The Homemade Heat Pump Manifesto

[AC_Hacker]

Maxis,

Congratulations on your progress!

Originally Posted by Maxis

Hi AC_Hacker
* what is the diameter of your drilling pipes - as I understood you should fit two 3/4 pipes in drilling hole?

The drilling pipe I used was 3/4" inside diameter water pipe. I had no idea what I would encounter when I started, so this was what I began with. I had read some opinions from well-drilling blogs that said that 3/4 inch pipe was too small to use, but I decided to try it anyway. The reasons given as to why 3/4 pipe was too small were that the small diameter would reduce the pressure of the drilling fluid (bentonite-based mud).

The drilling fluid serves several purposes:

• it cools the bit that is rotating in the hole
• it lubricates the bit so it will easily keep turning
• it washes any debris away from the drilling bit, so as to expose the sharp parts of the bit to the earth you are drilling
• because it is more dense than water, it more easily lifts the debris (cuttings) up from the drilling face and carries them to the surface
• it forms a 'skin' inside the hole to keep drilling fluid from leaking out of the hole and getting lost, and to prevent cave-ins in the hole

So now that I tried it, I can see that for holes that are not too deep, 3/4 inch pipe will work, but if you want to drill deep, larger pipe will be required to reduce pressure loss and to reduce excess twisting of the pipe.

The drilling motor I used was 1/4 horse power (190 watts), which is very, very small by well drilling standards. I told some well drillers what I was doing, and they couldn't believe that anyone would use such a small motor, and they couldn't believe that it would work at all.

When I first started using the drill, I used water only as the drilling fluid. I didn't even know about drilling mud. It worked pretty well, but I was having terrible problems with sand caving in on the hole and trapping my drilling bit. Then I found out about drilling mud,and it made a big difference. To use drilling mud, you need to build a system that will capture the mud & debris that is coming up from the hole and allow the debris to settle out and then send the mud back down the hole.

Here's a photo from the web that shows a mud capture pit:

I made my own mud capture pit out of a big plastic tub, and it worked. The thing that was the biggest problem for my situation was that the land where I am drilling has many big rocks which are very hard. My little drilling rig was just too small to be able to drill through them.

I later discovered the idea of using a shop vac to suck the sand and small stones out, and I made a tool to lift the big rocks out.

My final technique for drilling consisted of:

• gas powered post hole auger to get down through the top two to three feet of roots, sand, clay
• my electric drilling rig to get through the next 3 to 4 feet of tough clay and into sand
• the shop vac to get down through sand to the 17 foot level where I hit hardpan and stopped
• the rock removal tool as needed to remove rocks

Originally Posted by Maxis

* how the swivel is build from inside - how water gets into the pipe if it goes through swivel?

Here is a photo of the swivel parts:

At the bottom of the photo is a piece of pipe that has two holes drilled in the sides to allow the passing of drilling fluid.

Here is another photo of the pipe being drilled:

I drilled two holes on opposite sides of the pipe and made sure that the area of the two holes together was just a bit larger than the size of the inside of my pipe.

And here is a photo of an epoxy plug I put in the top end of the pipe so that the mud would be forced to flow down:

Originally Posted by Maxis

* what did you use to fill drilling holes when pipes were installed? As I know the bentonite should be used.

There are two reasons to use a special 'grout' to fill the holes:

• improved thermal conductivity
• preventing intra-aquifer contamination

I did some research about various grouts and found that straight bentonite grout has a relatively low coefficient of thermal transmission. There is an open-source grout MIX-111, that has improved thermal transmission (because it has a high percentage of silica sand) and will seal against intra-aquifer contamination.

I did some testing on my soil and found that the index of thermal transmission was already about as good as MIX-111. I also was not drilling through more than one aquifer layer, so contamination was also not an issue, so I refilled the holes with the same soil that came out, in the same order as it originally was in.

Hope this helps...

Best Regards,

-AC_Hacker

[Maxis]

Thanks for so quick response - very usefull information!

It's getting cold there in Latvia and in winter the ground will be freezed up to 1m, but in spring I will try to do some drillings.

Have you read about CABLE PERCUSSION DRILLING

Example: Borehole drilling rig for water wells (cable tool percussion method), pile & probe driving, site investigation, workover, geothermal, prospecting, environmental, peizometers, remediation & geotechnical. There is also the video available

Of course the ready made drilling rig is expensive, but if you can build (or get) free fall winch, than the rest is nothing.

