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Thread: Evohome DIY install check

  1. #1
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    Default Evohome DIY install check

    Sorry....yet another diy install thread for evohome. I think I have been thinking too much about it and have got myself confused so any help is much appreciated.

    We have moved to a victorian house which currently has 2 single zone Honeywell wireless thermostats installed linked to 2 BDR relay box which control the 2 zone valves (upstairs and downstairs).
    Our hot water is provided by a Vitodens 100W 26kw boiler and an unvented system. There is a zone valve for the hot water which is controlled by a Channel H37XL controller (2 CH and 1 HW).
    We have some rooms which are being heated during the day - and do not need to be - so I wanted to install some TRV's to do this - hence evohome.
    I have ordered an essential kit (Evohome controller, BDR1 and 6 TRV's alongside a hot water kit). I will get more TRV's over time.

    When I install evohome I assume I can replace the Channel H37XL with the BDR1 relay, and then reprogram the 2 CH zones BDR relays to be controlled by the Evohome controller?
    Or does the BDR1 evohome relay control the HW and both CH zones?
    Where does the HW kit fit into this - I was going to install the thermostat in place of the current one on the boiler, and then wire the controller and valve into the system.

    Is this correct or should I just leave the Channel H37XL in place, turn it to be permanently on, and then ignore the BDR1 that comes with the evohome kit and just install the hot water kit?

    When/if I remove the current Channel H37XL controller, which wires (L,N etc) do I connect as I believe I would need to make this be permanently on?

    As you can see I have really confused myself.....

    Thanks in advance

  2. #2
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    Quote Originally Posted by blobbi View Post
    Sorry....yet another diy install thread for evohome. I think I have been thinking too much about it and have got myself confused so any help is much appreciated.

    We have moved to a victorian house which currently has 2 single zone Honeywell wireless thermostats installed linked to 2 BDR relay box which control the 2 zone valves (upstairs and downstairs).
    Our hot water is provided by a Vitodens 100W 26kw boiler and an unvented system. There is a zone valve for the hot water which is controlled by a Channel H37XL controller (2 CH and 1 HW).
    We have some rooms which are being heated during the day - and do not need to be - so I wanted to install some TRV's to do this - hence evohome.
    I have ordered an essential kit (Evohome controller, BDR1 and 6 TRV's alongside a hot water kit). I will get more TRV's over time.

    When I install evohome I assume I can replace the Channel H37XL with the BDR1 relay, and then reprogram the 2 CH zones BDR relays to be controlled by the Evohome controller?
    Or does the BDR1 evohome relay control the HW and both CH zones?
    If the existing BDR relays are BDR91's then you can just clear the bindings on them and then bind them to your evohome, and depending on the model of the thermostats (Y87RF ?) you may be able to repurpose those as temperature sensors for zones as well.

    I'm going to assume your zone valves' microswitches fire the boiler and that you want to leave it that way. If so the set up is pretty easy.

    Assuming you choose to have evohome control the hot water as well, bind both heating zone valves (upstairs/downstairs) as heating relays - if you use hot water control this is done in the stored hot water settings where you can bind hot water temperature sensor, heating zone valve(s) and hot water zone valve.

    You have the option to bind more than one relay to the heating zone valve function - this will cause both heating zone valves to open and close together and allows the zoning to be performed by the HR92's instead. Wire one of your new BDR91's in place of the Channel H37XL to control the hot water zone valve.

    It sounds like you may have a BDR91 left over if you can re-use both of the original BDR's, in which case you could choose to use a boiler control relay - if you do that, bind it to the "appliance control" or "boiler control" function (depending on firmware version) and wire this directly to the boiler, removing the connection to the zone valve microswitches.

    Where does the HW kit fit into this - I was going to install the thermostat in place of the current one on the boiler, and then wire the controller and valve into the system.

    Is this correct or should I just leave the Channel H37XL in place, turn it to be permanently on, and then ignore the BDR1 that comes with the evohome kit and just install the hot water kit?
    Hot water control in Evohome requires both the sensor and a BDR91 - you can't make it work by ignoring the BDR91. You would replace the sensor for the Channel controller and remove it.

    If you have a sealed (unvented) hot water cylinder you will also have a separate protective high limit stat - this must NOT be removed, it must be kept installed and be connected in series with the relay contacts of the BDR91 to prevent cylinder temperature going dangerously high if the Evohome hot water control malfunctions.

    If you have a vented cylinder you can probably get away without a separate high limit stat. (I don't have one on my vented cylinder)

    When/if I remove the current Channel H37XL controller, which wires (L,N etc) do I connect as I believe I would need to make this be permanently on?

    As you can see I have really confused myself.....
    A BDR91 needs permanent live and neutral, you then usually link the live across to the A contact and the B contact goes to the live input on the zone valve.

    Check the example circuit diagram for S-Plan that comes with Evohome documentation.

  3. #3
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    Amazing! Thanks so much thatís super helpful

    Your assumptions are spot on. Can I ask....

    What is the benefit of a boiler relay switch?

    It sounds like the system works best if you have both zones firing and the trvís controlling the temp. I donít have enough at present for the whole house, can you maintain a hybrid system where the evohome knows which zone valve goes to which TRV, and also continue to use the Y87RFís?
    Last edited by blobbi; 30th January 2021 at 10:55 PM.

