Geothermal heat pump

**crater** · 02-28-2008, 07:14 PM

just wanted to add my 2 cents in also jdoll, I haven't got my Geo all in yet but it is going to be 1- 300' well "Pump n' dump system", the idea is that the return water that is returned at the 300' depth will be moved away by the aquafur before it could be pumped back up. The submersible pump will be set at 150' at least 100' away from the return. Here in Iowa they have had some problems with the return water freezing the well in the winter, so they also dig a return pit and fill it with rock just in case the weather would stay cold for weeks on end. then at a predertrimened water temp a valve that automactically switches over to the pit would be turned on to avoid a freezing problem. Sounds like alot of crap that could potentially go bad or fail over time (High maintence) but for a $30ish heating bill I guess I can't complain. My system also costs about the same. mine is estimated to come in for $21K well and pumps included.

**Bill Arden** · 03-02-2008, 12:39 AM

Originally Posted by crater

the idea is that the return water that is returned at the 300' depth will be moved away by the aquafur before it could be pumped back up.

Here in MN it's illegal to pump water back down a well.

I've not heard of water freezing problems as most systems I've seen use a sloped drain pipe that drains when the system turns the water off.

The snow on the ground insulate the ground and keep it thawed out.

Anther problem is that removing deep water can cause problems since that will draw contaminants down into the aquifer.

So the consensus is that "Pump n' dump" systems should use shallow wells.

**boze62** · 03-02-2008, 06:36 AM

I will agree with some of the posts, geothermal units are high maintenance machinery. I have a well to well system (open loop) installed in 1992 in a new home construction. I was living in a 962 sq ft home with elctric baseboard heat averaging $125/month in cost (no A/C). Then I moved up to a 1500 sq ft home with heat and A/C and kept it slightly warmer, and my average that year was the same!

About $3000 extra cost for the system, $3500 to drill a 290 ft well to supply (used the old well as return well or likely would have been another $1500, it is a 120 ft well which handles the return flow). I know I am ahead of the game, but maybe only by a small margin after replacing the pump once, redoing the soleniod shut off and in home supply and a couple of other things. These guys are not cheap.

**crater** · 03-02-2008, 07:02 PM

Yea Bill I'm kind-of leary about pumping back down my well also, but it is not against the law here in IA, I know a couple a people that have the same system and love it, however they both pump back to surface (Pond,creek), I just talked to my HVAC guy, he said that this was the only year he has ever had a problem with the freezing of the well, the return water is around 6d colder going back down than suppied. anyway they have a sollution for it, the discharge pit (French Drain)
BTY I have heard some rummor's that the state DNR is going to be looking into the pump n' dump systems, so it probaly won't be long before the outlawed here also, especially since neighboring states have already have banished them.

**CWinAZ** · 04-06-2008, 02:30 PM

Greetings! I am new to this forum, my first post. I have a question and have been searching for an answer. I live in Metro Phoenix, AZ and want to install an open loop GSHP system using a cistern for water source and return. My home is a 2 story and currently has 2-3 ton air to air HP's. Reading from several sources I would need about 18 gpm of water. How many gallon capacity buried fiberglass cistern would I need? I plan to use the water to irrigate a small area in the back yard and collect water from the roof to add to the cistern when available. Not allowed to drill a well in the neighborhood and am on city water and sewer.

**bartman99** · 04-21-2008, 08:45 AM

Originally Posted by crater

just wanted to add my 2 cents in also jdoll, I haven't got my Geo all in yet but it is going to be 1- 300' well "Pump n' dump system", the idea is that the return water that is returned at the 300' depth will be moved away by the aquafur before it could be pumped back up. The submersible pump will be set at 150' at least 100' away from the return. Here in Iowa they have had some problems with the return water freezing the well in the winter, so they also dig a return pit and fill it with rock just in case the weather would stay cold for weeks on end. then at a predertrimened water temp a valve that automactically switches over to the pit would be turned on to avoid a freezing problem. Sounds like alot of crap that could potentially go bad or fail over time (High maintence) but for a $30ish heating bill I guess I can't complain. My system also costs about the same. mine is estimated to come in for $21K well and pumps included.

Hi Crater,

I just found your post. I was wondering how your system turned out? I am contemplating the same thing. We live in Virginia and have a 400' well (12gpm).

