What clearances are required around transformers when they are installed?

All dry-type transformers depend upon the circulation of air for cooling; therefore, it is important that the flow of air around a transformer not be impeded. Many Eaton transformers require a minimum clearance of 6 inches from panels with ventilation openings. However, small kVA DOE 2016 efficient ventilated transformers are UL approved to be installed with just 2 inches clearance, while large kVA transformers require 12 inches or more clearance. In compliance with NEC 450.9, Eaton’s ventilated transformers have a note on their nameplates identifying the minimum required clearance from the ventilation openings and walls or other obstructions. This clearance only addresses the ventilation needs of the transformer. There may be additional local codes and standards that affect installation clearances.Transformers should not be mounted in such a manner that one unit will contribute to the additional heating of another unit, beyond allowable temperature limits, for example, where two units are mounted on a wall one above the other