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post #12 of Old 09-12-2011
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Originally Posted by Maine Sail View Post
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:


Last edited by btrayfors; 09-12-2011 at 11:55 PM.
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