Thought the setup took a bit of doing, surprisingly little when you consider the results–we’re now looking at 3 to 6 months of almost free heat for a 200 square foot room in the barn.
The pile took 2 hours to build (shifted by hand out of the back of a trailer), and the materials for the heat transfer coils (300 feet of 3/4″ pex pipe, fittings, clamps and pump and fans) cost under $400.00. The plumbing work took about 2 hours as well. See the previous post about Jean Pain for more info and links to resources.
The system can keep the room at 70F when it’s 17F outside, with heat from a 6 ton compost pile.
Here’s the layout of the valves and inlets to the loop which make it easy to get all the air out. Just hook up a relatively powerful circulation pump and use a 5 gallon bucket for the water to circulate through, eliminating all air bubbles, when filling. I like to put the circulation pump so that any air that might get trapped in it can escape when the pump is off. The highest point in this system is an expansion tank above the ‘T’ fitting seen in the upper left hand corner of the image below.
And a few more images: