| 摘要 |
PROBLEM TO BE SOLVED: To judge small water quantity without being influenced by the fluctuation in suction side pressure and water temperature. SOLUTION: In a system to control probable end pressure constant, at the same time when an operating frequency becomes a minimum maintaining frequency Nb and does not change for a fixed time, the water in a pipe is heated, and changes in water temperature is also monitored by a temperature detecting section. When the water temperature changes more than the specified value, the temperature detection section judges it as small water quantity and stops a pump. A water supply device carrying out this method is provided with a pump 1, discharge pipe 7, control device 2 and pressure detecting section 3. A ceramic heater 4 is adhered to the outer face of a pipe, and a thermistor comprising temperature detecting section 5 is arranged adjacent to the ceramic heater 4. A suction pipe 6 and discharge pipe 7 are connected to a water supply device.
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