My sealed thermo siphon system (20-tube panel, 168 l tank) is now up & running! Today, a day of slightly hazy sunshine all day, it achieved 50°C upper cylinder temperature (a 9°C rise) and 47°C lower cylinder temperature (a 24°C rise). And the only electricity used was in the battery-powered digital thermometers...
My thanks to the advice given by members of this forum, to A J Stone Services for supplying the main system components and much friendly help, BES for the pipe & fittings, and eBay for sundry other items (e.g. HT pipe insulation - see
http://navitron.org.uk/forum/index.php?topic=749.0)!
Fitting a thermo-siphon system meant mounting the panel on the edge of a flat roof over a sloping veranda (over the central heating oil tank!), and fitting the new hot water cylinder 1m above the first floor to get a reasonable height difference. This suited me as there’s no way I can install the panel on the main (2nd floor) roof… It also means no control system or mains wiring is required. If we went on holiday in the summer, I would just cover the panel to avoid overheating.
The system has cost a total of just about £1500, which includes some parts which I’ve yet to fit – mains pressure thermostatic shower & plumbing, hot water supply to washing machine, and a TMV.
3-D CAD model of design is (hopefully!) shown below - house wall is cut-away to show old HW tank position beneath new one (I DID cut a hole in the wall for the pipes, but it wasn't quite THAT big...!!); photo to follow soon...