Loop Depth

Discussion in 'General Discussions' started by mntnvew, Jan 12, 2009.

  1. mntnvew

    mntnvew New Member

    What, if any, benefits are there to placing the loop for a horizontal loop deeper in the ground? Is the ground warmer as you get down further, I assume yes but always end up hating life when I assume without 100% confidence :)

    I live in SW Montana and we get to -40 with wind chill so if I went down, say 8-9 feet would my systems performance increase?

  2. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    yes yes yes (system here doesn't allow just one 'yes' - too few characters?)
  3. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader


    The deeper you go, the less fluctuation in ground temperature. The surface soils would be much warmer in the middle of summer than at depth for example. Remember you're generally heating and cooling.
  4. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    Deeper is better.

    I live in Salt Lake City Utah, I have sensors in my soil. The temp at -5' is 51°, the temp at -9 is 54°.

    More important than depth, is proper loop length. Getting enough pipe in the ground is most important.

    Adding depth will give you a little better efficiency, but will not make up for being short looped.

    Do you have someone to design your loop?
  5. rw1995

    rw1995 Member

    Deeper is definately better. I went 9-10' deep, as the temps are more stable and moisture levels were much higher. We had water running into the ditch thru most of the trenches.

    You will not have a great amount of excavation time to go a foot or two deeper. My excavtor dug five 110' ditches, 60' header trench and 75' trench to the house in a 10hr day. The system was tested overnight, and backfilled 3hrs the following day.

    Some underground contractors may question the depth as far as safety goes, OSHA has 5' max without protection or sloping.

    We built the slinkys and rolled them up before the dig. Make sure the excavator is 6-12" wider than your slinky coil. Once they are to the end of the ditch, unroll the slinky into the ditch and they can backfill.

    We used a fiberglass pole with hook in the end to help unroll the coil without getting into or near the ditch at all.
  6. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    Excellent advice... we use the same technique using a piece of electrical conduit with a hook rolled on each end.
  7. mntnvew

    mntnvew New Member

    No I don't. Would you be interested.
  8. bjnm

    bjnm Member

    Definitely go with the deeper installation.

    For all the techies: I was told that it doesn't really matter by my loop installer. After reading everything I believe it does matter. However, I called another loop installer in my state and they gave the same installation method as the company I use so who might be wrong.

    My installation is 3 3/4" pipes running 350 out at 5 feet deep then at the end of the 350 feet they roll the pipes over and run them back at depths of 3 feet and 4 feet with about 12 inches between them. I was told as long as it is below frost line it doesn't matter. I have issues of our unit running too long which we are assuming is too small of unit, but if that gets fixed will the depth make a difference overall? This is for an envision 3 ton, in Indiana.

    Thank you,

  9. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    it seems that some installers will tell the customer anything to get off the hook.

    Sure systems can work if they are just below the frost line. But it is an indisputable fact that going deeper gets you warmer ground temps which will make your system work better.

    Sorry for the rant:mad::mad:
  10. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader


    The code "North of the Border" is minimum 4' deep, but I'm often installing at 8' depth. Frankly I've never installed at only 4' deep except for possibly the header area and the returns to the the house.

    Design software will allow you to see the increase in trench length required as you go shallower (and vice versa).

    But, as you are heating and cooling up here, I'm going to reiterate it is a bit false to look at deeper as "warmer". It has less fluctuation. That is what allows the loop to be minimized with depth. Granted in the middle of winter, it is warmer than soils above it, but we're interested in 12 months of the year.
  11. The loop design you have described should be fine for a 3 ton system in indiana. you say the unit runs to long. How long is too long?
  12. lman

    lman New Member

    I'm in Northern Indiana and it sounds like you've got the same kind of loop I have. I have a 3 ton also, but they were only going to do a 300' trench. I convinced them to go another 50'. My EWT is down to 29 though. My system runs 24 hours if it's below 20 and no sun. It drops into first stage and runs for a while and then goes back to second stage. I noticed that I can change a dip switch so that it stays in second stage until it reaches set point. Should I change that setting.
  13. Looby

    Looby Member Forum Leader

    According to my WF installation manual, it's best to stay in second stage if
    you have a reciprocating compressor. With a scroll compressor, it's better
    to "down-stage" if/when the t-stat switches back to stage1.

  14. gabby

    gabby Member Industry Professional Forum Leader

    I asked this question before. If a designed system (vertical or horizontal closed loop) called for 5 tons of cooling loop, and you installed the equivalent of 6 tons of cooling loop for that location, what would be the downside besides the extra cost of 1 ton of pipe loop?

    I realize the head may change slightly, the pump requirements may change slightly, but if the pump specs provided the capacity of flow or were upgraded, what's the downside risk to heating or cooling?
    You definitely don't have to worry about short loops and the problems associated with that.

    It is commonplace to have a 3 ton system with a 3.5 ton condenser for a conventional system. This is for cooling only, not heating.
  15. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    There is no downside. My house is just what you described.
  16. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    I agree there

    is no down side, except materials cost.

    Nice photos palcegeo, BTW.
  17. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    Thanks .

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