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NECA Revises 409-2015 Standard for Installing and Maintaining Dry-Type Transformers

Sep 11, 2015

The National Electrical Contractors Association (NECA) releases revised standard for installing and maintaining dry-type transformers, NECA 409-2015Dry-type transformers were used in the U.S.'s first municipal electrification plans, where the coils fully exposed to the surrounding air, to which all internal heat loss was freely dissipated.

NECA409-15Cover_WEBThese days, dry-type transformers are very common in commercial and industrial power distribution systems. This National Electrical Installation Standard (NEIS) describes installation and maintenance procedures for single-phase and three-phase distribution and power transformers and associated accessories rated at 600 volts ac or less, and 0.25 KVA or more, of the following types: 

  • Ventilated, indoor and outdoor, self-cooled or forced air cooled.
  • Non-ventilated, indoor and outdoor, self-cooled or forced air cooled. 

NECA 409-2015 Standard for Installing and Maintaining Dry-Type Transformers is the latest revised publication in the National Electrical Installation Standardsseries published by NECA and has been carefully updated to reflect the latest provisions and requirements in the NEC. NECA 409 includes periodic routine maintenance and troubleshooting procedures for dry-type transformers, and special procedures used after adverse operating conditions such as short-circuit or ground fault events, or immersion in water.

This edition of NECA 409 has been meticulously updated to include essential NEC requirements and continues to deliver the goods relative to quality and performance criteria installers and owners are seeking. Key value provisions of this standard not found in the NEC are testing methods, commissioning processes, and maintenance procedures for busways.   

“NECA’s National Electrical Installation Standards (NEIS®) library has grown over the years, and as new technologies emerge, the NEIS® evolve and keep pace,” stated Michael Johnston, NECA’s Executive Director of Standards and Safety. Johnston also emphasized that “the standards are constantly providing significant value to those in the electrical designing and engineering communities. The NEIS help professionals in developing design specifications in that they reduce and often eliminate specification writing time.”


NECA 409-2015, Standard for Installing and Maintaining Dry-Type Transformers Revised is $20 for NECA members and $40 for non-members. 

Visit the NECA Store at necastore.com to purchase. Index: #NECA 409-2015

Purchase NECA 409-2015 Today!


National Electrical Installation Standards™ (NEIS) are the only quality and performance standards for electrical construction. They establish requirements for installing electrical products and systems that go beyond the minimum safety rules of the National Electrical Code (NFPA 70) and are used primarily by electrical contractors, consulting engineers, facility managers and professionals who design and specify for electrical construction projects. With their installation detail, illustrations and thorough explanations, NEIS are also a valuable training tool for electrical construction industry. Individual NEIS are available in hard copy and as PDF downloads from NECA’s online store, NECAStore.com.



The National Electrical Contractors Association (NECA) is the voice of the $130 billion electrical construction industry that brings power, light, and communication technology to buildings and communities across the U.S. NECA contractors help customers achieve their goals for energy conservation, efficiency and renewable power. NECA’s national office and 119 local chapters advance the industry through advocacy, education, research and standards development. 

For more information, visit necanet.org.