601 Amp Fuses

[Grouch]

Section 240.6 lists 601 amp OCPD's as a standard size. Does anyone know how a rating of 601 came about?

Why not 401, or 501?

 

[infinity]

I'm guessing but I think it has to do with enabling you to get a "600" amp fuse (technically 601 amp) in an 800 amp fuse gap.

 

[jim dungar]

There is no Class L (800A) to Class R (600A) fuse reducer. The 601A fuse effectivelly allowed a 800A switch to be refused smaller. Very very rarely used in the real world.


In recent years, UL has changed its procedures for Class L fuses and so they are now available in ampacities 600A and smaller.

 

[Grouch]

Thanks guys!