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Radiant floor heat from steam boiler?

DanHolohan
DanHolohan Member, Moderator, Administrator Posts: 16,598
in THE MAIN WALL
has been there since day one. It pays to wander off the Wall. :-)
Retired and loving it.

Comments

  • Paul Llewellyn
    Paul Llewellyn Member Posts: 2
    Radiant floor heat from steam boiler?

    Forgive me if this has been covered before but I could not find a clear answer in the old message threads.

    We have a one-pipe steam system in an 1800 sq ft house with an old (1950s?) W-M boiler. We are adding a 1200 sq ft addition with radiant floor heating. The contractors and their heat guys say we need a separate hot water heater to power the radiant floors, even if we replace the boiler with a modern steam boiler.

    It looks to me like a new W-M steam boiler can be fitted with an exchanger to a indirect hot water tank -- why can't that same approach be used to provide hot water to the raidant floors? The heat guys I have spoken with say it will not work well because every time the radiant calls for 120 degree, some heat will escape up into the steam system. Who is right?

    Can this be done efficiently?
  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,598
    This part of the site

    will help you:

    Condensate Zone off a Steam Boiler
    Retired and loving it.
  • Dry Steam
    Dry Steam Member Posts: 32


    Wow .. Dan that's a great page!! Just when I think i've seen everything on a website you come around a surprise everyone..
  • charlie_16
    charlie_16 Member Posts: 9
    radiant from steam

    We also have an older WM steam boiler (only mid-90's vintage). Added a few hundred SF addition and went with radiant in that area. Our boiler (P-666 if I recall correctly) has accomodation for a hot water coil. I don't know all the proper terms perhaps, but an ?aquastat was put in place so that when making hot water it wouldn't fire past ?160 degrees. This temp is plenty for radiant, but won't make steam. I looked at the schematic given above to use condensate for hot water, but to get hot condensate, don't you have to make steam? What if you don't want steam? Not sure if I missed something there..
    Best of luck getting what you need/want.
  • kpc_40
    kpc_40 Member Posts: 62
    the boiler...

    will stop firing before the steam is made.
  • joel_19
    joel_19 Member Posts: 931
    buffer

    I have done this several times using a super Store indirect they work well because the coil is low in the tank. i like the 30 gallon model as it creates a heat sink of sorts to slow down the cycling on the radiant side.Then use a Tekmar to reset the tank works great and it's simple to do

    However at 1,200 sqft i might be thinking a seperate boiler as well. That's bigger than alot of homes! At that size you may need to upsize the steam boiler quite a bit. i'd be concerned about having a steam boiler with way more BTU's than is needed for the steam side because this can make for 1 unhappy steam system. plenty of info on here about the bad things that happen when you do that. So if i was the installer i'd be taking a good hard look at that boiler to radiator ratio before giving the thumbs up to adding the radiant on and upsizing the new boiler
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