Energy myth-busting: Is it cheaper to have heating on all day?

Ultrasonic

This it totally unrelated to energy saving but one reason I actually wouldn't want my heating coming on during the night is it would probably wake me up!

Thrugelmir

richardc1983 said:

Yeah I work from home so the house is occupied at 19c and then 18c when out or in bed as like a cool room at night. 

Sounds as if you just aren't active enough, too sedantry. 18c isn't cool. What tog duvet dso you have? 

richardc1983

Thrugelmir said:

richardc1983 said:

Yeah I work from home so the house is occupied at 19c and then 18c when out or in bed as like a cool room at night. 

Sounds as if you just aren't active enough, too sedantry. 18c isn't cool. What tog duvet dso you have? 

Not really I just keep the house so there are no large fluctuations in temp. When sat watching TV it's at 19c when many I know set it to 22 or 23c. Just personal preference. 22 or 23c is too warm for me. But keeping it at 18 or 19c means I dont have to turn it up. 

Ultrasonic

This may have been posted earlier in this thread but another post today made me find the following recent advice from Octopus advising setting combi-boiler heating flow temperature to 55°C:

https://octopus.energy/blog/winter-workout-gas-saving-tips/

Other advice is in line with what I actually do re. not unnecessarily heating rooms not being used, or the house at times it's not needed.

richardc1983

Ultrasonic said:

This may have been posted earlier in this thread but another post today made me find the following recent advice from Octopus advising setting combi-boiler heating flow temperature to 55°C:

https://octopus.energy/blog/winter-workout-gas-saving-tips/

Other advice is in line with what I actually do re. not unnecessarily heating rooms not being used, or the house at times it's not needed.

That’s the recommended maximum it should be set to for the boiler to give you the efficiency it was rated at. The lower you can put it the better. So try lower and find the point at which your home remains comfortable. Condensing starts at 55c. 

QrizB

richardc1983 said:

Ultrasonic said:

This may have been posted earlier in this thread but another post today made me find the following recent advice from Octopus advising setting combi-boiler heating flow temperature to 55°C:

That’s the absolute maximum it should be set to for the boiler to start condensing

Thst's not correct. Are you mis-reading the charts you posted a couple of pages back?

On that chart, "condensing mode" begins at 55C return temperature. Not flow temperature.

orrery

richardc1983 said:

That’s the absolute maximum it should be set to for the boiler to start condensing, the lower you can put it the better. So try lower and find the point at which your home remains comfortable. 

That assumes that the boiler is happy to be set at such a temperature.
Mine behaves better set at a higher temperature, then managed by a controller that uses proportional control (i.e. turned on and off in proportion to the heat required at the time). This ensures that the heating is run for the vast majority of the time with the return well below 50C and is therefore highly efficient. When the water puts in demand, the boiler runs continuously to meet it and the flow temperature is allowed to rise well above 60C to heat water rapidly and ensure that the tank is bacteria free.

richardc1983

QrizB said:

richardc1983 said:

Ultrasonic said:

This may have been posted earlier in this thread but another post today made me find the following recent advice from Octopus advising setting combi-boiler heating flow temperature to 55°C:

That’s the absolute maximum it should be set to for the boiler to start condensing

Thst's not correct. Are you mis-reading the charts you posted a couple of pages back?

On that chart, "condensing mode" begins at 55C return temperature. Not flow temperature.

I did mean return temperature so will amend my post. The recommendation is to to turn the flow temp however to 55c or lower if you can as then your boiler is likely to be running at the rated efficiency where returns are at about 38c with say 50c flow you will yet about 95% efficiency. Its seen as the best place to have it but again it needs to be a condensing modulating boiler. 

Ultrasonic

richardc1983 said:

Ultrasonic said:

This may have been posted earlier in this thread but another post today made me find the following recent advice from Octopus advising setting combi-boiler heating flow temperature to 55°C:

https://octopus.energy/blog/winter-workout-gas-saving-tips/

Other advice is in line with what I actually do re. not unnecessarily heating rooms not being used, or the house at times it's not needed.

That’s the recommended maximum it should be set to for the boiler to give you the efficiency it was rated at. The lower you can put it the better. So try lower and find the point at which your home remains comfortable. Condensing starts at 55c. 

I had understood that getting the return temperature below 55°C was beneficial in terms of condensing occurring, which is why I've dropped the flow temperature setting on my boiler. I think it's important not to overplay the very modest differences this makes though. Going by that graph dropping the flow temperature from my previous 70°C to 55°C is only likely to increase efficiency by about 5 percentage points (from about 87% to 92%). If I were to drop the temperature further to get the return temperature to 40°C or so efficiency would only increase one or two more percentage points.

As far as I'm concerned, MUCH bigger savings are to me made by people reducing how much they use their heating, through reducing peak temperatures (aim to not be cold rather than to actively feel warm), and not wasting heat on rooms or at times when it's not needed. (I know you take a different approach to the latter but I do believe you could reduce you energy use if you did more of this - at least overnight.)

richardc1983

Thank you I appreciate your input. Whilst my heating is set back to 18c overnight it very rarely comes on apart from the coldest of nights and even then my rads would feel cool too touch. I don't think I have explained before what my controls are. It is opentherm modulation so the max flow temp I have set on my boiler is the max flow temp it's allowed to go to, the rest of the time the flow temp can be down to 30c with the boiler return being about 20c. The thermostat tells the boiler what the flow temp should be and the boiler responds.

A little like you turning your flow temp down by hand and watching the temperature constantly. It does this automatically, works very well. When it comes back to the next timed period at say 0700am @ 19.5c it may for a short period up the flow temp to 40c and then when the thermostat reaches 19c it will modulate the flow temp back down. My boiler flu has no visible vapour or steam plume as it is recovering all the heat from the waste gases. 

A good analogy would be going to the coast for the day in your car. You can floor it there by driving at 80mph with a hair raising drive and get there faster but with the knock on effect being higher fuel consumption and affecting your MPG or you can take a leisurely steady paced drive at 60mph which will take you longer to get there but saving you fuel and giving you better MPG.

Opentherm (internal load compensation) and weather comp (external load compensation)  does this. It's like having cruise control it applies just enough foot on the gas to combat going up and down the hills to maintain the speed (your set temperature). Overall steady slower speed results in more comfort with less over shooting of the set temperature. 

For the last 10 years i've tried all manner of running my heating system. Timed on and off with it completely off, and for me it's better to have it set at say 18c overnight then when we are up and about it's set at say 19 or 19.5c. It barely feels on so remember this is because my flow temp is at 30c most of the time so literally just tricking in enough to maintain that temp rather than trying to raise it. 

Again I appreciate respectful and healthy debate it's how we learn by questioning and experimenting.