Does your well also supply potable drinking water? That is what we are contemplating too. Any specs on how the water temp in the well is affected by the heat pump return water? One fear is that the aquifer will not be able to handle the temps and will eventually reach a steady state with the HP (ie become too warm or too cold to be effective). Have you or any of your neighbors had a problem with this?

Thanks in advance,

BM

**Bill Arden** · 04-28-2008, 03:09 AM

Originally Posted by CWinAZ

Metro Phoenix, AZ ... open loop GSHP system using a cistern for water source and return.

Ouch.

It's not just the flow rate. you need to figure out how the water is going to be cooled back off again.

I would suggest you start with a closed loop drilled well system. to save costs you could start with cooling only using a water "A" coil or some other water to air radiator.

The closed loop wells last "almost" forever so in your case it is a good way to start.

Edit:
"almost forever" in this case is defined as the life expectancy of burred black plastic pipe.
I believe it's in the 100's of years so it can be considered a gift to future generations since heat pumps are likely to be used more and more in the future.

**statjunk** · 04-29-2008, 04:39 AM

Theoretical question. How far down would you have to dig a well so that when water is dropped down it will return as steam to power a turbine?

Couldn't you theoretically power a place for virtually free with a deep enough well?

Does this make any sense?

Tom

**speedbump** · 04-29-2008, 05:25 AM

That is a good question. I know you can do it in parts of Colorado.

bob...

**jadnashua** · 04-29-2008, 06:49 AM

Geothermal steam very much depends on where you live. In Iceland, they generate nearly all of their electricity that way, but then the island is essentially an old volcano. In some places, it is feasible, in others, it isn't, and unless very near the surface, unlikely to be useful on an individual level. Now, if you live near Yellowstone, maybe it would be fairly easy to tap a hot spring.

**Bill Arden** · 04-30-2008, 05:30 AM

Originally Posted by statjunk

Theoretical question. How far down would you have to dig a well so that when water is dropped down it will return as steam to power a turbine?

I believe it was 4 miles

here in MN when I looked it up.

Drilling a 100 foot well costs $3000 so.... a deep enough well to create power would be way to expensive here.

Edit: I would be far better off investing in that company that wants to do "hot dry geothermal power" in Yellowstone.

**speedbump** · 04-30-2008, 05:33 AM

Not to mention when drilling that deep they start out very big at the top and scale down as they go. The deeper they go, the harder it is and the longer it takes. So by conventional standards, there would be no comparison to cost.

bob...

**statjunk** · 04-30-2008, 12:32 PM

Originally Posted by Bill Arden

I believe it was 4 miles

here in MN when I looked it up.

Drilling a 100 foot well costs $3000 so.... a deep enough well to create power would be way to expensive here.

Edit: I would be far better off investing in that company that wants to do "hot dry geothermal power" in Yellowstone.

Jeeze-o-petes!

**barrybud** · 02-04-2009, 09:26 PM

Hello,

I've been reading through the thread and cant imagine dealing with the wells and the iron or other things that could foul up a system.
I'm in a story and 1/2 cape here in PA with a 4 season oil set up with water baseboards. I originally started looking for a Central A\C system because the summers here can be down right soggy with humidity. What I found was for about 35% more money I could get a direct exchange geothermal system to do both heat and AC over the cost of a central AC system.
This system doesn't use wells or water/antifreeze loops. I have 6 earth taps that are 70 feet deep in a conical shape that all join at the manifold. Two lines run inside the house to the air handler and the system uses R22 refrigerant. I only had an area about 10 feet around disturbed in the front yard with a small trench running to the house for the installation. It cost me a bit more because I had no air ducts run in the house before the geo system. The money I saved in the cost of the oil we would have used in the last 5 years has paid for the system. It also makes all the domestic hot water and the only time it kicks into 2nd stage is when the other half takes an extra long shower right when the heat comes on. The system gives priority to the hot water and the stat will kick in the electric element after 45 minutes if the house doesn't hit the set temp.

Here is a link for more info on the Geo company.
http://www.advancedgeotech.com/techov.html

**Bill Arden** · 02-05-2009, 11:38 PM

The "earth taps" are just another way of saying "Closed loop heat exchanger"

I've considered pounding in pipes and doing the same thing, except with water to transfer the heat to the Heat pump instead of running the freon into the ground loops.

Plastic is cheaper than copper and water is cheaper than freon.

On the other hand each person has to look at what works best in there area and the direct systems are better where the ground temps are close to the freezing point.