Transformers with ventilating openings must be installed so that the openings are not blocked by walls or obstructions. The required clearance shall be:

Transformers with ventilating openings must be installed so that the openings are not blocked by walls or obstructions. The required clearance shall be:

• A. As given in the job specifications
• B. Clearly marked on the transformer
• C. As listed in NEC Article 450
• D. Maintained on the top, bottom, and all sides

Answer: (B)

Ventilation clearances are determined by the equipment itself. The transformer is designed to breathe through its openings, and the exact space needed around those openings is specified by the manufacturer and clearly marked on the unit. That marking tells you the specific clearance to maintain so air can circulate and the transformer won’t overheat. This is why the best choice is the clearance that is clearly marked on the transformer. It ensures you follow the unit’s intended cooling requirements exactly. General job specs or the NEC might outline broad cooling principles, but they don’t provide a universal distance for every transformer. A blanket rule like maintaining space on all sides isn’t guaranteed for every model, and relying on a generic citation wouldn’t ensure proper cooling for a specific unit.

Ventilation clearances are determined by the equipment itself. The transformer is designed to breathe through its openings, and the exact space needed around those openings is specified by the manufacturer and clearly marked on the unit. That marking tells you the specific clearance to maintain so air can circulate and the transformer won’t overheat.

This is why the best choice is the clearance that is clearly marked on the transformer. It ensures you follow the unit’s intended cooling requirements exactly. General job specs or the NEC might outline broad cooling principles, but they don’t provide a universal distance for every transformer. A blanket rule like maintaining space on all sides isn’t guaranteed for every model, and relying on a generic citation wouldn’t ensure proper cooling for a specific unit.