Air balancing is a small profession with less than 3,000 commercial supervisors certified by four major organizations. There are fewer than 7,000 residential balancing professionals certified by National Comfort Institute. So, there are less than 10,000 certified air balancers in the world today. (For comparison purposes, there are over 800,000 brain surgeons in the world.)
This relatively small band of practitioners tests and adjusts the performance of operating HVAC systems and manipulates control devices and fan speeds to bring the system into a state of compliance with design specifications.
Measurements that air balancers take include a broad number of airflow tests, air velocities, static pressures, wet and dry bulb temperatures, fan speeds, and values. They also gather essential electrical and fuel consumption, dimensional measurements, installation documentation and manufacturer’s nameplate information. This data is captured in extensive reports containing an average of 200 data points for each system. This data is then compared to the field test measurements and to the specifications of the system designer, industry standards and the manufacturer’s specifications.
When used in this manner, a reasonable improvement in energy consumption is found to be in the neighborhood of 8% to 13%. Performance improvement can be determined by comparing delivered system BTU with specified or rated BTU, combined with energy consumption tests or interpretations form manufacturer’s specification. Live system EER can be measured, although very accurate and extensive testing and data collection is needed.
Although the test data is available, traditional air balancing reports rarely apply the data in this manner. Most reports and certification organizations simply show compliance through airflow at the grilles and match up field test numbers with engineer or manufacturer provided data only.
A study of today’s HVAC energy efficiency websites indicates that energy is saved by installing high efficiency equipment and sealing leaky ducts. Although these two actions may and often do reduce energy consumption, both actions may also increase energy usage in an installed system. Measuring the performance characteristics of an HVAC system, or air balancing, has been the prescribed method of testing and adjusting a system to maximize and verify performance and energy consumption since Willis Carrier and Dave Lennox made their first equipment.
A Shift in Perspective
Traditionally air balancing is a required step in the construction process. Even today on most commercial HVAC projects, engineers specify an air balance report to be submitted at the end of each job documenting a series of tests and adjustments. This type of air balancing still dominates the balancing profession today.
In the early 90’s a new application of air balancing emerged. A handful of air balancers began to use the same tests, but completed them in association with an engineer or system designer, prior to a HVAC system renovation. Balancing went from being a service included at the completion of a project, to a service provided at the beginning of a project. The purpose was to identify system performance defects, diagnose problems and provide essential information needed to redesign the system and correct comfort and efficiency defects.
Over the past 20 years this practice has redefined air balancing into HVAC system performance testing and diagnostics. This testing and diagnostics, coupled with the resulting renovation of the system, offers far greater results in energy savings than just balancing alone. Balancing combined with the needed repairs that are revealed produces an average energy savings of over 30% for residential systems and average commercial energy savings of over 20%. But that’s another article.
Where do the Savings Come From?
Let’s focus on savings produced by testing, adjusting and balancing alone. Air conditioning, heating and ventilation equipment is designed and built to perform at peak efficiency under a narrow set of operating parameters. When equipment is installed as part of a system, in a manner that forces operation outside of design specifications, performance and efficiency suffers.
Adjusting airflow, combustion, refrigerant charge, pressures, and energy consumption to comply with manufacturer’s specifications obviously increases performance and increases system efficiency. For this reason the ACCA Quality Installation Standard has gained wide approval from manufacturers and energy efficiency groups. In addition to better performance, equipment life is increased and warranty is reduced.
As the specified airflow over a system is obtained, heat transfer from the equipment peaks, compressors and heat exchangers function under the conditions they were designed to, fan power finds the level of performance it was meant to perform, duct loss is minimized and system controls are satisfied, which reduces run time. When a building has equal thermal comfort and adequate ventilation, thermostat settings are naturally lower, not mention the increase in total comfort, the primary reason the system was created.
A study of manufacturer’s performance data will show that lower airflow only reduces performance 3% to 5% if airflow is reduced 25%. As we compared that statement to field data, we questioned that claim. In order to maintain lower performance, either refrigerant charge or combustion must be adjusted under laboratory conditions as airflow is lowered. This doesn’t happen in the field. The effect of lower airflow on an installed system with an air distribution system magnifies the problem significantly, and run time increases substantially.
A test was completed this winter where a system in a home in the Midwest was run overnight and the system used just over one Therm of natural gas to maintain the temperature of the home. The following night under exact operation conditions and time, the same test was conducted, except the end caps of the supply ducts in the basement were removed. The fuel consumption increased over 10 times.
As the HVAC industry and the building science communities continue to unite in the study of building and system performance, we’re confident the energy efficiency of properly tested, adjusted and balanced HVAC systems will be included in field studies and research.
Rob “Doc” Falke serves the industry as president of National Comfort Institute a training company with technical and business level membership organizations. If you're an HVAC contractor or technician interested in a free air test and balancing procedure, contact Doc at [email protected] or call him at 800-633-7058. Go to NCI’s website at nationalcomfortinstitute.com for free information, articles and downloads.