Simple combi boiler question

[danny0001uk1]

Hi All,

My boiler is 35kw rated.

Does this mean it uses 35kwh of gas if the dial is on its max temperature of 80c

Or does setting the boiler at 50c use a lot less than 35kwh

Hope this makes sense!

[jonwm]

They all modulate nowadays, would probably only get near 35kw if hot water was being demanded at a quick flow.

I have a system boiler and it's 18kw rated as it doesn't need to heat on demand

Only my thoughts from reading about different types of systems / boilers, could be totally wrong.

[shambolic]

Also bear in mind that a 24/30/35 combi is the heat output to HW. Most of them are 24kw to heating. Which is far far too much tbh. They do range rate and modulate down but it’s far too much.

[K87]

I understood that the kW rating was like having a larger engine in a car, it had more power to heat larger houses, a 35kw boiler would be good for 10 to 15 radiators,

I hope that your logic is correct in that turning the temperature down on the boiler reduces costs, 50 on the water produces the perfect shower temp without adding any cold water.

The Ideal Vogue website is useful in terms of answering questions such as this.

[Pobolycwm]

The short answer is you will use less energy but likely have a colder house, the radiators will run at a lower temperature.

There are some things that will influence this, size of radiators and pipework, large radiators with large pipework will be better than small radiators with small pipework, with large radiators you can get more heat out.

If you have a standard hot water cylinder heated by the boiler your hot water will also be less warm

There may be issues with the boiler firing up too frequently and for too short a time as the temperature range between off/on is too narrow

There's several things you can do with radiator thermostats, system thermostat and hot water cylinder temperature that will save money , namely turn them down

Running the boiler at max temperature will be a bit more costly than running it at say 3/4 as you will be heating water up to a temperature higher than you need with some corresponding system efficiency losses