240.6 standard ratings why 600 and 601 amperes?

[tom baker]

Why does section 240.6 standard ampere ratings, list ...500, 600, 700,... and then additional ratings for 1,3,6,10 and 601. Whats the difference between a 600 and 601? is it the size?

 

[radiopet]

I believe Tom that the 601 has a setup that would allow its design to be used in lets say an 800A piece of equipment. Allowing you to meet the requirements of the 600A by taking an 800A rated equipment and fusing it at 600A or with a 601 rated fuse.

This would be prefered as well if someone was thinking of expansion at a later date and wanted to install an 800A piece of gear......but only wanted to fuse it at 600.

Again.....I may stand corrected but that is my take on it. Again the difference is the type of fuse and if it can fit in a piece of equipment larger than 600A.

 

[LarryFine]

Whats the difference between a 600 and 601? is it the size?

Yep. The 601 is a convenient way of fusing at 600a with a larger-size switch, etc.


Added: See? :grin:

 

[radiopet]

Search Feature : http://forums.mikeholt.com/showthread.php?t=83166

 

[bphgravity]

It also allows for an additional 1-amp load in case you need it...

 

[jim dungar]

Back in the old days, UL had a rule about mixing ampere ratings in fuse 'barrel' sizes. For example if you want to put a 400A fuse into a 600A switch you need to use a fuse reducer. So UL would(?) not list a 600A fuse in a 800A Class body size. To get around this the fuse industry created a 601A fuse. Recently, maybe 10 years, fuse manufacturers started to make Class L fuses all the way down to 400A.