Help with Geo sizing

Discussion in 'Quotes and Proposals' started by JC115, Nov 18, 2012.

  1. JC115

    JC115 Member

    I am building our new house soon (owner builder) and installing geothermal. I wanted to get some input on the sizing of the gshp. I will attach plans for those interested in helping. The house is located near Cincinnati Ohio, 45040 will be the zip code. I am working with a HVAC company (friends of family) who has installed geo, but they sub out the drilling. This will be a horizontal slinky installation which I will be installing and need help calculating as well we will get to that later i suppose.
    The quote they wrote up for me is for a 4 ton Tranquility 27 series 2 stage ( ttv049agc01alks ) with 15kw electric, and Hot water generator.
    So what do you think about the unit and the size? Should I go with a two stage unit?

    Here are some specifics on the house to be.
    - 2000 sq foot ranch with full basement
    - Insulation will be blown in cellulose in walls and ceiling
    - R49 in ceiling and R13 walls
    - It is a walkout basement, that will be finished eventually and well insulated
    - These are not the final plans, we are making some changes, but these should be close enough to get a good idea.

    Thanks for reading -JC

    Attached Files:

    Last edited: Nov 18, 2012
  2. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    Do you have a digger?

    What type of soil do you have?

    Did the "friends of the family" do a heat loss and heat gain? What where the numbers? Was 4-tons the next size up?

    I know your area well weather wise, but have never dug holes there. My daughter and grandsons live inside the I-275 beltway.

    Have you looked at radiant delivery?

    What is your cheapest fuel?

    I guess I need more data to be of much help.

  3. JC115

    JC115 Member

    The soil type is Xenia Fincastle according to a soil survey,
    I will work on getting the heat loss numbers.
    I have considered radiant delivery it sounds nice, but don't want to mess with it due to budget.
    I will have Natural Gas at the house, it is currently $0.504 ccf
    electric is $0.0221 would it be logical to have natural gas as backup heat instead of electric?
  4. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    I'll have to look up that soil type

    Radiant delivery can provide up to 30% in delivery savings, and that does not count the increase in comfort. Google Robert Bean for a great look at why and how radiant heating and cooling works. Thanks to the group at Tekmar, also Canadian, radiant cooling used to remove sensible heat is now easy. One still needs an air handler to remove the latent heat. If you can not find either of those sites let me know and I will find you a link.

    If you read some of my posts here you will find I have a water to water bias.

    Go Bengals. 21 to 3 at the half.

    Having natural gas available I would design a water to water system with desuperheater to help with domestic hot water and then add a buffering tank and finish DHW and provide auxiliary and emergency heat with a tankless water heater. A Tekmar 406 would make controlling the comfort easy.

    Last edited: Nov 30, 2012
  5. JC115

    JC115 Member

    Mark, I have read most of your post, and even talked to you on the phone before, I think radiant heat is very cool, and would consider it on a future build, but it is not in the budget for this house. Plus I am trying to keep things as simple as possible since this is my first house, and I am hoping the process goes as painless and quick as possible. But I do want the house to be efficient, and I want to learn to install the Horizontal loops.
  6. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    I thought we had spoken

    You may call again if you wish.

    I would then have you look at Unico Systems as it is very installer friendly once designed. It also is very water to water adaptable. Allowing for future staple-up radiant. I don't give up easy.

    Get the heat loss and gain and we can look at the loops.

  7. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader


    Learning to install the horizontal loops is not that complicated, and is what most people want to take on.

    Learning how much to install is the complicated part, and is a bit more involved with numbers and all.

    We can't go very far down any path unless you have a heat loss/heat gain on the house.
  8. JC115

    JC115 Member

    Here we go, the heating load is 35674, the cooling 31891
  9. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    If there is oppurtunity to reduce load, perhaps you could get cooling load down to 2 tons and augment heat with a little auxiliary. Otherwise you are rather genorously sized with a 3 ton.
  10. JC115

    JC115 Member

    Also consider the basement area is not included in these numbers. It will be finished eventually.
  11. JC115

    JC115 Member

    2.5 ton?
    3 ton two stage?
  12. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    your basement is part of the load now and will add little (unless your ducts are insulated against an unconditioned space).
  13. JC115

    JC115 Member

    Considering just the existing numbers what size would you all recommend?
  14. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    Not knowing your cost/kwh, budget or installation costs, it is difficult to say "X" is best.
    If installation cost is high and kwh cost is low, then I would likely try to insulate down to a 2 ton. If installation cost is low a 2.5 or 3 ton may offer better bang for the buck.
    As it stands a 2 ton is not adequate now, so 2.5 to 3 ton system is indicated.
    I don't suffer the same notion as others that a single stage unit is a poor choice in all applications, nor do I think you will have a discernable dehumidification penalty for using one.
    If you wish to go 2 stage and 2.5 ton CM has a TZ30, but you will likely find operating cost and installation cost very similar to a 3 ton.
  15. JC115

    JC115 Member

    My installation costs should be relatively low since I'm doing the outside work, I'm thinking 3, I am going to have my hvac guy make some changes to the load calc to be sure.
  16. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    I know the Cincinnati weather and if being paid to design this I would go 3-ton water to water using Unico or other high V delivery. One could include a chilled water coil for cooling and most of the heating. One could add an additional hot water coil for emergency and aux. heat.

    I would install a 3-ton loop field. What and how I would bury would depend on the dirt and the digger. When we worked with mtrentw at his home in Maryland the digger could tear up the yard faster than we could make slinkies. In Delaware, Ohio we did not have the room to go out and back so we turned 500' rolls of pipe into 65' x3' slinkies. Both system used loop field manifolds with larger sized transportation pipig between the loop field and the home.

    You can still call or email me if desired.

    Doing what I propose would allow for radiant delivery in the future.

    I have been seeing the use of the spray foam insulation products slaying my heat loss/gain numbers here in Northern Ohio. If you can squeeze the budget for an energy extra that would be a worthwhile investment. This is an internet SWAG and I will not be held liable or accountable for your actions and results.

    warm regards,


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