Sunday, October 17, 2010

Geothermal Is Here

Our new geothermal HVAC system is officially installed. Mostly anyway. The radiant floor heat is still in the works, but all of the forced air systems are up and running. What a glorious thing!

The whole thing started with a drilling rig pulling up to destroy our front yard. I had initially hoped that we could have the wells dug in the back yard, but there really wasn't any way of getting a 42,000 pound truck into the back yard without crushing our very old, shallow sewer line. Oh well, we had planned to re-landscape at some point, so why not now?

The area where our house is located -- from a geological standpoint -- is pretty much solid limestone. There are a few feet of clay and loose rock under the top soil, but then it is solid limestone for at least a couple hundred feet down. When I initially talked to the HVAC contractor, I asked what would happen if they hit rock while they were drilling. He told me that the drillers actually like to hit rock because the wells don't cave in on themselves, so it makes it easy to get the tubing down in to the well.

A drilling rig is really nothing more than a giant hammer-drill. A LOUD giant hammer-drill. I happened to be home sick with a cold the second day that they were drilling. Needless to say, I didn't really get to nap too much, but it was interesting to watch the drilling process from the bedroom window.
 
The wells are spaced about 10 feet apart. What you see in the picture below are the first four wells. The light grey sludge that you see isn't concrete. It is actually pulverized limestone dust mixed with water. The drillers would pump water into the the well to keep the bit cool, and the result was a slurry of limestone that would make its way to the surface. Once a well was drilled, the drillers would insert a loop of plastic tubing all the way to the bottom, then use a squeegee to scrape the slurry back into the hole to fill in around the tubing.

 
If you aren't familiar with geothermal systems, they work on a very simple premise: circulate water through the tubing in the wells to pull coolness out of the ground when it is hot outside, and pull warmth out of the ground when it is cold outside. If you want the more scientific explanation of how geothermal works, check out this link: http://www.geocomfort.com/geothermal-technology

Our system is the "vertical loop" type, so it required several wells to be dug. The number of wells required depends on the system size needed. Our HVAC contractor determined that our house needs 8 tons of heating and cooling, so that meant that 1200 feet of underground water loop would be required. The wells they dug in our yard are a little under 200 feet deep, so that meant that we ended up with seven wells.

The layout inside our house doesn't provide much space for running ducts from the basement to the second story, so we opted for a split system. This means that we have a separate system that heats and cools the upstairs level, while a unit in the basement takes care of the main level and basement. The upstairs unit is rated at 3 tons, and the unit for the main level and basement is 5 tons since it has more area to heat and cool.

Enough about the system -- back to the front yard.

A couple of days after the wells had been dug, another crew showed up to further destroy the yard. Uh, I mean, to join all the tubing into one continuous loop. If the yard looked bad after the wells were dug, it looked ten times worse after the loop work was over. In order to join the tubing for all of the wells together, they had to dig a pit that encompassed all of the wells, about four feet deep. So for half a day, we had a pit four feet deep by twenty feet wide by forty feet long in the front yard. Once all the wells were connected to each other, they filled the pit in. Since our soil is very rocky, the resulting pile of dirt in the front yard looks a bit like those pictures of the Mars landscape. I would love to show you a picture of the dirt pile, but I'm having trouble uploading any more pictures to the blog at the moment. For those who are just dying to see the dirt pile, you can send a self-addressed stamped envelope (plus $2.95 for handling). Other large cash donations are accepted as well.

The most exciting thing about having the new geothermal system installed is that it is the first thing we've actually put into the house. Everything else to this point has pretty much been removing or demolishing things in order to prepare for remodeling. So we've hit a milestone -- the remodeling is officially underway!

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