by Brian Kaupp
December 2003

Environmental systems continue to become more complex and owners and occupants often have expectations far beyond the designed capabilities of the system. Testing, adjusting and balancing personnel no longer can be just instrument readers. They must understand how heating, ventilating, and air conditioning ("HVAC") systems function as well as be able to properly test and balance these systems. Mechanical engineers and installers have a responsibility to provide to the owner, a functional HVAC system, which should include a certified test and balance report.

 Why use an AABC (Associated Air Balancing Council) or a NEBB (National Environment Balancing Bureau) certified firm?  There are some misconceptions on how a firm/individual gets certified; one misconception is that a fee is paid and you are certified, another is that after a period of time of performing testing and balancing a person fills out an application and he/she is now certified.  In actuality, certifying a firm involves strict conformance to high standards and procedures established by each organization, the employment of qualified supervisors and technicians, the possession of certain necessary instruments, a competent instrument maintenance program and continuing education just like any other professional organization.

Both organizations, AABC and NEBB, have comprehensive tests: AABC involves a site interview and an 8-hour written exam. NEBB involves an 8-hour written exam and an 8-hour practical exam on air and water balancing. Here are a few examples of test questions that an applicant would find on either test:

Example 1: A cooling tower rejects 960,000 BTUH with a flow rate through the tower of 192 GPM of condenser water.  The drift rate is 2%.  The blow down rate is 1.5%.  The required make up water flow rate is _____________GPH.

Example 2: An air handling unit has the following conditions:  6000 CFM of outside air at 30°F DB and 80%RH is mixed with 18,000 CFM of return air at 70°F DB and 40 grains of moisture. The required discharge condition is 95°F DB and 70ºF WB. The mixed air condition is ________°F DB and ________°F WB.

The above indicates the level of knowledge and understanding that a certified testing and balancing firm brings to the HVAC team. This type of knowledge and following of national procedures can not be guaranteed from a non-certified firm. There is no organization that governs a non-certified firm, no organization that requires calibrated instruments and what procedure is that non-certified firm following?

 The AABC and NEBB organizations also provide a national performance guaranty, which offers a solution to engineers and building owners in the event that the requirements of the project are not met by the test and balance firm. Under the terms of the guaranty, the organizations agree to promptly investigate any written complaints from engineers and building owners. Based on its findings, they would take appropriate action to resolve any problems associated with the complaint. A non-certified firm can not provide an engineer or building owner this performance guaranty.

Anyone can read an instrument, but a certified firm has experts to test, evaluate and problem solve.  In the world of engineering, the letters P.E. mean there is a level of knowledge that is expected. It is the same in testing and balancing. The letters AABC or NEBB mean a high level of knowledge and understanding of HVAC systems is expected from the test and balance firm.

To find a listing of certified firms, visit
www.AABCHQ.com  and  www.NEBB.org