Directional or trench

Discussion in 'Quotes and Proposals' started by v6turboman, Apr 14, 2013.

  1. v6turboman

    v6turboman New Member

    I'm getting ready to install a geothermal in a preexisting two story walkout basement. I have gotten some quotes and they seem to vary quite significantly in price range as well as product. Two of the quotes
    have caught my attention so far with one being a directional loop system and the other a trench.
    I live in the mist of some very tall oaks and maples, roughly 60 to 80 footers and densely populated hilly
    terrain. Also the soil is very sandy, at least for the first several feet.

    One contractor claims that the directional loop of course is the way to go because of the tree roots
    and sandy soil condition. They claim to be able to get down to just the right soil for the 5 or 6 loops
    needed to best accommodate my situation.

    The other wants to dig a trench 6' deep 3' wide with 6 pipes, he claims the tree roots grow around the
    pipe (3/4" Polyethylene SDR-11) and therefore do not effect the loops which may or not be true. It's mostly the soil conditions I am worried about. I am also a Michigander with a frost line of 42". So where in the written quoit it reads "average loop depth for 5'. I understand there are safety concerns at 6', but at 5' one of the loops would be above the frost line. They claim to have done many trenches without failure.
    Is going directional worth the extra 3 to 4 grand?

    Your two cent is greatly appreciated.
  2. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    I am a Michigander myself. We happen to use slinkies at 6'ish but a company in Haslett has done hundreds of miles (probably) of 6 pipe. Both work fine as long as there is enough of them. There is no "best" loop.
    Roots in general avoid loops that are colder than surrounding soil in winter and warmer in summer.
    Directional bore has the advantage of less landscape repair but generally costs more.
    Feel free to call with questions.
    Last edited: Apr 14, 2013
  3. v6turboman

    v6turboman New Member

    Not to worried about landscape repair, but what about the sand, and is 5' not sufficient for a trench with a Mi frost line?
  4. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader


    I am not a digger. I can run a machine, but not fast enough to get paid to do so.

    I have found if one stays about a foot below the level required for a frost free footer the loops will work. How much pipe to bury is a design issue.

    Design is the key, not rules of thumb, even though I still use both of my thumbs.

    I have learned to like slinkies when I have limited space, thanks to Palace Geothermal.

    I have learned to dig in sand in the wet and with a mini hoe with an 11 foot depth reach. One needs to be repaired and fast. A tree lives on roots that are in the top few inches of soil about out to its drip line. The big roots deep just keep the plant up-right.

    I have trenched loops in the woods in Delaware, Ohio, four years out, and Owings MD., last summer without any loss of trees, that I have heard about. Trees have been here awhile and can take care of themselves for the most part.

    I would base my choice of systems not on cost, but on effectiveness.

    I see folks installing glass communication cable with horizontal drilling all the time. Boring a 2' hole and sticking in 1 1/2" pipe might be very good for fiber optics, but if I wanted a geo pipe installed like that, I think I would like the hole grouted in. If air was a great heat conductor we would not be doing geo. We would still be using air source heat pumps.

  5. v6turboman

    v6turboman New Member

    Any advise as to what questions to ask about the geo installers about the loops, what types of test should they be performing on the loops to make sure the design will complement application? Or do most of the contractors just wing it from
  6. Calladrilling

    Calladrilling Member Industry Professional Forum Leader

    I would ask a few questions before making your final decision.
    Is the horizontal bore done with a grouted in loop at completion, or is it left to collapse (avoid this option if left to collapse).
    What is the depth of the bore, what is the soil they are going to be installed in, and how did they come u with length/numbers of bores needed?

    if the answers you recieve are not satisfactory to you, then go with the trench quote.
  7. v6turboman

    v6turboman New Member

    Dan the horizontal bore you are referring to, I am assuming is the directional bore, is this correct?
  8. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    If you have the space and do not mind the restoration of the yard later. I would go trench based on economics. Typically a trench requires more pipe in the ground than a " vortizontal ", but if it is cheaper to install more pipe than drill, I would trench.
  9. Calladrilling

    Calladrilling Member Industry Professional Forum Leader

    My OPINION in your situation would be trenches, if your limited on space then go vertical bores. I believe directional bores have their own advantages too ( to go under a pool, larger garden, or garage without disturbance) but it's not my first choice.
  10. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    First off that's average depth so for a 6 pipe trench generally you would have pipe at 6' and some at no less than 4' thus an average depth of 5'.....and yes it's sufficient in with MI frost line. Frankly the soil will be frozen around the loops anyway at the end of a heating season.

