| 摘要 |
PURPOSE:To prevent noises due to the inclusion of air from being made and to prevent a hot water pump from being burned, by judging the state of idle operation of a hot water feeding pump based on the relative relation between the states of operations of a flow switch and a pressure switch thereby stopping forcibly the operation of the hot water feeding pump. CONSTITUTION:When supply of hot water to a hot water storing tank 1 is stopped, air is included into a hot water feeding path 10, and hot water would not flow therein at all. In this case, while the flow switch 12 is in the off operation with the decrease in the amount of hot water feed, the pressure switch 14 keeps the on operation since the pressure in the hot water feeding path 10 remains lowered, so that the hot water feeding pump 8 is in the state of idle operation. However if the closed state of a normally open contact MR1-2 of a reactive relay MR1 resulting from the on operation of the pressure switch 14 and the closed state of a normally closed contact MR2-2 of a reactive relay MR2 resulting from the on operation of the flow switch 12 continue for a prescribed period (T), a normally open contact TM1 of a timer TM is closed and a protection signal is outputted. As a result, the relay MR3 performs the on operation to open its normally closed contacts MR3-1 and MR3-2 so that the operation of the hot water feeding pump 8 and the on operation of the relay MR4 for a compressor are stopped forcibly. |
