lukegabriel
New Member
Posts:4
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| 20 Sep 2007 05:39 PM |
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I'm pricing out geotherm in the Montreal area, and I'm looking to lay horizontal loops to save a buck or two, simply because I can. I told that to the nice man who came to visit today, and he said that horizontal loops aren't good in the Canadian climate because frost heave 'could' heave a rock into a loop and damage it.
I think this is absolute... horse puckey. However, I'm looking for a second (or third!) opinion.
I reckon that if I bury my loops 5-6 feet deep, they'll be below the frost line, and if I find the ground is super rocky (I have good solid till here), I'll just line the bottom of the trench in... clay? which should at least slow down the rocks.
Any help would be appreciated!
Thanks,
Luke |
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Palace Geothermal
Veteran Member
Posts:1609
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| 20 Sep 2007 07:11 PM |
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I would agree with you. As long as you bury the pipes below the frost line and use a bedding material you will be fine. |
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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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PanelCrafters
Advanced Member
Posts:680
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| 20 Sep 2007 07:14 PM |
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Posted By lukegabriel on 09/20/2007 5:39 PM
I told that to the nice man who came to visit today, and he said that horizontal loops aren't good in the Canadian climate because frost heave 'could' heave a rock into a loop and damage it.
I think this is absolute... horse puckey. I certainly wouldn't believe that anything would be moving below the frost line. Maybe he meant that a rock within the frost area could be pushed down into the loops? If so, just bury them deeper. |
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| ....jc<br>If you're not building with OSB SIPS(or ICF's), why are you building? |
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lukegabriel
New Member
Posts:4
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| 20 Sep 2007 11:47 PM |
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Hmm... I tried to google the science behind frost heave, I I turned up dry.
It makes sense to me though about rocks moving down, into the pipes, but I've heard about farmers fields 'growing' rocks.
...
Burying deeper does seem to be the logical solution eh? Think the clay liner is worth the money and hassle?
Luke |
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Palace Geothermal
Veteran Member
Posts:1609
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| 21 Sep 2007 08:22 PM |
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Rocks might move up, but not down. as long as you are below the frost line, you will be OK. Remember though that when you are heating your house, you are taking heat out of the ground. So be sure you are 1-2 feet below the frost line. If the soil is rocky, you need to protect the pipe frost or no frost. There is a little movement in the pipe as the temperature changes. A sharp rock against the pipe could eventually damage the pipe. Sand works as a good bedding material. Good luck |
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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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dmaceld
Veteran Member
Posts:1465
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| 21 Sep 2007 08:28 PM |
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Posted By geodean on 09/20/2007 7:11 PM
I would agree with you. As long as you bury the pipes below the frost line and use a bedding material you will be fine.
How would a very weak concrete mix work for bedding? Concrete mixed with only about 1/4 to 1/2 the usual amount of cement and using fine aggregate. I would think it wouldn't be too bad in price, would provide good thermal conductivity, and would be just hard enough to provide good protection to the pipe but weak enough to fracture as the earth moves, if it does. |
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| Even a retired engineer can build a house successfully w/ GBT help! |
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dmaceld
Veteran Member
Posts:1465
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| 21 Sep 2007 08:32 PM |
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Posted By geodean on 09/21/2007 8:22 PM
Sand works as a good bedding material. Good luck That is if the ground is damp or wet. If sand is dry it becomes a good insulator. Old time blacksmith shops used forges that consisted of a bed of sand inside a wood box! How would you like to have a fire inside a wood box in your shop? :-)
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| Even a retired engineer can build a house successfully w/ GBT help! |
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Palace Geothermal
Veteran Member
Posts:1609
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| 21 Sep 2007 08:33 PM |
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Concrete is not recommended for bedding or grouting geothermal pipes. As concrete cures, it shrinks a little. Thus there is not good contact between the pipe and the concrete which greatly reduces the heat transfer. |
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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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dmaceld
Veteran Member
Posts:1465
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| 21 Sep 2007 08:41 PM |
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Posted By geodean on 09/21/2007 8:33 PM
Concrete is not recommended for bedding or grouting geothermal pipes. As concrete cures, it shrinks a little. Thus there is not good contact between the pipe and the concrete which greatly reduces the heat transfer. That's right. I didn't think about that. Would the grout used to fill in loop bore holes be feasible as a bedding material? Or does it shrink also if it dries out? I know bentonite is used because it expands when it gets wet. Now that I think about it, I've seen some references to placing soaker hoses in the ground above horizontal loops to wet the ground if it tends to dry out. That's probably cheaper than some fancy, dancy, bedding material.
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| Even a retired engineer can build a house successfully w/ GBT help! |
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Palace Geothermal
Veteran Member
Posts:1609
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| 21 Sep 2007 08:50 PM |
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the grout used in bore holes is bentonite mixed with sand in a ratio of 1 part bentonite to 4-6 parts sand. This would work great, but is not necessary. Soaker hoses are a good idea if the soil is really dry. |
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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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lukegabriel
New Member
Posts:4
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| 24 Sep 2007 09:34 AM |
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I talked to a rep from waterfurnace, and also since then I've talked to another geothermal installer, and both hadn't ever heard of the piping being damaged by moving rocks.
So, if I do end up going with geotherm, Unless there's something really sharp looking at the bottom of the hole, I'm not going to bother lining it with anything.
You've all had great ideas and feed back! Thank you!
Luke |
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drogers
New Member
Posts:50
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| 29 Sep 2007 07:14 PM |
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I used to live an hour south of you. Most years frost will not penetrate 5-6 feet, most years. When it does you are going to look back at this post and realize some of these old people have more wisdom than you thought. |
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tuffluckdriller
Advanced Member
Posts:630
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| 03 Nov 2007 01:06 AM |
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A heaving ground loop usually will only happen if the system is undersized in the first place. This will make the geothermal heat pump work harder than it should have too, strip the ground of heat, and freeze the ground.
As far as it causing rocks to move, just bed your pipes. There shouldn't be any problem then.
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| Clark Timothy ([email protected])<br>Geothermal Heat Pumps: Heating and Cooling that's Dirt Cheap!<br>www.pinksgeothermal.com |
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