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While geothermal heat pumps have numerous benefits, including high SEER ratings and low maintenance costs, their accompanying loop fields make them inherently more complex and time consuming to install than traditional air-source heat pumps. Each installation involves digging up a yard, laying hundreds of feet of pipe, and generally disrupting the lives of homeowners, but thanks to the innovative thinking of manufacturers and contractors, there are now new products and techniques that can enhance the installation experience for the homeowner, as well as the contractor.
No More Nuking
One of the biggest complaints homeowners have regarding the installation of geothermal systems is the fact that it often ruins their existing landscaping. As Joe Huck, president, Williams Comfort Air, Carmel, Ind., noted, “Geothermal has always been a no-brainer for new construction, because the walks and drives aren’t there yet. But for an existing home, it can involve nuking the yard. Not to mention that few people have yards big enough to install horizontal loops.”
After hearing these complaints numerous times, Huck and new construction supervisor, Terry Biggs, started thinking about a different way to approach installing systems. They wondered if they could dig one central hole and install smaller loops at various angles and depths, potentially under sidewalks, driveways, and basements, instead of digging trenches to run several hundred-foot runs of piping. And it worked.
“First of all we dig a hole that’s about 4-by-8-feet deep, and all of the loop is installed from this hole,” said Huck. “We drill blind holes on an angle — in the shape of a fan — without coming back up, like with the old boring machine. We know exactly where the drill bit is, because there’s a sensor in there. We drill the hole, put the tube in the hole, pack the hole, then tie all of the supply lines together and all of the return lines together. Then we take the one supply line and the one return line, and bore those two lines into the house to the geothermal equipment. The property is not affected in any way, except for the hole that is graded and sodded over when we’re done.”
This patented process, called the Williams Vertizontal™, involves a modified drill that can bore the hole while taking the tubing with the drill bit (the one-pass process). In the two-pass process, the hole is drilled and the tubing is subsequently attached to the drill, then snaked back down the hole. “We’re really excited about how this will open up the geothermal industry,” said Huck. “Basically, we’ve made it so that if you have to cut grass, you can put geothermal in your house.”
The Williams Vertizontal process, which is not yet commercially available, does have its limitations, as it cannot be used in areas with solid limestone, and it takes more time to install the loop field because it involves a surgical approach to installation, instead of using a backhoe to “nuke” the yard.
“The Williams Vertizontal is not perfect, and it has its limits geologically, but if you don’t want us to nuke your yard, it’s a great option,” said Huck.
Better Pipe Fusion
A significant part of any geothermal installation involves pipe fusion, which, as described by pipe fusion machine manufacturer, McElroy Mfg. Inc., is a process that joins two pieces of thermoplastic pipe together with heat and pressure. Commonly associated with high-density polyethylene pipe (HDPE), the company explained that the butt-fusion process starts by facing or shaving the pipe ends simultaneously so that they can be joined together with heat to create a continuous sealed pipeline. The welding of the pipes is accomplished by using a hot plate in contact with the pipe ends, which heats the plastic to a molten state. Then, after its removal, the ends are pressed together under a controlled force to form a weld that is as strong as, or stronger than, the pipe itself.
McElroy’s new 1LC fusion machine is a compact tool that can be used to simply and reliably butt-fuse HDPE piping joints in a geothermal system, said company research and development manager, Jason Lawrence. “It has the features and functionality found on larger, more expensive manual machines, such as a locking cam system for holding a fusion joint immobile as it cools, and our patented Centerline Guidance System for even pressure around the joint. It is perfect for butt-fusing HDPE piping that is 32 millimeters in diameter and smaller.”
The 1LC works well with the 1-inch sizes that are common in some ground loops, said company public relations specialist, Tyler Henning, however, when it comes to fusing larger polyethylene pipe headers, larger fusion machines may be required. “We recently used our own 1LC on a large upgrade to one of our manufacturing facilities, and it helped our contractors properly and efficiently fuse key joints in the vertical loop fields constructed for our system.”
