A question about fuses

[gtmoore]

The fuse panel on our boat is getting a bit full with all the electrical goodies that I keep buying. I have a number of low current devices such as VHF Charger, Gas alarm, car radio etc that at the moment I am running from a single 5 amp fuse switch. The car radio has it's own inline fuse but would it be prudent to install inline fuses for all of these devices or provided I don't exceed the 5 amps load is it OK to rely on the fuse switch?

Thanks

 

[davel]

Nigel Caulder wrote a useful article in one of the mags (PBO I think) a few months ago. In it he reminded his audience that the fuse should be used to protect the cable as well as the device. In other words, if you have a low current rated cable linking your car radio to the 5 amp fuse, you have a potential fire hazard as the cable could burn out before the fuse does.

If your cable is rated above the rating of the fuse there should be no problem in running your devices in parallel other than the obvious point that if the fuse does go, you lose all your devices rather than just the one.

Dave L.

 

[gtmoore]

Excellent point! I'm normally careful to consider cable size when it comes to the load of equipment (such as a Bilge Pump I recently fitted) but in this case I didn't consider it in terms of the current carried with the fuse blowing! Certainly, the wire to the Handheld VHF charger is very thin so this should definitely have a separate smaller fuse I would imagine. It just gets a bit messy when you have fuses on top of fuses - plus the added inconvenience of having to remove a panel or something to get to it. I guess really I just need a bigger fuse/switch panel and a headache of a rewire!!

Thanks for the advice.

 

[bryantee]

have a look at http://www.boatownerscatalogue.com/ part no 950-001 or 950-002
they do a 6 fuse board with indicator lights which you can feed from the exsisting switch.not much bigger than a floppy disc. choice of blade or20x5 .hidden away it splits the power and safe guards the smaller demand units.20x5 is better because you can get .5 amp fuses.but the smallest blades ive seen are 3 amp.
good luck

 

[Chris_Stannard]

This is an srea of confusion. Normal fuses, such as your 5 amps, are meant to protect the wiring if there is a short somehwere in the circuit. They will blow before your wiring melts and starts a fire.

If you want to protect equipment you need to fit fast blow fuses, that will go before the equipment is damaged. Your VHF, for example, is likely to have an internal fuse of this nature. The wiring for current is often on the basis of keeping the resistance down, particularly on long runs with high demands. An anchor winch is a good example of this type of run.

Rather than just add more and more equipment to a fuse I would suggest you should consider going back to basics and taking a new power fuse off the main supply bus bar and choosing the wiring size and fuse for the load and the distance to be run. Any manual on boat electrics will quote the size of wire needed for various applications, the PBO one is very good and easy to follow.

Chris Stannard

 

[gtmoore]

Excellent Advice as usual!

Following your advice Chris I ordered the PBO book (turned up next day - well done Amazon!) and it really is excellent - in fact unknowingly I used a diagram from this book (in a PBO issue recently) to install some shorepower as it was so clear and easy to understand - thanks for the tip.

Bryan - thanks for the info on the panel although having read the aforementioned book I think the whole 12V electrics on the boat, though quite recently changed (not by me!) probably need a bit of a revamp.

Cheers

Gavin