Controller Freeze Protection
There are two ways to protect against solar panel pipes freezing.
The first way is to use the controller function. However this can only
be used in some circumstances when using heat pipe solar collectors. The
Sorel TDC3 controller has two anti-frost settings, below which the first
turns the pump on for 1 minute every hour. (e.g. at 3C), if the manifold
temperature reaches a second setting (e.g. 1C) then the controller runs
the pump continuously until the temperature recovers. This is adequate most
of the time, however in rural areas where freezing conditions may coincide
with a power outage, this system can leave a solar panel exposed to freezing.
It may be deemed a small risk and the consequences are not catastrophic if pipe work to
the panel were to fail. Most likely the leak would be outside the building and
because the system is closed only a couple of litres would leak.
The other alternative is to fill the system with an Anti-freeze mix, in any case this
is necessary if a flat plate collector or primary fluid vacuum tube panel is used. The
Anti-Frost function on the controller can also be used to give a "belt and braces" solution,
if the anti-freeze mix gave protection to -10°C, the controller could be set to circulate
the mix at -3 °C which is still very rare in Ireland, but offers a much higher protection,
particularily if the anti-freze mix has degraded (with time & overheat) and can no longer offer the