Effects of Brownouts, Surges, and Blackouts on HVAC Equipment

  • August 5, 2019
  • Len D'Amico

As most everyone is aware, power surges, brownouts, and blackouts can wreak havoc on electronic equipment. Power surges may be the result of weather, the demand for power during a heat wave, a weak electrical grid and infrastructure, or even something as tragic as a vehicle crashing into a utility pole, knocking down power lines. Regardless, when the supply of power to your business is interrupted or altered it can have devastating consequences. And although many people use a surge protection device on their expensive electronics at home, they are not as well prepared for their business’ HVAC equipment.

A brownout is defined as the power supply dropping more than 10% and is usually the result of the utility company rationing electricity to avoid a more devastating blackout. As a result, HVAC equipment is forced to draw more current due to the loss of voltage. The components of the system operate under a greater strain in order to compensate for the loss of power.

When experiencing a brownout, you may notice a flicker in the lights. After that interruption to electrical power, most air conditioning systems re-start with no apparent problems. But sometimes your HVAC equipment may not come back on, or if it does, it’s blowing warm air. It may also get stuck running non-stop and won’t shut down.

In many cases, severe damage can occur. This is a partial list of conditions and issues we’ve seen after blackouts and brownouts:

  • Reversed phases of two of the three power legs in electrical service
  • Burnt-out compressors
  • Damaged compressor windings
  • Control board damage or burnout
  • Transformers, relays, and contactors damaged or fried
  • Damaged evaporator and/or condenser fan motors

Not all of these issues necessarily stop your system from running immediately after an interruption of power service. In fact, when the power company reverses the phases of power legs, a scroll compressor and 3-phase motors run backwards. At first, they seem to be working but inevitably are damaged beyond repair. In the case of damaged compressor windings, it’s only a matter of time before the system will fail – when windings are damaged, acid is released into the refrigerant circuit and must be cleaned up.

Many large businesses and critical government and NGOs have uninterrupted power supplies, such as backup generators, to mitigate against the effects of power interruption or quality. However, they are expensive and not always necessary for smaller or less critical organizations.

An inexpensive way to prevent damage to your HVAC equipment is to add a phase monitor to the most critical pieces of equipment you require to keep operating. A phase monitor is a simple and inexpensive control that can save the need for costly repairs. Contact your HVAC service provider to see how they may help insure your business keeps running when the inevitable happens.

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