The Homemade Heat Pump Manifesto...
 

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NOTE: This blog string started here. It was suggested to me that it might better belong here:

http://ecorenovator.org/forum/projec....html#post2631

...so I made that change. You might want to want to read both blogs, but the real action is happening at the above link.

Regards,

-AC_Hacker
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Hello all,

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

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

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

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

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

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

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

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

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

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

So there are four parts to the project:

1. The Ground source loop field.

2. The Heat Pump.

3. The radiant floor system.

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

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

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

Humbly Yours,

- AC_Hacker

That's a 'cool' project you're in:) I read a book on home GSHP, mostly water-water. It had a few pictures of homemade contraptions with a word on what not to do when doing it yourself. I can't tell you more at the moment b/c a friend borrowed the book.
I'm wondering if installing a window A/C unit backwards would work as an air-air heat pump? It'd heat only one room, so you'd want it only where you spend most of your time, keeping the rest of the house cooler. There is also the question of efficiency - it might gobble too much electricity.

AC_Hacker: Maybe this thread should move to the Saving@Home subforum? There's more on heat pumps there. There is also EcoModder's evil twin, EcoRenovator, with a forum and everything. You can find most of us there:)

Piwoslaw,

The book you mention sounds very interesting. I sure would like to know more about that!

Regarding using an Air Conditioner turned backwards, I have heard of people doing just that. I am currently using a Sanyo Mini-Split heat pump and I have examined it and compared it to an AC of similar capacity. The thing that really stands out is how much larger the area of the evaporator core is on the heat pump, compared to the AC unit. It's over twice the size.

I believe that the amount of heat that can be transfered by a given volume of water compared to a given volume of air is about 3500 to 1.

I think that the energy consumed by a fan to move a unit heat in air is greater than the energy consumed by a pump to move the same amount of heat in water. I don't have a figure for that.

Radiant floor installers figure that there is a 30% efficiency advantage over central air systems. They also have the advantage of no noise, no draft, extraordinary reliability, and greater comfort.

But, all that aside, turning an AC backwards is much simpler, and should be more efficient than using resistance heating.

Cheers,

-AC_Hacker

I'd probably have to translate it for you, since it's in Polish. The author is a local heat pump installer (and, I believe, a professor). Hopefully I'll have the book back in a few months (my friend is looking for ideas to ecorenovate his summer house), then I'll scan some pics and translate a few interesting bits.
I wanted to exchange radiators in our house for floor heating to raise the efficiency of a heat pump system, but it turned out that our lot isn't good for a heat pump (small and lots of tall trees), so the floor system wouldn't pay for itself. But the installer (actually the author of the mentioned book) told me that a radiant floor system should have at least 8 meters of pipes per square meter of floor. Maybe in your area the numbers may be different (the units definately are...), so find out about that. Hope that helps some.

--Adam

> ...but it turned out that our lot isn't good for a heat pump
> (small and lots of tall trees), so the floor system wouldn't
> pay for itself.

If you can borrow or build your own well drill, a vertical borehole loop field can be reasonably inexpensive. Also, lots of heat can be had from a small lot. Is your problem with tall trees the issue of drilling through the roots?

> ...a radiant floor system should have at least 8 meters of pipes
> per square meter of floor.

Interesting... Most of the hydronic systems in the US consider 6 inch spacing to be the minimum. Your specification works out to about 5 inch spacing.

If everything else is equal, your spec of 5 inch spacing should prove to be more efficient.

By the way,there was a free design tool that I used called "Hydronic Explorer 2" by a company called Slant Fin. (Slant/Fin | High Efficiency Boilers, Baseboard and Radiant Heating) . You may still be able to find it. Easy to learn, very informative.

Cheers,

AC_Hacker

The closer the spacing, the more pipes you get in, and the lower the temperature, which does raise efficiency. Also, with more water in the system you might not need a buffer tank.

As for our heat pump: Our lot is small with lots of shade year round, so we'd have to drill. On top of drilling costs, local laws require permits and fees for drilling, while the soil under us is dry (wet is better for GSHP). The guy I talked to said that maybe it'd be worth it if we were building a new house, but not when retrofitting an old one. For a fraction of the cost we could add insulation and exchange our oversized natural gas furnace for a smaller high efficiency (107%) model, and then the bills would not be much higher than with a heat pump and radiant floors.
We will get a heat pump, but an air-water model for heating water with waste heat from the ventilation. That, plus a new ventilation system and solar panels for hot water, will be in a new thread when we finally get that project going.

