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Supplemental Radiant Floor

jonnyz Member Posts: 7
Hello and thanks for reading,


My boiler is only a few yeards old, and it is a closed loop hot water system with cast iron radiators.  It has two 2-1/2" headers that feed most of the house.  At some point, a third 3/4" copper line was added to the primary in/out pipes from the boiler, essentially creating another header but to heat one sole radiator. 


My question is can i simply tee off that recently installed 3/4" supply and return line to heat ~280 LF of pex radiant flooring?  I read alot about zoning, and pumps, and manifolds, but i simply just want to run hot water under the floor to supplement the rooms heating and keep the floors comfortable.


Any advice would be very helpful


  • NRT_Rob
    NRT_Rob Member Posts: 1,013
    if you

    dont care about output, you can do a suspended tube for basic floor conditioning that way.

    but how you guarantee flow through the loop, which will have a much higher flow resistance than the radiators, will be an issue. Also, zoning. Can't just run it all the time, need some kind of control device.
    Rob Brown
    Designer for Rockport Mechanical
    in beautiful Rockport Maine.
  • jonnyz
    jonnyz Member Posts: 7

    thank you for the respnse, I am only concerned with conditioning because I will still have a primary heat source in the room

    yes i am concerned about resistance. there is only one other radiator on this line, and that radiator seems to work just fine the way it is setup.  Also, the  boiler only runs for 20-30 min every  one to two hours, and the water temp only gets to about 120 deg. before the house is up to temp.  I dont think it should be a problem if they run the same amount of the time as the other radiators

    its a 150,000 btu boiler in a 2500 sf house
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