is supported by support members 44 at an elevation above the evaporator 12 whereby refrigerant within condenser 36 may flow by force of gravity through liquid line 38 to evaporator 12 refrigerant may flow in this direction even when the compressor motor 32 and pump motor 24 are de energized as by the opening of switch 46 connected in series with a power source 48 should the outdoor ambient temperature be below the freeze point of water refrigerant vapor in the evaporator will migrate through the centrifugal compressor 30 to the condenser where in turn it will condense and flow by gravity through liquid line 38 back to the evaporator to be vaporized again thereby causing a continuous cooling effect upon the water within the tubes 16 since the water in tubes 16 is not flowing because pump motor 24 is not energized the tubes will eventually become frozen this problem is obviated by the instant invention which employs an automatic liquid line shutoff valve assembly 50 the details of which are shown in fig2 now referring to fig2 it will be seen that valve assembly 50 includes an upper valve body 52 connected to a lower valve body 54 the lower valve body has a valve seat 56 disposed at the valve assembly inlet which is connected to the condenser lower valve body 54 also has an outlet opening 40 a valve or valve member 60 is arranged to cooperate with valve seat 56 valve 60 is connected by bolt 61 to valve stem 62 which is mounted for axial movement in bearings 63 a rollable diaphragm or flexible boot 64 having a partial cylindrical configuration.