Odd-sized Fuses

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jeff48356

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Livonia, Michigan
I've always wondered, what are odd-sized fuses used for? The ones in question are 6.25A, 10A, and 25A. What size of wire would you use each fuse with? I've seen these fuses around for decades, but never seen any circuit breakers in those sizes.
 
Jeff, some of the "odd" sizes fit motor calculations to a "t" so I have assumed they were manufactured primarily for motor protection, but I do not know that for sure. #14 remains the normal "minimum size conductor" per 310.5
 
LarryFine said:
How about 601a? :wink:
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What about it? I'm aware of that particular fuse, but I have never used one that size. I don't even remember what it is used for.

Now the 6.25 is very common in motor circuits.
 
dlhoule said:
What about it? I'm aware of that particular fuse, but I have never used one that size. I don't even remember what it is used for.
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One idea.
Because there are no fuse reducers available for 800A and larger fuse holders, a 601A fuse allows relatively easy up-size or down-size between 800 and 600A circuits without replacing the switch. Although I notice that fuse manufacturers are no offering Class L fuses that are <601A.
 
I have installed 601's for reasons Jim mention, down sizing for a store remodel that had an existing 800 amp FSS.

I also wear 501's..Levis that is
 
A 601 is a Class L (KRP-CL-600) fuse made to fit a Class L disco or switch, rather than a 600 amp RK5 or RK1. Class L fuses can also come 400 & 500 amp. The advantage is the Bolt-in feature.
The 6 1/4 was popular for a motor with a FLA of 3 to 4.8amps, like a 480/277 2-3 hp motor, with a SF of 1.15.
Just my $.02
 
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