National Electrical Installation Standards

Standards as High as Your Own

?
Friday, October 6, 2017

Question:

Re: CQD answer published Friday, September 29, 2017 -Dry Location

Regarding the use of a dry transformer inside a weatherproof in-use cover, I do not find a section prohibiting this. Section 300.38 defines the interior of the conduit as wet, and 300.50(B) defines an underground box as also wet, however, I do not know of a section defining the interior of an exterior above-grade box as wet, much less the space inside the weatherproof in-use cover.

The whole purpose of the special cover is to prohibit the entry of water into the space where the plug is inserted.

Scott Cline

A

Answer:

Hey Scott thanks for your comment it's good to hear from you. You are correct there is not a specific rule that prohibits plug in transformers from being installed outdoors under a weatherproof cover. Section 300.38 is in Part II of Article 300 so 300.9 would be more likely applicable to the voltage of a plug in transformer but those sections are for above grade raceways in wet locations.  The plug in transformer would not be inside a box it would be inside a weatherproof cover. Notice the difference between the definitions of "weatherproof" and "water tight" in article 100 - weatherproof does not include preventing the entrance of water. Also as stated in the definition of "outlet box hood" in 406.2 "it reduces the risk of water coming in contact with electrical components".

The original question stated that the plug in transformer was identified for dry location use only and the space inside the weatherproof cover located outdoors could be considered a damp location. As previously mentioned it is somewhat of a judgment call and suggested contacting the manufacturer.

ABOUT CQD: NECA’s Code Question of the Day (CQD) is a leading National Electrical Code® forum for NECA and the industry. The CQD generates a lively dialogue and relative practical and Code-based responses to an ever-increasing and interactive audience.

IMPORTANT NOTICE: All answers are based on the latest edition of the National Electrical Code®, unless the question requests a response based on a specific edition. This correspondence is not a formal interpretation of the NEC®. Any responses expressed to the questions are opinions and do not necessarily represent the official position of NECA, NFPA, or any technical committee. In addition, this correspondence is neither intended, nor should it be relied upon, to provide professional consultation or services.

ABOUT CHARLIE: Charles M. Trout, better known as Charlie, was a nationally known NEC® expert and author. He served on several NEC® technical committees and is past chairman of CMP-12. In 2006 Charlie was awarded the prestigious Coggeshall Award for outstanding contributions to the electrical contracting industry, codes and standards development, and technical training. Charlie was also a member of NECA’s Academy of Electrical Contracting. Charlie’s experienced team of industry experts keep the CQD dialogue and discussions active and informative in the spirit of the man himself, as he wanted.

NECA STANDARDS: NECA publishes the National Electrical Installation Standards™ (NEIS™), a series of ANSI-approved performance and quality standards for electrical construction. Visit NECA-NEIS.org for more information. NEISÔ can be purchased in three formats: as paper books, on CD, or as electronic downloads.

NECA SAFETY PRODUCTS: NECA publishes valuable electrical safety books and CDs for the industry. Visit necanet.org/store to view or purchase NECA safety products.

 CONTACT US: To submit a Code question, subscribe, or unsubscribe from this list, please e-mail: codequestion@necanet.org.