The Homemade Heat Pump Manifesto

[AC_Hacker]

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.

(NEXT POST: Selecting a likely candidate for building a heat pump.)

[jwxr7]

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.

[AC_Hacker]

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.

AC_fan-only

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.

AC_fan+compressor

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:

AC_the-tag

* 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.

(NEXT POST: We look under the hood to see what's going on...)

[Daox]

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

[jwxr7]

Very helpful info .

[Hugh Jim Bissel]

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.

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)

[AC_Hacker]

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

[Hugh Jim Bissel]

Originally Posted by AC_Hacker

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'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+. 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.

Originally Posted by AC_Hacker

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.

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! Its a miracle I'm still sane (though that could have been debated even before that ordeal)

[glenne1949]

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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[AC_Hacker]

(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