That is interesting. I don't remember you mentioning that in the thread, sorry if you did. Hopefully I will avoid that necessity by not disassembling my AC unit. I would like to use it as is, sacrificing some efficiency for simplicity.

Okey dokey, thanks.

Try design I used in my house. It is light, strong, easy, cheap,....
The heat you potentially loose (I mean go down and not up) depends on density of material and area of contact(mostly). When you use cement board and fill gaps you loose more. In my case I used 1x2 strips of wood. The tube has good contact with upper plywood through aluminum heat plates and has no contact with sub-floor. The only contact upper layer has with sub-floor are wood strips(low density compare to cement and fraction of total area). Also I used aluminum foil for reflection of heat up toward top layer. If you want to be more sophisticated you can use special bubble foil insulation. I used foil because I needed 3000 sq-ft and it would cost me a fortune.

Unfortunately I can not tell you about performance because I started from house to outside and you started outside first. But I can not see no problems.

If you need more details or pics I can post them.

Vlad, I have been wondering how the floor part of your project is coming along.

Yes, this would be a very good idea. Since it is still fresh in your mind, and all the details have not gotten lost.

I'm sure your floor will work well, I sure would like to see some performance figures, when you get the water flowing.

I started a thread which begins here for DIY radiant floors. Since that is exactly what you are doing, it would be be a likely place for your photos and info.

And since it relates to the homemade heat pump thread, maybe you could post a link to it here.

I'm looking forward to seeing it.

Best regards,

-AC_Hacker

Ground Loop + Heat Pump Test #1
 

Yesterday I did a test of my homemade heat pump. This is the first test with the heat pump finally hooked up to the loop field.

Here's a photo of the setup.


"a" is the homemade heat pump that I built about a year and a half ago. I've learned a lot since then but I think I can learn more from this unit, before I build the next one.

Here is an older photo of the heat pump, showing better detail...


"b" is the white "source" barrel (so named because the ground loop is where the source of low grade heat is coming from). This is the barrel that has the water coming from the ground loop. I have a quarter-horse sump pump pushing water through aproximately 720 feet of high density polyethylene pipe buried in the back yard. The water then returns from the loop and enters the brazed plate heat exchanger on the left side (evaporator side) of the heat pump. After exiting the heat exchanger, the water flows back into the 'source' barrel, and the cycle begins again.

The photo below is a detail of the source barrel and the sump pump. I measured the sump pump and it was drawing around 250 watts of power, ok for initial testing, but way too much for normal operation.


"c" is the sink bucket (blue 5 gallon bucket)

The photo below is a detail of the 'sink' bucket (so named because this is where the high grade heat is going to). Here the water is pumped from the bucket into the brazed plate heat exchanger which is on the right side (evaporator side) of my heat pump. After exiting the heat exchanger, the water flows back into the bucket.

I measured the pump, (actually a heavy duty aquarium pump) and it was drawing around 25 watts of power.


The photo below, is a closeup of the point where the capillary tube enters the brazed plate, evaporator side (left side) heat exchanger. The frost gives me an indication that things are working. I should have positioned the cap tube at the top of the exchanger, so that gravity would be working for me. I will incorporate this improvement into the next unit.


The chart below shows data gathered during the test. I ran the test for an hour, taking readings every five minutes.


Even though I wasn’t monitoring compressor power, I can tell that the COP is way down, and experiments are in order to determine optimum refrigerant charge levels .

Also, for a heat pump of this size, the 250 watts being consumed by the sump pump is extreme and I need to find other pumping solutions that will reduce this.

Regards,

-AC_Hacker

So, it looks like you pumped ~2,800 btu in 1 hour. Does this sound right? If it is, that seems a bit low? Is that due to compressor size or something else?

"...a bit low...", you are being too kind.

Actually, it's awful.

I was expecting something in the neighborhood of = or > 5118 BTU per hr.

As I recall, in the beginnng, even before I made my first post on EcoRenovator, my very first test yielded really dissappointing results. In fact right there, in the beginning, I was ready to give up. But when I tweaked the charge level a bit, things really started to happen.

So, I'll be experimenting with charge level, water flow rates and also possibly heat exchanger sizes.

Regards,

-AC_Hacker

I would call it pretty good for a quick and dirty test actually.

2800 Btu in an hour but if you look at the first half hour I get about 4300 Btu/hr. That's pretty close to the AC unit rating of 5000 Btu/hr... I don't know how they test them but I'm sure they give the max efficiency rating (probably 1st 10 minutes), not steady state rating. Pretty good I'd say for using the equipment for something other than its intended purpose and design conditions.

Not to mention even if you consider the lower value of 2800 Btu/hr that's about 820W, and you're only burning 575W (300W compressor, 25W aquarium pump, 250W sump pump) for a COP of 1.4. So you're not losing ground.

Also the small bucket of water causes the dT to rise relatively rapidly. I bet you would get a better reading with a larger volume of water (big drum?) with insulation. You are probably losing a fair amount of heat to the air at 100F with convection. But mostly reducing your dT/dt I think would reduce the measurement error.

Most importantly it looks like you're reaching steady state with the ground loop so that is bonus.

Thanks.

I did another test today, and the compressor has a slow leak (always did), so by default I will be comparing progressively lower charge levels.

Today I was monitoring the power used by the compressor, so I was able to calculate the COP over each five minute period.

The power used by the pumps is not reflected in this chart.


The COP line is multiplied by 100...

... I'm also getting my data-logger set up to use in the testing, but it's not ready for prime time yet.

I think you're right about heat loss in the heat-sink bucket, most importantly is the fact that the bucket is sitting on the bare concrete floor!

