Originally Posted by Maine Sail
80%..? Jon A. at ABYC says, and we've specifically discussed this, the ampacity chart already accommodates for ANL, Class T etc. and MRBF is really quite similar to an ANL.
Not really. ANL fuses are unlike any other CPDs, in that they blow at a much higher than nominal rating, whereas most other fuses and breakers blow at about 130% of their rating.
ANL blowpoints can exceed their ratings by 140% to as much as 266%. A 100A ANL won't blow until current reaches 175A or more for 500 seconds -- over 8 minutes!
The ampacity tables cannot take the differences between CPDs into account; you must do that yourself, or find a table in which the specific CPD is referenced.
I believe that MRBFs are like most other fuses found in the marine environment -- relatively fast blowing at 130% of their nominal rating. ANLs are very different.
Here are the curves for the MRBFs: http://bluesea.com/productline/specs/379#td