National Electrical Installation Standards

Standards as High as Your Own
 
Menu

NECA Online Help Desk
Please leave a message
Submit your Code Question | Subscribe to CQD | Un-Subscribe To CQD | Print | Share This | RSS
?
Thursday, April 4, 2019

Question:

Charlie, Please refer to the table. This breaker has AIC ratings for several voltages. We are trying to apply this breaker to a 480 volt high resistance grounded system. This breaker table shows a UL 489 AIC rating at a nominal voltage of 480 volt. So this looks like it can be applied in my system. What I am concerned about is the 600/347 rating listed in the table. Since this is a slash rated breaker and the lower value is less than 480 volt I am not sure this breaker can be applied in the 480 volt HRG system and if used could be a violation of 240.85 and a possible safety hazard. Is this slash rated breaker be used on a 480 volt HRG system?

Thank you.

Jeff
A

Answer:

Hey Jeff thanks for your question. If the circuit breaker has a slash rating that means that it can only be used in a solidly grounded system, not a high impedance system, as stated in 240.85. The voltage to ground cannot exceed the lower voltage rating.

ABOUT CQD: The Code Question of the Day (CQD) is NECA and ELECTRICAL CONTRACTOR Magazine’s flagship National Electrical Code (NEC®) public forum for the industry, sponsored by EATON. The daily distribution of Q&A generates a lively dialogue and shares relative Code-based practical responses.

SUBMIT YOUR CODE QUESTION: Click here to submit a question to for inclusion in an upcoming edition of the Code Question of the Day, or email codequestion@necanet.org. 

CHARLIE TROUT: 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. Even though Charlie passed away in October of 2015, his work continues in spirit. NECA continues to maintain this question forum for its many subscribers in memory and recognition of all his significant contributions to making the NEC what it is today.

NECA STANDARDS: NECA publishes the National Electrical Installation Standards™ (NEIS™), a series of ANSI-approved performance and quality standards for electrical construction. NEIS can be purchased in the NECA Store in three formats: a printed or  PDF download of a standard or, as an  annual subscription service.

NECA SAFETY PRODUCTS & PUBLICATIONS: NECA produces electrical safety publications and products for the industry including jobsite safety guides, handbooks and resource kits. View a full listing of available resources and products »

IMPORTANT NOTICE: Unless the question requests a response based on a specific edition, all answers are based on the latest edition of NFPA 70® National Electrical Code®.

This correspondence is not a formal interpretation of the NEC® and any responses expressed to the questions are opinions and do not necessarily represent the official position of NECA, NFPA, the NEC Correlating Committee any Code-making panel or other electrical technical committee. In addition, this correspondence is neither intended, nor should it be relied upon, to provide professional consultation or services. 

UPDATE YOUR SUBSCRIPTION PREFERENCES: Subscribe or Unsubscribe from this list.

Submit your Code Question | Subscribe to CQD | Un-Subscribe To CQD | Print | Share This | RSS

© 1999 – 2014 National Electrical Installation Standards. All rights reserved.
Brought to you by NECA. NECA is the voice of the electrical contracting industry NATIONAL ELECTRICAL INSTALLATION STANDARDS, NEIS and the NEIS logo are registered trademarks of the National Electrical Contractors Association.

Created by Matrix Group International, Inc.

Follow Us on: