New installation in a new(ish) house and a few questions.

Hi all first time here, also first time home owner.

Last year i've bought an old house that i am currently finishing renovating. The isolation was horrendous and no heating system you could call one, the previous owner had gas heaters in every other room, yikes.

So after we redid everything properly i decided that i wanted a smart thermostat, amazon not helping. I've got myself a wireless kit and a pack of 4 trvs (for starters, those things are expensive and i have to move in soon, it costs me an insane amount of money already) for 13 radiators in total.

The boiler is a vaillant ecotec pro from 2022, it does both heating and hot water and was connected to a digital thermostat working in off/on mode. I wired the wireless kit to the vaillant's ebus, put the shunt back in as per instructions, set tado to D07 and it seems to be working. The boiler fires up when i set heat to the max and stops when i set it to zero, it also looks like it's modulating properly as i am not observing the water going higher than 39°C once the house heated up.

Now for the questions. The radiator setup is as follows: 4 Radiators downstairs, 5 on second floor and 4 on the third.

I've put one trv in the living room downstairs, it's the most stable room it has only one wall that's directly exposed to the outside and also the one with the biggest radiator.

One in the office on the second story, one in the bedroom (it has a small room adjacent to it with no door with a small radiator in it) and the last one in the extra room. All on the same floor.

The rest of the radiators are equipped with the usual thermostatic valves and all are set to 2 out of 5 (i have to check the actual temp this gives me and adapt) safe the one in the hallway downstairs which is opened full blast (cuz you need at least one open radiator to not overheat the boiler i've heard). The wireless temp sensor/thermostat is in the living room.

The idea is when the living room hits the desired temp (with the sensor in the middle of it) the TRV closes the biga$$ radiator and the room will remain at the desired temp by opening and closing it rather than calling directly for heat. The rooms on the second floor will regulate their temp individually and call for heat as needed and they do it more often than the living room, they are also set slightly colder (like the bedroom). The rest of the system will get heat when the trv equipped rooms fire up the boiler.

Is it dumb? Are there ways to improve the whole shebang? So far (in the two last days since i've put tado in) the "dumb" radiators are nice and warm, do not seem to be overly heated, their respective rooms do feel properly heated too.

The boiler seems to be on 24/7 also according to the tado app, i suppose because it modulates instead of goint into on/off cycles, or is it supposed to shut down at some point?


  • If you're happy with the performance of the system as you've installed it, and with the current efficiency, then you could spend a lot of time tinkering for very little material return.

    However, a few observations:

    • You're probably unnecessarily overheating your hallway. What you've heard about leaving a rad open is to do with the scenario where there are TRVs on every rad and they're all closed. In this situation, there is indeed a risk of overheating the boiler and also of damaging the pump (as the water has only the much smaller primary circuit available). Typically, you'd leave bathroom rads off TRVs to serve this purpose (bathrooms being desirably warm), but also because a TRV will close the bathroom rad exactly when you want it open - after a shower/bath, when you're in your birthday togs. You could turn the hall rad down and open bathroom(s) instead.
    • TRV setting 2 is about 16C. 1 is 12C and 3 is 20C, etc.
    • If your system is running 24/7, it sounds like you're not using any temperature setback at night? In which case, you might be spending more than you need heating rooms whilst you're tucked up in bed.
    • Also re 24/7, depending on the size and modulation ratio of you boiler, if it's running constantly, you might find as the weather warms up again, your boiler starts to cycle itself on and off rather than modulate right down, as the heat demand should fall and in turn, the flow temperature. Few boilers can modulate low enough to keep the burners on in milder weather. Ours for example, can only go down to 7KW, which is more than we need most of the heating season.
  • I'd like to avoid glaring mistakes if possible, and also be reassured i didn't just made things worse, that gas is getting more expensive by the hour :p So thank you for the reassurance.

    At the moment since i'm moving things around i've set the same low(ish) temperature everywhere, once i start living there 24/7 i'd make the necessary adjustements to the overall planning, also cat.

    I prefer heating the rooms i'm not occupying to at least 15-16°C. Since we've finished the walls mid september i'd like to avoid mold and humidity, also the wooden flooring is brand new, would be a shame if it gets too wet. For example, we haven't been heating the four rooms upstairs at all, as my "foreman" my dad, would say "pshhh those would heat up anyways", except they didn't and i had streams of condensation running from the windows making puddles on the floor. Now that the valves are set to 2 there's no condensation anymore.

    The hallway leads to the stairs, i'd like to believe it sends heat up there. But the bathroom is worth considering, the throne is not comfortable at 16C :D

    Right now i'm burning about 15m3 of gas per 24h period, that's when it's -4 to -8 outside at night and still below zero during the day. I consider that to be somewhat reasonnable for a 150m² house, but my "foreman", who lives in an over insulated bunker, uses about 4m3 for half the surface.

  • I hadn't appreciated you're not currently living in the property, and are constantly running the heating on low.

    15m3 pretty much maps onto our home, per m2, although we are living here and it's an old property. We have good levels of roof insulation wherever possible, around 60% double glazing (conservation area), but the walls are uninsulated solid 9" and nothing done with the floors. Definitely not the most energy efficient.

    Agreed that 15-16C in unoccupied spaces is about right. All our rooms are set to at least 16C during the daily heating period. This does drop a bit overnight due to small setback (main living spaces set to around 16C so there's an equivalent drop to around 14C in the others). That setback does save on gas compared to 24/7 constant temp running, and through programmed step back up (as opposed to tado Early Start which doesn't work with our boiler weather comp), gets us back up to temp for the morning.

    Similar to your OT load comp, our weather comp is keeping the boiler running most of the time. It's been steady around 57C during the cold snap, but this morning (11C outside) is down to around 43C. So modulation, as opposed to stat switching on/off. In the shoulder seasons (spring and autumn), we get more boiler cycling as modulation ratio isn't great - it's an older Viessmann (min power around 7kW).

    Condensation is of course a consequence of relative humidity. Heat the air and it can hold more moisture. Given the structure of our house, we still get window condensation with RH below 50%, but promptly removing it (window vac) and regular airing keeps it under control.

    Large temperature swings also encourage condensation. We run our house at 18C during the day (18.5 in the evenings). As I mentioned, 16C setback. So not a great deal of difference. Particularly important with properly set weather compensation, as we'd never catch back up after a deep setback. Also worth considering with load compensation, to avoid tado adjusting up the flow temp (and so reducing boiler condensing) to catch up.

    In a nutshell though, you seem to already have things pretty well dialled in. It's easy to get too interested (as opposed to interesting) about running the system as efficiently as possible. Minimum flow temperature to achieve minimum comfortable room temperature throughout the house and you can't really go wrong.