Piwoslaw,

> On top of drilling costs, local laws require permits and fees for drilling,
> while the soil under us is dry (wet is better for GSHP).

The local laws and permits issue is why I built an ELECTRIC earth auger. It's very quite.

Around here, a finished borehole (drilling + pipe +grouting) that will yield 12,000 BTU per hour, costs $7000 (3.5 KW per 24,660 PLN) and would be 200 feet deep (61 meters). It could also be two 100 foot holes, or four 50 foot holes, or eight 25 foot holes, etc.

$7000 is a lot of money for me, that is why I built an electric earth auger (see photo below). I think I can actually do 25 foot holes. The auger shown on the photo uses a quarter-horse drill motor (187 watts) and a 25:1 gear reduction. I didn't get very far drilling dry, then I discovered using drilling mud which required using a pump to send drilling fluid down the hollow drillling pipe. This of course required making a drilling fliid swivel arrrangement, and a drilling fluid recirculation system. I discovered the drilling mud secret late in the summer, and it greatly improved my success, but then cold weather overtook me and I had to stop.

My gearmotor auger, at a quarter horse (187 watts) is really absurdly small. Most homemade augers are in the range of five horsepower (3730 watts) or bigger. Here in Portland, Oregon the ground is very difficult to drill. Lots of big rocks deposited by glacial deposits during the last ice age. However, even though it's slow, hard work, I have gotten down to 17 feet. If worse comes to worse, I can succeed with a loop filed that consists of 18 holes that are 17 feet deep each. In the mean time, I'm scouting around for a larger gearmotor for my drilling setup.

Earth structure really has a lot to do with it. Even my tiny 187 watt gearmotor auger would do a great job if the earth conditions were favorable. About 30 miles from here, there is sand that goes down about 85 feet. If that were my case, I'd have been done last summer.

Oh, and I should mention that I made a T-handle hand-powered test drill, which used domestic water pressure to flush out the drill cuttings. I was actually able to get down nearly 12 feet. With favorable conditions, it would be possible to do the loop field by hand!

The photos:
Gearmotor-Auger-2(small).jpg - This is a close-up of the gearmotor auger showing the first swivel which didn't work very well. It had O-ring seals and so much friction that I lost almost 1/3 of my drilling power (which wasn't much to begin with). Also seen is a garden hose feeding the auger. With the soil conditions here, sand and not much clay, cave-ins were a problem after maybe 5 or 6 foot depth.

Swivel(small).jpg - Here's the second generation swivel which worked much better. Once I realized that I was going to need to use drilling mud, I started taking my swivel more seriously.Hhere I'm using 3/4 pipe skimmed down to fit 1" ID sealed ball bearings. A happy fit was that the OD of the bearings just worked inside the plastic T-fitting. The whole swivel cost was about $23. Commercial ones are $300 or so. The friction is almost non-existant. Works great.

transfer-test(small).JPG - Here I'm making a test hole to see what the rate of thermal transfer is from the earth to the water.

Best Regards,

-AC_Hacker

It's true that it takes a lot more energy to move a unit of heat in air than in water. For its mass and density, air is pretty viscous so it takes a lot of power to shove it around, and for that matter the conduits we have for moving it, unlike plumbing pipe, are generally pretty rough on the inside. If you could have it, about the best material for moving large volumes of air would be large-diameter PVC pipe - which is really expensive.

My smallest HVAC system here at work uses a 1/3hp motor for running the blower. Obviously none of this has been optimised for the best possible performance but it isn't the worst case scenario either. So that blower moves around 800cfm, which after a little math with a REALLY GENEROUS fudge factor equates to about 300 pounds of air per hour.

My largest water heater has a permanent circulator pump, in this case about 1/2hp so it isn't a direct comparison, but that's moving, assuming the lowest numbers on the scale, over 400 pounds of water per MINUTE. Now, you can't heat water to as high a temperature as air, but water's heat capacity knocks air into a cocked hat.

