Line 2 has suddenly malfunctioned. Now a condensation removal system heater stays on full-time, even though there's no call for it this time of year. A small PLC stopped working, and none of the motors run.

The responding tech decided to start with one of the motors and found its fuses were blown and its neutral wiring charred. Your boss asked you to fix this, and his parting words were, “I told them it sounded like lightning to me, but they say they have a surge protector and it is working.”

Where should you begin in determining the cause?

This does sound like a surge induced by lightning, and your boss gave you an excellent clue as to why it did so much damage. They have “a” surge protector? There is no single surge protector that can reduce the energy of a big surge down to something that won't fry control devices and wiring.

The fact this facility has a single surge protective device and has this specific kind of damage is a good indication that it's time to install a tiered surge protection system in this facility. With such a system in place, any surge that comes through the service will be reduced to a safe level by the time it reaches the control devices and wiring.

But what if this particular surge wasn't from lightning? A big motor, such as a fire pump, starting across the line could be the culprit. Perhaps the damage has been cumulative, and only now did it add up to a chain of component failures. So, look for those big loads. Consider a soft start to solve the root cause.

Grounding helps keep surges from entering the building, but it doesn't protect individual equipment. Whether generated from inside or outside, undesired currents travel along metallic pathways. To prevent a high voltage differential between metallic objects, bond all of them per Art. 250, Part V of the NEC.