Smart Thermostat and Smart TRV installation advice

[joboro]

So in summary hopefully I have this right:
We have 8 rads and it would be worth me putting smart TRVs on the kitchen/ diner, living room, 3 x bedrooms, nursery. It would also be worth putting a dumb TRV on the hall and bathrooms, unless we wanted those areas to get quite warm?
And the room thermostat should go in the room we want to most accurately control temperature such as the baby room as it will more accurately control the temperature of that room, but it doesn't too much matter otherwise?

Hopefully I have all that correct?!
If so, I need to purchase 1 more smart TRV

Thank again!

 

[Lower]

With that system, can the Smart TRV's override the thermostat and turn on the heating by themselves?

 

[ian1182]

So in summary hopefully I have this right:
We have 8 rads and it would be worth me putting smart TRVs on the kitchen/ diner, living room, 3 x bedrooms, nursery. It would also be worth putting a dumb TRV on the hall and bathrooms, unless we wanted those areas to get quite warm?
And the room thermostat should go in the room we want to most accurately control temperature such as the baby room as it will more accurately control the temperature of that room, but it doesn't too much matter otherwise?

Hopefully I have all that correct?!
If so, I need to purchase 1 more smart TRV

Thank again!

You should not fit a smart TRV in the bathroom/en-suite as the electrics can be affected by the damp atmosphere. A regular dumb TRV is OK for either. That said, I don't have any TRV on the bathroom/en-suite radiators as these are my bypass devices.

If your aim is accuracy of temperature, the roomstat should go into that room as the smart TRV's use an alogrithm to estimate. The TRV sits within a few inches of the heat source and hence makes a "guess" on the ambient room temp. In the Home Assistant thread I previously linked there has been some discusion on the accuracy of the TRV's and the belief that a roomstat works better. Unfortunately a roomstat is twice the cost of a TRV (£80 vs £40).

On the general points. Do you have dumb TRV's on all your existing radiators?, if not get a heating engineer to add them. The cost of the actual dumb TRV is modest in comparison to the fitting cost. As you have invested in Drayton easiest is to just get some RT212 or TRV4's. You then have a base for fitting a smart TRV.

On the installation, start simple and work upwards. I would install just the Hub & roomstat to begin with, then add smart TRV's one by one in the zones you feel need independent control. I'd hold off getting another iTRV until you need it.

 

[ian1182]

With that system, can the Smart TRV's override the thermostat and turn on the heating by themselves?

No, I believe in a zone with a roomstat & smart TRV's it's the roomstat that wins. Any temp seen within the Wiser app is from the roomstat. In essence the roomstat senses the temp and the Wiser Hub instructs the smart TRV's to open/close.

If the zone contains 2 or more smart TRV's (and no roomstat) there is some averaging between them to determine the temperature.

 

[Lower]

No, I believe in a zone with a roomstat & smart TRV's it's the roomstat that wins. Any temp seen within the Wiser app is from the roomstat. If the zone contains 2 or more smart TRV's (and no roomstat) there is some averaging between them to determine the temperature

In which case the roomstat needs to go in the coldest room in the house and let the Smart TRV's turn off the heating in the other rooms when they get up to temp. Otherwise a TRV might be calling for heat, but the roomstat is up to temp so prevents the heating being turned on.

 

[ian1182]

In which case the roomstat needs to go in the coldest room in the house and let the Smart TRV's turn off the heating in the other rooms when they get up to temp. Otherwise a TRV might be calling for heat, but the roomstat is up to temp so prevents the heating being turned on.

If the zone contains both a roomstat & smart TRV's they will not call for heat as it's at the desired temp.

Unfortunately the Drayton terminology is confusing, sometimes they use room other times zone. For example the single channel Wiser with two smart TRV's is described as multi-zone.

https://www.draytoncontrols.co.uk/products/Smart-Heating/Wiser/wiser-multi-zone-kit-1-0

A zone in Wiser speak is a managed area. In the app they call it a room, however it could be a single room or combination of rooms or even the entire house. If you had just the Hub and single roomstat the whole house would form a single zone within Wiser, or Hub and 2 roomstats would be 2 zones. Additional zones can be added by using smart TRV's. Generally 1 or more Wiser zones fit within a physical central heating circuit.

The general principle is true, you would desire any rooms containing dumb TRV's for the TRV to close prior to the heating cutting out.

 

[Mister Banks]

Ahhh OK this makes sense I think. So if I put a smart TRV and smart stat in the baby room the room stat would tell the smart TRV to shut off at the right temp?

