Discussion in 'General Discussions' started by Bike Whisperer, Aug 1, 2008.

  1. Bike Whisperer

    Bike Whisperer New Member

    Hello everyone,

    New to the board, and the industry. I'm looking software suggestions for heat load and loop design. What have you found the most reliable? I have little luck scowering the internet. I have used GS2000.....and found it to be very finicky, as well as Ground Loop Design (the demo).

    Any suggestions?
  2. Geothermal Software

    This seems to be a pretty big question in the industry right now. I've been asked by contractors, engineers, and architects which software they should be using.

    I've used Gaia's GLD program (the full version) and was pretty satisfied with it although it had a few quirks where the output came out obviously incorrect. We are currently testing the ECA module from EliteSoft. I had a number of issues with it, including the inability to adjust for different grout types. It assumed all grout was the same conductivity as the formation.

    I know of a number of programs that calculate a single bore heat exchanger, does anyone know of one that will layout a non-generic loop field? Specifically, I was looking for one that could properly size the headers on a 300-500 bore design similar to the way AutoCAD can size ductwork (layout the bores and the order of connection and it does the rest).

    For building loads we've used both WrightSoft's and EliteSoft's (CHVAC and RHVAC) programs. Both were fairly solid programs.
  3. Bike Whisperer

    Bike Whisperer New Member

    My problem is I don't know when the numbers are obviously incorrect as I am new to this. And massive differences between programs is adding to the confusion so I can't trust any of my results. An example is for a 75000 btu house load, GS2000 says I need over 3000 feet of borehole, and GLD says I need 500. Similar differences in results for trenching as well.

    I am only using the demo, so perhaps GLD is giving wrong results? I doubt that, just trying to understand the differences. Hard to cough up $800 for a program that you are not sure of.

    Mutchgeothermal, would you be willing to run some results so I can know what is right and wrong?
  4. Geothermal Software

    Yes, I would say there is quite a difference in results. Both answers seem to be off on opposite extremes. If you send all of the data I can spot check, although there may be a delay as I don't have access to GLD at the moment since that computer is under repairs.

    It is usually best to have an idea of what the answer should be prior to running the calculations. We use the online contractor plan exchanges which gives us access to all of the geothermal projects in the region. That gives us points of comparison with our own work as well as an idea of the amount of activity in the area.
  5. Bike Whisperer

    Bike Whisperer New Member

    Where is this online contractor plan exchange? That would be a great tool.

    As for the information on the installation, the heat load is 75000 btu. The suggested pump us an Econar gv2000 forced air model GV670. 32 degree ewt, 20% methanol (although GLD is max 13.6% and my calculations have ben using that value). It is on a 7 acre lot so horizontal was planned, ground is damp clay at 10', located in Saskatoon, Saskatchewan.

    I'm eager to see what you come up with.

    Using those numbers on GLD, with a 10' deep 24" wide trench with one loop at the bottom of 1" sdr11, I get 534 feet of trench (1069 feet of pipe)
  6. Online Plan Exchanges

    An example of an online plan exchange for that area is Regina Construction Association at Regina Construction Association. Click the "Members Only" area and you will see the link for the online plan room. The vast majority of sites require membership fees, but some will offer trial passes. My project are in the US so we use a different set of sites. Most exchanges are regional and distribute in a digital format.

    When you spoke of a bore, I assumed this was a vertical loop which has much shorter ft/ton lengths than horizontal loops. I haven't run the calculations yet, but the 3000 ft number is now plausible. The 500 ft number from the other program may have been "per circuit". I'll run the program as soon as I can to verify.
  7. Richard Gordon

    Richard Gordon New Member

    Modeling Response

    I have had consistent perfromance using a combination of eQuest and PowerDOE, both using DOE 2.2 as an engine, for identifying both peak loads and annual energy use for GCHP systems. I then use data from the output with GchpCalc to determine the bore length. I have had consistent performance in the sizing of the GHEX using this process for over 10 years.

    It is my opinion that GCHP system designs should be based on total energy transfer, both winter and summer. This is the basis for correctly sized systems. The results form the modeling provide for thermal time lag which is not available in simplified programs, particularly those that are spreadsheet based. The predicted loads are significantly less than load analysis programs predict. Typically, the sizing using this process will be 10-25% less than those required for conventional systems. Rember, over sizing the GCHP adds substantially to the first cost and results in reduced perfromance when dehumidifcation is required.

    As an example, I completed and moved into a new 3,500 gsf house on January first of this year. I installed a 3-ton ClimateMaster Tranquility 27 GCHP system with a desuperheater for generating domestic hot water with duct zoning for the first and second floors. This house is tightly constructed and has R-49 attic insulation, R-23 wall insulation and windows with a U-value of 0.28. According to the analysis performed as indicated above, three 175-foot GHEX were required. Ceiling fans were installed in 5 major rooms to faclitate air destratification. So far, the loads are right on what was modeled. I maintained the indoor temperature at a constant 68F during the heating season and a constant 72F during the cooling season.

    One thing that I have learned is that seeking short cuts on the analysis are not worth the effort.

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