Standing Column vs. Closed Loop System

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

  1. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    You could be a real hard a$$ and demand a closed loop system able to deliver same efficiency as the SCW without additional cost.

    Assuming that's not feasible or reasonable and you choose to meet them part way, beware being shortlooped. Perversely enough you may even need a system with slightly increased nominal tonnage to meet the load with the less-favorable entering water temperatures likely to result from the substitution of closed loop instead of SCW. System design must take all these factors into account. We write often of Manual J and D calculations, but switching loop method requires at least a cursory glance at Manual S. In other words, make sure the selected tonnage unit will still meet the house loads given different entering water temps likely to arise with the switch to closed loop.

    Let me revisit the risk of being shortlooped: Whoever bears some or all of the increased cost of the well drilling stemming from the switch from SCW to closed loop will be financially motivated (potentially to the tune of 5 figures) to provide you the least possible total bore length (shortest possible loop field). That may result in your system operating at both reduced comfort and greatly increased electricity cost. We professionals here and the geo industry in general has an interest in keeping that from occurring, because one bad job might damage prospects for hundreds of others nearby.

    If you must switch to closed loop insist on a proper and realistic loop field design that meets your loads at high efficiency.
  2. CT Geo

    CT Geo New Member

    Here is an update on what is going on. Apparently, the soil conditions are not conducive to a SCW. The driller went down about 80 feet. They were trying to make an eight inch bore hole. They were unable to hit ledge - and the hole kept collapsing on itself. According to the owner of the drilling company, they would hit a layer of "good" rock, followed by fractured rock. From his experience, and given what they experienced in the first 80 feet, we will be unable to support a SCW on this site. The switch to a closed loop system will allow them to switch to a six inch bore hole.

    I certainly do want to make sure that the closed loop is designed to meet the needs of my house. I have a meeting on Tuesday morning with the well driller and HVAC contractor. I am going to have a total of seven tons (one three ton, one four ton unit). The house is one half new construction, one half refurbished, with the entire house being Energy Star rated (insulation, windows, etc. to qualify). From what I know now, we are probably going to have three bore holes, each about 350-375 feet deep. I'll know more after Tuesday morning.

    From a negotiating perspective, I am trying to figure out how to play things. The HVAC contractor is hinting that this is not their problem (even though they were the real advocate for going SCW over the closed loop) and that this is a situation between me and the driller. The well driller seems to be a decent guy, but I don't see him drilling a more complex loop design for the price of the original SCW. An independent voice (the Climate Master distributor) has spoken with the well driller on my behalf to confirm we do need to switch to a vertical closed loop. He has offered to participate in Tuesday's meeting by conference call. Any advice prior to then will be appreciated. If there is additional information that I can provide, please ask.
    Amper1 likes this.
  3. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    Do you have a contract with the well driller, heating guy or both?
    If only with the heating guy then it's his problem.
    I don't know how invested the heat guy is into the project (ductwork already done etc.) but depending on contract verbage, you may be a square 1, and free to walk away/re-shop. Certainly you can expect to share in the upgrade expense, but I would suggest to contractor at this point that total price should not exceed your lowest bid. I'm also curious as to how big a surprise this should be, I'd be curious if other local drillers had hit similar geology and if this was predictable.
    Anticipated well/ton sounds about right for my area, what did other closed loop guys suggest was appropriate depth.
    I've been lucky and not run into a problem around here (course most of my digs are horizontal), though my instructor hit a cobble vein once while drilling that apparantly was nearly a deal breaker. I think my contracts are about to get an "unforseen geology clause." Most contracts have safety valves, yours may be the same.
  4. CT Geo

    CT Geo New Member

    The heat guy is pretty invested. Ductwork is done in the second floor. Additionally, they have plumbing and electrical arms of their company that are doing work in the rest of the house - this is part of a large renovation and all the rough plumbing and electrical is done. I am not sure what you mean by your last statement - that the total price should not exceed your lowest bid.

