Heating power percentage and calling for heat

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  • Notascoobie
    Notascoobie ✭
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    I actually have the same boiler as you, the 38cdi. My settings are pretty similar to yours. Range rated to minimum power output, and max flow temp at 5 on the dial which is about 65 to 70c. I only have one of my rooms able to fire the boiler and this seems to allow the rest of the SRTs to reach their set temps in independent mode pretty well.. the only difference really is you have adjusted your pump speed.
  • stevo1011
    stevo1011 ✭
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    Hi @eezytiger

    I have been reading many posts about how you run your system with great interest. I am a newbie to the system and trying to find my way, like many others.

    I wanted to know how you have been getting on with the latest settings of the one room acting as zone controller and the rest of the house independent.

    Also, do you close the door to this unused bedroom with a setback temperature?

    or any internal doors?

    TIA

  • eezytiger
    eezytiger ✭✭✭
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    @stevo1011 I continue to run my system with just the lounge controlling the boiler. It is set to 19C. All other rooms are set to 20C so that they are allowed to reach that high as a maximum temperature limit.

    In practice most rooms don't get all the way there, but are close enough to be comfortable.

    I have experimented with various temperature setbacks overnight - everything from turning heating off to just a 1C setback - and have settled for now on no setback at all. i.e. The lounge is set to 19C 24X7.

    I might implement a bit of setback to 16C when it gets bitterly cold and it's almost a pointless and needless battle to maintain temps +20C above outdoor temps, but for now I have no setback.

    In this way the whole system works in "low and slow" mode without the big sprint to raise temps in the morning. There are modest energy savings to be made by lowering temps overnight, but not enough, IMHO, to bother for cost reasons, maybe for comfort if bedrooms are too warm.

    Today, with overnight temps of 6C and daytime temps of 8C, the boiler flow temp has not exceeded 48C and the return has not exceeded 37C. All quite efficient for my condensing boiler.

    The system is partially balanced, with the downstairs radiators dialled down a bit and the upstairs radiators left wide open, at least until the SRTs start closing them.

    We do generally close doors to "unused" rooms, mostly out of habit, but it matters little whether we do or don't since all rooms are heated to similar temps and none are deliberately zoned down to a lower temp so none will actually chill the house.
  • stevo1011
    stevo1011 ✭
    edited January 5
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    Hi @eezytiger.

    Thanks for your update, it is always good to read about changes people make and to get the adjustments and effects of the tinkering process.

    I am currently on v3 of my set-up. 🤣

    v1 - Like most I tried each room with Tado, controlling themselves, until I realised the constant cycling from the varying calls for heat around the house. I also had the issue of one wavy line calling for heat and the boiler not responding Tado advised to start the call for heat earlier so it has ramped up to 2/3 bars by the time I want it. Not really the answer I was looking for.

    v2 - Downstairs - Lounge, diner (pretty much open plan) and kitchen linked and controlled by wall stat in the lounge. Whilst the kitchen is a little cooler it's not significant to worry about.

    • Upstairs - Main bedroom, landing and small office room (coldest room) all with Tado. 2 x bedrooms without Tado and bathroom open all the time with no TRV. This one was a little more challenging:
    • 2 unused bedrooms with dumb TRV's lowered to 1 (circa 14 deg) and doors shut.
    • Main bedroom and landing linked, landing as zone controller, set to schedule of 16 and 15 during day and night. Office set to independent at 14 deg. Whilst working from home, I turned it up to 17.
    • Problems with v2 was all about the upstairs: The office took a long time to heat from 14 to 17 and during the night the cycling from the landing and bedroom TRV were waking me up.

    v3 - Downstairs remains the same. Upstairs I have the two unused rooms the same. The main bedroom and landing are both set to independent at 20 deg as a limit point. The office is set to be calling for heat at 14 deg, when not being used with the door shut. When being used for work I tweak the temp up to 17 with the door open to suck the landing heat in as they are inevitably warmer.

    Last night I went around balancing all rads and got an average DT of 10. My WB has its own flame modulation, so I am not considering the Tado wired kit to do the modulating. Whilst the boiler isn't a fully modulating system, the savings I would make alongside the cost of the wired kit would be negligible. Flow temp set to 45.

    I will monitor this for a few days to see what happens, my main issue is that the office room Tado TRV seems to vary alongside a digital thermometer on the other side of the room, despite having changed the offset several times.

    Considerations:

    • Getting another wireless stat for that one office room to make it more consistent. It just feels a bit of a waste having it stuck in one room.
    • Getting another wireless stat and positioning it on the landing to control the main bedroom, landing and office. My hesitation here is that I only use the home office 2 days a week, the other 5 days it would be heated to 16 unnecessarily instead of sitting at the setback of 14.

    OMG when you write this out it just goes on, who would have thought heating could be so complex?

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