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Hot water heater for floor heat...

Can someone help me with this? Can you use a regular domestic hot water heater or a tankless hw heater for floor heating? I will use a seperate hw heater for the domestic hw. I know to some point it will work but will it be effecient or will the hw heater just kick on and off causing my bill to go up? Thank you for any help you can give.

Comments

  • kevin coppinger_4
    kevin coppinger_4 Member Posts: 2,124
    you can...

    and I have if it is real budget job. I would not do the tankless water heater...to much $ for too many issues to over come. Tank type would be better or a boiler would be your best choice. kpc

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  • Boonierat
    Boonierat Member Posts: 58
    Water heater for radiant heat

    Quick answer is YES you can.
    Cautious answer is "put-ALL-your-ducks-in-a-row";
    you will be using an appliance as a 'boiler' that is NOT rated as a boiler.
    If you're going to be subject to local code enforcement inspections they may pick you up on that. Might be wise to check in with those folks in the 'front-end' and save yourself some grief down the road. 'Most' inspectors are willing to offer you some guidance.
    Stay loose; stay well,...................Nels
  • jp_2
    jp_2 Member Posts: 1,935
    load?

    how large is the load? if it is under 15,ooo btu I see no real other solution!
  • zeke
    zeke Member Posts: 223


    Depends on the load and whether it is fuel fired or electric. If electric, you have serious operating cost problems. For fuel fired, you can only get 160 deg maximum out of the HW heater and from what I have seen so far, this translates into about 170BTU per foot of baseboard, so for a modest load like 10,000BTUH, you would need about 58 feet of baseboard. I had this idea and abandoned it in favor of a 1.5KW oilfilled heater which puts out 5000BTUH, my needs, even though the cost of electric heat is twice that of fossil fuel.

    I need 5000BTUH, so from the above, I would need 27 feet of baseboard at a cost of $250 plus the circ pump, check valves and fittings and thermostat, another $350 plus piping and insulation plus my time ($1.00/hr) or a total cost of $800.
    Looking at the economics, the cost of the electric heater is about $75, and 2500 heating hours/year x1.5KW=3700KWH. At $.20/KWH, my seasonal cost for electricity is $740. For fossil fuel , it would be about 2500*5000*$2.5/(120,000*.8)= $325 (where I assumed $2.50/gal for fuel oil comparable to gas and a heater eficiency of 80%.

    So I would save $400/year and get my money back in 2 years. But, the cost of a dedicated oil fired unit is about $1000 which probably has 10 year life( I'm guessing here although at 160 degrees this could be too high) makes this decision questionable and so I abandoned it.
  • ALH_4
    ALH_4 Member Posts: 1,790
    heat source

    I would look at the Bradford White Combi2 and kill both birds with one stone.

    If electric, Laing heaters are a very nice option.

    Hot Rod did an article on exactly this in Plumbing Engineer this month.


  • A 160 water temp gets you a lot more than 170/ft out of baseboard. If you're using regular Hayden, rated at 720/ft @ 200 degree water temps, you can get almost 360/ft out of it with 160. 250/ft at 140 SWT. 115/ft at 120 SWT.

    Not central to your point, but to address that, yes, you saved some money, but now you have an oilfilled radiator. The parent is talking about radiant floor, not baseboard. You made the right choice, perhaps, instead of baseboard. But radiant floor would ratchet that comfort up a notch.
  • I used to heat my home wiht a water heater...

    Then I installed a REAL heating appliance and reduced my gas bills by an additional 30 %.

    It's your money. Spend it wisely now, or wastefully forever...

    ME
  • zeke
    zeke Member Posts: 223


    > A 160 water temp gets you a lot more than 170/ft

    > out of baseboard. If you're using regular

    > Hayden, rated at 720/ft @ 200 degree water temps,

    > you can get almost 360/ft out of it with 160.

    > 250/ft at 140 SWT. 115/ft at 120 SWT.

    >

    > Not

    > central to your point, but to address that, yes,

    > you saved some money, but now you have an

    > oilfilled radiator. The parent is talking about

    > radiant floor, not baseboard. You made the right

    > choice, perhaps, instead of baseboard. But

    > radiant floor would ratchet that comfort up a

    > notch.



    quote"A 160 water temp gets you a lot more than 170/ft out of baseboard. If you're using regular Hayden, rated at 720/ft @ 200 degree water temps, you can get almost 360/ft out of it with 160. 250/ft at 140 SWT. 115/ft at 120 SWT."
    ----------------------------------------------------------
    NRT Rob,
    Could you please provide a link to that regular Hayden. It must have huge surface area to get those numbers, I would be very interested.


  • I don't have a link, but it's not even as good as regular Argo Panel Trim, which is rated for 920 BTUs/ft at 200 degree water temps.

    The only baseboard I might think is as weak as you're suspecting would be something like slimline or other non-finned baseboard units.
  • william_5
    william_5 Member Posts: 62
    my two cents

    yes it can be done but what is it going to cost you?
    a peerless with a good burner firing at 1.00 gal..you will loose about 400 to 500deg up the stack you could also add extra zones down the road if you were to increase your house. to days boilers have as little as 15 gal or less water in them. a 30 gal hot water heater you are heating up more water than you need. as to installing a hot water heater for one zone may be two?? fireing at .75 a gal the stack temp could be a high as 750 deg going up the stack
    you can do the math
    william


  • william, except in extreme cases, heating too much water is not really a problem. That just means you have a stored mass of heated water, so it's that much longer before you have to fire again. Most heat source run better if they are allowed to have a real burn, no?
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