My boiler was set to heat my radiators to 75 degrees. When I had my annual check done, the engineer said it should be set to 60 degrees because that is a more efficient temperature.
What I don’t understand is why is that more efficient in the long run. Yes, the water is heated to a lower temp saving fuel, but now I have to run the heating for longer to get the house warm. Does having the heating on for longer not just cancel about any benefit from lowering the flow temp?
In: 8
Boilers always waste some heat through the exhaust, because for example if the water temperature coming in is 100F, your exhaust temperature cannot be lower than 100F.
If you run your boiler at a lower temperature and the water coming in is 80F, you can cool your exhaust to a lower temperature, meaning you transfer more heat to the water. Your system is more efficient. That’s why it’s better to use a lower temperature for longer than a high temperature for a short amount of time.
This is even more true for modern boilers that try to extract the last drops of heat from the exhaust by condensing the water vapor it contains: there is a lot of energy you can extract this way (because water vapor contains a lot of energy, that’s why it takes ages to boil water away on a stove), so if your incoming water is too hot you’re wasting even more energy.
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