OP
955Lincoln
Gold Member
I'm looking at it right now but it only mentions stuff above their lines. I will talk to the power engineer who came out and designed the system.
BTW, that sure is a wide trench. :shocked:
Geothermal in power trench...Doable or Not?
- Thread starter 955Lincoln
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I'm looking at it right now but it only mentions stuff above their lines. I will talk to the power engineer who came out and designed the system.
BTW, that sure is a wide trench. :shocked:
Illini22
Gold Member
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- Northern Illinois
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- 2013 Kioti dk40 hst, wright stander zero turn
You dig around it the same way you find other utilities. Dig parallel to the run, chip over with a tile spade to find trench with utilities. Once you find existing trench, probe down with spade, expose utilities, then bring backhoe in to clean out area to repair pipe, wires, cable, etc.
BruceWard
Platinum Member
The 6' wide trench is going to be wide and angled or stepped. Otherwise it could collapse and kill whoever is working in it. My guess is that at a minimum you are looking a minimum of a 2' wide 6' trench with a 2' wide 3' trench on both sides.
As you backfill you can install the electrical conduit beside the geothermal loop.
As you backfill you can install the electrical conduit beside the geothermal loop.
tshep
Gold Member
If I may...
I suspect if you're 1800 ft from power, you're also setting septic lines.
They're generally deeper anyway, stay wet, arranged in a grid pattern, and a lot safer to mess around or near.
Win, win, win for same trench geothermal.
I suspect if you're 1800 ft from power, you're also setting septic lines.
They're generally deeper anyway, stay wet, arranged in a grid pattern, and a lot safer to mess around or near.
Win, win, win for same trench geothermal.
OP
955Lincoln
Gold Member
Thanks for the idea. This may vary in different states but it would never work around here. On a conventional system our pipes are very close to the surface and the square footage wouldn't come close to what is needed.
eepete
Platinum Member
Just to be sure I understand the underlying situation:
1) You are the one digging this 1800' trench for power, not the power company.
2) Since the labor is "free", it seems like a good idea to put in a line for geo while the ground is open.
3) You looking at about a 5 ton geo unit or less (loop length).
4) 6 feet of depth is deep enough for where you are to do geo.
Short answer: I think it would work, but you need to check the technology and price it both "this way" and "traditionally".
Long explanation: If this were a "normal "geo, you'd dig a 3' wide trench and put a loop on each side, with 2' of vertical separation. If you dig a one foot trench, you would get just one loop (or a total of 3600 feet). Since you can't get down there, you'd have to do something like dig, put the bottom layer in, fill with 2', put the return layer in, fill with 1', and then you are are 3' deep for power.
This works because you have the time to do the steps. I'd check with the power company/local codes but suspect it would be OK.
There is another unknown here. My 8 tons of loop consist of 4 300' trenches with .75 inch pipe on each side for a total of 4800 feet. But the longest loop is 600 feet long. There is a manifold fed by some 1.25 inch pipe from the house. You would have a single 3600 foot loop, or 6 times the length of my loop. You'd need to figure out what size pipe to put in so that would work. It would not be surprising to see that be a 1.5 inch pipe.
If you needed just 3 tons of capacity, which might be around 2000 feet, it might be better to dig 4 250 foot trenches with your 1' bucket and do the bottom then top of a loop as described above. More digging in addition to the 1800 foot electrical trench, but the pipe might be cheaper.
I think you get the idea. Figure out the pipe size to make this work. Then for grins, price a more normal loop configuration and see what the pipe cost. Then try to put a figure on your "free" time. I'd also bounce this of a geo installer, and find out if there is some hidden problem with an extremely long loop like this. The installer can also check you numbers (feet of lines for a given tons of capacity, size of lines) and verify the depth question.
Terrain doesn't matter- the pump sees only friction loss of the pipe.
Note also that multiple same length loops into a manifold pit make diagnosing a leak easier if you mark the manifold pit carefully. With a single 3600 foot loop, if it leaks there is probably no good solution other than dig a whole new system.
Here are two pictures. The first is the four trenches as they lead to the manifold pit. At this stage, the fill in process was just beginning. The second picture is a close up of the 3' wide and 6' deep trench. You can see the lines on each side separated by about 2'. You can also see where I ran some conduit in the trench about a foot above the geo, and then that conduit would be about 3' under the ground. You can see that the wide of the trench changes the whole approach as to how you do things.
Hope these thoughts help, good luck with it!
Pete
1) You are the one digging this 1800' trench for power, not the power company.
2) Since the labor is "free", it seems like a good idea to put in a line for geo while the ground is open.
3) You looking at about a 5 ton geo unit or less (loop length).
4) 6 feet of depth is deep enough for where you are to do geo.
Short answer: I think it would work, but you need to check the technology and price it both "this way" and "traditionally".
Long explanation: If this were a "normal "geo, you'd dig a 3' wide trench and put a loop on each side, with 2' of vertical separation. If you dig a one foot trench, you would get just one loop (or a total of 3600 feet). Since you can't get down there, you'd have to do something like dig, put the bottom layer in, fill with 2', put the return layer in, fill with 1', and then you are are 3' deep for power.
