Master Electrician Exam (NEC)Grounding and BondingMedium
A master electrician is installing a lightning protection system on a commercial building. According to NEC 250.60, what is the requirement for bonding the lightning protection system to the building's electrical grounding system?
- AThey must be kept entirely separate to prevent lightning energy from entering the electrical system.
- BThey must be bonded together at multiple points to maximize lightning current dissipation.
- CThey must be bonded together at a single point to equalize potential.
- DBonding is only required if the building contains sensitive electronic equipment.
Show answer & explanationAnswer & explanation
Correct answer: C. They must be bonded together at a single point to equalize potential.
NEC 250.60 requires that the lightning protection system grounding electrode system be bonded to the building's electrical grounding electrode system. This bonding provides a common reference point and helps to equalize potential between the two systems, preventing dangerous voltage differences during a lightning strike.
Why the other options are wrong
- A. Keeping them separate can lead to dangerous potential differences between the two systems during a lightning strike.
- B. While multiple paths for lightning dissipation can be beneficial for the lightning system itself, the bonding to the electrical system is typically at a single point to prevent circulating currents and ensure equipotential bonding.
- D. The requirement for bonding is for safety and equipotential, regardless of the presence of sensitive equipment.
Lightning Protection System Bonding
The grounding electrode system of a lightning protection system must be bonded to the building's electrical grounding electrode system to ensure equipotential and prevent dangerous potential differences.
- Required by NEC 250.60.
- Prevents dangerous side flashes.
- Creates a common ground reference.
Memory trick: Lightning and power: one bond, one ground.