So you have a recirculating radiated heater, and its warmed by decomposing compost,presumably external to the coils, am I visualizing that correctly?
** Yep. the pvc coils are winded in spiral and connected to radiator. Between radiator and compost, you have one pump that pumps the water every 2h. Basically, it pumps cca 30 seconds each 2h.
I have dismantled whole compost and there are two problems.
1.) Stuff in compost should be chopped in very small parts ( including leaves )
2.) Compost should be covered when the temperature is under 10 degrees Celsius.
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I rearrange the compost from the beginning and i cover it with blanks and nylon.
After two days, the result was as expected. Warm water again :-)
So i guess that this are two main thing, one should watch for.
There is one other thing that i dont get it...
On some forums, some guys are talking about different type of bacteria. The one that can boost up compost performance up to 70 degrees Celsius. The main thing is to create some internal compost environment that is capable of producing enough nitrogen and oxygen....
http://www.agrowingculture.org/2011/08/humanure-part-iii-thermophillic-bacteria-composting-stages-the-sanitization-of-compost-joe-jenkins/MV