Next test will have the bucket sitting on 2 inches of foam.

Part of the discontinuety in the data is due to the fact that the analog clock I'm using has floppy hands. I have a digital clock for further readings.

Regards,

-AC_Hacker

May I ask why you need to drill for closed loop water exchange setting? All the source I learned seemed to use trenches instead of wells. I'm really confused because usually they drill wells (shallow ones) for direct exchange setting.

Sorry it may seem to be a lazy question, since I may be able to find the answer by reading through this thread. But it's simply too much reading, with over 40 pages spanning almost two years. I very likely will take my time and read through it anyway because there is so much useful information. But for the moment, I'm really burning to find the answer for this really simple question.

And congratulations on the success and thanks for sharing this.

bigsmile, welcome to the conversation...
 

bigsmile,

Welcome to the conversation.

FYI, it is possible to search particular threads for certain key words, to find out what you want, but I will try to answer your question...

My whole reason for doing this is that I am aware that GSHP is the most efficient way to heat a house. I'm also aware that the entry cost of a GSHP is so high that the only people who can afford a GSHP are the people who don't actually need the operating cost savings that a GSHP can provide.

So I have taken upon myself to see if it is possible for a normal person, of normal means, to build their own homemade ground source heat pump from cast-off parts.

In other words I am trying to democratize the practice of Ground Source Heat Pump construction.

I live on a city lot and the loop field would have to go in my back yard.

I learned that foot for foot, full-depth boreholes are more efficient than trenches and slinkies.

I didn't go with trenches, because I couldn't see myself digging trenches by hand, and I didn't think I could build a power trenching machine.

I did think I could build a powered drilling machine.

Initially, never having drilled a hole any deeper than a hole for a fence post, I had no idea just what I would encounter if I drilled holes, and I planned to do some holes with a depth of 50 to 100 feet each. I thought if I drilled slowly, in time I would achieve my goal.

My next step was to hand-drill a 12 foot deep test hole, and perform a thermal test on it to see how much hole I would need to satisfy my estimated heat load. My test indicated that I would need about 200 feet of hole.

Then, I tried to drill deeper holes, but my equipment and technique caused too many problems to proceed.

(At this point, you may want to take notice of the work that Vlad has done because he has built a very serious drilling machine that looks like it will be able to do what my equipment could not)

In the course of my drilling, I did learn a bit about the soil conditions in my yard. I learned that there is a 'hardpan' layer about 17 feet down, that is holding up a water table which manifests as wet, coarse sand. This high water table and wet coarse sand is very favorable for heat transfer.

Based on this, I decided to go with 16 holes each 17 feet deep, with connecting pipes at a depth of 2 feet. The frost line here is 9 inches deep.

So the 16 holes with an effective length of 15 feet each would give me 240 feet of borehole, more than enough, I reasoned, to do the job.

But getting back to the borehole vs trenching approach, if you have a large enough area, and if you can get and run a backhoe, trenches just might be the way to go. However, the deeper you can go, the more stable is the ground temperature...there is that trade-off. I think the most often quoted figure is 'deeper than 25 feet', there is not much significant temperature swing. So I realize that my loop-field will have temperature swings, especially the more shallow parts. The same for trenches & slinkies, so the heat pump needs to work harder, later in the winter.

If I could have gotten a backhoe into my backyard, I might have tried trenches, I did consider it.

If you have more than a passing interest in this endeavor, you might want to read the whole thread, because there's a lot of info from my experience, and the experience of others, and also many very informative information resources that you can link to from the thread.

Best of all, there are now some other brave souls who have taken up the challenge and are trying their own projects, borrowing some methods, inventing some others, all driven by their own unique skills, gumption, and understanding.

In more ways than one, we are breaking new ground!

I invite you to join us.

Regards,

AC_Hacker

Thank you very much for the detailed answer. Mean while, during the hours I posted my question and now, I have roughly gone through this thread. One thing I'm curious about is that early on (in about the first post), you conducted some experiment with the heat pump you built. It had rather good cop numbers. Why now when you connect it to the ground loop, the COP drops so much?

Also, you mentioned the compressor has a leak. Are you sure it's the compressor, not the other parts of the refrigerant circuit? The reason I ask is because I have the feeling that the plate exchanges may not be for refrigerant, so it may be them that are leaking.

Great question...

This test is different from what would be encountered in actual practice, because the source temp is declining continually and the sink temperature is rising continually and there is no steady state. But it does give many snapshots of what to expect at various stages of temperature difference between the heat source and the heat sink.


Above is the ending part of the original heat pump test, with my new addition which is the fat red line that approximates the COP. As you can see, the COP is declining. In all of the subsequent tests I have done, I see the same thing. What is going on there is that the "source" temperature is getting lower and the "sink" temperature is getting higher. One way to look at it is that the heat pump has to "lift" the heat a greater distance and therefore has to do more work (a more scholarly explaination can be found here). This would account of a declining COP. In the early test I should have let it run longer so that the source temperature was well below what I would expect my loop field temperature to be.

(* I'm still testing for optimum refrigerant charging levels, and I may have some additional testing to do on heat exchanger sizing. If I want to strangle all of the COP possible out of my system, I may need to go to larger heat exchangers. *)

So I now know that my initial loop field temperature is close to 51, in December and I can expect it to decline somewhat as winter progresses, and the more I use the heat pump. I'm still not sure what the rate of decline might be, and I'll just have to use the heat pump under normal conditions to find out.

