General question about fuse types - voltage

[Doug32 Member Find all posts View Profile Close Doug32]

I had a conversation with a couple of guys in my 4WD club about fuse voltages. We wondered if the voltage shown on fuses are irrelevant for low voltage applications. For example, I have some glass tube fuses that are 15amp capacity. One fuse is rated at 32 V and the other at 250V. Could I use either of these in a 12V circuit with each providing 15amp protection. Does the voltage rating matter? Cheers

[JohnLynn Senior Member Find all posts View Profile Close JohnLynn]

I would say yes you definitely can, if they are designed to blow above 15 amps then that is what they should do. I assume the voltage rating refers to the insulation resistance that the fuse body is made from, although if these are both glass and the same length it does seem odd that they have different voltage ratings. However if the working voltage is the same or less than the rated voltage they will be fine.
Hopefully someone will let us know who is more knowledgeable about this, I am only answering with a background in telecoms and being a smart arse.

[Doug32 Member Find all posts View Profile Close Doug32]

Thanks John for your response.

[Guest Close Guest]

The voltage rating on the fuse must be greater than the circuit voltage.

[Doug32 Member Find all posts View Profile Close Doug32]

OK! I was more concerned with watts passing through the fuse. A fuse marked 240V and 10 amps will have 2400 watts passing through it before it theoretically blows. Does this mean that the same fuse will still blow at 10amps with only 12 volts passing through it (120 watts). That is a big difference in power passing through the fuse.

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

A fuse has amps flowing through it not watts, the voltage refers to the interrupting ability of the fuse, ie it will safely fuse and arc at 32V, it could arc over if a 100V was applied for example. It will blow at the same current if 5V is applied or 32V.

[Doug32 Member Find all posts View Profile Close Doug32]

Thanks Leigh that's worth knowing.