I have about 780 feet of 1/2 inch pex in four parallel coils. It wont come close to handling 150 kBTU's. It won't handle my new boiler (about 112 kbtu ) I "borrowed" 100 feetemesine said:Copper is really pretty expensive. 1/2 inch copper is $1.50+ per foot on a quick google search. I could do a very large heat exchanger in pex. I'd rather work in pex, it is a lot easier to work with. I want to be able to transfer about 100K to 150K BTU at a 20 degree temperature differential with water flowing at 20 gpm.
One solution would be to run 4 parallel 3/4 inch, 250 foot pex lines in the heat storage tank. Space in the tank is not a problem. That is around 200 square feet of pipe surface area. I may just build it and add on a few more lines if necessary. Pex is so easy to work with it might be easier than building a more complicated copper heat exchanger.
Does anyone know how to calculate the heat transfer if such an array? I know it is not easy!