Modern control systems are almost always digitally based. Or, most importantly, they run on low voltage for system communications. Thus, controls are sensitive to voltage spikes from a variety of sources on the communication wiring.
Control system sensors are typically located far away from the system processors and are connected with low voltage wiring to the system communications. Long metallic wires act as an antenna to pick up surges from a variety of sources. The remote sensors and actuators are usually grounded wherever they are mounted.
These multiple grounds allow surges from ground voltage differences to enter the communication wiring. Once surge energy is allowed on the communication wiring, all devices that communicate are subject to surge damage.
Now imagine the hours of field time it takes every year to replace damaged sensors and actuators distributed throughout the local area. If you are a building owner, controls repairs and maintenance can be a considerable expense. If you are a controls installer, a single sensor damaged at a customer site means you travel to that site carrying replacement parts. It’s an expensive process.
Surge protection installed on the controls communication system, sensors, and actuators have proven their value over years of real-world installations. When owners realize the value of surge devices, they have installers place surge protectors on their controls. Some installers even look at the value of surge as savings in “windshield” time- if it takes a long drive to get to a customer site, then they install surge protection. In most cases, it is a better value to protect your controls with surge protection than to risk damage, downtime on your controls, and repair costs.