Hot-water supply and heating system

A hot-water supply and heating system comprising:

• a heat source unit configured to generate heat;
• a heat-medium heat exchanger through which the heat is supplied from the heat source unit to a load-side device;
• a primary circuit in which a first heat medium circulates between the heat source unit and the heat-medium heat exchanger;
• a first pump provided in the primary circuit and configured to circulate the first heat medium between the heat source unit and the heat-medium heat exchanger;
• a secondary circuit in which a second heat medium flows between the load-side device and the heat-medium heat exchanger;
• a second pump provided in the secondary circuit and configured to cause the second heat medium to flow between the load-side device and the heat-medium heat exchanger;
• a first temperature sensor configured to detect a primary fluid temperature that is a temperature of the first heat medium that flows out of the heat source unit via the primary circuit;
• a second temperature sensor configured to detect a secondary fluid inlet temperature that is a temperature of the second heat medium that flows from the heat-medium heat exchanger into the load-side device via the secondary circuit;
• a heat-source-unit controller configured to control a heating capacity that is the amount of the heat generated from the heat source unit;
• and
• a pump controller configured to control the second pump based on control information received from the heat-source-unit controller,
• wherein the heat-source-unit controller is configured to:
• determine whether the primary fluid temperature detected by the first temperature sensor is lower than a primary target temperature or not;
• determine whether a heating capability of the heat-source-unit device is equal to an upper limit value determined in advance or not, when determining that the primary fluid temperature is lower than the primary target temperature;
• and
• transmit upper-limit reached information as the control information to the pump controller when determining that the heating capability of the heat source unit is equal to the upper limit value, the upper-limit reached information being information indicating the heating capacity of the heat source unit reaches the upper limit value, and
• wherein the pump controller is configured to:
• reduce an operation frequency of the second pump when receiving the upper-limit reached information from the heat-source-unit controller;
• determine whether a heat load that occurs at the load-side device is low or not based on the secondary fluid inlet temperature, when receiving the upper-limit reached information from the heat-source-unit controller;
• and
• reduce an operation frequency of the second pump when determining that the heat load is low.