Fuse Ratings Explained

Wednesday, 16 January 2013  |  AdrianR

Typical style capped glass fuse Most fuses used in an automotive and domestic application now have (and should have) standardisation for fuse identification, modern fuses now in production standardise the displayed rating for continuous use. In some cases and in particular glass fuses, the rating on the fuse cap can still be marked with a blow rating by manufacturers, which often leads to confusion even within the electrical trade.

Because a fuse is there to protect the circuit components and cables from current overloading, for safety reasons and component cost, it's important to note that: 

Continuous rating for fuses means they should blow at the amperage when the circuit is always on or plugged in.
Blow rating for fuses means that the circuit is intermittent (on-off) and the fuse heats up before blowing.

Before replacing old glass fuses, it's always recommended that when possible, you check your equipment manual or supplier's website documentation before replacing fuses to determine exactly which fuse rating you require.

This blog post was created: 16th January 2013 and closed for comment 25th July 2015.

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