over speccing a boiler?

[rocketchunk]

I don't trust my baxi pf40 to last another winter so am going to replace it with a new Worcester (conventional) boiler. I've taken off all my rads today and am going to replace them (and most likely the pump & 3port valve too). The new rads will have a total btu around 28k and with the hot water aswell I was thinking a boiler with output around 50k btu would be more than adequate for day today use. Is there any merit in getting one with a significantly higher output in the hope of it being understressed and more likely to last or does this kind of thing not really apply with boilers? I'd like to know myself before my gasman comes around later in the week. Many thanks in advance for any advice.

 

[dcawkwell]

No. You need to use a boiler sizing calculator available on the net.
Unlikely you will need anything bigger than 24kW for house heating.

 

[D_Hailsham]

No. You need to use a boiler sizing calculator available on the net.

This is a good one: Whole House Boiler Size Calculator.

Next, calculate the heating requirement of each room. You can go the whole hog and use a heat loss calculator, but a quick and dirty method is to apportion the boiler output to each room by floor area.

You now need to check the outputs of your rads, which can be done by using the info in Stelrad Elite Catalogue. (Rad outputs are very similar irrespective of manufacturer, unless you have designer rads. )

Ideally the rad output should be about 20% greater than estimated as this allows the boiler to run at lower temperatures, which saves money.

This does NOT mean you have to install a boiler which is 20% larger.