "earth" as well the blue neutral?
     
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  7. Echo the husky

    Echo the husky

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