We’ve just had a new boiler fitted (oh the excitement!) and the fitter put the temperature of the hot water as high as it goes. Is it better economically to have it like that or to knock it down a bit?

I’m not a thermodynamicist, but it seems logical to only heat the water to the temperature that you need it, Shirley?

No doubt someone who actually knows what they’re talking about will be along shortly…

but then you would use less when filling a bath / sink if it’s hotter?

depends onthe boiler.

my combi specifically states NOT to adjust the mixer valve.

the dial thermostat on the front of mines is for controllign the water going round the heating system. – the temperature of the water returning to the boiler still needs to be a certain temperature.

Time to kill until Loose Women comes on eh?

My combi has a front dial to control hot water temp. I would advise setting it so it’s not scalding.

Is this water in a cylinder or from a combi? A combi can only output hot water at about 1.2bar [or something] so if you water a shower at 40 degs and 1.2 bar you’re OK but if you want it more powerful then the boiler can’t keep up with the demand unless it’s producing water at > 40degs.

Personally though I would have thought that if you have a combi you should set it to produce water at about 40.

That said I’m not a plumber or a doctor, don’t have a combi boiler and store our hot water at about 62deg (‘cos it’s heated by spare PV generation and I’m making the most of the sun).

HTH 🙂

its a combi.

Ours (a VailLant combi) has a nifty ambient temperature scale alongside the temp. dial.

Cheers,
Jamie

Sharkbait has pressure and flow rate confused. The boiler will require a minimum pressure of 1bar or so, depending on the model, but the flow rate and temperature from the taps is interrelated win the power of the boiler and the groundwater temperature.

So setting the water temp on the boiler to max just means that you can get the most energy from the boiler – I.e. The highest temperature for the flow rate you demand for the taps.

Most combis have a flow limiter to regulate the flow rate to ensure a reasonable temperature is obtained, but the bottom line is leave the boilers hot water setting to max, and try not to be too impatient when filling a bath 🙂

My tuppence worth.

Any stored warm water should be kept at about 60-ish degrees to kill legionella bacteria.

Water then distributed at about 50 degrees and in modern regs to not exceed 40 degrees at output to baths (prevent scolding etc) achieved with trv.

40 degrees at output to baths (prevent scolding etc) achieved with trv.

What?

Forget it – it’s a combi boiler.