need some assurance.. ELECTRICAL question

[generalleexj]

ok well ive been doing alot of research over the past couple weeks and just got done building/ wiring my accessory fuse box
i put it in the rear cargo area in the odd shaped compartment in the right rear ( all XJ owners know what im talking about) anyway, i have a sound system and everything so heres what i got

i had 1 4 Gauge wire running to the rear to a distribution block for all of my amps sub and capacitor. today i ran another 4 gauge wire to the distribution block
so i currently have (2) 4 gauge wires going to 1 distribution block ... my question is that i know i need inline fuses at the battery and of coarse everywhere where i put a smaller gauge wire coming off the distribution block. but what im confused about is. that in the 2 fuse holders at the battery for the (2) 4 gauge wires what size fuse should i have ? before i added anything i just had an 80 amp fuse and has been fine for about a year. is it ok to just put another 80 amp fuse in the other wire so that both the 4 gauge wires will have an 80 amp fuse ???

thankyou. also in the rear i ran an 8 gauge wire from the distribution block to the accessory fuse box. i put a fuse holder about 8 inches from the dist. block

to find out what size fuse to put there i should add up all the amperages of the fuse box correct ??? i.e. lights/power outlets ???

right now i only have a power outlet ( 25 amps ) in the acc fuse box so what size fuse should i put in the 8 gauge wire ??


sorry if my post if confusing... its hard to word all this wiithout sounding dumbb

thankyou in advance

 

[5-90]

Size wiring according to anticipated load. Size fuses according to actual load. Often, fuse specs are given by the manufacturer of whatever you're hooking up.

Fuses should be placed as close to the power source as possible, for the most protection.

So, you'll want to size the fuse for each accessory being "safed" - for instance, I've got a two-cavity 12VDC power outlet on the centre console, near the passenger's right knee. While it's rated for up to 30A in total, I've not had any more than 3A plugged into it. Therefore, it gets a 5A fuse (the circuit is designed for up to 35A, so I can simply sub a larger fuse in if I use it for more load.)

The power output I've got in the back is spec'd for 25A, and I use it for a 12VDC cooler (draw: 10A) Therefore, it gets a 15A fuse - even though the circuit is designed for 30A as well.

Does this make sense? You want to select wiring to allow for the MAXIMUM current that may be drawn on that circuit. Generally, I size wiring for 10% or so over whatever the peak draw/rating of the accessory is, a little overage is nice. However, I'll then fuse that circuit for the most I actually use it for - which explains the disparities I'd noted above. Just because I select a 30A power point, and supply it with a potential 30A, doesn't mean I give it a 30A fuse. I know the potential is there, so I've got it if I need it, but I select the fuse for what I actually use it for.

So, if you're feeding a secondary distribution point for a few amplifiers, take the fuses that are plugged into the amps, add them up, and add, say, 5%. Take that number, and use it to select the mains power fuse that you'll put in near the battery.

So, if you're feeding two amps that draw 30A each, add them up to get 60A. Add 5% - 63A. Use that as a guideline for selecting your wire size and mains fuse. You should be able to find a 70A or 75A mains fuse (PAL, ANL, or AGU,) and then size your wiring accordingly.

If the size is not conveniently done, or if it's odd, it's actually acceptable to use two feedlines in parallel, and "split" the fuse evenly over both feedlines (for instance, if you only need a 60A fuse - accounting for overage - and you can't get a 60A MAXI fuse, you can split it in half and use two 30A ATO fuses in its place.) The other rules still apply - put the fuse as close as possible to the power source or primary/mains distribution point, and split the fuse rating evenly. If you have to use three fuses, that can also be done - but make all three the same size (3x15A ATC should give you 45A circuit protection.)

Also, circuits should be fused individually - which makes troubleshooting loads easier. The rule of thumb is that the smaller fuse will pop first (not always, but generally,) and if each accessory has its own fuse, that makes tracking down shorts and overloads so much easier!

5-90

 

[generalleexj]

thanks soo much for you info, it helps alot,

just another quick question

but i have (2) 4 GAUGE wires going to the dist. block in the back so your saying that i should add up ALL the estimated amperages for the fuses... ?

example,

if i have 2 amps and acc. fuse box with 1 power outlet lets say the combined amps are about 90. so i should put a 45 AMP fuse on each of the 4 gauge wires ??? is this correct ? because i used to only have 1 4 gauge wire with an 80 amp fuse in it. if i put another 80 amp fuse in my new 4 gauge wire will i mess anything up or is that a bad idea ?

 

[BOB]

I ran a power distribution block to the cargo area.
I wired three circuits to the ignition and three have direct power, to a toggle switch up front by the driver.
I also ran a 1000 watt power inverter to the cargo area.
I need it to rum my 700 watt coffee maker

...BOB

 

[5-90]

thanks soo much for you info, it helps alot,

just another quick question

but i have (2) 4 GAUGE wires going to the dist. block in the back so your saying that i should add up ALL the estimated amperages for the fuses... ?

example,

if i have 2 amps and acc. fuse box with 1 power outlet lets say the combined amps are about 90. so i should put a 45 AMP fuse on each of the 4 gauge wires ??? is this correct ? because i used to only have 1 4 gauge wire with an 80 amp fuse in it. if i put another 80 amp fuse in my new 4 gauge wire will i mess anything up or is that a bad idea ?

2x45 = 90. 2 x 50 - 100.

2 x 80 = 160 - which is probably a bit much. Fuses are easy to change, so you can just change out your 80A fuse (keep it for a spare - you can use it to feed "essentials" off of that distro block if you pop your new mains fuses.)

5-90