gregj
Basic Member
Posts:326
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| 15 Jan 2008 12:02 PM |
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I'm looking at geothermal for my residence in eastern Nebraska. I have a backhoe with a 24" bucket and 14' deep digging capability. I live on a farm, soil is considered a Sharpsburg clay and I have about 3 acres surrounding my house that I could use for loops.
I would like to save some bucks by installing the loops myself. Can any of the experts on here recomend a loop configuration for my circumstances? I'd like to keep it simple by digging 24" wide trenches to the needed depth and length.
So would a 24" wide trench be too narrow for slinky? If I go multiple pipe how many pipes would be ideal for a 24" wide trench? Do I trench a loop or a spoke - that is should I dig a trench that loops back to the house so the pipe returns by a different path or a trench that ends away from the house so the pipe returns along the same path in the same trench?
Finally, Is a deeper trench better? Should I go as deep as I can dig? |
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caja_ca
New Member
Posts:14
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| 15 Jan 2008 11:32 PM |
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not an expert...seen the slinky in books, but never applied , from what I understand slinky is for constricted areas. Figure out how many tonnes you need approx 600 ft of 3/4 per tonne . ie:Five tonnes dig 2, 300 foot trenches and one trench perpendicular to them (for your headers) lay down the tubing with ends coming into perpendicular trench dig a third trench and use that soil to fill first and second trench....continue on using dirt from new trench to fill tubed trench. Lines should be 2 feet appart, but 20 inches should be fine. trenches should be good at 3 feet apart. On a 5 tonne loop-5 trenches you will want to have a "reverse return " header system in the perpendicular trench. From the perpendicular trench you run your 2 lines to the house.
OR you could dig 8-10 feet lay a set of loops cover with 2' of dirt and lay a second set. (caution:soil compaction) , less trenches.
your loops will connect to 3/4 in tees and then to 1in to flow center. Can't explain "reverse return" (or draw it for that matter)
Not an expert.
Not a fan of the slinky---l
Not sure of depth required, or length for a tonne in Nebraska.
Not sure I'm helping
Cheers |
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gregj
Basic Member
Posts:326
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| 18 Jan 2008 06:22 PM |
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Anyone else have any info? |
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Palace Geothermal
Veteran Member
Posts:1609
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| 18 Jan 2008 07:49 PM |
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If I was doing this job, I would dig a 2 ft x 6 trench by 250'. I would lay one 500' coil of pipe down one side of the trench and back the other. Then I would take another 500' coil and staple it to the side of the trench up 2' from the bottom. This is called a four pipe trench. Deeper is better, but more dangerous. Working in the bottom of a 14' deep trench is way to scary for me.
I did see a guy once who and built a tool that he could just reach down in the trench and position the pipe. If you really wanted to go deep this would work. Just do a 2 pipe trench. If you are doing the digging then this would give you a better system.
There is no reason to do a slinky in your situation. They take a lot more pipe. 24" is not wide enough.
Dig the trenches in a fan pattern so that they all start from a pit and fan out away from the pit. This makes the heading a lot easier.
Hope this helps. Ask if you have more questions. |
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Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
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gregj
Basic Member
Posts:326
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| 21 Jan 2008 05:09 PM |
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Thanks Geodean. There's definitely no way I'm working in a 14' deep 2 ft wide trench. In fact I wouldn't go in a 6' deep trench without a trench box or whatever they call it - and with a boxed 2' wide trench I don't think I could move very well. I was planning on working from above for tubing installation and coming up with some type of tool to position the pipe. Was hoping not to go to 14' deep either, that was just my max reach.
Our max frost depth is around 3' here so if I go with the four pipe trench would the 4' depth of the upper pipes be deep enough or should I go a little deeper say 2' below frost line for upper pipe and 2' lower for the lower pipe (total trench depth of 7')?
