More building owners are asking for geothermal heat pumps (GHPs) and other efficient heating-and-cooling alternatives, boosting demand for skilled workers who know how to assemble all the hydronic components. A union in Chicago has just begun to teach its workers formally on the ups and downs of GHPs.
“As the consumers and the industry go toward geothermal, we are bringing our journeymen up to knowledge so they know how to install it properly,” says Paul Chapello, an instructor at pipefitters’ union Local 597. Earlier this year, the local’s training facility in Mokena, Ill., installed a three-ton geothermal system, the guts of which are on display for night classes that started this fall.
The problem with teaching students on the inner workings of GHPs is that most of the key components are buried or are underwater, so it is often difficult for newcomers to visualize how the parts and pieces come together. Local 597 got around that problem by exposing much of the works indoors.
The training center’s demonstration system features a vertical, ground loop and a “slinky,” indoor water loop. A single-phase compressor runs off the parallel closed loop and is wired up to an electronic thermostat. The working fluid is a red mix of propylene glycol, a nontoxic antifreeze. “It is the same stuff as in a slushie,” says William Wren, another instructor.
Building the indoor water loop required a structure big enough to contain 4,000 gallons of water and three, 150-ft-long coils of 3⁄4-in. plastic tubing made of high-density polyethylene (HDPE). In a normal installation, workers would have submerged the HDPE in a nearby pond, lake or aquifer. Local 597 consulted with Chicago’s Shedd Aquarium to build a fiberglass tank with a window similar to one that would normally display exotic fish.
For the ground loop, the union brought in a contractor to drill three, 8-in.-dia. boreholes down to 150 ft below the floor. The HDPE loops, about 900 ft total, went down into the wells, which were filled with a thermal grout that stabilizes the tubing and helps it conduct heat. Typically, the surface HDPE pipe would be buried at least below the frost line to protect it. Because this system is indoors, freezing is not an issue, so some of it is visible.
Typical air-conditioners use compressed refrigerant and fans to pull air through a 40°F evaporator coil and reject the heat to an outdoor, 120°F condenser. Local 597’s system—and all GHPs—use refrigerant and an indoor coil, but the glycol loop is the condenser, cutting the energy the compressor needs to maintain pressure. Because the water loop is at room temperature, it is less efficient than the ground loop, which runs at about 50°F to 55°F. In a recent demonstration, the compressor pulled 8.5 amps from the water loop. Wren switched to the ground loop, and electrical demand dropped 18%. Still, the system is 30% more efficient, overall, than a conventional one. Watch the demo up close at www.enr.com.