A water heater includes a first heater, a second heater, and a controller. The controller can enable different operational modes of the water heater, wherein only the first heater operates, only the second heater operates, or both the first and the second heaters operate. The controller can also be configured to enable a hybrid operational mode and a bypass operational mode. Further, in the different operational modes, the controller can direct water flow to at least one of a first conduit coupled to the first heater, a second conduit coupled to the second heater, and a bypass conduit. The controller can be configured to receive input signals relating to environmental conditions around the water heater and/or an aquatic system in which the water heater is installed.

The present disclosure provides a method and a system for controlling a heat pump water heater. The method includes: receiving a turn-on instruction; detecting the current temperature of the water in the water tank and the ambient temperature; acquiring a turn-on temperature difference according to the set temperature of the heat pump water heater and the ambient temperature, and acquiring a turn-on threshold according to the turn-on temperature difference; determining whether the current temperature is less than the turn-on threshold; if no, maintaining the current state; and if yes, controlling to enable the heat pump system to heat the water in the water tank.

A method of heating water in a water storage tank. The method includes: selecting an outlet port and an inlet port from at least three ports located in the tank at different heights along a vertical direction. The outlet port is below the inlet port. The method further includes extracting water from the outlet port, supplying the extracted water to an external heat exchanger configured for heating the extracted water, and delivering heated water from the heat exchanger to the selected inlet port.

An air-conditioning and hot water supplying composite system includes a heat source unit and a heat source-side heat exchanger, an indoor heat source unit, a hot water supply unit connected to the heat source unit and including a hot water supply-side heat exchanger and a hot water supply-side expansion device, and a controller that controls the heat source unit. The controller includes a mode switching unit that switches a control mode of the air-conditioning and hot water supplying composite system between a hot water supply control mode, a hot water supply preheating mode, and a condensing temperature control unit. The condensing temperature control unit determines the target condensing temperature according to a temperature of a heat medium subjected to heat exchange by the hot water supply unit, in the hot water supply control mode.

Embodiments of the invention provide a pool heater including a housing, a first tankless heater, a second tankless heater, and a controller. The controller is configured to activate only the first tankless heater when a first condition is met, activate only the second tankless heater when a second condition is met, and activate the first and the second tankless heaters simultaneously when a third condition is met.

A water heating system for a domestic hot water tank, the system including: a heat pump adapted to provide heat energy; and a heat exchanger comprising a coil of thermally conductive material arranged such that a diameter of the coil is approximately between five and six times greater than a diameter of the thermally conductive material and the heat exchanger is adapted to be installed in the domestic hot water tank and operationally coupled to the heat pump.

The present disclosure relates to a method and a system for preventing freezing when a four-way valve in a heat pump water heater is failed, which includes following acts: In act S1, it is judged that whether current water temperature T is lower than a preset minimum temperature T.sub.min , for the water tank, if yes, perform act S2; if no, perform act S1 again. In act S2, it is judged that whether a cooling rate Td of the current water temperature T is greater than or equal to a preset rate ΔT; or, it is judged that whether the current water temperature T satisfies T<T.sub.min−a and whether T<T.sub.min−a stands for a first time period t1, in which a is a limit value of a temperature difference; if at least one yes, perform act S3, otherwise, return to act S1. In act S3, a heat pump system is controlled to stop and an electric auxiliary heating system is started. By judging whether a cooling rate Td of the current water temperature T is greater than or equal to a preset rate ΔT; or by judging whether the current water temperature T satisfies T<T.sub.min−a and whether T<T.sub.min−a stands for a first time period t1, it may be judged precisely that whether the four-way valve is failed, which avoids a misjudgment.

This invention provides an electronic control for combination (fuel-fired boiler and electric heat pump) building space and water heating systems that optimizes operation of such within the operating temperature limits and heat capability of both the heat pump and boiler unit in the combination system. In a diagnostic mode, the controller assesses the ability of existing heat radiation systems in thermostatically controlled zones to meet heating loads at different operating temperature limits of the heat pump and boiler. The system/controller provides information to guide most effective deployment of system heat-dissipation devices. In its normal operating mode, the controller is capable of receiving input signals from zone thermostats, the boiler and heat pump, along with current outdoor temperature and other data, processing and evaluating inputs over time, and outputting control signals. The controller facilitates use of a combined heat pump and boiler heating system with minimum equipment, installation, and operational cost.

An apparatus and system for a combination space and water heater including a controller device and a method for control. The controller device is a self-contained system that can be added to, or in combination with, existing water heaters and hydronic air heating systems using standard plumbing connections, and provides a potable water system without any need of an intermediary heat exchanger. The controller device automatically monitors a heating capacity of the water heater and the hydronic heating coil over time, and correlates measured heating loads with one or more environmental temperatures, thermostats, user settings, and/or a supplemental heating system.

A water heater includes a first heater, a second heater, and a controller. The controller can enable different operational modes of the water heater, wherein only the first heater operates, only the second heater operates, or both the first and the second heaters operate. The controller can also be configured to enable a hybrid operational mode and a bypass operational mode. Further, in the different operational modes, the controller can direct water flow to at least one of a first conduit coupled to the first heater, a second conduit coupled to the second heater, and a bypass conduit. The controller can be configured to receive input signals relating to environmental conditions around the water heater and/or an aquatic system in which the water heater is installed.