    I fully expect that I will have some financial pain to deal with this situation - I just think that this should be shared by all parties involved, rather than just me. If I am wrong, please let me know.
  5. jrh

    jrh Member

    If you are contracting this job, I dont see why your heating guy should lose any $$. You said he supported a SCW,but did he insist on it?, would his price have changed if you had gone closed loop? Now if he was contracting the entire job,and stood to make some $$ off of the driller, It would be a different story. I dont know if you have clarified which is the case, but I think it is important in deciding who should be spliting the difference.

    On another note the #'s on your closed loops are what we use in the lower hudson valley,NY ,when we are grouting to 1.2 conductivity and FYI it costs me $18900. for 1050ft of vertical loops drilled, looped, grouted and brought into the house. This does not include casing, if you need 100ft per borehole add an extra $4500.
  6. CT Geo

    CT Geo New Member

    Even though there is a separate contract with the well driller, the HVAC contractor brought him into the equation. The HVAC insisted that a SCW was the way to go (all other HVAC contractors that I discussed this project with said they would go with a closed loop), and this driller (that the HVAC solicited a bid from) was the only one that would do a SCW. Part of me says that this is a cost that I will need to end up covering on my own, another part says that this is a situation that I could have avoided (or at least mitigated by negotiating with multiple drillers) had the HVAC not insisted on a SCW.
  7. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    Part of me says that this is a cost that I will need to end up covering on my own, another part says that this is a situation that I could have avoided (or at least mitigated by negotiating with multiple drillers) had the HVAC not insisted on a SCW.

    There is a larger dynamic here that I don't know has been explained to us. You have a guy that's doing all the heating plumbing and electrical....I think part of the decision to use him was likely price. Why would that matter? makes us ignore warning signs i.e. every other contractor in the area said closed loop.....
    That the geo guy recommended the driller makes him in part responsible for driller. Every job I sell has contingency money in it. Maybe only a few hundred but you'd take it. When folks ask me to sharpen my pencil I explain that I can but it may interfere with my ability to take the best care of them.
    You shopped loops so you know who the least expensive in town is. Since you have a driller with an investment in the project and an HVAC guy with egg on his face I personnaly would expect to pay no more and perhaps less than other low bidders. Further I would not proceed without checking references on closed loop units done by this contractor and driller. I also want to know what % of the load is covered by equip with closed loop (you could go from good to marginal).
    Good open loop guys are not necessarily good closed loop guys.
    As I said before you don't sound like someone who wants something for nothing and that attitude goes furthest with me. I am more likely to give something to someone who expects to pay for it (they're the ones that will brag about me).
  8. stevecaz

    stevecaz Member

    Oh I am shaking my head at all this as a geologist.

    For one only an idiot would bring a drill rig out to a property for a specific purpose (SCW) and not have a reasonable expectation of what will happen. A little research ahead of time would have found depth to water, depth to bedrock, and bedrock type. With this the decision to drill or not could have been made. The only unpredictable problem then is finding a decent water bearing fracture, not have too many.

    You said "They were unable to hit ledge - and the hole kept collapsing on itself. According to the owner of the drilling company, they would hit a layer of "good" rock, followed by fractured rock. From his experience, and given what they experienced in the first 80 feet, we will be unable to support a SCW on this site."

    First, they should have known the approx. bedrock depth at your property. Easiest way is to find info from another well in the area (potable, irrigation, environmental monitoring, etc.). Second, casing is driven in the overburden while drilling to prevent cave-in, and to maintain a seal once bedrock is hit. You also say they were unable to hit bedrock (please don't use the word "ledge"), yet then say they hit layers of good and fractured rock - so did they get to bedrock or not? Was the cave-in from the overburden soil or from actually highly fractured bedrock like shale. And what is your bedrock? A quick look at the geologic map of CT will tell you that. If you are in limestone or shale or numerous other types, then instantly you know if the SCW isn't a good candidate.

