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Help please - simple wiring question Hive dual channel on combi boiler

Discussion in 'Electrics UK' started by W1ldstallion, 9 Jan 2019.

  1. W1ldstallion

    W1ldstallion

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    Hi,

    I bought a hive dual channel (heating AND hot water) in the sales, but I have a combi boiler (Valiant EcoTec Plus831) so don't need the hot water option.

    My problem is that I'm not sure which way to hook up the heating on/off wires to the new Hive thermostat.

    The existing thermostat is a Honeywell CM900, wired like this:
    Honeywell thermostat.jpg

    Using the Hive diagram
    Hive wiring diagram.jpg

    I have wired up the thermostat like this:
    Hive wiring.jpg

    Does this make sense? I wasn't sure if the black or the grey should go to heating on, and whether a connection to heating off was needed.

    Thanks in advance for any advice!!
     
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  3. flameport

    flameport

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    Your wiring is wrong.
    Before connecting anything, you need to find out where the black and grey wires are connected in the boiler.

    The dual Hive may not be suitable, and even if it is, guessing will most likely result in things being destroyed.
     
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  4. W1ldstallion

    W1ldstallion

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    Thanks for the response flameport, how can you be sure that it is wrong?
     
  5. flameport

    flameport

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    You have wires to both heating on and heating off.
     
  6. W1ldstallion

    W1ldstallion

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    So I should only have one wire connected to heating on? What should the other wire be connected to?

    Thanks
     
  7. bernardgreen

    bernardgreen

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    The dual and single are NOT the same.

    The single channel unit does NOT put Live ( 230 volts ) onto the terminals that connect to the boiler.

    The dual channel unit DOES put Live ( 230 volts ) onto the terminals that connect to the boiler.

    0x56.jpg
     
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  8. W1ldstallion

    W1ldstallion

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    Ok thanks Bernard. I guess I will try and return the dual channel hive and replace it with the single channel.

    Once I have the single channel thermostat, which terminals (1-4) should I attach the grey and black wires (A/B) to?

    Thanks
     
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  10. bernardgreen

    bernardgreen

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    Terminals 1 and 3 on the SINGLE channel receiver if the boiler requires Volt Free contacts. But check with the boilers instructions as to the mode the boiler works in ( Volt Free or Switched Live )
     
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  11. ericmark

    ericmark

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    Looking at the instructions page 32 it seems there are three options for the thermostat, 24 V DC room thermostat which would normally be placed in a cool down stairs room with no alternative heating or outside door to switch off heating on warm days, also there is Bus connection (Controller/room th. digital) this is the preferred option, instead of switching boiler off/on it turns it up/down so the room stays at an even temperature.

    The VRT 50 – Room Thermostat eBUS costs around £45 it does not make sense to fit a more expensive model without eBUS, I think NEST 3 has OpenTherm with eBUS, also EvoHome have a version with OpenTherm, but Hive does not it seems have the option, so not really suitable for your boiler.
     
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  12. SimonH2

    SimonH2

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    Looking at the instructions Ericmark linked to ...
    DO NOT power up the system as you'd connected it - this is almost certain to destroy the controller board in the boiler. The connections for the thermostat need what is termed "volt free" switching - this means that the external switch simply makes or breaks the connection but does not impose any voltage on it. In this case, the boiler uses an internal extra low voltage (24V) for control and this is unikely to be fully protected* against "misconnections". The dual channel device you have puts the full mains voltage onto the switched outputs which will blow the board in your boiler.

    This is why it's not enough to just look at how the existing stat is connected. You have to look at how the other end is connected AND the manuals for both the boiler and the new stat/controller to ensure that they are compatible.

    * Personally, If I were desiging such a device I'd at least attempt to make the circuits such that permanent damage wouldn't result from stuffing mains up the connections - and TBH it wouldn't be all that hard. But in these days when they want to shave every last ½d off the price ...
     
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  13. SimonH2

    SimonH2

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    Also, DO NOT power up the system with the stat/controller removed from the terminal plate. There's lots of exposed bits of metal there, some (or at least one) of which will be live whenever the system is powered up. You don't want to risk someone inquisitively sticking their finger in :eek:
     
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  14. W1ldstallion

    W1ldstallion

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    Thanks for the advice all. I'll steer well clear of this.

    I think I'll be replacing it with a Nest system, they have better features anyway!
     
  15. ericmark

    ericmark

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    Nest 3 seems to connect with Energenie MiHome TRV heads, so you can extend the system. However I have not tried using the follow commands, so not a clue how in real life they work.

    I also have never tried direct connection to the bus, all the reports say connection to the bus is better, however never tried it.
     
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