Radiant retrofit - oil to geo

Discussion in 'Radiant Heating and Cooling' started by LongshoreGeo, Mar 4, 2014.

  1. LongshoreGeo

    LongshoreGeo New Member

    I am looking for some advice from the radiant gurus for a project on Long Island. I am looking at a geo retrofit project where client has a total of 4 existing zones of heat/ac. Currently heats with oil. Second story is 4-ton AC and hot water coil for forced hot air (we plan a split geo system here). Basement is a 1.5 ton AC system with hot water coil for heat. Getting a line set to the basement air handler will not be possible, so homeowner is looking to keep that system (and run the coil with hot water from geo??). First floor has two zones existing. One area is heated with radiant (existing ac load is 2.5 tons for this zone) and the second area on the first floor is heated with hot water coil / air (planning a package unit here).

    My big conern here is the radiant and providing hot water to the basement hot water coil. There are no design documents available for the radiant so we don't know tubing layout / spacing. It is my understanding that geo-radiants systems typically run at lower temps and may require tighter spacing between the tubing. Can we successfully retrofit the radiant with geo running at lower temps or will we need to have high temp system to match existing?

    At this point we are just trying to determine if the retrofit is reasonable and establish a back of the napkin budget for homeowner to consider. Also, if anyone is looking to team on this, I would be open to that also.
  2. DavidCraig

    DavidCraig Member

    Perhaps I've not had enough coffee yet this morning, ... are you saying they have 4 different heating setups and radiant is just 1/2 of first floor?
  3. LongshoreGeo

    LongshoreGeo New Member

    yes, existing is 4 different heating systems, one of which is radiant for part of the first floor. The other three zones heat with hot water coils and forced hot air, all being fueled by an oil fired boiler.
  4. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    If the project justifies it, you can rent an infrared gun and you can sort out the spacing on the tubing. Combine that with a room x room heat loss and you then compare your potential btu output with the room's requirements.
  5. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    Longshore there are great minds here to help. It really is just a math problem. You can run a room by room load to determine their requirements. You can establish what you have in each room for delivery and compare what it will produce at lower temperatures (key to geo radiant success). Next are strategies of augmentation can we get ducts everywhere for AC? Then we can start with radiant heat and switch to hydronic or DX air handlers for second stage.
    Next is control strategy. The system you propose is somewhat like Tamar's and the pitfalls are the same for you and your client. You can get everything else right and tank the controls and it will perform badly.
    Best of luck.
  6. LongshoreGeo

    LongshoreGeo New Member

    thanks for the feedback guys. How about a CM high temp water to water to provide for the radiant and DHW? Have you guys installed many of these units? Joe, you read my mind. I am leaning toward augmenting this zone with a water/air package unit that could provide additional / back up heating for the radiant. At this point I am just strategizing so we can come up with a premininary budget before the analyze the loads and work up a design. Thoughts?
    thanks. Matt
  7. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader


    Joe is right this is just a math problem. I can look over your work if you wish.

    Once the math is done then you know how to pipe what you need.

    Caleffi just sent me a new Idronics on how to control hydronic systems it is a free download, and well worth a look.

    To the question of mapping the radiant floor. I, (Stephanie did the work) have shut down a high mass floor and then re-supplied very warm water and tracked the loops with a point and shoot infrared thermometer.


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