The Homemade Heat Pump Manifesto
 

Hello all,

(I have been working on this project since 2009, and I am having great success and fun, but have yet to find anyone on the web doing similar work.)


I live in an older small house (< 1000 square ft.) built in 1892. I am going through the whole house, meticulously insulating it with expanded poly styrene board. I tore off the lath & plaster, increased the thickness of my walls, and I'm layering in 6 inches of rigid foam into the walls, ceiling, and under the floor.

So I'm thinking ahead to a highly efficient heating system. As best as I can determine, a Ground Source Heat Pump (AKA: GSHP) running warm water through a thin (1.5 inch), radiant concrete floor is my best bet.

[* NOTE: Subsequent study suggests that a 'sandwich' style hydronic floor with close-spaced aluminum spreaders will be easier to build and at least as efficient as a thin suspended concrete floor, but that comes much later in the story. *]

I don't have much money, but I am resourceful and very stubborn.

I have found out that the approximate size of a heat pump I'll require is slightly under 12,000 BTU/hr. In HVAC speak they call 12,000 BTU/hr a 'Ton' of Air Conditioning. Your mileage may vary.

I have also found out that here in Western Oregon (Portland), a GSHP will require a borehole about 200 feet deep. It could also be two boreholes about 100 feet deep, etc... Again, your mileage may vary.

I also found out that heat pumps are classed as Air-to-Air, Water-to-Air, and Water-to-Water.

The kind I need is Water-to-Water. The kicker is, that the smallest I have been able to find is four ton (48,000 BTU/hr). So this means that in order to proceed with the project, I'll have to build my own heat pump. In HVAC, bigger is not better... just slightly smaller than big enough is best, economically speaking.

I have built a proof of concept unit that works. Here's a photo:


I built this unit last summer and did some testing. Here's a performance graph:


The COP is calculated for each measurement period, and changes quite a bit, but the overall COP is quite good.

So, is anyone interested in such a project? I have already built a prototype heat pump, it is working and I have tested it and the test results are very encouraging. I have attached photos and performance data at the end of this post.

I am now in the hole drilling phase. I built an earth auger, which would have worked really well in other parts of the country, but in Oregon, where I live the drilling is not so easy. I have increased the power of my auger 20X and I'm getting ready to dive back in.


A properly designed system as I'm describing should be able to operate at an efficiency of over 300%. My prototype has actually shown efficiency over 400%. In HVAC, efficiency can go over 100%, because the electrical energy that is input is not directly converted to heat, but is being used to move heat from one place to another. Strange but true.

So, there are four parts to the project:

0. Determining your heating load.
Free software is available on the web for this. It is also possible
to measure directly, the energy you are using. I have done both.

1. The Ground source loop field.
Here in Oregon, where I live, an 80 foot long, three foot wide,
by four foot deep trench containing about 300 feet of slinky
loops of plastic pipe, per Ton (12,000 BTU/hr) is required.
(* or *)
Two hundred feet of borehole per Ton is required.

2. The Heat Pump.
I have found that air conditioners and de-humidifiers can serve
as a starting place for DIY heat pumps. These can be had for
cheap to free. German children are using Propane gas as a
refrigerant for cooling CPUs so they can play video games faster.
What a concept!

3. The radiant floor system.
From all I have read, nothing beats PEX in concrete for efficiency.
This is seriously messy, but the technology involved is very
straight-forward.

I'd really like to get other people interested in this kind of project. Commercial units installed run $15,000 to $45,000 and up. I'm estimating that I can get mine going for under $2,000. Maybe under $1,000. So far I've spent about $400.

So, let me know if there's interest... I have loads and loads of information I'd like to share.

If we are not the people who can re-purpose pieces of junk that are now headed to the scrap yards and turn them into state-of-the-art high-efficiency home heating systems, who's going to do it?

Humbly Yours,

- AC_Hacker

P.S.: Here's a link to a PDF which will serve as a good overview to our project:



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Welcome AC_Hacker. I don't know if my city would let us do this where I live in Canada, but I'm really interested in what you've written so far. So, for those of us who may not be able to do something like this, please still keep us posted on your status, or if you've got any other ideas you'd like to share.

Where did you learn to invent stuff like this? I wish I knew how to put things like this together, but I wouldn't know where to start. I really commend you for building things like this.

Higgy,

There is tremendous interest in GSHP in Canada. I learned a large part of what I know about GSHP from websites provided by your fair government. Thank you!

> Where did you learn to invent stuff like this?

Lots of reading, being willing to try something, welcoming failure as also a learning moment.

I have friends that like to sail. I've noticed that their best stories are all about near-disasters. Of course, they DID live to tell the tale.

Best of Luck in your own adventures!

Cheers,

-AC_Hacker

Welcome to the site AC Hacker. I'm in a similar boat. I have an older 1800s house that I'm just starting to remodel to get additional insulation into the walls (also thickening them for added insulation). I was also planning on going with in floor radiant heat. One room of the house already has it and it is simply wonderful. Its currently running off the hot water heater (blah). I was thinking about going with a conventional high efficiency boiler as a backup for solar hot water heat. But, your heat pump is very fascinating and I'm excited to see where it goes! Feel free to bounce any ideas around on here. We'll do what we can. :)

Daox,

Thanks for your post.

Commercial GSHP + hydronic floor heat setups in Europe are claiming COPs as high as 5.5.

If you have the cash to hire it all done by experts, save yourself some grief.

If you're on a limited budget, like I am, then the fun begins...

> But, your heat pump is very fascinating and I'm excited to see
> where it goes!

Is there some aspect of my project you'd like to know more about? There's so much to it, I hardly know where to begin...

Best Regards,

-AC_Hacker

Oh gosh, I barely know where to start too haha. How about explaining your drilling rig there? Did you make it yourself? How large of a diameter does the hole need to be? I'm really not familiar with how you do these things.

Drill Rig #1
 

The drilling rig...

I started some notes on the thread over at EcoModding you might want to look there too. At some point, I'll put everything on one thread, probably here. See the EcoModder thread:

The Homemade Heat Pump Manifesto... - Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com

But here's the story...

A local farmer told me that he was able to drill a 35 foot well by using 2 friends an 2 cases of beer (smart farmer).

I started by making a T-handle test drill, that used a water hose, connected by a swivel coupling.


auger-T-handle-test(small).jpg - This is my first test drill, only with a shorter piece of drill pipe, so you can see what's going on. I actually used a 6 ft. section of pipe and when the auger advanced about 5 ft., I added an additional section of pipe. I was able to advance about 13 feet in about 35 minutes. One problem I encountered was that the hose kept kinking, so I had to hold it up with one hand and I turned the auger with the other hand. So I was able to advance 13 feet with only one hand. The other, and more serious problem was that because of the high sand content of the soil, I was having cave-in problems. I didn't know what was causing it, I just knew that my auger was getting stuck and was very hard to pull out of the ground. Later I would discover that drilling mud would solve the cave-in problem.


auger-T-handle-test_upper-detail(small).jpg - This is a detail of the swivel end of the auger. The swivel adapter is not eactly the same as 3/4 pipe thread, but by loading lots of teflon tape onto the threads, I got a satisfactory seal.


auger-T-handle-test_lower-detail(small).jpg - this is a detail of the business end of the auger. The water gushes through the pipe and flushes out the drill-cuttings. I have come to understand that the water is definitely part of the tool. It contributes more to the advancement of the drill than any effort on my part.

I live at the top of an 80-foot bluff and look down at a local river. I did notice that I was hitting rocks at about 12 to 13 feet. What I didn't realize at the time, but have come to know that every well driller understands very well, is that 14,000 years ago, an ancient flood deposited about a foot of clay mixed with basalt river gravel which over fourteen millenia has consolidated in what the locals know as 'hardpan'... it's tough stuff.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
AC_Hacker's Update, Sept 6, 2009:
At the time this was written, I thought I had, indeed hit hardpan. Later work, using tools that didn't obscure the nature of the soil I was digging through, revealed that I had actually hit an area of fist-sized rocks left from a 10,000 year old geological event. I developed a tool (the "steel claw"), shown later, that enabled me to remove the rocks and advance town to a depth of 17 feet where there was very wet, coarse black sand, very good for Ground Source Heat Pump work and worth the extra digging. At that depth, I was actually able to look down boreholes and the see the hardpan layer.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

You may not have anything like this where you live. In fact, a couple of blocks from here, thing might be much better, or much worse.


auger-base(small).jpg - This is the base of the gearmotor auger I put together. Based on my hand-drilling experience, I figured a small motor would do the job, so I got a 1/4 HP 25:1 permanent magnet gearmotor off ebay for $70. A 1/4 HP motor doesn't require a huge amount of structure to support and control, so fabrication was pretty easy.


auger-head(small).jpg - This is the gear motor head. I fabbed an 'L' bracket for the motor and used a 2" square tube for the vertical, and a close-fitting 2" inside receiver tube welded to the L bracket. it slides up & down well and doesn't have too much slop. You can see the hand cranked wench to raise and lower the gearmotor head. It's not optimum, but it works OK.

