| 摘要 |
PROBLEM TO BE SOLVED: To supply the circulated hot water of low temperature without impairing the durability of a heat exchanger in a hot water heating system. SOLUTION: A low temperature circuit-side control is executed when the supply of 45°C hot water from a low-temperature terminal unit is requested (step S101). Whether a detected temperature TH of a high-temperature thermistor is over a dew condensation avoidance temperature 50°C or not under this operating condition, is determined (step S103), the control is switched to high-temperature circuit-side control when TH is 50°C or less, and a target temperature of TH is set to be 55°C (step S104). Then whether a detected temperature TL of the low-temperature thermistor is less than 45°C or not is determined (step S105), then whether TL is over 52°C or not is determined when TL is more than 45°C (step S106), and the burning capacity is controlled to achieve TL of 55°C (step S107). The low-temperature circuit-side control is executed again when TH is over 65°C under this operating condition. COPYRIGHT: (C)2006,JPO&NCIPI
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