For a transformer vault located on the 2nd floor of a high-rise building, the minimum height of an oil-confining sill below the door into the vault is how many inches?

For a transformer vault located on the 2nd floor of a high-rise building, the minimum height of an oil-confining sill below the door into the vault is how many inches?

• A. 3 inches
• B. 2 inches
• C. 1 inch
• D. 4 inches

Answer: (D)

Oil containment is about keeping any oil that might leak from an oil-filled transformer from spreading beyond the vault. The door into the vault sits over an oil-confining sill that acts like a dam. Requiring a minimum height of four inches ensures that if oil leaks or drips, it will be trapped in the sill area rather than running onto the floor and toward the building’s egress. This height provides a practical volume to contain leaks typical for transformers and helps maintain a safe, non-spill environment around the doorway in a high-rise setting. Lower heights would be more likely to allow oil to escape under the door, increasing fire and environmental hazards, so the four-inch sill is the standard.

Oil containment is about keeping any oil that might leak from an oil-filled transformer from spreading beyond the vault. The door into the vault sits over an oil-confining sill that acts like a dam. Requiring a minimum height of four inches ensures that if oil leaks or drips, it will be trapped in the sill area rather than running onto the floor and toward the building’s egress. This height provides a practical volume to contain leaks typical for transformers and helps maintain a safe, non-spill environment around the doorway in a high-rise setting. Lower heights would be more likely to allow oil to escape under the door, increasing fire and environmental hazards, so the four-inch sill is the standard.