(By the way, I'm a terrible welder. I have a stick rig, which I have tried repeatedly to master, but it has won every time. So, I bought a crappy little wire-feed welder for $100 and it has worked wonders. Highly recommended.)

The gearmotor I chose is permanent magnet, so I can reverse the direction to unscrew pipe... very handy. I also have a bench test variac that I use to control speed. Works great.

Next post will detail the auger-head swivel... it's surprisingly important.

Best regards,

AC_Hacker

Here on the ocean front the HVAC companies are starting to sell Geo Thermal systems that are really pump and dump units.
They drill your back yard to around 150 foot and pump the water to a storage tank that is used to pre-cool or pre-heat your HVAC unit.
Ground water here flows out at around 55 degrees year round so this works really well in the summer and reasonably well in the winter. (We seldom see below 50 degree days and below 30 degree nights.)
Unbelievably expensive
Starting at $20,000 for the simplest of units.
There are , however, quite a few of them in my neighborhood. (The developer had a deal with the HVAC installers and the prices were financed into the original purchase price)
I have often wondered how hard it would be to make something like that on my own.
I would just bury some 55 gallon plastic drums in the yard about 50 foot down and use that as my storage facility, (removes them from the house and reduces the need for insulation) then move the water to the furnace as necessary.
So that being said, I am very interested in your project and will keep watching for stuff I think I might be able to implement.
S.

metroschultz,

Pump & dump? I'm not so sure I follow what you mean...

I see this term in geothermal usually meaning that an 'open loop' system is being used, and water is being drawn from the ground or river or other water source then heat is extracted and the water is then pumped on to a lake or a river or a different well where it is absorbed back into the earth.

Is this how you mean the process works?

Regards,

-AC_Hacker

Welding Polyethylene Pipe...
 

I've been wracking my brain, trying to figure out how to join the pipe that will eventually become my ground-source heat exchanger.

I know that PEX is pretty good stuff, but because of the way the PEX plastic is made, it can't be welded.

PVC and CPVC is out of the question because it gets brittle.

I've noticed that in all the sources I have read, High Density Polyethylene (aka: HDPE) is the pipe of choice, with 3/4" being the size often used for small, home-heating applications. If the Ph of your soil is not acidic, copper would be good too, but very expensive. So in practice, HDPE seems to be the choice, with life-spans of 50 years guaranteed, and life-spans of 200 years expected!

The only catch is that many states require that the HDPE have all joints & couplings being welded. Since I'm going to be doing this myself, I have considered many alternatives to welding, including barbed connectors and stainless steel hose clamps... should last a good long while.

So, I was at the local gigantic home-improvement store, looking over various kinds of plastic pipe, and I saw big rolls of black polyethelyne water pipe. I zeroed in on the 3/4 pipe and saw that they have two grades, schedule 40 (100 psi) and schedule 60 (160 psi). The schedule 40 was too thin to consider, looks like it could be crushed by the force of the earth above. The schedule 60, however looked really pretty good.

So I bought a short length of the schedule 60 and went looking for possible joining solutions. At a high quality (professional) plumbing store, I did find some very nice looking brass barbed joints which would use stainless hose clamps. I also did some asking about as to welding tools. Turns out that there's a company named McElroy that makes a tool called MiniMc (pronounced 'mini-mac'), that consists of a teflon-faced heating tool, a ratcheting facing tool, and a gripper/slider tool that holds the pipe while it is being faced, heat-melted, and fused. See photos, etc here: (McElroy MiniMc Fusion Machine Overview). Also check out the manual, photos, animations, movies, etc. Quite an education! The local outfit sells the tools for nearly $2000 (OUCH!) they'll also rent them for $45/day or $180/week (gasp). But this doesn't really look like rocket science...

So, on the way home, I stopped at my favorite junk store and got a teflon skillet, to try a wee bit of free-style polyethelyne welding. I put a chunk of aluminum plate on the stove burner, and put the teflon skillet on top of that and set the gas flame as low as it would go (my stove has 35,000 burners). I used an infra-red thermometer and set some short lengths of Polyethelyne upright on the skillet. When the heat got up to about 300 degrees, I noticed a small bead forming on the pipe end, where it met the skillet. I picked up the pipe in my hands and pushed the hot ends together, and to my amazement, welding was happening!


This stuff ain't rocket science. I mean if I can get this close on two tries with a teflon skillet, this is possible!

Now, can anyone think of a way to make a heater tool and a device to hold the pipe securely while it is fusing?

This welding problem is sort of the missing link in the ground source loop field phase of the GSHP project.

Regards,

-AC_Hacker

Looks pretty good. I'm betting you could make something like that clamping tool with some ~3/4 ID steel pipe. Cut it in half, put a hinge on one side and weld a bolt to the other side with a tab on the other half and use a nut to hold it together (kinda like the tool has). Make two of those and put them on a vise grips or c-clamp or quick release hand clamp of some sort. I'm not too sure about the heating of it. Any electric heating element could possibly work. Perhaps an electric skillet? Those are my ideas. I'm loving the progress though!

Polyethylene Fusion Device (AKA: the 'Mini-Hack')...
 

I took my Polyethylene weld tests down to show Howard-the-Machinist this morning. When I showed him what I was able to do with a Teflon skillet on the kitchen stove, he was rightfully impressed. So impressed in fact that he volunteered to do some destructive testing to see how good the welds were. He fixed a 3/4 piece of steel rod in the bench vice and used another piece of 3/4 rod to try and tear the welded pipe apart. One weld broke pretty easily. It was a weld on which I had tried minimum heat. You could see at the torn cross-section that some of the end was still shiny and had not even melted from the heat of the skillet. The other welds were so strong that the poly pipe gave way before the weld did. Pretty impressive. But I can see just how much better it would go with a device that was along the lines of the Mini-mac. So could Howard. He showed me some online sources for 'cartridge heaters' that came in various wattages and temps. They ran about $35 each. He also said that he'd mill out a chunk of aluminum for the cause. That's no small favor. It's good to have friends in high places...

Before I left I introduced my Teflon skillet to Howard's bandsaw.


This will give me non-stick surfaces for fusing the poly pipe.

On the way back home, I stopped into Goodwill to look for resistance-heating devices I could savage to heat my home-made polyethylene fusion machine(AKA: 'Mini-Hack'). I had plenty to choose from: hair dryers, clothes irons, waffle irons and finally I found just the thing... a mini electric sandwich maker:


This device drew 600 watts, which I properly guessed ran 300 watts per side:


I got really lucky because it even has a temp regulator. Who would have guessed that sandwiches cook at the same temp as the fusion temp of polyethylene


UPDATE NOTE:
On subsequent posts you will see information volunteered by a reader with far more polyethylene welding experience than I will ever have. Owing to his suggestions, I have passed over the mini-sandwich maker's thermostat because it doesn't allow the heat to go high enough. I have instead decided to go with an electric skillet temp controller because it allows temperatures up to 450 degrees F. I have also wrestled with the fabrication of a simple-to-make answer to a device like the Mini-Mac:


Let there be no mistake, this is a really well-made piece of equipment and a professional ought to trust his work to nothing less. However the price of the Mini-Mac and heater is about $2000, so resourcefulness must prevail.


So here is my current thinking on how to de-technify a device to precisely join poly pipe for fusion welding:


In the background is the jig for centering the pipe. I built it on a large L-bracket. The smaller angle was welded in place first, before cutting out the section from the middle, thus assuring that the two sections would be in line. Since my house is small and well-insulated, it will require a pretty small loop field, so I'll be able to get by with just 3/4" pipe. The operation will require two people, one to hold the heating iron, the other to hold the pipe in place and to apply force on the pipe when the fusion temperature has been reached.In the foreground, bottom-right is the electric skillet heat control (temp control goes over 450F), in the mid-ground, middle left is the heat-cell which I made from the band-sawed Teflon skillet and the 300 watt mini-sandwich heating element. I'll post more detailed photos in a couple of days.

Still have a few mechanical problems to solve before the Mini-Hack meets the poly pipe. I ordered 200 feet of poly pipe five days ago, should arrive in about a week.

[EDIT: Here is a picture of the finished fusion tool. Lethal voltage just a fraction of an inch away from my fingers. This must get fixed before it is plugged in.]




