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Geothermal in a 1918 house with cast iron radiators?

Jim_65
Jim_65 Member Posts: 184
I would be concerned with the limited water temperatures available from a geo system. This would definitely limit your output of the rads. Although when we use a modulating condensing boiler with reset we can reduce the supply water temps and still match the heat load. However, you may need some kind of back up or second stage when you approach design conditions.

Did the contractor do an actual heat loss and compare it to the EDR of the existing Rads? What is your current heat source?

Comments

  • Mhosmer
    Mhosmer Member Posts: 3
    Geothermal in a 1918 house with cast iron radiators?

    I have a house that was built in 1918 that has large cast iron radiators. I don't believe that in the long term natural gas prices will go down so I'm very interested in installing a geothermal system (vertical closed loop). I've had the only geothermal company in our area out to give me an estimate.

    Our estimator, assures me that as long as we have cast iron hot water radiators that the geothermal system will work. I'm concerned that the BTU output from the geothermal will not heat the house. I live in the Cleveland area and the winters can get a bit extreme.

    Has anyone done this? Any advice?

    Thanks,

    Mark
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928


    I have not used geothermal but as long as you're reasonably insulated and weatherized I can certainly prove by demonstration that iron radiators can heat homes at VERY low temperatures! In the worst case the geo might need a bit of a boost in extreme weather.
  • Mhosmer
    Mhosmer Member Posts: 3
    Geo

    No he measured the house but not the existing radiators.

    The existing system is hot water, It's an old oil burner that has been converted to gas. I don't know the make.
  • Jim_65
    Jim_65 Member Posts: 184
    Geo

    I agree with Mike that you can make CI rads work with low temps. We do it all of the time. As we both stated with a back up or boost available would at least compensate for extreme weather/design conditions. We design/limit our geo systems to operate at least at 120* Max supply temp in our area.

    You could also entertain the idea of a High efficiency modulating condensing boiler that would match the load and use far less energy and the potential for fuel savings is there as well.

    I mentioned the EDR of the existing Rads to see if they could potentially be oversized. I have yet to come across a calculation chart to show Btu outputs at low entering water temps. But if you compare the heat loss to the output of the rads you should be able to calculate how much back up is necessary.
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928


    Jim,

    If you EVER find a low-temp chart for iron radiators, please share! I've been searching and searching for a LONG time.

    I truly believe that 2 btu/hr per degree of temp difference per sq.ft. EDR is a VERY safe value for temps below 90° and/or differential temps below 20° or so.
  • Jim_65
    Jim_65 Member Posts: 184
    Chart

    Mike,

    Mark is out of the office right now but I will ask him if he has such a chart available. He is pretty busy today due to some no heat calls plus it is snowing pretty good today with frigid Arctic temps. If he has one or knows of one I will pass it on.

    I like your example and I will run some comparrison calcs.

    Thanks!
  • clammy
    clammy Member Posts: 3,091
    geo therm

    I was just thinking to myself and wondering is your geo therm system vertical refregerant loops or a water loop system and also what refregerant is this system using r22 or it's furture replacement 410A .I've seen the intinal costs are big bucks .I beleieve for me i would go with a modulating condensing boiler and possible save some big bucks on the install costs and have a system that will definalty meet your heating requirements with no need for a back up system plus offer you some real saving in gas compustion .I would check out all my opitions before i leaped plus i would want a detailed heat lose and be sure that at th4e lower water temps that your homes heat lose can be made with out systems peace clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating
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