The Homemade Heat Pump Manifesto

[charlesfl]

I live in Florida near Pensacola where the soil is sandy and the ground water is high. People here water their lawn with fresh water using a shallow well pump.

I am building a GSHP with a R22 condenser heat pump I got from Craigslist and a shallow water well with pump and dump technology for now.

[charlesfl]

I have my well drilled to 40 feet and currently designing the heat exchanger.

Thank you AC_Hacker, Ecorenovator, and all other contributors for the excellent information and documentation.

charlesfl

[AC_Hacker]

Originally Posted by charlesfl

I have my well drilled to 40 feet and currently designing the heat exchanger.

charlesfl,

Congratulations on your thermal well!

Near Pensacola, are you? I lived for a short time, not too far from Fort Walton Beach, so I'm quite familiar with that sand.

It would be very useful if you could share some of the details through descriptions and photos, if you took them, of how you went about drilling in sandy soil like you have there. I know that there are other folks who read this thread, and are from the sunny, sandy South.

Your experience could help others, with similar soil conditions, to also be successful.

My guess is that you used drilling mud to keep the sand from caving in on your drill string. But you may have discovered an easier way to do it.

Fourty feet deep is pretty darn good.

I'm also very interested in how you are going about designing and making your heat exchanger. I think that is probably a difficult part of the project for very many people.

How many Tons of cooling are you expecting from your unit?

I assume that you are going with an air handler for inside your house, although circulating cooling water through ceiling panels would be another approach, if you could find a way to control the condensation problem. I have read quite a few accounts of the use of ceiling panel cooling in European office buildings. Apparently they use humidity sensors (and I would assume de-humidifiers, too) to modulate temperature/humidity so that the dew-point is not reached... otherwise, it would start raining inside.

Anyway, good luck on your project!

Best regards,

-AC_Hacker

[AC_Hacker]

This is a response to a question that originally appeared on the R-290 thread, but I thought it would be good to post it here...

Originally Posted by Geo NR Gee

We are preparing to use the R290 (22a) in an outdoor ASHP soon, I need to figure out the amount to install.

According to the Enviro-Safe instructions: Each ounce of Enviro-Safe 22a Refrigerant is equivalent to 2.5 ounces of R22. That would mean a system that normally holds 200 oz. should now be evacuated and filled with ____oz.?

This should be a simple math question. I think that you take 200 oz. divide 2.5 = 80 oz.

According to the folks at Enviro-Safe, I should also check the pressure from the manufacturer and match it to that.

Next is to research the proper method of removing the old R22......

Wow, 200 oz of R-22 is 12.5 pounds... that's a lot of r-22.

Your conversion from R-22 to R-290 or Enviro-safe is correct, but it's still 5 pounds of hydrocarbon refrigerant, so play it safe.

Regarding pressure, I found that when I used R-290, the pressures required to get good performance were actually much less than the pressures called out for R-22.

For instance, when the R-22 pressures were:

• Hi side = 400 psi
• Lo side = 250 psi

I was getting good performance from R-290 at:

• Hi side = 200 psi
• Lo side = 125 psi

...sometimes even lower.

I started with the same pressure for R-290 as were called out for R-22 and when I ran my compressor, I didn't see any evidence of the miracle of refrigeration taking place... in face I was completely crest fallen and was sure that I was a complete failure until I reduced the pressure way down.

The unit had a very slow leak and ran my compressor through several days with the vacuum gauges attached and got to see the range at which the setup would work... it was very interesting.

I also did some efficiency tests over that range, and that was even more interesting.

Another thing, when I was hacking my unit I changed out both HXs, and the overall system volume was significantly changed, so I couldn't rely on weight of refrigerant... I had to go by pressure and performance.

-AC_Hacker

[sparkchaser]

Hello all,
I was wondering about that! I had read somewhere the pressure and quantity were less than R-22, but I didn't know just how much!

[randen]

This past weekend the homemade GSHP was installed. As you may remember the shop is about 1800 sq ft. and insulated well. The office area is aprox 600 sqft with infloor heat and the balance shop area is to be heated with a air- handler. The heat pump was built around a 2 Ton air-condition compressor. In the test phase it put out about 18KBtu/H. For now the ground loop only has water in-case we decide to change to a 3.5T compressor unit it will be less of a mess. The numbers are as follows: Incoming ground loop temp 55 deg F Out to ground loop 53 Deg F. By these numbers the flow rate is good. The temp out from the GSHP to the shop air handler and infloor heat is 82 Deg F return is 72 Deg. After running for the whole day (8 Hrs) with an outside temp 34 Deg. the shop only made it to 62 Deg F. The office floor only 66 deg. The air handler is putting out air at 78 Deg F. I'm going to let it run through the night 24 Hrs to see if we have maxed out. The electrical energy in is a whopping 1290 watts. If we can make 76 deg in the shop and or infloor temp. I can live with that otherwise a larger source will be needed. If I could ask AC Hacker; do you run your GSHP continually? and what performance do you see.

Randen

[AC_Hacker]

Originally Posted by randen

If I could ask AC Hacker; do you run your GSHP continually? and what performance do you see.

