Lightning is one of the primary causes of failure in submersible motors. Without any protection a submersible motor has approximately a 30% chance of damage by lightning-induced surges within a year. Each year lightning strikes 16 times for every square mile, starts 75,000 forest fires and, according to the National Weather Service, kills 40 Americans every year. Lightning is also one of the primary factors in the failure of submersible motors. A direct hit during a storm can knock a motor out immediately; however, it is usually a power surge that causes damage. When a motor is hit with a voltage surge a carbon track is left in the motor, and with each following surge the carbon track builds.
Eventually, the carbon pathway becomes such a super highway that normal operating voltage causes further damage, resulting in motor failure. Lightning-induced damage can occur regardless of the make of the motor, design or lubrication system; two-wire motors are hit just as often as three-wire motors, and lightning doesn’t know the difference between hermetically-sealed and oil-filled submersible motors.
So, what really happens when lightning strikes? Lightning simply wants to be grounded, and the water deep in the earth creates an outlet; however, the submersible water well system is right in the way. When a power surge hits, the conventional lightning arrestor causes the surge to travel down both the ground and lead wires. The voltage surge travels down the lead wire looking for ground; as the surge reverses, it meets the split portion of the surge and both parts of the surge join, doubling the voltage. The doubled voltage can be too much for the motor to handle, causing damage and knocking out the water system.
Even though the pump was installed correctly and a lightning protector was installed, there can still be a surge that even a properly grounded arrestor is powerless against. The key to preventing lightning damage is to divert the lightning to ground instead of having it reflect back and cause more damage.
Franklin Electric provides built-in surge protection in single-phase motors, either in the motor itself, or in the control box. For example, all 4-inch Super Stainless motors have surge arrestors in the motor itself. The same holds true for 4-inch 3-wire motors from 1/2 to 5 horsepower. In the larger single-phase motors, surge arrestors are provided in the Franklin control box. Surge arrestors are also built in to 3-phase Super Stainless motors from 1/2 to 3 horsepower, but only in the 200 and 230 Volt ratings. Note that in other 3-phase installations, you will need to supply surge protection in the 3-phase panel.
No matter where they’re located, surge arrestors all work the same way. They’re in contact with ground, and when a power surge occurs, the arrestors work by simply diverting the surge to ground. Laboratory and field tests indicate that the arrestor life, in situations where repeated surges can be expected, are consistent with typical submersible motor life expectancy.
When you pay for a Franklin motor you pay for protection. Aboveground motor installations take time and cost customers a lot of money. The Franklin advantage is total protection for less money. The Franklin Super Stainless submersible with built-in lightning arrestor is your best protection against lightning damage, saving you time, effort and the possibility of an unsatisfactory aboveground arrestor installation.