Best Practices in Surge Protection for HVAC Systems

It’s almost impossible to imagine a modern building without heating and air conditioning. Today’s HVAC systems not only help ensure the comfort and health of building occupants, they also support temperature and humidity control for a wide range of facilities and purposes, ranging from industrial processing to storage of materials and goods. While we think of these systems as heavy equipment, they are actually controlled by sensitive electronic circuits – and are thus vulnerable to damage from electrical power surges and spikes. To prevent damage to these vital control functions, system designers should include surge protection as part of every installation plan, and maintenance staff should consider adding surge protection to any system that was installed without adequate protection.

Some HVAC technicians may not be aware of current best practices for surge protection, or the latest surge protection devices available for this purpose. Here are four best practices to improve surge protection for HVAC at your facility:

Element 1: Knowing that surge protection is necessary

Many elements of HVAC systems are robust and heavy-duty – comprised of substantial motors, blowers, fans, chiller pumps, and similar equipment. This may mislead installers into thinking that such systems can’t be damaged by unseen events, including the subtle, everyday power surge events that normally pass by unnoticed.

Savvy HVAC technicians know that the reality is very different. While many parts of HVAC systems are indeed rugged, the brains of the system, including sensors, controllers, timers, and similar components, are all made up of sensitive electronics that must be protected to prevent unnecessary damage and downtime.

Best Practice #1:

Insist on including surge protection for any new HVAC installation, and evaluate the addition of surge protection to any currently installed HVAC system that is not protected.

Element 2: Two levels of input power protection

Many facility managers understand the need for surge protection, but may still have the question of how much protection will be adequate for the purpose. For example, building managers know that it is good practice to install surge protection at the service entrance of the building. Is that enough to provide protection for all the electronic systems within the facility, including the HVAC?
The answer is no, for two reasons. The first reason is that while building-level protection will provide some isolation/safety from externally-generated surge events, many smaller surges can be created from within the building itself and cause damage to the HVAC control system. These internally-generated surges can come from a wide range of activity, including those that draw significant power such as welding, and also from exactly the type of large motors that are found in HVAC systems, among other places. Thus, the surge protection installed at the service entrance will not entirely prevent power surges from reaching the HVAC controller circuits.
The second reason is that the surge protection devices installed at the building entry are unlikely to be tailored to the specific systems within the facility that need protection. For example, commercial facilities usually have electrical supply voltages higher than 120 volts – up to 20KV is not uncommon. Step-down transformers are used to supply the various voltage requirements of internal equipment. Therefore, the surge protection devices that are appropriate for protecting power at the service entrance help protect from external surge sources, they are not effective for each type of system within the facility.

Best Practice #2:

Best practices recommend a first layer of protection at the service entrance of a facility, and a second layer of appropriate protection at the power connection of every sensitive piece of equipment for maximum effectiveness.

Element 3: Protecting the thermostat

Now we understand that best practices recommend protecting the HVAC system at the electrical disconnect. Is protecting the power connection sufficient to protect the entire HVAC system?
The truth is, protecting the HVAC system at the power disconnect is a great start, but that will not protect the entire system. Another threat of surge energy often comes from the thermostat wire that connects to the externally mounted condensing unit. HVAC thermostats are sensitive devices that are particularly vulnerable to surge damage because of their normally low operating voltages. Because the system is often spread over several locations within and outside a building, there is the possibility that the low voltage connection cables could transmit surge currents to the thermostat and cause damage. These surges could be created by accidental contact with power cables or other electrical failures.

Best Practice #3:

Provide a third layer of protection using an additional low voltage surge protection device to protect the thermostat from damage.

Element 4: Ensuring ongoing protection

Based on the best practices described above, responsible facility managers have ensured that appropriate surge protection is installed at the building service entrance, at the HVAC electrical disconnect, and to protect the thermostat. When these three layers of protection are installed, has the surge protection challenge been solved?

Unfortunately, the truth is that electrical surges are a daily event, and many smaller surges happen without being noticed. Surge protection devices are designed to sacrifice themselves to protect their attached equipment. This can happen all at once in the event of a severe power surge, or it can happen over time as smaller surges gradually take their toll. In either case, the surge protection devices will eventually become degraded and will need to be replaced. To ensure continuing protection, a routine inspection program is needed to check on their status and identify any devices that require replacement.

Best Practice #4:

Implement a routine inspection program to ensure continued protection.

Regardless of the type of building you manage, HVAC systems are important for your success. You can take proactive action to help ensure that your HVAC systems are as reliable as possible, and avoid unnecessary downtime and repair costs by following these four best practices. Make sure to include surge protection as part of every new HVAC installation and consider adding surge protection to any system that was installed without adequate protection.

At DITEK we are dedicated to building rugged, dependable surge protection solutions. Contact us to learn more about how to protect your HVAC systems.