|
 |
Freeze Protection for Solar Water Heating
The greatest danger to a solar water heating system
is freezing. Even when the air temperature at night is well above
32°F, idle fluid in the collector can freeze because it radiates
heat up to a cold, dark sky. You can prevent this by using antifreeze
instead of water as the heat transfer fluid. It circulates in
a closed loop and transfers heat to the storage tank in a heat-exchanging
coil. It is important to use propylene glycol rather than ethylene
glycol and test it every two years; ethylene glycol can be poisonous
if the exchanger leaks.
It is less likely that the water in a batch water
heater would freeze, especially if it has a lid that can be closed
on cold nights. However, the water in the pipes that connect the
batch heater to the inside can freeze. Freeze damage can be prevented
by using either polybutylene pipe, which should not burst when
water in it freezes, by wrapping heat tape around metal pipes
or by simply draining the system in cold weather.
