Vaillant system upgrade for remote control

[GiAl]

Hi,

I would like to upgrade my heating system (ecotec plus VMW 346/5-5 with a VRT370f thermostat) to be able to remotely control it.

I was looking at installing a VRC720f thermostat with a VR921 box and several VR50 TRVs to be controlled with the Vaillant app.

Before embarking in the full purchase, though, I’d like to find out how the system would work.

Specifically, the VR50 only operates the radiator valve or does it also send a request to the boiler (via the thermostat, I suppose) to provide hot water ?

If it is so, which device has precedence, the VR50 or the thermostat itself ?

Just an example: during the night the thermostat is set to, say, 18 degrees and in the room there are 20 degrees. A VR50 in the bedroom detects a temperature in that room that is below the set temperature. What happens ? The VR50 simply opens the radiator valve but the radiator does not heat up because the thermostat is preventing this or the VR50 actually sends a request to the boiler that is honoured and the radiator in the bedroom starts heating, but also all the other radiators that do not have a VR50 installed ?

Does it mean that to prevent this, one needs installing VR50s on all radiators, including the bypass one ?

BTW, I have seen a starter pack with 3 VR50s and the VR920, I couldn’t figure out the difference between the 920 and the 921, would the 920 work in the setup I want to install ?

Thank you !

 

[ericmark]

Theory is the TRV controls room temperature, and it tells the main thermostat/hub when it needs the boiler to run, but in this house for example we have 14 TRV's and it would cost a fortune to have them all linked.

So we select main rooms, and use cheaper non linked TRV's for the rest.

However call it a hub or a thermostat, this has two ways to tell the boiler what to do, digital i.e. on/off, or analogue i.e. up/down, my boiler will not work with up/down type, I think however yours will.

So in real terms we use near enough engineering, having iVector 5 speed fan assisted radiators which can heat and cool may seem ideal until you look at the price, may use a kick space heater in kitchen, but else where they are too expensive.

The main consideration is speed, the faster the heat exchanger can heat the room, the less time the room needs heating for, so with a boiler able to give say 6 - 28 kW of heat, when using a single room, it needs to be able to sink 6 kW of heat or boiler will cycle.

Even fixed output the same applies, I arrive home, and want to cook food, so room one to heat is kitchen, then eat the food, so room two is dinning room, the relax watching TV so room three is living room, then to bed so rooms four are the bed rooms.

By heating each room in order the re-heat times can be reduced, but my house was designed in the old days when we did not have programmable TRV heads. So the radiators are not big enough for this idea to work.

So the ideal is not possible, we move to near enough, so yesterday we went out, Nest Gen 3 linked to my wife's and my phone detected this, and turned down heating to Eco, but I know with temperature showing as -7°C my heating would not turn on early enough, Nest is not very good, so I manually turned it back up with my phone some 2 hours before due home.

Each system will have different response times. I am told the Drayton Wiser TRV heads are smart and work out how long it takes to heat a room, so if due home at 5 pm, and set to 5 pm, the start time will vary depending on how cold it is.

Some geofencing one can select distance, mine is just Eco and Comfort, so each one has plus and minus depending on your life style and the home. This guide tries to compare systems however is seems to thing Nest still works with Energenie, and it does not.

We also have on/off v modulating thermostats, OpenTherm is most well know, so you can have the boiler controlled by the return water temperature or by a modulating thermostat.

I will admit I made an error selecting Nest Gen 3, but it would cost to much to change, again looking at near enough engineering, how far do you want to go?