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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.