Boiler input and output?

[Readingplumber]

Good evening all,

If I designed a heating system to work on a 20kw boiler -

Would the boilers input or output be 20kw?

Please can someone explain the meaining!

Thanks

 

[Hugh]

3.412 btu's = 1kw

 

[Plucky]

Heat input is how much energy you put into the boiler to get its output. So due to efficiency losses you might find a boiler with a 20kw output has a heat input of say 22kw. If you have sized a house and need 20kw you would be looking for a boiler with an OUTPUT of 20kw

Most boiler manufacturers quote outputs

 

[doitmyself]

If I designed a heating system to work on a 20kw boiler

That's putting the cart before the horse!

The first thing to do is calculate the heat loss from your house. The easiest way to do this is by using the Boiler Size Calculator. Manufacturers normally quote the boiler output, so you need a boiler of the size given by the calculator, or next largest.

This assumes that you have a hot water cylinder. If you want to install a combi boiler, you need to size it according to the cold water flow rate and the demand - number of taps/showers running at the same time. A combi boiler will normally be larger than the size given by the calculator, so it will be OK for heating as well.