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Energy myth-busting: Is it cheaper to have heating on all day?
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The bit in bold negates your whole argument. You said it yourself, you save by turning the heating off overnight.My 2p.
The ask jeff article does make claims which are not backed up with studies. However, it is not an unreasonable argument. Wet bricks and wet cavity fill would be more conductive of heat than when dry and houses produce a lot of water vapour some of which escapes through the walls. My gut feeling is that water vapour isn't enough but that's just my gut I've no facts to back that up either way.
National trust did some tests in one of their properties and found their cost of heating was lower when it was on low 24/7. That could be because the walls stayed dry. Equally it could be because running low is more efficient that running high, especially on a condensing boiler where the difference is at least 10%. For dense property, which all National Trust places would be, the difference between 24/7 and broken running is a ~5% saving which hence would gave a saving on 24/7 running.
Turning off radiators in unused room is dubious IMO. The insulation in a house is in the outside walls. There is no insulation between rooms and of course air freely moves between rooms. Turning off a radiator in a room just reduces the radiator surface to heat the house. The unheated room is getting heat from the heated areas of the house. It has to be unless it is at outside temperature, i.e. middle of winter, -1C outside, -1C in unused bedroom, ice on the walls.... Doesn't happen. Turn the rad down by all means but keep it sensible, say 18 or 16C, warm enough to keep condensation at bay and so that there isn't too big a difference to the rest of the house. Otherwise that room will be sucking heat out of next door rooms since houses do not have insulation between rooms. The issue in reducing the rad area is that you make the remaining radiators work harder so hot so less efficient with a condensing boiler.
What most people fail to realise is that everyone is in fact heating their house 24/7. Take a house a 20C, outside is 0C. You turn the heating off at 10pm. Does the temperature drop to 0C? No (unless you live in a tent). What happens is that the house temperature slowly drops overnight to maybe 16C by morning. All through the night heat has been leaking out of the house. That comes from the structure of the house. The next morning when turn the heating on you put that lost heat back into the structure. The overall energy usage is similar, you save a bit overnight because the average temperature is 18C (20C->16C, avg 18C), rather than it being kept at 20C. The downside is that you have to make the heating work harder so it is less efficient.
The bit after about the heating 'working harder' is twaddle, my heating doesn't work any harder than I let it, and mine is set to a level where it is always in condensing mode.
I know you think people struggle, but no advocate of timed heating (as opposed to 24/7 heating) does. They understand perfectly, and they are saving money because of it.I know people struggle with this let me give another analogy. <snip pointless analogy>0 -
The bit after about the heating 'working harder' is twaddle, my heating doesn't work any harder than I let it, and mine is set to a level where it is always in condensing mode.
No, it isn't twaddle. Yours maybe, if you understand it well, but I suspect most people don't.
My heating will run for about 40 minutes before the return water is hot enough to cause the boiler to start to modulate i.e. the flow is about to go over-temperature. Once the boiler modulates, you can kiss goodbye to condensing mode, as the return water simply increases rapidly in temperature - not easily visible unless you find the hidden option to display it on the boiler (requires manual in hand) or strap a thermocouple to the return pipe.
The only way it can be tamed and kept in condensing mode is for the controller to enforce a proportional control regime - turning the boiler on and off so that it never gets into modulating. Proportional control doesn't usually start until the room temperature is approaching target - within about 1C.
I'd regard my system as being pretty typical of most systems out there.4kWp, Panels: 16 Hyundai HIS250MG, Inverter: SMA Sunny Boy 4000TLLocation: Bedford, Roof: South East facing, 20 degree pitch20kWh Pylontech US5000 batteries, Lux AC inverter,Skoda Enyaq iV80, TADO Central Heating control0 -
If your return temperature is increasing 'rapidly' then turn down the output until the return is low enough to keep it condensing. The return is only increasing because your rads can't shift the heat fast enough, or your house is already warm enough.No, it isn't twaddle. Yours maybe, if you understand it well, but I suspect most people don't.
My heating will run for about 40 minutes before the return water is hot enough to cause the boiler to start to modulate i.e. the flow is about to go over-temperature. Once the boiler modulates, you can kiss goodbye to condensing mode, as the return water simply increases rapidly in temperature - not easily visible unless you find the hidden option to display it on the boiler (requires manual in hand) or strap a thermocouple to the return pipe.
The only way it can be tamed and kept in condensing mode is for the controller to enforce a proportional control regime - turning the boiler on and off so that it never gets into modulating. Proportional control doesn't usually start until the room temperature is approaching target - within about 1C.
I'd regard my system as being pretty typical of most systems out there.
Regardless, the stuff about the boiler running a bit harder in the morning is never going to be enough to cancel out a whole night of wasted energy heating rooms when people are tucked up asleep.
If you left your house unoccupied for a year, would you leave the heating on? After all, if you let the house go cold for a year the boiler would have to work quite hard to bring it back up to temperature when you returned.
Probably cheaper to leave the heating on I think. :rotfl: 0 -
Regardless, the stuff about the boiler running a bit harder in the morning is never going to be enough to cancel out a whole night of wasted energy heating rooms when people are tucked up asleep.
If you left your house unoccupied for a year, would you leave the heating on? After all, if you let the house go cold for a year the boiler would have to work quite hard to bring it back up to temperature when you returned. Probably cheaper to leave the heating on I think. :rotfl:
I have used this analogy many times on this forum.
