A transformer with a ___ enclosure is permitted to be installed inside a building.

A transformer with a sealed enclosure is permitted to be installed inside a building because sealed enclosures provide a high level of protection against dust, moisture, and other contaminants that could adversely affect the operation of the transformer. This type of enclosure minimizes the risk of contaminants entering the transformer, which can lead to overheating, reduced efficiency, and potential failure.

Sealed transformers are designed to operate effectively in environments where exposure to external elements is a concern, ensuring safety and longevity. Other types of enclosures, such as ventilated or waterproof, may not provide the same level of protection specifically needed for indoor installations. A ventilated enclosure, while allowing for air circulation, may expose the internal components to particles and moisture that could compromise the equipment. Similarly, waterproof enclosures are typically used in outdoor settings to protect against water intrusion, making them less applicable for typical indoor environments.

Therefore, the use of a sealed enclosure is the most appropriate choice for a transformer installed within a building, ensuring it operates safely and efficiently in a controlled environment.