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  1. #1
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    Geothermal used with radiators

    Existing heating system in the house is an oil fired hot water boiler with fin type radiators. Boiler is about 40 years old and still working fine. Uses about 800-900 gallon of oil for heat and domestic hot water for the year or about $3000/yr. IIRC boiler is a 150000 btu unit. House currently has 2 zones 1 which covers an addition that is only used during Christmas and special occasions, thermostat stays set at 50 most of the time, remaining main part of the house is 70 from 5am-10pm then 50 for the night. Space heaters in the bathrooms probably add another ~150/month say $1000/year.

    Are any companies making geothermal units which can be used with the finned radiators?

    While installing I likely would break the main house up into at least 4 zones kitchen/living/downstairs bed, downstairs bath, upstairs bedrooms, upstairs bath.

    There is about 20 acres to bury tubing so that isn't an issue, I'd be doing the trenching and install.

    Replacement of 50/60s vintage radiators with more efficient units is also possible.

    Thanks for any input.

  2. #2
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    Aug 2002
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    Southold, NY
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    Geo will not give you the water temperatures you need.
    It can be used for forced air heat and Supplemental hot water.

  3. #3
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    Dec 2004
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    A water source heat pump with a water loop can be made to work, but you will need to at least double the amount of existing radiation surface, that will allow for much lower temperature water.

    By the way, their really isnt anything more effective at radiating heat then the existing cast iron radiators, lots of surface area.

    If they want to do a major renovation, you can put radiant tubing on the ceilings or in the walls, same as you would a concrete floor and have a plaster contractor float that in.

    Radiant ceilings is the way many of the older mid rise buildings in Chicago were done back in the 30s-50s. Works really well. Just have to be careful when doing trim work or any penetrations.



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  4. #4
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    Thread Starter
    Quote Originally Posted by heatingman View Post
    A water source heat pump with a water loop can be made to work, but you will need to at least double the amount of existing radiation surface, that will allow for much lower temperature water.

    By the way, their really isnt anything more effective at radiating heat then the existing cast iron radiators, lots of surface area.
    I didn't think it would work but just making a wild assed guess I'd figure the system would pay for itself in 3-5 years in energy savings. Figured it wouldn't hurt to check. The radiators are the sheet metal fin and tube not cast iron. I'd say it wouldn't be difficult to get 2-3 times the surface area in the available space, thus wondering about more efficient modern units.

    Quote Originally Posted by heatingman View Post
    If they want to do a major renovation, you can put radiant tubing on the ceilings or in the walls, same as you would a concrete floor and have a plaster contractor float that in.



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    This is my family home built circa 1910. It wouldn't be economically feasible to redo the ceilings and walls, already been done with walls and attic filled with loose rock wool insullation. Converting the house to a forced air system isn't viable as far as I'm concerned. Second floor might be doable with all vents and returns in ceiling, but it would be a nasty job. The first floor would be a mother and require a special crew of very small people. It was tough for me to get around under the house 30 years ago when I was 20-25 lbs lighter and 4 suit sizes smaller. There were many places where I had to get all the air out of my chest to go under a joist and breath between the joists.

    Was sick and while laying there watching TV caught a segment on geotherm and this was just me wondering if there was a replacement that would put a big dent in the heating bill long term. IIRC and I did my calculations correctly it was going to be well over 5 years to recoup the cost to replace the existing boiler at the current rate of oil usage and cost.

  5. #5
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    Jan 2012
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    You’re boiler is way oversized and the reason why you’re using so much oil.
    Especially true if you can recover from a 20 degree setback.
    Properly sized/properly installed modern boiler would save you money.
    If I do a job in 30 minutes it's because I spent 30 years learning how to do that in 30 minutes. You owe me for the years, not the minutes.

  6. #6
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    Sep 2007
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    They also make boilers fueled by wood pellets, and models that burn firewood very efficiently.
    UA Local 32 retired as of Jan 2020

  7. #7
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    Dec 2004
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    Quote Originally Posted by packratt View Post
    I didn't think it would work but just making a wild assed guess I'd figure the system would pay for itself in 3-5 years in energy savings. Figured it wouldn't hurt to check. The radiators are the sheet metal fin and tube not cast iron. I'd say it wouldn't be difficult to get 2-3 times the surface area in the available space, thus wondering about more efficient modern units.


    This is my family home built circa 1910. It wouldn't be economically feasible to redo the ceilings and walls, already been done with walls and attic filled with loose rock wool insullation. Converting the house to a forced air system isn't viable as far as I'm concerned. Second floor might be doable with all vents and returns in ceiling, but it would be a nasty job. The first floor would be a mother and require a special crew of very small people. It was tough for me to get around under the house 30 years ago when I was 20-25 lbs lighter and 4 suit sizes smaller. There were many places where I had to get all the air out of my chest to go under a joist and breath between the joists.

    Was sick and while laying there watching TV caught a segment on geotherm and this was just me wondering if there was a replacement that would put a big dent in the heating bill long term. IIRC and I did my calculations correctly it was going to be well over 5 years to recoup the cost to replace the existing boiler at the current rate of oil usage and cost.
    If the only radiation is fin tube, then you can certainly upgrade that. Myson, buderus and a few others make stamped steel wall hung radiators that can provide alot of surface area in a small space.

    Typically fin tube will max out at about 600 btu per lineal foot with an average water temp of 170 and a space temp at 68 or so. Which is about 100 degree difference.


    I would think geo would get a max temp of 140 output, making the average around 130 which is only around 60 degrees above space temp. Which is where the 2 x radiation comes from.

    Take a look at the myson or buderus type radiators and look at the ratings for 130 degree water.

    You may be able to do it, but you would most definitely need to do repiping.

    Might not be worth it. Not sure.




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  8. #8
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    How many people in the home? You can probably save a good bit of oil by switching to an 80 gallon electric water heater. And converting the boiler over to a cold start boiler. Along with having an outdoor reset installed.
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  9. #9
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    I can't agree with you @beenthere. Depending on electric rates, an indirect will cost less to make hot water, especially with a modern, properly sized boiler like an EK (with or without storage tank-depending on OP's needs).
    That boiler is very oversized, then, removing the dhw, then add outdoor reset, and it will be short-cycle (poor efficiency) city.
    If I do a job in 30 minutes it's because I spent 30 years learning how to do that in 30 minutes. You owe me for the years, not the minutes.

  10. #10
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    Double posted it...
    If I do a job in 30 minutes it's because I spent 30 years learning how to do that in 30 minutes. You owe me for the years, not the minutes.

  11. #11
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    Quote Originally Posted by STEVEusaPA View Post
    I can't agree with you @beenthere. Depending on electric rates, an indirect will cost less to make hot water, especially with a modern, properly sized boiler like an EK (with or without storage tank-depending on OP's needs).
    That boiler is very oversized, then, removing the dhw, then add outdoor reset, and it will be short-cycle (poor efficiency) city.
    Electric water heater doesn't have as much standby loss as an oil boiler.

    As a cold start boiler, it won't be short cycling, as it will be heating up a fairly large amount of water.
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