[JoeBoy]

Hey people I'm building out an electrical box, and need a very basic but essential question answered.

Essentially just an enclosure with a 12x fuse holder, and 2x busbars for negative returns and a few relays.

I want to set the thing up for future expansion, so when I want to install something in future (e.g a light bar or camping lights etc..), I don't have to open the box and do a bunch of crimping/ soldering connecting etc...

So my plan is to have everything pre-wired, so when I do want to connect something later on - all I will need is throw a fuse in and have the cabling already run outside the box to a length of say 20cm and connect there.

So my question is this, if I'm pre-wiring the positive and negative wires from fuse holder to a length of 20 cm, what would be a safe wire gauge to use?

From my understanding 18 gauge can safely run 40 amps at 30cm so does that mean I could use 18 gauge for 30cm out of the box, and then connect a larger gauge to it for the main run to an acc?

 

[CroPatrol]

According to the calculation and experience, you can put a 2.5mm2 wire to a length of 5 M. If in doubt, then put a fuse 16A and put 5m of wire, and make a short circuit. The fuse must blow in 1 second.

 

[Overboard]

So my plan is to have everything pre-wired, so when I do want to connect something later on - all I will need is throw a fuse in and have the cabling already run outside the box to a length of say 20cm and connect there.

This sounds like an absolute mess to me. Get the box with some fuses ready but don't connect the unused cables you suggested. I suggest something like the pic where there is good space for the negatives and a terminal beside each fuse that is easy to connect to. The Narva one in the pic has the advantage the cover locks on rather than just clips on. All terminals are shrouded with the cover on which is not the case for all fuse boxes.

 

[Neardood1]

Crimp on style blade terminals are your friends. Instead of running 20cm of wire from a fuse gang, buy one with blade terminals and just run the wire and crimp onto an unused fuse terminal when you want to expand. that way it saves having to do a time consuming solder joint, and you can easily swap terminals without tools which is helpful for fault finding.

 

[GQshayne]

Yep, I am with the other guys - sounds like a bit of a mess. I use fuse blocks with negative bus bars like the Narva one. Jaycar units are similar and much better priced. Then with any new component that may be installed, it simply needs to be wired to the fuse block. The fuse block needs to be easily accessed at any time, so wiring back to it should be a simple exercise.