Before using the 1LC fusion machine, contractors should understand the butt-fusion process, said Henning, and if they don’t, they might want to consider attending McElroy University. “The ideal class for geothermal contractors would be our small diameter operator qualification course, which includes a lot of hands-on training.”
Looks Great, Less Backfill
Also looking to improve the ground-loop installation process is fittings manufacturer Ground Energy Systems, which recently introduced the Geo-Glide U-Point. Stating that it is the narrowest geothermal U-bend in the industry, company president, Ron Gershoni, said the U-Point allows contractors to drill a smaller-diameter hole and use less material to backfill the hole.
“Less material leads to a reduction in the time it takes to mix and fill the bore with grout,” said Gershoni. “The U-Point is also up to 33 percent smaller on the outside than other U-bends in the industry but features a wide-open interior flow path with no sharp turns.
The company also recently introduced a product designed for use on the interior part of a geothermal installation. Geo-Glide thin wall fittings are designed to facilitate the speed and appearance of insulated piping. The fittings feature a thin wall, sweep bend, and ribbed surface, all of which reduce friction, making it significantly easier to slide insulation over the fitting. “This leads to a reduction in time to complete the job, a reduction in pressure drop, and a much nicer finished appearance of the installation,” said Gershoni.
Traditional fittings have a thick wall, and the elbows have a sharp 90-degree bend, said Gershoni, and the combination of these two features makes it very difficult to slide insulation around them. “Often the insulation bunches or tears, causing delays and unsightly fixes. We designed the Geo-Glide to specifically address the difficulty of insulating thicker-walled fittings.”
Pipe Joining Made Easy
Watts has manufactured products for geothermal applications for a long time, and its product director, Steve Barrett, agrees that field preparation for the geothermal heat exchange can be expensive and time consuming. To simplify the process, Watts recently introduced the Triton™ radio frequency pipe fusion system, which uses radio frequency technology to fusion weld polyethylene pipe and fittings quickly and safely.
“Radio frequency fusion welding has been available for many years, though it has typically been used for joining plastic shapes and component housings in a factory production setting,” said Barrett. “The Triton system is specifically designed for pipe joining applications in the field. It allows the field to be dry-fitted and pipe joints fused with minimal tool and pipe set-up time. The process is not affected by weather or temperature. The entire field can be tied in, dry-fitted, fused, and pressure tested by one installer.”
The primary benefits of the Triton system to the contractor are safety and speed, as it does not generate any external heat and has no exposed heating surfaces, said Barrett. “All of the heat is generated inside the fitting, so fittings are warm to the touch after fusion but will not burn the contractor. As for speed, the control unit is self-calibrating and makes adjustments to the weld time based on an integrated ambient temperature sensor. The system is ready to weld within a minute of powering it on and is not affected by wind, drizzle, or cold outside temperatures.”
With the Triton system, preparation of the pipe is as simple as cutting it squarely, wiping it clean, and inserting it into the fitting using the depth gauge built into the fitting, said Barrett. “The installer does not have to babysit the fitting once the fusion cycle is started and can move on to dry fit the next joint in sequence. The control unit will alert the installer when the fusion cycle is completed, and the next joint can be started in sequence.”
Triton requires a minimal amount of training for new users and can be used in all-new, retrofit, and repair situations where OD controlled (ASTM D3035) medium-density polyethylene pipe (MDPE) and HDPE is used, which includes geothermal polyethylene pipe. The Triton system is a moderately more expensive way to fuse pipes, but the system allows one person to dry fit and complete all of the fitting fusion usually associated with bore and trench installations, said Barrett.
As can be seen here, new products and techniques are continually being designed to ease the installation of geothermal systems. Given the increasing popularity of these energy-efficient systems, it is likely that even more innovations will be seen in the near future, making geothermal a more attractive option than ever for homeowners.
Publication date: 7/29/2013