Standing Column vs. Closed Loop System

Discussion in 'Geothermal Loops' started by CT Geo, Apr 6, 2009.

  1. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    Just a footnote about the HVAC guys "added costs" for closed loop.... a couple of flo raters, gauge glass, sediment filter, and 2 solenoids cost about the same as a flo center. Labor is similar as well to install one or the other.
    I'm more distressed about your continued ignorance of load and design % covered by the equipment.....7 tons seems a lot for 1700sf if I'm remembering correctly......
  2. CT Geo

    CT Geo New Member

    The house is 3,500 sf, not 1,700. I am trying to clear up my "ignorance" regarding the design - I will be discussing the project today with the HVAC contractor and will be efforting to obtain the Manual J calcs for the house.

    I, too, was skeptical of the HVAC contractor's claim that there would be additional costs associated with the closed loop system. In addition to what you point out above, there will no longer be a need for a CuproNickel heat exchanger, which I would think would result in an additional savings.

    My ignorance, in large part, is related to the fact that I am a home owner and I work in a field that is completely unrelated to any of this. This forum has been extremely helpful. I appreciate all of the input that I have received.
  3. gabby

    gabby Member Industry Professional Forum Leader

    The great thing about ignorance is that it is curable with knowledge.
    We all have a comfort zone staying within our “endogenous” arena, but real world experiences seem to drag us into endeavors that are “exogenous”, thus expanding our knowledge base.

    Endogenous- within a system, such as tissue and organs inside the human body
    Exogenous- outside a system, such as the value of the dollar exerting pressure on the supply/demand of oil.

    Today your knowledge base increased by two vocabulary words as did mine.

    Things to know:
    Manual J values for the heat and cooling loads
    Total CFMs needed for the load, as well as a per room basis.
    Loop length and size for “whatever” system is to be installed along with the pump size for the system.

    The rest of the Manual alphabet fine tunes the size of ductwork per run, and the placement to deliver the right CFMs per room. If the system is divided into multiple units, then you need these calculations for each unit too. The accessories like plenum temperature, temperature probes, gauges for pressure or flow rate are all bells and whistles to monitor performance or in troubleshooting the system.

    If you pay an hourly rate for service, these become important. The time it takes to add them later could be costly for a minor issue repair. It’s much easier to add the basics at installation, than later.
  4. CT Geo

    CT Geo New Member

    Ok, now I have some information. The HVAC contractor just faxed over their calculations.

    Total Heating Required: 62,096 Btuh
    Total Sensible Gain: 27,178 Btuh
    Total Latent Gain: 2,741 Btuh
    Total Cooling Required Including Ventilation Air: 29,919 Btuh

    There is a lot of other information in the fax that I received (they used the Elite Software package, fwiw). If there is anything else that is germane to this discussion, please let me know and I will see what I can find.
  5. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    Are those numbers for the existing 1700 SF house or do they include the planned additions you mentioned earlier?

    This thread has gone on so long I've become confused - perhaps a brief recap of house and present situation would be in order.
  6. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    7 tons for a 62K load don't jive.
    Like engineer the thread is long enough that much of the info is lost to me.
    I hope you took the word ignorance to mean a non-judgemental lack of knowledge about something vs the more insulting possibilities.
    I remain ignorant to many things including what my wife is thinking.....
  7. CT Geo

    CT Geo New Member

    Here is the recap:

    My wife and I purchased a 1700 sq. ft. house, with the intention of immediately adding onto it. The house is now 3500 sq. ft. The existing house is 2x4 construction, the addition 2x6. As part of the renovations, we are replacing the old, oil fired heating system with a geo system. Through my early research, I decided that I liked the ClimateMaster product line, and I worked through their distributor to find local installers. I received two bids from authorized installers, selected one of them, and off we went. Note: one CM installer was proposing an eight ton system (two fours), the one that I went with proposed a seven ton system. The installer that I selected proposed doing a standing column well, which we now know is probably not going to work due to the geological conditions of my site. After some price checking and negotiating, the original well driller is coming back to my house to drill and install a closed loop (unless by a stroke of luck we will be able to sustain a SCW in another bore hole).

