"Shallow rock" affects vertical loop's capacity to heat?

Discussion in 'Vertical and Horizontal Loops' started by Tamar, Dec 12, 2013.

  1. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    That's great
  2. Tamar

    Tamar Member Forum Leader

    I had to post this picture, since we've had about a 40* temp rise in the last 24 hours. At -6, the 2 compressors run 100% of the time and the EWT was pretty stable at 29.5. Now, just 24 hours later, one of the compressors is mostly off and you can see how quickly the EWT recovers to a higher temp.

  3. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    Thanks for this.....shows a well functioning system
  4. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    :)The physics at work!

    Lets point out here that many of your local engineers, and even your installer, said that your loop field cannot support your house heating load.
    Last edited: Feb 25, 2015
    Tamar likes this.
  5. pfer10

    pfer10 Member

    Question as I have read through Tamar's thread. You guys say 8 tons of equipment but when running on closed loop isn't that more like 6 tons of equipment since all the units seemed to be rated at 50F EWT? At least for the name badge a 5 ton unit seems to put out 4 tons on closed loop. The 3 ton seems to put out 2 ton. It seems like the equipment is always about a ton less at 32F EWT. Why don't they just rate it at 32F since closed loop seems to 95% of the installs?
  6. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader


    The ton naming is really just to talk basics. As you've touched on, it is not exactly written in stone.

    Designs around here are typically based on 30F EWT with equipment sized based on their output at these temps (for heating that is).
  7. pfer10

    pfer10 Member

    I guess I get goofed up because from the thread everyone agrees that the loops can support 6 tons of equipment but in the thread it continuously mentions 8 tons of equipment. But really on a closed loop that 8 tons is going to be more like 6 tons. It just seems like they would rate it at 32F or 30F if that is what it is going to run at most of the time.

    Also one other question. 98% of the load means if the house uses 1,000,000 kBtu per heating season the geo will cover 980,000 kBtu?

    Sorry for the questions in your thread Tamar but it has got me learning and is good reading.
    Last edited: Feb 24, 2015
    Tamar likes this.
  8. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    No. Generally x% of the load means x% of peak load. The heat loss of the structure at design temperature.

    At least when we talk about % of load.
  9. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

  10. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    Rated tonnage usually is for cooling 12,000 BTUs/ton, whereas in heating at 32f EWT the units usually put out around 9,600 BTUs/ton.
    Yes, 98% of annual load means 98 out of 100 million annually. That is different from the peak load, which is the difference on a daily our hourly basis the supplement heat has to make up. Residential units usually come in increments of 1 ton cooling capacity. It means nothing but that one should pick the unit size which serves the assumed load best.
    Just to reiterate what Chris said here before.
  11. Tamar

    Tamar Member Forum Leader

    It all makes my head spin...sometimes I think I've got it, but don't ask me to explain it to anyone else. Watching my system is fascinating, especially with all the cold weather we've been having. It's easy to see how one 3.5 ton compressor vs two 3.5 ton compressors affect the ground loop and the EWT. The next layer is factoring in what the design temp does to all the facets (mine is set to -5). And then another layer is what the source EWT is, which just amazes me how much that varies. And I know nothing about how to set the variable speed pumps to make sure everything's moving through the system at the optimum speed. Gives me so much respect for the experts who know how to make this work!!

    Palace GeoThermal likes this.
  12. pfer10

    pfer10 Member

  13. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    I guess everyone here is excited that you turned from a totally frustrated homeowner to an excited geo junkie!:)
  14. Tamar

    Tamar Member Forum Leader

    I knew I had it in me....:D . I have to say, I don't know what to do with all my spare time now that I'm done case-building and researching and coordinating schedules and such. I just watch my WEL and smile.
    Palace GeoThermal likes this.
  15. BMGEO

    BMGEO New Member

    6 wells at 200 ft. Is going to fall short of 8 tons I drill my on wells because of this very thing, well drillers short stick you on each well one 20 ft stick and call it good because you have 20,40, Ft. or more of header pit thinking that will Make up the difference, but it don't, I mostly drill in rock it seems to give off, and take in some of the highest thermal transfer in my book, but if you are trying to drill it with a mud rig you got problems, my wells are pulling between 11387 BTU'S to 12276 BTU'S at 200 ft. At 300 ft. I pull another 78k to81k of BTU'S, moving me up to about 1.66 tons - 1.73 tons per 300 ft well, but I uses beratherm gold grout, w/4 50 lb. Sacks of white sand silica, 15 gals water, not dumping pea gravel down them, 3- 300 ft wells gets over 5 tons, and at 11-12 dollars per ft. It saves home owner 100 ft of drilling cost, but I use 1" loops also so 5 300 ft. Wells sould have dont
  16. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    So you know that 6 x 200ft is falling short of 8 tons?
    Do you know Tamar's geological conductivity and diffusivity, and the pipe diameter, and grout conductivity, and pipe diameter? Do you know the minimum temperature her loop drops down to?
    I have seen loop fields supporting each ton with less then 120ft of borehole.

    Welcome to the forum, but your first post here sounds a bit more like "look how great I am", without having the necessary information to really judge what kind of load Tamar's loop field supports.
    Palace GeoThermal likes this.
  17. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader


    Hi and welcome.
    As a new member I will give you a mulligan on your blatant comments and derogatory insinuations. We have a very mature think tank of brain power here trying to educate each other as profesionals and help homeowners with problems that they have. Talking smack about a entire industry group " drillers" will not make you very popular here.

  18. BMGEO

    BMGEO New Member

    Sorry I guess after being done wrong by so many different ones, than being left to hold the bag so to speak, and trying to explain to the homeowner, why they never registered their wells, and after digging down 15 ft. And only finding gravel pea size, no grout in it kind of gets frustrating, anyways only God is good not me just trying everything I can to make things work and do 110% for my customers so they are satisfied, please forgive my tongue, I do enjoy reading the discussions
    Palace GeoThermal likes this.
  19. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    BTW, a borehole filled with pea gravel and then filled with water is not a bad conductor of heat! Ice is even better! I just consider it environmentally inappropriate to not seal the borehole from the bottom up.
    waterpirate likes this.
  20. richard kellogg

    richard kellogg New Member

    The suspense it killing me. I spent the last few hours reading all of your woes, only to get to the happy ending - without seeing how the system was resolved. It went form dispare to success, with no posts.

    How was this resolved? Did the installer fix it, settle in court and you call in someone else, or what?
    So glad to see it is now.

    It was an interesting read.

Share This Page