RTP Solar recommends a "Drainback System" for Solar hot water.  This is an ideal system for North Carolina, where we must protect against freezing temperatures in winter.  The system has two loops - one is a closed loop with fluid (distilled water) flowing in a circle from the roof, then down to a heat exchanger, then back up to the roof.  In the middle of this loop is the drainback tank: the water falls into this tank at night, or when there is no heat to be gained from the panels.  The other loop circulates water from the hot water tank into the heat exchanger, where it extracts the heat back into the tank.  RTP Solar installs the SolarHot Solar Hot Water System.  The diagrams below are adapted from SolarHot - and we invite you to review their products at www.Solarhotusa.com 
RTP Solar has worked with SolarHotusa to provide the following YouTube videos:
http://www.youtube.com/watch?v=-i-sr3gTaEw          http://www.youtube.com/watch?v=puauTXEExPs       http://www.youtube.com/watch?v=UXyZulDQLD8  

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