Best regards
Maxis

[AC_Hacker]

Originally Posted by Maxis

Of course the ready made drilling rig is expensive, but if you can build (or get) free fall winch, than the rest is nothing.

Maxis,

Yes, I did see that web page, it is very interesting.

Cable percussion (they call them cable drill around here) are used a lot here, where I live. I met a retired well driller last year and almost all of his wells were drilled with that type of rig. He built his own rig, something I found to be very impressive. Apparently, the cable that is used for percussion drilling has a twist that is opposite to all other cable. The percussion drilling parts screw together, and the special cable makes them all stay tightly together. If a normal cable with the usual twist is used, the percussion parts will unscrew and down the hole they will go.

Here is a file that has some good information about several types of drilling.

Of course Wikipedia has lots of good info under 'well drilling'.

But one of the more intriguing approaches I have found is call Baptist well drilling.

The cost of the equipment is very low and if the soil conditions are favorable, depths of almost 100 meters are possible.

I would think that by combining some of the ideas of the cable drill andd the Baptist drill, a simple cheap effective rig could be made.

In fact, this document has lots of facts and figures and photos of manual drilling rigs as well as a motorized drilling rigs.

I built one also and tried it. I got it to work by myself, but you really need extra people or a motorized rope puller, or both.

Here's a whole boatload of videos of people making and using Baptist well drilling rigs.

What I find inspiring about this way of working is that money does not have to be an impediment to drilling.

Best Regards,

-AC_Hacker

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[Maxis]

AC_Hacker,

Thanks, greate info for reading and looking.

I have underfloor heating in all house and I keep the output temperature of heat pump low to have high COP. I heat floor directly from heat pump without using any temperature reduction valves.

That gives high COP, but if you want to use heat pump also for drinking water heating, than water could be only preheated.
I plan to make small heat pump to raise the temperature to 60 C (max 2 KW heat / 600 W electricity). That would be good starting project - small compressor, only some wells needed. For me the direct expansion idea looks interesting. Propane (R290) could be used as refrigerant - it has good oil return properties, could be used without special permission, but it seems that high pressure would be needed to get 60 C. The Butane (R600a) could be the alternative, but I don't know about oil return.

Best regards
Maxis.

[AC_Hacker]

Originally Posted by Maxis

Thanks, greate info for reading and looking.

I have underfloor heating in all house and I keep the output temperature of heat pump low to have high COP. I heat floor directly from heat pump without using any temperature reduction valves.

That gives high COP, but if you want to use heat pump also for drinking water heating, than water could be only preheated.

Maxis,

It sounds like your approach is using all of the best ideas:

• radiant floors
• low heat pump output temp
• no temperature reduction
• heat pump hot water pre-heat
• organic refrigerant

...all very good.

It is my hope that other readers of this blog will be motivated by efforts such as yours.

Do you have any photos of your radiant floor / heat pump setup?

I am interested in the radiant floors in your house. Was the house designed with radiant floors when the house was built or were radiant floors put in later?

The reason I ask is that my house does not have radiant floors yet, and I want to put radiant floors in. My house is old and I'm not sure if it will support radiant floors with the usual thickness of 3 inches (7.5 cm). I'm going to start with a test room of 12 x 12 feet (13.4 sq meter) and the weight would be around 2448 pounds (1110.4 kg). Seems like a lot of weight to me.

Do you have any advice?

Originally Posted by Maxis

I plan to make small heat pump to raise the temperature to 60 C (max 2 KW heat / 600 W electricity). That would be good starting project - small compressor, only some wells needed. For me the direct expansion idea looks interesting. Propane (R290) could be used as refrigerant - it has good oil return properties, could be used without special permission, but it seems that high pressure would be needed to get 60 C. The Butane (R600a) could be the alternative, but I don't know about oil return.

Yes, I think 60 C (140 F) is too high in temperature for R290. The Japanese are now making vapor-compression water-heaters using carbon dioxide (R744) as a refrigerant. They are achieving temperatures of 194 F (90℃). The pressures to work with R744 are very high, but the technology is emerging.

Using R290 to pre-heat water to around 100 F (38 C) would be achievable. Then you could use a conventional heat source to go the rest of the way.

I wish you luck in this project!

