PURPOSE: To prevent freezing, detect the abnormality of a pump and permit the back-up of the pump automatically without necessitating the operation of a valve by a method wherein a main machine circuit, having a valve and a check valve for a pump, is connected in series to a preliminary machine circuit, having the valve and the check valve for another pump, while check valves are provided in parallel respectively.
CONSTITUTION: A main pump circuit 3 and a preliminary pump circuit 4 are connected in series and valves 8 are provided at both ends of respective pump circuits while check valves 7, 6 are connected in series as bypass circuits. Abnormality detectors, such as a pressure switch 9 and a flow meter 10 which detect abnormal condition, are provided on the side of supplying to start a preliminary machine upon abnormality. According to this constitution, water flows through all lines even when either one of the pump circuits 3, 4 is operated. On the other hand, a faulty machine can be removed by the operation of the valves 8 even when either one of the main pump or the preliminary pump is being operated. Water flows through all lines even when the abnormality is detected and either one of the main pump or the preliminary pump is being operated whereby automatic back-up can be effected.
TSURUSHIMA YASUHIRO
HAYASHIDA TETSUNORI
TOYAMA ISAMU
