An air distribution system includes the fans, ducts, and filters associated with heating, cooling, and ventilation. When we look at energy consumption by building; heating, cooling, and ventilation are among the top three energy consuming systems. Common optimization measures include re-calibrating thermostats, inspecting system dampers, and rightsizing fans to match the needs of your building. A study conducted by the U.S. Environmental Protection Agency found that nearly 60 percent of building fan systems were over-sized by at least 10 percent. The study found that on average, fans were over-sized by 60 percent.
Before exploring the energy efficiency opportunities available for your air distribution systems, we must first understand the difference between a constant volume (CV) system and a variable air volume (VAV) system. A CV system allows air to flow consistently during operating hours while a VAV system controls the amount of airflow based on changes in heating or cooling load. Although VAV systems are generally more energy efficient, regular maintenance is required to keep any system operating as intended.
Rightsizing fans is an effective way to improve the energy efficiency of your air distribution units as rightsized fans will meet your current airflow requirements, increase occupancy comfort, and increase the equipment life of your variable speed drives. Rightsizing fans can also prevent any cycling losses. Cycling losses further decrease the efficiency of your system by powering on or off throughout the day. For example, a boiler that short cycles several times in an hour may be 30 percent less efficient than its steady state efficiency.
“The best way to avoid cycling losses is to right-size equipment and to ensure that equipment can meet a variety of loads,” says 360 Energy Group Engineering Director, Simon Nowak. “This can be achieved through proper design and through equipment tuning in a program such as retro-commissioning.”
Rightsizing a supply fan can also be done by inputting larger pulleys, adjusting static pressure, or installing smaller motors. Larger pulleys will reduce the speed and fan power associated with your system so that you can match your peak load requirements while saving energy. For VAV systems, adjusting static pressure is an easy way to reduce the horsepower consumption of your fans. To match the lower power requirements for your right-sized fans, it may be necessary to install a smaller motor. The Energy Star building manual for air distribution systems states that rightsizing a 75hp motor to a 50hp motor could reduce motor energy consumption by 33 percent.
Other energy efficiency opportunities for your air distribution systems include re-calibrating your thermostats and inspecting your dampers. Pneumatic control systems require frequent calibration every six to twelve months. This upkeep will ensure that your thermostats are working correctly and can prevent control errors down the line. Another maintenance measure to keep up with is inspecting your unit’s dampers. Dampers are a key component to energy efficiency, but if not working correctly can have adverse effects on your overall building performance.
Keep your building operating efficiently by looking at your air distribution systems to right-size fans, re-calibrate thermostats and inspect system dampers. To make sure your building is running as intended, consider retro-commissioning to identify ways to improve the overall efficiency of your energy consuming systems. Contact 360 Energy Group, Senior Program Manager, Ryan Curry at 312-267-2864 or ryan@360eg.com to take back the control of your building.
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