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Thread: Help sizing geo

  1. #1
    Join Date
    Jul 2014
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    Kansas
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    Help sizing geo

    I have a job that they want geo. I live in Kansas where there's a wide temperature difference. If my calcs are coming out to a heat loss of 53000btu/hr and my heat gain is 29000btu/hr, I know I probably should size for the greater but will the geo get the humidity out in cooling? Also they have radiant in the garage and basement 35000btu/hr to add more interest.

  2. #2
    Join Date
    Feb 2009
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    Portland OR
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    So is the 53,000 BTU per hour for the whole home or is that part of the garage and basement. Or is it that the garage and basement are an additional 35K BTU per hour.
    First I would put in a two stage 4 ton, use the electric backup for a little bit of the heating load since a 4 ton should get you close to 44K of usable heating capacity. Then I would put in a 3 ton water to water for the radiant floor.
    Since you are asking this question I assume you are not certified for a Waterfurnace 7 series which a 4 ton would be perfect for this application. The biggest issue you run into with cooling is not being able to dehumidify if your oversized, I dont' know how humid Kansas is in the summer.
    Do you have enough ductwork and airflow for the geo? Are they converting from Propane... Oil... Natural gas... Existing Heat Pump... Electric resistance heat?
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  3. #3
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    This is new construction. The 53000btuhr is what I came up with for the house. The garage is coming in about 18000 and the basement at 17000btuhr. I was hoping to get set up with a combination unit. We can get humid here. Like last wk I seen 80% probably 50-70% would be average though.

  4. #4
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    The other option is to still do the 4 ton dual stage but add a dehumidier to the house to help control the humidity during the AC season yet provide 95% of the heat in the heating season.
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  5. #5
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    Or hot gas reheat
    i belong to peta ... people eating tasty animals. all my opinions are just mine.

  6. #6
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    This is probably an elementary question, but would I need a separate loop field if I went with 2 units? I don't think I'll talk the homeowner into spending that much.

  7. #7
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    Quote Originally Posted by plumedic View Post
    This is probably an elementary question, but would I need a separate loop field if I went with 2 units? I don't think I'll talk the homeowner into spending that much.
    No, you can do as many units as your pumps can handle and the BTU's your loop is designed for. I have a 7500 sq foot home with 4 geo systems on one loop. Two for water heating and two for air.
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  8. #8
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    Interesting. So can you control priority of the unit using the loop or is that not necessary?

  9. #9
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    Quote Originally Posted by plumedic View Post
    Interesting. So can you control priority of the unit using the loop or is that not necessary?
    There is no priority, you just need to make sure the loop can flow for all units
    Lets say you have a 2 ton that needs 6 GPM and then a 3 ton that needs 9 GPM, that just means your loop must flow 15 GPM total so that if both units are running you still have full flow. The loop also needs to be able to handle the extraction or rejection of heat based on standard loop design, so if you put in 2 bores at 200' for a 2 ton, if you have a 2 ton and a 3 ton then you need 5 bore holes at 200' for the two systems.
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  10. #10
    Join Date
    May 2005
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    Quote Originally Posted by SkyHeating View Post
    There is no priority, you just need to make sure the loop can flow for all units
    Lets say you have a 2 ton that needs 6 GPM and then a 3 ton that needs 9 GPM, that just means your loop must flow 15 GPM total so that if both units are running you still have full flow. The loop also needs to be able to handle the extraction or rejection of heat based on standard loop design, so if you put in 2 bores at 200' for a 2 ton, if you have a 2 ton and a 3 ton then you need 5 bore holes at 200' for the two systems.
    What's the flow path for the loop through the various units? Do you have them in series and basically put the most important unit first? Do you have a series of ball valves in a parallel header?

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