The definitions

[Tom749 0]

What are the main differences of the Amps as attachment? (1) 30Amps (Main Disconnect) (2) 17.5A (FU) (3) SCCR-200kA Thanks for your reply in advance. amps.bmp Edited 10 Jan 2012 by Tom749

[drforsythe 15]

1) This is the rating of the disconnect. You can connect loads up to and including 30 amps to this device. When fusing, the disconnect, fuses must not exceed this value. 2) This is the rating of the fuses installed for this particular circuit. Main conductors coming from this fuse block must be sized to handle the rating of the fuses. 3) SCCR - Short circuit current rating. Per 2008 NEC Article 100: "Short-Circuit Current Rating. The prospective symmetrical fault current at a nominal voltage to which an apparatus or system is able to be connected without sustaining damage exceeding defined acceptance criteria." This is basically the amount of current a device can safely withstand during a short circuit (while the circuit protection is heating up, but before it trips or a fuse blows). The SCCR rating is used to design circuits that are safe to workers exposed to the live circuitry. It is used in arc flash calculations and required in the U.S. where the NEC (National Electrical Code) 2008 has been adopted. This is a simple overview. Hopefully it is helpful.