section 240.4(B) permits you to use the next higher standard rated fuse or circuit breaker when the conductor rating doesn't match the standard sizes (with certain restrictions). However, 240.4(C) limits this to 800A or less. I have heard that the 800A limit was not always there. My question is when did the 800A limit start? My oldest Code book is 1981 and it is still there in 240-3 exc. 1.