Fuse Ratings

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bcorbin

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Asking a dumb question here....

I know there are 100%-rated circuit breakers, but is there the equivalent type of fuse? Or even a type of fuse that is not the hard and fast 80% continuous load?

I've just never seen one, and was wondering.
 
no,
CLass RK-5 & RK-1 fuses are sized depending upon application from 115% (lighting) to 175%-225% (motors) of the FLA & Service Factor. Class J your should start at 150% of FLA and work up from there. Class T generally for lighting only 115%-125%.
Just my $.02
 
bcorbin said:
Asking a dumb question here....

I know there are 100%-rated circuit breakers, but is there the equivalent type of fuse? Or even a type of fuse that is not the hard and fast 80% continuous load?

I've just never seen one, and was wondering.
Click to expand...
Yes, kind of.

All fuses and all circuit breakers are rated at 100% when installed in "open air". As soon as the fuse or breaker is installed in an enclosure it becomes an 80% rated device due to the build up of heat in the enclosure.To be used at 100% the enclosed fuse or breaker must be adequately ventilated. UL has test procedures for 100% rated fuses and breakers, but economics usually prevent them from being employed below the 1200A case/frame sizes.
 
I found this after much searching.

http://us.ferrazshawmut.com/oem/media/pdf/A4BY.pdf

So what you're telling me is, this fuse that they claim is 100% rated is no different than the other fuses? If I put this fuse in an enclosure, bam...80% rated? :confused:

*EDIT*

Never mind. I just got off the phone with a fuse manufacturer, and they finally explained it in a way I could get through my thick head. When Wil Smith says "You are the dumbest smart person I've ever met," I think he's talking to me.
 
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