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Due to the 40-ft.-high ceilings in the most recent addition at New Hampton Metal Fab, air conditioning was not an economical option. Instead, the company installed an 18 ft. diameter PowerfoilX fan from Big Ass Fans.
The immense size of the large-diameter fan efficiently moves the large amounts of air through the entire facility, leading to more comfortable and productive employees.
During destratification, warm air is pulled off the ceiling and brought down to occupant level before being pushed out to the walls and up to the roof to be recirculated. Thoroughly mixing the indoor air at New Hampton has reduced the temperature difference between the floor level and the underside of the roof deck to less than 1°F, enabling the company to keep the facility at a uniform temperature of 68°F.
Expanding a business is an outward sign of success, yet this accomplishment can also spur unexpected growing pains. That was the case when New Hampton Metal Fab added to its facility, and heating and cooling the extra space became a challenge. To improve the working environment, New Hampton installed a large-diameter fan from Big Ass Fans (Lexington, Kentucky). Now, the company has realized energy savings, and the work environment is much more comfortable for employees.
When New Hampton Metal Fab opened its doors in 1945 as a blacksmith shop in northeast Iowa, the company worked out of an 800-square-foot wooden shed. After several expansions, the third-generation, family-owned business now fills a 53,000-square-foot facility, where it produces molds for the pipe and precast concrete industry as well as agricultural equipment. After a recent 12,000-square-foot expansion, the company realized its growth created hot working conditions in the summer and cold conditions in the winter that were diminishing employee comfort levels and hampering productivity.
The facility itself has little to no insulation, so the average 20°F to 80°F outside temperatures are felt throughout the shop floor. Adding to the varying-temperature issue is a 40-foot-high ceiling in the most recent addition. In the summer, the high ceilings make air conditioning an uneconomical option. During the winter, the temperature difference from floor to ceiling could range from 5°F to 30°F due to stratification. This occurs when hot air, which is less dense than cold air, rises. The air coming from a heating system or as a byproduct from the facility’s plasma burn table and welding station is lighter than the rest of the air in the facility, so it collects at the ceiling while the colder air remains at ground level. “We’d send somebody up to fix something and they would strip down to their long johns, while the guys on the floor were standing there in Carhartts, basically freezing,” explains Pete Gallup, purchasing manager.
To eliminate these temperature variations, New Hampton originally installed individual, 30-inch floor fans at 20 different stations. “They moved some air in the summer, but they didn’t destratify at all in the winter,” Mr. Gallup says. The company also tried installing fans on the walls to push the warm air down during winter months, but this caused a draft at the already cold floor level. Finally, the company removed the wall-mounted fans and replaced them with an 18-foot-diameter PowerfoilX fan from Big Ass Fans.
As it turned out, the large-diameter fan solved both summer and winter temperature-control issues for New Hampton. The key to this is variable-speed control—running at higher speeds in the summer and lower speeds in the winter. While adjusting the fan’s speed is part of the equation, ultimately the large-diameter, low-speed fan’s immense size is what makes it so efficient at moving large volumes of air and saving energy.
In the summer, the fan runs at 60 to 100 percent capacity to circulate a cool breeze. New Hampton is able to save energy by increasing the temperature several degrees because air movement across a person’s skin creates a cooling sensation similar to that of an air conditioned building. To achieve this rate of effectiveness, the low-speed fan uses an airfoil/winglet design to move air up and over obstructions. Additional AirFences installed along the airfoil can reclaim the air sliding down the airfoil as the fan spins, redirecting the air towards the floor and increasing the efficiency of the fan.
In the winter, the fan is slowed to 15 to 25 percent of maximum operating speed to destratify air. The key to destratification is the ability to mix the entire volume of air in the space and to do so without causing a draft. By increasing the length of the airfoils, the large-diameter fan is able to sweep more surface area than a smaller-diameter fan. Through proper air circulation, warm air is pulled off the ceiling and brought down to occupant level before being pushed out to the walls and up to the roof to be recirculated (see diagram on left). Thoroughly mixing the indoor air at New Hampton has reduced the temperature difference between the floor level and the underside of the roof deck to less than 1°F, enabling the company to keep the facility at a uniform temperature of 68°F. “We used to have some very cold corners we just kind of moved away from. Nobody would work there,” Mr. Gallup says. Now, employees can work pretty much everywhere, he says.
As an added benefit, the amount of air the fan moves increases at a much faster rate than the amount of power it takes to turn it as the size gets larger. So, with all things being equal, the fan will become more efficient as its size increases. “By reducing the amount of heat trapped at the ceiling, it’s similar to turning the thermostat down five to seven degrees,” says Christian Taber, senior application engineer and LEED AP for Big Ass Fans.
The large-diameter fan turned out to be a good balance for New Hampton. The company says it saved 34 percent on heating costs after the fan was installed while providing cooling during the summer. “Welding is pretty much a down and dirty job no matter where you do it,” Mr. Gallup says. The addition of air movement does not change this fact, but it goes a long way to improve the overall comfort of the welders.