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Recirc line from CI BB?

We have a situation in a remodel of an old three story Tudor. the kitchen zone has a kickspace heater and 5' of Cast Iron Basebaord for the library. The library is built over an old garage floor, and the crawl space is not heated. I'd like to run a gravity recirc line from the boiler to the supply and return sides of the radiator just below the floor under the CI BB. I reasoned that if it works for domestic hot water it should work for this application? The zone in question is on it's own thermostat in the library, and operates off of a zone valve. I thought that we could run Heat PEX around the basement back to the boiler from 3/4" x 1/2" tees in the supply and return lines and with a check valve where we connect to the boiler at the drain, we should get small amount of gravity flow any time the boiler has heat. Any other solution has inherent reliance on electricity (ie. three way zone valve/separate circulator and controller in the cold crawl space/electric heat tape) or hope that insulation alone will keep it from freezing and bursting....not my favorite choice. If this would work, the circulation would be minimal yet enough to prevent freeze up. The CI BB is fed with 3/4" x 1/2" monoflo tees on both the supply and return sides. Will this be a viable way to overcome the potential problem? If not, what other suggestions do you have? Thanks in advance for your input!


  • Weezbo
    Weezbo Member Posts: 6,232
    wrap the return rooms with slant fin convectors and Dont

    put the pipes where they will freeze. Of cource you have to determine the path And install a control for that baseboard(slant-fin) and not oversize the convectors in the Slant fin housings as not to overwhelm the occupants with heat from the convectors. that was alot to take in on one go around. you would have to make some mono flow ts and a danfoss valve with remote sensor and thermostat your "zone" control of the convectors over the top of the new return run from the kick space and CI baseboard.
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