So, some lessons from all this are:

• a shallow loop field will work, but a deeper loop field will work better, because it is less affected by seasonal fluctuations (less heat when you need it most).
• a larger loop field will decline more slowly than a smaller loop field.
• a larger heating load will cause any loop field to decline more rapidly.

Step numbers one through three are still insulate, insulate, insulate.

I mis-spoke, I should have said that the system has a leak. The very last part I suspect of leaking is the compressor. The part I most suspect is the refrigerant-to-brazed-plate connection.


These particular heat exchangers are really meant for water-to-water use. And I had to get some adapters to fit water pipe threads to refrigerant tubing. I didn't appreciate it at the time I got the heat exchangers, how important it is to braze the whole system so that it is hermetically sealed.


Here is a heat exchanger I bought subsequently, which is meant for refrigerant use and has "sweat" fittings. Don't be confused by the name... in the refrigeration trade, they often say "solder up a system" and the name "sweat" would make you think that they are referring to sweat solder, but in practice, brazing is the method used, because it is stronger and more able to withstand decades of vibration. The construction of both exchangers is the same high quality, the connection is the difference.

I also may have a pinhole failure in the brazed joints I did... I didn't know what I was doing, and was really flailing about just trying to get something together so I could do some testing.

What I need to do is over-charge the system, remove the electrical connecting parts, and submerge the whole frigging thing in a water tank and look for bubbles...that would do it.

Hope this helps...

Regards,

-AC_Hacker

HP test - 4 (Dec 20, 2010)
 

I'm still having a heck of a time with the data logger, so here is more manual data logging...

Logging Improvements

• I have started using a digital clock (the one on the Kill-a-Watt) and the time is more reliable.
• I have insulated under the bottom of the blue bucket, so heat is not being lost through conduction into the basement floor.
• I've started logging the cumulative kw-h with the Kill-a-Watt, and using that in the COP calculations.
• I have started using a thermometer that responds in tenths of a degree to measure the loop water temp.

Below is the chart for this test, as in the prior tests, the energy used by the pumps is not being considered.


I've made the lines easier to read.

Due to the automatic scaling,the kw-h line is at the very bottom of the chart.

The COP*100 line looks pretty favorable (even pushing over 400%!), especially when the heat-sink temperatures are down below 100 degree range (when the "lift" isn't so high). This really speaks volumes about the advantage of radiant floor heating (huge radiating area, lower feed temperature), where feed temperatures are in the range of 85 to 95 degrees, compared to forced air (smaller radiating area, higher feed temperatures) where the feed temperatures are in the range of 120 degrees.

Below is the logged data for this test.


Curiously, the temperature of the loop field (AKA: 'T(source)') starts to climb a bit toward the end of the test. I think this is due to the heat being produced by the quarter-horse sump pump.

So next on the agenda is looking for a much lower wattage pump that can still provide sufficient circulation through the loop field.

Regards,

-AC_Hacker

Thanks for the reply, and for the invitation to join. I also believe that when it comes to heating and cooling, GSHP should be the way to go. But the current situation is that the high cost spoiled the whole thing for most people. I really hope that something will be done in the future to bring the price down. But for the moment, I can't resist being drawn to thinking about DIY. What I have in mind is direct exchange setup. It's efficient and also it requires smaller ground loop. The only thing seems to be certain technical difficulties, such as the oil return issue.

If that's the case, I came upon a masters thesis on dx system, in which it is stated that as long as the wells are shallow (20' or so) and the velocity of the refrigerant fast enough, oil return isn't an issue. Does this sounds correct to you?

In your other post, you mentioned the patents on dx system. I guess it may be a good idea for me to read some of the patents. Actually I have came upon a couple of such patents during my random search, but the issue is that the website I read didn't have figures. Just reading the text didn't give me very clear idea. Does the site you mentioned (about patents) have figures?

BTW this is really a great thread. I've spent some effort searching about GSHP, this is the one single most informative result I've found so far.

One thing about the efficiency is that the compressor you use may not have very high efficiency to start with. I think most window AC units have EER value below 10. The compressors in central AC units or mini-splits should have higher efficiency.

Yes, the oil return does seem to be the issue with DX systems.


Some DX companies drill a series of holes from a central header vault, that radiate out and down, this reduces the vertical travel but allows sufficient length.

By figures, I think that you mean illustrations... My favorite patent site is:

called freepatentsonline

...they have searchable text and you can also download a PDF of the whole patent, with pictures. I searched my files for a particular patent that would be very helpful to you, it was either taken out by one of the big air conditioning companies, or was assigned to them. Its real value was that it gave limits to certain proportions of tubing, like the length could not exceed 720 times the inside diameter (I just made these numbers up) in order for the lubricant to circulate properly. It had ratios like that for the whole system. Very useful.

Keep searching...

Also, there is a maker of GSHPs in Canada named Maritime Geothermal Ltd. and I have a PDF that I found previously on their website called, "Maritime Geothermal Installation Manual.pdf". That shows an installer (that could be you) how to build a DX loop field. I think this may be very, very useful for you. I just tried to find this document again, but no luck.

The document is about 1.5 Meg, too big for EcoRenovator to handle.

If you send me an email via the EcoRenovator thingie, I'll send you a copy.

I'm very glad that I can help. If you happen to come across material you want to share, this is the kind of place where you can share it.

I especially encourage you and anyone else who reads this, to do some actual experiments, to try things out.

I say this because it was when I built that little heat pump (that I am still testing) that this whole thing really started to seem possible.

And I think that when a group of people start sharing information and experiences, then the snowball will really start rolling.


Let me know if I can be of further help.

Regards,

-AC_Hacker

I think you may be right about that.