Regards,

-AC_Hacker

P.S.: I just located some good, free industry literature. The Plastic Pipe Institute (there is such a thing) has a book called Polyethylene Pipe Handbook which can be downloaded chapter at a time here:
Handbook of PE Pipe

...of special importance is the chapter on "PE Pipe Joining Procedures" located here:
http://plasticpipe.org/pdf/chapter09.pdf

__________________________________

Yes,
That is exactly what they do.:thumbup:
Pump fromthe ground water table (to an underground storage tank)
and dump back to the water table (through a leeching field).
Several of the units in my neighborhood have had their leeching field sink. (sinking field = mucho denero) :(
We live near the ocean and the water table is just below the surface..

Sounds horrible. A lot of states only allow closed loop GSHP systems, I used to think it was too restrictive, but with what you're telling me, it makes good sense.

Somehow this all reminds me of the colossal financial mess the whole USA is embroiled in... Possibly the same players.

Regards,

-AC_Hacker

What is truly horrible is that in this city we are not allowed to have "Grey" water systems. With my wife and daughter and grandson here (plus the influx of people on the weekends) I would love to be able to make a grey water system for the toilets (like Ben's:thumbup:). I wouldn't need to wait for the toilet so I could wash clothes. I would be adding fresh water for the toilets.:p
All the water in the home has to be clean and clear, either city water or purified ground water ( for the few homes left with wells and pumps).
They allow the thermal systems because some developers lobbied for and exemption. The same developers that built this neighborhood and several others.
I believe they had some deal with the heat pump guys to get it going.
Maybe it was all with the best intentions to start.
I will give them credit for one thing though.
My neighbors with the pump and dump systems pay only a fraction of what I do for A/C in the summer.
I have 1500 sq ft and pay $200. for electric in June, July, August and Sept.
My closest neighbor with the system has 3400 sq ft and pays half that.:eek:
He is waiting for his backyard to collapse.
The house next to his went sinkhole last year and it cost them dearly. Don't ask, I don't know all the details but it has something to do with the insurance or lack of it or not enough coverage or .....whatever.

metroschultz,

I'm not sure where you live, but here in Portland, Oregon the city is being extremely slow to make progress on greywater.

In the meantime, quite a few citizens have taken charge of their own lives and are quietly and safely operating greywater systems.

-AC_Hacker

I have considered that.
Too afraid of big brother:(.

AC_Hacker does a heat transfer test...
 

Most of the sources I respect advise doing a heat transfer test to determine the rate at which heat will be transferred into the earth (for cooling) or out of the earth (for heating). This transfer rate will be the same in each direction, and will determine how much loop-field (trench or borehole) will be required to heat or cool your house. This is important because the loopfield is the most expensive part of the GSHP installation process if you are hiring it out, and is a lot of work if you are doing it yourself. So it's a good idea to get it right. Too little loop-field won't be able to supply the heating or cooling required. Too much, while not such a bad idea, means greater expense and greater work.

So I went on a google-frenzy to try to locate testing and evaluating proceedures, and after many, many hours, finally turned this up:

http://www.geokiss.com/tech-notes/TCTestingSum.pdf

So, I consider this test to be my first attempt at testing and likely to be a candidate for improvement, but this is what I did...

I had used a hand auger, meant for fence posts, and had dug to a depth of twelve feet in about 3 or 4 hours. I was going to fill the hole back in, but I decided to try to get some use out of the hole along the way. I buried a double loop of CPVC pipe I had laying about in the garage and attached some garden hose to the input an output of the loop. (see photo)

Then I filled the hole back up with the dirt that I had laboriously augered out and used water on the dirt as I went, so it would settle well.

I hadn't actually found the testing method document that I'm linking to above at the time I started testing, so I was just sort of making it up as I went along. I reasoned that if I introduced a known amount of heat-energy into the CPVC-loop, the ground would absorb the heat-energy at a rate that I suspected would decline. I further reasoned that if I monitored the temperature of the water, it would tell me something about the rate of absorption of heat by the ground. If the ground absorbed the heat at a high rate, the water temperature would be low, if it absorbed the heat energy at a lower rate, the water temperature would be higher.

So here's a sketch of my setup and a few photos:


If you read the proceedure I am using for my guide, you'll notice that the proceedure call for measuring the input and the output temperatures from the ground loop that is under test and arithmetically averaging them. I made the simplifying assumption that the water swirling around in the cooler box would physically average the temperature.

(NEXT POST: thermal transfer test data & analysis)

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AC_Hacker does a heat transfer test (part 2)...
 

So here's my test data & analysis...

Time Temp
____________
0.00<tab>54
0.133<tab>57
0.167<tab>57
0.50<tab>60
1.733<tab>70
4.00<tab>79
6.25<tab>83
7.50<tab>85
8.433<tab>86.5
14.833<tab>92
15.25<tab>92
15.517<tab>92.5
19.883<tab>96
21.00<tab>96
22.083<tab>97
24.03<tab>100
25.82<tab>100
27.65<tab>99
31.67<tab>99
40.317<tab>99
44.23<tab>101
49.60<tab>102
63.65<tab>102
68.93<tab>103
89.55<tab>106
102<tab>107
113<tab>107
123<tab>108
143<tab>109

(I had to use the "<tab>" thingies, because the real tab didn't appear correctly in this blog)

Since I don't have an automatic data logger (yet) I logged all the data by hand. The time intervals were irregular but I think that it doesn't matter so much.

The first thing I did was to put the data into a curve analysis program. The program I found is a really great shareware program called CurveExpert for Windows available here: CurveExpert 1.3: Download

I've used this program for lots of things. There are even tutorial pages available, if you need.

At any rate, it was very useful to get well done graphs as the test progressed. The program does automatic curve fits and it was interesting to see that the program selected various curves before finally settling on an MMF type curve.


From CurveFit, it's even possible to get the equation of the curve that is the best fit and to project the curve forward in time. I was interesting to predict what the temperature would be at a particular time and to check the results as they came in.

But this wasn't really getting me what I needed, which was a quantified characteristic of the earth formation in my yard. This is where the document mentioned in the previous post: TCTestingSum.pdf, came to the rescue.

I tried to follow the proceedure but wasn't able to get the same results as the author had. Either I was making a mistake, or I was using a version of Excel that was older and didn't have the exact feature he was using. But I devised a work-around and got reasonable results.

Here was my proceedure:

1) Start Excel
2) Open the data from a tab-delimited text file. This just means that the data is written in a test file and you hit the 'tab' key after the Time data, but before the Temp data. If the tab could print like this: <tab>, your data would look like this:

...
0.00<tab>54
0.133<tab>57
0.167<tab>57
...

Anyway this is a standard text format that Excel understands.

...of course you could just enter the data straight away into Excel and I could save myself some time & typing.

If you graph the data I have included, it would look like this:

See picture

Looks similar to the graph from CurveExpert.

At this point, the author of TCTestingSum.pdf was able to do a right-click on the graph curve that Excel made. Then he was able to choose "Add Trendline" and then a Logarythmic trendline, and the result, as illustrated, was a linear graph. I was not able to get these results, certainly not the graph as illustrated. So my modification to the process was to return to the spreadsheet, 'Insert' a column between the Time data and the Temp data. Then I wrote a simple formula (=ln(A1)) that took the natural log of the data in the time cell. I copied this formula down to the rest of the data cells. Then I made another graph of these data columns, "ln(Time)" and "Temp". At this point, I got a graph that resembled the illustrated results.


I then did the right-click and 'add trendline' this time I chose "Linear", since the natural log function had essentially linearized the graph. This did give me a formula with slope. Then I was able to use the rest of the proceedure as described. This all gave me a "k" value of 0.569464441. I was in turn able to use this value to calculate the total length of borehole, which would yield 12,000 BTU/hr. This calculated borehole length came to 214.23 feet. Which is reasonable, as I hear from local installers that they estimate that 12,000 BTU/hr (AKA: one Ton) borehole length to be in the range of 175 to 225 feet.

I have attached my spreadsheet for your consideration.

Some improvements:
* Get a real data logger
* Use the actual type and configuration of Polyethylene pipe I plan to use in the actual installation.
* Use a borehole that is closer to the actual location of the installation (the test borehole was within three feet of my basement, so error is to be expected)
* use the type of grout I plan to use. I'm currently planning to use "mix-111", more information available here:
Information Bridge: DOE Scientific and Technical Information - Sponsored by OSTI

I welcome your comments.

