Tado shows as heating but Vaillant ecoTEC plus 831 does not heat CH

abs

We're having some issues with our tado not heating the house.

We have a standard Vaillant ecoTEC plus 831 combi boiler.

The hot water seems fine (adjusting the hot water temperature in the app changes the temperature from the tap), but the central heating shows its heating but the boiler just kicks in for a short time, then the display shows a flashing radiator symbol, which apparently means the target CH water temp has been reached and the pump is still just circulating.

Does anyone have any thoughts - is there a way to adjust the target central heating water temperature via tado?

Thanks

Wouwou

Is it resolved yet? Have the same problem

eezytiger

It appears you are using eBus control. I have the same boiler and I've had Tado for one year. Twice I have tried using eBus and twice I have given up. With eBus, Tado can ask for some extremely low flow temperatures, such as 33C. At minimum 9 kW output power and maximum 24 kW such a temperature can be reached in a few seconds, depending on the existing water temperature and how many rads are open to dissipate heat.

In my opinion this boiler is not well suited to eBus control with Tado. I think it is better to use relay control and set a target flow temperature manually to suit the needs of the system and outdoor temperatures at the time.

I have taken a few specific steps with my system to try to improve operation and operational efficiency.

1. Use relay mode.

2. Manually range rate the boiler to the minimum output of 9 kW at all times. 24 kW is completely unnecessary for most average homes.

3. At present my flow temperature is limited to 50C. This allows sufficient heat to reach the radiators and do some meaningful "work" whilst keeping return temperatures low and keeping the boiler highly efficient.

4. Of nine radiators and eight SRTs, only two radiators can demand heat from the boiler. The rest of my SRTs are in independent mode and cannot force the boiler to fire. In this way, when the boiler does turn on, there are usually a few radiators ready and waiting to take a share of the boiler output. You cannot force 9 kW out of a single radiator, never mind 24 kW, so it is better to have more radiators needing heat at the same time so that it has somewhere to go. This will keep return temperatures lower for longer and help to avoid premature "overheating" of the output flow.

5. Our house is almost always occupied, so, rather than blasting the house at breakfast time, going cold during the day and blasting again in the evening, we just keep the heating on 24x7, with thermostatic control. This way we can trickle out the heat throughout the day and night, keeping the fabric of the property and its furnishings at comfortable temperatures at all times. Thus 9 kW for temperature maintenance is ample. In fact, I am trying to run our system more along the lines of a heat pump - relatively low (for a gas boiler) flow temperatures, "larger" emitters, by way of multiple rads warming the house at the same time instead of only one or two, and never letting the house get cold.

Of course, different homes and family demands will need their own individual solutions, but I've described what works for us. The biggest takeaway is that eBus control and the 831 do not play well together. Anything else I've said might be food for thought.

And I don't pretend to be an expert. I'm just a retired guy with plenty of time to think things through and test my theories. So far I'm pretty happy with the results.