Upgrading Of Fan System JC Penney Atlanta, GA
(The following is excerpt from U.S. EPA files)
The air distribution for one of JC Penney's 155,000-sf stores was provided by five air-handling units located in a penthouse equipment room. Two return fans, also located in the penthouse, vented air from the first and second floors through ductwork and back to the air-handling units.
The air-handling units supplied conditioned air through ductwork to diffusers throughout the building. The fans operated at two speeds, high and low, each manually controlled with selector switches as well as on-off automatic-function switches. The fans usually operated at the high-speed setting, although they were cycled occasionally to conserve electricity. In an effort to reduce energy consumption, tests were conducted to determine the airflow from each of the fans while operating at high speed. Data collected indicated that the actual airflow for each air-handling unit was less than the design air-flow; therefore the fans were larger than necessary for this facility. The testing also revealed that an accumulation of dirt on the cooling coils in air-handling units 1 and 2 was restricting air flow and wasting fan energy. QuikFan software (see our QuikFan software offering) was used to estimate the energy savings potential of various upgrade options. Measurements of each fan motor indicated that the maximum load was less than the horsepower rating. Another potential energy saver was minimization of the outside air brought into the building for ventilation. This air had to be heated or cooled, which required energy. By monitoring carbon dioxide levels in the building it was felt that the air in-take could be safely reduced to the minimum quantity necessary. JC Penney decided to install variable-speed drives on the supply-air and return-air fans in the building to bring the fan capacity nearer the actual load and to install carbon dioxide sensors(see oue publications #37, 29,84 and 31) that would enable the system to minimize the intake of air. The large open areas in the store made it impractical to install variable air volume boxes that control the speed of the fan motors with pressure sensors. Space thermostats were therefore used to regulate fan speeds directly. Before installation of the variable-speed drives, the fans cycled on at maximum electrical consumption and then cycled off regularly. The variable-speed drives eliminated this inefficient constant cycling. Peak power use was therefore less than the maximum, with projected electric demand savings of 36 kW per month. The total cost of installation of the variable-speed drives and the carbon dioxide sensors was $17,000, which is projected to save 138,833 kWh of electricity at an annual savings of $9,726. The payback for this upgrade of the fan system is 1.75 years, and the internal rate of return is 56.6 percent. JC Penney was therefore able to realize substantial annual savings with a relatively low investment, and the savings continue year after year.