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sizing electric hot water heater for small radiant job

DKHDKH Member Posts: 14
Your formula is correct.(3.4144)I would doubt that you will have the recovery rate and capacity to get the required btu output to heat even the smallest radiant job. Besides the energy cost vs benefit should be looked at.Do the numbers.I dont think it is practical.


  • pat_3pat_3 Member Posts: 89
    sizing electric hot water heater for small radiant job

    i'm pretty sure the conversion is ,watts x 3.4 = btu's,but is that my only concern ,or does the storage capacity come into play also?
  • MolsonMolson Member Posts: 6

    You can't rule out electric. Do the numbers. In my area of Canada the cost of electricity isn't that bad. Also if you have low water design temperatures you have the advantage of lower operating temperature from electric-no flue gas condensation problems or mixing valves. Electric can be simple direct piping. EVERY installation is different and every method has its pros and cons.
  • hrhr Member Posts: 6,106
    Electric options

    I've done a number of small electric water heater floor warming systems. A 6 gallon electric with a 1650 W element will give you around 5600 BTU/hr. Plenty for most bathroom tile floors or small kitchen floor warmer.

    4500 watts will provide 15,000 BTU/ hr. I prefer gas or LP but it is not always an option for numerous reasons.

    Here are a couple of my bathroom floor warmers.

    hot rod

    hot rod

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  • pat_3pat_3 Member Posts: 89
    what will work

    if the wattage of the element converted to btu's meets the load of the area to be heated ,what determines the neccesary storage capacity of the unit? i've done a few systems with 6 gallon electric heaters with no problems to date...can i go smaller?
  • hrhr Member Posts: 6,106
    The larger capacity

    will provide less on off cycling of the element. More of a buffer tank effect. My small electrics are one zone one temperature, generally two or three short loops (under 200'). I like to do the tile shower walls on one loop and one or two for the floor depending on the room size. I do the deck around a tub if they use a drop in with a tile deck around it. This also makes for a nice towel warming spot on the warm tile surround.

    I run the circulator constantly and use either a setpoint control or dual sensing wall stat and reley to turn the element on. A small pump is all that is needed a 15-10 Grundfos is generally plenty. Price and availability wise 6 gallons are a good choice.

    Some customers like the digital wall stat, others are fine with a tank mounted setpoint control. I fine most people run the bathroom floor warmers year around. I lower the temperature on my setpoint in the summer a few degrees, but still try to run it a few 5 degrees above the temperature on the ac stat, just to temper the tile floor a bit.

    Give the owner an easy to adjust control and they will find the setting that best suits their comfort. Bathroom tile warming is my biggest sale. Simple and inexpensive and customers love warm tile bathroom floors. I have even won over a handful of GCs that now include this in all their proposals.

    hot rod

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  • DKHDKH Member Posts: 14
    warming/heating ?

    are we talking floor warming systems or systems to provide complete heat loss requirments
  • pat_3pat_3 Member Posts: 89

    most of the small electric heater jobs are for warming tiled areas in homes that are hot air heated,but i would like to know the capacity of the small elctric heaters for heating purposes
  • JIM F.JIM F. Member Posts: 82

    curious? no expansion tank. water feeder..
    do you just fill and bleed it and let it fly. do you use a low water cut off or pressuerw switch to shut it down...
    looking at the picks very minamal materials
    profitable addition if it works..
    and i'm sure it does or you wouldnt have put it in.

    jim f.
    trying to learn every day of new techniches
  • Art Pittaway_2Art Pittaway_2 Member Posts: 80
    Figure the BTU's

    and with electric thats watt you get. As long as the heater element will put out more than your floor needs to heat the room it will heat. Did an indoor basketball court with a 20 foot ceiling (1/2 court) and one water heater heats it nicely. We couldn't use gas because there was nowhere to vent and there was plenty of electrical capacity and room for the heater. We could have used an electric boiler but the load was small and the boilers were bigger than needed. Check your load and look for what fits the project.
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