    Even if a well was successfully installed, was there any hint that groundwater from that bedrock type in other areas will meet the quality criteria? Cupro-nickel exchangers have some higher limits, but there are limits. You could have drilled the well, and then found out the water was no good.
  9. CT Geo

    CT Geo New Member

    Let me explain a little bit. My wife and I purchased a home that was 1,700 sq. ft. on a nice lot in a neighborhood of larger homes. We did this with the intention of adding onto the size of the house to end up with one that is in the 3,500 sq. ft. range (as most of the others in the neighborhood are). From the beginning, I knew that I wanted to go with Geothermal. I interviewed several qualified installers. During my research, I determined that I wanted Climate Master equipment, and I used CM to identify local installers. One of them was the company that I ended up selecting. After I made this selection, they indicated that they had both plumbing and electrical expertise in house, and that there would be some economies of scale in using them for the entire job. I gave this information to my builder (who knew from the beginning that I was making the HVAC selection on my own), with the instructions that he should compare the HVAC's electrical and plumbing prices with those of independent plumbers and electricians that he would normally use. I told him that it would be his decision in the end who to use for the plumbing and electrical. After evaluating all of this, he determined that the HVAC contractor was the right one to do everything (HVAC, plumbing, electrical). I chose them to do the HVAC well before I knew they would be interested in (or capability to do) the plumbing and electrical.

    I had my meeting with the driller, HVAC contractor and my builder this morning. There is a little over 50% increase in the driller's cost to me to switch from a SCW to vertical closed loop. The HVAC contractor says that there is approximately $2,700 in additional cost to him (for pumps, other misc. equipment) that he will be eating for this job. While I am frustrated by the switch in well design (and the associated increase in install cost), I am still comfortable that I am working with a quality team.

    I dug out the bid from the other Climate Master installer in my area to compare, and my installer is still (including this additional drilling cost) significantly less than the other installer.
  10. CT Geo

    CT Geo New Member


    Your suspicions have prompted me to think a great deal about this. I asked the well driller yesterday how I could know if his 50% increase was reasonable. He invited me to get another quote, which I am now in the process of doing. Over the phone, the new well driller that I am talking to thinks that a 50% increase seems high, but he will get a copy of the well design, put pen to paper and get me a rough quote within the next few days. For what it is worth, I also checked with my builder and the well driller is a sub-contractor of the HVAC - we do not have a direct contract with him. Given these two facts, if the second well driller (who comes highly recommended) ends up with a more favorable quote, what do I do? The first well driller certainly feels that he is owed something. He has said on more than one occasion through this process that he lost $7,000 in attempting to drill the SCW - he may want me to make him whole on that. I have mixed feelings on what he is owed, and my frustration will certainly increase if this second quote comes in at a significantly lower cost.
  11. While SC GT looks very attractive, and certainly works in many areas, you have to be prepared for the additional attention that they may require. In TN, our groundwater quality practically prevents SCGT systems, but I've heard of a few that have run for 20+ years with no maintenance in our area. I've heard that they work very well in the northeast (granite formations with good water quality). We only propose closed loops at our company, but I'll concede that standing columns are appealing due to the reduced drilling depths. From a contractor's perspective, it's much easier to bid a closed loop and not have any change orders. On an open loop or SC well, the final price can vary depending on the static water level, as can the anticipated pumping costs over the life of the system.
  12. CT Geo

    CT Geo New Member

    Here is the update on the status of my install.

    After negotiating with two drillers (the original and another), I was able to get, what I think, was a fair price for the new (Closed loop) design. I ended up going with the original installer. The new installer had come in with some good pricing, and the original came down somewhat from his initial 50% increase. At the end of the negotiation, I felt most comfortable with him in that he had already spent two days drilling on my lot, so he was most familiar with my specific site conditions. Also, the specter of a potential charge for the two "lost" days and/or potential litigation were factors in my decision. Both he and I are upset with the HVAC installer for setting the (now obviously) unrealistic expectation that a SCW was a sure thing for my site. The HVAC installer claims that they had given me a cost for doing a closed loop system in the event that the site did not support a SCW. I never saw this from them (although I did see a closed loop cost from other HVAC contractors). The well driller has indicated that if they did provide a closed loop design price, "they must have pulled it out of their asses" (his exact words) because he never provided it to them.

    After all of this, the end result is that the well driller's rig will be at my house tomorrow, and the wells should be installed by the end of the week. I did get the well driller to agree to drill one of the virgin wells first (rather than the one that he worked on last month) in the event that there are conditions more favorable to a SCW in that location.

