Horstmann 425 to Hive

Discussion in 'Plumbing and Central Heating' started by David Horne, 14 Oct 2021.

  1. David Horne

    David Horne

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    Hello,

    I’ve just moved house and found myself with a Ideal Mexico Super ideal C125 boiler, Horstmann 425 control and Sunvic thermostat. I’d like to replace the control for a hive but need some assistance with the wiring please.
    I’ve attached a couple of pictures.
    Thanks in advance!
    David
     

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  3. stem

    stem

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    This has been asked before, you can find an example that should help you here.

    There should be a diagram on your Sunvic thermostat somewhere; maybe the lid, that shows where the L, N and Switched L wires are terminated. The L and SL need to be bridged / connected and the N isolated safely.

    EDIT
    As you don't describe the type of plumbing the controls are connected to, I forgot to add: If you have a fully pumped system with motorised valves then the Hive is already set for that. Much less common now, but if you have an older system with just pumped central heating & natural (gravity) circulation of hot water, the Hive should be changed to gravity mode. The Hive instructions will tell you how to do this
     
    Last edited: 14 Oct 2021
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  4. David Horne

    David Horne

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    Hi,

    thanks for your reply. I did see that post but I wasn’t too sure what to do within my own thermostat. Linking out L and SL makes perfect sense.
    Thanks again.

    David
     
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  5. stem

    stem

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    Ideally it's best done at the origin of the cable if you know where it is. Note where the individual wires are connected, disconnect the cable, then insert a link between the terminals where the L and SL to the thermostat have just been removed from.

    The old thermostat and its cable can then be removed completely.
     
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  7. David Horne

    David Horne

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    Hi looking into this further, there is only a live and neutral on the thermostat with a resistor.
     

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  8. bernardgreen

    bernardgreen

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    tlm2253.jpg
     
  9. ianmcd

    ianmcd

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    As above you dont have a neutral , you have a live and a swtched live
     
  10. stem

    stem

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    As it is switching a load well under 13A it should have had a neutral connected to terminal 4 as shown in the diagram, so its working accuracy wouldn't have been very good. However as has been said, it's only the L and SL you are interested in. If there was a neutral wire it wouldn't be required anyway .....
     
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