I've been doing alot of research while designing a new house for my pond property and am interested in using a geothermal heat pump. There are many ways this can be done with using a closed loop system underground, an open loop system where the water is pulled from a well and discharged to a lake, river or POND. There is also a system where a closed loop of the HDPE pipe is sunk to the bottom of a pond or river. This is what I am most interested in, with the open loop my second choice. (I have 2 wells near the house location)
Has anyone constructed a system like this? The following article is very positive about this and there seems to be no downside.

http://www.waterfurnace.com/earth_loops.aspx

The tax incentives are also outstanding where there is a 30% rebate from the federal government and also rebates from states.

http://i39.photobucket.com/albums/e188/buzzworth/800px-Pond_Loop_Being_Sunk.jpg

sean

Dwight up in Minnesota has a 3 stage geo system like you want to use (closed and in the pond). I'll bet if you send him a PM he'd tell you about it. He said that even in sub zero temps the electric 3rd stage hasn't kicked on yet.

Buzzworth,

I've had a geothermal Water Furnace since 1994. It's excellent (supposed to be the most efficient of all heating and cooling methods) although I'm sure my heating and cooling bill would be lower if I didn't have a cathedral ceiling!

My technician says I have tops a couple of years until I need the unit replaced. So it appears about 16 to 18 years is the life of these units? Or perhaps it's just the compressor, I'm not sure.

At some point I will go to a closed loop system that is horizontally or vertically placed vs. my present open loop system if there is no effective way to ream out the water line. Take a look at the photo below and you will see why. This is what the inside of my water line looks like that discharges into the pond. (Open loop)



Here's the same discharge end with the pond drained down for maintenance.




I assume it's this way the entire length of the line due to iron and carbonate deposits. If someone can assure me I'm wrong I'd be glad to hear it. At some point I fear it will clog and effect my Geothermal unit. My water is extremely hard at 400 to 500 mg/l with about 2 1/2 mg/l or iron, and if one's water is not, it may not be an issue.

I think putting your water line in the bottom of the pond would be O.K. as long as you don't ever plan on seining the pond! That's why I have to forego that option as I seine my ponds annually -- although I could possible use one of the smaller ponds -- and not seine it. It could come to that due to cost issues.

I do wonder if the loop would be more efficient in the ground vs. in the bottom of a pond that gets down to 39 F. -- in northern temperate climates -- vs. a little warmer 6 or 7 feet below the ground. Not sure what the temps gets down to down there. Perhaps it's not much warmer?


Here's something some folks neglect on heating that can really make a difference: Passive heating of your house via windows facing south. I have lots of windows on my log home facing south and we keep our geothermal unit off from October through November. Actually we shut it off in September too to as their is not a great need for cooling. Sometimes it gets too warm up into the 80's in the house in October due to the windows and we have to close the blinds!

Here's some info I gleamed from my geothermal technician as I was interested in using geothermal water for my fish raising:

My open loop which is a 2 1/2 ton system drops my well water source discharge temp ~ 10 to 17 F. in the heating mode to about 40 F.

In the cooling mode it increases the well water temp ~ 16 F. to about 70 to 75 F.

The lower the flow the higher the temperature change.

If anyone considers an open loop because it discharges into their pond and thinks it will nullify evaporation, I have my doubts. My discharge is 20 gpm but from appearances I don't think it adds that much water to my .62 acre pond.

my system has been in since 1991: a closed loop geo thermal now probably buried in the bottom muck. It's workrd well,even with my cathedral ceilings and large windows facing southwest. My compressor is probably on it's last legs,too,although I think the buried pond loop is fine.the thermostat need to be set and left. My system is not a heat on demand,where you turn the thermostat down when you leave in the morning,then turn it up when you return.Back up heat is a 240volt heater that when on really turns the electric meter spinning! as far as seining,I,ll find out in about 7-8 years when I remove the paddelfish.

