Every condensing boiler (that is every boiler fitted since 2005) has a sweet spot. When the water coming back from the radiators is cool enough, the boiler pulls extra heat out of its own exhaust and uses it, which is where the "condensing" name comes from. Run it too hot and that bonus heat goes straight out of the flue.
Most boilers leave the factory with the radiator flow temperature set to 70 or 80°C. Dropping it to 60°C puts the boiler in the efficient zone for most of the time it is running. Independent testing by Nesta found gas savings of around 6 to 9% from this one change, and comfort in the majority of homes was unaffected.
Is it right for your home?
Yes, if you have a combi boiler (no hot water cylinder) and your radiators are a sensible size for the rooms. The house heats up a little more slowly, which you will not notice if the timer comes on 15 minutes earlier.
Hold off, or ask us first, if:
- You have a hot water cylinder heated by the boiler. Stored hot water needs to reach 60°C to keep legionella at bay, so the setting needs more thought.
- The house already struggles to get warm in a cold snap. Undersized radiators want a higher flow.
- Someone in the house is vulnerable to cold. Comfort comes first.
How to do it
- Find the radiator temperature control on the boiler. It is usually a dial or button with a radiator symbol, not the tap symbol (that one is hot water, leave it alone).
- Turn it down to 60°C. On boilers that show a number, set 60. On dials without numbers, about two-thirds of the way round is usually close; send us a photo if you are unsure.
- Leave the room thermostat and timer as they were.
- Live with it for a few days. If a room is slower to warm than you like, nudge the flow up by 5°C.
On an Ideal Logic or Vogue, press the heating button and use + and - until the display shows 60. On a Worcester Greenstar, turn the left-hand dial (the radiator one) to the 6 o'clock position or until the display reads 60. On a Vaillant ecoTEC, press the left button under the display, then use the arrows.
While you are at the boiler
Check the pressure gauge reads between 1 and 1.5 bar when the system is cold, and have a look at the white plastic condensate pipe outside for anything that could freeze it. Both are five-minute jobs that stop the two most common winter call-outs.
How toastd can help
If you would rather we set it up, we do it as part of every service, along with checking the radiators are balanced so the lower flow still heats the whole house. Send your postcode and number and our team rings you back today.
Sources: Nesta, Money Saving Boiler Challenge; Heating Hub, boiler flow temperature guidance.