Turn down your boiler thermostat#
If you have a condensing boiler, then it can recover heat from the hot gases that result from burning gas or oil, but this will only work if you run the boiler temperature low enough.
Before condensing boilers, boilers were intended to run at a flow temperature of 70-80C, and many of them are still set this way. Condensing boilers can’t recover heat unless the flow temperature is around 70C or below. The lower the flow temperature (down to 45C), the better the heat recovery works.
Lowering the temperatures is more likely work with generously sized radiators, buildings with lower heat loss, and buildings that are heated most of the day rather than for individual events. If you have an older building in a reasonable state, you might get away with 60C. If you have a newer building that’s insulated, 50-55C might be more appropriate.
Be careful
If you use a hot water storage tank, you need to keep the flow temperature 70C or above to avoid Legionella. The tank needs temperatures above 60C to kill the bacteria, and there is some heat loss between the boiler and the tank.
Fan convectors usually require higher flow temperatures. This will be specified in the manual.
Is it a condensing boiler?
Condensing boilers have a small white plastic condensate pipe coming out of them, usually at the bottom. All boilers installed since 2005 are condensing.
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