Bremer pond geo project

Thanks, guys. Dwight, I appreciate all of your statistical work and details.
I am going to be working with a friend that is in the HVAC industry, as he is the one that suggested I look into it.
After much reading, I have seen that in my area that the loop in the pond needs to be at least 6 feet under and that is no problem since I will be 12 foot when the pond is refinished and holding.
I have the "luxury" of renovation over winter and into the spring of my pond, so I can be sure the loops are strategically placed before the refill.
My friend is planning to use this as an experimental project for his company and is going to do much of the layout gratis. I will get the equiptment at a relatively cheap price and then let him use my house for demos.
The house will be a timberframe structure and be totally enclosed with SIPS so it will be quite tight and have an air interchange unit to dispell moisture-laden air.
As the design and implementation proceeds, I will keep everyone updated.
Thanks all....this is a great place for many reasons.

sean

Cecil,

Do you have problems with freezing in the winter? We are also looking at geothermal with an open loop, discharging to the pond. At 20 gpm, that is lots of water pouring onto the surface of your ice. I use our pond for skating and ice fishing. I am worried that that much discharge would cause slushing and uneven ice. Our pond has about 1/2 acre of surface.

Maybe this is why you put it under the surface, but I heard that pumping water into the pond without aerating it can cause problems as well.

Pumping 20 gpm into a pond won't hurt it.. Also I don't think you should run it too the surface..

Yes I put it into the pond under the surface to prevent freezing. However as BGKiller says 20 gpm is a pittance and insignificant for oxygen issues in a .62 acre pond that is 1 million gallons.

As i said earlier I would go with a closed loop anyway if I were you. The open discharge even at 20 gpm is intermittent and doesn't have any advantages as far as compensation for evaporation.

FWIW: I think there are advantages to each of the options; but we ultimately went with the verticle system when we did a house remodel recently.

Update:

The issue where my discharge hose is clogging shut will not be an issue at some point so I won't have to go to the expense of installing another one or a closed loop system.

Turns out my local plumbing service has a solution they can pump through that will clean out the discharge hose. They have also assured me it's non toxic to the pond.

They are also now selling the same brand of geothermal units that I have. So when the time comes to replace the unit...

Here's what my discharge hose looks like now:



I thought this might be of interest to some of you.

I went to a local home and remodeling show this weekend. There were a few HVAC dealers there and most were touting geothermal. I spoke to a couple and when I referenced having a pond that is accessible for use, they were very helpful with tips on what they would like to see when the pond is renovated.
They have floated in the pipe before but having a clean bottom to work with was a much better situation. There have been problems/questions as to how well they could arrange the pipe array in the past and using spacers between loops is beneficial. They also would prefer to place the loops off the bottom for better circulation around the HDPE.
With the 30% federal tax credit and the state incentives, I can see no downside to going this route. Heck....I want to build this house just to use some of the newer technologies out there.

Buzz

Hey I'm a refrigeration mechanic in Canada. Everyone here uses closed loop systems, pond is ideal because it way easier and cheaper then boring. All the piping will last longer then you (they say). But like Cecil said probably wont get much more then 10 years out of it because the compressor will blow. Become friends with your hvac guy, you can always fix something for cheap if there isn't a mark up!

This link documents our geothermal project.
Geothermal Install

Dwight:

Have you been able to document any water temp changes in the pond that could be strictly attributed to the Geothermal system?

If you were to run an open system, do you think it'd change the water temp in the pond at all?

Cecil, you have an open system. You say it's 20 gpm, but have you verified it?

How big is the well for your house, and do you run two different wells? One for house water supply and one for geo water supply?

Flow out of the discharge is probably not 20 gpm but the pump for the house had to be 20 gpm to run the geothermal. I haven't actually measured it but if I remember I will do so when I drain the pond.

One 4 inch well 20 gpm for the house and geothermal.

Sorry about the long post. Just figured I need to explain.

I would like to share with you a insulation technique I done in 2009 that is saving me thousands and it only cost me an Extra $1200 (difference in insulation company price quote). My Electric bill 14 month average is $146.28. That is less than 50% of what comp. houses in my area pay.

