Evohome TRV and thermostat without controller

[fishslinger]

Hi, just joined

Is it possible to pair one or more TRVs to a thermostat without the controller?

Thanks

[DBMandrake]

Interesting question, but I'm not sure I see the point of it.

Without the HR92 being paired to a BDR91 you still couldn't call for heat from the boiler.

An HR92 can work standalone with no bindings, I know that much. However in that case it will only act as a dumb TRV where you can set the temperature by turning the knob, you get no scheduling (as that is done by the controller) and it will only open and close the radiator valve, but be unable to call for heat from the boiler. Most or less exactly the functionality of a mechanical TRV, just a bit more accurate.

[fishslinger]

Yes I will leave the scheduling to our ancient mechanical timer (for now)

I would like to have the thermostat seperate to the radiator

[HenGus]

Yes I will leave the scheduling to our ancient mechanical timer (for now)

I would like to have the thermostat seperate to the radiator

Sounds like an expensive option for no real benefit. I appreciate that Evohome isn't the cheapest of smart heating options but the controller can work as a smart thermostat in its own right without any HR92s. Personally, I would start with that then add HR92s as funds become available. You can have a mix of HR92s in rooms that you use and conventional TRVs in occasional rooms. The downside of this is that the rooms with conventional TRVs will come 'on' whenever a room with a HR92 demands heat. Conversely, a room with a conventional TRV may not get any heat unless a room with a HR92 is demanding it.

[DBMandrake]

I'm in that situation - I have 9 radiators (well, 7 for now, as both radiators have been removed from the dining room for renovations) in 8 zones but so far I only have 5 HR92's.

The dining room, (which doesn't get used that much except as a thoroughfare to the upstairs loft conversion and somewhere to dump things like push chairs and bouncers!) study/exercise room and spare bedroom are all still on manual TRV's for the time being. Not ideal, but all the heavily used rooms are scheduled and controlled.

Aside from the drawbacks you describe the only thing that annoys me a little is I need to remember to manually turn down those three rooms with manual TRV's before bed in case the bedroom radiator comes on to maintain our minimum night time bedroom temperature. (Currently 17 degrees with a 6 month old also sleeping in the room) If I forget to turn them down and its a cold night those other radiators will also come on in the night and waste a lot of energy when the bedroom HR92 fires the boiler.

As for manual TRV rooms not being able to call for heat on their own - keep in mind that you have exactly the same problem with a conventional one thermostat system - if your hall thermostat is satisfied no other room in the house can get heat, no matter how cold! So you're no worse off in that regard and at least with Evohome with a few HR92's there is a much greater chance of some other room other than just the hall needing heat and allowing the manual TRV rooms to warm up somewhat by piggybacking on boiler demand from other rooms.

[HenGus]

I agree that it is not a perfect set up but it as good as HIVE with the option to zone in the future.

[fishslinger]

I agree that it is not a perfect set up but it as good as HIVE with the option to zone in the future.

That does sound like a sensible option. I didn't realise that the controller also contains a thermostat. I have an hr92 and ravl adapter arriving tomorrow so I will be able to see if the system is going to work on my radiators