AVG Frost Protection Valve 15mm 1/2" BSP FPV15 has been developed to meet the requirements of thermosiphon solar collector panels installed in a frost prone environment. Important note: The AVG Frost Protection Valve is not recommended for freeze zones. A closed circuit collector panel with an approved anti-freeze fluid transfer should be used for these locations. It is important to refer to the solar water heater manufacturer’s installation instructions The FPV is designed to protect a solar collector panel from frost damage when the outside air temperature drops. The air temperature is monitored by a sensitive wax filled element which reacts by opening the FPV valve seat when the temperature drops. This allows warm water from the solar storage cylinder to flow through the solar collector panel and out of the FPV. The warm water flowing through the solar collector makes it harder for the panel to spot freeze which could damage the solar collector. The warm water flowing through the FPV will eventually close the valve seat and the water will stop flowing. The FPV will automatically repeat this cycle until the outside air temperatures rise.