The Homemade Heat Pump Manifesto

[Ko_deZ]

From what I can see from the drawing, this geocoloumn will not be very efficient. The volume of dirt it is in close connection to is not very large compared to the size of the unit, and the way they have different height of condensers that all gather to one will give a higher return temperature than if they used only one coil going all the way from top to bottom. Also, it will only be useful for cooling as mentioned above. It does not seem to me like this would be a good solution except for areas with a thick enough layer of loose ground to avoid drilling in rock, a high ground water level, and rapid movement of ground water _and_ a very limited area avaliable. Anything else would be cost inefficient compared to other solutions.

[AC_Hacker]

Ko_deZ,

Could you re-check the data you provided to me regarding the Chinese heat exchangers?

I was able to get to the web site (very, very slow to load), but when I sent them an email, it took nearly three weeks for the email to bounce back "undeliverable".

Sincerely,

-AC_Hacker

[Ko_deZ]

Hi.

I did a re-check, and the e-mail I have used is hralehx@gmail.com. Unsure what I posted earlier, but this e-mail address is a gmail address, so it being very slow to respond as undeliverable is strange. Hope you get hold of them. I am about to put together my heat pump as you might have understood from other threads, but have been held up by good weather. This time last year we had snow and -5C (about 23F?) peaking at -10C (14F?). Todays nice 10C (41F?) is a very welcome surprise, and very useful to get things done outside the house.

[AC_Hacker]

Ko_deZ,

Could you re-check the data you provided to me regarding the Chinese heat exchangers?

I was able to get to the web site (very, very slow to load), but when I sent them an email, it took nearly three weeks for the email to bounce back "undeliverable".

Sincerely,

-AC_Hacker

[randen]

Its been many weeks but the heat pump is working and in test mode. The GSHP has been constructed using re-purposed items. The compressor was a 12 yr old air to air conditioner. It was used gently maybe only 20 weeks total. The heat-exchangers are home made copper shell and tube with a special 4 way valve that would only switch between ground loop to air handler and always maintaining a counter current between the refrigerant and glycol through the exchangers. The total cost was about $300.00 for fittings and tube insulation. Most of the other materials where scrap pcs. The coils of copper where donations from a friend cleaning out the garage. Condensor is 3/8 tube surrounded by 7/8 tube about 25ft Lg while the evaporator is 5/8 tube surrounded by 1" PVC tube used for hot tubs. The counter flow shell & tube exchangers work very well. Refrigerant temps leaving the exchangers are only 2-3 deg. of the exitting glycol. The refrigerant used is propane and seems to work well. The pressures are comparitively lower than the R22. The test was with 20 gals of water each, heating one and cooling the other over 1/2 hr. Two intervals of 15 min each. The results (maybe I can be corrected) but 180 lbs of water heated through 25 F deg rise is about 18 KBTUs and the second interval only an additional 20 F deg is about 16.5 KBTU. The ending temps of the barrels was 37 F deg and 88 F deg. There may be a little discrepency metric to imperial conversions plus the additional heat from the compressor. The down side if there is any is I don't believe that the maximum 18 KBTU will keep the shop warm for the winter. Judging by comercially avalible units of 24 KBTUs (2T)the heating out-put is whats expected. The up-side is I have a 3.5 T that can easily replace the smaller compressor. Both the condensor and evaporator tube & shell exchangers can be cut and lifted off the compressor. Its made a nice compact unit 18" high X 24" dia. One nice thing is the insulation on the exchangers act as sound dampining. If the HXs can handle the extra energy I'm sure 3.5T will warm the shop.

[Geo NR Gee]

Thats a cool 4 way valve. Can you tell me more how it works? I am a little slow (a lot).

[AC_Hacker]

Originally Posted by randen

Its been many weeks but the heat pump is working and in test mode.

Randen,

You totally rock!

That is really a great-looking rig you have made there, from the coiled tube-in-tube HX to the 4-way valve.

Very respectable numbers, too on your test run.

This just goes to show that you don't have to be a rocket scientist to do this stuff... but it clearly helps to be an accomplished machinist.

Great going!!

Best Regards,

-AC_Hacker

[randen]

Thankyou A/C Hacker

If it was not for your successfull experimentation I would have just submitted to buying a GSHP. I had run a test on the comercial (ClimateMaster) installed in my home. It is a 3Ton unit water to water with a 60 gal buffer tank. The begining temp 27C to 43C in 45 min gave me a result of 18360 BTU/H This is just slightly better than the 2 ton (18000BTU/H) I had just completed. I believe the Propane Refrigerant may have something to do with this. Some others have indicated that they had realized a 20-30% increase in effiency with the introduction of propane. Based on the comparison I will continue to install the 2 Ton GSHP into the shop. The shops heating load would only be 3/4 as much as the house. It should be more than adequate. The proof will be that cold Canadian north wind moving in soon.

Thanks to all Randen

[AC_Hacker]

Originally Posted by randen

Thankyou A/C Hacker, if it was not for your successfull experimentation I would have just submitted to buying a GSHP.

Thank you! Your success, and the success of others is why I'm doing this.

One design detail you may want to keep an eye on...

In the photo below, is an old style refrigerator called a "Monitor Top". They were designed, similar to your heat pump with a HX surrounding the compressor. In their case, the HX dissipated heat from the motor. The compressor itself was very heavy, and was firmly bolted to a cast metal structure that was the top of the refrigerator. The HX was rigidly attached to the compressor body... no wiggle room. The vibration was damped by mass. Monitor tops were very heavy (I had one).

When I saw your setup, I thought you might have been inspired by the old monitor tops.

The reason I'm bringing this up is the matter of vibration. As you probably noticed, your compressor sat on rubber feet, to isolate the compressor's vibration from the compressor's surroundings. Modern practice is to let the compressor vibrate, and to give it plenty of wiggle room.

Here is a photo of a small air conditioner compressor...

Note how the tubing is bent in a "U" shape. You'll see this feature in just about any vapor-compression machine you look at. I don't think that the reason is for any kind of P-trap as is found in plumbing. I am convinced that the extra tubing is there to reduce the angular flexing. By spreading the flexure out over more tubing length, the flexure angle is reduced, and so is the stress. Thus the tubing would be less affected to by the compressor's vibration.

I have also noticed rubber spacers, strategically placed between some of the tubing runs, to dampen any resonant vibration tendencies of the tubing itself.

So, you might want to keep a critical eye out for indications of stress-causing vibration... Hopefully, it will not be an issue.

Best Regards,

-AC_Hacker

[Geo NR Gee]

Originally Posted by AC_Hacker

This just goes to show that you don't have to be a rocket scientist to do this stuff... but it clearly helps to be an accomplished machinist.



-AC_Hacker

Homemade valve? HMMM