North Australian FISH FINDER TM forums

Loki wrote:The only way a fuse will protect an appliance from over current is if you supply an overvoltage. I=V/R IE Voltage goes up, so current goes up. Can happen but rare.
If you use 50 amp on a 2.5mm2 cable it will fry the cable if if the appliance can handle it.
If you have a radio that draws 1.5 amps of current, you do not put in a 1.5 amp fuse. All you get is nuisance trips. You put in a 5 amp, or 10 amp fuse. Depending on the cable. If the cable is 1mm2 I would not be using a 10 Amp fuse.

This doesnt really make sense to me because when your voltage goes up your current draw will decrease.
All the fuse is suppose to do is protect the wiring not the appliance different gauge cable obviously has different current handling capability and you shouldnt over fuse what the circuit is designed for.
There is very rarely ever any thing in your average tinny that needs relays for all the appliances in the above i would not reccomend any no offence but this is what happens when 240volt sparkys trys to do auto electrics.

cheers

Anyway, as i said, i had bugger all knowledge about wiring etc.

I built a motor home a few years ago and got most of my info from a 'guru' in the field . he has written many books and used to be on boards for different safety organisations
(yes from a book but most tafe stuff is theory from books)


His recommendation was for the bigish circuit breaker to protect the wire and the fuse right next to the appliance to protect it (fues suitable to the power needs of the appliance)

this wont work on a boat though because the limited access to appliances.
it made sense to me.

on a boat, you need to have the switches in the one spot so you can turn things on/off easily. (same as a car, but different from a house or a motor home)