BadBarret

I was wondering if anyone knows if the wire to switch on the relay has to be of a larger gauge. Here is my scenario, I have assembled a relay box for 3 sets of lights and one spare. So the box has 4 relays. I have a length of 5conductor cord that is 14g however the insulation on each wire is thick and the overall diameter is fairly thick too I'd guess 5/8in. Problem is I can't find a place in the firewall to run a cord that large so I was going to replace that 5conductor with 5 separate lengths of wire which happens to be 18g. Question is would the relays draw that much for 18g to be an issue? Again this is just the wire to switch on the relay. Largest pair of lights set up would be a pair of 100w KCs.

14Sport

18 gauge will be fine for the control circuit. The relays only draw milliamps there.

BadBarret

Thanks for the quick response. I was pretty there wasn't much draw there but wanted to make sure. And then of course the lights themselves would would require a large gauge for the load side correct?

14Sport

Yes. Depends on the draw of the lights and length of the wire run. Don't forget with 2 lights on 1 switch you need to add the draws of each together. If you don't know the amp draw you can calculate it from the wattage. Wattage/volts=current in amps. Fuses should be rated a little higher than the draw. The relay should be rated higher than that so the fuse will blow first. Here's an online calculator for finding wire gauge based on draw and length. If you return the accessory ground to the battery instead of the chassis then the length of the ground wire has to be included in the calculation.

Wire Size Calculator

It is a good idea to fuse the control circuit with a 3A fuse as well.

And also a schematic if it comes in handy.



Or if you plan on running the load circuit separately...

BadBarret

Awesome. Thank you. The lights I'm working on now are 100w each. So that's 8.3a draw or 16.6 together. I have 12g automotive wire now just trying to find the amp rating so I'll look at your link. Each load is fused with 20a fuses to 4 total for each set of lights. Switches are fused with a 3a fuse and I have a 30a fuse in-line directly off the battery.

Edit: and the relays are 30a

BadBarret

Another question I have is would I have to worry if all sets of lights were on at the same time? The lights that will be running right now off the box are 2 KCs at 16.6a, 2 LED pods at 3a, and 2 factory dogs since my jeep didn't come with them. I assume factory fogs are what 55w each? So if that's the case they would draw about 9a together. So about 30a all together. So would that 30a in-line fuse cover that?

14Sport

It's very close but should. I believe the newer JK fogs are only 24 watts. If you do end up blowing it you could bump it up to the next level. And you really should match the fuses to the draw of the lights they're protecting. The faster the blow the better when it comes to a short.

Using the calculator, a 30 amp run of 10 feet for the load feed should be 8 gauge. Less than 9' could be 10 gauge. Less than 6' could be 12 gauge. If you change it to a 5% drop (which many guys do), it could be 12 gauge up to 14'.

BadBarret

Good point. So basically a 20a fuse for 2 LEDs drawing 18w a piece is a bit overkill huh. And I'll double check the fogs to verify the correct wattage

14Sport

Yeah it might be a bit much...lol...a 5 would be better. Go as big as you want on the relays as long as it is higher rated than the fuses. Bigger never hurt anything there. Most lights I buy come with a wiring harness which includes a switch and a fuse. Since you don't need either of those with an sPod or "home made" sPod, I usually just pull the fuse that came with the lights and use that.

And for the spare setup, I would run everything except pin 87. Then when you go to add the accessory, you just have the run the positive from the accessory to pin 87 and run the ground and you'll be good to go.

BadBarret

I double checked the fog light bulb and it is 24w. I don't know what I was thinking of, the headlights maybe. And I will definitely get the appropriate fuses for each set of lights. Thanks again for all the info! I really appreciate it.

Also the spare is all wired to the switch. Just the load end is open. I wired it just to verify the LED worked when switched on. It shouldn't hurt anything, I hope. The connecters are insulated so the metal is all covered by plastic.

Thanks Sport!