My first DIY Solar hot water Collector using a 300' Pex Coil
The project consisted of building a Solar Box/Oven for 300' of 3/4" Pex-B Tubing to sit inside of and was built using 2x12's with a finished size of 36"x36" . 1/2" plywood was used for the backing with 1" Polyiso Board sitting on top of that with a thick piece of sheetmetal plate on top of that --- everything inside the Box was painted a flat black including the aborber plate, inner / outer box walls , and Krylon Fusion Paint for the Pex Coil . The top of the Box recieved a double pane argon-filled Low E window in vinyl sash which has good light transmittance with ability to retain heat in the Box. Collector Box is on a 30 degree angle from vertical. Piped in parallel to the water heater so the house hot water supply is either fed by 100% Collector water or from the standby electric Water Heater (accomplished via bypass valves) .
Results after 5 hours of solar heating starting with 55 f. Well water :
90 f. totally sunny day (30 degree angle):
Temp. inside Box : 140 f.
Exiting water Temp : 136 f.
93 f. totally sunny day (laying horizontal on the ground)
Temp inside Box: 160 f.
Existing water Temp : 158 f.
84 f. totally cloudy day with mostly rain (30 degree angle) :
Temp. inside Box : 105 f.
Exiting water Temp : 100 f.
(The Pex Coil holds about 6 gallons, but since i live alone ... it is more than enough hot water for my limited water useage for 100 f. showers and occasional Dishwasher ; in fact on a sunny day I have to cool it down alot with cold water at the Shower Head so Im using less than the 6 gallons of Collector Water. . The Pex-B Tubing I used has a rating of 200 f. at 100 psi and the CPVC leading from the Collector Box to the house is rated at 180 f. at 100 psi. Total material cost : under $400 . This project is ideal for someone who has minimal daily hot water requirements ; more Pex Coils can be added for greater storage capacity if needed . The aim of this system was to keep it inexpensive , uncomplicated, without the use of a seperate water storage tank / controls / pump and to provide adequate hot water for One person) .