Calculating boiler size

[topgazza]

I have been checking out the Worcester Greenstar range and whilst I will get a proper Corgi guy in to fit it I would like to know how to work out what size boiler. There are a couple of web sites that provide a calculator and they tell me around 14.5KW.

I know I can check my curent one but I have added a loft conversion with 2 rooms. The current boiler seems to cope well so I guess I could just use that size. Is it true that too big a boiler is as inefficient as one that is too small ?

Oh, I have an unvented presserised system. Does this change my type of boiler ?

 

[Paul Barker]

Most boilers can be range rated down with a pot on the pcb or by electronic controls, which your installer can enquire about from the manufacturer if he is intelligent enough.

Therefore go one size up get it ranged down, the cost difference is usually about £30.

The only proviso being that the gas pipesizing excercise has to be for the highest possible rating of the boiler. If your installer has the intelligence to pipesize.

You might wander why I am being so derogatory about installers? 1 in 3 boilers I come across were adequately sized or pipesized, and most have dodgy flue positions. But that's all about to change as off duty firemen can't get away with it any longer with notification and Rockweiler buyers solicitors.