I've thought about projects like yours from time to time. The one I kept coming back to was, what if I got a small window-mount heat pump unit, detached its exterior coil and built a water box around that? Then just circulate your heat exchanger water from the ground loops into the water box. It's quick and dirty, but I don't see any big reason why it shouldn't work. You get to eliminate half of the fan noise from the AC unit by pulling off that outdoor fan, and redirect that fan's controller to operate the ground loop pump. Since the water is entering and leaving via insulated pipes, you can place the heat pump pretty much wherever you want it.

As you say, your mileage may vary.

elhigh,

> ...what if I got a small window-mount heat pump unit,
> detached its exterior coil and built a water box around that?
> Then just circulate your heat exchanger water from the
> ground loops into the water box.

I think it would really improve the efficiency of the unit, you should do this!

I actually considered making a water box around the air heat exchangers also for my project, but I intend to use this to heat my house, so I took the route I took.

A couple of things you might consider, the amount of tubing and fins, etc that the air exchanger uses is way bigger than you need, it will still work, though. I've been looking for some rule-of-thumb that I could use to make a switch from air to water, so I'd know where to start. I seem to recall that I saw on some boat refitting blog, someone saying there was a 50:1 difference between tubing in air and tubing in water. A buddy of mine is fitting a small refrig into his boat and using a condenser that is actually in contact with the ocean water. He said the condenser tube was only a few inches long for his refrig. So maybe the 50:1 ratio is close.

Another thing is that if you plan to use this unit for a long time you could get stuff growing between the fins, in which case you might need to carefully remove the fins all together, to prevent fouling.

Another suggestion is that your unit, however big or small it is will be putting out a surprising amount of heat, so you'll need to have sufficient pipe in the ground to absorb all the heat. The rule of thumb where I live is that a 200 foot hole is required to transfer 12000 btu per hour. Look on your AC to see what the BTU rating is. If, for instance it is 8000 btu, the equation would be:

Required Hole Depth= (8000/12000) * 200

So your hole would need to be at least 133 feet deep.

You could also use 10 holes, each 13 feet deep. They should be separated by at least 8 feet each.

The earth has a lot of heat to give or, in your case, to absorb. But it does it slowly on a per foot basis. So you need more feet of pipe in the ground to get the heat flow rate you desire.

But it definitely sounds like a worthy experiment that we can all learn from.

I'm currently working on a detailed post, spelling exactly how to convert an Air Conditioner or De-Humidifier to a working heat pump.

So stay tuned...

And best luck on Eco-Modding your AC,

-AC_Hacker





'

What if you did that with your fridge? That's been floating around in my head for a while. If you already have some kind of ground source piping in the house, then sticking the refrigerator's coils into that would not only raise its efficiency (as would external insulation), but would also add some extra heat to the source of your heat pump. In fact, you can go one step further and notice that the temperature inside the fridge is close to either the temperature of your ground source, or of the return, so why not put the whole fridge in a water jacket? No compressors, no coils, no noise.

I've also been wondering about how much heat can be stored underground? Say you dump your A/C heat into the ground during the summer. How much of it will still be there when you need it in the winter, and how much will dissipate? That probably depends on your climate. Here, heating season is 5-7 months, while A/C might be needed no more than 2-6 weeks. Say you have solar panels that help with heating or hot water, but which are too big for summer. Would it be worth while to pump the sun's heat into the ground all summer?

Piwoslaw,

I really like the way you are thinking about this.
_ _ _

Here are some books that are very informative on this subject:

heat-pump-book.jpg - Loads of info on GSHP design & installation. The approach is for forced air, whole house heating.

radiant-floor-book.jpg - In the US, this is considered to be the bible of radiant heating. I'm sure that better books are available in Europe. Has computer aided design software included.

Piwoslaw, if your friend's book addresses using GSHP + radiant floor, it needs to be translated into English.
_ _ _

First off, I think that many, if not all of the people on this blog realize that energy is getting more scarce and also if the energy we use has a fossil fuel or nuclear origin, we are directly contributing to global warming and/or degradation of our environment. Whatever we can do to reduce our burden on the planet is the right thing to do. It's a serious pursuit we have here, but it can also be great fun for us and inspiring for others.

> [using water to remove heat from the condenser] ...What if you did
> that with your fridge?