I actually have about a half dozen more compressors (people just keep giving me these things!) that came from equipment with better SEER ratings.

I'm also going to try a TXV valve on the next one.

Regards,

-AC_Hacker

I need to post this to be able to post email address.

It turns out that I need to have 20 post to send email on the forum. (I even need 5 post to be able to post email address.) I'm sure I'll get there sooner or later, but at the moment, if you don't mind, please send the document to whyharp@gmail.com.

I've been looking for something like an installation guide for DX for quite a while without success. So this is really something that I want to read. Thanks in advance.

Help is on the way...

-AC_Hacker

Got the file. Thanks a lot. With this, I may be finally able to put together a plan and get into action.

From what I have been able to gather, heat exchangers cost you about 10% in efficiency. I think this is one of the ideas behind HX systems... get rid of a HX and gain 10%.

I don't understand why no one is using DX floor heating, and cutting out that 10% loss also.

Seems to me that with copper tubing in the floor and all on the same level, the lubricant loss issue would not be so bad.

-AC_Hacker

If DX is used on the sink end, as well as the source end, this may be able to solve the problem of refrigerant imbalance between heating and cooling. During cooling, the refrigerant in the floor coil can be pumped to the ground coil to make up for the shortage, and an alternative air based evaporator coil will be used, which uses much less refrigerant.

Can you use soapy water from a spray bottle?
(That's how they find leaks on tires... :-)
Then you don't have to immerse a partly
electric device...

Seth

copper in the floor isn't used very often anymore since it reacts with the cement and will develop leaks eventually. PEX is much more common but I don't know if it is ok with refrigerant or not.

Seth,

Thanks for your suggestion. I did try the soap-bubbles method previously and I couldn't find the leak.

...and you're right about the electronic part, but that is all easily detachable from the top of the compressor (one nut & three spade connectors), leaving nothing but hermetically-sealed mechanical parts.

The problem is that the leak is really small, about 2% a day, so I'm afraid I'll need to use extreme methods.

In the meantime, I'm running daily tests and carefully monitoring COP, to determine what the most efficient refrigerant charge level is. So far, the COP is still climbing.

Regards,

-AC_Hacker

I'm open to all ideas no matter how far-fetched...
 

Strider,

Yeah, I know about the caustic nature of concrete, and how it will eventually eat copper... it eats aluninum too.

But the potential for increased efficiency is really tantalizing. Another thing that I keep thinking about is the fact that the refrigerant lines would surely have a smaller diameter than PEX and a thinner, lighter floor might be possible.

This leads me to another problem...

I'm trying to think of a better way to do a warm floor, a way that would minimize thickness and especially weight but maximize conductivity.

Here's the problem as I understand it:

WET SYSTEMS

(PEX pipes cast, in place, inside of concrete)
So far, the most efficient floor construction for radiant floor is a concrete slab whose thickness is 3 to 4 inches thickness, well insulated from the bottom (3 to 4 inches, or more of high-density foam), with a good conductive layer on the top (no cover at all over the concrete, or thin linoleum or ceramic tile). The feed tubes are closely spaced (around 6 or closer), of larger diameter (5/8 or larger) and are near the bottom of the concrete slab. The thermal mass of such a slab is very large, it takes about two days, maybe longer to bring it up to temperature. But the temperature of such a slab is very even across the the top, so you end up with a huge, evenly-heated radiating area. All of this is done so that the feed temperature can be as low as possible often at 85 degrees, possibly as low as 80 degrees F, allowing the heat-pump to work at it's highest COP. The down sides are that the system doesn't respond to temperature changes quickly. it is very heavy and expensive. This system is reserved for new construction, on-grade work.

The next best is a thinner slab, maybe 1.5 inches thick of concrete or what is known as Gyp-crete, which uses Gypsum as a filler to produce a lighter floor. The conductivity of Gyp-crete is lower than cement and it is more expensive. Because if the reduced thickness, the surface temperature is less even and there are temperature peaks and valleys. To provide sufficient room heating, the feed temperature must be higher, somewhere between 90 and 100 degrees F. Here the heat pump COP will not be as high.

DRY SYSTEMS

(PEX or other pipe inside, or on, or under more common construction materials like dry-wall, plywood, wood or MDF etc. sometimes with aluminum fins to aid heat conduction.)
These systems have the lowest thermal mass, and can most easily adapt to temperature changes. They are least expensive to make, and can easily be used in suspended floors of conventional construction. Vlad has constructed such a system to heat a home he is building. He is using aluminum fins and also aluminum foil to direct heat up to the floor surface. I am very interested in how Vlad's floor will perform.
There is another way where foil-covered MDF "puzzle-pieces" with pre-formed grooves for the PEX, are nailed down to the top of an existing floor and the PEX is forced into the grooves and a covering material goes over the top.
Usually the the temperature peaks and valleys is higher for these floors than the 1.5 inch gypcrete floor and the feed temperature of these floors is higher, usually running around 95 to 105 degrees F.

So, with that as a history, I am trying to come up with a wet system floor that would use a material that would be lighter than concrete (density = 145 lbs/ft3), that has a much higher index of conductivity (10.0 Btu-in./hft2F)

It should also, if copper tubing is used, have a similar index of thermal expansion. PEX will flex, so expansion doesn't seem to be a problem.

I tried some experiments with PEX cast in concrete samples, but the experiments were poorly designed and didn't indicate anything conclusively.

I also tried concrete with aluminum bits as an aggregate, which was a disaster because alumimum reacts with concrete and causes it to foam up.

The material for the wet system doesn't need to be concrete...

