A system for heating water to improve safety and efficiency. The system may have normal operation measured in time. After a time of normal operation, a water temperature setpoint may be checked. If the setpoint is not at a certain level, normal operation may continue. If the setpoint is within the certain level, water temperature may be measured. If the water temperature is less than a desired level, one or more draws of water may be measured for a preset temperature drop. If the draws do not meet the temperature drop, a return to check the setpoint may be made. If the draws meet the temperature drop, the setpoint may be reduced and a time of normal operation may be measured to determine whether a burn cycle occurs within the time. If not, normal operation may continue; but if so, a return to check the setpoint may be made.

A building heating system, including for heating water, such as tap water and/or utility water, of a building water system. The embodiments also relate to a kit of part to realize such a building heating system. The embodiments further relate to a method for controlling the building heating system.

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.

Disclosed is a storage water heating system with a heating apparatus external to the storage tank. The external apparatus receives a liquid coming from a lower portion of the tank, heats it, and delivers it to a top portion of the tank, where the hot water outlet is located. In this way, the natural thermocline of temperatures in the storage is maintained, the water delivered is at a greater temperature, efficiency is increased by reducing heat standing losses, and there is greater control over the quantity of energy stored. The external apparatus may be activated in response to a heating demand for the storage or for outlet water, or even in response to a power surplus from photovoltaic equipment and in the absence of withdrawal. A control system may modulate the power of the instantaneous water heater to track the surplus power of the photovoltaic system.

A water heater system including a boiler having a heat exchanger and an indirect water heater having a heat exchanger, and a controller configured to activate a pump such that the water flows between the boiler heat exchanger and the indirect water heater heat exchanger, and to control a heat source to provide heat to the boiler at a firing rate. The water heater system measuring temperatures of the water at the boiler water inlet and at the boiler water outlet, calculating an amount of heat transfer from the boiler heat exchanger to the indirect water heater exchanger based on the measured temperatures, and adjusting the firing rate based on the calculated amount of heat transfer to determine a heat transfer capacity of the indirect water heater exchanger.