Any technology we invoke to solve a problem will start a chain of events that will lead ultimately to extractive processes, and there will be depletion, pollution and inefficiency all along the way. So first, let's see if there are 'low-hanging fruit' that are lower on the technology chain that will solve our problem...

* Do we need a refrigerator at all? Until a hundred years ago, people got along quite well without any refrigeration. People used the natural coolness of the earth to delay spoilage. Can we use a cool space in our house to keep fruits & vegetables in? Around here, many houses built 100 or more years ago used what was known as 'California Coolers' to keep fruits & vegetables in. This was a small cabinet-sized pantry built on the shady side of the house, with a vent to the outside at the top and bottom. For most of the year, it worked very well. No power required, no moving parts.

Here's a link to an idea for a cooler that won international recognition:
Pot-in-pot refrigerator - Wikipedia, the free encyclopedia
...notice that here, the heat absorbing property of water evaporation was used.

* Do we need a refrigerator all the time? This depends on local weather, but in my part of the world, winter time is six months long and rarely freezes. A metal box on the back porch works perfectly as a refrigerator. No power required, no moving parts. I'm the only person I know that uses this. When I tell people about this, they think I'm strange...I think they're strange. But without resorting to technology, I have reduced my refrigeration load by half.

* Is there existing technology that successfully addresses this problem? I have attached (0.1-kW-per-day_chest_fridge_2.txt) and (fig-1.gif) a detailed description here of a super-efficient freezer-to-refrigerator conversion. The link is on this site with a photo.
DIY, Super-Efficient Fridge Uses .1 kWH a Day | EcoRenovator.org
...this link is another approach to this...
Convert freezer to refrigerator | OliNo

* Are there existing building blocks I can use? Here's a link (Welcome) to a company that makes a pre-charged refrigeration system that can be connected to an air or water heat dissipation system.
_ _ _

...So getting back to your original ideas, my thinking about the earth as a heat source and a heat sink has shifted recently. Dry earth is a good storage medium of heat and cold however, water migrating through earth moves heat with it. This can be bad if we are trying to store heat because the water will carry our stored heat away. It can also be good if, for instance we are trying to extract heat from the earth, water migration will renew the heat in the earth.

If we assume that the earth is dry, then it can be imagined to be a giant storage battery, and any heat we put into the earth from a refrigerator, or a solar panel will be there for us when we need it.

> Say you dump your A/C heat into the ground during the summer.
> How much of it will still be there when you need it in the winter,
> and how much will dissipate?

earth-temp.jpg - this is a scan from the GSHP book. Note the reducing temperature swings as you go deeper. Also note the time lag (AKA: phase shift) of temp. swings as you go deeper.

Heat travels through dry earth pretty slowly. One study I read (Passive Annual Heat Storage - Improving the Earth Shelter) specified the rate at 16 feet per 6 months. So in your case, you could use underground loops to store heat during the summer and use the same loops to retrieve heat during the winter. The temperature or the earth at a depth of about 25 feet is just about the average of year-round temperatures. Most of the heat of the earth comes from the sun. In most cases, the heat from below is so small that it is of no consequence.

> Would it be worth while to pump the sun's heat
> into the ground all summer?

I have managed to pick up 10 solar heat collectors for an embarrassingly small amount of money. My plan is to use a small solar PV panel to run a pump during the summer to store heat in the ground. Here, we have bright sunny summers, plenty of sun, plenty of heat, and cold overcast winters with little sun, and temperatures hovering around 37 degrees F. Water migration may work against me, I won't know until I try.

I'm really interested in hearing more about your friend's book...

Best Regards,

-AC_Hacker

It is pretty common in the homebrewing craft to have a chest freezer with a temp controller. You use it to control the temperature of fermentation or the serving temperature. A cheap chest freezer and one of these controllers makes a high efficiency refrigerator that is also much cheaper to buy:

NORTHERN BREWER: Fermentation Temperature Control

I have the Johnson Controls A419 and a $100 chest freezer from Lowes, it is very dependable. I haven't run it on a KillaWatt so I don't know how much load it draws, but I doubt it is very much.

Here is a heat pump design that uses water stored in an insulated attic space to store heat. The heat is generated either by solar energy into the water and then vented into the living area, or if the stored heat is not warm enough, by a heat pump (air conditioner with the hot end pointed into the living area and the cold end pointed into the attic.