People attempt to use the same argument(i.e. constant heating) for Hot Water tanks. i.e. it is cheaper to keep hot water on all the time because if you have timed heating, the boiler will have to work harder and use more gas/electricity/oil than it would to keep the water at a constant heat.
Surely nobody, but nobody, would argue that leaving the heating off for a year, and then bringing the house back up to a set temperature after a year, would use less energy than keeping it at that set temperature for the whole year.
When the heating is left off for that year, the laws of physics determine that the rate of heat loss from the house decreases as the house cools and will be zero when the inside and outside temperatures are equal.
So if we agree the 'one year heating off' analogy, at what point do the laws of physics not apply? one month? 1 week? one day, one hour?0 -
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If your return temperature is increasing 'rapidly' then turn down the output until the return is low enough to keep it condensing. The return is only increasing because your rads can't shift the heat fast enough, or your house is already warm enough.
No, I don't subscribe to the 'leave your heating on' notions.
As for turning my boiler down, this is one of those "In theory, theory and practice are the same, but in practice they're not". Firstly, you need to keep the boiler temperature up to heat water above 60C, and to heat water (and the house) fast enough.
In addition, the boiler behaviour may not be quite what you imagine. If the flow is set to 60C, then typically the return is 40C (on mine at least) which is fine. As TRVs start to close, the flow is restricted and the return temperature starts to increase - eventually the boiler modulates to hold the flow to 60C until it hits the maximum modulation (about 5kW on mine) - at this point the boiler allows an over-temperature of 7 degrees i.e. 67C flow, about 57C return and then shuts down. Far better to have the boiler flow temperature at about 68C, giving more rapid response to heating demand and allow the controller to manage affairs using proportional control. With proportional control, the maximum on time is about 45 minutes and it takes about 40 minutes for the boiler to reach 68C flow, which will be 48C return at full power which is fine, and is a far better all round strategy for economic running., but this will obviously depend on how clever your controller is.
All in all, I find turning the boiler down to be least effective strategy.4kWp, Panels: 16 Hyundai HIS250MG, Inverter: SMA Sunny Boy 4000TLLocation: Bedford, Roof: South East facing, 20 degree pitch20kWh Pylontech US5000 batteries, Lux AC inverter,Skoda Enyaq iV80, TADO Central Heating control0 -
Quite right, thank you. That is why I want more discussion on efficient use of renewables.
Which part of reliable renewable's produce constant base load grid-managed power is efficient ?Disclaimer : Everything I write on this forum is my opinion. I try to be an even-handed poster and accept that you at times may not agree with these opinions or how I choose to express them, this is not my problem. The Disabled : If years cannot be added to their lives, at least life can be added to their years - Alf Morris - ℜ0 -
Richie-from-the-Boro wrote: »Which part of reliable renewable's produce constant base load grid-managed power is efficient ?
A bit off topic for this forum, but grid level or home batteries charged from renewables (solar, wind, biomass - whatever is plentiful at the time) would be extremely efficient. We know from studies conducted in Germany that we could make the switch to entirely renewables if we get our ourselves into gear.4kWp, Panels: 16 Hyundai HIS250MG, Inverter: SMA Sunny Boy 4000TLLocation: Bedford, Roof: South East facing, 20 degree pitch20kWh Pylontech US5000 batteries, Lux AC inverter,Skoda Enyaq iV80, TADO Central Heating control0 -
So what's the definitive, laws-of-physics-abiding solution?
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No, I don't subscribe to the 'leave your heating on' notions.
As for turning my boiler down, this is one of those "In theory, theory and practice are the same, but in practice they're not". Firstly, you need to keep the boiler temperature up to heat water above 60C, and to heat water (and the house) fast enough.
In addition, the boiler behaviour may not be quite what you imagine. If the flow is set to 60C, then typically the return is 40C (on mine at least) which is fine. As TRVs start to close, the flow is restricted and the return temperature starts to increase - eventually the boiler modulates to hold the flow to 60C until it hits the maximum modulation (about 5kW on mine) - at this point the boiler allows an over-temperature of 7 degrees i.e. 67C flow, about 57C return and then shuts down. Far better to have the boiler flow temperature at about 68C, giving more rapid response to heating demand and allow the controller to manage affairs using proportional control. With proportional control, the maximum on time is about 45 minutes and it takes about 40 minutes for the boiler to reach 68C flow, which will be 48C return at full power which is fine, and is a far better all round strategy for economic running., but this will obviously depend on how clever your controller is.
All in all, I find turning the boiler down to be least effective strategy.
We need to be careful that we are comparing apples with apples here. I have a modern condensing boiler set up for HW priority controlled by Evohome/Opentherm. My boiler has a TSet max profile of 70C and heating is currently set manually to 65C.
Whenever hot water heating is required, Opentherm will request 92C which is limited to 70C by the boiler. The boiler will slowly heat up to 70C. My hot water is controlled in a 60 to 55C range.
When one of the 12 heating zones demands heat and the range is out with +/- 1.5C of the zone target temperature, then Opentherm will gradually build up the boiler temperature to 65C - adjusting to maintain a 20C return difference.
Once all 12 zones are within their target range, the boiler audibly closes down. On the one Or two cold mornings that we have had this season, I have come down and seen boiler return temperatures of 40 to 44C.
In sum, the Opentherm/Honeywell logic is to get the system up to temp ASAP and then adjust to keep it there.
The above is not to suggest that cost/efficiency can be improved by having the heating on 24/7.This is a system account and does not represent a real person. To contact the Forum Team email forumteam@moneysavingexpert.com0
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