My original thinking after talking with contractors was I would do the polyurethane closed cell spray foam and that cost I considered to be high. That is when I decided to do self educating on insulation since I was my own contractor for building my country home. I understood what the R Value (Thermal resistance) & U Values (overall heat transfer)actually mean. I then figured me a cheaper and better way to do things when it came to the insulation.
I actually thought about the idea on an offshore fishing trip. Sitting there fishing someone slid out and opened the 5 day ice cooler under the rear seat to get some Ice on Sunday we put in there on Thursday night. When I heard man this thing sure does keep ice good my answer about insulation hit me like a ton of brick on the head. That cooler is insulated with only about 1 in thick polyurethane closed cell foam (AKA R Value). It is sealed very well to prevent heat transfer (AKA U VALUE)(which defeats the purpose of the R Value insulation). I also quickly remember how much ice would have been melted when some knuckle head leaves the cooler not shut well. Now on to what I did.

Instead of doing the more expensive 2" closed cell for the walls that the insualtion company recommened. I did a much cheaper technique that we called Flash and Batt. I flashed the walls & stud (side contact only on the stud or you get into the expensive labor of having to shave foam off the stud before drywall can be installed) with the closed cell foam to seal of the Air leaks and prevent heat transfer (AKA U Value). This made the R Value of the regular wall Batt insulation much more efficent. I then Batted with R15 (normal is R 13) to give my wall a near R20 total value and Dramatically increased my U value by removing heat transfer. Also so you understand heat transfer in the world of science there is only heat. Temperature starts at absolute zero and then heat is added. In colder temps the heat transfer is considered to transfer from the interior of the house outside instead of cold entering.

Next was the top. The insualtion company wanted to spray closed cell to the roof (expensive again) and heat and cool the attic that I use for storage (floor system in attic). I was like I think not, I am not into just waisting money. Then they said well lets just insulate between the floor system after you get the drywall installed just like a regular house would. I thought just a second and said NO. Lets install the sheet rock like a regular house and then flash it like we did the walls before blowing in the insulation. The insualtion agent said I have not done that and I do not know if flashing will bleed thru the sheet rock. I said well lets go to lowes and get a piece of sheet rock and you can spray it before you leave and we will see. We did and no it did not bleed thru the sheet rock. So after the sheet rock was installed we also sprayed it with a flashing of closed cell like we did the walls and then blew in regular insualtion over the top to come out with a near R40 R value and the close cell increased the U Value. So Basically I am sealed in like an upside down cooler with closed cell insulation. To give you an idea of how I use my heating and cooling my wife sets the thermostat at 72 year round. In the winter when we not at home she turns it down to 69 and the summer about 75 when we are gone. I got a good laugh out of the A/C company one time during a 100 degree summer day when the unit went out (bad Valve). They called and wanted to know if anyone had been trying running the A/C since it was only 78 inside and 100 outside. They acted like they did not was to believe me when I told them now one had been home since 7am and the A/C had been off since around midnight.

Anyway I hope this post me be some help to someone since I am not good at typing and this post took a good bit of time to type.

That is a great idea - especially the ceiling...

Are your exterior walls 6"?

Tums, could you go into more detail about the "flash"? I'm not grasping it 100%.

Are you saying that the wall studs were "flashed" with a thin coat of closed cell foam before the drywall was installed"
Or was the whole wall stud and inside of the outside sheathing given a thin coat of the stuff?

The ceiling drywall and studs were sprayed with a very thin coat of Closed Cell Foam from the top before the bats were installed?

When I finally get around to building a pole building for aquaculture, I'm seriously considering having a south facing wall a trombe wall. That is, a block wall painted black with large glass windows about 4 inches out to heat the block wall to 150 degrees in the winter via sunlight. There are slots in the walls up high and low that passively circulate the warm air through the a higher slots due to the fact that warm air rises, and the cooler air in the building sinks and comes into the area of heating via the lower slots. In the warmer parts of the year the glass is shaded with economical shades that are made just for that purpose.

2X4 studs in the walls. 3/4" OSB wrapped with in a standard material. Brick exterior to the roof & Vynil siding in gables.

