ANL Fuses vs. Class T Fuses


not an electrician.
I need to replace a fuse I purchased, after OrioN kindly pointed out I had spec'ed the wrong size fuse. I'm hoping to educate myself on why I should choose one type over the other:

Class T Fuses:

  • higher "Amp interrupt Rating"
  • HUGE
  • $$$
ANL Fuses:

  • lower "Amp interrupt Rating"
  • smaller and easy to mount
  • more readily available
  • cheap
I'm speculating that for RV use, the high "Amp interrupt Rating" is not as relevant. But maybe their bigger size means less voltage drop? If there isn't a huge performance difference I would prefer to save the space and cash and go with an ANL fuse...

Thanks, I look forward to learning what is known. :popcorn:


2012 Sprinter 3500 Ext
If your Inverter manufacturer recommends using an ANL fuse, as you have previously posted, then I would just go with that.

- - Mike
2013 Airstream Interstate from 2012 Sprinter 3500 tall & long


Engineer In Residence
A fuses interrupt capacity is the amount of current that can be flowing through that fuse (at the time it blows) and still have the fuse safely and quickly blow.

From Wikipedia
Breaking capacity or interrupting rating is the current that a fuse, circuit breaker, or other electrical apparatus is able to interrupt without being destroyed or causing an electric arc with unacceptable duration.
Battery banks are a bit unique in that they can supply astonishingly high amounts of power if they are short circuited. Having a fuse that can safely and rapidly clear a fault at high currents is important. Because Class T fuses blow very quickly there is less chance of damage to equipment.

If a fuse takes too long to clear a fault, the wiring downstream (usually junctions or terminals) can catch fire.

Also if a fuses interupt capacity is exceeded, it can cause an arc, or in some cases they will shatter/explode. None of these are desirable.

From Blue Seas circuit protection catalog

ANL Fuses vs. Class T Fuses
What is the difference between an ANL and a Class T fuse?
These two fuses are the most common high amperage fuses used in
marine applications and there are significant differences between the two:

ANL Fuse Advantages:
  • Lower cost than Class T fuses
  • Available in a wider amperage range than Class T Fuses
  • Single mounting hole dimension allows all ANL Fuses to be used with the same fuse block
  • Fusible link window gives visual indication of fuse being blown
  • Ignition protected—safe for installation aboard gasoline powered boats

Class T Fuse Advantages:
  • The only UL 248-15 listed fuse commonly available in the marine industry
  • Very fast response to short circuits protects high-amp electronic equipment such as inverters
  • 20,000 Amp Interrupting Capacity


2008 2500 170" EXT
Why does an inverter need protection from a 12V short between battery and inverter?
Larger inverters draw larger currents. Larger currents have the potential (see what I did here) to arc during a short and this condition exposes the inverter to possible damage. Faster blowing Class T fuses are recommended to mitigate the risk.


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