Best Regards,

-AC_Hacker

P.S.: For those who want to know more about the topic of borehole testing, I have located what might be the definitive paper on the subject:

http://epubl.luth.se/1402-1544/2002/...DT-0239-SE.pdf

P.P.S.: Here is a link to a report from a professionally done borehole test. Note the unusually high results and the speculation as to why such unusual results were obtained.:
http://www.tva.gov/commercial/TCStud...iles/Se-02.pdf

...and another done in Alabama in 2000. These are more typical results.
http://www.tva.gov/commercial/TCStud...iles/Jo-18.pdf

...and yet another done in Illinois in 2008.
http://www.midwestsustainable.com/Co...%20Example.pdf

>>>>>>>>>>>>>>>>>>>>>

I am very interested in your thread. Nice work so far too :thumbup:. You shop at Goodwill too, one of my favorite places to check , right up there with garage sales!
I have been wanting to mess around with heat pumps. I can get ahold of old ac units and dehumidifiers but have been afraid to mess with the original plumbing. It's just something I haven't had much hands-on experience with. What did you have to do to the Ac unit you converted in the picture you posted in the beginning of the thread?

How to make a heat pump out of junk...
 

jwxr7,

First the disclaimer:

I am not an HVAC technician. In fact, I am barely a hacker. Some of the things I describe may be against the law in the country or state in which you live. I do not encourage anyone to do anything that is unlawful. Additionally some HVAC equipment contains gases that are known to cause lasting damage to the atmosphere and also to cause global warming, so the manufacture of these gasses, the utilization of these gasses and the venting of these gasses into the atmosphere is also unethical and immoral. As if that were not enough, working with HVAC gasses in an enclosed space can be very dangerous because they have little or no odor and while they are not leathal of themselves, they can displace oxygen in the lungs, causing you to pass out and possibly die. Also, refrigerant gasses are under very high pressure, when they rapidly expand, can instantly cause frostbite of the fingers, and if they sprayed in your face, could cause loss of eye-sight. So, be warned, be very careful, do not work in a confined space, do not work without eye protection, do not work alone. This is serious stuff. You should familiarize yourself with proper and legal methods of handling refrigerant gasses. Act as if your life and physical intregity depend on what you do. Because my friend, it is true.

Now if you read all of the above, you should have a bit of respect for the process.

Having said all that, I have learned most everything I know about creatively re-purposing HVAC equipment, from German children. That's right I said German children. There are some fantastic blogs out there where German children describe in precise detail how they were able to take old air-conditioners and re-configure them and re-charge them with propane (aka: r-290; Barbeque Gas, etc), all so that they could super-cool the CPUs on their video games and play video games faster. I stand in awe of German children.

I would urge you to go on a Google-frenzy and search out what these kids have done.

Here are a few suggested terms:
* Extreme Systems
* Vapor Phase Change Cooling
* the term "German Children" will not be very useful

...be creative...

You're also gonna need some tools:
* Copper tubing cutter (cheap)
* A Manifold Gauge Set ($5 to $100)
* A good brazing tourch. I suggest Mapps gas, it's hotter ($35)
* Brazing rod with silver content from 10% to 40%. No, solder or silver solder is not good enough because refrigeration systems vibrate and solder does not have the physical strength. I've even heard HVAC folks use the term "solder" (like "...solder it back up."), but on inquiry, found out that they were actually referring to brazing.
* A good vacuum pump with fresh vacuum pump oil every time you use it. I got my vacuum pump for free, a friend of mine bought it off ebay, the rotor was stuck so he just gave it to me. I freed up the rotor, put fresh oil in it, let it run for about 8 hours and tested it and saw that it would pull down to about 80 microns.
* When you're serious, a micron vacuum gauge (ultra low pressures). I built my first system without a micron gauge, but I was never quite sure if I really got the vacuum low enough, or if my equipment which was all second hand was really any good. If you can borrow a micron gauge to test your equipment, that would be a big help.

...ebay and garage sales and pawn shops are good places to start looking.

Some things to keep in mind:
* go for Air-Conditioners or de-humidifiers, they're more robust than refrig compressors
* Make sure you start with a working unit. Try it out. Make sure it runs & gets cold.
* A neighborhood AC shop could extract the refrigerant for a modest cost, when you're ready to go, they might even do the recharge, if they like you and are interested in what you're doing. I have heard that it is even possible to use a spare refrig compressor for an extractor, but I have no first hand knowledge of this.
* don't 'open' the system until you are actually ready to convert it to your purposes. Refrigeration systems last a long time if their internal atmosphere is just gas & oil and NO WATER. Refrigeration oil loves watrer and will absorb and hold moisture in the air. So when you open the system the clock is ticking. Try to get it together, brazed, tested, vacuumed and re-charged ASAP.
* In my experience, a lot of the people who are in the HVAC trade are not so very happy to see new people experimenting with refrigeration. They may be blunt, maybe discouraging, might even threaten to turn you in to the HVAC police. But, if you find someone in the HVAC trade who is heplful, treat them with all the respect you can muster, they're your lifeline.
* I have noticed that there are loads of HVAC manuals, etc. floating about in the Peer-to-Peer world. If torrents won't locate anything useful, eMule just might.

Here is a link to a Danfoss manual on the basics of refrigeration, good information.

Thanks AC_Hacker, I'll do some searching and asking. One of my old friends from highschool went into HVAC and I also have a big fat HVAC text book that will be valuable.

Selecting A Likely Candidate For Building A Heat Pump
 

So if the thread is called "how to make a heat pump out of junk", I guess one of the first secrets is how to tell that the hardware you have is not really junk after all.

In this section, I'm going to describe finding an Air Conditioner Unit as a candidate for re-purposing. De-Humidifiers also make good candidates, maybe even better, but there are many more AC units in Goodwill, junk stores and garage sales.

Although you can get by without one, a device that will measure watts in realtime can be a very useful tool, not only for selecting but also for subsequent testing and evaluation. I use a model called a Kill-A-Watt link here: [http://www.p3international.com/produ...P4400-CE.html]. I actually have two and I use them all the time.

The popular misconception about non-functioning or poorly functioning AC units it that "the refrigerant leaked out". Compared to other problems, this is actually pretty unusual. The most common problem is that the coils have become blocked by debris.

So first, we need to run it.

Plug the unit in. If you have one, plug the unit in to a watt meter and the watt meter into an outlet.

Turn the unit to 'fan only' or 'cool off' or what ever it takes to just run the fan. Let it run and note the reading on the watt meter. It should be somewhere in the 30 to 80 watt range. If it is drawing more than 80 watts, then compressor is on. Turn off the compressor. Let the unit run for five minutes and feel (or measure) the air coming out. This will be our baseline temperature.


After five minutes or so, turn the unit to Maximum cool and the fan to high. Let it run for 5 to 10 minutes.

CASE #1 - Watt meter reads 300 to 1500 watts, the unit is blowing copious amounts of cold air out the front (obviously cooler than our baseline temperature). When you feel the rear coils, they should feel a bit warm to the touch.


If this is the case, you obviously have a proven winner.

CASE #2 - Watt meter reads reads between 300 and 1500 watts, the unit is not cooling very well. The rear coils feel warm-to-hot. The front coils feel cold.

Possible causes:

a) Blocked Air Flow - This is very common. The filter in the front or the coils in the front or back of the unit are blocked. This may be why the unit was tossed. If you feel the coils in the front they should feel cold, also if you feel the coils in the back, they should feel warm. If the coils or air-filter are clogged it's simple to fix with a really strong vacuum cleaner, but for our heat pump purposes, you might not use the refrigerant-to-air coils at all. Liquid-to-liquid heat exchangers are much more efficient and open up a very interesting world of experimental possibilities. In the coming posts, I will show you how to buy or make liquid-to-liquid heat exchangers.

b) The refrigerant has leaked. This is actually pretty unusual. If your unit is drawing more than 300 watts, and no cooling is happening, don't consider this unit at all. If refrigerant can get out, water can get in. Water in any amount, in the refrigerant system is bad for heat pumps.

CASE #3 - Watt meter reads 30 to 80 watts during the whole test.

This means your compressor never came on. Possible problems:

a) The compressor is dead. Compressors are well-built, hermetically sealed and tested before they ever leave the factory. This would be very unlikely to be the case.

b) The compressor starting capacitor is dead. The compressor starting cap is pretty darn reliable. This is also an unlikely case.

c) The compressor thermal safety switch has failed. These are reliable, not so likely to fail.

d) The switch on the front of the unit, or it's attached thermal sensor is bad. These can be the problem more likely than the above problems. But if these are the problem, it makes subsequent testing difficult.

e) The temperature where the AC unit is being tested is too low for the cooling cycle to start. This is can be very likely. Most of the units I have looked at need to be warmer than about 65-70 degrees F to begin to work, even at Maximum cool. You may have a winner on your hands...maybe.

So, if you can't verify that the compressor is actually working, it's really a crap-shoot. If you can get the unit for free or really, really cheap ($5), it might be worth it, but no matter how cheap, remember if it doesn't work, you still have to dispose of the carcass. Probably better to keep looking...

Other things to consider:

Look for the refrigeration identification tag. It will tell you some things like:


* Cooling capacity - This is a sales figure. It may be accurate, or it may be exaggerated. This was what was found under 'lab conditions', wherever or whatever that is.

