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in floor heat with a cast iron boiler?

Jim_64 Member Posts: 253
I just picked up a really neat old house that was abandoned.  All the plumbing in the house was froze up and burst.  It's got a 135,000BTU Burnham boiler in the basement.  Since the pipes are burst and I'll need to do demo ceilings from some water damage, and it's got a full basement, I'll be able to get at everything.  With mixing valves, can I get the water temp down enough to do in-floor heat?  Or is this old, blue beast going to cook the water too hot for that? 


  • Gordy
    Gordy Member Posts: 9,546
    It's done all the time

    Just need a mixing valve.

    What are the existing emitters ?
  • Jim_64
    Jim_64 Member Posts: 253
    fin tube

    It's got baseboards that are mostly burst from being froze up.  Like I said, the plumbing and HVAC is a complete do-over in this house.  
  • Gordy
    Gordy Member Posts: 9,546
    Heat loss

    Do one to make sure radiant floors can do the job on their own with out supplemental.

    You will have to decide the type of radiant floor detail. Over the top sandwich, or under floor.

    It may be helpful to pin down type of base board, and how many feet in each room as your gutting the system.

    Sure the boiler is not damaged?
  • Jim_64
    Jim_64 Member Posts: 253
    not sure yet

    Once the ground thaws out, I can get the well working and a line run to the boiler so i can see if it holds tap water pressure.  If it's damaged I can pick up something else to use.  I got the house cheap enough. 

    I'm thinking under floor heat since i can get at everything and the former owners went through the bother of sanding and refinishing all the original tongue and groove flooring throughout the house.  Looks really sharp. 

    I'll do a heat loss calc. and make sure this blue beast isn't too big.  There really doesn't seem to be enough base board for 135,000 BTU.  At 590BTU per foot, that means it would need about 229 feet of baseboard?  I'll get over there with a tape measure and see for sure.  I would be surprised if there's any more than 120-150 feet in that whole house.  HVAC guys around here don't understand anything but forced air systems so it wouldn't surprise me the least if it's set up all wrong. 

    How do you calculate the heat emission of under-floor heat?  Do I run one 1/2" oxygen barrier pex line between each floor joyce and staple it against the sub floor?   
  • SWEI
    SWEI Member Posts: 7,356
    Retrofit floor heat

    pretty much requires heat transfer plates and insulation underneath the tubing.  Omitting either is just plain foolish.

    Heating capacity will depend on the thickness of the T&G and (to a lesser extent) the species of wood.  As long as the bottom surface is flat, you will get decent performance out of extruded aluminum C-plates (sometimes called Omega plates.)  If your joists are on 16" centers, plan on two runs per joist bay.  Make sure you have enough capacity (maximum floor surface temp 85ºF) before you leap.
  • Gordy
    Gordy Member Posts: 9,546
    Floor output

    Another option is radiant ceilings which will actually have more output. Give it some thought if you are removing ceilings.