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PC-8R Installation Guide Version 1.0 Rev 1.1
Fuse Selec on:
The PC
-
8R uses mini blade fuses. The fuses come with a number stamped on top of the fuse in
white i.e. the fuse value.
Do not use cheap reproduc on fuses ( usually no white value stamp on the top and not made
from a nylon plas c ).
The number stamped on each fuse is it’s con nuous current ra ng at 25
˚C
,
however, running a 10A fuse at 10A causes a heat to be generated at the fuse element. With a
10A ATM fuse in three different ( brand name ) manufacturer fuse holders, and a current of 10A,
we measured temperatures of up to 90
˚C
. When operated at 75% of the rated current, this tem-
perature dropped to a much more acceptable 49
˚C
. Li lefuse
( patent holders )
recommend dera ng
of the fuse value by 25% to avoid heat/reliability issues. A quote from Li elfuse_fuseology.pdf
“
For example, a fuse with a current ra ng of 10A is not usually recommended for opera on at
more than 7.5A in a 25˚C ambient”.
In short, if you want to fuse 15A circuit, use a fuse that is at least 15A/0.75= 20A
Example 2: Switched output 3 is to protect a naviga on systems that requires 4.8A con nuously.
To select the fuse we divide 4.8/0.75= 6.4A. Since there are no 6.4A fuses we use the next higher
value, which is 7.5A ( standard value ).
Example 3: Switched output 6 is to protect a set of LEDs that draw 10A con nuous. Dividing
10A/0.75= 13.3A. Since 13.3A is not a standard value we would use a 15A fuse ( the next higher
value ).
Mini Blade fuses are sold in the following values: 2, 3, 4, 5, 7.5, 10, 15, 25, 30
Figure 7: Mini Blade Fuse Standard Values ( Li leFuse )
