Discussion in 'General Discussions' started by easter, May 23, 2011.

  1. easter

    easter New Member

    I am starting changeover soon. it will be diy because contractor price was more than i could afford @ approx. $15000 for 3 -500ft loops installed. i live on the water where a river meets the ocean, approx.6-8 ft above high water level. would it be wise to dig deep enough to allow water into trenchs? water is ice-covered 5-6weeks a year.
    if it is reasonable,instead of three trenchs should i go with one wide trench with out pipes on the bottom and return two feet above and how wide should trench be?
    any input would be appreciated.
  2. zach

    zach Member Forum Leader


    You are asking for design information over the internet. TIme, effort, experience, and knowledge of local soil conditions all go into a proper design.

  3. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    What are you trying to accomplish? What is the size of the system, where are you located? Was the proposed system vertical or horizontal. was it 500 length for trenches or for the boreholes? There are too many things that can go wrong with a loop. You should get professional help from someone who can look at the jobsite and design the loopfield for you. You mention that you cannot afford to pay a contractor, then you should not be able to afford a design failure. Or get some more bids.
    Don't underestimate the amount of work involved.
    You need to install the loopfield, header it, pressure test it, bring it into the building (may be you can salvage some of your open system pipe), seal the walls, fill it with antifreeze (depending on your location), purge the air out, install new circulation pumps, install a flowcenter, wire all this. So what pipe were you using, what circulation pump(s), do you have the means for purging in your design, what antifreeze do you use and at what concentration, do you header inside or outside, do you know what a reverse header is, what is your ground conductivity (probably pretty good so close to the water)? An then what load does the loopfield need to support?
    I am not trying to show off here, but there is a bit more involved in an outside loopfield, and I am trying to give you a sense for it. You cannot just ask how wide the trench should be.
    We help many DYIs, we let them excavate, we show them how to make slinkies, we let them put in the trenches, but everything else we do ourself. Chances are that you would not have the equipment to do it right, and your questions suggest that you lack the experience.
    One thing you might want to consider is to take an installer course, at least it gives you some basic knowledge. Right now, you probably setting yourself up for an uphill battle resulting in a failure. All this is well meant. We are called many times where even professional companies get into trouble and ask us to bail them out. The heatpumps usually always work well and have a wide operating range, it is usually in over 90% loop design issues which make systems fail. I can only urge you not to contribute to that statistic...
    Last edited: May 24, 2011
  4. easter

    easter New Member


    Thanks for reply and concern. I will try and answer your questions as best i can with my limited knowledge. I live in Atlantic Canada and I got the quote from the company that installed the unit and the only installer in my area. The unit is a nordic 3-ton, 3-stage.
    I have had some issues but we won't go there.I just want the system working as well
    as a Nordic can.The ground is gravel and the lines will be horizontal,6ft deep and 10ft
    apart .Pipe will be hdpe sdr11 3/4' 600ft long. Unit calls for 500ft but I always like to go a little extra. Trenchs will be 2ft wide with pipe out one side and return on the other side.
    Pipes will be headered inside with pvc sleeves in concrete wall filled with expanded
    foam. I will do a reverse header.
    The flow center will be QT-FCQ1G from Geo Hydro. Anti freeze will be Methanol
    at 20% for -15*F protection. I will rent a pump for purging and non-pressurized
    flow center should take care of the rest. My brother in-law will do the wiring.
    The majn question on my mind is if I dig deep enough to have my pipe in water ,do I still
    need 10ft spacing or something closer to a pond loop.
    Thanks again.
  5. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    Probably not

    But if your soils are truly gravel, I wouldn't install any pipes in that unless they were in water.

    Not enough info. to comment further, but be careful if you're basing your installation details off of a quote. 500/ ton is about the shortest loopfield I've encountered. Loopfields = building loads not heat pump sizes.
    Last edited: May 24, 2011
  6. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    Gravel is a red flag unless you have water in the trench. It will not behave like a pond, since it is missing the stratification. At the bottom of a pond water is 39F due to its highest density at that temperature, and cooler water will raise away from the pipes, something which will not happen in trenches. If you are putting straight pipes in, they do not need to be 10ft apart, usually ice cylinders form with a radius of 1-1.5 inches. So being 4ft apart is good enough.
    500ft is very short, 600ft is the minimum/ton we go with, given your unknown soil conductivity, I would go up to 800, but for pressure drop reasons not more than that. Alternatively, you can add a 4th loop.
    Headering inside with shutoff valves on each circuit might enable you to purge the loops without a purge cart. Methanol concentration of 20% is not given you -15F protection, but rather 15F, I assume this was a typo. Make sure you have a pressure drop calculation done for the loopfield,
    Last edited: May 25, 2011
  7. easter

    easter New Member


    Thanks for replies and suggestions.The information I provided was from my own research,mostly from this site. One thing I remember from the quote was the 500ft loops and according to your thoughts that was suspect. The only other thing I remember was the price and the info is now gone from my email.The gravel I mentioned is not what would be considered pure gravel. The size is anywhere from dust to 6 inch.The dust to sand size will be put on pipe first. If not sand or clay will be brought in. Trenches would be 10ft apart with pipes in trenches being 2ft apart. Can I take from your suggestion that I could use one trench 8ft wide with pipes 4ft apart with three out at 6-8ft depth and three at 2ft above that returning. If not I will go with 3 trenches.I also realize that it will not be close to a pond loop-guess that was a bad comparison.And yes, the -15 was a typo. I enjoy working with my hands but not on this keyboard.
    Thanks again.

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