Wall thermostat integration with TRV heads (electronic)

27 Jan 2008
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Llanfair Caereinion, Nr Welshpool
United Kingdom
Years ago we were always told, you don't fit a TRV in same room as the wall thermostat, well that has clearly all changed.
MIHO069 Full User Guide said:
TRV warmup time (16)To allow any TRVs to reach their own designated target temperature, the heating can be set to continue heating for abdefined time after it has reached the target temperature at the thermostat location. This TRV warm up time can be set from the settings section on either the web browser, or smartphone app.
It is now expected to have both TRV and Wall thermostat in the same room, but from the quote it is clear they have to be set to complement each other and not fight each other.

To date that is the only thermostat where I have seen instructions on how to set, in fact only one where I have seen a warm up time option.

The big advance in my eyes is having °C marked on the TRV, not more silly *123456, but it seems how the TRV works with the wall thermostat varies a lot, and I am not impressed with the MiHome Energenie method, having the TRV follow the wall thermostat seems to me the wrong way around, Hive idea seems better where the TRV tells the wall thermostat to run boiler even when the target temperatures has been reached by wall thermostat.

Nest wall thermostat was suppose to work like the MiHome Energenie one, however the support was withdrawn, it does work of sorts, but not reliably. The TRV will some times follow, but not every time.

EvoHome will it seem not work without TRV heads, but not sure on this? But it does seem to have been one of the first fully integrated systems, but the Hive allows one to slowly add, rather than buy all together, which is what I tried to do with Nest only to find support withdrawn.

So my TRV heads are set to same schedule as the wall thermostat, but not linked, as yet not tried setting the TRV heads to geofence, the Nest wall thermostat does, and also has occupancy detect, so if family in the house it will not shut down.

I feel I wasted money with MiHome Energenie as they can't be manually adjusted, so if I walk into a cool room and phone is not in my pocket then it seems can push button and I get 21°C for one hour, the default is 16°C which is a tad low, but with the cheap eQ-3 I can set the eco and comfort settings and once set pushing one button swaps between them until a program change is reached, and boost button opens up TRV head to 80%, it also actually tells you if the valve sticks, or travel too much or too little, no putting spacers in like the MiHome Energenie.

But most of these systems you only learn what they can do after you have bought them, all top often you get "Follow the instructions on the app." which means no idea how it works until you have bought and installed it.

So the instructions for Hive seem great, the way it should integrate wall thermostat to TRV head, but so did Nest and MiHome Energenie until I tried it.

So other than MiHome Energenie and Nest which I now know, how do the other makes work, do they really integrate, or when it comes to real life are there problems? Specially using wall thermostat and TRV in same room, if my TRV fails to alter temperature in any room other than hall, it just means one room is wrong temperature, but if the hall TRV fails to follow set seclude, so it does not match the wall thermostat, then heating can get stuck on or off. As yet not happened but the TRV uses batteries, not sure what MiHome Energenie does when batteries discharge, the eQ-3 TRV head is designed to open once battery becomes depleted, MiHome Energenie don't tell you, should last 2 years, I change every year to make sure.

So what does Hive, EvoHome, or Tado TRV heads do when batteries become depleted?
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Years ago we were always told, you don't fit a TRV in same room as the wall thermostat, well that has clearly all changed.

The manual for the MiHome Energenie TRV's doesn't say that.


It just has the general instruction that if there is a TRV already there to set it to maximum, so it is manually overridden and effectively not fitted.
They can't make up their mind, for the thermostat it says they need to follow, and for TRV there should be no thermostat to follow. And yes the MiHome Energenie does not effectively link to wall thermostats, but Hive, EvoHome, and Tado do, and even when there is no wireless link, both wall thermostat and TRV can run same schedule.

At the moment my TRV heads are not set to geofence, my worry is the wall thermostat may switch on before the TRV switches on, so the boiler would be cycling waiting for TRV to open, and if the wall thermostat switches off, it does not matter what the TRV does, it will not heat the room, however there is the speed of response, if I have been out all day, I would assume the TRV has motored wide open, so on my return the wall thermostat switches on the boiler and the radiators all reach full heat before the TRV has had time to close, if the room has cooled to 16°C this is not a problem, well before the room reaches 20°C the TRV will have been closing, but if the room is at 19°C, then the TRV could fail to close fast enough, and the energy in the radiator is still going into the room after the room has reached 20°C as the thermals in the room have not started quick enough to even tell the TRV to start closing, air takes time to circulate to both warm the wall thermostat and the TRV.

I actually find out of house for an hour all OK, the house has not cooled enough for TRV to have fully opened, out of house for 6 hours OK, there is time for TRV to act before rooms (except hall where wall thermostat is) over heat. But out for 3 hours then it is common for heating to over shoot, and I am really not sure the geofencing and occupancy detection is really worth it. For what it saves, may be better to always come home to warm house, but being 5 minutes from work I suppose does not give system much of a chance to heat up home before I arrive.

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