On 30 Mar 2007 02:16:52 -0700 Jives11 wrote :
So how do solar hot waters heat the water ? Is there a secondary coil
in the hot water tank, through which the solar heated water is pumped

This is the preferred method, though you can put s pre-heat cylinder in
the existing cylinder feed

OR do they raise the temperature of the water in the storage tank.

No, partly for the reason you give (legionnaires), also because there
is potential for this water to become dangerously hot and it is being
fed to uncontrolled places (e.g. basin 'cold' taps), also a plastic
cistern full of very hot water is not a good idea.

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk