A 45 kVA, 480 to 208Y/120-volt dry-type transformer is suspended below the ceiling of an equipment room where the ceiling is plywood attached to wood joists. The minimum clearance from the transformer to the ceiling is:

A 45 kVA, 480 to 208Y/120-volt dry-type transformer is suspended below the ceiling of an equipment room where the ceiling is plywood attached to wood joists. The minimum clearance from the transformer to the ceiling is:

• A. 4 Inches
• B. 3 Inches
• C. 6 Inches
• D. 12 Inches

Answer: (D)

The space above a dry‑type transformer must be large enough to allow heat to dissipate and to provide access for maintenance, especially when the ceiling is combustible. Heat rises, and with a plywood ceiling on wood joists, the NEC requires a larger vertical clearance to reduce the risk of heat buildup and potential ignition of nearby materials. Therefore, the minimum clearance from the top of the transformer to the ceiling in this case is 12 inches.

The space above a dry‑type transformer must be large enough to allow heat to dissipate and to provide access for maintenance, especially when the ceiling is combustible. Heat rises, and with a plywood ceiling on wood joists, the NEC requires a larger vertical clearance to reduce the risk of heat buildup and potential ignition of nearby materials. Therefore, the minimum clearance from the top of the transformer to the ceiling in this case is 12 inches.