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Thread: Living room temp at night

  1. #11
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    Quote Originally Posted by olektrolek View Post
    this might provide false impression of making savings on heating because is off over night, but sometimes bringing the temp back up will cost more than just keep maintaining bit colder over night...

    This is absolutely never the case…

    Imagine your room as a box and your heat as energy. If energy is escaping the box you need to supply the equivalent amount of energy to maintain a consistent temperature. Let’s say 10 units of energy escape over an hour period. If you didn’t provide any energy to the box for one hour, in the next hour you would need to provide 20 units to get back to the same temperature - exactly the same amount as you would have used to maintain a consistent temperature.

    The issue you have is that the heat loss from a house is directly related to the inside vs outside temperature differential. The higher the differential the higher the heat loss. As such it will always be more effective to turn the heating off and then reheat the room. Even if you had perfect insulation you would only ever use the equivalent amount of energy.

    Obviously boiler efficiency and running in condensing mode plays a part in this but in most homes heat loss at higher temperature more than exceeds the efficiency gains from a boiler ticking away under opentherm control whilst condensing

  2. #12
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    Ive seen this info but i dont think its correct.

    When the livingroom for example will cool down to 15c, the boiler will need to work on 100% ch demand for good 2 hrs or longer (depending on factors) to heat up the room to 20c again in the morning.

    If the livingroom is small it may work but for my openplan it takes to long to heat up in the morning.

    I suspect everyone circumstances may be different, in my opinion at least for me 2c lower for night works the best. But i will try to do some more testing 😀

  3. #13
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    I always "love" this thread theme as every time it comes up (on a regular basis ) there are so many opposite views - lol. Hence why I said a detailed parallel test would be great to put this to bed once and for all
    The "bit" that always nags me about the theory is that if we just consider the air in a room then absolutely it doesn't make a difference whether I heat from cold or maintain a temp, the energy used for the period of heating must be identical as per MajorDanby post. However, if we now add in thermal mass heating ie the heat required to raise the walls, furniture etc so that they become heat emitters (ie mini rads) rather than heat consumers (emitting cold and making the room "feel" cold), then that is the bit that I wonder whether there is an advantage in keeping the room at a higher constant temp (Unless in a highly insulated property with very low thermal mass requirements) so that the room "feel" factor is constantly maintained. I appreciate that this "feel" factor is somewhat unscientific and so on pure energy and temp I expect MajorDanby post and Killa47 Martin Lewis reference are, in absolute energy terms, the “facts of the matter”

  4. #14
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    Quote Originally Posted by olektrolek View Post
    this might provide false impression of making savings on heating because is off over night, but sometimes bringing the temp back up will cost more than just keep maintaining bit colder over night...
    Quote Originally Posted by SteveP View Post
    I always "love" this thread theme as every time it comes up (on a regular basis ) there are so many opposite views - lol. Hence why I said a detailed parallel test would be great to put this to bed once and for all
    The "bit" that always nags me about the theory is that if we just consider the air in a room then absolutely it doesn't make a difference whether I heat from cold or maintain a temp, the energy used for the period of heating must be identical as per MajorDanby post. However, if we now add in thermal mass heating ie the heat required to raise the walls, furniture etc so that they become heat emitters (ie mini rads) rather than heat consumers (emitting cold and making the room "feel" cold), then that is the bit that I wonder whether there is an advantage in keeping the room at a higher constant temp (Unless in a highly insulated property with very low thermal mass requirements) so that the room "feel" factor is constantly maintained. I appreciate that this "feel" factor is somewhat unscientific and so on pure energy and temp I expect MajorDanby post and Killa47 Martin Lewis reference are, in absolute energy terms, the “facts of the matter”
    The energy considerations are the same from a thermal mass perspective as well as air temperature. There will obviously be a greater lag to those elements heating up however. Couldn’t possibly comment on feel however 😂

    Just as an aside - my rooms ‘feel’ hotter when at 19degree and still heating to 20 rather than stable at 20 because the radiators are cooler when maintaining a temp

  5. #15
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    Quote Originally Posted by MajorDanby View Post
    Just as an aside - my rooms ‘feel’ hotter when at 19degree and still heating to 20 rather than stable at 20 because the radiators are cooler when maintaining a temp
    Absolutely agree - thats why sometimes I turn the boiler down so that rooms take much longer to reach temp as even though at a lower temp they "feel" warmer as the rad is still going Makes sense but doesn't help the cause of a smart heating system simply trying to maintain a room temp !!

