Power quality in HVAC applications

November 22, 2017 // By Steve Hughes
Most people can remember a time when they've walked into a room and seen one person dressed for the arctic while the person next to them looks like they're in the Bahamas. 

Although disagreements over heating like these have led to fights in some offices, for most businesses poor power quality in HVAC systems can do more damage financially. This article explains how to keep your HVAC running cool when things get hot.

Power quality is a term that many people use but few fully understand. Typically associated with a stable supply of mains electricity, power quality covers a range of problems, including the continuity of the supply of electricity, fluctuations and spikes in voltage and current, as well as transients or harmonic currents.

For years, power quality was a problem almost exclusively reserved for industrial applications. When manufacturers began using non-linear, switched, devices like variable speed drives (VSDs) to control the speed of a motor driving a conveyor belt, they had to pay attention to the effect these devices have on the mains supply.

The use of switch-mode power supplies (SMPS) results in harmonic currents in the electrical supply. Here, the current waveform expands to accommodate multiples of the fundamental 50Hz frequency. This means that the device using power is not only consuming more electricity — sending energy bills through the roof — but it can also cause motor windings and transformers to overheat and lead to inefficiency and possible breakdowns.

In recent years, the popularity of SMPS in computer systems and laptops, as well as in phone chargers and consumer electrical equipment, has created a power quality problem in HVAC applications. Combine this with the fact that most buildings, offices and residential and commercial facilities have some form of heating, ventilation and air conditioning (HVAC) it is easy to see the scale of the problem. Poor power quality can damage HVAC components including heat exchangers, fans, pump motors, condensers and furnaces, reducing their lifespan and raising energy costs.