What is best central heating temperature?

Chenbas27 · 5 December 2019 at 11:58PM

Hi,

I have a baxi 400 combi boiler. For my radiators to heat up properly, I have to set the temperature to about 50 degrees. I was googling what temperature central heating should be set at, and it says about 21 degrees for thermostats, but then I've seen other sites saying the boiler should be 60-70 degrees.I'm confused.I want to be fairly warm, but not be paying too much.

Advice welcome, thanks

Ebe_Scrooge · 6 December 2019 at 9:37AM

A couple of things. First, we are talking Centigrade rather than Fahrenheit, yes ?

Second, be aware that there are 2 temperatures you need to consider. The central heating temperature is usually controlled by a thermostat in the house somewhere, and round about 21 degrees is generally reckoned to be a comfortable temperature for most people.

But the boiler also heats the hot water in your tank (unless it's a combi). The hot water is usually stored at somewhere about 60 degrees - I forget the exact figures, but much lower than that and you run the risk of Legionella bacteria living in there (in theory, at least. In reality the risk is very low unless the water is sat there unused for a long time). That's usually the recommendation, anyway.

All heating systems vary in their design, but that's the basic principle. I'm guessing that the temperature control on your boiler is the hot water temperature, the room thermostat should be the central heating.

If you've got the thermostat set to 21 and the house is cold, you need to do a bit of investigation. It could be something as simple as the radiators need bleeding, or they could be sludged up - either is very easy to fix. Failing that, the thermostat could be faulty - you could try to sort this out yourself, but unless you're fairly confident in what you're doing, you're probably best getting a heating engineer to have a look for you.

Anyway, hope this helps a bit :-)

matelodave · 6 December 2019 at 5:07PM

50 degrees or lower is probably too low unless you've got oversized radiators or underfloor heating. Set you boiler to around 55-60 and the room stat to 21.

The room stat controls the room temperature by switching the boiler on and off whereas the boiler stat controls the temperature of the water flowing through the radiators. However, if the flow temperature is too low then the rads wont get hot enough to warm the room in a reasonable time or even not enough for the room temp stat to control the boiler so it could end up running all day with lukewarm radiators.

The ideal boiler temp is around 55-65 degrees but you need to experiment a bit to decide what suits your particular configuration and lifestyle.

If you want a quick warm up say for an hour in the morning and a couple of hours in the evening then you need a high flow temp however, if the heating is on most of the day then you can usually get away with it being a bit lower

Rodders53 · 6 December 2019 at 5:16PM

Baxi 400 Combi boiler https://www.baxi.co.uk/our-boilers/combi-boilers/baxi-400-combi . So no hot water storage / temperature issues.

The boiler has user controls for both CH (25 to 80 C) and HW (35 to 60 C) in any case.

CH circulating water temperature and flow rates should be set to get the correct temperature drop on the radiators in->out pipes...

The radiators are designed/specified to give designed heat outputs with a flow water temperature difference of 30, 50 and 65. Now assuming a room is at 20 C you'll see the input flow would need to be at 50, 70 or 85 C to achieve those radiator heat output numbers.

There's no specific correct answer - other than that of the system designer/installer, who w(sh)ould have done all the heat loss calculations for the rooms, sized the radiators and specified the water flow temperature and rates. That data is seldom provided to the end user.

BUT the lower you can run the boiler CH flow at then the cheaper it will be to operate (probably), albeit it may take a bit longer to get the home up to an acceptable temperature from 'cold'. It may also not be able to keep the rooms warm enough on the coldest of days, so need increasing. (Some boilers have a 'weather compensation' system to automatically lower temps when warm outside and higher when cold.)

AIUI lower temps will also help the boiler to be in the more efficient condensing mode.

It's a suck it and see / trial and error situation. Adjust it higher and lower and see the effect on comfort for your use of the system.

coffeehound · 6 December 2019 at 5:25PM

A key factor is the construction of the house. Brick/stone walls and concrete floors take far longer to warm up than modern dry-lined plasterboard walls and suspended wooden floors.

Another factor is whether you are at home during the day or not.

Depending on these, running the radiators warm 24 hours a day, or having them hotter for short periods will make more sense accordingly.

I find radiators run just warm most of the time, aiming for an air temperature of 19 to 20 C is the most comfortable and doesn't cost too much.

Fly100 · 27 April 2020 at 10:52AM

I would suggest taking some temps, the lower you can run the flow temp is better as a rule. However, you need the return temp to be lower than 47C ( ish). This will allow the boiler to Condensate and recover any exhaust heat. There is of course a consideration the boiler may have a min temp it runs at. I would suggest 50C is on the low side.

What is best central heating temperature?

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