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Radiant floor heating

Unless you are changing fuels to one with a lower cost per net BTU, there will be no difference. Let me re-phrase that. If you now have a 50 gallon heater which has an inherent buffer and you switch to an indirect, there is a possibility that you may actually increase your propane usage due to cycling losses.

If your 1500 SF shop floor has an output of, say 20 BTUH per SF (just a guess for Richmond and that you may have some ventilation), that is 30,000 BTUH. Your 50 gallon heater may have a 40 to 50 MBH burner. A tankless may have at least that depending on model. I suggest you will still need that tank as a buffer to take out the swings from bursts of input. Your water temperature has to be pretty low and you really need to store those BTU's to be metered out over time. Hard to improve on the simplicity of a dedicated tank type HW heater.

I would suggest shopping different propane suppliers (not that you will save that much), perhaps buy a bigger tank to keep your cost per gallon low?

You could consider perhaps solar or a geothermal heat pump if your electrical costs are reasonable? Is oil an option or natural gas? Heck with a wood shop, you probably have some scraps, is a wood boiler an option?

Hard to give direction but you know the local availability better than anyone.
"If you do not know the answer, say, "I do not know the answer", and you will be correct!"

-Ernie White, my Dad


  • David Haywood
    David Haywood Member Posts: 1
    Radiant floor heating

    I live in the Richmond, VA area. I have a 1500 sq ft woodworking shop which is heated with hot water radiant heat. It works just fine, but the cost is high with propane. I am using a 50 gal water heater to do the job. I have been thinking of switching to a tank less heater, either propane or electric, but I don't know (1) if it would work in this application (2) if I would save any money considering the cost of the unit and residual costs.
  • Glenn Sossin_2
    Glenn Sossin_2 Member Posts: 592
    Other Problems

    Besides not saving any money of fuel - instantaneous heaters generally require minimum flow rates usually .75 gpm, and a high head pressure - more than you could expect out of most radiant installations unless you planned/designed for it. Because of the high btu output, these units generally look for a delta T in excess of 15F before they will even fire up regardless of flow. Remember, they were designed thinking you had 40psi + cold water coming into the unit that you were heating up by 50, 60 degrees or more.

    I agree with Brad - you are mis-applying the product and are likely to have excessive cycling. No fuel savings.

    Question - did you insulate under the slab? Did you use edge insulation? This system is going to run continually so you should have used at least 2" of structural foam to minimze heat transfer to the ground. What did you use ?
  • Gary Hayden_2
    Gary Hayden_2 Member Posts: 61
    Wood Shop = Radiant Floor Heating

    I live in Norfolk VA and will be heading up your way in a couple of weeks. I have a couple ideas that we can discuss - Please send me an e-mail if you are interested.

    1. Wood fired boiler
    2. Solar / Wood fired boiler combination
    3. Oil boiler

    If this 1500 square foot facility is for an every day business - I would think the investment for one of these scenarios would be a good one. For the wood fired boiler - depends on where you are located?
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