PURPOSE: To prevent damage due to freezing even at a time of power failure by providing an electromagnetic valve which is opened or closed by ON-OFF of a heater source at branch pipe inlet and exit and by draining a branch pipe and a hydraulic pressure measuring apparatus at OFF time of the heater source.
CONSTITUTION: In a time of usual operation, since an electromagnetic valve 5 is excited by the power source 10, the valve 5 is in an open state and an electromagnetic valve 6 is contrary in closed state. Thus, supplied water is filled into the branch pipe 3 and in a sensor 1, and the hydraulic pressure can be measured. Next, in case of OFF state of the source 10, the valve 5 turns to a closed state due to the magnetic erasure and the valve 6 is in the contrary in an open state. Accordingly, the supplied water sealed in the sensor 1 is flowed out to the outer part through a drain exit 13 and a drain pipe 19. Thus even if the source 10 of the heater 4 is lost, the prevention of freezing is made possible because the inner part of the sensor 1 is drained.
OZAWA TOSHIO
NOUCHI TAKAO