Can the trenches follow the surface contour or do they have to be level or sloped a certain way? |
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Palace Geothermal
Veteran Member
Posts:1609
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| 21 Jan 2008 06:47 PM |
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1' below frost line will work. 2' works better. It just depends on what you can easily do. Following the contour works just fine. IF you are going to work from above, you should probably do a 2 pipe trench. As you have to get down in the trench to do a four pipe.
Let me know how it works out. |
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Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
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BarnTalker
New Member
Posts:5
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| 22 Jan 2008 02:30 PM |
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New member. New question on loops. In our market here in SW Ohio, geothermal is coming to the forefront of discussion. We have installed a few systems in new homes (we specialize in homesteads, small farms) but are encountering debate as to the potential problems with pond loops. Namely, customers and subcontractors concerned with the potential for fish kills, deoxygenation, and thermocline inversion. Most of what we see says that pond loops are the most efficient and since most of our projects include construction or rehabilitation of a farm pond, this system makes the most sense. We shoot for a minimum 2000 s.f. per ton, min. depth 10'. I can't find anything to confirm or deny these fears. Please help a newbie. |
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Palace Geothermal
Veteran Member
Posts:1609
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| 22 Jan 2008 04:16 PM |
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Hey Barn Talker welcome totthe forums ! I don't know of any published data on the size requirements for pond loops. The numbers you stated sound in line with the pond loops I have seen installed. Have you been to the Slim Jim site ? LINK |
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Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
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TechGromit
Advanced Member
Posts:634
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| 22 Jan 2008 04:30 PM |
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Posted By BarnTalker on 01/22/2008 2:30 PM
Namely, customers and subcontractors concerned with the potential for fish kills, deoxygenation, and thermocline inversion.
I'm not sure I understand the question. My understanding of Geothermal is it extracts either heat or cold from the water that passes thru the the system and the "exhaust" or "waste" coming out of the system is water that is a few degrees colder or warmer than what goes in. I don't see how water a few degrees difference in temperature around the geothermal exhaust is going to affect the fish in the pond one way of the other. The Compressor doesn't suck any oxygen out of the water that runs thru the system and far as Thermocline Inversion I don't think any system will have much of an effect of the overall temperature of a decent sized pond. I guess in theory a large enough system coupled with a small enough pond would affect the overall temp of the pond downward or upward but as the temperature drops (or goes up) the system would have to work harder and harder to continue to have an effect on the pond. I don't think any system could force the temperature into the freezing or boiling mark, but it's an interesting idea. |
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Palace Geothermal
Veteran Member
Posts:1609
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| 22 Jan 2008 05:02 PM |
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I forgot to talk about fish and other stuff. I would agree with TechGromit. It simply is not a concern as long as the pond in large enough. If the pond freezes then water on the bottom is 39°. If it hasn't frozen yet then the water on the bottom will be warmer. You do not want to aerate the pond during the winter. Summer is OK. |
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Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
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BarnTalker
New Member
Posts:5
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| 22 Jan 2008 05:14 PM |
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Thank you for your input. One of our HVAC contractors has been through training with, among others, Climate Master. He has relayed to me that all manufacturers, including Climate Master, that he has talked to toute as one of the benefits of a closed loop pond system that as the system pulls heat out of the pond it will freeze earlier and stay frozen longer (they say to tell customers that they'll have more ice skating opportunities!). And for those that are "concerned" about fish overpopulation, the excess heat dump into the pond in the summer will instigate a moderate fish kill each year. Now, this is all second-hand info and I have not been able to verify any of this, but for my customers who don't like to ice skate and want to build a healthy fish stock these potential rumors are disruptive. I agree with you that "it's an interesting idea", but the thermodynamics just don't make sense to me. In my estimation, the incredibly high heat capacity of water shouldn't let these things happen. However, I'm new to this technology and my thermodynamics classes are far behind me....but I'll keep looking nonetheless. |
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Palace Geothermal
Veteran Member
Posts:1609
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| 22 Jan 2008 05:44 PM |
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Posted By BarnTalker on 01/22/2008 5:14 PM as the system pulls heat out of the pond it will freeze earlier and stay frozen longer (they say to tell customers that they'll have more ice skating opportunities!). And for those that are "concerned" about fish overpopulation, the excess heat dump into the pond in the summer will instigate a moderate fish kill each year.
