Money Saving Boiler Challenge - Turn down boiler temp to save money and energy waste

nightsky224

Money Saving Boiler Challenge to encourage people to turn down their boiler temps to save £££ and energy waste.
https://moneysavingboilerchallenge.com/

Easy to follow, step by step instructions. 

(Only for combi boilers)

FreeBear

Why should it be limited to combi boilers ?

A condensing system boiler would surely still benefit.

dunstonh

FreeBear said:

Why should it be limited to combi boilers ?

A condensing system boiler would surely still benefit.

Possibly worried about liability should people drop it below 60c.  Water tanks are at risk of Legionella if the temperature is not kept at 60c or above.  Some may need a bit more if the outlet point is further away from the tank. 

nightsky224

FreeBear said:

Why should it be limited to combi boilers ?

A condensing system boiler would surely still benefit.

I believe it's because reducing the temp of heat-only (regular) or system boiler system reduces water temp as well as radiator temp which isn't the case with combis. Reducing your hot water temp carries Legionella risks.  
More info here https://www.which.co.uk/news/article/one-simple-way-to-adjust-your-boiler-to-lower-your-heating-bill-atXmR3z2RY92

FreeBear

nightsky224 said: Reducing your hot water temp carries Legionella risks. 

Some 250 cases of Legionella reported annually. Of those, about half are contracted overseas. The risk of catching Legionella in this country is extremely low. Yes, maintaining a water temperature of 60°C will kill the bacteria within minutes, but so will a water temperature above 50°C (it just takes a little longer).

Miser1964

I hope this gets picked up by the media, it's exactly what JRM was going to spend £15M of taxpayers money on!

Glum

For those with a regular back boiler, it seems that it might be more efficient to turn the boiler temperature up to almost maximum (in winter). It sounds illogical but I assume that if the radiators heat up faster, the room stat switches the boiler off a bit sooner and the pump stops using power. Conversely, a cooler boiler might struggle to get the house warm enough to trip the room stat, so the boiler and pump are running for longer. By way of an example, old GlowWorm back boilers had a recommended boiler temp of 180°F or 82.2°C.

I would appreciate any comments. Let's assume that TRVs are not fitted. Is there an efficiency saving?

Miser1964

>For those with a regular back boiler,..<

If it was installed before 2005 when condensing boilers were mandated, then quite possibly what you say is correct. Dropping the output flow temp may just make the house cold with no benefit in efficiency if the boiler has no condenser. 

[Deleted User]

This is the reason, condensing boilers work more efficiently at a lower return temperature, 55C is the maximum for it to condense giving about 87% efficiency, but get that return temp down to about 30C and you are getting 95%+ efficiency.

The thing is it is too complicated to get folk to measure their return temperature, so easier just to tell people to reduce the outflow. As per the graph below, the boiler will get more efficient so nothing to lose in turning down the outflow. 

Turning the outflow down to 60C should pretty much guarantee the return will be 55C or lower so it is a great starting point, but if you can get away lower then go for it. I have my outflow set to 50C and typically the return temperature is around 30-35C giving me about 92%+ efficiency.

[Deleted User]

Most modern boilers will also tell you the return temperature, here's mine, I just switched the heating on for you MSE'rs even though I don't need it (9C outside) just to show you this:



Note that the return flow temp isn't always going to be precisely the same, so when you first turn your heating on it will be really low as most of the heat will be warming the radiators, but as they reach temperature the return will rise. The above was after the heating was running for about 10 mins.

Smart boilers/thermostats will knock back the flow temperature as the house reaches the set temperature (opentherm), I've seen mine drop the outflow to 40C as the house reaches normal temps and the TRV's are starting to close off resulting in not as much difference in the return temperature.

BUFF

May I ask what boiler that is?