Dry-type transformers installed indoors rated over 35,000 V must be installed in a vault.

Dry-type transformers installed indoors rated over 35,000 V must be installed in a vault.

• A. Only if located on the top floor
• B. Only if kVA > 50
• C. True
• D. False

Answer: (C)

High-voltage indoor dry-type transformers create significant fire and arc-flash risks. When the voltage rating exceeds 35,000 V, the installation must be in a fire-resistive vault to contain any fire, limit smoke and heat, and provide controlled access for maintenance and emergency response. The vault acts as a protective barrier between the transformer and occupied spaces or other equipment, improving safety for personnel. Because of these safety concerns, the statement is true. The requirement isn’t based on top-floor location or on kVA; those factors aren’t what trigger the vault installation.

High-voltage indoor dry-type transformers create significant fire and arc-flash risks. When the voltage rating exceeds 35,000 V, the installation must be in a fire-resistive vault to contain any fire, limit smoke and heat, and provide controlled access for maintenance and emergency response. The vault acts as a protective barrier between the transformer and occupied spaces or other equipment, improving safety for personnel. Because of these safety concerns, the statement is true. The requirement isn’t based on top-floor location or on kVA; those factors aren’t what trigger the vault installation.