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Friday, June 9, 2017

Question:

Good morning, I enjoy starting my day with the CQD. We have a discussion going on here at the office with differing opinions.  It is my understanding “fuse reducers” that will allow for example, a 40A fuse to be installed in a 30A Fused Disconnect Switch of the same voltage are illegal; however, I am unable to find the code section to support my position.

Your help in this matter is greatly appreciated.

Larry N. James

A

Answer:

Hey Larry thanks for your question, we are glad to help you start the day. Cartridge fuseholders must be designed so that it is difficult to put a fuse of a higher class into them as stated in 240.60(B).  So no a 40 ampere fuse should not fit in a 30 ampere fuse holder - that would actually be a fuse increaser. There are fuse holders available that allow a 30 ampere fuse to be installed in a 60 ampere fuseholder. The NEC does not prohibit their use.

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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.

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