A Viessmann safety valve with attachable pressure release mechanism and O-ring, suitable for use in Vitodens 100-W WB1A Combi, Vitodens 100-W WB1A Combi Plus, Vitodens 100-W WB1A System, Vitodens 100-W WB1A Combi, Vitodens 222-F FS2A, Vitodens 242-F FB2A and Vitodens 111-W B1LA units. The pressure relief valve helps to control pressure in a closed system by proportionally opening to relieve excess pressure, preventing catastrophic malfunction.

