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Circuit breakers vs Mega Fuse


krissvdh
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I'm hoping someone with a more reasoned mind will be able to assist me.

I'm just gathering up the last few bits to install a pair of aux fuse boxes (1 X 6 Feed & 1 X 12 Feed) and i'm undecided on the benefits and drawbacks of large 100A fuses over a similar rated circuit breaker.

Obviously the need to carry spare fuses is not a massive drawback but space is limited when it comes to replacing them. I'm specifically looking at Blue Sea marine circuit breakers which are said to be pretty durable with regards to water ingress and vibration.

Now the reason i'm undecided is the fact that I have not seen many folk use them when doing a similar job. Is there a reason behind this that I am missing? This load of wiring is going to be a proper job and i'd like to be happy with it and get it right first time.

Regards

Kris

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I personally prefer lots of smaller fuses over one or two big ones. Provides better "discrimination" [that is, you can spot the problem circuit quicker] and also avoids the issue of one-fuse-covering-multiple-things which plunges you into darkness silence and going-nowhere-fast when it blows.

Example: last time I designed a wiring-loom from first principles I had 4 separate 2.5-amp fuses for the sidelights on each corner, one for the number-plate lamp, one for the main instrument-pod illumination, and one for the switch illumination. Then another one for the trailer-socket. Four separate fuses for the four electric windows; four separate fuses for front/rear screenwipers and washers, separate fuses for front and rear interior lights..

Circuit-breakers seem overkill for such a situation: they get expensive very fast when you need lots of them! Only thing I can think of that might possibly need a 100-amp fuse or breaker is the glowplugs (which take about 60A on a TD5).

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A big fuse doesnt replace the requirements for smaller fuses . The smaller circuits should be protected by using a fuse rated for the calculated current in that circuit . The larger fuse is there to cover the largest calculated load on that supply .

Circuit breaker has the advantage that you can do an immediate reset , in case of some anomaly , but should only be reset once or twice , saves carrying a load of different rated fuses, and still requires sorting the problem if repeat trips. HTSH

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Thanks for your input.

It is just to protect the main cable from the battery through to the opposite seat box which is where the fuse box is located. The fuse box won't feed anything mission critical and will keep any and all accessories separate from the vehicle wiring loom.

It's only a short run but I'd rather like to follow a belt and braces approach.

Kris

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