I'm open to all ideas no matter how far-fetched.

Regards,

-AC_Hacker

Thanks for the great info/ radiant floor ideas.
 

AC,
I have to express my appreciation for this thread. I stumbled across it yesterday afternoon and have been like a kid in a candy store reading through the entire thing from page 1. Awesome job to you and Vlad and all others who went out and "did something". I have been entertaining the idea of GSHP for some time now and am thrilled to find a place where many of you have taken the dedication and initiative to go beyond the "entertaining the idea" stage and actually do something about it, whether right or wrong. Very impressive to all of you, I am excited to see how it turns out and am looking forward to taking some action myself.

I have noticed AC that you stress over and over in the post how "insulation, insulation, and insulation" should be one's first call to action so I will start there and also get the GSHP manual you talk about and begin educating myself further.

I have an incredible resource at my disposal in the form of a 15 acre lake positioned 65' from the back of my house and its 13' deep avg. I think this may allow for some very EASY and flexible testing scenarios this spring without all the sweat equity you gents have had to do. However, I don't know a whole lot about HVAC and especially the particulars regarding heat pumps and thermodynamics, but I have certainly learned a lot in the past 24 hours.

As to the radiant flooring, it would seem the most bang for the buck would be a "staple up" method underneath with the foil fins, covered on top with durock and tile flooring. The durock would be bonded to the original subfloor with screws AND thinset mortar, the tile would be bonded to the durock with thinset mortar creating a pseudo stone surface thickness of around 1". The question is, can you live with the inefficientcy of the not very heat conductive wooden subfloor standing between your heat source and stone floor?

Something that hasn't been mentioned previously, and I am surprised Vlad did not run into some of this, is the height factor for anything on top of the floor other than perhaps the MDF foil "jigsaw puzzle" you mentioned (I am familiar with). If a person were doing an entire floor, rather than just a room, and I am guesstimating here with Vlads floor. He put down 3/4" furring strips, then covered floor with 5/8" ply, so now he's at 1-3/8" up with a bare floor. What type finished flooring? hardwood, add 3/4". Tile with underlayment, add another 1-1/8". If he used tile (without cementitous underlayment) or hardwood, he has raised his floor by 2 to 2-1/4". Can he still open his exterior doors? Did he remove them and cut some of the header out and re-install? Will he have to remove/reinstall all of his interior doors as well (could undercut the interior door jambs and simply saw the bottom of the interior doors.)

It seems that if a person is not going to go some route with a poured concrete substance (sometimes the juice isn't worth the squeeze!) that doing a staple up scenario would yield as effective as what Vlad did. I say that because if we really look at what Vlad did.... he put radiant heating on the bottom of a new subfloor that sits on top of the old subfloor. Would his results be the same had he put it on the bottom of the old subfloor and sheeted the bottom of his unfinished (I am assuming they were unfinished) floor joists? I only bring this up as a consideration of cost/effort, not to undermine Vlads' work. He has done far more than I. Thanks again to all, I am loving this discussion/thread.

Hybrid Floor?
 

AC,

I was just sitting here thinking how can a person find a compromise between a full concrete floor vs a staple up scenario??? Perhaps this is a solution:

What if a person used metal studs as a concrete form to make "heat slabs" of a certain dimension? Galvanized metal studs used in commercial construction are thin, light, good transfers of heat, and cheap. They are shaped like a "U" and if layed flat, would yield a "tray" that was 1-1/2" tall x 4",6",8", whatever dimension you like depending on cost and availability.

Let's say you could find 2x6 metal studs on craigslist for a couple bucks each. You could run 1 tube down the middle, because they are easy to cut and work with, you can put them end to end to make a tray that you can run from wall to wall and then fill with the sakrete product of your liking. You can also do them 1 at a time making this a DIY dream. This would give you a preformed "slab" with a heat tube running right through the middle. Maybe you only place a run every 12" in the room, cutting your concrete weight down by x% but still giving you some mass. Fill the voids in between with foam and wood for subfloor support and something to fasten to. If you aren't worried about the raised floor height, this may be a great solution. If you used something cementitious as a substrate (i.e. durock, hardiboard, etc.) then you could further strengthen the thermal bond by applying mortar to the tops of your "heat slabs" as you go.

It seems this may allow each person to micromanage the weight/efficiency trade off .

AC Hacker,
I would like to start by saying great blog..
I live in the interior of Alaska and have been interested in GSHP for quite a while now, I worked for a commercial outfit about 14 years ago installing them in commercial and residential settings.
I am also very interested in re purposing other peoples "junk", I scrounged up a de-humidifier a few months back with the intention of hacking into it to make a small scale GSHP to test out. I have ground water at about eight feet and also heavy equipment to move dirt (40 acres) so burying field loops should be no problem just the material and diesel fuel cost to run the dozer.
I have been planning on building a new house for a few years now reading on super insulating and heat recovery ventilators and such.
what I am interested in at the moment (its cold outside) is more pictures/drawings of how exactly you tied the tubing from the compressor to the heat exchangers. I saw the pictures of where you cut the tubing apart and what you reused. I was wondering what controls the cold side temp above freezing your exchanger up, or is that a function of how much water is run through it?
I test ran the de-humidifier the other day after partial dis-assembly and the condenser got hot and the evap side got cold, I disabled the cooling fan by pulling a wire and ran it that way for a while.
thanks
Joe

I just recall something when I read about DX hp. I think the oil return problem isn't restricted to vertical arrangement of coil. Long run of horizontal coil may also have this problem. To furcilitate oil return, it is usually recommended that horizontal runs of copper tube be sloped a little. This may be difficult to arrange if refrigerant lines are directly used for floor heating.

