| 摘要 |
PURPOSE:To surely stop a pump before reaching shutoff pressure even if pumping power lowers by stopping the pump by means of a flow switch when the pressure enough to open a pressure switch has not been generated. CONSTITUTION:When long-term use of a pump 1 has caused pump characteristics to deteriorate, even if pump discharge volume becomes larger than the quantity of consumed water on the side of a faucet on the condition that the pump 1 is being operated through a series circuit formed of a pressure switch 10 an the first contact 11a of a flow switch in a control circuit 22, pressure in a pressure tank can never exceed its upper limit. When the pump 1 is operated under the above condition, it approaches to shut off operation, and thereby a flow passing through a discharge pipe is reduced. When the said flow reaches its specified value of less, the first contact 11a of the flow switch is opened to stop the pump 1. Therefore the pump 1 can be surely stopped near its shut off operation to prevent a failure due to water temperature rise in the pump 1.
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