Thermal Attic - Solar Heating & Natural Cooling Systems

The designer frequents the "small houses" group on yahoo. There are some very well thought out design discussions there. If you are not already in the group, they would love to hear about your experiments.

About 20 years ago I read of a built-in refrigerator that used an ammonia absorption loop to cool a heavily insulated compartment. During the day, heat from the sun would drive the ammonia off the wet end of the loop outside the house, to a reservoir inside the cooler box. During the night, the ammonia would boil off from the loop inside the box and condense with the water. Next day lather, rinse, repeat.

This cooler design used about 1/2 kwh per year - to run the light.

If heat moves through dry earth at about 16' / 6mos, then the right place for your ground source loops is directly under your own basement floor, about 16 feet down. In the middle of January, all the heat you dumped in there for cooling back in July ought to be just about creeping its way back up to you -

I thought about doing the same. Before I got married we had a north-facing porch and I sometimes put stuff from the freezer out there when it was really cold. That was a good time for defrosting the freezer (our fridge and freezer were two separate units). Since we only opened the freezer once every few days this wasn't a problem. Using the balcony instead of a refrigerator wouldn't be that easy: first, the balcony was two floors higher than the kitchen. Second, I guessed that I would waste more heat opening and closing the balcony door a few times a day than what the fridge was actually using (it was the most efficient we could get then).
Now I live at my wife's and we also have a north-facing balcony, but the fridge and freezer are one unit, so whether one is empty doesn't make much of a difference. It's very efficient (rated A+, around 0.65kWh/day, compared to 1.25kWh for the previous unit), but gets opened quite often (see: Dad-in-law ;)).

Back to GSHP, I remembered another rule I came across somewhere: For every square meter of area of the building you want to heat there should be 4 meters of underground piping. Also, laying the pipes about 1.5 meters below the surface is supposed to be slightly better than deep drilling, under the assumption that that area of ground gets a lot of sun. 1.5 meters is about how deep the sun's heat penetrates, but is also the the freezing depth. Of course, the difference isn't that big, but if you have a sunny southern slope next to the house, it'd be sin to start drilling instead of digging.

Polyethelyne Welding...
 

Please see new post over at the EcoRenovator site:

The Homemade Heat Pump Manifesto - EcoRenovator

Best Regards,

-AC_Hacker

Piwoslaw,

I'm curious about the rule which says: 4 meters of pipe for every square meter of building.

Obviously this ignores the heat loss characteristics of the building, it also ignores whether the system uses heated forced air or radiant floors, and if radiant floors, whether the piping is embedded in concrete (feed temp = 90 F), is embeded in non-concrete material on top of the floor (feed temp = 100 F), or is fastened below the floor (feed temp = 120 F). It also seems to ignore whether the ground-source piping is in boreholes or is in trenches, and if in trenches, how is it arrayed? As slinkeys? as parallel pipes? So many things to consider...

Where I live, the rule of thumb (which ignores all the above factors, too...) is for every 1000 square feet (93 square meters), you'll need 12,000 BTU/hr (3517 watts), which requires about 200 feet (60.96 meters) of borehole, or about 80 feet (24 meters) of trench, with about 320 feet (98 meters) of pipe in the trench. I may have errors in my conversions, but this is quite a bit different from the rule of thumb you are suggesting. I do realize that I live in a mild climate and that it gets pretty cold in Poland...

Regards,

-AC_Hacker

P.S: There are some new posts about polyethylene welding and also proceedure for testing a borehole for thermal transfer rate over at this link:
The Homemade Heat Pump Manifesto - Page 2 - EcoRenovator

Hey, finally registered cause I wanted to add my 2 cents about your ground-source heat/air plans. The past year I've been helping install a commercial level ground-source system. I'm not a HVAC tech or engineer, so take my suggestions with a grain of salt (or a shaker full): I can only say "thats what we did here." (in Texas)

About pumping heat into the ground, I would think that would be worthwhile if your main demand is heating. Here in TX, the main draw is AC, and some systems will have "dry coolers" to pump excess heat out of the system during the winter; because the temperature of the system water (closed loop) creeps higher and higher due to the high AC demand relative to heating.

