Hi,

I have bought a small two and a half bedroom end-of-terraced
Victorian house. It has gas central heating with a floor-standing
boiler that does the job. The boiler could be 20 - 25 years old. The
system has a hot water tank with a jacket that seems as thick as a
cardigan. The system supplies loads of hot water and some of the rads
are absolutely scorching. I'm sure the rads could do with a "re-
balance". I feel it is all very inefficient in fuel terms but it works
and will cost a pretty penny to replace.

I'm thinking about doing / getting done kitchen, bathroom and loft.

I would like to stick some "wet" solar panels on the roof, even if
they don't pay off financially, so I feel I am doing my "bit" for the
environment. OK, money does come into it - see below.

At most, the house will be occupied by one or two people. So here is
the idea. Replace the boiler with a condensing combi boiler. Then I
get hot water "on-demand" and at mains pressure. I don't heat a tank
and then let it cool for hot water I never use. I had a Vaillant combi
boiler in a one-bedroom ground floor flat and (apart from the
occasional wobbly) it would chuck out hot water at mains pressure
within seconds. I want to retain that and avoid shower pumps and
electric shower heaters.

The "clever" bit would be to have a hot water tank but only use it
for the central heating. It would have two supply circuits, one from
the wet solar panels on a south-facing roof - this would "pre-heat the
water. The second supply circuit would be from the boiler. The idea
being I could collect as much heat as possible on a sunny day on the
solar circuit and top it up with gas-heated water. The tank would need
to be well-insulated to store the heat from a sunny day and release it
in the evening.

Could such a setup be installed and would the heat gained from the
panels be worth the expense of the installation? Is there anyway of
making a rough calculation on the heat / temperature gain to work out
the money saved on pre-heating the water in the tank?

Thanks

Clive