Harmonic distortion is a problem that can severely alter the quality of power delivered to HVAC systems and can cause damage, disruption, or failure of HVAC equipment. It is primarily an "invisible" problem that is not widely understood among facility personnel, but its growing impact on HVAC operations makes it a pressing issue requiring an increased depth of knowledge and expertise.
Harmonic distortion is created by electronic equipment drawing nonlinear loads. In years past, when the current drawn by most HVAC equipment was linear or sinusoidal in shape, harmonics was rarely an issue. Today, however, virtually all electronic controls and variable frequency drives (VFDs) in commercial and industrial HVAC systems utilize power conversion technology that draws current in short, abrupt pulses that create distorted, nonlinear waveforms. These nonlinear waves produce reflective, or harmonic, currents that flow back into the power distribution system, degrading power quality. HVAC equipment and devices drawing nonlinear loads include VFDs for fans and pumps, electronic controls, chillers, heat pumps, and building automation systems.
Most buildings can manage nonlinear loads of up to 15% of the total system capacity, above which some troubling issues can occur due to harmonic distortion. These include overheating or failure of motors, nuisance tripping of circuit breakers, malfunction of building automation systems, unexpected shutdown of chillers or air handlers, voltage drop affecting compressor performance, and power interference on control systems. Severity can range from annoying (inconsistent temperature control) to costly (equipment failures) or dangerous (complete HVAC system shutdown in critical environments).
As our region’s leading service and diagnostics specialist, MSC can help clients navigate the complexities of harmonic distortion in critical HVAC, process cooling, and building automation systems. For more information, please contact us at 973-884-5000.
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