Our borehoeles were spaced 20ft apart. The greater spacing will likely help increase the amount of heat that can be stored. If it's just one or two rows, the spacing may not matter as much as in our case where we had 230 boreholes in the space of about a soccer field and a half!

Just left a post there about my experience and recommendations for polyethylene welding.

All these different threads got me confuzzled: I'd been reading both this thread and that one (@ ecorenovator). I finally decided to register at ecorenovator to reply. I made the post about poly welding then went looking for this thread to reply to it. After checking my browser history, I finally found it here at ecomodder.:confused: Oh well, I guess the excuse was needed, I've been lurking here long enough. :thumbup:

Hi guys
I have looked over your thread, the threads in twister and some others. I am a commercial industrial HVAC tech for 25 years and tough it for about 10 years in the evenings. I have enjoyed watching what you and others are doing. some times I'm impressed, some times I shake my head and some times I'm just scared. I am looking to build my own Geo heat pump unit by cannibalizing my air to air HP. I have seen some comments elem ware referring to the so called secret info in this info. Please do not believe this is true, I think most techs would love to share there knowledge. the reason it seems they play there cards close to there chest is: it is a very technical field That takes a extensive back round including the laws of thermodynamics, physics, chemistry and electricity theory. this does not mean that the common man cant do what you are doing, but to make it work well and last you Need a few things under your belt. I think you guys can do very well be cos you have desire the #1 thing to synced.
I have held off interjecting be cos there is no short way to learn well the vapor compression cycle and the other things involved. I hope to make a write up that will be usefully some day. for now, till I come up with some thing I will answer your questions if you are willing to share the knowledge you have.
although I have lots of experience with water source heat pumps and water cooled units I am looking for the info for the ground source loops.
Paul

Paul,

Welcome to the conversation.

When I started this "manifesto" thread, I had in mind that it would be a kind of 'open source project' where people could share their knowledge. So, when folks like you join in, it is very encouraging.

I'm not sure if you know that although this is where I started this project thread, it's moved over to the sister blog:
The Homemade Heat Pump Manifesto - EcoRenovator
...it was driving me crazy trying to double post and remember what was said and where.

Anyway, on the other blog (above URL) there's a ton of additional info.

And I'm figuring this thing out as I go along, so if you see things that need correcting, let's get things cleared up.

> ...I am looking for the info for the ground source loops...

The best source of info I have found is the IGSHPA book, "Closed-Loop Ground-Source Heat Pump Systems: Installation Guide". It's not cheap, and I wasn't able to find a copy that was used that was much more reasonable.

IGSHPA manuals are here:
Publications | Manuals

What I've been able to determine is that there are different ways to get the Ground Source heat. Some are cheaper than others. ranking from cheapest to most expensive goes something like this:
1) Closed Loop Pond
2) 'Open Loop' pump & dump systems where you take water out of an aquifer and dump it back to the aquifer or to a river or use it for irrigation.
3) Trench type systems using a 'slinky' arrangement or a linear pipe arrangement.
4) Closed-Loop boreholes.

Geology or lot size may make one of the choices the only choice that will work.

So, I live on a 50 x 100 city lot and don't have enough room for anything except drilling down. I can't affford to have a professional do it, so I'm trying to do it all myself.

Sizing the loop field is a matter of knowing what your building heat load is and knowing what the thermal transfer characteristic of your particular soil is. On the other blog, I set out how to test your own soil to determine what your heat transfer rate is.

Thermal Test URL:
The Homemade Heat Pump Manifesto - Page 2 - EcoRenovator
...post #18...

So, for me and my small house, I'm figuring my house's heat load to be about 12,000 BTU/hr (a Ton).

In these parts (Portland, OR) the rule of thumb is that a borehole needs to be between 175 and 225 ft deep, per 12,000 BTU/hr. When I tested it, it came out to 214.23 ft. This would mean that I would need at least 214.23 feet of borehole. More borehole is better, and also more expensive.

I have heard that around here, a 5 foot deep by 3 foot wide trench with 300 feet of slinky loops would get you about 12,000 BTU/hr.

I also found out that the material of choice for loop fields is High Density Polyethylene (AKA: HDPE). Many states are insisting that all joints be heat-fused (AKA: welded). Installers guarantee these for 50 years, but the general agreement is that they'll last a couple of hundred years, or more.

