On Sun, 02 Mar 2008 11:16:46 +0000 someone who may be The Natural
Philosopher wrote this:-

If I have hot water in my cylinder, and there's not much sun, I may lose
heat by pumping the hot water out onto the roof.

Why should you do that?

To stop it freezing?

Why?

The Solartwin heats the domestic hot water directly. If it freezes
then it freezes, the panel tolerates this without problems. When the
sun comes out next it will soon unfreeze the panel.

With systems which heat the domestic hot water indirectly the solar
circuit can be provided with a suitable amount of anti-freeze. There
are also drain-down systems. Even if people haven't done either of
these, the pump will generally run for not many minutes even on the
coldest nights.


--
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