"Simon Langford" wrote in message
om...
Thanks for all the replies and help everyone. I think I'm getting
somewhere now. I screwed down all the radiators and towel rails apart
from the top floor and ran the boiler for 30 minutes. Sure enough the
top floor gets nice and hot.

Then I opened up the ground and first floors just a little bit, until
some warmth came through. This morning when the heating came on,
everything was nice and warm.

When I checked the pressure in the system before forcing the heat up
to the top floor, it was at 1 bar. After getting the top floor hot it
was down to almost zero, so maybe there was a blockage somewhere which
has now been shifted. I'm going to do a proper bleed tonight, and
might get myself a digital thermometer as recommended here, to do a
proper balance.

I'm still pretty sure that the boiler runs flat out (i.e. never cuts
out under its own thermostat). It is quite a large house, especially
the ground floor which is more than twice the area of the other floors
and has some very high ceilings. So maybe a 24KW boiler is only just
up to the job? We're about to remove a large radiator from the
kitchen and put a wood burning stove in its place, so that might help
the boiler load. (I know the kitchen will be colder when the stove's
not lit...)

Anyway, thanks for all the help.

Simon.

If the boiler is borderline install extra insulation in the loft. Then go
around with a silicon gun and get rid of air leaks.