Under-floor cable trays can be bonded to which grid if present?

• A. Flooring bonding grid
• B. Ceiling grid
• C. Grounding grid
• D. Primary grid

Answer: (A)

The main idea is equipotential bonding of metal in the floor area. Under-floor cable trays are metallic and can carry fault currents or develop voltage differences with other grounded metal on the floor. If a floor bonding grid is present, bonding the trays to that grid ties them to the same electrical potential as surrounding floor metal. This creates a safe, low-impedance path to equalize potential, reducing shock risk to personnel and helping control stray currents and interference.

Ceiling grid isn’t the targeted bonding path for under-floor installations, and a grounding grid refers to the broader earth-ground network rather than the localized floor bonding plane. The flooring bonding grid is specifically intended for bonding floor-mounted metal work like under-floor trays, so it’s the best choice when available.