On Mar 11, 9:34*pm, "Triffid" wrote:

There is now no float valves to stick or go wrong in the loft, no chance of
any leaks or bursts in the loft, no motorised valves in the system to stick
or go wrong.

If you are going to draw comparisons you need to be thorough on both
sides. You have omitted the potential issues you may face with the
secondary heat exchanger and diverter valve that the combi introduces.
Also, the lack of any backup hot water availability should the boiler
breakdown.

If I had the choice of fixing/replacing a motorised valve in an airing
cupboard or a diverter valve inside a boiler I know which I'd
prefer... ;-)

Besides which, you really ought to be comparing against a modern
unvented cylinder as these address most of your concerns about
'conventional' systems - heat loss, flow rate, pressure, float valves
etc.

Mathew