PURPOSE: To eliminate the chattering of the captioned valve and to prevent the pulsation of cold-and-hot-water by giving a predetermined time-difference to the valve opening/closing time of a differential pressure control valve, when the time is set.
CONSTITUTION: The downstream side of a cold-and-hot-water-machine R of a discharge pipe 1 of the first and second variable speed pumps P1 and P2 is connected to a suction pipe 5 via a bypass pipe 6, and a differential pressure control valve 7 is installed in the midst of the bypass pipe 6. A control device 11 is provided with a timer TMc, which monitors the state of continuation of the closing condition of the bypass valve 7, and a timer TMo, which monitors the state of continuation of the opening condition of the bypass valve 7. The timers TMc and TMo are started when the running speed of the pumps P1 and P2 reaches the predetermined, valve-closing/opening speed of the bypass valve 7, and a closing/opening signal is issued to the bypass valve 7 after the valve-closing- or -opening condition has continued for the predetermined period.
HAMADA SATOSHI
IKEDA MASASADA
EBARA DENSAN KK