To suppress start/stop of an electric pump, and reduce noise by arranging a bypass pipe for connecting a delivery side and a suction side of the electric pump to each other, and switching control of the electric pump from an estimated terminal pressure constantly controlling unit into a pumping head control part in the case where a signal having a minimum flow rate and less is detected continuously for a prescribed time by a flow rate detecting means.
A feed water piping 1 comprises a feed water main pipe 2 and feed water branch pipes 3A, 3B, and electric pump 12 (12A, 12B) is arranged on each feed water branch pipe 3A, 3B. Bypass pipes 15A, 15B are arranged to connect a delivery side and a suction side of the electric pump 12 to each other, and electric valves 16A, 16B are interposed between them. Pressure detectors 18, 20 and a flow switch 19 are arranged on the feed water main pipe 2, and the electric pump 12 is controlled through inverters 22A, 22B on the basis of the output thereof. Namely, in the control unit 21, in the case where a minimum flow rate and less is detected, control of the electric pump 12 is switched from an estimated terminal pressure constantly controlling unit into a shut-off pumping head control unit for controlling the electric pump 12 serving the pumping head having a set pumping head or more as a first pumping head.
SATO MORIYUKI
OBAYASHI AKIRA
