Open vs. Closed Loop operating costs?

Discussion in 'Geothermal Loops' started by Guest, May 7, 2008.

  1. Guest

    Guest Guest

    In researching GSHPs I've learned that open loop systems are more efficient due to the more consistent temperatures of the well water, but I have not seen any figures on operating costs vs. closed loop. Is it more expensive to pump water from a well vs. pump coolant around a closed loop? And if so, how much more expensive is it?
  2. Guest

    Guest Guest

    The main difference in actual operating costs is in the Horse Power ratings of the pump. For open loop the horse power rating would be higher then the close loop but only marginally.

    The main difference in actual operating costs is in the Horse Power ratings of the pump. For open loop the horse power rating would be higher then the close loop but only marginally.

    The problems I have with open loop:
    · The water quality can change.
    · Possible contaminates
    · In a lot of areas the ground water is very acidic
    A vertical closed loop has very little temperature variation. It's not susceptible to contamination and the water quality is constant. If you compare most manufacture’s data the COP differences between open loop and vertical closed loop is very small.

    There can also be environmental concerns using ground water.
  3. Guest

    Guest Guest

    Thanks for the reply.

    My well pump is 1.5 hp, 11 amp and is set 305' deep.
    How does that compare to the pump needed in a closed loop system?

    My well water is acidic, but I have a neutralizer and softener with the resulting water being of very good quality.

    My thinking is why spend the $$$ to put in a closed loop if I don't have to. I am finding that contractors here favor closed loop systems, but can't give me (what I feel are) very good reasons why. Are they just looking to make more money... or are there other reasons to favor closed over open loop?
  4. Waukman

    Waukman Member

    If you can determine the quality of your water and can get a good estimate of the lifespan of the geo unit using that water that will give you a better idea of the costs. My parents have an open loop and have not had any issues for many years.
  5. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    Most closed loops run on 1/6 to 1/3 hp pumps. There is not lift required so the pumping requirements are much less.
  6. Guest

    Guest Guest

    Re: Reply to thread 'Open vs. Closed Loop operating costs?'

    Geographically I don’t know where you’re located but there are times when your unit will run for 24 hours straight.

    11 amps for 24 hours = 58.8 Kilowatt Hours @ $0.10 per KH = $5.88
    1.4 amps for 24 hours = 7.4 Kilowatt Hours @ $0.10 per KH = $0.74

    Now to be fair if you use vertical holes for your closed loop system you will have to have two pumps connected in series. If you have more then three or four bore holes you may need 3 pumps in series.

    I installed my GeoThermal two years ago. I used the trench method placing 1500 ft. of 3/4" pipe in three separate 5' deep loops. My 3 ton FHP unit requires 4 gpm. which I supply with a TACO 009 pump rated 115 VAC, 1.4 Amps at 1/8 HP and a regulating valve.
    If I had it to do all over again I would pay the extra money to have the holes drilled and I would have put my loops in vertical since ground water for geothermal use is not allowed in Indiana. The ground temperature variation at 10’ depth is +- 5 deg F and at 30’ it’s +- 1 deg F

    If you have to go 305’ to get to water then I would think it too precious a resource to be using it in a geothermal application. I personally feel that unless you can hit water at 20’, ground water should not be used for geothermal. Fresh water is too great a natural resource to be wasting it on geothermal. Even if your putting back in the ground.
    I find it hard to believe that a water softener is going to keep up with a > 4 gpm. flow rate for very long and this is what I talked about in my first reply about a consistent supply of source water. Ground water requires a continuous monitoring routine to be sure the quality remains acceptable. In a closed loop if you use distilled water and food grade antifreeze/alcohol to fill you loop then all you need to do is remove the air and pressurize to 40 psi. and your finished. You will get years of uninterrupted service from your loop and extend the life of your heat pump with very little monitoring over the years.

    Loop installation has a very steep up front cost but it’s also the heart of your system. Heat pumps can be easily replaced but the supply system can’t so it must be given the biggest priority when installing a geothermal system.

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