Disconnect Fuse / CB

[Rson]

Sometimes a device will have a note like this “ Short-circuit rating achieved when used with respective fuse type and maximum fuse rating”

This is for an Eaton R9 type rotary disconnect switch. The 30A disconnect has a 100kA Short circuit rating with class J 30A fuses. Without it, you get the default rating for a switch which is 5 or 10 kA…

Ok - this makes the most sense so far. I hadn't been thinking about the SCCR of the disconnect itself - without the fuse.

 

[johnd_125]

the CB in the panel may not be necessary if there is a proper sized CB in the DB. But in my world customers would rarely pay any attention to, or provide for that.

I also typically have a few motors in a group installation to protect and I can size the CB appropriately for that.