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Thread: Completely new heating install, best way to configure for EvoHome?

  1. #71
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    I don't suppose you have a picture of the CS92A connected to the temp probe?

  2. #72
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    Not off hand no, however here is one from google:



    The CS92A is on the left. On the right is the strap on sensor for vented cylinders but the kit also comes with a probe style insertion pocket sensor for unvented cylinders. The sensors both have about 60cm of cable built in to connect to the CS92A but as mentioned you can extend that if needed.
    Last edited by DBMandrake; 5th February 2017 at 05:04 PM.

  3. #73
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    Ah, so having purchased the Evo Home Shop Connected Value Pack A, I should have 2 x BDR91s and a CS92A? One BDR91 is for the boiler and the other is for the CS92A?

  4. #74
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    You're getting confused. The CS92A and the BDR are totally unrelated. The BDR is a relay used for controlling things, like zone valves, boilers, etc. The CS92A is a wireless transmitter that sends the temperature of your hot water to the controller.

  5. #75
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    Quote Originally Posted by dty View Post
    You're getting confused. The CS92A and the BDR are totally unrelated. The BDR is a relay used for controlling things, like zone valves, boilers, etc. The CS92A is a wireless transmitter that sends the temperature of your hot water to the controller.
    Page 5 of the Evohome Installation Instructions might help. That said, it is an easy mistake to make. In my system, 'S' plan, I have two BDRs: one controls the CH zone valve and the other the HW zone valve.

  6. #76
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    Evohome assumes you need one BDR91 for the HW and the other to fire the Boiler as a Boiler Relay. If you have a true S plan then you will land up with 3 BDR91s. One for HW, one for CH and one for Boiler. Ofcourse you could choose to use an OT bridge instead of a Boiler Relay and then have the two BDR control the HW and CH valves only.

  7. #77
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    Quote Originally Posted by bruce_miranda View Post
    Evohome assumes you need one BDR91 for the HW and the other to fire the Boiler as a Boiler Relay.
    No it doesn't - the most common S-Plan configuration with Evohome has two BDR91's - one for the HW zone valve and one for the CH zone valve. The boiler is fired using the orange wires of both zones valves not directly, so there is no boiler relay in this configuration.

    If you only have a hot water zone valve and no heating zone valve (in which case it's not really an S-Plan or Y-Plan system) then yes you can configure the two BDR91's as hot water zone valve and boiler relay instead, and let the HR92's prevent heating during hot water demand, provided all radiators have HR92's.
    If you have a true S plan then you will land up with 3 BDR91s. One for HW, one for CH and one for Boiler.
    This three relay configuration is a second option for S-Plan/Y-Plan - and is the one I use. It's more complicated but it does give some additional flexibility over firing the boiler from the zone valves or not having a heating zone valve.
    Last edited by DBMandrake; 5th February 2017 at 08:56 PM.

  8. #78
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    The reason I said Evohome assumes one BDR to work the HW and one to fire the boiler is because that's how it comes configured in the box. To use the Boiler relay to work the CH valve instead you need to unbind it as the Boiler relay and rebind it as the CH zone valve relay.
    Evohome expects all your radiators to have HR92s with no separate CH zone valve.

  9. #79
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    Quote Originally Posted by bruce_miranda View Post
    The reason I said Evohome assumes one BDR to work the HW and one to fire the boiler is because that's how it comes configured in the box. To use the Boiler relay to work the CH valve instead you need to unbind it as the Boiler relay and rebind it as the CH zone valve relay.
    Evohome expects all your radiators to have HR92s with no separate CH zone valve.
    That's how mine works (due to piping layout, primarily), but it's described as an "alternative layout" in the installation guide.

  10. #80
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    Quote Originally Posted by paulockenden View Post
    I know this isn't what you want to hear, but Evohome works best when you give it control of everything. I think that when spending the amount you must be, it's daft to skimp on a couple of hundred quid for additional HR92s.

    However, if you do that, a couple of things to note:

    1 - You won't actually need the four zone valves (so perhaps a saving can be made there to pay for the HR92s?).
    2 - You'll probably need to have the controller on one of the middle floors, to get a reliable signal to the top floor and your basement. Ideally somewhere in the middle of that floor too, rather than on an external wall.

    As for the 12 zone limit, you can put several HR92s (or even rooms) into the same zone. So you could have a 'bathrooms' zone, for example, or 'second floor'.

    I'm sure others will have observations too....

    P.
    Does this mean the combination of EvoHome BR91 and HR92s on a S Plan dual valve system will effectively zone?

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