- Determine how the building is grounded. Is it bond-grounded through structural steel?
- Is conduit used as a ground or is a grounding conductor used in all instances?
- Is grounding of the neutral done correctly, i.e., at the service entry panel, at all separately derived devices (transformers, generators, and UPS only and nowhere else), i.e., in outlet boxes or in power panels?
- Where is the grounding system located and what gauge wire leaves the service entry panel?
- What is the primary method used? (Connection to a cold water pipe is normally the primary method.)
- What is the secondary method used? Is it buried below the permanent frost line? (Secondary methods normally consist of a counterpoise system, ring around the building, single or multiple grounding rods, or rods forming an equilateral triangle.)
- What is the condition of the electrical grounding system?
- When was the system last tested?
Glossary of Terms
Air Terminals—Also referred to as lightning rods, these copper or aluminum rods are vertically mounted on a structure’s roof or top at various high points. Positioned to protect above the roofline, the rods are designed to intercept lightning strikes.
Main Conductors—Made of copper or aluminum, these cables connect air terminals to grounds. Conductors are coursed inside the framing spaces during construction of the building, hidden from view and protected from corrosion. On existing buildings conductors may be coursed behind down spouts or other parts of the building.
Grounds—Main conductors are attached to metal ground rods that are set at least 10 feet deep in the earth. Special grounding requirements are sometimes necessary in sandy or rocky soil.
Bonds—The bonding connects grounded metal objects to the main conductor cable and prevents side flashes (lightning jumping between two objects).