Jay-Cee,

Welcome to the conversation.

I really do like your ideas regarding radiant floors, I'm going to have to think these over. I especially liked the modular idea with the 6" steel 'stud' and the cast-in PEX. I like it, I like it.


Yes, insulation. Don't know if you're familiar with the German 'Passivhaus' concept. In North America, they call it "Passive House", but it's different from passive solar heating, although Passive House does include passive solar heating. The reason I mention it is that they have made some serious headway regarding insulation and high-performance windows.

When the insulation is really excellent, heating becomes less demanding. And sometimes hardly even necessary.

Wow, your job just got a lot easier.

Since you’ve made it through the thread, you know that doing a heat load analysis is in order. Probably even before you get serious about insulation. Here’s a free tool for you to use. It would be a very good idea to do an honest analysis on exactly the situation you have right now, I know it's tempting to fudge on the numbers, but do it just as things are right now, and save the results. Then do it again for how you want to do the insulation and compare. This will make a big difference, and it will go a long way toward shaping your thinking.

It's also best to consider that energy prices will get higher in the future.

Energy saved is cheaper than energy made.

I don't know if you found it, but there is a guy with a web site who had exactly the same setup that you have, and he did a successful install. His site is called something like "DIY Heat PUMP". I just searched for it and couldn't locate it. I wrote to him and told him I was doing a similar project, including building my heat pump from parts from an air-conditioner. I never heard from him again. I guess he thought I was kidding!

However, even though he had a pond near his house, and even though he had access to heavy equipment, and even though he bought a ready-made heat pump, and even though he utilized existing central air infrastructure, he said that putting in that heat pump system was the longest, most involved project he had ever attempted.

Oh well...

So, once again Jay-Cee, welcome aboard. Your enthusiasm is most appreciated.

As you proceed in your project, as you have discoveries, please share and if you have questions, please ask.

Best Regards,

-AC_Hacker

Joe,

Welcome, welcome, welcome.

OK, I tried to take a photo, but there is so much tubing and sensors going on I'm afraid it would confuse you badly.

So a drawing is in order:


I didn't draw the wires going to the compressor for clarity...

a.) This is where the refrigerant leaves the compressor, and so it's where the circuit starts. The compressor squeezes the vapor a lot and when a gas is squeezed (AKA: compressed) it gets hot. So if you touched the tube leaving the compressor, it will be hot to the touch. It might be very hot, so be prepared to pull your finger away quickly.

b.) The refrigerant then flows through an up and then down path into the heat exchanger. It's no accident that the tubing goes through this long path... the compressor vibrates when it is running, and having a long path spreads the repeated stress out over a longer distance.

c.) This is where the refrigerant leaves the heat exchanger. It is best to have the refrigerant enter at the top and exit at the bottom, so that gravity will act in your favor. When the refrigerant flows through the exchanger, it is cooled by the water that is flowing in the opposite direction (very important for efficiency). A lot of the heat that the refrigerant had gained when it was compressed, has been picked up by the water. The hot water can be used for something useful, like heating your home in Alaska. In the process of giving up its heat, the hot vapor begins to turn to liquid refrigerant(AKA: it condenses). That is why this heat exchanger is referred to as the condenser.

d.) I hope it is clear in the drawing that the tube from c-to-d is passing behind the compressor, and is not going into the compressor. The point "d" is where the refrigerant tube is brazed to the very small diameter tube (AKA: capillary tube, or cap tube). The tiny tube going from d-to-e is the cap tube, and its small diameter, along with its length acts to slow and regulate the flow of the refrigerant in the system. Sometime the cap tube is refered to as a 'metering device'. So pressure builds up between the compressor and the cap tube. All the tubing from a-to-e is referred to as the high pressure side (AKA: high side).

e.) This is the point where the cap tube is brazed to some larger copper tube. When the high-pressure refrigerant leaves the cap tube, it sprays out and instantly goes into a vapor state (AKA: evaporates). When it evaporates, it gets cold, very cold. Just imagine a hot day and spraying water on your face... same thing.

This is also the place where the refrigerant (very cold refrigerant) enters the heat exchanger. Again, it is a very good idea to have the refrigerant entering from the top and exiting from the bottom, so that gravity is our friend. While the cold refrigerant flows through the heat exchanger, it is taking heat from the water that is flowing in the opposite direction (very important for efficiency).

So the water that flows through this heat exchanger (AKA: the evaporator) will flow next to some water. The water will give up some of its heat to the refrigerant. And the refrigerant will carry this heat on through the cycle.

This is where we run our ground-loop water. So even though the water is pretty chilly, it's about 50 degrees here in my loop, the refrigerant is so much colder, that it take the heat from the water...

f.) This is where the refrigerant exits the heat exchanger. The refrigerant will carry the heat that it picked up, with it on it's way to the compressor. Again, there is a loop, in fact, there should be another loop that I left out for clarity. But you need to have them there for stress relief. As the refrigerant passes from f-to-g, it passes through a filter that serves to hold excess refrigerant, and also to filter out any unwanted bits. There is also a dessicant that will trap water that may have been in the circuit. Water and refrigerant are not a good mix.

g.) This is where the refrigerant re-enters the compressor. the refrigerant has been cooled by rapid evaporation, then warmed somewhat by water in the heat exchanger, but it is cool enough to keep the compressor running cooler... but it does pick up some heat from the compressor.

So there you have it.

Did that help?