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    One suggestion, although you have probably got it working now, if you have DHW coming from a tank bind the BDR91 and set that up first, then set up the second BDR91 for the CH. The installation manual does say that (well it did last time I looked) but it is not obvious that is the order of things.

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    Not installed yet, it arrives over the next couple of days.
    I had another look at the boiler - its actually unvented, I was confused by some old tanks in the attic - the bit I worry about is the HW control which I think I should easily be able to take out the old thermostat, put the new one in, wire up the remote sensor for it and then take out the old CH/HW controller, bypass the CH wires and hook up the HW with a BDR1. I have a fair idea of what to do ��

    I am still not sure what the benefit of using the extra BDR1 as a boiler relay switch is?

    Thanks for the help

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    Two relays. One is for the heating system the other for the hot water as the sensor connects to the latter to tell it when the temperature has dropped and the boiler needs to fire up. Make sure you keep them all at least 30cms apart when installing.

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    Ok, so I've come up against an issue with wiring.
    As stated above - the original system was a ChannelPlus37XL attached to a Viessman 100W boiler controlled by 2 Y87RF Thermostats each controlling a zone (upstairs and downstairs)
    I now appreciate that you can't really have a hybrid system and so have combined the CH zones so that they are linked as the Wireless controller and I have HR91's on most of the radiators (I need to buy some more!)

    The HW though I cannot for the life of me work out the wiring. I removed the ChannelPlus and it was like this (E N L 1-6 as per the guidance https://www.tlc-direct.co.uk/Technic...nn/H37XL_I.PDF)

    Attachment 1768

    The issues I have are:
    1. I wired up the BDR1 and HW sensor, linked them both to the controller but it would not fire the boiler. I followed the wiring for an SPlan in the documentation but still no luck. Any Idea which wires go where?
    2. I wonder if when I disconnect the thermostat connected directly to the boiler if I need to again create a link to complete a circuit, this is currently hard wired in via a boile?
    3. I am unsure how to connect the CH wires to bypass the controller. The CH is set up and working now when I turn the ChannelPlus on all the time, I just need them to work when I disconnect the wires.

    I appreciate that this is a DIY install and I could get someone in to do it, but I am trying to work it out myself

    Thanks in advance

  8. #8
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    I rely on greater expertise to step in here but the BDR91 is the link that replaces the thermostat in the sense that the actual thermostat or HR92 sends a message to the Control Panel that it needs heat, the Panel then tells the BDR91 and it then instructs the boiler by closing the circuit that is linked to the standard thermostat connection in the boiler. My current boiler’s connection, other than mains power, is no more than to where the old original, pre Evohome hall thermostat used to connect.

    With my new boiler to be installed I don’t have a BDR91 it being replaced with the OpenTherm Bridge. If I used a BDR91 it would be wired into the thermostat connection on the boiler. With the OpenTherm Bridge there is a designated point to wire it in and it seems it picks up low voltage power from the boiler as, unlike the BDR91 it is not connected to the mains. That means at first sight having the bridge in the same area as the boiler but my thinking is that as there is an existing connection at present connected to the thermostat point from my airing cupboard to the boiler I may put the Bridge in the airing cupboard and pick up the old otherwise redundant thermostat cable and use it to connect to the OpenTherm point. All then neatly out of sight.

  9. #9
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    Quote Originally Posted by blobbi View Post
    Ok, so I've come up against an issue with wiring.
    As stated above - the original system was a ChannelPlus37XL attached to a Viessman 100W boiler controlled by 2 Y87RF Thermostats each controlling a zone (upstairs and downstairs)
    I now appreciate that you can't really have a hybrid system and so have combined the CH zones so that they are linked as the Wireless controller and I have HR91's on most of the radiators (I need to buy some more!)

    The HW though I cannot for the life of me work out the wiring. I removed the ChannelPlus and it was like this (E N L 1-6 as per the guidance https://www.tlc-direct.co.uk/Technic...nn/H37XL_I.PDF)

    Attachment 1768

    The issues I have are:
    1. I wired up the BDR1 and HW sensor, linked them both to the controller but it would not fire the boiler. I followed the wiring for an SPlan in the documentation but still no luck. Any Idea which wires go where?
    2. I wonder if when I disconnect the thermostat connected directly to the boiler if I need to again create a link to complete a circuit, this is currently hard wired in via a boile?
    3. I am unsure how to connect the CH wires to bypass the controller. The CH is set up and working now when I turn the ChannelPlus on all the time, I just need them to work when I disconnect the wires.

    I appreciate that this is a DIY install and I could get someone in to do it, but I am trying to work it out myself

    Thanks in advance
    What is triggering your boiler in your evohome set up? In your old system, the timers were operating the valves and inside the valves there were switches triggering your boiler. Evohome can also operate in a similar fashion where the zone valves are operated by the BDR91 and the micro switches in them triggers the boiler. Or infact Evohome has a 3 relay connection. Where one BDR91 does CH and one does the DHW valves. But then a 3rd BDR91 is added called the Boiler Relay, and it's job is simply to fire up the boiler.

  10. #10
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    At the moment its the old 7 day programable controller which is triggering it.
    I was hoping to wire in BDR1 to perform that function - I've accepted defeat and a sparky is coming next week!
    Thanks for the input

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