* Input - This is about the maximum that the compressor and the fan will draw.

* Refrigerant Pressures - Write this down, you may need this info later.

* Refrigerant Type - This is the refrigerant that the unit was designed to use.

Freon - Usually R-22 & R-12. They worked great except that they destroy the ozone layer and cause global warming. A real problem. These are very expensive to obtain and in some cases illegal if you don't have a HVAC license certificate.

It is interesting to note that German Children seem prefer using Propane (AKA: R-290, Barbecue Gas, etc) because it is not damaging to the ozone layer and has zero global warming potential, and is incredibly cheap, and requires no license to obtain. It also works well with compressors designed for R-12 & R-22, as it uses the same type of lubricant (mineral oil type). It also seems to be similar enough to R-22 that it can be use without significant modification to the metering devices (more on that later). If I understand correctly, R-290 is being used as an automotive refrigerant in Australia. It is very flammable and produces water vapor and carbon dioxide (CO2) in the process.

R-134a - Currently in use. Can be obtained in auto parts store. It does not destroy the ozone layer but does cause global warming. It will be restricted and then phased out. Compressors that use R134a will not be compatible with Freons, as the compressor oil is of a different base and does not play well with mineral oil compressor lubricants or the refrigerants that use these lubricants (R-22 or R-12 and R-290). I have heard of people having success by completely replacing the lubricant with mineral oil compressor lubricant. I have not tried this. Use of this refrigerant is reported to cause cancer of the testicles in lab rats. Under certain conditions, R-134a can burn and produces deadly gasses in the process.

Regarding the size of the compressor, there's a saying that a cowboy can't have too much money, too fast a horse, or too many women. Well, what works for cowboys doesn't really work for heat pumps. if you have a large compressor, you pay more for it with every revolution. The trick is to figure the maximum BTUs or watts you will need, and design a little bit smaller. Plan to use a supplimental energy source to fill in during extreme conditions.

So I have found smaller units to be the most interesting. I have a couple of bigger compressors (about 12,000 BTU) in the cellar for future experiments, but it's the smaller ones that really fascinate me now (small house heating, water pre-heating, high efficiency refrigeration, domestic water heat recovery, etc.)

The AC unit that is in these pictures works perfectly, looks brand new, is the right size and had the fabric filter clogged with cat hair. It cost $25.

So best of luck to you finding a good unit. Let me know what you found and how much it cost...

Remember, don't open the refrigerant system until you're all prepared and ready to braze it back up. We have a way to go yet.

Very nice write up! I like the break down of refrigerants/lubricants and common AC problems. Very good info.

Very helpful info :thumbup:.

Very Cool (in more ways than one!)
 

I'm not a HVAC tech, nor do I play one on TV, but I just wanted to add my 2 (or 10) cents to the matter. Wanting to comment on this thread (and other ground-source heat/air threads) was what prompted me to reform my evil lurking ways and register.

A touch of background to start: The last year I've been helping to install a ground-source system at my place of employment. As a result, I've had some hands-on experience welding polyethylene pipe -- over 2000 welds of both butt and socket fusion.

So lets talk about the fusion: The butt fusion I was doing was in the 2-4" pipe size, with this machine <http://www.mcelroy.com/fusion/no14/>. We did socket fusion for the smaller stuff mainly because of all the tees used, I would guess, but for the scale you're talking about I wouldn't expect that you'll be needing many fittings.

Here are some things that come to mind about welding in general, and specifically about DIY welding:
- Most definitely make some sort of sliding jig to hold the pipes for heating and assembly.
- You want to keep both ends of the pipe parallel with each other.
- You want both ends of the pipe aligned with each other. like this: == not this: =---
- The ends of the pipe should cut be square (to each other, and to the heater) We had a contraption with rotating blades to square up the ends (and get to clean pipe)
- The ends of the pipes need to be cleaned (if not trimmed, but that wasn't an option for us: proper procedure was to ALWAYS trim/square (even if you've already trimmed and you just adjust the pipe in the clamps to align the ends))
- Our heater was set for about 500 deg F. Time-wise, I didn't do any butt fusion smaller than 2" (heating time was around 20 or 30 sec for 2", but not sure off the top of my head) so I don't know what to tell you about the time: experiment till you get a bead that's the right size
- There should actually be two beads - one from each pipe, and they should be about the same size (probably 1/8-1/4" for your pipe size) and even all the way round: if its a joint that counts (ie you can't cut it up to look at the cross section) the bead is how you tell if its likely to be a good weld or not.
- Practice before you do welds that'll be permanent: especially to determine your heating time. Then cut the pipe in half longways to look at the cross section of your welds: the bead should wrap around to the pipe, there should be no line: ie. if the bead wasn't there you shouldn't be able to tell where one pipe starts and the other ends. (also, before you cut, try bending the pipe back on itself to test strength)
- The evenness of your bead (or lack therof) will tell you if the end faces of the pipes were square to each other
- Let the joint sit and cool for awhile (3 min was specified) before you remove from the alignment jig to keep from putting stress on the joint until it's cooled some -- even after removal, be gentle with it until it's cool to the touch

This is getting longer than I intended, so let me leave it at that for now, and come back later. I'm definitely not trying to rain on your parade, just want to make sure you don't have to go leak hunting in a year or two. :thumbup:

Edit: I guess this doesn't address the original issue of what to use to do the welds, but it'll be important to keep in mind (IMO) as you build your alignment tool, and put it to use.

Good luck welding! I much preferred the butt fusion to the socket fusion: socket doesn't use an alignment machine. If you make yourself a good aligner you can take your time lining up and clamping, so the only thing you adjust in the heat of fusing is the pressure/distance of the pipes from each other. With socket, you have to align the pipe and fitting on the heater, then put them together and keep them aligned during cool down. Much more prone to error.

Have fun, but don't breathe the plastic smoke (anymore than you have to, at least) :D

Hugh Jim Bissel,

Thanks for the post! This is really great info.

I was thinking along the lines of your suggestions, but it is really helpful to have someone like you with your experience, to verify that I'm headed the right way.

Regarding temperature levels, all I have to go on is what I've read, and the suggested heat of the heat iron is Minimum = 400°F; Optimum = 425°F; Maximum = 450°F.

But in your experience, you had good results with 500°F?

I'm making pretty good progress with my welding tools. It looks like butt welding equipment isn't going to be so difficult, but I don't even know what a socket welder even looks like yet.
_ _ _

Thanks again, HJB for your feedback, the reason I'm doing this blog is so people can share their ideas & experience, and so we can all benefit by being more informed & capable. The way things are looking, we're really gonna need all the capability we can get.

Best Regards,

-AC_Hacker

I'll have to look when I get home to see what the recommended temp was, but it was in the 450-500 range. From issues we had with the socket iron it seemed the temperature could vary a good bit as long as the time was adjusted: ie higher temperature & shorter time within limits (that was the issue we had: I think the thermostat died, so the heater was always on and went up to like 650+.:p we replaced it as soon as we could, but as I recall we still could do the welds, just had to drop the time down)

That 425 should be fine. Your time will be a bit longer, but as long as it's a good bit above melting temperature (which sounded like it was about 300 from your previous posts) you should be fine.:thumbup:

There's not much to a socket weld kit: the iron has "socket faces" bolted to it: basically a female end the pipe goes in, and a male end that goes in the socket joint. the only other special equipment is "cold rings" basically vise grips with a half circle the size of the pipe welded to each jaw: this is basically a depth stop on the pipe to keep it from going too far into the face on the iron or into the joint. The overall idea is similar to gluing PVC together, the differences are that instead of gluing, you put both parts on the iron for the specified time, then pull them off the iron and push them together. The theory sounds easy, but when you're trying to get a 2" fitting off the iron and onto the pipe, two people or something solid to push against are mandatory!

In your case, you're probably just going up and down each borehole in series: therefore you won't need any tees, whereas all our wells were in parallel (since each was 250' down), so each well teed off a horizontal line. Loooots of fittings. My friend and I drove each other crazy welding endless fittings in the bottom of 4' trenches in the heat of Texas summer! :eek: Its a miracle I'm still sane (though that could have been debated even before that ordeal:D)

Some possibilities?
 

A.C. and all,

A few top of the head comments: I'm interested and have done a little investigation. AC, you have, of course, identified two of the main problems, capability to drill through hard rock, and fusion welding of the polyethlene tubing, to be used in either vertical wells or in trenche installation.

Hard rock drilling might be the more difficult problem, not readily adaptable as a DIY project. Requires an equipment size of something like a Bobcat. I have one, and got an estimate of around $10k to convert it. Seems that for small lot size, around half acre here in Maryland, you would need vertical drilling. Lot sizes are too small for the alternate trench system. You estimate in the Oregon area that two 200-ft wells would be required. I assume, alternatively, four 50-ft wells. Putting these in line with a simple header arrangement would allow the wells to be easily connected together.

