For Greg Short, summer means fielding complaints from employees. Mr. Short is Maintenance Supervisor for Agri-Fab (Sullivan, Illinois), a major manufacturer of small lawn trailers and accessories. The company supplies to retailers like Lowe’s and others companies. As Mr. Short says, “If it can be attached to a Sears lawn mower, we make it.”
Housed in a metal building, Agri-Fab employees cook under the hot summer sun. To ease the situation, the company bought floor fans and column fans. Mr. Short says the floor fans were a disaster. He remembers how the fans would get dirty or run over by fork-lifts. Additionally, they were used so much they would eventually break. The fans were always in the shop being repaired. If the fans couldn’t be repaired, they had to be replaced.
Mr. Short says the company wouldn’t consider air conditioning the facility. Installation and energy costs made it an impractical and expensive proposition. The company looked into installing a misting system to cool down the roof, but it didn’t make a lot of sense. “It used a lot of water,” says Mr. Short. “The return in cooling and in our investment wouldn’t have been worth it.”
As Mr. Short researched the misting system, he stumbled onto Big Ass Fans (Lexington, Kentucky). These high-volume fans have diameters that range from 8 to 24 feet and operate at low speeds to produce high cooling results.
Mr. Short was intrigued by the large fan concept and did some more research. Each fan generates a 20-foot column of air beneath it. But it’s not the column of air that is the fan’s key to success. When the fan’s air column hits the floor, its deep air jet radiates out in all directions. As the jet moves out from the center and hits walls and partitions, air moves to the ceiling and recirculates through the fan. This creates convection-like currents that gain momentum with time. If several fans are mounted near one another in a very large space, the adjacent floor jets act like vertical partitions and improve the impact of each individual fan.
Mr. Short knows that while large (or small) fans do not cool air, they do work with the human cooling system. When perspiration evaporates off the body, it feels cool because evaporation moves body heat away from the body. Fans can make a worker’s skin feel 5 to 7 degrees cooler.
Fans are great for cooling down employees, but fan speeds of more than 300 fpm can create an air current that is unpleasant and disruptive. In addition, the air jet created by high speed fans dissipates over a short distance, creating uneven air movement throughout the building. For this reason, a gentle breeze created by slow-moving fan blades is more effective at cooling. High-volume, low speed fans work on the same principle.
Large fans can even improve comfort in air-conditioned spaces. The best-designed air conditioning system will generate an air throw of over 10,000 cfm per 100 tons, which is felt only by those working closest to the air registers. A single 20-foot ceiling fan displaces air at a rate of about 90,000 cfm. The moving air can be felt 50 feet from the center of the fan.
To workers, this slow-moving air can make the facility’s air temperature feel 6 to 10 degrees cooler than the thermostat actually registers. This is said to create significant savings in operating costs. Conservatively, a facility realizes 5 percent savings in air conditioning costs for each degree the thermostat is raised. This means a 20 percent savings for a thermostat set at 82o F instead of 78o F.
Big Ass Fans recommended that Agri-Fab set up the fans on a grid pattern over the shop floor. The company bought 20 fans: two were 10-foot models; the rest were 20 feet in diameter. “Our buildings have 112-degree roof pitch,” says Mr. Short. “The ceiling peak is 31 feet high and about 18 feet in the eaves. We have a lot of conveyor belts and racking systems. The fans fit perfectly and hang 3 to 4 feet below the peak.
“The employees love them,” says he continues. “It still gets hot down here in Sullivan, but now it’s a lot cooler on the line.”
Although Agri-Fab purchased the fans to cool its employees, they turned out to have an added benefit. “We keep the fans running in the winter,” Mr. Short explains, “and they help to destratify the air.”
“With 31-foot high ceilings, we know that lots of our heat is going into the area above the employees,” says Mr. Short. “That’s no good. In the winter, we slow them down. The fans push down hot air from the ceiling. It’s much more comfortable.”
Mr. Short knew that prior to installing the fans, his building had to be “overheated” to maintain a comfortable temperature for employees. That typically means setting the thermostat at a higher temperature with the hope that some of that warm air will work its way down to the floor. According to the Michigan Consolidated Gas company, compensating for this stratification of air is the single biggest waste of energy in buildings today.
With a 1 horsepower motor, the fans are said to offer an inexpensive and efficient way to bring heat down from a plant’s upper area. That means turning down thermostats at floor level.
Comparing then and now, Mr. Short says “Our heating units aren’t running constantly like they were before. It’s more comfortable in the summer, and in winter.”
Fans that cool in summer and heat in winter seem counter-intuitive, but it all depends on the speed at which the fans rotate. The slower rotation of fans in the winter moves huge volumes of air more slowly than it does in summer conditions. By doing so, Big Ass Fans force heat that collects near the ceiling to be distributed more thoroughly and evenly throughout the facility.
Employee comfort means more than just saving money on energy costs. Research has proven that worker satisfaction with the plant environment translates to as much as a 15 percent increase in productivity. Improvements in climate conditions are the biggest contributing factor. That’s because temperature, humidity and air circulation make the most immediate and noticeable difference to employees.
“I can’t believe how much attention these fans generate,” says Mr. Short. “We have a robotic pallet stacker. It’s pretty impressive, but lots of people come here and want to talk about the big fans. I get calls from people interested in how well they work.
“I think they address a real big problem in buildings like ours. In winter, high ceilings eat up hot air. In the summertime, the hot roof heats the building. The fans have taken care of the problems we had with climate control. On high speed, they cool our employees. On low speed, they push hot air down from the ceiling.”
Mr. Short says employees are now much happier. He’s happy, too. “We were among the first companies to install the fans. We’ve had them for 4 years now.
According to Mr. Short, the fans use minimal energy, and never break. He adds, “In my line of work, that’s one of the best things that can happen. We run them 24/7.”