This just can't be true in every case. There are plenty of pond loops working out there. Find a couple and ask them if there fish have died. If you aerated the pond in the summer, this should take care of whatever heat the heat pumps put into the pond.
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Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
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Palace Geothermal
Veteran Member
Posts:1609
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| 22 Jan 2008 05:49 PM |
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Talk to these guys SlimJimPond loops is all they do. |
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Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
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TechGromit
Advanced Member
Posts:634
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| 22 Jan 2008 10:23 PM |
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Posted By geodean on 01/22/2008 5:02 PM
If the pond freezes then water on the bottom is 39°.
Wow that cold? The colder the water is the harder the system has to work to extract heat out of it, I would learn towards a open loop well system or better yet a closed loop system since the water is somewhere around 50 degrees F. I would imagine a system pulling in 39 degree water is a lot less efficent than one pulling in 50 degree water. |
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Palace Geothermal
Veteran Member
Posts:1609
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| 23 Jan 2008 09:59 AM |
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Posted By TechGromit on 01/22/2008 10:23 PM
I would imagine a system pulling in 39 degree water is a lot less efficent than one pulling in 50 degree water.
A heat pump with enetering water temp of 40° has a COP of 3.75, with entering temp of 50° the COP is 4.06. This is an increase in efficiency of 8%.
Sure 50° is preferable to 39°. But the cost of a pond loop is a fraction of what a verticle loop would cost. Does it make sense to spend $10,000 to $15,000 more to get a verticle system that is 8% more efficeint? Not in my book.
So pond loops are very attractive if a pond is available. |
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Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
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BarnTalker
New Member
Posts:5
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| 23 Jan 2008 10:26 AM |
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I thank everyone for their contributions. You have done well to assuage my concerns. As I said, we have installed pond loops with no evidence of them creating an ice age nor an aquatic massacre. I'm still looking for rock solid evidence, but confident to counter the arguments. |
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gregj
Basic Member
Posts:326
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| 23 Jan 2008 02:07 PM |
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Posted By TechGromit on 01/22/2008 10:23 PM
or better yet a closed loop system since the water is somewhere around 50 degrees F.
I have been curious about the actual temps of a closed loop system. Does anyone know of any published data for an actual installed residential system that shows the outgoing water temp and incoming water temp over the course of a heating or cooling season? It just seems to me that the ~50 degree ground temp that we have here in Nebraska would drop considerably around the geo pipes over the course of the winter as the heat pump continues to remove heat from the soil. I realize that the surrounding soil will add heat back but I'd like to see real numbers on how well the soil temp is maintained. |
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BarnTalker
New Member
Posts:5
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| 23 Jan 2008 05:01 PM |
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Here is an excellent design manual from McQuay with a fair amount of empirical data on loop temps, design loads, etc.
LINK
Worth a look. |
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Palace Geothermal
Veteran Member
Posts:1609
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| 23 Jan 2008 06:08 PM |
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I have a slinky loop in my yard. I have been tracking the temps for three years. The loop temp swings from 40° to 68°. No way of knowing how much of this swing is seasonal vs. heat pump. |
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Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
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gregj
Basic Member
Posts:326
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| 25 Jan 2008 02:32 PM |
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Thanks Barntalker and geodan. That link is interesting. It doesn't give any actual data other than an interesting observation that the ground temp rises some over the years with a geo system. Never thought about that before. Long term soil temp drift is probably more likely in an area where the cooling/heating seasons are unbalanced.
Geodan, your's are the first actual loop temp numbers I've seen and greatly appreciated. |
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