You mention another problem, that of fusion welding. Perhaps this would not be such a difficult problem with 50-ft wells, where the piping could easily be lifted out and replaced if necessary, allowing, I would suppose, joining sections of small diameter polyethlene tubing using stainless steel clamps (it was, for instance, not very difficult, in a 500-ft water well, to replaced the pvc lines).

Doing a google search you come up with different kinds of equipment for doing fusion welds. I presume one would use butt welding. Note also that Oklahoma State University has an ongoing ground coupled heat pump installation program where fusion welding is one of the topics covered. Several of these classes are listed below:

I have need for two such installations, one at my residence which is situated on a half acre and another at a farmhouse I own where there is sufficient ground area for a trench type. Also, considering adapting my Bobcat (since I have one) to do vertical drilling to 50-ft. And, I imagine the adaptation could be done for less than the $10k price that somebody quoted me) And at that 50-ft depth, as indicated, I would assume maintenance, in event of leaks, would present no particular problems with the more conventional methods of pipe connection. Aside from the ground coupling technology, the rest of the installation, I believe, could be handled by most any qualified HVAC installer. Am I right?

If interested, please comment.

Glenn Ellis
glenne1949@ol.com



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Post from Glenn...
 

(This reply actually was posted by Glenn in a Yahoo group, where I cross-post portions of this blog. I'm copying it here as it is of interest. -AC_Hacker)

A.C. and all,

A few top of the head comments:? I'm interested and have done a little investigation. ? AC, you have, of course, identified two of the main problems, capability to drill through hard rock, and fusion welding of the polyethlene tubing, to be used in either vertical wells or in trenche installation. ?

Hard rock drilling might be the more difficult problem, not readily adaptable as a DIY project.?? Requires an equipment size of something like a Bobcat.? I have one, and got an estimate of around $10k to convert it.? Seems that for small lot size, around half acre here in Maryland, you would need vertical drilling.? Lot sizes are too small for the alternate trench system.? You estimate in the Oregon area that two 200-ft wells would be required.? I assume, alternatively, four 50-ft wells.? Putting these in line with a simple header arrangement would allow the wells to be easily connected together.?

You mention another problem, that of fusion welding.? Perhaps this would not be such a difficult problem with 50-ft wells, where the piping could easily be lifted out and replaced if necessary, allowing, I would suppose, joining sections of small diameter polyethlene tubing using stainless steel clamps? (it was, for instance, not very difficult, in a 500-ft water well, to replaced the pvc lines).

Doing a google search you come up with different kinds of equipment for doing fusion welds.? I presume one would use butt welding. Note also that Oklahoma State University? has an ongoing ground coupled heat pump installation program where fusion welding is one of the topics covered.?? Several of these classes are listed below:

I have need for two such installations, one at my residence which is situated on a half acre and another at a farmhouse I own where there is sufficient ground area for a trench type.? Also, considering adapting my Bobcat (since I have one) to do vertical drilling to 50-ft.? And, I imagine the adaptation could be done for less than the $10k price that somebody quoted me)? And at that 50-ft depth, as indicated, I would assume maintenance, in event of leaks, would present no particular problems with the more conventional methods of pipe connection.? Aside from the ground coupling technology, the rest of the installation, I believe, could be handled by most any qualified HVAC installer.? Am I right??

If interested, please comment.

Glenn Ellis
glenne1949@ol. com

So I've looked, and even though I saw that booklet just a few weeks ago when looking for something else, now that I'm looking for it, it's nowhere to be found! I did find this website though which has the temp from 400-450, so you're probably better off sticking with that. It also has more info and pictures about bead sizing, what good welds should look like, and a good step-by-step fusion procedure.

It doesn't have heat times though, but you should be able to figure that out easily enough once you start test-welding: for 3/4" pipe 30 sec is probably way overkill: keep making welds and adjusting the time by a few seconds until the bead is close to the right size per that website. When you get close, you might go in each direction by a second until you know min and max time (per bead size), then use the middle of that range for the welds that count. (the range will change by a few seconds depending on the weather conditions: temperature of the pipe and if there's a lot of wind).

Caught me while I was typing:D

We did the majority of our project in-house, and before I was hired the idea was tossed around of buying/renting a drilling rig, but they ended up having professionals come in. Would have been fun to learn, but I could see how it would have been rather dangerous if we didn't know what we were doing. Once they got going, they were knocking out each 250' hole in under an hour - through solid limestone. Also, they were able to blow the drillings out with air instead of having to use mud, so I'm sure that sped the process up as well.

The numbers don't add up, if you need 2 200' wells than 2 x 200 = 8 x 50 or if you need 1, than 1 x 200 = 4 x 50

But, yes, once the math is right, one big well could be divided into smaller wells: thats why we were able to do 230 wells at 250' down instead of having to do one 57,500' well!:eek: (and have to put 6" pipe down it instead of the 1" we used!)


We buried our horizontal piping 4 ft down to keep it out of the effects of surface temperature. From my point of view, I'd much rather spend even twice the time once and do it right, rather than have to repair many times (especially if you consider selling the house in the lifetime of the piping (50-100+ yrs!). If you're running all your wells in series, you shouldn't need many joints at all: a U at the bottom of each well, and then a coupling between the ends of each coil of pipe: its best to leave a loop at the top of each well to accommodate expansion and contraction so you don't need elbows there.

Response to Glenn...
 

Glenn,

Thank you for your interest...

> You estimate in the Oregon area that two 200-ft wells would be
> required.? I assume, alternatively, four 50-ft wells.? Putting these
> in line with a simple header arrangement would allow the wells to
> be easily connected together.?

Thanks for spotting my error...

In western Oregon where I live:

1 Ton (12,000BTU/jhr) = 200 ft borehole
(or)
2 each 100 ft boreholes
(or)
4 each 50 ft boreholes
(etc)

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
[UPDATE: When I first wrote this, I thought it was correct, but experience has shown that the idea needs modification. The deeper you go, the less seasonal temperature fluctuations will affect the temperature of the earth. The opposite is also true, and the shallower, the more seasonal temperature shifts will affect the temperature of the earth. The following picture illustrates this principle:


In my case, I ended up drilling 16 holes, with an average depth of 17 feet each. The top of each borehole was 2 feet under the surface of the earth, so the effective depth of each borehole was 15 feet. So my total borehole length was 16 X 15 = 240 feet. But since this was close to the surface of the earth, it was certainly not as effective as a 240 foot deep hole. During the winter of 2010-2011, I ran a very small heat pump 24 hours a day. I was able to extract useful heat but I was not able to log so much useful data.

Nonetheless, it is clear to me that the idea works. It is also clear to me that drilling shallow holes, as I did, will require that more holes must be drilled.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

In the part of Oregon where I live, temperature swings are not as large as they are in many other parts of the country, so the heating and cooling load is generally less than in many other places. The information I have gotten from quite a few local sources is that the rule of thumb, when estimating the amount of borehole required here is 200 ft. of borehole for every Ton (12,000 BTU/hr) of cooling/heating required. Because my house is small and well insulated, my design heat load is somewhat less than 12,000 BTU/hr. I have found that respectful conversation with GSHP installers and water well drillers who also drill wells for GSHP installations (most do), will readily yield this rule-of-thumb information for your particular area. Also, I show how you can experimentally derive this information for your own specific location yourself at this URL: http://ecorenovator.org/forum/introd...nifesto-2.html. The blog posting also cites a document that I took as the source for my test. You would do well to read and understand that document before you do your own test.

One aspect of my test that may appear as a source of error is that the test hole I used was only 12 ft. deep. It would likely give you misleading results to only use a 12 ft. test hole in your location. As the source document points out, your test hole should be as close in size and construction detail as the actual boreholes you plan to use. In my case however, I live in a very small house, which I have re-insulated very well, and I live in a relatively mild climate, and most importantly I am actually planning to use many 12 to 15 foot deep boreholes. So in fact, the borehole I used does resemble the boreholes as they will finally be constructed.

The rest of your thinking is correct regarding using a branching loop field.

> ...where the piping could easily be lifted out and replaced if necessary...

Generally, the piping is designed to go in the ground and to stay in the ground.

> ...considering adapting my Bobcat (since I have one) to do vertical
> drilling to 50-ft.? And, I imagine the adaptation could be done for
> less than the $10k price that somebody quoted me)?

This sounds great! I wish you the best on this one. Please post photos as this progresses. I guarantee that you will have considerable respect for loop field installers when your own loop field is complete and working!

