Turn Down Thermostat Marital Debate!

scottishsue

How as we are trying to save costs we aare told to turn down thermostat - but which one. We have one on our combi boiler and thermostats on each of the radiators. Also I think we have a thermostat on our hot water boiler which I presume should be turned down a notch too! Settle argument

autismmum

id like to know this one too, thanks

bryanb

Turning down the radiator thermostats will reduce the max temperatures in the rooms concerned. If you turn down the water boiler one it will reduce domestic water temp. The one on the combi boiler will reduce the temp of the water circulating through the rads. (the rad stats react to air temp)

Cardew

Above(post #3) is correct.

Just adding that all boilers have an optimum water temperature at which they operate at their highest efficiency - it is normally toward the higher end of their range; but look at handbook.

Having the water temperature in the radiators hotter simply means that the room will reach the temperature set by the TRVs(radiator thermostat) quicker.
The only problem is some people don't like them too hot if they have young kids.

mech_2

Generally, lower water temperatures are more efficient, but you can't set it very low with a non-condensing boiler (ie: most boilers installed more than 3 years ago) because when the water returning from the radiators gets below around 54 degrees C, the boiler's exhaust will start to condense in the flue and corrode the inside of the boiler. That's why all the advice is to turn up the boiler thermostat to maximum. To protect the boiler, not for efficiency.

Personally I would have thought a flow temperature of 75 degrees would be fine, and unless you find you can't keep your house warm at that temperature there's no good reason to have it higher. The problem is that many old boilers don't tell you what temperature they're operating at, so setting it to the optimum temperature isn't possible. On my old boiler I used to set it to one and a half notches below maximum (out of five) on the basis that it couldn't possibly be less than 75 degrees C, but it was only a guess.

On the other hand, the new condensing boilers can be set as low as can maintain the temperature of the house. Though if heating the house from cold after a winter holiday away, you may find you temporarily have to set it higher, or the house takes forever to warm up.

As for the roomstat, obviously you can set that as low as is comfortable for you.