Thermostat replacement - help please

Discussion in 'Plumbing and Central Heating' started by Hazelcrockey, 21 Nov 2021.

  1. Hazelcrockey

    Hazelcrockey

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    Hi, I'd be really grateful if someone could help with this. I bought a Danfoss TPone-B to replace a very old dial thermostat. Thought it would be simple but I was wrong. Boiler is and Oil, Worcester Greenstar Heatslave II recently installed by previous house owner

    The existing Drayton thermostat is wired into the switched socket supplying the boiler. Three terminals are used in the thermostat - N (blue wire) L (brown wire) and CALL (black wire).

    The new Danfoss has COM (COM), OFF (NC) and ON (NO)

    Can anyone confirm which terminals I need to use on the Danfoss please. Given that it battery powered and I think the old one required mains I am reluctant to use trial and error on this.

    The cable to the boiler has 5 cores, the usual 3 plus black (fed to thermostat CALL) and grey (fed to thermostat L). When the double pole switch feeding the boiler is on there is 250v at the live (L) terminal in the thermostat

    I've tried pasting images but they aren't showing for some reason

    Any advice on this would be appreciated

    Many thanks in advance
     
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  3. ianmcd

    ianmcd

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    Bottom right hand side, there is a button "upload a file " click that and add your photos , your post makes as much sense as my wife trying to order from a menu :rolleyes::rolleyes::rolleyes::rolleyes:
     
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  4. Hazelcrockey

    Hazelcrockey

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    Thanks for your reply Ian. I tried that but all I get is an error message despite having reduced the image size to a couple of hundred bytes.

    To simplify. I have an old Drayton thermostat controlling a new Worcester Heatslave II boiler. I bought a Danfoss TPOne-B to replace it. The Drayton has three wires, wired into N, L and CALL. Which terminals do these relate to on the new Danfoss? I have a choice of COM, NC or NO. I know from Googling that the neutral is probably redundant for my battery powered Danfoss but not sure which terminals to use.

    Thanks
     
  5. CBW

    CBW

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    I’d go for L into Com and call into NO, NC not needed and terminate neutral wire safely in a connector block.
     
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  6. MeldrewsMate

    MeldrewsMate

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    Grey is your live feed to the 'stat; connect it to Danfoss COM.
    Black is your CALL from the 'stat; connect it to Danfoss NO.
    Disconnect and make safe the L, N, and E that are not required for a battery operated device.
     
  7. Hazelcrockey

    Hazelcrockey

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    Thanks all for the responses. I'm now confident I can do this without destroying the new thermostat or my boiler
     
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