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

  1. #1
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    Default Completely new heating install, best way to configure for EvoHome?

    Hello all,

    New here.

    I'm having a fresh central heating and hot water installation done (all new pipework, new boiler, new rads, new unvented cylinder) at my new place which has a cellar, ground floor, first floor and second floor. There are 4 zone valves (1 for HW, 1 for cellar/ground, 1 for first floor and 1 for second floor).

    My installer is competent but has not installed EvoHome before. He is going to call Honeywell for advice but I thought I'd ask here what the best way is for him to wire the zone valves?

    Secondly, some of the house (second floor) may be unused for some time and I may want all the radiators there switched off, save for the hall way one, perhaps - should I get HR92s for this floor?

    Thirdly, I don't want to have specific control of every single radiator (say bathrooms). How does this work with EvoHome which I understand has a limit of 12 zones?

    Thanks in advance.

  2. #2
    Automated Home Legend paulockenden's Avatar
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    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.

  3. #3
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    A starter for you and your installer should be the Evohome Installation Guide and this website:

    http://youlearn.honeywelluk.com/course/evohome

    I will leave it to others with more knowledge of Evohome and multi motorised valves to comment on your proposed set up. Suffice it to say, that if HR92s are fitted to all radiators, no motorised valves (except for HW) are required. HR92s are grouped into zones with one HR92 acting as the zone temperature sensor ( a separate remote sensor can be used instead). I do have the standard 'S' plan with 12 zones. When a zone demands heat, the valve opens and the boiler comes on. When no heat is demanded, the valve closes and the boiler heat shuts off.

    PS: I should have added that Evohome has to be installed fully in accordance with the installation guide. In particular, minimum separation distances for the various components are essential if you don't want to spend your life trying to resolve communications faults. I would also suggest that you get your installer to fit HR92 compatible TRV bodies (honeywell Valencia)
    Last edited by HenGus; 22nd January 2017 at 09:45 AM.

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    Evohome is really designed to have control over every radiator using an HR92 - anything else is a compromise in some way or the other.

    It sounds like you weren't planning to get any HR92's ?

    You are limited to 12 zones per controller but there is no hard limit on the number of HR92's. So if you have multiple radiators per room that keeps the total number of zones at 12 or less that is not an issue. It's also possible to group multiple rooms into a single zone using "multi-room zone" mode, where those rooms share the same schedule.

    It might be the case for example that you could group multiple bathrooms together to follow the same schedule thus "bathrooms" counts as a single zone. Or Children's bedrooms might be another one.

    Some information that would help understand your situation better - how many rooms do you have with radiators in them, and what is the total number of radiators ?

    (Edit: that was freaky - three replies within a minute!)
    Last edited by DBMandrake; 22nd January 2017 at 09:46 AM.

  5. #5
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    Quote Originally Posted by paulockenden View Post
    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.
    Good catch - I hadn't really noticed 4 floors were involved. Depending on the construction of the building its even possible that no one single location will reach all devices on all four "floors", and that two controllers on different floors might be necessary from a signal point of view - so signal testing should really be done before lots of money is spent.

    This would solve the issue of having too many zones for one controller, but complicate the boiler control and wiring. One controller would have to be in charge of hot water and some of the heating zones while the other would be in charge of the other heating zones.

    For that to work well you might need two heating zone valves (in addition to the hot water zone valve) to separate them so that each controller could call for CH heat via its own zone valve. (With both zone valves calling for heat from the boiler) Otherwise there would be interaction between the two controllers where one controller calling for an increase in heat from the boiler would cause the zones under the control of the other controller to overshoot.

    Wiring and zoning for this would be a little bit complicated so would be best left to a Honeywell specialist to figure out if you did go the two controller route.

  6. #6
    Automated Home Legend paulockenden's Avatar
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    I'd imagine a good installer would bring along a controller, an HR92, and a BDR91 and use them to do a site survey prior to doing anything.

    Needless to say, mine didn't....

    P.

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    Had same scenario just over a year ago with new boiler, pipes, rads etc. Big house sideways, not up/down.
    Made the mistake of thinking Evohome is an add-on. It's not. It's core and the boss.

    Had plumbers put in 3 Zone Valves - HW, Up Heating, Down Heating. Wrong - hindsight is wonderful isn't it,

    Most plumbers (or heartng engineers) have years doing standard stuff and that's how their brain is wired. Evo is, simply put, "what it really should be".
    i
    You need just 2 Zone Valves - HW and Heating.
    Good quality constant pressure pump.
    Evo TRVs on every Rad - grouped as needed (as above) (These are the "real" Zones for Evohome).

    I have Evo controlling Valves and Valves controlling Boiler - Boiler controls pump as is needed by IT.

    Sytem works a treat - all rooms exacly where we want them and there is always sufficient HW.

    And for icing on the cake get a Amazon Echo and use Alexa to give even more control - I can say "set office hallway to 21" , "set Bedrooms to 21" or "set downstairs heating to 21" - this would give you ALL the flexibility you describe. ie: "set first floor off"
    Last edited by MrB; 22nd January 2017 at 11:22 AM.

  8. #8
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    Quote Originally Posted by MrB View Post
    You need just 2 Zone Valves - HW and Heating.
    Good quality constant pressure pump.
    Evo TRVs on every Rad - grouped as needed (as above) (These are the "real" Zones for Evohome).
    Actually just 1 Zone Valve for HW, and TRV controllers on all radiators.

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    Quote Originally Posted by bruce_miranda View Post
    Actually just 1 Zone Valve for HW, and TRV controllers on all radiators.
    This can result in room temperature overshoots when hot water demand activates though, due to a sudden increase in flow temperature that the partially open HR92's were not expecting - see my S-Plan thread for my workaround for that in a two zone valve configuration...

  10. #10
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    Quote Originally Posted by DBMandrake View Post
    This can result in room temperature overshoots when hot water demand activates though, due to a sudden increase in flow temperature that the partially open HR92's were not expecting - see my S-Plan thread for my workaround for that in a two zone valve configuration...
    Good point. That said, the two installers that I have been talking to about a boiler replacement looked at my system and tried to suggest that it would be far simpler just to leave the 'S' plan configuration as is, and not worry about the burst of hot water around the CH system.

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