The Homemade Heat Pump Manifesto

[NiHaoMike]

Originally Posted by AC_Hacker

Here is one of the most informative sources of refrigeration hacking I have ever come across:

Phase Change Building Guide - XtremeSystems Forums

It has been considerably expanded since I first discovered it.

I'd advise you to read the whole thing, and when you are through, go back and read the whole thing again. This is an absolute gold mine.

Make note of the tools required, and start nailing down access to the stuff you're gonna need. You may have friends or relatives who have some of these tools to lend or give or sell cheap.

Sometimes Chinese tools can get you by:

Harbor Freight Tools

(* hint: don't even consider the 'Air Vacuum Pump', not good enough *)

Ebay is a good source of refrigeration servicing equipment. Here's a good starting point:

eBay ? HVAC Tools, HVAC Meter and HVAC Gauge items on eBay.com. Find IT on eBay.

Also, sadly, due to the horrible economic situation, there are HVAC techs who are forced to pawn their working tools. So check out the pawn shops, but don't go there until you have studied ebay, to familiarize yourself with what the going prices are. The pawn shop owners do this as a matter of course. Prepared yourself for some lively bargaining.

Do they have garage and estate sales where you live? Another good source.

And lastly, I'd advise you to read well the section on brazing. Then get some copper tubing and a MAPS tourch (Propane will work, only slower) and some silver brazing rod, some brazing flux, and start practicing. The infra-red energy of brazing isn't so good for your eyes, so don't neglect eye protection. An old welder told me that even plastic-lens sun glasses will offer protection, but you should double check that.

Regarding brazing, the tools and materials aren't so expensive and you can get some practice right away. I tried all kinds of brazing rod for this and didn't have any luck until I tried 40% silver rod. The silver content makes it flow really nicely. This stuff isn't cheap but you can get "job packs" with about 5 or 6 sticks.

The temperature at which the brazing rod flows well isn't very far away from the temperature at which copper slumps, so there is some skill there that you will have to develop. You'll want to have this skill on tap and well-developed before you hack into your AC unit. Resign yourself to the prospect that you may have a half dozen failures before you learn how to get one really pretty brazed joint.

You may even want to tackle a homemade brazed tub-in-tube heat exchanger.

Be patient, be persistent, you can do this.

Hope this helps...

I'll share my experience with refrigeration relating to a research project I did about refrigerating CPUs for higher performance.

Before doing anything else, research. It is very important if you want to assemble the device properly and have it work correctly on the first try. In particular, the TXV, as simple as it may seem, is one of the most difficult parts to understand. Make friends with a refrigeration engineer if you can. (In my case, the "fridge girl" I became friends with really helped me buy stuff, and not just by helping me select the right parts, as you'll see later.)

Then obtain the tools needed for refrigeration work. Some of the most common essentials are: a gauge set, vacuum pump, multimeter with thermal probe, MAPP or acetylene torch, and refrigerant can tap (if using refrigerant cans without nipples).

The gauge set is the most frequently used tool in refrigeration work. It mostly comes in 2 varieties - 2 valve and 4 valve. It is cheaper to convert a 2 valve gauge set into a 4 valve by adding a splitter and valves, although professionals may find that too clumsy. It's fine for DIY work, though. Expect to pay about $50 for a good entry level gauge set.

A vacuum pump is used to remove air and moisture from refrigeration plumbing. (Air and especially moisture can cause internal corrosion.) As previously mentioned, "jet" vacuum pumps are used for vacuum packing and are more or less worthless for refrigeration. I made my own vacuum pump from an old freezer compressor by replacing the oil with vacuum pump oil.

Unless you're going to use all flare connections (which have their own problems), you'll need a torch to "weld" (really more like high temperature soldering) the connections together. You'll need at least MAPP since propane does not get hot enough to make reliable connections. Acetylene is even hotter but much more expensive and overkill for our uses. You'll need welding rods made just for refrigeration since regular plumbing solder will crack and leak under pressure cycling. It will take a lot of practice to get it right. In my experience, the temperature is about right once the pipe starts glowing red.

Then you'll need parts and supplies. A cheap way to obtain many refrigeration parts is to buy an old refrigerator, freezer, A/C, or dehumidifier from Craigslist. (In my area, I have seen a listing for an old dehumidifier for $10. I'm going to make it into a small heat pump clothes dryer if it is still available.) You'll need to locate a refrigeration parts store in your area to buy service nipples, fittings, pipe, and some other parts and tools. Some stores are reluctant to sell to individuals (which makes no sense since they're losing a potential customer), so be prepared to locate another store to actually buy stuff. (I had a real problem buying a TXV for my CPU cooling project since only one store in my area had the right one available and they did not want to sell to me. The solution was to have my friend buy the part, which I then buy from her. Apparently, they could not resist selling supplies to a pretty customer!)