    Please elaborate on the disconnect between the size of the units and the load. Please note that the load calcs were done prior to my decision to improve the insulation and windows throughout the home, vs. just in the new section as originally planned. My hope is that this will allow the entire home to hold its heat better than originally planned.

    No offense taken on the ignorant comment - I took it as you meant it.
  8. gabby

    gabby Member Industry Professional Forum Leader

    Good....the comment was not made to offend but to applaud increased knowledge.

    What are the average ceiling heights for the home, the total CFMs needed? Are there rooms with lots of windows facing any direction but south?
  9. CT Geo

    CT Geo New Member

    In the "old" house, the ceiling heights are about 8 1/2' on the second floor and 7 1/4' on the first. In the "new" house, the heights are 10' or more throughout. Total CFM per the HVAC contractor is 1243. There are windows on all sides, with only two facing west. The largest number face north. All windows are low-e, argon filled.
  10. jrh

    jrh Member

    Are your units already installed? 7 tons for a 62k load is a bit oversized to begin with,If you made other improvements, your heat load has probably dropped, Thus making your system more oversized.

    Oversizing geo systems is not good. 1. you will spend money on your install than you need to. 2. oversized equipment will short cycle, decreasing efficiency and life of the unit. also will not properly dehumidify in cooling mode
  11. gabby

    gabby Member Industry Professional Forum Leader

    Total CFM per the HVAC contractor is 1243.

    That doesn't jive for a 3500 sqft home.
    Having higher ceiling heights for the addition will increase the load of the addition and the overall load for the home (3500 sqft).

    The Elite software spells out all of the vital numbers on a per unit and total unit basis. Page 2 should show you the sq.ft/ton of CFM needed,as well as the Total heat required in Btuh and tons, along with the total cooling in Btuh and tons.

    The load preview report will tell you how many systems and the net ton and recommended tons for each system if multiple systems. The rest of the report is done on a room by room basis, important for duct sizing.
  12. CT Geo

    CT Geo New Member

    The units are not installed. I posed your question to the HVAC installer. He said that we are using two stage units - Tranquility 27's. The first stage on the three ton is 22k Btuh, the second stage is 29k Btuh. The four ton has a first stage of 31k Btuh, 37.5k Btuh on the second. He has designed the system to use the first stage for the bulk load (I think he said 90%, but that math seems to be a little off).
  13. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    I hope the system has NOT been specified to provide 90 % of design day load at low stage. That would result in a radically oversized system
  14. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    what city are you in?
  15. CT Geo

    CT Geo New Member

    Maybe it wasn't 90% of the load...

    Outside of Hartford, CT. Why?
  16. gabby

    gabby Member Industry Professional Forum Leader

    Location determines hot climate or cold climate priority. In your case, heat is your major concern, thus A/C may be over-sized to meet the heat load.
    There are others on this site from Conn., thus a size comparison of similar homes versus loads is more realistic than a home in Dallas. Even though rules of thumb are ballpark and skewed by the specifics of the build, questions should arise if similar structures with similar manual J's have exaggerated differences.
  17. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    >>>>goes off to look up hartford and compaire it to waterford.
  18. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    Waterford and Hartford CT should have similar design weather - they are both inland, near same elevation, and close together. Masochists can commute between them on eternally-under-construction I-84.
  19. CT Geo

    CT Geo New Member

    The driller returned yesterday to begin drilling for the closed loop. As I had requested, he attempted to drill the second bore hole first. This time, he hit plenty of good rock, but no water. I am not sure why the subsurface conditions vary so much from hole to hole, but I think that we are now locked into doing the closed loop. First hole was done at the end of the day, 350 feet. Two more to go, all of equal depth, giving me a total of 1050 feet. They say they should be done with the drilling, by the end of the day on Wednesday, at which point they will put the pipes in, grout, interconnect, trench to the house, and bring the lines inside.
  20. demurf

    demurf New Member

    I currently have a scw that has been in use for 26 years with relativly no maintenance. I had to replace the waterpump aprox. 10 years ago but the well is now backing up on a constant basis. I have been told that the cost for a new return well is approx $5K and I am looking at doing a complete new system with a closed loop. Is there an advantage to a 200 foot vertical loop over a 125foot horizontal loop?

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