Hi

I am in the process of fitting TRVs to all my rads (except the two in
the rooms where the room stats live) - and wondered if you could help
with a question about my current boiler. I thought it was a 'gravity'
system.

I have put some photos of it here (when the server will let me upload
them anyway!)

http://www.thehawthornes.org/the_lodge/boiler_room.htm

The system is set up in such a way that I can eithe rhave hot water
on, or heating and hot water - I can't just have heating. I have also
noticed that when the room stats have reached the set temperature, and
close the zone valves, the pump still works. Is this normal? Where
is the water going?

There is also green marks on nearly all the soldered joints between
pipes - is this normal?

I am in the process of designing a new CH system - but in reality, it
is probably 6 months away yet - one that will cope with a loft
conversion, and about 10Kw of extra rads (in a barn that is attached
to the house) - so am not about to do anything drastic.

Thanks in advance

Simon