Flash basically means you run the foam sprayer across and it generally leaves a coatin of closed cell foam over .5" and up to 1" thick. The thickness depends on how fast the spray operator moves his hand.
Flashing the interior part of the stud from where it meets the OSB but not all the way out to where the drywall will meet the stud. Basically the sprayer is moved down the corner and held back far enough to spray the side of the stud and not the face. Studs transfer heat more the closer you get towords the exterior wall. It basically has the same effect as using a 2x6 stud to move your drywall farther away from the heat.
The ceiling drywall was sprayed from the top and the trusses and flooring was sprayed the same way as the wall was partially up the stud several inches for a good seal. The reason for doing this is ths same as the heat transfer will lose engery having to travel longer distances and slower via thru wood before influencing your internal enviroment. We even had inserted all of the fixtures and vents in the ceiling before spraying to get a good seal around those also. I put painters tape over the vent holes on the can lights to make sure they did not get plugged. Had even run all the electrical & wiring down the walls so all the holes going into the interior wall would be sealed as well. After the flash their we just simply blew in regular attic insualtion to what was normal for my area.

Cecil that is a very good Idea. Here we deal with cooling issues more months than we do heat. I raised my Metal roof an extra inch to give more ventalation air flow to cool between the metal roofing and the OSB. A house pretty much needs to be designed for its location and insulated well to be economical. It is easy to let the elements in when it is comfotable outside. If you can keep out the outside enviroment when is not helpful and economically control the internal enviroment at that time. It is a WIN, WIN.

A couple of years ago we installed a "Water Furnace" with two 300-foot closed-loop vertical wells.

Due to having a log home, we can't really add any significant insulation.

First, let me say, that I am extremely happy with the system we installed. We also figure that we saved about $2400-$2600 the first season, which was far in excess of what we expected (we are into our second season).

We looked at three alternatives for the heat exchanger, and one included one of the ponds. Being where we live, the HVAC people said that when the water is warmest, we need the water cool, and vice versa. We could have done a field, but ... We chose two 300-foot deep closed loop wells that enter the house at 7-feet below ground level. The unlined wells were done in less than a day, which was far cheaper than trying to trench to the pond, or to do trenches for a field.

The system has four separate zones and thermostats which allows us to only only heat/cool the areas we use during that time of day. Our hot water is essentially free. Best of all, the entire system draws very little current when cooling or heating, so when we put in a whole house generator, we only had to put in an 8KW propane system, which is far more than adequate for everything we have -- except the well (it is 600 feet away, and on a separate meter, with a separate small generator). The generator truly runs the entire house, including two refrigerators and a freezer.

Thanks Tums! I understand it now.

That really is the proof in the pudding right there.

8kw for the whole house is really, really good....like by a factor of four good!

Wow that's impressive Ken. My electric bill is still about $500.00 a month even with Geothermal. I'm sure my cathedral ceiling doesn't help.

Our house also has a cathedral ceiling, but probably smaller. Two floors over 24 x 48 heated basement. Our monthly electric has run between $65 and $165 over the last 20 months. That is for heat, AC, and hot water, plus the appliances, lights, etc.

Cecil, how much of that electric bill can be attributed to your trout pond well pump?

None right now. I may request an audit. My bill was the same for the two years I didn't run the well pump as it was when I did. No one comes to check the sensor as it's remotely detected. I don't trust the remote sensors and have heard they can be inaccurate. Typically when I run the well pump it's about $100.00 per month.

I did notice the rates keep inching up every month and every year. It sure would be nice to produce my own power even if it took a few years to pay for it.

I did a full spray foam insulation when I built my house.. I have to say its damn near airtight and very sound proof still can hear redneck 4x4's go by but very faint.. My ceilings are 8" of spray foam with 18" of blown in (needs another layer settled to about 12").. I plan to ad geo eventually but not through the pond just underground horizontal undr my garden..

BGK was that open cell foam or closed cell done in layers?

I can't remember I wanna say open cell and no it wasn't done in layers, sprayed and shaved.. I think the Close cell was ridiculously more expensive and not tecommended, more used for coolers and commercial