Great question. For sure, you need to keep an adequate flow rate going, or it will freeze. You also have to monitor the temperature so that if it approaches freezing the unit will automatically shut down before harm happens. But in your case, you'll want to run some kind of anti-freeze mix in your loop field. There are antifreeze liquids that will not cause environmental damage. You can probably google it as fast as I can.

Hope this has all helped.

Best regards,

-AC_Hacker

AC_Hacker
that is absolutely great of you, that drawing did it for me. that is what i was thinking but have not hacked into these much yet, I have a basic understanding about how they work but not alot of hands on yet. I think one of the missing links for me was the refrigeration regulation, on these small systems I now understand it is done by the capilary tube, this provides the pressure drop the refrigeration needs to get cold. In the natural gas industry they use a JT valve (joules Thompson) to liquefy natural gas, same thing here.
so on bigger systems do they use an adjustable valve to better regulate how cold the cold side is by varying the pressure drop?
Yes I would agree that counter flow in a heat exchanger is the most efficient at heat transfer. I will have to order up some flat plate heat exchangers off e-bay to get my experiment rolling soon, only a few more months before it warms up and other projects will take precedent over this.
I have been reading alot on construction in sub-arctic conditions for quite a while, the university here has published a cool manual
.cchrc.org/docs/best_practices/REMOTE_Manual.pdf
I think that super insulated is by far the way to go, as you stated energy is only going to go up.
I plan on taking my time and building a home correctly then heat with the best means to include radiant heat. Open floor plan that can be heated with a wood stove in a pinch but have the primary heat pump secondary wood/coal fired outdoor boiler.

I have a set of gauges and a home made vacuum pump from an old freezer now I need to get me a small set of torches and play around with getting the fittings to bottle up my refrigerant from my system. Up to this point I have only played around with R134A on a few vehicles, patching the leaks pulling a vacuum then recharging them, with pretty good luck.

Really looking forward to tearing into this project in the coming few weeks, thanks for the kick start, oh on that link there is a link inside it to some pilot projects here in the Fairbanks area where they installed GSHP systems this year, be interesting to see what they come up with for numbers.
Shoot if I could even heat a small building like my chickens house with this heater for cheaper than I can with oil I would be happy...
thanks again for the welcome, looking forward to reading more about your project and I will work on learning all I can and sharing it here..
Joe

Yes, exactly so. I have an adjustable valve I'm going to try out on my next system, which I think will work ok. For the smaller compressors, it's a bit challenging because the valves have a stated range within which they work. It seems to be easy to get valves in the one ton and higher range, but not so easy when you want to go smaller.

Just in case you don't know this already, the cap tube diameter and size is precisely fitted to the compressor/heat-load/refrigerant combination. If you have a compressor meant for R-22 and you want to use R-134a, not only will your cap tube no longer be the right size, but your heat exchangers will be too small (R-134a carries less heat per compressor cycle than R-22), and worse, the R-22 lubricant is not compatible with R134a. R-290 has similar characteristics to R-22. This is one of the reasons I have used R-290 (AKA:propane) which of course carries substantial personal risks to work with, and it is illegal in some parts of the world. There is some stuff available on ebay called Enviro-Safe 22a, which I am interested in trying, which seems to be a direct replacement for R-22. It may be propane, I don't know.

If your de-humidifier was charged with R134a to begin with, you're good to go.

I've been using a 500 watt compressor that previously had R-22. I used 20-plate heat exchangers that are about 8 in by 2.5 inches. It seems to be working out pretty well. Try to get heat exhangers that have pipe thread fittings on one side and "sweat fittings" on the other side.

Don't forget that you need to flow some kind of inert gas through the tubing you will be brazing, otherwise the copper will oxidize and you'll have nasty flakes in yor system that could clog your tiny cap tubes.

And I like the idea of a homemade Freezer Compressor vacuum pump. I think that there are lots of people who would like to see how you built that... Please post photos!

By the way, the manual you mentioned is absolutely great. It really has some of the best building techniques I have see regarding insulation.


However, I haven't gone through the manual carefully, but I did not see any mention about methods to use to avoid Thermal Bridging, which the Passive House people are well aware of. Thermal bridging can reduce your effective R-value by 15%, check it out.

So good luck with your project... be sure to let us know how it turns out.

Best Regards,

-AC_Hacker

I read through parts of the REMOTE manual, and I like the fact that they're proposing walls a foot thick with insulation. However, I don't really see the advantage of this approach instead of putting the extra insulation in an offset studwall INSIDE the house. A staggered studwall allows for a conventional, durable, well-tested exterior construction method.

I'd like a house with thick walls, windows mounted flush with the exterior, and a deep window sill for potted plants or people to sit on.

R.E.M.O.T.E wall system
 

Part of the idea of adding the insulation on the outside to to build a continuous pure insulation to provide 100% free thermal bridging. Another reason is to provide the cold area outside away from the interior to prevent condensation from forming and building mold and such inside the wall cavity. Here in the Interior you don't place any plumbing in exterior walls due to the freezing problems during extreme cold spells. This building technique allows you to put plumbing and other utilities into exterior walls.

This method would also be less labor intensive and less cost than the "Swedish" walls that you mention "staggered walls" or a wall within a wall.
This would allow you to frame with 2"x4"'s if you wanted to or else they say 2"x6" on 24" centers if you wanted to run any type of utilities in them to allow for more room.

Just plain 2"x6" walls here in the interior is not enough to be very energy efficient, there is a lot of thermal bridging at all of the studs which lowers the whole building R-value by quite a bit as AC_Hacker said.
So adding a few layers of sealed foam on the outside of the building stops all thermal bridging except around doors and windows.

perhaps a more conventional radiant floor idea
 

AC Hacker,

Something else just hit me that may be more conventional and cut out some challenges AND cost while still being potentially just as efficient so I thought I would throw it out here for review and see what everyone else thinks.

