when u purchase a boiler it will have a model no and in there will be two digits this is the boiler output. ie worcester 30si is 30kw. worcester 25si is 25kw etc. this is the max rating the boiler can produce in central heating. u can add the total output of all the rads to see how much u need.
kash
March 2013
It means the power in kW (kilo Watts - a unit of energy)
Modern boilers are 90% or more efficient - they convert most of the input energy to heat - (heated water) the output. Old boilers can be as low as just 75% efficient.
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