But if you're actually thinking about doing this yourself, you need to give yourself the benefit of all the information you can lay your ambitious hands on. So if you're expecting to save the better part of $10,000 you'd be well advised to spend $100 and go straight to the source of information: Publications | Manuals. In fact, they offer a ground source installer course at a pretty reasonable cost. My advise is to go for it!

> I would assume maintenance, in event of leaks, would present no
> particular problems with the more conventional methods of
> pipe connection.?

I think that there's probably a good reason why most states require fusion welding and pressure testing of GSHP loop fields. I'm not saying that you're incorrect, but I'd advise you to do more research.

There are also other issues such as being able to achieving flow turbulence and minimizing friction losses, etc. that might not be apparent at this stage of your thinking.


> ...the rest of the installation...could be handled by most any qualified
> HVAC installer.? Am I right??

There's probably less cost and drama in the HVAC portion of the project, but your best bet would be to hire someone with successful experience in GSHP installation.

But overall, you have correctly identified that the majority of the cost & work is in the loop-field.

But Glenn, if you are going to go to this length, I would advise you to also consider abandoning forced air and going with hydronic radiant floor heating. Not 'staple up', not the panels that go on top of the floor, but what's known as 'wet system' where the PEX is embedded in a 1.5 inch layer of concrete. When properly done, this offers substantial advantages over forced air, as the heat pump is not called on to raise the working fluid (water) to as high a temperature.


Hope this has answered your questions.

Regards,

AC_Hacker

HJB's excellent info on pipe fusion...
 

I'm not sure if this stuff is getting out of sequence or not, but HJB (AKA: Hugh Jim Bissel) shared a great link to information on pipe fusion technique here: (Polypipe - Heat Fusion and Joining Intro). It's the best and clearest info I have seen and I didn't want it to get lost in the shuffle.

Best Regards,

-AC_Hacker

Driven Pipe Loop Field...
 

(* Interesting post from another group *)

> From: "Paul Phillips" <cptrdbrd@yahoo.com>
> To: wastewatts@yahoogroups.com
>
> Hi all
> I have been tossing around the geothermal idea for a some years
> and I am getting closer to starting work. wile doing some research
> on well drilling, I came across "driven well" this is where you use a
> special made point that threads on the end of galvanized pipe and
> you drive it into the ground up to 100-150 ft. they usually have slots
> or holes to let water into the pipe at the bottom.
> My thought is not to have the holes in the bottom. all so then you
> made a manifold on the top to allow you to make a sort of tube in tube
> heat exchanger, you could run say 3/4" pex with 1/4" of closed cell foam
> down the middle. this would give you a closed loop design. if you could
> do multiples of this like a spider design to 50-100" you may not have to
> drill expensive wells.
>
> Paul

Paul,

I have a portion of a manual called "Drilling Methods for shallow geothermal installations", that was written by a Swedish Geology Prof named Olof Anderson, date unknown.

From studies conducted in the early 1980's, they cite rammed (AKA: driven) co-axial (AKA: tube-in-tube) steel tubes as one of the possible methods for GSHP installation. Corrosion seems to be a problem. Regular steel has a mass loss of 2.15% per year and is estimated to be good for 32 years, copper has a mass loss of 1.74% per year with an estimated life of 40 years. Stainless steel appears to have negligible mass loss and is expensive.

* please see attached scans *

Regards,

-AC_Hacker

How Refrigeration Works...
 

Before we open up our Air Conditioner, it would be a good idea to consider how the thing works, so that we will have some appreciation for the stuff we're going to be looking at and in some cases modifying.

EDIT: 1-28-2012
It is useful to get info from several sources. Here in an excellent explanation of how refrigeration works from a seasoned HVAC guy, originally posted here.
END OF EDIT: 1-28-2012

I have talked to lots of people, modern people, who just can't understand why I think I can use a refrigeration compressor (actually Air Conditioner compressor), which they associate with cold, and to bury pipes in the ground, which they also associate with cold, and reasonably expect that this procedure will result in making my house warm. I've tried to use refrigerators as an example, which they associate with cold, to explain the process, and I usually get to see people with pitying eyes stare at me, wondering how an otherwise reasonable person could be so misled.

But I'll try again here...

First off, what is heat?

We have an intuitive notion that heat is what we feel when we touch something that is warmer than our hand. And the opposite, cold is what we feel when we touch something that is less warm than our hand.

If we look really deeply into the question of what heat is, we will find out that heat is actually a manifestation of energetic movement of molecules. The greater the movement, the greater the heat. But something what might feel cold to us, like cold water, in fact has this energetic molecular movement that results in heat. It may have less energetic movement than warm water, but it still has energetic movement.

In fact, any material will have this energetic movement that we will call heat until the very cold temperature of −459.67°F. SO compared to that the temperature of the ground is pretty warm.

Let's look at this refrigeration diagram:


This is a simplified diagram of the components in the refrigeration cycle of our air conditioner. I have taken the liberty of adding the light green line to the diagram from the compressor across to the "valve" (AKA: metering device, expansion valve, capillary tubing, etc.). This green line marks the boundary between the high pressure side (AKA: high side, pressure side, hot side) which is on the right side of our diagram, and the low pressure side (AKA: low side, suction side, cold side) which is on the left side of our diagram.

This whole refrigerant circuit is hermetically sealed from atmospheric pressure, it is in it's own special refrigeration world, there's no water in there, there's no dirt in there, just refrigerant and some lubricant. Before we power up the compressor, the pressure of the refrigerant gas/liquid on both sides of the diagram is under greater than atmospheric pressure (probably in the range of 50 to 100 psi), but it is equalized on both sides. Neither side is hotter or colder than the other.

When we put power to the unit, we intentionally create an imbalance and we exploit the changes that result from this imbalance.

There may be a bit of a time delay, but very soon, the compressor starts working and it begins discharging refrigerant gasses out of the compressor and sending them through the high-pressure side tubing. They travel through this tubing until they get to the "valve" where their progress is slowed almost to a standstill. But the compressor continues pumping away and the gasses back up and the pressure increases and so does the heat of the gases and at some point, the gasses are under so much pressure that they almost begin to turn into a liquid, a hot liquid. This hot, highly pressurized gas then flows through an assembly which allows for the removal of some of the heat. This assembly is called the condenser. When enough heat is removed, the hot gasses in the condenser actually do turn into liquid, and in so doing they yield up an accellerated amount of heat. (* This gives us a thermal imbalance that we can exploit to make our heat pump. This thermal imbalance is where the heat that we desire to heat our house or our water is extracted. But where does it come from? Read on...) The hot liquid then moves along to the expansion valve.

The expansion valve in small air conditioners usually takes the form of what is known as a 'capillary tube', or 'cap tube' in the trade. This cap tube uses the friction created by both a very small diameter, and a relatively long length to consistently restrain the flow of liquid refrigerant in the circuit. The cap tube is reliable, fairly consistent and cheap. The cap-tube is designed to work with our compressor, so we'll want to salvage it when we begin major surgery.

Loook at the second picture:


So the liquid flows in a restrained manner through the cap tube, which may be 4 to 8 leet in length, all coiled up, inside our air conditioner. Then something strange and wonderful happens...

While the compressor has been feverishly creating a high-pressure condition on the right side of our diagram, it has also been feverishly creating a low-pressure condition on the other side of the diagram.

As the refrigerant travels through the cap tube, at some point very near the exit of the cap tube (less than an inch) it enters the low pressure created by the compressor. When this liquid enters the low pressure area, the imbalance of pressures force the liquid to instantly flash into vapor. (* This instantaneous flashing into vapor causes an instantaneous drop of temperature. Here we have another thermal imbalance which we will also exploit in our heat pump. This extraordinary imbalance, cold in this case creates a thermal "vacuum" into which heat from surrounding earth or water will flow. *)

Look at the third picture:


I'm also posting another diagram of a refrigeration circuit. It's really a great illustration, and you should be able now to understand just what's going on in this picture.


As an addition, here are some documents that also introduce the principles of refrigeration:

• FUNDAMENTALS OF REFRIGERATION PART 1.pdf
• FUNDAMENTALS OF REFRIGERATION PART 2.pdf
• FUNDAMENTALS OF REFRIGERATION PART 3.pdf
• FUNDAMENTALS OF REFRIGERATION PART 4.pdf
• FUNDAMENTALS OF REFRIGERATION PART 5.pdf
• FUNDAMENTALS OF REFRIGERATION PART 6.pdf

And here is a clear, plain-english description of the refrigeration process.

And here is an information packed index page leading on to amazing projects by people determined to wring extra performance out of their computers by using refrigeration technology to cool down over-clocked CPUs.

Best Regards,

-AC_Hacker

We look under the hood to see what's going on...
 

OK, sorry to take so long... life is a multi-threaded process.

