The Homemade Heat Pump Manifesto

[AC_Hacker]

Originally Posted by Daox

Sounds like a good idea, but some of your pictures aren't showing.

Daox,

Which pix are not working?

I will fix.

Regards,

-AC_Hacker

[Daox]

The ones in the link you posted. The second, third and fourth pictures I get red Xs.

apppended loop spacer tube details

[AC_Hacker]

Originally Posted by Hugh Jim Bissel

Looking awesome!

Since you're running your loops in series you wouldn't need more than a send and a return temperature which you could read at the inside unit. If your loops were in parallel having a send and return on each parallel leg would allow you to verify each leg was providing equally.

Having more sensors than that (ie send and return on each well in series and/or every 2 feet) would be cool to have to see HOW it is working, but would be unneeded for anything except additional info. The main send/return temp change (and actual water temperature) is the big thing.

Looking forward to seeing it in action!

HJB, good to hear from you again. I was beginning to think that you'd been raptured into polyethylene fusion heaven or something.

By the way, the info you shared on poly fusion in previous posts was very helpful. The little poly fusion paddle I made worked out great and the temps you suggested were really close to what ended up working for me. As I recall, you were using temps around 500 degrees F, and I ended up using about 475 degrees F. As I recall, the pipe you were welding was much larger than what I was using, and would surely call for more heat. The jig I used to hold the pipe worked too, but it was clear to me that the precision gripping and alignment and steady pressure features of the pro equipment are definitely there for a reason. I did use the water + pressure test as you suggested on every weld, and I'm glad I did. Thanks for your input.

But I sure had plenty of time to think about the fine points of loop field design and how my 17 foot deep loops might work out...

I thought about this diagram, from the Closed-Loop/Ground-Source Heat Pump Systems Installation Guide (which I think is manditory reading for anyone who is contemplating Ground Source Heat Pumps):

This diagram is most likely taken from soil characteristics around Stillwater Oklahoma, but the principle is still the same.

My little loop field is operating in the 2-17 foot range as shown in the diagram. I imagine the fields you worked on were operating in the 4 -200 foot range, where temperratures arre much more stable, annually.

I thought about the effect that the connecting piping had on the performance of the whole array. If I assume that your boreholes were 200 feet deep and were on 20 foot centers, then the connecting pipe's length as a percentage of the vertical pipe length is 10%, not such a big percentage. In my case, my boreholes were 17 feet deep and on 12 foot centers, so the connecting pipe as a percentage is 70%, a much larger percentage.

I measured the temp of the earth just after trenching and my August temp at 2 feet was 60 degrees. The temp at the bottom of my boreholes in August was 53 degrees. That's a temp swing of 7 degrees. I'm guessing that the temp at the bottom of my boreholes in Janurary will not be terribly far from 53 degrees and I'm guessing that the Janurary temp swing will be 7 degrees colder, or at the bottom of my 2 foot deep trenches will be the same amount colder. or about 46 degrees F.

So after wrestling with all this, and not being able to find any existing data on the annual temperature swings of Portland soil at various depths, I just made a wild *** guess that it would be a good idea to insulate my connecting pipes to reduce the effects of surface temp flucuations.

I further thought that the temps of the water coming out of the heat pump will be pretty chilled and that 46 degrees F might look pretty warm at that point, so when I insulated the connecting pipes, I did so on the back half (returning) part of the loop.

I've never heard of anyone insulating the connecting pipes, but it seemed like a good idea at the time.

So, yeah, I really would like to know how a loop field is functioning at various points in the loop and at various depths.

This should be interesting.

Best regards,

-AC_Hacker

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[Hugh Jim Bissel]

Originally Posted by AC_Hacker

HJB, good to hear from you again. I was beginning to think that you'd been raptured into polyethylene fusion heaven or something.

No, afraid not. I've been keeping up with the project via the update emails, but school's been keeping me busy.

Originally Posted by AC_Hacker

As I recall, the pipe you were welding was much larger than what I was using, and would surely call for more heat.

It did, but through a longer time on the iron, not a higher temperature. We may have been running a little hotter than spec, though that didn't seem to affect the joints -- not even when the thermostat on the iron stuck on: did a few joints at 600+ until we figured out what was up and got a new iron, just had to drop the heating time!

Originally Posted by AC_Hacker

I thought about this diagram, from the Closed-Loop/Ground-Source Heat Pump Systems Installation Guide (which I think is mandatory reading for anyone who is contemplating Ground Source Heat Pumps):

My little loop field is operating in the 2-17 foot range as shown in the diagram. I imagine the fields you worked on were operating in the 4 -200 foot range, where temperratures arre much more stable, annually.

Yeah, our cross trenches were about 4 ft down, and the boreholes were 250 ft. Completely agree the GSHP install guide is mandatory reading for anyone even thinking about doing their own install, and not a bad idea to read it even if someone else is doing your install: make sure they do it right, cause not everyone does!

Originally Posted by AC_Hacker

I've never heard of anyone insulating the connecting pipes, but it seemed like a good idea at the time.

