Mechanical to digital thermostat

Discussion in 'Plumbers' Talk' started by rizla13, Sep 11, 2019.

  1. rizla13

    rizla13 New Member

    I have a old honeywell t40 mechanical thermostat
    I want to change it to a new digital honeywell dt90e

    Can someone please help with wiring.
    I have uploaded the old wiring
    Currently its wired up as follows
    Earth to earth
    Blue -2
    Yellow-3
    Red-1

    How would i wire it up to dt90e. I have attached a wiring diagram of the dt90e which is the last picture

    Thanks
     

    Attached Files:

    Last edited: Sep 11, 2019
  2. Mike83

    Mike83 Well-Known Member

    Old stat red to new stat A.
    Old stat yellow to new stat B.
    The neutral will need safely terminated.
     
  3. rizla13

    rizla13 New Member

    I was waiting for you to reply mike
    I was trying to pm you the. Found out they have stopped the pm function

    I take it neutral is blue? Thats needs terminating?

    What about earth? Do i terminate it or just leave it tucked away?
     
    Last edited: Sep 11, 2019
  4. Mike83

    Mike83 Well-Known Member

    Yes blue neutral needs terminating.
    Is there space on the new stat for an earth?
     
  5. rizla13

    rizla13 New Member

    I don’t think there is
    I have attached a pic of the wiring diagram of the new stat in my 1st post.
     
  6. rizla13

    rizla13 New Member

    This is what i got from honeywell website
     

    Attached Files:

  7. MGW

    MGW Well-Known Member

    I would if room permits use a block connector, if not bend over wires so no possibility of copper sticking out of end and use insulation tape.
     
  8. rizla13

    rizla13 New Member

    Would that be for both blue and earth wires?
     
  9. The Teach

    The Teach Well-Known Member

  10. rizla13

    rizla13 New Member

  11. The Teach

    The Teach Well-Known Member

    have a look at the thermostat backplate,the square cable access area.

    The not required wires can be independently terminated in a 3amp 2 block terminal strip some trimming of the block connector with a Stanley knife helps. carefully situate it in the cable access area. Sometimes taking a few mm out of the wall in the cable access area will assist accommodating the connector block.

    There are always other ways of doing jobs,others will have other ideas :)
     
  12. rizla13

    rizla13 New Member

    Ok thanks much appreciated

    So just to clarify wiring into honeywell dt90e

    Red(live) goes into A
    Yellow (switched live) goes into B
    Blue (neutral)into terminal block
    Earth into terminal block?
     
  13. Mike83

    Mike83 Well-Known Member

    The wiring will be correct.
     

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