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Thread: Can Evohome control floor zone valves in addition to the HR92 smart TRVs?

  1. #1
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    Default Can Evohome control floor zone valves in addition to the HR92 smart TRVs?

    Hi there,

    I have had Evohome for some time but our boiler has just packed up and we're getting a new one installed in an alternative location soon. We have a three storey house and the new boiler will be positioned on the middle floor to service central heating and a megaflo unvented cylinder.

    All rooms have HR92 controllers on the radiators except the bathrooms and hallway radiators (6 radiators in total).

    I would like to know if it's possible to have a 'floor zone valve' that can be controlled through Evohome that can be fitted as part of the new boiler installation and pipework adjustments (that will anyway be necessary). I'd like to be able to switch on only the top floor radiators (master bedroom and nursery +non HR92 ensuite) just before we go to bed without having the other 5 non-HR92 radiators in the hallway and downstairs bathrooms coming on.

    Is it possible to do this? And if so what kit would I need to purchase?

    Kind regards,
    Paul

  2. #2
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    Hi,

    With some pipework adjustments this should be possible. You'd have to decide exactly which radiators/floors are controlled by the zone valve and I guess you'd want these to be the downstairs bathrooms and hallway, but not any of the radiators with HR92s. The zone valve could be controlled by its own BDR91 and you'd also need to choose a temperature sensor (you could use the evohome controller if it's in a suitable position or a separate device like a DT92). I think you'd also need a HR92 added to the upstairs bathroom radiator so that it doesn't switch on every time the boiler fires. Alternatively, you could just add HR92s to all 6 radiators (assuming they already have TRVs) and then group them into zones on the Evohome controller and you wouldn't require the zone valve etc.

    Dan

  3. #3
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    Quote Originally Posted by greenonline View Post
    I would like to know if it's possible to have a 'floor zone valve' that can be controlled through Evohome that can be fitted as part of the new boiler installation and pipework adjustments (that will anyway be necessary). I'd like to be able to switch on only the top floor radiators (master bedroom and nursery +non HR92 ensuite) just before we go to bed without having the other 5 non-HR92 radiators in the hallway and downstairs bathrooms coming on.

    Is it possible to do this? And if so what kit would I need to purchase?
    A better question is whether it's logical to complicate your installation this much by adding zone valves, rather than just fitting HR92's on the remainder of your radiators ? As long as you have an Automatic Bypass Valve installed in your system (which you probably already do) then you can fit HR92's on all radiators and thus have all radiators controlled. This allows any individual radiator in the house such as a bedroom to come on by itself without bringing on any other uncontrolled or manually controlled radiators. This is a major benefit IMHO.

    If you have HR92's on all radiators you have complete flexibility in your scheduling, so it is dead easy to have your bedrooms scheduled to come on in the evening and through the night at a comfortable night time temperature while your downstairs goes off.

    Our bedroom is scheduled to come on at 18 degrees from 8pm for our 3 month old and stay that way through the night, whilst the living room downstairs goes off at 11pm (or manually if we go to bed earlier) and the other downstairs rooms go off at 8pm.

    We don't even have to think about the bedroom being up to temperature at night - its always ready at bed time, and as an added bonus, not only do none of the downstairs radiators come on at night if the bedroom needs heat (they are scheduled for 5 degrees frost protect) the boiler won't even come on at all if the weather is warm enough that the bedroom is already above 18 degrees at bed time.

    Or if it starts off warm then gets cooler in the night it might come on a little bit after say 3am to keep the room from dropping below the set temperature. It works brilliantly, although I'd recommend a remote wall mounted thermostat like a DTS92 mounted away from the window near the head of the bed rather than relying on the HR92's built in sensor if you sleep with the window ajar. (As cold air from the window flowing down over the radiator can make the HR92 think the room is colder than it really is causing the radiator to come on more than it should)

    So my recommendation would be to check that you have an automatic bypass valve already fitted (or the system uses a variable speed pump) so that you can eliminate your always on / bypass radiators and fit HR92's to them. Then you have complete scheduling flexibility and it will definitely do what you ask.

    I'm not even sure that the scenario you describe could be programmed using Zone Valves on the Evohome system.
    Last edited by DBMandrake; 9th July 2016 at 09:54 PM.

  4. #4
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    Thanks DBMandrake

    This is the dilemma... I understand that I can have full control of each room by having HR92s on all rads but because of the design of our Edwardian house we have a large central staircase that runs up the centre and the hallway/landing is a massive expanse. My concern was that if we don't have the hallway radiators on then as soon as you open a door for one of the rooms the heat will just be sucked out into the hallway and given that you can only have 3 on/off time settings per radiator I'd need to choose when to trigger those so may find I'm constantly having to manually adjust those. Because of the massive expanse they'd never reach the target temperature so the boiler would no doubt be on 24/7. My thinking was that if one or more Hr92 rooms are on then there's no harm in having the hallway and bathroom rads/towel rails on too to prevent heat leakage from the rooms, and these radiators can be turned down manually through their regular valves so they're not on full blast.

    If there's no other way of doing it then I may have to put HR92s on 'all' but it would be useful to understand all potential options before committing another 300+ on 6 more HR92 valves and potentially over-complicating the scheduling in the process.
    Last edited by greenonline; 9th July 2016 at 10:54 PM.

  5. #5
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    Quote Originally Posted by DanD View Post
    Hi,

    With some pipework adjustments this should be possible. You'd have to decide exactly which radiators/floors are controlled by the zone valve and I guess you'd want these to be the downstairs bathrooms and hallway, but not any of the radiators with HR92s. The zone valve could be controlled by its own BDR91 and you'd also need to choose a temperature sensor (you could use the evohome controller if it's in a suitable position or a separate device like a DT92). I think you'd also need a HR92 added to the upstairs bathroom radiator so that it doesn't switch on every time the boiler fires. Alternatively, you could just add HR92s to all 6 radiators (assuming they already have TRVs) and then group them into zones on the Evohome controller and you wouldn't require the zone valve etc.

    Dan
    Hi Dan,

    Can the Evohome control two BDR91s? How would that work? Would the zone valve itself be a 'room' on the Evohome controller? If the top floor master bedroom Hr92 was set to come on could that trigger this separate BDR91 so the zone valve 'closes' to the middle and ground floors?

    Appreciate if you could elaborate further.

    Kind regards,
    Paul

  6. #6
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    Hi Paul,

    Yes, another BDR91 can be bound as the actuator for a new room/zone and it will control the zone valve via the Evohome controller (you also need a temp sensor). It would just function in a similar way to an additional HR92 with its own zone. There's no simple way of linking zones so when one switches on another automatically switches off. This would all have to be controlled by schedules on the controller. I'm sure there would be a clever way of wiring the system so it works the way you've described, but you'd also want both zones on at other times rather than only one at a time.

    My recommendation would be to use HR92s on all rads (this is my setup).


    Dan

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