So now we're going to open up the case, but we are not yet going to open up the refrigerant system.

Safety first, make sure you have the Unit unplugged. Locate the plug before you start using the screw-driver.


(NOTE: when I take something apart anymore, I keep my digi-camera close at hand and take photos at every step. This way if I forget exactly how it goes back together, I can refer to my photos.)

Most AC units are built very much alike. If you have a different model, even a different brand, you should be able to follow right along with the text & photos here.

SAFETY NOTE FROM bma1984:
Remove all of the sheet metal screws that look like they might be holding the beast together. When you think you have them all, give the sheet metal & plastic case pieces some gentle tugs to take it off. You might want to re-use all of or maybe part of the case, so treat the sheet metal with care and save the screws all together where you won't lose anything.

Here's what I ended up with:


one of the first things we should look for is the schematic. It will be on a piece of paper stuck inside, or glued to a panel in side, but they all have them and they have useful information.


A couple of things to note in the schematic... On my schematic, in the lower central area of this schematic, coming off of the BR wire of the compressor, there's a symbol labeled "OLP". This indicates the Over-Load Protector, and is a round bi-metallic module that is under the plastic cover on top of the compressor. It serves the purpose of preventing the compressor from overheating. If a maximum temperature threshold is reached, a bi-metallic
spring will interrupt the flow of current to the compressor. We'll look at it later. Also of interest is the "capacitor". symbol on the lower right of the schematic. The compressor and fan motor each use a starting capacitor to nudge them into starting. In most of the air conditioners I have seen, there is only one capacitor case, with two capacitors inside, a smaller one for the fan and a larger one for the compressor. If we decide that we don't want to use the fan, we can still use the same capacitor, and just ignore the fan side.

Next is the compressor, it's the main reason I bought this AC unit. It accounts for most of the weight and cost of any air conditioner.


There are two copper tubes that come from the compressor. One comes out of the top. This is the high pressure discharge from the compressor. the other tube usually goes in the side, near the bottom of the compressor. This is the low pressure (AKA: suction side) tube. We can expect that the high pressure side will become warm when the compressor is running, we can also expect that the low pressure side will be cooler to the touch, when running.

On the side of my compressor is a number in large-size type that reads, "qa075cde". If I Google that number (qa075cde - Google Search) , I eventually find out that my compressor is made by LG and that it is between 1/3 and 1/2hp with a displacement of about 7.5cc/rev. Most room a/c's use r22 which usually means it has mineral oil or alkybenzene.

(* I also find out that there are several hacker forums where people more knowledgeable than I am, are re-purposing AC units for all sorts of things. *)

While I am looking around the compressor, I also see a coil of thin copper tubing. This is called the "cap tube", short for capillary tube, which is the air conditioner's refrigerant metering device.

This cap tube is carefully sized (length and diameter) to the compressor and the refrigerant type. It is possible to size my own cap tube, but if I'm careful, I will be able to use this one. As previously stated, R-22 has characteristics that are very similar to R-290.

Also of interest, but perhaps a little hard to see, is that the compressor is sitting loosely on little rubber vibration absorbers. These are also matched to the compressor, so if possible I will keep them too.

This blog software will not let me select more pictures in one 'reply', so I will continue this section over into another 'reply'.


Regards,

-AC_Hacker

We look under the hood to see what's going on... (continue #1)
 

Let's take a look at the top of the compressor...


There's a plastic cap, held in place by a single nut. the power wires and the OLP (over load protector) are under this. Take a moment to notice the letters printed at the edge of the cap, we'll see them again. If the AC unit is unplugged, let's remove the nut for a quick look inside.


Here we see various colored wires that power the compressor. We also see the OLP device which will press against the top of the compressor, when the cap & nut are in place.

If we compare what we are looking at to the schemetic, we will see this...


I've drawn in a light green line between the OLP on the schematic and the actual OLP device.

I have also drawn in a yellow line between schematic's compressor connections and the real thing. Take a few moments to familiarize yourself with the connections, the wire colors, the letter symbols on the schematic and the letter symbols on the actual compressor. Do they all agree?

Now put the cap and the little washer and the nut back on the compressor. The nut should be snug but not really tight.

Next, let's look at the rear side of the AC unit. This is the side that will be outside the window. On a day when the AC is running, this radiator will be exhausting the hot air from the room (and the heat generated by the compressor). The name of this radiator (AKA: air-to-air heat exchanger) is the 'condenser coil'.

I have drawn a light-blue circle to indicate and area where the aluminum fins got 'mooshed'. If I want to use this condenser, I can straighten out the fins by hand. Small combs are available to help with this job. If the air is not able to flow freely past this part of the condenser, it can't dump it's heat.


I have also drawn in a yellow circle around another detail... This piece of bent-over tubing is where the refrigerant was put into the unit at the factory. If this looks a bit funky, it's because in mass production, every effort is made to shave cost from the millions of units that are produced. If a real service valve was here, the price to make this AC unit would be about a dollar more. When millions of units are produced, it adds up to real money. If I decide to build a heat pumpout of this unit, I will need to put in a real service valve (AKA: Schrader Valve) here, and I will put in another one on the 'low-side' of the compressor.


THe Schrader valve comes in various configurations, the most common has the same thread as a 1/4 inch flare fitting, and the valve core is an automobile valve-stem core. be sure that when you braze on a Shrader valve, that you first remove the valve core before you apply heat, and wait until the brazed area is cool to the touch to re-install the valve core, else the valve core seals will melt, stink and fail to ever work again, as I found out.

I have reached the end of my picture quota, so...

We look under the hood to see what's going on... (continue #2)
 

Lets take a closer look at the flow of refrigerant...


...here we see the discharge tube coming from the top of the compressor and down through a 'U-shaped' tube, then splitting into two paths and entering into the condenser coil. I have drawn the directional arrow in RED to indicate that the refrigerant is hot at this point, both because it has been compressed, and because it has picked up heat from the compressor. The U-shaped tube is there partly to help spread out the vibrational stress over a longer distance, to prevent pre-mature failure of the copper tube. The splitting of the refrigerant paths is to raise the efficiency of the condenser coil to expose more high-pressure gas to more air-cooled copper tubing.

At the bottom of the condenser coil, the two refrigerant paths converge into one path and enter the cap tube. I have drawn the directional arrow in MAGENTA to indicate that the trip through the condenser has removed heat from the refrigerant.

Then the refrigerant flows through the cap-tube and then enters the 'suction side' (AKA: low-side) of the refrigeration cycle.


I have shown the path of the refrigerant through the cap-tube in MAGENTA. I have drawn the circle and arrow in BLUE because this is the point of expansion of the refrigerant, this is where the refrigerant flashes from warmish liquid to very cold gas. When we run the AC unit, we can expect to find frost forming at this point first, and then spread along the tube tward the evaporator tube.

here's another detail of the tubing near the condenser:


I have drawn the flow arrow to the condenser in BLUE to indicate that it is really cold, and the flow arrow from the condenser in LIGHT BLUE to indicate that some of the cold has been lost, actually heat has been gained.

Also note in the background of this picture, the silver cylinder. This is the starting cap for both the fan and the compressor.

Next is a full shot of the condenser.


Note the temperature sensor at the bottom of the evaporator coil. It is there to sense the temperature of the exiting room-air and also to sense if the evaporator gets really frosty. It will shut down the AC unit to allow the frost to melt. Then after a few minutes (about 5 minutes) the unit will start up again. If we are clever, we might be able to reuse this sensor for our newly re-purposed machine.

Next photo is looking down next to the top of the compressor and shows the return of the refrigerant to the compressor.


The refrigerant has lost some of it's cold to (gained some heat from) the room air during it's trip through the evaporator coil, but after it passes through the filter (which also contains desiccant to remove any water that may have been inside at the time of manufacture), and enters the compressor, it is definitely cooler than the compressor. The designers count on this to help keep the compressor cool.

We look under the hood to see what's going on... (conclusion)
 

Let's take advantage of the fact that the cover is off and watch what the unit does under power...

Make sure that the cover is back on the compressor, and that no screwdrivers or wrenches are in or on the AC unit. If you have a watt-meter, this might be a useful time to measure the power consumption of the unit.

I let mine run for a couple of hours and here's what it looks like.


If we look at the evaporator end of the cap-tube, we should see frost forming.


After it has run awhile, the compressor's heat begins to build and we see that the frost on the evaporator line has decreases a bit.


I have included here an interesting chart that shows various refrigerants, and when they were discovered.


There's more to learn about the innards of an AC unit, but this should do it for now.

This is the conclusion of "We look under the hood to see what's going on".

I hope this has been useful for you, and has not only given you a bit of knowledge but has fortified your gumption to continue on with some interesting and useful AC hacking.

Best Regards,

-AC_Hacker