A heat-pump circuit may include an indoor heat exchanger, an outdoor heat exchanger, a compressor adapted to circulate a working fluid between the indoor and outdoor heat exchangers, and an expansion device disposed between the indoor and outdoor heat exchangers. A monitor for the heat-pump system may include a return-air temperature sensor, a supply-air temperature sensor, and a processor. The return-air temperature sensor may be adapted to measure a first air temperature of air upstream of the indoor heat exchanger. The supply-air temperature sensor may be adapted to measure a second air temperature of air downstream of the indoor heat exchanger. The processor may be in communication with the return-air temperature sensor and the supply-air temperature sensor. The processor may be programmed to determine a working-fluid-charge condition of the heat-pump system based on the first and second air temperatures.

When a heating operation mode using a heating unit is specified and when a hot water supply request using the hot water in a hot water storage tank does not occur, an air conditioning apparatus transmits a first selection signal for selecting the heating unit to a three-way valve. When the heating operation mode is specified and when the hot water supply request occurs, the air conditioning apparatus transmits, to the three-way valve, a second selection signal for changing a destination of circulation of secondary refrigerant from the heating unit to a coil heat exchanger, and transmits an operation start signal to a refrigerant indoor unit.

A heat pump may include a compressor configured to compress a refrigerant, a first temperature sensor provided in heating pipes connected to a heating device that heats an indoor space to sense a temperature of fluid flowing through the heating pipes, and a controller. The controller may be configured to determine whether a boiler is operating to heat an indoor space or is operating to supply hot water based on a sensing value of the first temperature sensor. The compressor may operate when the controller determines that the boiler is not operating to heat the indoor space and/or determines that the boiler is operating to supply hot water.

A hydronic system and method of use that will maintain normal system operating pressure while also reliably detecting even very small fluid losses in any closed loop fluid heat transfer system is described. The system includes a controller having clock or timing functionality in communication with one or more pressure sensors and a fluid supply valve that provides one or more notifications when the pressure drops below predetermined levels during predetermined periods of time. Depending on the nature of the pressure loss, the system has the capability of opening a fluid supply valve to provide make up fluid and increase system pressure.

A heat pump may include a compressor configured to compress a refrigerant, a first temperature sensor provided in heating pipes connected to a heating device that heats an indoor space to sense a temperature of fluid flowing through the heating pipes, and a controller. The controller may be configured to determine whether a boiler is operating to heat an indoor space or is operating to supply hot water based on a sensing value of the first temperature sensor. The compressor may operate when the controller determines that the boiler is not operating to heat the indoor space and/or determines that the boiler is operating to supply hot water.

A hot water supply system that can reduce energy consumption is provided. The hot water supply system includes a liquid heater for heating a liquid, a liquid-water heat exchanger, a water-heating circuit in which the liquid is circulated between the liquid heater and the liquid-water heat exchanger, a lower outward path for leading water from a lower part of a hot water storage tank to the liquid-water heat exchanger, the upper return path for leading the water from the liquid-water heat exchanger to an upper part of the hot water storage tank, a middle outward path for leading the water from a middle part of the hot water storage tank to the liquid-water heat exchanger, a middle return path for leading the water from the liquid-water heat exchanger to a middle part of the hot water storage tank.

A hydronic system and method of use that will maintain normal system operating pressure while also reliably detecting even very small fluid losses in any closed loop fluid heat transfer system is described. The system includes a controller having clock or timing functionality in communication with one or more pressure sensors and a fluid supply valve that provides one or more notifications when the pressure drops below predetermined levels during predetermined periods of time. Depending on the nature of the pressure loss, the system has the capability of opening a fluid supply valve to provide make up fluid and increase system pressure.

A hydronic system and method of use that will maintain normal system operating pressure while also reliably detecting even very small fluid losses in any closed loop fluid heat transfer system is described. The system includes a controller having clock or timing functionality in communication with one or more pressure sensors and a fluid supply valve that provides one or more notifications when the pressure drops below predetermined levels during predetermined periods of time. Depending on the nature of the pressure loss, the system has the capability of opening a fluid supply valve to provide make up fluid and increase system pressure.

Heat pump system (100) comprising a heat medium circuit (210,220,230,240,250,310,320,410,420,430,440,450,460) in turn comprising at least three heat exchanging means (314,315,315,422,433,452) between the heat medium and a respective heat source or sink selected from outdoor air, a water body, the ground, indoor air, pool water or tap water, a valve means (311,312,313,421,431,451) arranged to selectively direct the heat medium to at least two of said heat exchanging means, and a control means (500). The invention is characterized in that the heat pump system comprises temperature sensors (314a,314b;315a,315b;316a,316b;423,424,425;432,434,435) both upstream and downstream of at least one of said heat exchanging means, in that the system determines, based upon temperature measurement values comprising at least one value read from said sensors, to what heat exchanging means the heat medium is to be directed, and in that when heat medium is not directed to a certain heat exchanging means a measured temperature value is read upstream and downstream of the certain heat exchanging means, and in that an alert is set off in case the values differ by more than a predetermined value. The invention also relates to a method.

A heating system (100), a controller (110) for a heating system and a method of controlling a heating system (100) suitable for responding to grid stress events are disclosed. A heating system (100) comprises a tank (104) for holding water; a heat pump (102) arranged to provide heat to the tank (104); an electric heating element (108) disposed in the tank for heating water; and, a controller (110) configured to: control electric power from an electric power grid to the heat pump (102) and the electric heating element (108); detect a grid stress event; determine a heat pump energy penalty for providing heat in response to the grid stress event under a present operating condition; and, vary, in dependence on the determined heat pump energy penalty, a power provided to the electric heating element (108).