On Thu, 09 Mar 2006 22:22:35 +0000 someone who may be AJH
wrote this:-

Yes this was my assumption, the water header being sufficient cross
section, and within the insulated area of the house, that once the
pump stopped it just filled up a bit. The only drawback I could see
was that the pump would always work against the head from the header
tank up to the panels. In a sealed system the pump only circulates
against the friction in the system.

http://www.imaginationsolar.com/PDFs...ainback_v1.pdf
shows the unit promoted by one supplier. In addition to this box
there is just the panel, cylinder and some piping/wiring.

The drainback system does depend on the valve working, just like
human life depends on valves in the heart working. I suspect that
the valve in the unit is chosen to have a very large number of
working cycles, as it will be operating a minimum of once a day and
so the possibility of it failing and the panel to freezing is remote
enough to be placed with the other remote possibilities, like the
panel being hit by a meteorite.




--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54