  6. #16
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    Have to agree with MajorDanby. The physics is clear, heat loss is proportional to temperature differential, so for economy turn off when not required. No ifs, no buts.

    Perceived comfort is a different matter and some people may not feel comfortable until the thermal mass has stabilised at the required temperature. Thus for comfort, they may prefer to maintain a higher base level of heating, even though it uses more energy overall.

    Just to be pedantic (there’s always one) an object cannot emit cold, only absorb or emit heat. Although of course, it feels as if cold is being emitted even though in fact heat is being absorbed. Sorry, I will shut up now.
    Last edited by CT1; 7th December 2021 at 03:21 PM.

  7. #17
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    Quote Originally Posted by Mid112 View Post
    Hello,

    Whats everyone view on a temperature of a living room when unused at night?

    I was keeping it at 18C at night, i think if i go lower takes too long to the living room to heat up in the morning.

    Cheers
    Tend to let the temperature drop downstairs as it wants - never gets much below 17C though except in really cold weather. Wouldn't like it to get much below 14 C in fact for no really good reason except that I have a uninformed worry that too much temperature cycling is not good structurally ( I know it sounds crazy ).

    In fact, due to mobility issue, we spend most time upstairs so rapid heat up in the morning isn't a issue for us.

    Been researching smart heating and certain to install Evohome sometime soon. Interim, I spend a lot of time tweaking the Danfoss TRV's to get, 18-19 downstairs in the day and about 21 upstairs. We just have three zones d/stairs: lounge/diner, kitchen and hall - the hall is odd in that it is always warm since it has the bypass rad in it ( always on - no TRV ).

    Def. need to get a grip on the heating especially with the hikes in prices.

    On fuel economy, it definitely saves money reducing any temperatures you can - its just physics ( I was/am involved with heat transfer in electrical machines and their enclosures ). Its interesting that the same question keeps coming up in camper/motorhome forums - the answer is the same - reduce heating if you can - only heat water when you want it - if your aim is to save money. I don't like the cold though so we have to pay for the extra heat.

    richard
    Last edited by rd99; 10th December 2021 at 10:37 PM.

  8. #18
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    I suppose this will mostly depend on how much heat the boiler can generate. In my case I am on city heating and that is practically unlimited heat supply. In the cold season I heat the children's bedrooms when they go to bed and at wakeup time and it takes only about 10-15 minutes of heat demand to get the rooms from 15 to 19 using a standard rad.

    In the living room we have UFH. The floor itself is a mix of styrofoam and cement, I think some 50cm thick, this is standard building method in The Netherlands. Normally this is topped with some 10cm of cement but in our case we first have a heat reflective layer and the UFH tubes and then the cement top. Prior to getting Evohome we never witnessed the room dropping below 16C and that is what I set as the `not in use` temperature and I actually have that set from 9:00PM already.

  9. #19
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    I drop mine to 16oc at night, which it very rarely gets to. I usually sits at around 18/19oc at night. It is a very well insulated house though.

    I've actually done extensive testing with ours, and it's cheaper to leave the heating on all day in an unoccupied house than just morning/night timings. I'm actually going to go one step further to test if it's cheaper to leave on 24/7 (Which I suspect it might be). However like I said, we've got really good insulation and triple glazing so the heat loss is very minimal.

  10. #20
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    My heating is set to 10c overnight with the main bedroom and living room only set to come on at 06:00 at 19c. During winter months over night the rooms drop by about 5C from what they were when we go to bed. A little more if the outside temperature drops very low but even when outside is -1C the rooms overnight only drop to 14c or thereabouts. Thus set at 10c nothing comes on. When it does come on the chill in the air goes within 30 minutes and some heat can be sensed even if the room is not up to temperature. I never use optimisation as it always seemed to bring the heating on too early. A waste.

    I was away from home recently for 2 nights and switched it all off. Monitoring it from afar the whole house equalised in temperature and all rooms were reading about 12c on the third day with an outside temperature of 5C.

    What I notice with OpenTherm in operation is the boiler flow temperature starts at 70c but once up to temperature or near to it, it steps back. I often notice the flow temperature just below 40c with everything at it’s set temperature. Usually about 38c.

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