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Old 12-16-2011, 08:56 AM   #1
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Anyone ever put in an 'open loop' geothermal heat & cooling?


We are building a lofted ranch house on 80 acres in S/E NE next summer. Our plan is to use an open loop system for heating and cooling using our well water and exhausting it into a pond that's already right there.

Our water table is pretty sufficient here, probably because we are close to the Big Nehama River and there is a large aquifer underneath also.

I don't hear of many folks using the open system much anymore. However, there are several closed systems around here.
And there is a contractor nearby who installs geotheremal systems.

Our wells do have hard water. I know we will have lime build-up problems in the A coil. I plan on using a filter to cut that down some.

Can anyone give me assistance on what other problems we are going to run up against?

BTW: We have a Heat Souce One outdoor furnace system for the shop already. So we can have reliable back up heat in winter, if necessary.

Please post your experiences + or -.

Much obliged,
MG
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Old 12-16-2011, 02:02 PM   #2
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Anyone ever put in an 'open loop' geothermal heat & cooling?


Hi Gregg.

There's a ton of variables involved in open loop geothermal.

If the pond is of decent size, and close enough to the house, I would install a closed loop pond system instead. This keeps your GSHP insulated from the harshness of hard water, has lower pumping costs than using a well system for open-loop, avoids aquifer issues, etc.

That said, your BEST option is to contact a professional in your area. They will help you through the details. You can also post over on the www.geoexchange.org forums... friendly guys over there will help get you pointed in the right direction.
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Old 12-16-2011, 11:15 PM   #3
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Anyone ever put in an 'open loop' geothermal heat & cooling?


Moon:

Thank you for the reply. The local GTH outfit has got back to me pushing to sell the closed loop also.
I suppose they are somewhat more efficient, but more $$ on the initial installation, since you need 2 deep wells.
However, I want to have the exhaust water running into the pond (1.5 acre) to keep the level maintained and even somewhat open in the winter. I have bluegill, bass, catfish in it. It is only about 75 yds from the house site.

Much obliged,
MG
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Old 12-17-2011, 05:48 AM   #4
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Anyone ever put in an 'open loop' geothermal heat & cooling?


Quote:
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Moon:

Thank you for the reply. The local GTH outfit has got back to me pushing to sell the closed loop also.
I suppose they are somewhat more efficient, but more $$ on the initial installation, since you need 2 deep wells.
However, I want to have the exhaust water running into the pond (1.5 acre) to keep the level maintained and even somewhat open in the winter. I have bluegill, bass, catfish in it. It is only about 75 yds from the house site.

Much obliged,
MG
Gregg,

A 1.5 acre lake should be perfect for a closed-loop lake loop, unless it's very shallow. You do NOT need 2 deep wells for a lake loop.

And with 80 acres, you shouldn't need a deep style of closed loop system at all. For example, on my 1.6 acre lot, my geothermal loops are in a 6 foot deep, 6 foot wide, 250 foot long trench. This is much cheaper than drilling deep wells.

Check out the geoexchange forums and get help there. I will tell you that I have NEVER seen anyone there recommend an open loop system run off a well pump. Depending on the size of your well pump, it can almost completely erase any of the cost/energy savings of geothermal. When you add in the extra cost of cupronickel heat exchangers (to protect against well water) and periodic maintenance, closed-loop is almost always cheaper in the long run, even with the higher initial cost.
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Old 12-17-2011, 07:15 AM   #5
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Anyone ever put in an 'open loop' geothermal heat & cooling?


Moondawg:

Actually I WANT water running into the pond. It is a pond that (in some winters) freezes pretty deep. Are you suggesting using the lake as a heat sink?

True, I haven't inquired that the electrical $$ cost of running a water well would be. But I just replaced a submersible pump down my dad's 120' deep farmstead water well, and it was terribly high. But it has been there for 28+ years.

Oh yea, the pond is not very deep. And we are going to hoe it our and also raise the spillway to bring it up to 1.5(?) acre.

Mustang Gregg

Last edited by Mustang Gregg; 12-17-2011 at 07:23 AM. Reason: Typo
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Old 12-17-2011, 09:46 AM   #6
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Anyone ever put in an 'open loop' geothermal heat & cooling?


Open loop systems are common in my parts.
Our water is hard like yours so an occasional acid flush is necessary. The only drawback that I can see is the use of the pump adding to the electrical usage. If the water temp is over 59 degrees, it might be more efficient to use a high seer unit. But if your going to fill the pond anyway, I would do it..
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Old 12-17-2011, 10:17 AM   #7
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Anyone ever put in an 'open loop' geothermal heat & cooling?


Master of Cold:

Not sure what the underground water temp is. I know that the cellar temps around here are about 50 degrees F in the summer. We live just on the NE-KS border, if there is a longitudnal ground temp chart out there.

What I see as an advantage is that I have lots of water with only a 50' well on the property. And of course the exhaust water will maintain the pond. If it turns out that the pond would stay somewhat clear during the winter, we could keep some the cows here for winter too.

Thank you all,
Merry Christmas,
MG
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Old 12-17-2011, 12:07 PM   #8
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Anyone ever put in an 'open loop' geothermal heat & cooling?