Good question... Just about every aspect of my setup is different than yours (except for the propane), so it's definitely comparing apples to oranges.

Last winter I did a test run, to see how the heat pump and the loop field were working together. I didn't have any kind of thermostat for most of the run, so I left it on, 24/7. I used an automobile radiator for an air handler, because that was all I had, and I put a box fan behind it, blowing on 'medium' speed. I ran the test in my basement which is pretty small, 24 x 15, and the basement has no insulation at all, I haven't done any rigorous air sealing, and there was an opening in the basement to a crawl space that was 16 x 16, no insulation. I would say that only 180 square feet of the 616 square feet of the ceiling in the basement (and crawl space) had directly heated space (70F) above it. The rest of the cieling space was only heated by the heat that leaked out of the heated space (37F to 55F). I was using a loop pump that was moving about 2.3 gallons per minute. My compressor is really miniature, it came out of a 25 pint per day de-humidifier, it draws somewhere in the neighborhood of 400 watts. My conservative guess is that it was putting out around 4000 BTU/hr.

Having said all that, it took about three days for my basement to go from it's usual low 40s temperature (for that time of year) to around 60F degrees... which I felt was not an unreasonable temperature for a shop. There was a lot of variation in my basement temperature during that time, partly due to ambient air temperature (I think because the space is almost all underground, this was not so important), and partly due to the effects of the loop field temperature during this test. Because I live in the Pacific Northwest, rain that has come off the Pacific ocean has a major effect on local weather. I noticed that rainfalls carried a lot of heat, and when the rain fell on the ground, that heat passed into the ground, and therefore affected my loop filed temperature in a positive way, and had a noticeable effect on the performance of my heat pump and on the basement temperature. I also learned that a warmish rain would not register in the loop field temperature for maybe three days, but then as it worked it's way down through the ground, I would see an up-tick in loop temperatures and also basement temperatures. an up-tick in loop temperatures might be in the neighborhood of 1 or 2 tenths of a degree, but that would mean an up-tick of maybe 4 to 6 degrees in the basement. At one point, the basement hit 73 degrees and felt uncomfortably warm.

(* It was about this time that I broke my arm quite badly, so not much has been done since then. *)

So, I don't know if this is what you wanted, but this was how it was. Because I was using air out, I wasn't sure how to measure performance quantitatively... I just went for experiential knowledge.

Regarding your system, I would suspect that your air handler is on the small size... this kind of gets back to my rant about low temperature heating and hydronic floors and how low temp heating needs optimized floors and large radiating areas, and all that...

I forget exactly what you said about your air handler, I seem to recall that you may have said that you converted it from another type of fuel source to what you are presently using.

At any rate, I have read quite a few accounts about people who have plumbed a heat pump into an air handler that was originally meant for fossil fuel, and were disappointed by the results. The reason in that situation is that fossil fuel yields much higher temperatures, so an air handler with a smaller area will work, but if you try to use the same air handler with a lower temperature heat source, it will not put out heat at the same rate.

I think it should be pretty easy to see if this could be a remedy for you, you could hook up a few car radiators with fans, in-line with your regular air handler to see if it made any improvement.

Another thing to look at is testing and tweaking your heat pump to get maximum performance. Have you looked into subcooling & superheat?

Here's a document on it...

Another approach would be to run a series of your COP test like you did before, and try tweaking your TXV and also refrigerant pressure level to get maximum heat output... which might be a different 'tuning' than what you'd get with a maximum COP 'tuning'...

And, lastly, you may be right, you just might need a bigger compressor.

I hope this has been of some help...

-AC_Hacker

[randen]

I had left the GSHP purr away all night. The office floor temp made it to a solid 75 Deg F. The shop area never made it past 62 Deg F The overnight outside temp dipped below freezing with some wind. The ground loop temp didn't change. Although the shop is comfortable enough now but when winter takes a big dip I don't think it will remain so. As AC hacker had suggested I played with the amout of refrigerant charge.With the gauge set installed and the amp meter as well as a digital temp probe on the highside tube a temp of 176 Deg F was read. Adding a little propane slowly got me to 179 Deg F the current draw didn't change much the high side pressure rose 10 psi. As more propane was added the current rose to 7.5 A and the temp dropped. As I removed propane the temp peaked and then dropped again and the current dropped. The sweet spot is 210 psi High 45 psi low 6.4 A and 179 Deg F out to the HX. Well it looks like the verdict is in, we need to step up to the 3.5T compressor. Thanks for the help and inspiration

Randen

[AC_Hacker]

Originally Posted by randen

Well it looks like the verdict is in, we need to step up to the 3.5T compressor.

I hope you're not planning to cannibalize your original heat pump...

You could use it for the 'shoulder season' and use the 3.5T for serious heat.

I really like your 'current draw/temp out' approach to optimizing your refrigerant charge, very clear and to-the-point.

Best,

-AC_Hacker

[rhino 660]

look here,
you guys had said something about making your own socket fusion ends
these are replacement faces.

Socket Fusion Faces : TLSF : Tools and Accessories : Geo-Hydro Supply, Ltd.