Water heating system including multi-function heat source apparatus

A water heating system comprising:

• a first heat source apparatus, the first heat source apparatus being a hot-water-heating heat source apparatus and including a first hot water supply circuit;
• a second heat source apparatus including a second hot water supply circuit;
• a hot water delivery pipe to which the first and second hot water supply circuits are connected in parallel;
• and
• a cut-off mechanism configured to cut off a flow path to the hot water delivery pipe in the first hot water supply circuit,
• the first heat source apparatus having an operation state in which heating of low-temperature water in the first hot water supply circuit and supply of a heat medium to a space-heating terminal are simultaneously performed by using a common heat source,
• the first hot water supply circuit being configured to heat the low-temperature water through heat exchange with the heat medium, which is heated through heat exchange with the heat generated by burning fuel, and to output the heated water to the hot water delivery pipe,
• the second hot water supply circuit being configured to heat low-temperature water through heat exchange with the heat generated by burning fuel, and to output the heated water to the hot water delivery pipe,
• when hot water supply by the water heating system is started, hot water being output to the hot water delivery pipe from the second hot water supply circuit while the flow path in the first hot water supply circuit is cut off by the cut-off mechanism, and
• when a load imposed by hot water supply by the second hot water supply circuit becomes higher than a predetermined reference value, the cut-off mechanism opening the flow path in the first hot water supply circuit to allow output of hot water from both of the first and second hot water supply circuits to the hot water delivery pipe, wherein
• the first heat source apparatus includes
• a first heating mechanism configured to heat the heat medium,
• a space-heating circulation path configured to circulate the heat medium heated by the first heating mechanism to and from the space-heating terminal during a space-heating operation,
• a bypass circulation path branched from the space-heating circulation path and configured such that the heat medium is again merged with the space-heating circulation path without going through the space-heating terminal, and
• a distribution control mechanism configured to control a distribution ratio representing a ratio of a flow rate of the heat medium supplied to the bypass circulation path to a total flow rate of the heat medium heated by the first heating mechanism,
• the first hot water supply circuit is configured to heat at least some of the low-temperature water which flows through the first hot water supply circuit through heat exchange with the heat medium which flows through the bypass circulation path,
• the second hot water supply circuit includes a second heating mechanism configured to heat at least some of the low-temperature water which flows through the second hot water supply circuit,
• when the hot water supply is started, the second heating mechanism is activated with the flow path in the first hot water supply circuit being cut off by the cut-off mechanism,
• when the load imposed by hot water supply by the second hot water supply circuit becomes higher than the reference value, the distribution control mechanism is controlled such that some of the heat medium passes through the bypass circulation path in the first heat source apparatus and the cut-off mechanism opens the flow path in the first hot water supply circuit, and
• when a flow rate in the first hot water supply circuit is higher than a prescribed value while a control command to cut off the flow path is generated for the cut-off mechanism, the distribution control mechanism controls the distribution ratio such that the heat medium is not supplied to the bypass circulation path.

A water heating system comprising:

• a first heat source apparatus, the first heat source apparatus being a hot-water-heating heat source apparatus and including a first hot water supply circuit;
• a second heat source apparatus including a second hot water supply circuit;
• a hot water delivery pipe to which the first and second hot water supply circuits are connected in parallel;
• and
• a cut-off mechanism configured to cut off a flow path to the hot water delivery pipe in the first hot water supply circuit,
• the first heat source apparatus having an operation state in which heating of low-temperature water in the first hot water supply circuit and supply of a heat medium to a space-heating terminal are simultaneously performed by using a common heat source,
• the first hot water supply circuit being configured to heat the low-temperature water through heat exchange with the heat medium, which is heated through heat exchange with the heat generated by burning fuel, and to output the heated water to the hot water delivery pipe,
• the second hot water supply circuit being configured to heat low-temperature water through heat exchange with the heat generated by burning fuel, and to output the heated water to the hot water delivery pipe,
• when hot water supply by the water heating system is started, hot water being output to the hot water delivery pipe from the second hot water supply circuit while the flow path in the first hot water supply circuit is cut off by the cut-off mechanism, and
• when a load imposed by hot water supply by the second hot water supply circuit becomes higher than a predetermined reference value, the cut-off mechanism opening the flow path in the first hot water supply circuit to allow output of hot water from both of the first and second hot water supply circuits to the hot water delivery pipe, wherein
• the first heat source apparatus includes
• a first heating mechanism configured to heat the heat medium,
• a space-heating circulation path configured to circulate the heat medium heated by the first heating mechanism to and from the space-heating terminal during a space-heating operation,
• a bypass circulation path branched from the space-heating circulation path and configured such that the heat medium is again merged with the space-heating circulation path without going through the space-heating terminal, and
• a distribution control mechanism configured to control a distribution ratio representing a ratio of a flow rate of the heat medium supplied to the bypass circulation path to a total flow rate of the heat medium heated by the first heating mechanism,
• the first hot water supply circuit is configured to heat at least some of the low-temperature water which flows through the first hot water supply circuit through heat exchange with the heat medium which flows through the bypass circulation path,
• the second hot water supply circuit includes a second heating mechanism configured to heat at least some of the low-temperature water which flows through the second hot water supply circuit,
• when the hot water supply is started, the second heating mechanism is activated with the flow path in the first hot water supply circuit being cut off by the cut-off mechanism,
• when the load imposed by hot water supply by the second hot water supply circuit becomes higher than the reference value, the distribution control mechanism is controlled such that some of the heat medium passes through the bypass circulation path in the first heat source apparatus and the cut-off mechanism opens the flow path in the first hot water supply circuit, and
• the first hot water supply circuit includes a flow rate restriction unit configured to make an amount of flow in the first hot water supply circuit smaller than an amount of flow in the second hot water supply circuit when hot water is output from both of the first and second hot water supply circuits to the hot water delivery pipe.