HOT WATER HEATING DEVICE

PURPOSE:To prevent momentary idle burning by making the circulating pump to be possible to run when the water level in expansion tank becomes higher than lower water level and beginning the combustion of water heater when the water level reaches at middle. CONSTITUTION:A water level detecting device 6 is set in an expansion tank 4 and the detecting device 6 is constituted from detecting electrodes of high, middle and low water levels H,M,L respectively. When the water level of expansion tank 4 does not reach L, an automatic water supply valve 7 is opened to supply water automatically and the running of circulating pump 5 and the combustion of water heater 1 are stopped. When LON is reached, the circulating pump 5 is made to be possible to run. When MON is reached the combustion of water heater 1 is made to be possible. The automatic water supply valve 7 is closed when high water level H is reached. By making the circulating pump to be possible to run when the water level in the expansion tank reaches LON, and beginning the combustion of water heater when the water level MON is reached, the momentary idle burning caused by vibration when the water level in the expansion tank has reached at LON or lower than L can be prevented.