Best Regards,

-AC_Hacker

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[AC_Hacker]

Back to building the heat pump from a used air conditioner...

My brazing skills went a bit rusty over the summer, so I thought it would be best to get the tools and skills ready to go so I can get on with the conversion.

In part 1, I showed you the MAPP gas tourch I'm using. As I said previously, I tried Propane, but it just didn't get hot enough to do the job. Mapp gas burns hotter than Propane, but not as hot as Acetylene. If you already have Acetylene, use it. If not, MAPP is good enough, and the setup is way cheaper.

So, in addition to the tools previously pictured, here are the tools I'll be using:

The flaring tool is usually used for making the flare for a flar fitting, but in this session, I'll be using it as a vice and as a heat sink.

The tube cutter is standard, but I know I'll be working in tight spaces, so the small kind is best.

The 'tube expander' probably has a much better name, but I'll be using it to expand tubing.

One joint we will need to make will connect two pieces of tubing of the same size.

Since refrigeration is subjected to vibration, a butt joint will not do, so the trick is to expand one piect of tube so that the other tube will fit inside.

Here I'm using the flaring tool as a vice and I'm tapping the tubing expander with a hammer to stretch the tube to the right size. I'm actually going two steps bigger, so the tubing got a bit deformed, but it ends up being a sound joint.

Here I'm applying silver-brazing flux to the tube that will slip inside.

Now we give it all the heat that MAPP gas has to give...

I have noticed that I am much less timid about applying heat than I used to be, and my brazing is all the better for it.

So now, let's see what we have...

(* * * to be continued * * *)

[AC_Hacker]

So here's a photo under the microscope of the braze joint I just did:

So, here we are, this was done with 55% silver brazing rod. Horribly expensive stuff, but it works like butter.

So, I cut the brazed joint off and I noticed a little black flake sticking out of the tubing:

So all the lovely heat of the MAPP gas has caused the copper in the tube to combine with oxygen and make this flake of copper oxide. This is VERY BAD for refrigeration, because the refrigeration circuit relies on liquid refrigerant passing through a capillary tube or a tiny orifice to regulate the flow rate. Just one flake of copper oxide could ruin the whole thing.

* * *

Another joint we will need to master is joining a smaller tube to a larger tube:

Here's how we do this one...

We put the smaller tube into the bigger tube and grab the edge of the big tube with a pair of pliers, and pinch...

...and pinch really hard and you've got it!

Now let's put some heat to it...

(* * * to be continued * * *)

[AC_Hacker]

The brazing rod I've been using is 55% silver. It cost me $20 for two ounces. Pretty expensive stuff. Around here they won't sell 5% silver or 15% silver in amounts smaller than a pound, and it costs $35 and $70 per pound respectively. But if you're only going to do a very small amount of brazing, $20 worth of brazing rod might be enough, and still it would be the cheapest way to go.

When I stopped off to see Bruce-the-pirate today, he gave me a stick of 5% silver brazing rod to try. I was pretty sure that it was going to be an absolute failure, but I decided to give it a try anyway.

So I fired up my tourch and leaned the flame into the joint I had formed at the end of the last post, Brazing (part 3).

Like I said, I have become much less timid at applying heat, compared to myprevious experience.

The 5% silver rod, and the 15% silver rod have a phospher-bronze alloy which is self-fluxing when joining copper-to-copper.

When I applied the 5% rod to the cherry-red joint, I was completely amazed, very fast melting and a very nice flow. It just took one small touch-up on the back side of the joint to make a good braze joint, all around.

Here's the microscope photo:

...but when I cut the joint out, all these black flakes of copper oxide fell out too. This will never work for refrigeration.

Something has to be done...

(* * * to be continued * * *)

[Daox]

Very interesting. I really don't know much about brazing, but could add flux to the inside of the pipe? Or would that gunk up the works too?

Also, how do the pros do this kind of work?

[AC_Hacker]

Originally Posted by Daox

...but could add flux to the inside of the pipe? Or would that gunk up the works too?

Good point. Now that I have experienced the glory of silver-phosphor brazing rod, I doubt that I'll use 55% silver and flux on this kind of work again. But joining copper to a different metal will still require flux.

Originally Posted by Daox

Also, how do the pros do this kind of work?

Check out this link:

How do HVAC professionals braze?

Best regards,

-AC_Hacker

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