Power quality in HVAC applications

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. Here, Steve Hughes, managing director of REO UK, 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.

Facilities managers responsible for a building’s HVAC system are also obliged to meet industry standards such as EN61800-3, which specifies the limits of electromagnetic emissions, immunity levels and testing methods for power drive systems (PDS) — the parts of a VSD that control driven equipment.

The standard identifies four categories where PDSs can be used in one of two environments. The first environment looks at domestic premises, low voltage networks, houses, apartments and residential buildings. The second looks at industrial buildings and those supplied by a dedicated transformer such as factories and plants. Depending on the category, the standard either lets anyone install the PDS or requires installation by a professional.

According to the standard, a PDS rated at less than 1000V can be installed by anyone in domestic premises. This is already causing problems as the demand for apartment buildings grows. Apartment buildings typically use more sophisticated building management systems, with electronics controlling the heating, lifts, extraction, doors, telecoms and internet-over-mains connections, all of which can be compromised by poor power quality, ultimately hampering the user’s experience.

To enable facilities managers to use drives properly in their HVAC system, REO UK has developed an entire suite of products dedicated to eliminating power quality problems in HVAC applications. The REO Unity range comprises electromagnetic compatibility (EMC) filters, mains chokes, output chokes, sinewave filters and powerline filters.

So, the next time you feel like wearing your shorts to the office, make sure your HVAC system is running as cool as you look.


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