Interesting indeed! When you say you insulated the connecting pipes on the returning part of the loop do you mean from the last well to the building, or more than that?

Couple of questions/thoughts: Were you planning on running some kind of antifreeze in the water: (You are in the north, right?) Cause if you're pulling out more heat than you're putting back you're ground temp will drop. As surrounding heat moves in the temp should stabilize, but if you're starting at 46, freezing is not that far away. (installation guide discusses antifreeze solutions in Append A).

You'll have to see what your water temperature does season to season to know how well it's working (1st yr or 2 even the worst designed system will do fine). if your primary load is heating, you'll be wanting to get as much heat in the ground as you can, so you might look into putting your fridge on the system as well! (and depending on if and where your temp stabilizes will determine how much heat you need to add: ie solar hot water heater vs running the AC with the windows open for a day or two.

What were your plans for purging the air out of the wellfield? I'd suggest plumbing in valves so you can borrow/rent a bigger pump to get all the air out of the system, which your circulation pump may or may not be able to do.

Also just a thought, if you're feeding more than one unit inside you might go with one main (and backup) pump rather than a pump on each unit: we've had issues with "pump packs" (smaller 1 unit pumps). So if you don't have a plan in stone already, you might consider a few large, rather than many small pumps. (though that brings up other issues like what happens when the units are off: do you flow water through the coils or close the unit off and slow down the pump....)

Got to run, but I'll try not to be such a stranger.

[Nikolai]

Hello to everyone,
this is my first post here although I follow this idea and similar forums.

Regarding isolation, do not forget to underground pipes draws heat from the earth at a depth below about 1.5 m, while all that is shallower than that is above the "frost line".

This means that theoretically you should insulate pipes to a depth of 1.5 m, but in practice I think that is enough to isolate less, likely to 1m depth max. Of course, all parts of the pipes that come from the soil should be well insulated, and separated each one of other.

For this purpose, Styrofoam or similar can be used ...

[GvilleRenovator]

Welcome Nikolai!

Originally Posted by Nikolai

Regarding isolation, do not forget to underground pipes draws heat from the earth at a depth below about 1.5 m, while all that is shallower than that is above the "frost line".

YAY no frost line in Florida!

I did plan on doing my best to keep everything 3 feet deep or more though.

[AC_Hacker]

Originally Posted by Nikolai

Hello to everyone, this is my first post here although I follow this idea and similar forums.

Welcome to the discussion Nikolai!

Originally Posted by Nikolai

Regarding isolation, do not forget to underground pipes draws heat from the earth at a depth below about 1.5 m, while all that is shallower than that is above the "frost line".

This means that theoretically you should insulate pipes to a depth of 1.5 m, but in practice I think that is enough to isolate less, likely to 1m depth max. Of course, all parts of the pipes that come from the soil should be well insulated, and separated each one of other.

For this purpose, Styrofoam or similar can be used ...

I agree that the pipes should be as deep as is reasonably possible. And I also agree that they should be below the frost line.

Where I live, the frost line used to be 18 inches (about 0.5 meter), but now it has been re-defined as 9 inches (about 0.25 meter). So, compared to some other parts of the world, it doesen't' get very cold here.

You didn't mention where you live in your post Nikolai, but a frost line of 1.5 meters means that you must live pretty far North or South, or at a very high altitude.

Where do you live?

There is another reason why running pipes deep would be a good idea, and that is that they draw in heat in a circular pattern. So if they were deeper, there would be more area in the circular pattern to draw from.

Regards,

-AC_Hacker

[AC_Hacker]

Originally Posted by GvilleRenovator

YAY no frost line in Florida!

I did plan on doing my best to keep everything 3 feet deep or more though.

GvilleRenovator,

So, if you're in Florida, you're most likely looking to use your GSHP for cooling, right?

I'm in a more northerly location (W. Oregon) so heating is my primary aim. I plan to put in a radiant floor heating system because having that large area is very favorable for heast pump... A radiant floor wouldn't work for cooling, because water will condense on the floor and you'd have to contend with wet slippery floors all summer.

However, I recently read that the Germans are doing cooling by pumping cold water through the ceiling. The temperature of the water in the ceiling is regulated to be just below the dew point, so condensation doesn't happen. Apparently, having a very large heat absorber in the ceiling gives a greater cooling comfort level without needing to reduce the temperature of the air as much as is usually done.

Also, what is the situation regarding drilling & trenching? Do you have clay soil? Sandy soil? Big rocks? How many feet of borehole or how many feet of trench is required to get a Ton (12,000 BTU/hr) of HVAC?

Best Regards,

-AC_Hacker

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[Nikolai]

AC Hacker, have you considered a Dx variant of geothermal heating?

It can be done by direct burial copper pipes in the ground (cold end)...

[cold in Maine]

Hello AC Hacker! I am fascinated by your work! I also have an old house and have been researching geothermal heating, and I am a teacher and want to have students explore some of these ideas as well. Could you give me an idea of what you have spent on materials? I would like to try to duplicate some of your experiments and need to look into obtaining supplies. As I digest the postings further I will probably have more questions. Thanks for your work!