In line fuses

[on-one]

My boat's about 25 years old and the wiring is a bit of a mess as people have added to it over the years. I've recently replaced the sounder and gps and am about to add a vhf and have tidied up the wiring for them but now want to sort the rest of the wiring. So far I've left the in line fuses suplied with the electronics in the circuit but have just bought a new fuse block so each item will be on its own circuit with a fuse.

What's "best practice" should I leave the in line fuses in as they're more protection for the circuits or does this create confusion as I'll have to check two fuses rather than 1 if something blows?

[deadbeatloser]

i have wired all my stuff up with the set up you quote (blok n fuse) i dont think it will cause any trouble or ever will, like wearing two condoms a
regards dbl

[oldboot]

There is realy no hard and fast RULE, but there are several philosophies.

The engineered philosophy genelay is that fuses are there to protect WIRING down stream from the fuse. so that a panel fuse is to protect the wiring following it....... inline fuses on equipment are then for protecting the equipment.
If you have several pieces of equipment fed off one fused circuit then thats the way it should be.........bear in mind that much of the modern electronics will have it own power switches too, so there is little necessity for having a seperate switch for that item.


There is also a "fuse and switch for everything" philisophy.

Now at a time where the only electronics on a boat was the marine radio..... which should have been diect wired (common opinion)...all the remaining items wer lights and motors like bilge pumps....so the fused switch panel was a very logical thing to do.

I know some that will argue that if all the fuses are in the fuse panel there is only one place to go, and you dont need to chase the inline fuse.

You can get into all sorts of meditation over this sort of stuff.

I will raise on significant engineering philosophical point.

Why will a fuse blow and what caused that failure and what are the implications.

Fuses fail for three reasons,
A fuse blows due to significant wiring or equipment failure.
A fuse blows because too much load has been applied
A fuse fails due to mechanical failure.

If there is a significant failure within a piece of equipment like a radio or sounder and the correct inline fuse blows, the likly hood of that item functioning after replacement of the fuse is low. If the wiring is adequate and the fuse protecting that wiring was correctly sized.....it should have remained in tact ( should).

So we are left with wiring failures, aside from accidents most wiring failures are design or maintence related....so if you do nice work and look after it it should never be a problem.

If a fuse blows because the circuit has been overloaded, in a boat there is a design problem......do nice work it should never be a problem

Fuses do fail from mechanical falure, I have seen cheap fuses simply pull apart, vibration can be a problem as can corrosion. I have seen fuses and holders so badly corroded that the fuse and the holder were useless.
Always buy good quality fuses and holders, and look after them.


Personlay I would leave the in line fuses on the electronics..... there may be waranty issues there too.
Personaly I cant see a good reason for having seperate circuits or switches for individulal electronic items.... except radio.........I can see an argument for wiring a marine radio direct to battery..... I can see arguments agains too.

Have you included a main battery isolator and have you included a heavy main fusable link or circuit breaker.

I can also see an argument for using circuit breakers instead of fuses on the main panel too.

I know I rave on but I hope I've given you some stuff to think about.


Is the wiring heavy enough? I always ask....... especilay if it is my work.

cheers

[Kleyny]

i use circuit breakers for 90% of my electronic either car or boat.
You can buy ones that reset after they cool back down. (good for when its a booboo on your behalf)

neil

[on-one]

"like wearing two condoms " - Interesting choice of words dbl, the main reason I'm working on the boat rather than using it is an unplanned baby

Thanks all everyone for your replies, oldboot the main reason for going for a fuse and switch for everything is that I want to rewire the boat in stages rather than all in one go, once I've got everything sorted, labelled, and all of the redundant stuff off the boat I might try to simplify things a little thanks for mentioning the main circuit breaker no idea if there's one on the boat or not. Have seen a couple on a bulkhead but I'm almost sure they're for the ac power which I don't want to go near

[oldboot]

Your main battery isolator and the main feed circuit protection device should be right next to the battery......the idea being it protects the feed from the battery otherwise you have a heavy cable running up the boat with no protection and a battery capable of delivering 100's of amps fault current.
The battery isolator allows you to shut down the whole boat without removing the battery... the only thing left connected is the cranking circuit.

The concept of the two condomsis probably.. alright
More accurately...you are being more specific about your protection.

If the boat is 25 yeras old........it's problay due for a good look at anyway.

I would start with a battery isolator, main circuit breaker and a positive & negative distribution block.......that gives you a sound place to start and a place to connect and disconnect as you work and the means to isolate the system whilst making connections.
you would work out from there to the switch & fuse panel and keep going down the individual circuits.

cheers

[littlejim]

Mine had inline fuses on all the wires tucked up behind the dash, with different amp ratings.
I got rid of them all. Ran the wires to a bit of perspex with screw top fuse holders mounted in it and put some Dymo under each fuse holder with the amp rating on it. Above is Dymo with what the fuse is for. The spares are elsewhere, but I don't have to memorise which value fuse is for what. Should help as the Altzheimers cuts in.
One fuse per circuit will do me. Can't see how two fuses can help in any way other than having to replace both when the circuit overloads.

[oldboot]

I certainly dont recon that inline fuses for everything is a good idea.

Apart from inlines that come as fitted with electronics I dont think they are a good idea.

On other idea is to wire all the individual circuits on the boat in the same guage wire....... then there is only 1 fuse rating require on the fuse panel...you can get away with this on most small boats.


cheers

[Feral]

I have fuse blocks at each battery bank, dont run a lot of electrics, so everything gets its own fuse in the fuse block, but if you were running more than one thing off a fuse in the block, I'd recommend a smaller fuse between the fuse block and the gear, so the individual fuse wull blow.

Otherwise you have to fault find to find out which bit of gear blew the main fuse, which will always occur on a black night in pooring rain 200 yards from a lee shore!

PS My electric motors are not fused. just straight power through Anderson plugs from each battery bank. Probably should be fused, maybe one day.

[Fatenhappy]

Hey on-one ....

From an electronics point of view, the reason for the fuse so close to the power source is in actual fact 2 fold .... 1. to protect all the wiring and 2. to protect the unit being fused itself.

As far as each unit being fused individually it is not uncommon for manufacturers to individually fuse an item within itself, so there is really no reason why you shouldn't/can't leave the in line fuses where they are providiing that is right up and close to the unit.

Having said that, if the in line fuses are at the source, take them out of circuit for neatness and by doing that there's one less thing that can go wrong (... open circuit/blow)

Cheers
Greg

[on-one]

Thanks Greg. There'll only be about 6 inches of wire between the new fuse block and the inline fuses so it seems a bit unnecessary to have two fuses so close together but since someone from furuno designed it with an inline fuse I'm reluctant to take them out