Yes, the room stat takes over and controls the TRV.

 

[Lower]

If the zone contains both a roomstat & smart TRV's they will not call for heat as it's at the desired temp.

The general principle is true, you would desire any rooms containing dumb TRV's for the TRV to close prior to the heating cutting out.

Unless a smart trv is able to override the room stat and turn on the boiler, the only benefit of smart TRV's is the fact you can schedule the temperature in the room the smart TRV's are fitted, as long as the room stat somewhere else is calling for heat.

I wouldn't expect a roomstat and Smart TRV to be in the same room.

 

[Mister Banks]

In which case the roomstat needs to go in the coldest room in the house and let the Smart TRV's turn off the heating in the other rooms when they get up to temp. Otherwise a TRV might be calling for heat, but the roomstat is up to temp so prevents the heating being turned on.

Every room stat or iTRV has to be allocated to a room. If a room stat is allocated a room containing one or more iTRV’s it takes control of the room. The way I use my Wiser system means There is no point having a room stat in a room without at least one iTRV as it will conflict with the rest of the system. I use my room stats in rooms to compliment the iTRV.

 

[Lower]

Every room stat or iTRV has to be allocated to a room. If a room stat is allocated a room containing one or more iTRV’s it takes control of the room. There is no point having a room stat in a room without at least one iTRV as it will conflict with the rest of the system. I use my room stats in rooms to compliment the iTRV.

I'm not sure i understand. If the roomstat takes over that room, why does the same room need a smart TRV?

Secondly, if its only the roomstat that can turn the boiler on, once the room that the roomstat is in gets up to temp the boiler will turn off and the rest of the smart TRV's become useless until the boiler gets turned back on by the roomstat.

 

[ian1182]

I'm not sure i understand. If the roomstat takes over that room, why does the same room need a smart TRV?

Secondly, if its only the roomstat that can turn the boiler on, once the room that the roomstat is in gets up to temp the boiler will turn off and the rest of the smart TRV's become useless until the boiler gets turned back on by the roomstat.

That is true if the roomstat and smart TRV's are allocated to the same "room" in Wiser. If however the roomstat is in "room1" and smart TRV in "room2" they independently control the boiler.

Perhaps my use of zone is not good. Unfortunately in the Wiser app it uses "room" when it really means an area (i.e. zone) of the property that could be one or more actual rooms. Apologies for the confusion.

 

[Mister Banks]

I'm not sure i understand. If the roomstat takes over that room, why does the same room need a smart TRV?

Secondly, if its only the roomstat that can turn the boiler on, once the room that the roomstat is in gets up to temp the boiler will turn off and the rest of the smart TRV's become useless until the boiler gets turned back on by the roomstat.

It does take a while to get your head around this. Don’t think of the room stat as being the only device that calls for heat, every iTRV also calls for heat independently unless it is allocated to a room that contains a room stat. In theory you don’t need a room stat in the same room as an iTRV but if you want more precise control over room temperature or the iTRV is installed in a poor position such as behind furniture then a room stat helps to control temperature much better.

 

[oldbutnotdead]

You might want to consider the room stat going in the hallway- it's timer and temperature settings will then give a background heat level for the rooms without smart valves (hallway, bathrooms). Don't put a TRV on the hall radiator until you can determine whether it's set up as a bypass heat sink. Do put conventional TRVs in the bathrooms.
And then play away. The Smart trvs seem to work (on temperature determination) about as well as dumb TRVs, play with the values until you get the place comfortable for you.

 

[Lower]

It does take a while to get your head around this. Don’t think of the room stat as being the only device that calls for heat, every iTRV also calls for heat independently unless it is allocated to a room that contains a room stat. In theory you don’t need a room stat in the same room as an iTRV but if you want more precise control over room temperature or the iTRV is installed in a poor position such as behind furniture then a room stat helps to control temperature much better.

If the Smart TRV can call for heat independently, then i get it. That's why i asked if with this system the TRV's can call for heat and i thought the answer was no.

 

[ian1182]

If the Smart TRV can call for heat independently, then i get it. That's why i asked if with this system the TRV's can call for heat and i thought the answer was no.

Your question was "can the Smart TRV's override the thermostat and turn on the heating by themselves?".

If the roomstat & smart TRV are in the same room then "no" is the correct answer. If they are in different rooms, the TRV is not overriding the thermostat as they control separate areas and either can independently turn on the heating.