"Fentoozler" nospam@mapson wrote in message
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"Doctor Drivel" wrote in message
eenews.net...

"Fentoozler" nospam@mapson wrote in message
...

I saw a great set-up the other day...

Unvented cylinder, heated via solar panels (actually evacuated tubes),
which then passed through a Worcester condensing boiler for DHW.

Do you mean a combi?

The boiler simply topped up any heat demand required. The cylinder sat
at 25c even in the winter, therefore using a lot less energy to satisfy
demand. Also had an immersion in case of boiler problems.

Probably not that rare - first one I've seen though.

Not so rare. Look at the Eco-Homtec site as they have a boiler dedicated
for the task. It really improves combi performance having the inlet
raised to 25C and above. I prefer a thermal store to have the solar heat
dumped into, and a heating or system boiler heat the store. Low pressure
and faster DHW rates, if you need high rates of course, not everyone
does.

It was a combi - a great system and not overly complicated to fit either.

It has an unvented cylinder, which required an annual service, and full of
pressurised water.

I have the system you say you prefer above, evacuated tubes dumping heat
via a twin-coil cylinder (sealed for solar, open for boiler), the other
coil heated from my trusty old Glowworm BBU!

BBU? Yuk.

Gets too hot in the summer though (80c +), thinking about adding a rad and
a zone valve to dump the heat when necessary, shame to waste it though.

Excessive heat could be problematical on an unvented cylinder. What you
could do is increase the thermal store size by adding another cylinder
instead of rads. Have the return from the main cylinder run through the
additional cylinders coil and either have a shunt pump to pump from one to
the other, or use gravity. Do you have a conventional cylinder or thermal
store which instantly heats cold mains water? A thermal store can easily
store water at 95C.