Take a Look at the Overlooked to Improve Efficiency
Karpen stated that a number of relatively unknown systems, plus a number of overlooked maintenance and operation items, “can save a substantial amount of energy, particularly electrical energy, in many buildings.”
He added, “There are also some new technologies that have not yet caught on that can make a real difference. I see this, time and time again, when I do preliminary surveys of buildings.”
Emerging TechnologyOne example of an emerging technology, he said, “is the GFX heat exchanger, which can be used to recover heat going down the drain from hot water discharges.”
The heat exchanger, manufactured by Doucette Industries, York, PA, consists of a coil of copper tubing wrapped around a copper drain pipe. “Incoming cold water is fed into the bottom,” he explained, “and preheated water comes off the top which can be fed directly into a hot water heater.
“A 5-foot section of the heat exchanger can recover 60 percent of the available energy between the hot water flowing down the drain and the cold water feed.”
Because the unit allows preheated water to be fed into the hot water tank, “the capacity of the hot water heater is now effectively two-and-a-half times as great.”
Attractive PaybackIn the residential sector, the typical payback period for this product is between two and five years. According to the inventor, Carmine Vasile, a number of residential installations have resulted in savings as large as 45% on total water heating bills. As the system works best on continuous flows of hot water, batch use (such as a washing machine) does not result in much savings, except in laundromats where the hot water usage is essentially continuous.
In commercial use, the payback period is typically between two and five months, and can be less, said Karpen. And the Long Island Power Authority is providing rebates for commercial installations.
However, only several thousand of these systems have been installed worldwide to date. But Karpen believes that the potential number of installations is in the tens of millions. “People need to know about this relatively unknown device, and they will use it.” (For more information on the GFX heat exchanger, see “Stopping Heat from Going Down the Drain,” September 4, 2000, page 33.)
Varaiable-Speed Kitchen ExhaustAbout 12 years ago, a small test and balance firm, Melink Corp. of Cincinnati, OH, developed a variable-speed kitchen exhaust controller.
Commercial kitchens operate their hoods for long periods of time every day; however, there are periods between meals where the systems are in light use. This controller works by sensing the smoke, temperature, and carbon dioxide in the exhaust gases, and appropriately slowing down or speeding up the fan to properly exhaust the cooking range as needed to save energy.
In the first 10 years of selling the product, Melink sold only 400 units. In the past 18 months, the company has seen a considerable increase in business, and has sold 600 controllers, one-and-a-half times the volume of the previous decade.
Ted Owen, vice president of sales, told Karpen that the company expects a huge increase in business in the near future, largely driven by the cost of energy. The controllers save both electrical energy to drive the fan, as well as natural gas used as a cooking fuel at the grills, since a decrease in the exhaust rate reduces radiative as well as conductive and convective energy losses.
In addition, substantially less conditioned air, either heated or cooled, goes up the kitchen exhaust.
Owen said that energy managers at chain restaurants and supermarkets are beginning to listen now. And Melink is now working with hood manufacturers to have the systems installed by an oem, instead of having to retrofit it after the construction of the kitchen.
The controller works with three-phase exhaust fans. A variable-speed controller that will work with single-phase shaded pole or permanent split capacitor motors is being developed.
In the past, the owner of a kitchen hood with a single-phase exhaust fan motor had to replace it with a three-phase motor, as well as running a three-phase line from the electrical panel to the kitchen range. The additional cost could add as much as $1,000 to the price of the installation. Normally, the cost of installing the variable-speed controllers runs between $3,000 and $8,000 per hood, depending on field conditions and the number of fans to install controllers.
Karpen noted that there may be as many as 1 million commercial kitchen motors that would benefit from the controller’s energy savings.
With the development of single-phase models, due out in July, the controllers can be installed in residences as well, and the company says that it is getting some inquiries from high-end residences, some of which have the essence of a small commercial kitchen.
Dehumidification TechnologyAnother energy-efficient product that is not in typical use is the dehumidification system from Nautica Dehumidifiers, Inc., Huntington, NY, which uses its MSP™ (multiple small plate) heat transfer technology.
The system can be used to dehumidify outside air streams for applications where the desired dewpoint is above 35Â°F.
“Typically, these systems are twice as energy efficient as desiccant dehumidification,” proclaimed Karpen. (For more information, see “More Energy-Efficient Dehumidi-fication,” May 17, 1999, page 11.)
Nautica has just improved the performance of its products by using a counterflow air-to-air plate heat exchanger in a multiple small plate configuration. The heat recovery efficiency has been brought up to 85%.
“The improved systems are cheaper to install than desiccant dehumidification systems. They are less complicated, and require little maintenance other than changing filters and coil cleaning,” Karpen said. The technology is used in conjunction with conventional cooling coils supplied by chilled water or by direct expansion.
Clean Ducts and CoilsMaintenance of hvac systems is very important to maintaining optimum efficiency. “The most significant maintenance item that can be done to both improve indoor air quality and cut energy use is a complete duct and coil cleaning,” he stated. “It is not unusual to improve the efficiency of an air conditioning system by 20 to 30 percent.”
He recommended that coil cleaning be done on an annual basis.
Karpen also strongly favors the use of paper pleated filters. He said they are far more efficient than fiberglass filters, and suggested that filters be changed every three months on a regular basis.
Insulate for SavingsPipe insulation is something that is often overlooked, he remarked. “You would be surprised how many boiler rooms and domestic hot water systems do not have proper pipe insulation.” Tables are available in the ASHRAE Fundamentals Guide which provide data on insulating piping, he said. “If the piping in a boiler room is properly insulated, the boiler room temperature should not exceed 70Â°.”
Replacement of older hvac systems should always be done using the most efficient equipment available, advocated Karpen. Accepting lower efficiencies to save some dollars upfront will end up costing the user dollars every day the system is in operation.
Forced-air heating systems fueled by natural gas have efficiencies approaching 90%, he said. Users should not install second-best systems. “The 80%-efficient furnace should be banned by the Department of Energy,” he declared.
Regarding cooling, most manufacturers of air conditioning equipment have models with a SEER of 13 or above, and some approach 16 to 18 SEER. That’s a big jump in efficiency from the commonly applied 10-SEER standard unit.
“The 10-SEER air conditioner should also be banned by the Department of Energy, and new regulations to effectuate a higher efficiency standard have been proposed,” he noted.
Proper Returns“It is impossible to properly balance a system without proper return ductwork,” he said. Many owners, in a desire to cut costs, have their hvac contractors leave out return ductwork and rely on the ceiling plenum as a return. “This is a disaster,” maintained Karpen, “because dirt accumulates on top of the ceiling tiles, resulting in indoor air quality problems.”
Another common cause of IAQ problems in buildings, he added, is dirty carpeting. Karpen related that he recently quit a consulting job at a law firm because the dirty carpet in the building was making him ill each day.
Lighting is one more way to save a significant amount of energy in a commercial operation. “Full-spectrum lighting is more energy efficient than conventional fluorescent lighting because one can see better at a much lower level of illumination,” he stated.
And one final tip for the many PC users out there: “When you’ve finished using your computer, be sure to turn it off.”
Karpen can be reached at 3 Harbor Hill Drive, Huntington, NY 11743; 516-427-0723.
Publication date: 05/14/2001