When it's time to start assembly, the parts to install last are the filter drier and (if prefilled with oil) the compressor. They will be degraded by exposure to air, so make all the other connections, then start pulling a vacuum after finishing the last connection ASAP. If you're reusing an old compressor, tape shut the pipes immediately after removing it and/or change the oil in it. If you're changing the oil, do not add the new oil until after the vacuum is pulled and then purged and leak tested with an inert gas. (Helium for inflating balloons works well, as does CO2 or nitrogen.)

If the first vacuum and leak check is fine, continue by releasing the pressure and pulling another vacuum for about 3-4 hours. Then purge with an inert gas to about 5 PSI of pressure and start another vacuum of about 3-4 hours. Repeat the purge and vacuum process again, then fill the system with refrigerant up to about 40PSI. Then start the system and continue filling until the sight glass fills up (if there is one) or until subcooling or superheat reaches the proper range.

[AC_Hacker]

NiHaoMike,

Great info...

I made my own vacuum pump from an old freezer compressor by replacing the oil with vacuum pump oil.

Can you say a bit more about using a freezer compressor as a vacuum pump?

What kind of vacuum levels were you able to pull?

I like the idea of a DIY vacuum pump!

Regards,

-AC_Hacker

[NiHaoMike]

Originally Posted by AC_Hacker

NiHaoMike,

Great info...



Can you say a bit more about using a freezer compressor as a vacuum pump?

What kind of vacuum levels were you able to pull?

I like the idea of a DIY vacuum pump!

Regards,

-AC_Hacker

Sam's Laser FAQ - Vacuum Technology for Home-Built Gas Lasers
I don't have a gauge that can precisely measure the vacuum level, but it pulls as low as the gauge set will measure. I estimate 1 Torr or so since it is a rotary compressor.

[cdig]

I have an old well on my property that we just recently decomissioned in favor of town water. In the geo_thermal manual you provided at the beginning of this thread there's a section on 'standing column well ground heat exchanger' ... thoughts?

How deep would the well have to be in order to work? The ground water is pretty high around here, so I don't think the well is very deep, but if I can use it instead of drilling a bunch of holes in my yard, why not right?

[AC_Hacker]

Originally Posted by cdig

I have an old well on my property that we just recently decomissioned in favor of town water. In the geo_thermal manual you provided at the beginning of this thread there's a section on 'standing column well ground heat exchanger' ... thoughts?

How deep would the well have to be in order to work? The ground water is pretty high around here, so I don't think the well is very deep, but if I can use it instead of drilling a bunch of holes in my yard, why not right?

The easiest & cheapest way is usually the best way.

However, in my explorations of alternative energy strategies, I am continually confronted by just what a tremendous amount of energy I use habitually without being aware of it. The alternative energy strategies usually involve using energy densities much lower than what is available with fossil fuels.

I got a taste of this when I hooked up my first experimental 400 watt heat pump to a 10 foot ground loop to see how much heat I could extract. Short story is that the loop froze solid in about 25 minutes.

There was heat in that loop, but my little 400 watt compressor was drawing the heat out at a much faster rate than the 10 foot loop could supply it. The ground gives up its heat, but gives up its heat very slowly.

In a few days, I should have the last of my loops completed and I'll have 240 feet of loop for the heat pump to draw heat from. I'm pretty confidant that my little heat pump won't be able to extract heat as fast as the ground can supply it.

cdig, I'm not sure where you live, but some things you'll need to know are:

1. What is the average ground temperature where you live? If you have a state office of energy, they should be able to tell you this. It will be aprox. the temperature at about 25 feet down. The baverage ground temp where I live (Western Oregon) is around 55 degrees F. However, the measurements I have gotten at the bottom of my holes is 53 degrees.

2. What are the heating degree days where you live throughout the year? This is a number that is used to calculate of how much heat will be required in your area.

3. What is the heat load of your house? You can get some computer programs that can give you a pretty close approximation of this for free.

Try something here:

home heat load calculator - Google Search

...here's one that might work for you:

Heat Load Calculator / Refined Home Renovation

You can also figure it pretty close from your heating bill. Look at the bill from the coldest month, convert it to BTUs per hour for that month. and maybe multiply the BTU per hour by 50% to account for energy use peaks.

Last winter, where I live, we had a really cold spell, and for that two week period, I turned off my gas heat and used only electric heaters which had watt meters (Kill-a-Watt) on each one, and I kept detailed records every 4 to 6 hours, so I know with a very high degree of confidence what my energy use baseline is.

