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solar/geothermal help

Al Letellier_21
Al Letellier_21 Member Posts: 402
Helping my nephew with his hybrid heating system....all radiant with Weil boiler (of course)and a 60 gallon indirect and Wirsbo extruded plates, a wood boiler and a 600 gallon insulated stainless steel tank for storage. We will be tying in a solar set up and need a dump zone. He has a lot of fill to put in at the front of his house, almost six feet, and we are thinking of a buried 500 foot loop in the ground. No other place to put any excess heat.

I have little if any experience in this area and am looking for suggestions/ideas as to what to use for tubing/size to get the best heat transfer. Considering both fully charged system with A/F or a drain down. We have the grade to pitch but I am concerned about complete drainage but at 6 feet down under grass with no traffic it shouldn't be an issue, but we live in Maine !!! My nephew is so bright it scares me at times but he sure is fun to work with....even at my age I learn something every time we work together.

Any thoughts, ideas or solid tech info would be greatly appreciated from all you knowledgeable pros out there....is this a great site or what???


  • hot_rod
    hot_rod Member Posts: 22,110
    what type of collectors

    and how many (square footage) With 600 gallons of storage you may not need much, if any dump.

    Also consider a drainback, they never need dump capacity. With large square footage arrays and little if any summer loads the DB's look much better.

    Go to www.caleffi.us and download I-dronics #6, plenty of good ideas, like this schematic, for pressurized glycol and drainback arrangements.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Al Letellier_21
    Al Letellier_21 Member Posts: 402
    solar dump

    Thanks for the tip, Hot Rod. Should have thought of that as I have that copy here.

    So much info available and so little time.........I appreciate the push in the right direction. Haven't sized the collectors yet, still in the planning stages.
  • meplumber
    meplumber Member Posts: 678
    Did this.....

    I did a house up here on MDI where we did a 6' deep X 4' X 4' pit full of 3/4" hePex and packed tight with sand.  The pit acts as a bit of a geo storage tank if you will. 

    A bit of controls magic brings the circ to the pit on when the storage tank temp hits a pre set mark.  This house is a similar setup, minus the wood.  It uses a mod con for primary and solar as the boost.

    We also did a few with wood/ mod con/ solar/ insulated storage where we used tubing laid in under a walkway for a dump.  Doesn't work too well when the surface temp of the walkway climbs.  Hey live and learn.

    I recommend an A/F mix of about 30% in the pit.  Can't be too careful with an average frost depth of 5' can you.

    Good Luck
  • LarryC
    LarryC Member Posts: 331
    Heat dump = firewood dryer

    If you do not use a drain back solar system, why not plumb in horizontal cast iron radiators and stack firewood on them?  Don't dump the excess heat, use it.

    Obviously winter freeze protection will be an issue, but the summer is too short already.  Extending the wood drying season will allow for dryer wood and higher buring efficiency.
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