Open loop drain-back pool heating system
Closed loop antifreeze pool heating system

pool loop and collector loop. When the pool does not require heat, the pump circulates water from the pool, through the filter, check valve, 3-way diverter valve, standard pool heater, and back to the pool. If heat is needed and the solar system cannot supply it, the standard pool heater then turns on. The pump is usually controlled with a timer but in this case, is also controlled by the solar controller. If the pool needs heat and the solar system can supply the heat, the controller sends a signal the the 3-way diverter valve to redirect the flow of pool water through the solar collector panels. The water returns back through the standard pool heater and on to the pool. Usually the standard pool heater will be held off when solar heat is being supplied to the pool. The check valve between the filter and 3-way diverter valve prevents the pump from losing its prime when the system is turned off. The check valve between the pool heater and solar panels prevents water from backing up into the panels when the 3-way diverter valve is in the non-solar position, i.e., by-pass position. The small pipe (about 3/8" - 1/2" diameter)

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Closed loop antifreeze pool heating system - The closed-loop-antifreeze pool heating system consists of two loops; the heat collection loop and the heat delivery loop. Let's first

look at the heat collection fluid loop. Starting at the pump just to the left of the expansion tank, fluid will be pumped up to the collector panels. Here, the panels will absorb energy from sun and transfer this energy, in the form of heat, to the collection fluid. The fluid will then return down to the the heat exchanger. Here, heat will be transferred from the collection fluid side of the heat exchanger to the cooler pool side water. The collection fluid will then complete it's loop by flowing from the heat exchanger, through the check valve, and back to the pump. The job of the expansion tank is to allow for the expansion and contraction of the heat collection fluid as it heats up and cools down. The pool pump, just above the left end of the pool will normally be controlled by a timer but will also be controlled by a solar controller. The solar controller will make sure whenever the heat collection pump is running that the pool pump is also turned on. When solar heat is being collected, the pool pump pumps pool water through the filter and on to the heat exchanger

where the pool water absorbs heat from the warmer heat collection fluid flowing through the heat collection side of the heat exchanger. The water then returns through the pool heater, which is held off and to the pool. The controller continually monitors the sensors located at the solar collector panel and the feed line near the pool filter. When the temperature at the collector sensor exceeds the temperature of the pool water feed line by a pre-determined amount, usually 8 - 15º F, the controller turns the pumps on. The pumps stay on until the temperature difference between the panel and pool feed line sensors drops to about 3 - 5º F.

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