The Homemade Heat Pump Manifesto

[randen]

The air-conditioning operated though the night cooling the shop to 21.5 deg C. The morning out side temp 26.6 deg C. It would seam utilizing the ground loop only is very effective. The loop is 6 ft deep 2400' of tube with a 2' tube to tube centre distance in clay. Our location is rural north of Strathroy where they have a high water table and sand. The water table here is around 85' deep.

Randen

[AC_Hacker]

Originally Posted by randen

The air-conditioning operated though the night cooling the shop to 21.5 deg C. The morning out side temp 26.6 deg C. It would seam utilizing the ground loop only is very effective.

Your results sound very good. I think your approach is pretty smart, trying to get the biggest bang for the least bucks.

Where the compressor could help for cooling is if the re-purposed shop air handler was not providing enough cooling for your purposes. The compressor would give you cooler water, at a price.

You could also increase your cooling by just increasing the total area of your air handler. the easiest way would be to install more air handlers, like maybe 4X what you have now.

It might be worth your while to set up a performance log of your system. I did that this past winter on my backyard system.

Since you're using your system for cooling, you might record once a day at the hottest part of the day, which I would assume to be around 2PM:

• Loop water temperature
• Outdoor air temp
• Shop air temp

I was running my system with no thermostat, and I found that small changes in loop water temp made big changes in the amount of heat my system could put out, which was evidenced by the temperature rise. That behavior might not be so pronounced with a direct water system like you have now.

The reason I mentioned the small change/big change issue, is you might want to use a thermometer capable of resolving to 1/10 degree when measuring loop water temp.

So how are you handling the condensation that is being produced?

Best regards,

-AC_Hacker

[Drake]

Just toured a "Passive house" that successfully uses a smaller scale ground loop(600') that precools/dehum or preheats incoming air to HRV. It prevents frostup in winter and cools house without additional A/C under limited internal heat load(#of people inside,cooking, etc.). Being super insulated and air tight these buildings are much more isolated from outside temp. Condensation was trapped and drained as any A/C coil(catch pan and drain tube/pipe). Free distilled water if saved! Exploring this against "earth tube" for my building project.

For those heating with geo I would think it not difficult to work in a bypass loop before HP to just air handler for summer cooling using existing ground loop.

[AC_Hacker]

Originally Posted by Drake

Just toured a "Passive house" that successfully uses a smaller scale ground loop(600') that precools/dehum or preheats incoming air to HRV.

How did they do this? Did they run the loop water through some kind of water-to-air HX, similar to what randen has done?

Did you take any photos?

-AC_Hacker

[randen]

Ok the verdict is in. Air-conditioning with a ground loop works but!! The relative humidity is still very high. Utilizing the ground loop temperature in the evaporator side of an air handler will reduce the temperature of the room greatly but as the temperature is close to the actual room temp the result is not enough humidity is condensed out of the air. You start with high temp high humidity you get lower temp but the same relitive humidity. The evaporator requires a lower temp to condense out the humidity. By the numbers (sorry metric) outside temp 35 deg C. Water from the ground loop 17 deg C. air leaving the air handler 21 deg C. Room temp morning 21 deg C.
highest temp during the day 23.8 but the relative humidity is still around 80% Although the lower shop air temp is better than outside you feel hot and sweaty but again a lot better than the 35 deg C. outside. Maybe if the relative humidity of the air mass was lower it maybe more comfortable. One interesting thing I was cooling the air for 600 watts of electricity.

The GSHP will progress as time allows and of coarse I will continue to use the ground loop only system. I will post some more pictures soon.

Randen

[Drake]

Looked to me like the HX was a standard "A" coil condenser used in AC(easy enough to salvage). No BTU rating was available. And as Randen points out dehum is far less than dehumidifer or AC. I think purpose of ground loop is more for tempering incoming subzero fresh air to HRV than cooling but it is there and does provide some.

[Ko_deZ]

@Drake
That is given that the ground loop returns a high temperature, like at Randens place. Here the temperature would be maybe 13-14C in the summer, and for a deep well you would get about 7C. That would condense water just fine.

[randen]

Further Updates
Today at Randen the air was dry but hot 30 deg C. The shop air was 26 deg C. but dry. I felt a little hot, working hard in the shop and turn the ground loop cooling unit on. The air cooled very quickly maybe because of the lack of humidity. But in a matter of 1/2 hr the shop was at 22 deg C. and feeling very pleasent. It would seem that the cooling effect of ground loop only is viable if the humidity is low to start with.

To answere some earlier questions the air handler had a slant coil HX that was rated 3.5 ton of cooling with an additional HX coil to augment heating. I had pumped the loop water through both for a little extra capacity. The amount of condensate that flowed out on the humid day was remarkable but still didn't result in complete comfort.

Randen

[AC_Hacker]

Originally Posted by randen

It would seem that the cooling effect of ground loop only is viable if the humidity is low to start with.

With humidity being the issue, you might not need so much AC to bring the temperature of the water coming into the HX down to give you the condensation and dehumidification you need for comfort... possibly way less than 3.5 tons.

-AC_Hacker

[Ko_deZ]

Hi.

As MAPP is a trademark, not ever sold in Norway, and even the MAPP producer has closed down production, I had to get creative. I got in touch with one of our two large gas suppliers, and due to vacation time I got really lucky. I got in touch with a metallurgy professor, which seemingly had a great time talking about other things than his mundane everyday customer questions.

The local version of MAPP is called Thermolene. Not sure if that is an AGA brand only, but they sell this at least. It is avaliable in normal AGA shops together with all needed equipment. Even the prices where not all that bad. Excellent. I was about to hang up, and started thanking the dude for great info when he stopped me. "What will you use this for?". After some time of explaining, he sent my hopes crushing down. "Then Thermolene is not suitable.". The technical reason I cannot remember all the details of, but in essence, the high hydrogen content of the Thermolene will make the weld brittle, or at least more brittle. The life expectancy of the weld with MAPP or Thermolene (they contain the same stuff really ), and expecially when not mixed with oxygene but with humid air, is greatly reduced. Now, typically a bazed connection will have no problem handling the pressure, even when using Thermolene, but due to the continuous vibrations from the compressor, the brittleness might become an important factor.

There was an option though, you could buy some insanely expensive welding sticks with special fluss (that is the norwegian word) on them to stop this effect, and he would still not recommend the approach.

With propane in the system, a sudden big leak in an enclosed area could be less than desired.

Ko_deZ