4. What is the rate of energy transfer I can expect from my source? In your case, the well you're talking about. If you look through this blog (http://ecorenovator.org/forum/projec....html#post2787), I site a test that you can do on your own well to determine what the rate of heat out will be.

So you can experimentally determine the heat you can get from your well, divide that into your calculated or measured peak heat load and see what percentage of your heat you'll be able to get from your well.

If it is over 100%, you are indeed in fat city!

If it's somewhat less than 100%, you can use your well as an adjunct to your existing heating setup and save some money.

If it's pretty tiny, like for instance only 5%, then you know that if you had 20 such wells, you'd be back in fat city.

I did exactly this procedure, and my calculations came out to 15.4 holes, so I'm going for 16.

I'm also going for a lot more insulation.

Hope this all helps...

Best Regards,

-AC_Hacker

[AC_Hacker]

Last Thursday, I had made great progress having finished the fifteenth hole.

I also suffered a setback when the pully which is at the top of my drill set-up failed.

I was trying to extract an auger from the hole #16 and the forces generated by the 2000 pound winch easily deformed it.

I wasn't terribly surprised as the pully was actually made for reeling in clothes line. I had estimated correctly that it was a good match for the manual winch, but the power winch was just too much for the light assembly.

So I bought a winch-grade pully and rebuilt the pully-carrier, this time with much stouter steel.

Problem resolved.

So now, with the show...



Regards,

-AC_Hacker

[Daox]

Wow, 15 holes. You're getting close now.

[AC_Hacker]

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* * LOOP SPACERS * *

There's one important detail I forgot to post earlier, so I'm apending it to this post...

I read that the performance of the boreholes is improved by keeping the 'down-the-hole' and 'returning' pipes separated as much as possible. There is a commercial product that is available that does an excellent job I am sure. But I made my own out of thin-wall irrigation tubing I had laying around and some bicycle tubes cut into strips. The local bike store most likely has a barrel filled with dead inner tubes, just waiting for you to come get some.

I put the spacers on the loop pipe at intervals of 3 to 5 feet.

In the beginning of this project, I bought 100 feet of thinwall 1/2 inch irrigation tube for $10. I soon realized that it would be crushed by the weight of the earth, so I didn't use it, and I had 'munged it up' enough that I couldn't take it back either. But it did turn out to be very useful for tubing spacers.

In the picture at the top are some spacers I cut from the plastic tubing. Since the holes varied in size, I cut a large number all at once, but varying in length from 4 to 7 inches, to fit various situations.

The photo on the bottom shows some strips of bike tires I cut into strips to use for tying the spacer-tubes onto the poly pipe loops.

I looped the tire strip around the poly pipe as shown in the photo below:

The photo above show how I passed the tire strip ends through the small tube.

And tied the free ends around the other leg of the poly pipe loop as shown in the photo below.

The photo above shows the spacerin place, doing its job of keeping the poly loop pipes spread apart. One nice thing about the thinwalled irrigation pipe is that if I mis-calculated the width of the borehole and put in a spacer that was too big, the thin-walled tubing would collapse a bit.

Toward the end of this phase of the project, I developed an alternate method which may be more appealing, and that was to make a wire hook out of coat hanger wire to be used with rubber bands cut from a fat tire bike tube. I tried a mountain bike sized tube for making rubber bands, even cutting them at a diagonal, and they were just a little bit short. I didn't try it, but I think that a 'fat-tire' innertube would be just right.

Upper picture shows the hook, with an orange ribbon attached to aid visibility, the tube spacer, and a diagonal-cut rubber band.

As shown in the bottom pic,the rubber band would be slipped over one leg of the loop, then the wire hook would be pushed through the spacer tube, hooking the rubber band. Then the hooked rubber band end would be pulled through the tube and slipped over the remaining leg of the loop. Several of these would be put over the loop, then slid into place at desired intervals.

I tried this method toward the end of the hole drilling phase, and it was just about as fast as the tying method, using cut strips, and I could see that with a bit of practice, the new method would go faster than tying.


Regards

-AC_Hacker

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[dremd]

WOW man
MAD props!

EDIT:
Just saw you notes above about VAC pump.
If you are going for cheap http://www.harborfreight.com/cpi/cta...emnumber=96677 is impossible to beat; you will need a big air compressor to run it; but if you are doing this , once per year you could borrow one . . . mine pegs my automotive HVAC A/C gauge every time.

I also own http://www.harborfreight.com/cpi/cta...emnumber=66466
Works well also (I use if for My bio-diesel pickup tank). If you want you can take advantage of Harbor Freight tools lax return policy and "rent" one if you are careful not to scratch/ get it dirty.

[Daox]

Alright! Congrats on getting all the holes done!

Next is trenching?