| 摘要 |
PURPOSE:To enable to operate economically, by automatically reducing an output from a prime mover part for a forced-circulation pump when it is detected that a return passage part of a circulating water passage is filled up with water. CONSTITUTION:A cistern 7 for controlling the supply of water to a hermetically sealed type hot water storing tank 2 is provided at a place in proximity to the tank 2 with respect to height, and the forced-circulation pump 4 is intermediately provided in a feed passage part 3A of the circulating water passage 3 between the tank 2 and a solar heat collector 1 provided above the tank 2. In said water heater, the output of the prime mover part 15 for the pump 4 can be varied in a plurality of stages, and a device 14 for detecting that the return passage part 3B of the water passage 3 is filled up with water is provided. Further, based on the detection results of the device 14, a mechanism 16 automatically changes over the output of the prime mover part 15 from a 2-polar operation with a large lift to a 4-polar operation with a small lift, thereby performing operations wastelessly and economically. |
