Best heat source for zoned under floor radiant heat.

ED 3000 Posted By ED 3000, Nov 24, 2018 at 4:50 PM

  1. ED 3000

    ED 3000
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    Dec 23, 2015
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    Plan to keep the existing boiler and cast iron radiators in service until I see how this goes.

    I've read about people using domestic hot water heaters or tankless boilers.

    The floors are 3/4" pine tongue and groove, only. So I think the radiant pex will go right through, and I can get to 3/4 of the first floor right from the cellar.

    Any suggestions regarding the heat source? The gas line is easily accessible in the cellar where it's going.
     
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  2. maple1

    maple1
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    Not sure I am getting the question.

    If you have a NG line, then a NG boiler?
     
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  3. ED 3000

    ED 3000
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    Dec 23, 2015
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    I have an old, terribly inefficient ng boiler. It feeds big old cast iron radiators. They work, but burn up tons of fuel and are never comfortable. The lines are the steam lines, just converted at some point from steam to hot water. Way oversized and wasteful.

    My plan is to bite off small chunks of this hydronic heat update. I can install pex under most of the first floor, in several stages. First, under the living room. Next, under the kitchen. Finally, I'll probably have to use radiant emitters in the second floor rooms.

    Finally to my original question: I'm not going to use the old boiler for this, mostly subfloor radiant system. I'm gonna set up a parallel system with the old radiators in place, until I get it figured out.

    I've read about people using domestic hot water heaters, or modern tankless water heaters for this application. Just looking for some thoughts on the best way to do this.
     
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  4. maple1

    maple1
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    We don't have NG here so no direct experience - but I would likely just get a new modern efficient NG boiler. I think they are condensing? And insulate the bejeebers out of all my piping. Not sure I see any advantage to trying to use a water heater - you would likely want the house heating horsepower of a boiler since that is what they are designed for. At some point at least. Although I have no clue about equipment costs for any of this.

    I'd also consider still using or re-using the cast iron rads. Those can put out some comfy heat at lower water temps. You could replace the big piping with smaller stuff or pex, during your overhaul, maybe?
     
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  5. ED 3000

    ED 3000
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    Dec 23, 2015
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    I think everything you said makes sense.

    Upstairs, keeping the radiators will likely win the day, they are there, free, and will work with a minor retrofit to the hardware.

    The downstairs radiators are going in favor of the subfloor radiant lines. There is a real issue with how much space they are taking up in my tiny rooms. And the downstairs is adequately heated with the wood stove.

    Probably would be best to just update the whole boiler, from an efficientcy standpoint. I'm pretty sure that is gonna be the expensive part. Which is why I'm exploring lower cost alternatives.
     
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  6. maple1

    maple1
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    I would love to be able to hook to NG. It isn't here, though.
     
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  7. ED 3000

    ED 3000
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    Dec 23, 2015
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    We are lucky with that. Previous owners were forward looking and ran the line many years ago. Some neigbors are paying big $$$ to tap into the main recently.
     
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  8. fbelec

    fbelec
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    you don't want to try to use a old boiler for low temp heating. radiant is mad to run at about 120 degrees. if you run a old boiler that way it will wind up a flood because it will rot out. you can use a water heater i know someone that is using that now since it is a closed system the heater is 25 years old. just keep in mind the the water heater is 80% eff. you are better off using a condensing boiler because it is comfortable at the low temp of a radiant system. you could even set it up to run on solar hot water.
     
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  9. zrock

    zrock
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    Why not go wood? Those outdoor wood systems kick out a lot of heat.
     
  10. ED 3000

    ED 3000
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    I considered wood, but inside, with a dual fuel system. Going outside to load the fire scares me.

    Due to this old houses' configuration, can't see how to fit what I'd need in the cellar, and just isn't in the cards to put an addition on to house a wood boiler and storage.

    If we ever build a house on bigger acreage, I'd probably make this the central part of our heating infrastructure.
     
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  11. zrock

    zrock
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    Outdoor wood boilers are already in their own little house. Drop and go.. they also need to be several meters from structure for fire purposes

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  12. ED 3000

    ED 3000
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    Dec 23, 2015
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    Still have to go outside to get to the little house.

    I've looked into it, and have nothing against them, I am just not rugged enough to trek through the cold, wet, and snowy, any more than I do already to keep the inside stove fed.

    It's a good suggestion, an owb is just not for this odb.
     
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  13. zrock

    zrock
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    Lol... I know the feeling

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  14. CaptSpiff

    CaptSpiff
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    I've worked on many of these many many many years ago. I personally love older NG steam boilers with millivolt thermostats. A little annual upkeep and bulletproof after that. And you always have heat during a power outage. But you're past that....

    You've got a conversion to (I assume) forced hydronic with the old steam radiators. How does your system return its water?
    I would consider, if you love the old radiators, to replace the old steam pipes with PEX as a long term solution.

    For the proposed under floor heating, you've got to get the temperature of the circ water down to 120 deg from the 160 to 180 your boiler wants to put out. I've solved this in the past by installing a "SuperStor" tank normally used for domestic potable hot water. I ran that as a separate zone off the boiler, and that fed the under floor in however many zones you choose.

    I've also done a few redneck installs where I've used a standard 40 gal electric water heater as the storage/mixing tank, instead of the SuperStor. Feed it as a boiler zone and then the under floor from the mix. That gets a bit tricky with the controls, but it'll save you $6-800 if things are tight.
     
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  15. maple1

    maple1
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    Should only need a mixing valve for the floor.
     
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  16. ED 3000

    ED 3000
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    Dec 23, 2015
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    Now we're talking.

    I don't love the old radiators. My rooms are very narrow, and the radiators eat up just enough real estate to make modern life difficult. I'm gonna remove the ones on the first floor. I'm literally fighting for every inch of floor space in my living rooms and kitchen.

    On the second floor, I think I'll do exactly as you recommend, and feed the existing radiators with pex. I can't do radiant floor on the second floor, as I've removed the plaster from the first floor ceiling and intend to leave the first floor ceiling as exposed beams.

    I'm totally in over my head here, but I guess that's always the case with my projects.

    I'd still like to figure out an upgrade to the old boiler that won't hurt too much ($).

    Regarding returns, see the picture.

    IMG_20181129_201526210.jpg
     
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