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Steam Radiator Under the Floor

Is it possible to mount a steam radiator below the floor and have the heat be released from a floor mounted register? My boiler was redone by JStar in 2013. The install resulted in the creation of a wet return located along the basement floor as well as dry return snug up to the basement ceiling. All the basement supply mains are near the basement ceiling where they come off a beautifully piped drop header. Does anyone have experience mounting a radiator in between floor joists with a register opening into the conditioned space above? Do to the relative heights, the supply to the radiator may have a slight down pitch. The return can be down pitched as it can tie into the wet return located along the floor. Any issues here? Would it work if the radiator was properly sized to fit between floor joists? The goal is to eliminate the radiators from the kitchen footprint, but still get heat into the room. I would ask JStar, but he is no longer in the retail game. Thank you.

Comments

  • Kahooli
    Kahooli Member Posts: 112
    Get a convection type radiator(s) and build your duct channel and cold air return, or put them in your wall with a channel. You could reuse your existing kitchen pipes. This is actually my plan once I get around to gutting the kitchen.
  • Jamie Hall
    Jamie Hall Member Posts: 22,891
    You can do it. The trick is to remember three things: the steam has to be able to get in, the air has to be able to get out, and the condensate has to drain.

    In your situation, the biggest problem, I expect, is going to be finding a way to mount the radiator so that the condensate can all find its way to the outlet and drain out. Some under floor or ceiling mount radiators are very thin, relatively speaking, and one orients them so that the outlet corner is the lowest point (it doesn't have to be much lower, just lower). Then to let the air out, what will be needed is a vent on the return pipe before it drops down to the wet return. If the return goes directly to a wet return it doesn't need a trap (it does, obviously, if it ties into the dry return).

    Just make sure the whole thing is high enough so that it doesn't have any chance of flooding at the boiler cutout pressure.

    The question I would ask, though, is where is the air going to come from for this radiator to heat and have come up through the floor vent?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Ted_Ryan
    Ted_Ryan Member Posts: 36
    Jamie, thank you for the piping advice and question. I need to think about the cold air supply for the radiator to assist in output of heated air. I could leave the radiator bay open and draw basement air upwards into the kitchen, however, that might make it too easy for cave crickets to make it upstairs to the first floor :) On another topic, do you know of anyone serving the Poconos in PA?
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,300
    I think you would be better off without a radiator. Use a "Turbonics" fan coil unit. They are rated for steam and have a sensor to start the fan when the coil is hot. You wire this to a wall mounted thermostat. They have a fan and will take room air and heat it and return it to the room
  • Ted_Ryan
    Ted_Ryan Member Posts: 36
    Thank you for the Turbonics idea. I see that in addition to the below floor mount, they also have a unit designed to fit in the toe kick of a cabinet.
  • Ted_Ryan
    Ted_Ryan Member Posts: 36
    Contacted Turbonics. They said no go to running the fan coil of of a steam loop. They said the solder joints would not hold (do they understand low pressure steam???) Should I ignore this? Otherwise the only option is to connect a hydronics line off of the tankless coil in the boiler. Any thoughts? Thanks.
  • ChrisJ
    ChrisJ Member Posts: 15,439
    @Dave0176 and @EzzyT may serve your area, I'm not sure.

    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • SteamCoffee
    SteamCoffee Member Posts: 123
    The Turbonics unit need relatively high steam pressure, iirc 7psi+ to run correctly. Some old vapor systems had ceiling mounted rads to insure complete return condensation before the boiler, (Bromell??). Let us know what you come up with and how it works out...
  • Jamie Hall
    Jamie Hall Member Posts: 22,891
    The Hoffman Equipped system in the building I care for has ceiling radiators in the basement. They work fine.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,300
    Turbonics used to make steam units but I checked their literature and I guess they no longer do.

    2 options I see are a radiator hung in the basement ceiling inside a duct. You could probably use a duct booster fan to move the air. The air won't move without a fan unless you take basement air which causes other issues (like a shortage of boiler combustion air). This would take a somewhat rube Goldberg approach.

    using a tankless heater to make a hot water zone will work, and I think is a better idea

  • ttekushan_3
    ttekushan_3 Member Posts: 958
    We've done radiant with steam before.

    Frankly, I've never added or altered a steam heating system to incorporate hot water loops; only reverse engineered what was there so the new balances with the old.

    In particular, the radiant steam's always been in kitchens where the basement ceiling is accessible.

    FWIW, here's a scribbly drawing since I'm not near a desktop computer. You'll also see I'm nowhere near a t-square or engineers rule either! But here it goes. It uses a 2" black pipe run that traverses the joists, valved and trapped. Could be vented and taken to a wet return if a single pipe. I suppose small fin tube would work too.

    Remember that the same rules apply for maximum floor temp on a design day as with PEX radiant. It's just that total BTU's are delivered intermittently into a buffer space. Easy. No water loops necessary.
    terry
    Grallert
  • Ted_Ryan
    Ted_Ryan Member Posts: 36
    Thank you for the design schematic! This is definitely another design solution to provide the heat source without taking up limited floor space in the kitchen. I wonder if the area directly above the steam line would be noticeably hot vs. the rest of the floor. I currently have large steam mains running under the floor, but they are reasonably insulated and the bays above are open (there is no ceiling in the basement) so the heat can dissipate. I guess your design suggests placing the supply line under the cabinet along the wall and then letting the heat convect out across the floor. Very thoughtful and appreciated.