O/T Domestic hot water temperature

[robert green]

Just had a new combi boiler fitted. What temperature should we set the hot water to? Some advice seems to be 60 degrees and then it can be adjusted with a mixer tap. It is currently at 45 which seems a bit low. What is most efficient?

[CaterBram]

Have a look at here

 

but personnally around 60 Deg C

[Roadsport06]

Mine is set to 50 degrees, we find this hot enough. Mixing it too much to cool it down seems like wasted energy. We also have little kids so don't want it too hot for them.

[richy]

Legionella - keep it above 60 at the taps.

Richy

[Burwell7man]

It must be most efficient NEVER to mix cold into hot water, so whatever is the coolest setting you and your family can withstand it going to be the best IMHO. 45 deg C sounds about the same as mine.

[Stationary M25 Traveller]

45º ... legionella multiply !! See pdf in second post.

[Frying Pan]

I asked the same question here. Ours is at around 50 degrees now and all is well with the world

[Roger Ford]

If it's a combi boiler, where would the legionella multiply? Surely that's only an issue where the hot water is stored in a tank?

[robert green]

Thanks for the replies. I did a search, but missed the previous post, so thanks for that.

 

Working on the basis that the boiler can only heat so much water at a time, it seems to make sense to have it hotter, and dilute so that two showers for example can run together. If it keeps the legionella at bay so much the better. I wasn't sure if domestic boilers worked more efficiently at a particular temperature, but it seems not.

 

Thanks all.

[Roger Ford]

Working on the basis that the boiler can only heat so much water at a time

 

A boiler can only put so much energy into water. You can have lots of water at a lower temperature, or less water at a higher temperature. I suppose there's some ultimate limit on flow rate, but generally the flow is limited by the temperature you set, if I understand correctly.

[Roadsport06]

Isn't the legionella bacteria a problem if you have a storage tank rather than heating the water that you need?

[myothercarsa2cv]

And the hotter the water is the more limescale you will get

[Pendennis]

Legionella is not an issue in a combination boiler. I won't say impossible but more improbable

The mention of Legionella easily causes excitement 😬 but in reality it is quite rare, best leave it at that

 

As has been said, lower the better. It is quite common under the renewable energy scheme to store hot water at 45C for short periods, then once a week heat it up to 80C to kill off any risk of Legionella.

Ask yourself why heat up water to 70C then cool it down to wash