Replacement boiler sizing- A bit confused!!!!

Hi,

I have to replace my conventional oil boiler asap. Its a Turco 2000 70/90 which I think is 21-26kw. I was going to replace with a new boiler with the same output but have been calculating the heat demand required using a couple of whole house boiler sizing calculators like the one linked below.

http://www.idhee.org.uk/calculator.html

This is telling me that I need a boiler output of 14.2Kw, am I missing something or was my old boiler too big?

Its for a 3 bed semi built in 2003 running 10 rads with a non ventilated 210L water tank.

Should I be looking at replacing with something like a Worcester Greenstar 12/18, don't want to order something too small but at the same time dont want something far too big.

I would say 18kW would be plenty.

Thanks for the reply Dan.

Its a bit daunting thinking about downsizing when the existing boiler was 21-26kw rated.

I guess it was over-sized when the property was built (not by me!), must have been costing me a bit in oil over the years

Providing your are using the IDHEE calculator correctly, your boiler is oversized. Common errors are no of floors and insulation.

Best way to check is to imagine how many 3kw electric fan heaters you'd have to use if the boiler went wrong. If you can get away with 3 or 4 your assessment is correct.

Worth mentioning that if you buy the boiler, it will be very difficult to get a good tradesman to subsequently fit it - and, if you go to a Worcester Bosch accredited, 7yrs parts and labour warranty is on offer.[/i]

Thanks simond, yes looks like my calculations are right.

Unfortunately I live on an island on the west coast of Scotland and will have to get a local engineer to fit the boiler, no Worcester bosch engineers up here. No problem as we have plenty of good tradesmen, unless any approved guys fancy a trip!

In theory you could get anyone to fit it and then offer a holiday to an accredited installer to commission it to get the long warranty!

Tony