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Originally Posted by Mustang Gregg View Post
Master of Cold:

Not sure what the underground water temp is. I know that the cellar temps around here are about 50 degrees F in the summer. We live just on the NE-KS border, if there is a longitudnal ground temp chart out there.

What I see as an advantage is that I have lots of water with only a 50' well on the property. And of course the exhaust water will maintain the pond. If it turns out that the pond would stay somewhat clear during the winter, we could keep some the cows here for winter too.

Thank you all,
Merry Christmas,
MG
Greg, I am suggesting that you could use the pond as a heat sink. (well, heat SOURCE in the winter!) It is very easy to put over one million gallons of water(3gpm per ton of heat/cool) through a heat pump in a season. That's a significant amount of water, and if your pond is not already fed by a stream, eventually that water is going to need a place to go. Even feeding the pond with your geothermal "wastewater" will not keep the pond from freezing over in the winter.... by the time the groundwater passes through the heatpump, has heat removed, and then travels the 75 yards through the ground to the lake, it will be VERY close to freezing.

If you have a hoe to dig your dam/spillway, then you could save significant money by digging the trench for your geothermal loops yourself. Excavation is the biggest cost of loop installation.

Even though you have plenty of water right now from your 50ft well, that might not be the case in a few years, depending on the aquifer and how many other people start pumping a million gallons a year out for their heatpump. :^) You also need to make sure that the well can supply ~12gpm (for an average 4ton system) for roughly 24 hours straight.... during the very coldest of winter, a right-sized geothermal system will run almost all day/night. This is NOT the time to find out that your well won't give enough water to keep the heatpump happy.

You also need to check local codes to see if you're even allowed to run a "pump and dump" geothermal. Many areas require a reinjection well instead... take water from the aquifer, run through the HP, and then back down into another well.

Lots of things to think about. Please don't take my advice as a professional. I'm just a "hobbyist" who believes more people should use Geo.
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Old 12-17-2011, 01:09 PM   #9
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Anyone ever put in an 'open loop' geothermal heat & cooling?


Yes, I have a small back hoe (on my skidsteer). My neighbor is a semi-retired plumber who has a Ditch Witch trencher and a case backhoe/loader. He does a lot of work for me and I help him with work too. So that part won't be a big expense.

As for a place for excess water, the pond has a spillway.

Thanks.
MG
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Old 12-26-2011, 09:33 PM   #10
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Anyone ever put in an 'open loop' geothermal heat & cooling?


I have professionaly installed almost thirty geo systems. if you asked me to hook up a geo under the terms you are suggesting I would have to say no. Your idea sounds nice but it just screams problems and warranty issues. I would go along with the guy that suggested the pond loop system. Pond loops are easy to install and they are some of my best performers.
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Old 12-26-2011, 10:47 PM   #11
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Anyone ever put in an 'open loop' geothermal heat & cooling?


Tomskids:

I tried to send you a PM. But that system won't work. So I'll post here.

What would warrantee issues be? I reckon that the A coil (if that term is right) would be prone to liming up. What else?

Thanks!
MG
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Old 12-26-2011, 11:04 PM   #12
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Anyone ever put in an 'open loop' geothermal heat & cooling?


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Old 12-27-2011, 04:34 AM   #13
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Anyone ever put in an 'open loop' geothermal heat & cooling?


On a very cold month, you could easily use over 260,000 gallons of water.

Min water flow of an open/pump and dump that I've seen is 1.5 gallons per ton per minute. Thats still a lot of water if the geo has to run 24/7(8,640 gallons a day) for any length of time.
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Old 12-27-2011, 10:27 AM   #14
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Anyone ever put in an 'open loop' geothermal heat & cooling?



That is a lot of water, for sure. I will investigate further.

At present we heat our 1800 sq ft (1890's era) house and 2400 sq ft shop (two story) with an outdoor wood burning furnace.
We may opt for a similar system with the new house and shop.
There is plenty of free wood on the property.

Thanks,
Mustang Gregg
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Old 12-27-2011, 03:54 PM   #15
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MG,
Maybe I should have been more descriptive. By warranty issues I don't necessarily mean from the manufacturer. Although there could be some. I mean more from an installer point of view. For example. If I installed the system and you called me a year later because you didn't have enough heat. Well, I would spend better than 4 hour testing pressures, flows, temps and a few other things. Then lets just say the exchanger is dirty. So I spend a few more hours cleaning that, then a few more testing to be sure it was cleaned thouroughly. Of course I would be expected to do all this on warrranty for free for five years. Then lets say we do all this and discover that it didn't fix the problem and there is a real mechanical warranty issue. Then I have to convince the factory that I have been pumping clean water throught the unit. You see, from my standpoint from an installer this is a lose/lose situation. You get an iffy product and I lose money. I'm not installing your system. So I have nothing to gain here. Maybe you're doing it yourself. Regardless, do yourself a favor and put in a closed loop system. If you really want to pump the well water into the pond you might be able to put in a secondary plate type exchanger that could exchange the well water heat with your geo loops. If that ever gunked up beyond repair you would only be out around 400 bucks for the cost of the exchanger. Just a thought.
Tom
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