Combi boiler settings

WillyNelson · 5 Dec 2017 at 17:59

Had our boiler serviced today and I've now noticed that the boiler man set the heating temperature dial on the boiler all the way up to max. The heat has been banging out this afternoon and the boilers are scalding to the touch - which is less than ideal with a toddler about. Previously I had the setting at about 2/3 and the temp when the boiler was on was about 65C. On max the temp was up to 85C!

In my mind 85 is far too hot. I appreciate that the higher the temp, then the higher the return temp and the water can keep recirculating, thereby saving energy. But what is an ideal temperature to have the heating water set at?

Thanks in advance.

bremen1874 · 5 Dec 2017 at 18:07

I believe that if the return water is too hot a condensing boiler won't condense properly.

IIRC mine is set to 70-ish degrees but I'm not going into the loft to check.

HardwareGeek · 5 Dec 2017 at 18:22

Not a gas man but maybe he turned up to max to do a gas rate test or something and forgot to turn back down?

eviled · 5 Dec 2017 at 19:34

boilers and radiators are designed to be most efficient around 60 deg. :cool:

PiKe · 5 Dec 2017 at 19:36

You can tell if your boiler is condensing properly if the flue is puffing like a steam train when it kicks back in.

samcat · 5 Dec 2017 at 19:55

From memory there should be a 12 degree C delta between the out and the return on the boiler, so it can condense properly. If this isnt achievable then the boiler is incorrectly sized or something is wrong with your radiators.

Turn it down, rads work well about 50-60oC. Some are designed to work at much lower temp (for ASHP/GSHP systems)

koolpc · 6 Dec 2017 at 00:35

Gas guys always turn it up when servicing in my experience. I have always had to turn it down afterwards.

Felix · 6 Dec 2017 at 09:06

Mine is set to 60oC. I usally find the heating engineer puts it too high, possibly to test.

DXP55 · 6 Dec 2017 at 10:40

I set mine so I can just keep my hand on a rad - it's hot enough then.

robj20 · 6 Dec 2017 at 11:38

samcat said:
From memory there should be a 12 degree C delta between the out and the return on the boiler, so it can condense properly. If this isnt achievable then the boiler is incorrectly sized or something is wrong with your radiators.

Turn it down, rads work well about 50-60oC. Some are designed to work at much lower temp (for ASHP/GSHP systems)

The temperature of a radiator largely has nothing to do with how efficient it is, it's the room radiator Delta that's important.

The aim for efficiency with modern boilers is to have the return temperature about 55c or below.
Not all systems work the same either, mine for instance decides what flow temperature to use depending on the load so can start at 80c then ramps down to a low as 20c.
Once rooms are to temperature the flow and return are usually the same temperature, anything around 20 - 30c usually.

darael · 6 Dec 2017 at 18:32

I have to turn my boiler to 75c for the house to heat up in reasonable time. Otherwise the boiler is on for longer to heat the house up.

samcat · 6 Dec 2017 at 21:32

darael said:
I have to turn my boiler to 75c for the house to heat up in reasonable time. Otherwise the boiler is on for longer to heat the house up.

BUT you might find you use less gas doing it at a lower heat for longer...

Hedge · 6 Dec 2017 at 21:50

Stick it in the middle then adjust to suit.

Surely ideal is what you like the most?

Felix · 7 Dec 2017 at 09:04

samcat said:
BUT you might find you use less gas doing it at a lower heat for longer...

Burn at a lower flame and more efficient for longer at a lower temp or burn at full pelt at a hotter temp for shorter time...