    Updates to follow...
  13. jrh

    jrh Member

    I am sure you are aware that all closed loops are not created equal. Do you care to share your details?Loop length, diameter, pump selection,type of antifreeze,grout,What load is that your sizing for. sizing for All these things really matter,better to get feedback now than after drilling and backfilling.
  14. CT Geo

    CT Geo New Member

    Here are the details that I have. The system will be a total of 7 tons (one 3 ton, one 4 ton), with forced air. There will be three wells, each 350 feet deep. Each well will have 80 feet of six inch casing (a lot of casing, but this is a result of what the well driller now knows about the site after spending two days drilling). Each bore will have 1 1/4" of geo-loop and will be grouted with enhanced bentonite. I do not have the type of antifreeze or pump selection - I believe that the HVAC contractor will be selecting these. The HVAC contractor did tell me that the pumps would be in a dual housing (two pumps) - one as the primary, one backup. Let me know if there are other details that I should be getting, and I will report back.
  15. Bergy

    Bergy Member Industry Professional Forum Leader

    CT Geo,

    How can you have seven ton loop field support two four ton units? I don't understand the 1 1/4" pipe. While I'm no loop expert, we have no vertical loops using more than 3/4" pipe for 700' of pipe. Also, 2,100' of pipe for eight tons seems a bit shy. Our loops, in east Iowa, would consist of eight 300' bores, using 3/4" pipe, for an eight ton system.


    EDIT...Sorry, I made a mistake on the loop lengths. We use 150' bores with 300' of pipe per ton.
  16. gabby

    gabby Member Industry Professional Forum Leader

    I too don't understand. Houston Texas requires seven 300' wells or 4200' of 1"loop for 5 tons...minimum.
    Some Northern areas require 150'-200' wells of 3/4 or 1" HDPE pipe or 300'-400' per well/ton. Three tons would be 900'-1200' of pipe for a 3 ton system, not a 7 ton system. :?: :?:
  17. CT Geo

    CT Geo New Member

    Well, looks like I have some more work to do. The loop design was prepared by a professional. Both well installers quoted on the same design. I do not have the specs, but I have been assured that the calculations are correct. I will contact the loop designer to confirm that it is adequate for my system (note that I made a typo and it is a seven ton system, one three ton, one four ton unit). Might the fact that my system is sized for heating, not cooling factor into the equation? Could the fact that the pipe is larger (1 1/4" vs. 3/4 to 1") than you both are discussing account for the smaller wells?
  18. jrh

    jrh Member

    1050 ft of vertical bore for 7 tons matches what we would design for if the driller is grouting to a 1.2 conductivity aka 8to1 sand to grout mix, If they are using a .4 mix we want to see 200 ft/ton or 1400ft for a 7 ton system. We also use 1.25 pipe often, mostly in our 450ft holes. It is a long way from Iowa to Houston to the Northeast.

    What was result of your heat loss/gain calcs?
  19. CT Geo

    CT Geo New Member

    I believe that they are using 1.2 conductivity grout.

    I do not have the heat loss/gain calcs. The house will be Energy Star rated, with Above Grade, High Performance Insulation (R21 in the walls, R38 or better in the ceilings).
  20. Looby

    Looby Member Forum Leader

    Pipe diameter should have essentially no effect on the total length of
    in-ground pipe required to meet your load requirements (BTU/hr).
    Heat transfer depends on the ratio of pipe diameter to wall thickness,
    and for SDR-11 geo pipe, the ratio is constant (i.e., 11:1). Therefore,
    heat transfer across the pipe wall is nearly independent of diameter.

    For a given flow rate, large diameter pipe has lower pumping losses
    (good), but also lower Reynolds number and less turbulence (bad).

    The trick to loop field design is finding an acceptable combination of
    pipe diameter and configuration (i.e., number of parallel branches) to:

    a) satisfy the HP manufacturer's GPM specs

    b) insure adequate turbulence in each branch

    c) minimize pumping costs

    The total length of in-ground pipe is pretty much dictated by your load
    requirements (BTU/hr) and local soil conditions (conductivity, diffusivity).

    Engineering is just a bucket of trade-offs.

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