22-Jun-2014 04:58 PM
Systems 1, 2, and 3 have a passive Thermal Freeze Valve protection option. These systems are called “Open loop” because they have street water pressure in them at all times while in operation. In case of a hard freeze, a simple freeze protection drain setup is included with these systems whereby the pump is turned off, two ball valves are closed and two hose bibs are opened (allowing about one to two gallons of water to drain out, using a pail or hose to drain), this process takes about two minutes. The “Thermal Freeze Valve” starts to open at about 40 degrees to let a small flow of water out onto the roof. This flow is usually enough to prevent freeze-up of the collector absorber during occasional freeze conditions to as low as 30F.
Better freeze protection down to 20F is provided with System 2 which has a “Differential Control Recirculation Freeze Protection” or PV powered System 3 with Snap Switch and Transformer Recirculation Freeze Protection. The snap switch will sense freezing conditions from its roof sensor and will turn on the pump causing a constant flow of water through the collector. The “Thermal Freeze Valve” is important to use in conjunction with the Differential Control in case of power outages. This type of freeze protection is used extensively in Florida, Arizona, California (as far north as Sacramento) and similar climates but draining must still be done in a hard freeze temperatures below 20F.
In the unlikely event that the absorber is freeze damaged, it is easier to repair due to its easily removed copper absorber which can be repaired or the damaged section replaced at low cost.
For COMPLETE freeze protection, use the system 4 and 5 closed loop heat ex-changer tank.