The four types of HVAC surges (external power surges, internal surges, lightning surges, and switching surges) can prevent up to 60% of system failures.

Introduction to HVAC Surges

Speaking of indoor climate control, we need to use HVAC systems in both winter and summer, which are one of the most sensitive components in the house and can be seriously affected and damaged by a variety of different power surges. Understanding these power surges is very important to maintain and improve the life and performance of your HVAC equipment.

Power surges from external power sources

Ultraviolet radiation can affect your circuits, or external power surges (due to grid problems or construction sites near your home) can suddenly introduce higher voltages from the power supply. For example, a common power surge from an external power source will increase the voltage from the standard 120 volts to over 169 volts. This sudden rise can overload the electrical components on your HVAC system and cause failure or loss of efficiency. To prevent this, it is necessary to install surge protectors and voltage stabilizers.

Internal power surges

Internal power surges are generated inside a building, usually when operating high-power equipment, such as elevators, powerful motors, or additional HVAC systems. These are temporary spikes, although they can be 10 times the normal operating voltage. For example, when a large motor starts up, it can produce a large surge that affects the HVAC system. These internal surges can be controlled with proper grounding and the installation of surge protectors.

Surges Caused by Lightning

Even an indirect lightning strike to a building can cause huge fluctuations in electrical wiring. A single lightning strike can deliver millions of volts into the system. Lightning strikes can account for 5% of all surges, which can plague your HVAC system. If you live in an area with frequent thunderstorms, it is critical to install lightning rods and ensure that your building's electrical system is properly grounded and that surge protectors are installed.

Switching Surges Within the System

Switching Surges occur when electrical equipment within an HVAC system is turned on or off. While these surges are generally lower in throughput compared to other surges, they can also cause wear and tear over time. An example is the brief startup of a compressor, which can deliver voltages as high as twice the normal operating voltage. While rare, regular maintenance and a properly specified HVAC surge protector designed for your equipment can help you handle these surges.

Power Surges from External Sources

Power surges from outside the building's electrical grid are the most common, and they can be very dangerous to HVAC systems. There are many factors that cause these surges, and they can easily wreak havoc if not handled properly.

Reasons Behind External Surges

Power quality events such as events such as grid failures, construction near a work site, and switching operations by utilities can be the primary cause of external surges. For example, a 6,000-volt voltage spike can occur as a result of a power company switching electrical loads. Construction equipment interfering with underground or overhead power lines can also create sudden and unpredictable surges.

Effects on HVAC Systems

Extra voltage moves through power lines and enters surge protectors through external hydro surges. This can overwork the system's electrical systems, such as circuit boards, compressors, and motors. HVAC units are susceptible to 6,000-volt surges, which can cause equipment to fail immediately or develop reliability issues over time, i.e., frequent failures or reduced capabilities.


To protect your HVAC system from external power surges, several precautions should be implemented:

Real-world use case

Now, imagine a commercial building located in a large metropolitan area that has constant problems with power fluctuations due to construction going on nearby. In a year, its HVAC system has several component failures, resulting in expensive repairs and long periods of downtime. The facilities management company installed surge protectors and voltage stabilizers, which reduced HVAC failures by 80% and increased the life expectancy of the equipment.

Internal Electrical Surges

As more and more large equipment comes online, buildings can experience internal surges that cause circuits to exceed their rated electrical load. If not properly handled, these sudden events can interrupt the normal function of the HVAC system and cause extensive damage.

Causes of Internal Surges

A common source of internal surges is the starting and stopping of high-demand appliances. This can include other HVAC components, elevators, refrigeration units, or large motors. When the equipment is turned on, these devices can generate surge currents up to 10 times the rated level. When a large motor starts, the line voltage can rise from 120 volts to 1,200 volts in an instant, so its operation will cause all connected equipment to deform, causing disconnection.

Effects on HVAC Systems

Internal surges can be a significant problem for HVAC systems. Such surges can cause fuses to blow, circuit breakers to trip, or circuit boards to burn out. Continuous surges wear out components over time and can mean warranty issues and more frequent maintenance. As many as 60% of HVAC system failures can be traced back to electrical problems, from internal surges to worn components.

Protective Measures

This is not a simple task, and protecting the internal components of your HVAC system from the threat of a surge requires a combination of the following measures:

Lightning-Induced Surges

HVAC systems are among the systems most affected by lightning surges. These surges are caused by lightning strikes and can quickly funnel enough energy into a building's electrical system to damage any number of its HVAC components.

Characteristics of Lightning Surges

Lightning that propagates through power lines can inject millions of volts into an electrical system or directly into a building. A single lightning bolt can generate a voltage surge of about 200 million volts. Even if a direct lightning strike doesn't hit an HVAC system, electromagnetic pulses (and surges generated by wires within a building) can be generated by indirect lightning strikes.

Effects on HVAC Systems

HVAC vs. Lightning Surges These surges can burn out circuit boards, blow fuses, and even turn compressors and other critical components into a pile of scrap metal in the blink of an eye. The extreme heat and energy released by a lightning spike can cause instantaneous and irreparable damage. For example, lightning-related surges are estimated to cost the U.S. more than $1 billion in electrical system damage each year.

Protection Strategies

To protect HVAC systems from surges caused by lightning strikes, several protection methods are employed:

Lightning Protection Case Study for Commercial HVAC Systems

A commercial location located in a lightning zone was frequently struck by lightning, which resulted in numerous power issues due to frequent damage to HVAC equipment. Installing a comprehensive lightning protection system, including lightning rods, high-capacity surge suppressors, and enhanced grounding, reduced HVAC downtime at the location by 90%. Lightning protection is also a safeguard for HVAC equipment, which has been shown to save a lot of money on repairs and replacements.

Switching Surges within the System

HVAC Switching Surges – An often overlooked condition in HVAC systems that can cause very serious system performance and lifespan impacts. They are caused by the normal function of electrical devices and appliances in the HVAC unit.

Causes of Switching Surges

Switching surges are generated by turning electrical loads on and off. Examples include normal cycling of compressors, motors, and fans. When a compressor starts, it creates a surge where the voltage rises to 2-3 times the normal operating level. Although short-lived, these spikes can create hot spots that stress electrical components.

Effects on HVAC Systems

Switching surges cause cumulative wear and tear on HVAC systems. Continued exposure to these surges can damage insulation, burn out circuit boards, and shorten the life of essential components. One study showed that HVAC systems exposed to repeated switching surges were 25% more likely to fail than those not exposed to surges.

Mitigation Strategies

There are many different ways to reduce the effects of switching surges:

Surge protection in industrial HVAC systems

High levels of switching surges cause regular downtime for an industrial facility with multiple high-capacity HVAC units. By integrating VFDs and installing surge suppressors at strategic points in the system, the facility has reduced equipment failures by 70%. This foresight has improved system reliability while also reducing maintenance costs and increasing operational efficiency.