Here's product information from a typical HDPE pipe provider:
http://www.superlon.com/supertherm.pdf

There are also considerations of providing flow turbulence, to improve heat transfer. The IGSHPA manual covers this.

Here's a link to a brief blog discussion on the subject of flow rates:
http://www.eng-tips.com/viewthread.c...227114&page=10

PVC pipe is not recommended because it gets brittle with age. I have read, however, that the first GSHP developments did use PVC. I don't know if all of the PVC installations failed, in fact, I don't know if any of them failed.

I have also heard stories about how "a neighbor buried garden hose in the back yard to heat his house". I have no way to verify the information as to whether this will actually work.

I do recommend experimenting.

I also recommend being aware of standard methods, if for no other reason than it can suggest a starting point.

Here's Washington state's standard:
http://apps.leg.wa.gov/wac/default.a...te=173-160-453

Here's from Lancaner county Pennsylvania:
http://www.co.lancaster.pa.us/planni...p?a=3&Q=268236



Does this help?

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

And I do have a question for you:

I have this little 400 watt compressor, and I'm trying to size a pair of flat plate heat exchangers for it. By my reckoning, it will move about 1600 watts (about 5500 BTU/hr), steady state. I'll be pumping water in at maybe 47 degrees into it on the Ground Source side, and I'll want in the neighborhood of 5000 BTU/hr out on the hydronic floor side. I figure I'll run R-22 or similar refrigerant. I'm not trying to heat my whole house, just a room that needed about 4000 BTU/hr on the very worst day last winter.

I threw one together last summer and it worked pretty well, but I'd prefer to have a better idea of what I'm doing.

Do you have charts or sizing programs that you like to use?

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
NOTE: While waiting for a reply, I found what appears to be a pretty good brazed plate selection program. Found here:
http://www.flatplate.com/resources_SOFT.htm
...choose the "Refrigeration Heat Exchangers" option.

The specifications for ebay-available brazed plates is pretty much non-existent. There is some vague mention of BTU transfer for solar-heating.

Problem is that refrigerants have a very different specific heat, compared to water. So I Thrashed around through several brazed plate selection guides and found that for refrigeration purposes, both evaporation and condensing, heat-transfer seems to work out to about 5000 BTU/square-foot for small exchangers.

So the formula might look something like:

Heat = ((width) x (length) x (# of plates - 2)) x 5000

...where width & length are expressed in feet.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Best Regards,

-AC_Hacker

Hey Piwoslaw,
There actually is a website and formula for using the earth in a big half-ball shape(insulated underneath the ball) then building new purpose-built eco-housing on top of it. I think the size of half-ball and how deep it went depended on location and size of house. As I recall, heat was dumped into the earth storage in the summer and heat was drawn back out in the winter. This pretty much made for an average temp all year round if engineered right. Perhaps I can take the time later to research my extensive bookmarks and come up with the website.
take care and stay warm/cold-average! Tinkerbill (new member from Yahoo wastewatts group)
PS: sorry I forgot to use the quote function. Newbie mistake.

URL please...
 

tinkerbill,

This sounds like an interesting web site. Your description left me wanting to know what the URL was.

I'd sure appreciate it.

BTW, bein's as how you're a fellow portlander, I'd be curious what kind of Eco mods, hacks or improvements you've implemented.

Regards,

-AC_Hacker

Passive Annual Heat Storage & Homemade Heat Pumps
 

tinkerbill,

Thanks for the URL's.

Regarding the book you mentioned, I have a copy of that book. It sets out the theory of PAHS pretty well, but doesn't really give you plans for building your own PAHS hous, but they do have plans for sale.

The Beaverton Library has a copy. I'd say it is well worth reading, even worth giving your scanner a heavy workout.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
NOTE: This blog string started here, on EcoModder. It was suggested to me that it might better belong here:

http://ecorenovator.org/forum/projec....html#post2631

...so I made that change. You might want to want to read both blogs, but the real action is happening at the above link.

Best Regards,

-AC_Hacker
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

What about having the back side of your fridge/freezer through a wall or sliding glass door that you don't use in the winter? You would never need to "let cold air in" but would gain from having the great outdoors cool your food.

Cheers
Ryan