A device (10) for controlling a system (30) for heating and cooling including at least one valve actuator (12) for a valve (14) of a bypass line (16) of the system (30), and a flow measuring device (20) for a return line (18) of the system (30), the return line (18) leading a combined flow from the bypass line (16) and a heating or cooling device return line (32) from at least one heating or cooling device (22) to at least one thermal energy source (24), the flow measuring device (20) being configured to determine and provide at least one actual flow value of the combined flow, wherein the valve actuator (12) is configured to receive the actual flow value and to control the valve (14) based on the actual flow value. The disclosure provides a device (30) to control a system for heating or cooling that is easier to handle and has reduced costs.

A water heating system having a system inlet pipe (1.002), a hot water delivery pipe (1.003) and a hot water return pipe (1.006) connected to a building hot water distribution network (1.024); the water heating system including one or more water heaters (1.001), the or each water heater having a heater inlet (1.022) and a heater outlet (1.023), a hot water return pipe (1.006) connected between the system inlet and delivery outlet via the building hot water distribution network to form a close loop hot water supply-return circuit; a pump (1.005) connected to circulate water through the hot water supply-return circuit whereby the pump can circulate water through one or more of the water heaters; a valve means (1.007) [a first non-return valve] adapted to prevent inlet water (water delivered to the system inlet) from flowing into the hot water return pipe or the building hot water distribution network.

Bypass valves for pool heaters are disclosed. Embodiments may include pool heaters with a heat exchanger, a support, and an automatic bypass valve coupled to the support. The automatic bypass valve may include a cylindrical bypass shaft, and a bypass valve having a non-circular opening configured to receive the bypass shaft, where the bypass valve is configured to slide along the cylindrical bypass shaft responsive to water pressure in the heat exchanger, and where water and debris can flow through the non-circular opening when the bypass valve is in a closed position.

A bypass system is provided for use with a pool water heater having a pool water heater input port configured to receive a portion of pool water, a heating system configured to heat water received by the pool water heater input port, and a pool water heater output port configured to output heated water from the heating system. The bypass system includes a pool water receiving port configured to receive pool water, a bypass line configured to divert a portion of the water from the pool, an output port configured to output the portion of pool water from the pool, a pool water heater receiving port configured to receive the heated water from the heating system, and a pool output port configured to output, to the pool, a combination of the heated water from the heating system and the portion of the water from the pool.