When I think of the modular idea previously discussed with steel studs, I see the pro's as being:

1. Relatively cheap.
2. Readily available.
3. Ability to do one run at a time and can do solo if necessary.
4. Concrete slabs would be easy to vibrate/trowel to an even and consistent height.
5. Ability to manage how much concrete weight you want to add (at the cost of efficiency)
6. Sufficient density and mass
7. Slabs can be bonded to new subfloor with mortar enhancing thermal transfer.


What I don't like:

1. Overall floor height being raised at least 2", probably more like 2-1/2" and all the challenges that come with it. (stated previously, but I also wanted to add the trip factor if a person doing this has stairs going up or down anywhere in the house. We have all heard the saying "watch out for that last step...!"
3. Voids of either air, or wood, or foam insulation in between each slab takes away from the "even-ness" of the overall system.
4. Cost of concrete, mortar, additional substrate, furring strips, insulation (maybe) and steel studs could add up more significant than expected.
5. Long term potential possibility of termite/insect infestation without homeowner ever knowing because the floor is now above the bottom wall plate and has voids.

The height thing is a real dealbreaker in my mind, so I started thinking "how can a person place/pour a 3/4" - 1" concrete floor filled with tubing and it not crack or break up over time due to the shallow height??

So here was my evolution of the idea... What if you cut 5-1/2" wide strips of 1/2" or 5/8" concrete board (wonder board, hardi board etc...) and screwed them to your original subfloor leaving a 3/4" gap between each. Then run your 1/2" plastic (it would yield a run every 6" O.C.) in the gaps. Then tile DIRECTLY over the top (preferably a larger floor tile like 16x16 or even 24x24). As you are setting your tile you will fill each pipe run gap with mortar which will bond the tube, the cement board, and the tile all together at the same time. Most good tile mortar has latex flex agent added to it to allow for movement. The larger tile will yield a fabulous bond to the substrate below and there will be NO VOIDS. Thus, your total FINISHED Floor height will be: 1/2" cement board/piping + 1/8" mortar bed + 1/4" tile = 7/8" above subfloor and no challenges with doors/stairs. It seems this would yield the most uniform and "solid" type surface with the least amount of materials.

Note: I would put the strips across the floor joists and mortar them to the subfloor to ensure strength.

I also did some rough calculations about cost and weight for comparison.

Weight (using a 30x30 floor, 900 sq ft.)

Per Radiantec.com's DIY radiant floor installation guide (I cannot post a link)

They recommend on a floor joist system installation:
7/8" pex on 16" center (would seem appropriate for the modular slab idea)
or 1/2" pex on 8" center (my idea above mentioned 6" on centers)

so my rough calculations were this
Modular Slab design with metal studs:
* would need 25 runs at 16" OC approx 28' long (not sure how much room needed to bend 7/8" pex in a "U" shape). Plus the 2 ends at approx 30'
25 runs x 28 feet = 700' + (2 runs x 30') = 760' of "modular slab"
* avg weight of concrete/cubic foot = 143.38 pounds.
* .125' x .4375' x 1' = cubic volume/lineal ft. of 2x6 steel stud = .0546' cube
* .0546 cubic feet x 143.38 lbs = 7.83 lbs/ lineal foot of modular run.
* 7.83 lbs x 760' of slab = 5949 lbs.
* Then have to add concrete board on top of that. 1/2" Wonderboard claims on their website to be 55 each sheet (3'x5').
* 15 sq ft = 55 lbs or 55/15=3.66 lbs/sq.ft.
* 3.66 lbs * 900sq. ft. = 3299 lbs.
*Thus far total weight is 5949+3299= 9248 lbs.
Not included is finished floor material weight, water weight in pipe, additional mortar, wood furring strips, or metal studs.
Seems a little heavy, will be over 100 lbs./sq. ft. when all else is considered.

The new idea would only weigh the weight of the concrete board, 3299 lbs + the mortar bed and fill (not calculated) + the tile (not calculated). My thoughts are that it is a significant amount of mass, but certainly not so heavy one would have to question whether his joist system could hold it. I believe this type of weight would work on any home without question. If you think about it, its nothing more than installing a tile floor with the exception of "hiding" some pipes in the underlayment.

Cost:
additional 41.4 cubic feet of concrete-(.0546 cu ft/lineal ft. x 760 lineal foot)
Whatever you spend on metal studs.
Possible pricing difference between 7/8" pex of lesser length vs. 1/2" pex of greater length.

Final Note and Disclaimer: Please keep in mind that NOTHING has been mentioned about what method would or would not be more thermally efficient. I am completely uneducated in that area and hope that your responses will help me to understand! All logic here is approached from a "what seems easiest from a cost, construction, longevity point of view", and probably a biased one at that.... be advised.

AC_Hacker
I will try to insert a picture of my donor de-humidifier below, it has the capillary tube split into two parallel runs instead of one capillary tube coiled up.
So do I try to find some new capillary tube to replace the two with one so total length of the two?
or do I just try to fashion up some kind of fitting to braze the two in parallel?
I don't think it will by too difficult to try to braze them in parallel. I see at the local hardware store they sell a very small tubing that i could practice with, oh yah and I won't forget about the purge gas during brazing...
Joe:cool:

Jay-Cee,
have you heard a product called warm board?
looks like the way to go for new construction or you may even be able to add it to a home on an upgrade?
warmboard.com

Joe