This works because you have the time to do the steps. I'd check with the power company/local codes but suspect it would be OK.
There is another unknown here. My 8 tons of loop consist of 4 300' trenches with .75 inch pipe on each side for a total of 4800 feet. But the longest loop is 600 feet long. There is a manifold fed by some 1.25 inch pipe from the house. You would have a single 3600 foot loop, or 6 times the length of my loop. You'd need to figure out what size pipe to put in so that would work. It would not be surprising to see that be a 1.5 inch pipe.
If you needed just 3 tons of capacity, which might be around 2000 feet, it might be better to dig 4 250 foot trenches with your 1' bucket and do the bottom then top of a loop as described above. More digging in addition to the 1800 foot electrical trench, but the pipe might be cheaper.
I think you get the idea. Figure out the pipe size to make this work. Then for grins, price a more normal loop configuration and see what the pipe cost. Then try to put a figure on your "free" time. I'd also bounce this of a geo installer, and find out if there is some hidden problem with an extremely long loop like this. The installer can also check you numbers (feet of lines for a given tons of capacity, size of lines) and verify the depth question.
Terrain doesn't matter- the pump sees only friction loss of the pipe.
Note also that multiple same length loops into a manifold pit make diagnosing a leak easier if you mark the manifold pit carefully. With a single 3600 foot loop, if it leaks there is probably no good solution other than dig a whole new system.
Here are two pictures. The first is the four trenches as they lead to the manifold pit. At this stage, the fill in process was just beginning. The second picture is a close up of the 3' wide and 6' deep trench. You can see the lines on each side separated by about 2'. You can also see where I ran some conduit in the trench about a foot above the geo, and then that conduit would be about 3' under the ground. You can see that the wide of the trench changes the whole approach as to how you do things.
Hope these thoughts help, good luck with it!
Pete
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OP
955Lincoln
Gold Member
Thanks for your input Pete. The pipe size will most likely be the killer. I didn't realize that most "normal" systems were parallel loops which makes more sense. It's a shame because the farthest half of this loop would be planted in spring (water) saturated ground and the thermal exchange should be excellent.
My house will be fairly small. I wouldn't be surprised if 2 tons was right on the money.
In regards to #4. Is that a question or do you know 6' is deep enough for my area? I just got this idea yesterday and haven't done any research yet.
Thanks again :thumbsup:
My house will be fairly small. I wouldn't be surprised if 2 tons was right on the money.
In regards to #4. Is that a question or do you know 6' is deep enough for my area? I just got this idea yesterday and haven't done any research yet.
Thanks again :thumbsup:
JimRB
Veteran Member
My geothermal used slinky pipe in the trenches. The trench was as deep as the septic tank contractor's backhoe would dig. The pictures suggest it was deeper than 6 feet. I thought the electric was 3 feet deep in another trench far away. 3 ton system to condition about 2700 sf designed more to cool than heat as we have more hot days than cold days. Google search geothermal trenches and geothermal ground temp for some facts.
eepete
Platinum Member
I don't know what depth would work in your area. Like many topics involving "the ground", one has to ask around and see what's done locally.
The "slinkly pipe" approach is an example of something that works in some areas, but not others. And if you in the south, and focused mostly on cooling, if the ground heats up to 80 degrees in the summer things still work just fine.
Our frost line here at a 36 degree latitude is around a foot. I've never seen the ground frozen more than 5 inches. A concrete pad on 4 inches of gravel will never see a frost heave here. That would be a very different story from up in New England.
I don't know why you couldn't do your own loops, just work a loop at a time into a manifold pit. Biggest problem is the manifold pit accumulating water. If it were me, my labor, and pipe I'd go up about 20% from whatever was recommended to insure it would all work. When you trade your time for money, often you can get a "better" result than what the trades would normally do.
Good luck figuring it all out!
Pete
The "slinkly pipe" approach is an example of something that works in some areas, but not others. And if you in the south, and focused mostly on cooling, if the ground heats up to 80 degrees in the summer things still work just fine.
Our frost line here at a 36 degree latitude is around a foot. I've never seen the ground frozen more than 5 inches. A concrete pad on 4 inches of gravel will never see a frost heave here. That would be a very different story from up in New England.
I don't know why you couldn't do your own loops, just work a loop at a time into a manifold pit. Biggest problem is the manifold pit accumulating water. If it were me, my labor, and pipe I'd go up about 20% from whatever was recommended to insure it would all work. When you trade your time for money, often you can get a "better" result than what the trades would normally do.
Good luck figuring it all out!
Pete
OP
955Lincoln
Gold Member
Do my own loops, as in, a seperate trench project or in the power trench? The power trench is a long straight run that ends up 1800' from where my house will be. Actually, add another 300' or 600' of pipe to that figure. 1800' is to the barn and the future house will be 300' farther away.
I like to add too. If I need 2 tons I will go with 3 for example. With a variable speed compressor humidity is not an issue anymore.
