FM Frequency: Balancing Act
By Jeff Crane, P.E., LEED® AP
Published in the January 2006 issue of Today's Facility Manager
FM Frequency ended 2005 with a challenge to identify and eradicate wasteful energy in facilities’ boiler operations. If your building doesn’t have boilers, and the December article was more useful for lining the birdcage, put down the scissors. It’s a new year and if you (like many) have the post-holiday-utility-budget-busting blues, this month’s column might give you some ideas for fine tuning your facilities and perhaps saving a few utilities dollars.
Regardless of the energy source, powering and heating facilities this winter (electricity, wind, natural gas, propane, fuel oil, or even the sun), most buildings have a critical system whose primary duty is stirring and mixing and bringing us comfort. If you’re nodding and fondly thinking of the margarita blender in the office kitchen—get hold of yourself—that’s not what I meant.
I’m talking about fans and air handlers. Whether they are enormous chilled water “swamp coolers” (built up air handlers common in textile mills) or small and simple furnaces, most facilities have at least one fan system responsible for moving and mixing the conditioned air. There’s no need to get bogged down studying fan curves, pulley diameters, sheaves, v-belts, rpm, and horsepower. All you need to remember is this: most buildings’ air handling systems are improperly balanced—often with too much exhaust or too much ventilation resulting in wasted energy and building pressurization problems.
Your favorite architect and mechanical engineer probably don’t agree on much—particularly the appropriate size of mechanical rooms. But they probably would agree that an ideal building maintains a slightly positive pressure relative to the outside. This is achieved by bringing in a little more outside air than is removed with exhaust systems, but not too much. This balancing act between fresh air and exhaust helps maintain acceptable indoor air quality (IAQ), prevents uncontrolled moisture migration, and improves control of the HVAC systems.
Before confirming the facility’s air balance diagnosis, you need to do a little homework. Facility managers without mechanical system experience or without access to accurate building design drawings and specifications can spend some time surveying the facility with a licensed mechanical engineer to compile valuable information.
A qualified engineer can apply ASHRAE Standard 62 and local mechanical codes to determine exactly how much exhaust and fresh air is necessary (and where it belongs) based on current building use, people occupancy, and existing air distribution equipment. Carbon dioxide monitors and other occupancy sensing control strategies can be considered for buildings with fluctuating people loads or inconsistent operating hours (schools, churches, entertainment complexes). [To read about an entertainment facility, see “Beautiful Music” by Anne Cosgrove.] A creative but deliberate approach can allow a facility manager to conserve energy in applications while maintaining compliance with codes, providing acceptable IAQ, and achieving appropriate building pressurization.
Once you determine the required exhaust and fresh air rates and a control strategy, you need to test and balance (T&B) the system components physically and see if those requirements are met. If you don’t have test equipment and expertise on staff to conduct the T&B, you can hire a mechanical contractor or specialty T&B firm.
When researching and comparing suppliers, it’s a good idea to speak with professional references and ask about certification from the Associated Air Balance Council (AABC) and/or the National Environmental Balancing Bureau (NEBB).
During the T&B, improperly operating equipment is adjusted and airflows are set to the new specifications. Older buildings with dated equipment may be unable to satisfy current needs. This awareness and documentation can help generate project proposals that include energy, health, and potential liability justifications.
This process is part of the commitment to operational excellence known as commissioning. Many in the industry confuse the terms commissioning and start up. Start up is what is done with building systems when they’re first installed or when a space is first built. From Chapter 42 of ASHRAE’s HVAC Applications CD (2003):
“Commissioning is a quality assurance process for buildings from predesign through design, construction, and operations. It involves achieving, verifying, and documenting the performance of each system to meet the building’s operational needs within the capabilities of the documented design and equipment capacities, according to the owner’s functional criteria. Commissioning includes preparing project operational and maintenance documentation and training operation and maintenance personnel. The result should be fully functional systems that can be properly operated and maintained throughout the life of the building.”
Kicking off the new year with an air distribution review can help confirm that you’re complying with IAQ standards and running your buildings as efficiently as possible. Happy New Year!
Crane is a mechanical engineer and regional property manager with Childress Klein Properties, a leading real estate developer and property management services provider in the Southeast.
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