A transformer vault floor in direct contact with the earth shall be constructed of at least how many inches of concrete?

A transformer vault floor in direct contact with the earth shall be constructed of at least how many inches of concrete?

• A. 2 Inches
• B. 3 Inches
• C. 6 Inches
• D. 4 Inches

Answer: (D)

When a transformer vault floor is in direct contact with the earth, it must be a solid, thick concrete slab to safely bear the weight of the equipment, resist soil pressure, and limit moisture ingress. Four inches is the minimum thickness that provides sufficient bearing capacity, reduces the chance of cracking or settlement under heavy loads, and helps keep moisture from reaching the equipment. A thinner slab would be prone to damage and moisture problems, while a much thicker slab adds unnecessary cost without added safety benefit.

When a transformer vault floor is in direct contact with the earth, it must be a solid, thick concrete slab to safely bear the weight of the equipment, resist soil pressure, and limit moisture ingress. Four inches is the minimum thickness that provides sufficient bearing capacity, reduces the chance of cracking or settlement under heavy loads, and helps keep moisture from reaching the equipment. A thinner slab would be prone to damage and moisture problems, while a much thicker slab adds unnecessary cost without added safety benefit.