Master Electrician Practice Exam

What is the largest size transformer, in kVA, that can be installed in a room that is not constructed in a fire-resistant manner?

1. 75 KVA

2. 100 KVA

3. 112.5 KVA

4. 150 KVA

The correct answer is: 112.5 KVA

The correct choice reflects the National Electrical Code (NEC) requirements that limit the size of transformers installed in locations that are not constructed with fire-resistant features. Specifically, the NEC states that transformers of a certain size and rating can only be installed in non-fire-resistant spaces if they do not exceed a specific kVA rating. The limit is set to ensure safety and compliance with fire protection measures in buildings. For transformers, the maximum size typically allowed in these spaces is 112.5 kVA. This guideline helps minimize potential fire hazards that could arise from larger transformers, which may generate more heat and pose a greater risk in a non-fire-resistant environment. As the size of the transformer increases, so does the risk, necessitating more stringent fire protection regulations. By adhering to this kVA limit, the installation remains compliant with safety codes and minimizes risks associated with fire due to electrical equipment. Thus, 112.5 kVA stands as the largest permissible size for a transformer in a room lacking adequate fire resistance.