    The loops don't care if there's sand, but if it's dry it will take more loop than if it's damp sand.

    IMHO you are worried about the wrong thing here. You should worry about contractors references. Get a good contractor and the loops will take care of themselves.
    Last edited: Apr 15, 2013
  11. Bergy

    Bergy Member Industry Professional Forum Leader

    Most of our retro loops are with directional boring. Using DB allows us to cut a 2 X 2 hole in the slab, where we want the loops to be, and the looper can punch in the headers. Makes for a very neat install.

  12. v6turboman

    v6turboman New Member

    AMI is it correct to say that the loop freezes at the end of the session with all loops, DB, slinky, trench, & vertical
  13. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    No. It is correct to say that we design loops to deliver 30ish to 90ish degrees F of entering water temperature (EWT). If your EWT is down to 30F then the surrounding earth will likely be frozen (or get there soon).
    Here is my apprehension for you.
    You are worried about your loops and it appears only your loops.
    Generally with shoppers we try to find out what their Manual J heat loss is and see what size heat pump has been recommended. It tells us a lot about your installer if you know what I'm talking about and if the design is plausible.
    So far the only thing we know about the 2 installers you like is- one is trying to get you to spend extra on boring. If the reasons you listed for boring were given (and not just your take on why they were offered) then I would characterize that installer as disingenuous.

    However if he said that DB would work better because of the nature of soil so you didn't have to tear up as much of the lawn, that's different.

    One disingenuous implication people use is "more efficient". For groundloops here in MI (and most places) "more efficient" means less of them to achieve the same result. In that context vertical is most efficient and horizontal least (setting pond loops aside for now) but since they are all designed to achieve the 30-90F design parameters none will save you significant $$$ on operating cost, but they can cost you a lot of bucks on the installation side.

    Where are you located?
  14. v6turboman

    v6turboman New Member

    Manual J's were perform with both Quotes with similar results.

    One at 77,181 Btu's/hr recommending a 5 ton hydron revolution vertical, with a vertical loop attached.
    And the 2nd contractor coming in at 75,613 Btu's/hr, 5 ton series 7 WF, with a directional loop.

    The loop is just one of my concerns
    The Hydron man claim the Aux strip will come on at about 2 degree's F..
    Where as the Water Furnace guy say's I should expect the strip heat to come on between 12 & 7 degree's F.
    Not sure which one to take at face value?
  15. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    Depending on where in MI I would lean towards 5 tons.
  16. v6turboman

    v6turboman New Member

    Just north of Grand Rapids about 15mi's, both are a 5 ton units, but what at the strip heat claims?
    Last edited: Apr 15, 2013
  17. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    My understanding is the WF should have a lower balance point. I'd have to see their manual J's to see why they are what they are but likely one of them is "padding the load" (meaning picking a lower min design temp).
  18. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    You get a good amount more value with a 7-series, due to its variable speed compressor.

    It depends on with what design temperatures the Manual J was conducted. At the end of the day manual Js are still an estimate. There is not much difference in peak performance between 2 different 5 ton units, the Hydron is optimized for Winter and has a bit more refrigerant in it. Great features like microchannel heat exchanger, very well made, we put a lot of them in. WF 7 series shines with new variable speed technology.
    I find the WF significantly more quiet in case that matters.
  19. v6turboman

    v6turboman New Member

    I see what you mean one (WF) used 72F as the winter temp. and the other (Hydron) used 70F
    and yes quiet is big factor in my situation.
  20. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    Yet to find a customer who is not totally thrilled with the WF variable speed. I am putting a WEL on one tomorrow, will report back.We are selling both. Both will make you happy. As always, the key is the guys who puts it in!

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