12 Feet Under: 1000 Square Feet of Geothermal PC Cooling - Page 30

Here's the messy finished heat stick. The element's hexagonal base edges had to be slightly ground down to fit into this spare 2" pvc tube. It was JB epoxy welded into place with three layers. The interior wires were also covered with epoxy and then filled with silicone through a hole drilled into the side. The electrical tape was used to cover the hole while the silicone slowly dried. With the drain port top it conveniently screws into my reservoir which keeps water flowing past the element.



Watt meter readings at 19.33 hours into the testing. It's plugged into a 14 gauge extension cord that goes to a GFCI outlet in the kitchen. The power use is slightly higher without that extra 20 feet of cord being used.




The crawl space temperature sensor (purple) is being hit by the sun, hence the swings. It's interesting to note the water temperatures are also very slightly affected at those points too. Aside from that there's not much to note about the readings so far.

Well, it looks like more than 48 hours will be required.

I'm doing science, and I'm still alive. Well it was somewhat scientific until the flaws became apparent. At this point I'm only making a pretty graph I can compare future results to. (Ambient temperature swings are wrecking the data.)

The daily and weekly images in my last post have been updating every 5 minutes with the new results. However, here are the saved full charts of the last two days.



Cliff note legend: Blue = Water in and Red = Water out



The water out spike down at 10:45 was caused by my topping off the reservoir (loop wasn't fully bled). The element was unplugged for one minute and two cups of pre-warmed water were added. It still took a while to recover from that.



(Repost of the updating Day and Week chart)



At 10:30 this morning I placed a cardboard box in front of where the pipes exit the ground in the crawl space. The effect was visible in the exposed water out readings a few minutes later. It doesn't look like the sun was adding many BTUs directly to the loop, but the sensor was being slightly warmed.

The increased warming effect while the sun is at its strongest (9-3) is also interesting. The next time I do this test, the crawl space will be closed off and I'll have added another layer of foam to the pipes.


I'm not sure if I mentioned it, but that ground sensor's readings can't be used to accurately determine how much the ground has heated up. Its located at the start of the loop, at the side of the coils and at least a foot higher in the ground. Its more of a general ground temperature guideline to go by. That being said, the ground sensor reading has gone from 11.2c to 14.8c. The water in one has moved from 11.6c to 19.3 in 65 hours. Only 2.42c of that occurred in the last 48 hours though.

I'm really looking forward to how quickly, or slowly, the water and ground normalizes once I remove the heater at 1am tonight. I'll keep the pumping running without a load on the loop so the cooldown rate can be recorded.

The effect on the loops equilibrium should be noticeable immediately.

Yeah Shurik, I definitely need a chiller to extract heat from the ground this winter. Replacing a condenser with a heat exchanger to the ground source isn't as big of a energy saver in a temperature climate. It's nice and clean though, since the window AC unit would still be installed and used in exactly the same fashion.

Edit: The live temperature data is also updated every 5 minutes in a table here.
Edited by Romir - 3/19/10 at 3:44pm

I'm putting these pictures in their own post for the update listings.

Here's the final energy use tally at the 72 hour mark. I pulled the plug two minutes after the sensor results shown in the image, so they're spot on for the final results.



(Most of) day 3's chart of the thermal testing. Not much happened. There was a little over a 1c rise in the water temperature from the 113,000 BTUs dumped into the loop yesterday.



Its been 20 minutes and the water in temperature has already dropped 1.5 degrees Celsius.