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  1. #1
    Join Date
    Jan 2010
    Posts
    55

    Ground or Air source heat pumps, and any general advice.

    (sorry for double post, I put in the wrong forum before)

    I have around 6 or 7 bids including a mixture of conventional air to air and ground source heat pump systems. It is for a 3100 sqft 1-1/2 story house in NE Oklahoma. I am pretty confident in the load calcs because just about all of them came up with about 4 ton downstairs and 3 ton upstairs. And surprisingly they are all about the same price for similar equipment, etc.

    Considering the tax credits and rebates from the utility the ground source system will cost about 21% more than the conventional. this is for vertical closed loop system. My questions are concerning approximate payback and just general issues. Some geo equipement sites I've used that account for electric rates, etc give me a payback of about 3 years and the contractor claims no more than 5 years payback. the units I would use probably are climate master packaged units and claim around a 27 SEER. The conventinoal units I'm comparing to are about 15 SEER Lennox or Trane equipment. If I go up to 19 Seer the cost difference is almost nothing after credits and rebates.

    So aside from the payback is the quality of the equipment comparable to the a high end trane or lennox, or any other higher end unit?

    One technical question I had involves using antifreeze in the loop. One contractor says he won't use it because it decreased efficiency & isn't necessary. The other disagrees and says he never installs w/o it and that methanol doesn't decrease efficiency. Finally, one said he would drill 4 holes using about 183'/ton and the other said 7 200' wells, so 200' per ton.

    Any general adivice or tips are appreciated. I think w/ the few thousand extra expense and rising energy costs the ground source may make sense. I just am not too familiar with it and wanted some advice.

    Oh, another thing mentioned by a contractor is that he installs very small strip heaters because they are expensive to operate and the heat pump capacity will always catch up, it just might not catch up quite as fast w/o the expensive strip heaters. In fact he says he turns his off in his own home and just deals w/ the occaisional couple degree temp drop. Any thoughts on electric backup heaters? (we don't have gas or any other source)

    thanks.

  2. #2
    Join Date
    Mar 2008
    Location
    northern Indiana
    Posts
    114
    So aside from the payback is the quality of the equipment comparable to the a high end trane or lennox, or any other higher end unit?

    Should last as long if not longer.

    One technical question I had involves using antifreeze in the loop. One contractor says he won't use it because it decreased efficiency & isn't necessary. The other disagrees and says he never installs w/o it and that methanol doesn't decrease efficiency. Finally, one said he would drill 4 holes using about 183'/ton and the other said 7 200' wells, so 200' per ton.


    If loop temperature gets into the 30's F you should have antifreeze.
    Methanol would be the best choice.
    7 200 ft walls = 400 ft per ton (pipe goes down and back up)
    Generally the longer the better, you should clarify that.



    Any general adivice or tips are appreciated. I think w/ the few thousand extra expense and rising energy costs the ground source may make sense. I just am not too familiar with it and wanted some advice.


    GEO is a great product provided it is installed properly and backed by the dealer!
    So pick your dealer wisely and not just on price.



    Oh, another thing mentioned by a contractor is that he installs very small strip heaters because they are expensive to operate and the heat pump capacity will always catch up, it just might not catch up quite as fast w/o the expensive strip heaters. In fact he says he turns his off in his own home and just deals w/ the occaisional couple degree temp drop. Any thoughts on electric backup heaters? (we don't have gas or any other source)


    I think back up heat is a wise move. You never know about mother nature or unexpected failures. How you accomplish that is your decision be it heat strips or wood burner.

  3. #3
    Join Date
    May 2005
    Posts
    159
    Where are you located? Do you have any idea what kind of soil is underneath your area? The contractor that said antifreeze ruins efficiency is wrong. It barely effects the heat transfer rate, and barely raises viscosity if you use methanol. Also, contrary to what the worry-worms would have you believe, methanol is very safe. It's actually really hard to ignite. I work with engineers that have run methanol engines on dynos where they sprung a leak in the fuel lines. The methanol was spraying directly on a cherry red exhaust manifold and they didn't get any fire.

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