HDD Used In Geothermal Application
HDD used successfully to install new geothermal loop system at million-dollar estate with minimal effects to property and landscaping
By Randy Happel Aug 21, 2013
The setting is one of the most prestigious locations in the South — or perhaps anywhere in the country for that matter. Often referred to as “Beverly Hills of the East,” Atlanta’s famed Buckhead district is home to the ninth-wealthiest ZIP code in the nation (30327), and a median household annual income in excess of $350,000. Situated within the gently rolling hills and dense forests are some of the most stately and glorious mansions in the entire Southeast.
It was here that Rick Daniel and John Peebles, founders and co-owners of Southern Geothermal, headquartered in Evans, Ga., were called on to assist in remedying problems with a multi-ton geothermal heating/cooling system positioned beneath the meticulously landscaped site of a new 10,000-sq-ft mansion. A premature malfunction with one of three vertical loops installed directly beneath the million-plus-dollar home prior to construction — and well in advance of completing the elaborate landscaping surrounding the home — was in need of repair; and Southern Geothermal was chosen to provide a solution.
Installing a replacement system using the vertical drilling approach would likely result in severely damaging the now-established grounds; an obviously costly proposition for the homeowner. Southern Geothermal was selected for their ability to provide a less intrusive option. Having successfully completed more than 900 geothermal installations previously, the expertise of Southern Geothermal in completing horizontal loop systems installations was well documented.
“Trenchless was the only option without incurring a lot of construction damage,” Daniel says. “Heavy vertical drilling equipment would have wreaked havoc with the grounds, likely resulting in considerable damage to landscaping and the 500-yard long, winding cobblestone driveway. HDD equipment is much more compact and far less intrusive. Using HDD avoided lot of headaches and saved a lot of money.”
Prior to starting Southern Geothermal, Peebles had worked with some of the top HVAC companies in the Augusta, Ga., area as a service technician. In 1997 he founded his own company — Peebles HVAC — specializing in geothermal systems installations. At the time, Peebles HVAC was one of only five heating and air conditioning companies installing geothermal systems in Georgia. In 2007, Peebles landed what he considered a defining moment for his company — the installation of 300 geothermal units at Fort Gordon Military Base located in nearby Augusta. After several years of steady growth spawned by the increasing awareness of the many benefits of geothermal heating/cooling systems, Peebles teamed up with Daniel, an experienced and successful business and marketing strategist, to create Southern Geothermal in 2011. The same year, Peebles and Daniel purchased a Vermeer D16x20 Series II Navigator horizontal directional drill (HDD) for completing horizontal loop system installations.
Southern Geothermal has become a recognized leader in geothermal installations and loop service throughout the Southeast, having cultivated relationships with many of the top HVAC contractors in the Southeast. The company offers a broad range of geothermal installations expertise, including both single- and multi-family residential dwellings, public housing projects and commercial building applications. The company’s capable crew of six is well-versed in both trenchless and vertical drilling technology, having installed both horizontal and vertical closed-loop systems, as well as lake/pond closed-loop and open-well applications.
Perhaps more than any of the geothermal installation jobs tackled by Peebles and Daniel’s company previously, it was imperative that the Buckhead project be completed with the utmost care and sensitivity to surroundings. Minimal effects on property and landscaping were imperative. Hence, a horizontal-loop installation configuration was the obvious choice.
“Using HDD has made a lot of jobs much easier,” Peebles says. “Trenchless is a much less invasive approach compared to the disruptions often created by vertical drilling equipment. We’re able to complete jobs with very little damage or mess. On the Buckhead project, we were able to drill beneath a courtyard walkway, the front yard and under a cobblestone driveway with virtually no visual effects or damage.”
The drill plan developed by Peebles and Daniel was based on the original system’s specifications and tonnage requirements as calculated by the HVAC contractor. Geothermal system load calculations are determined based on several factors — square footage of the structure, ground conditions/conductivity, climate and usage. Once the system’s capacity requirement is calculated, Southern Geothermal then puts an installation plan into action.
After receiving the load system specifications for the Buckhead project, Peebles and Daniel mapped out a drill plan that called for completing three 300-ft bores; one each for the three circuits needed to support the 3-ton capacity load requirement of the system. According to Daniel, the cooling load of most geothermal systems requires installing more loop material than is required for heating. Climate and soil conditions are also major considerations for determining load calculations.
Soil conditions on the Buckhead job consisted of varying densities and compositions of clay, along with scattered deposits of shale. Along the lengthy bore paths, drill operator David Faircloth would often encounter areas of wet clay followed immediately by a hard-packed composition of the same substance, with some shale thrown in for good measure. Soil profiles were not completed in advance given that Peebles had extensive knowledge of the soil conditions having drilled in the area on many previous occasions. A straight bentonite drilling fluid mixture was used to ensure the integrity of each bore was maintained.
Upon the completion of each bore, the heat-fused sections of SDR-11 polyethylene tubing — material ideal for geothermal fluid conductivity — were pulled back through the bore path using the D16x20 Series Il drill. The three loops were then connected to the header situated beneath the courtyard, and from there, on to the house and the existing HVAC system. Peebles was pleased to report that the project was completed successfully without incident.
“Our company is experienced in completing both horizontal and vertical geothermal-loop systems applications and both methods are equally effective and efficient,” Peebles says. “The major difference is the equipment often used to install each. In this situation HDD was the best option for several reasons. The compact frame and corresponding minimal footprint of the Vermeer drill vs. the larger, heavier drilling equipment used to install vertical systems made all the difference in the world. The ability to drill beneath established landscapes, driveways, retaining walls, etc., and with very minimal adverse effects was a huge advantage. As you might imagine, the homeowner was elated.”
Randy Happel is a features writer for Two Rivers Marketing, Des Moines, Iowa.