Can I down grade when changing to a condensing oil boiler?

[mrlapou]

Our very old open flue oil boiler needs replacing. It's rated output is 28~32kw. Prob a Band 'F'.

An installation engineer came round and he mentioned since new boilers are more effiecient I could consider going down one size in burner output to something like a Worcester Bosch 18/25. That'll save oil? I'm not sure I agree as total of all rads rated output, add up to 27KW (2 x 3kw rads added at a later time since old boiler installed). Figures exclude the HW coil.

Is the gfuy correct?

 

[oilman]

You need enough heat for the losses in the building, not just because the radiators can handle that much. If you have 28mm pipes you can handle 20kW and less if its 22mm. You will probably save some oil, but because the boiler is inherently less wasteful, not because it is condensing. Strapping a condensing boiler into an old system is not much good, but the politicians say you have to have a condensing boiler.

I definitely would look at something other than a Worcester Bosch as their warranty service is pants. Try Grant.