Oh how I wish I took a picture of that rocker switch the melted on me with my air horns.

I have a 200psi cutof switch on the tank with a relief valve. There is a bladed 20A breaker a few inches from the battery and was a 15/20A rocker switch under the dash. Well one night I forgot to flip the switch to off (which normally isnt an issue) but this particular night the tank must have been low. So the compressor kicked in. Not an issue right? Wrong. When it got to 200+ pounds the cutoff valve stuck and didnt cut the power. Well the relief vavle MIGHT have worked but theres no way to test it without over pressurizing it. But the breaker up front didnt flip (although it did discolor from the heat) and the 15/20A rocker switch decided to literally melt. Now IDK exactly what happened in what order but I do know 2-3 safety devices failed. The compressor did survive (thankfully) but the battery did not. It never held another full charge after that. Now, had I wired it the way is was supposed to have been ran with a SPDT relay, that switch never would have had to carry that load. Also, if the relay was used, the power would have been killed with the ignition. But I was in a hurry to install it and get it up and running. Needless to say, it is wired correctly now.

 

Im going to have to agree with dirty. I wired my light directly to the battery. battery->20A in line fuse-> 30A switch-> lights. All ran with 14 gauge wire, and grounded at the lights and switch. My buddy has a an air horn too connected to a compressor, and hes got everything hard wired and all controlled with 30A rockers. No problems yet.

 

That happened because the motor was under so much stress it was actually pulling much more amperage than it usually would because it couldn't force the air into the tank to pressurize it over that 200psi.
For the most part a device like that should be rated at 80% draw since it may peak/spike occasionally.
What do you mean a 15/20 rocker switch? It's either 15 or it's 20. If you put a 15amp switch and a 20amp inline fuse, that is also why the fuse didn't pop. The rocker was the weakest link at that point.
Do you know what the draw was on the compressor? Even 20amp seems kinda low. Most i thught were 30amp. The tiny one's are usually 15 and 20 but they are rated for maybe 110psi.

Car wiring is diff than house wiring. Car wiring can handle more current than a same gauge house wire. Most newer house wiring is 12awg wiring with a 20amp breaker. You can run up to 60 amps on that same 12awg wire in a car BUT, the fusable link needs to match the amerage draw of the specific product.

 

I think 'dog invented electricity.

 

I dont wanna get too much into this because its not my thread but the OEM fure with the Viair 380c that I have was 15 to begin with. After popping 2 from normal usage I went up to the 20A bladed breaker. As for the rocker being the weakest link, that was my point of the entire topic. I dont remember if it was a 15 or 20 at this time as that was more than a few months back since everything was installed.

 

No offense, but I think dog talks too much from theory and not enough from experience. I've been wiring my own car electronics for over 25 years and I have seen more than a few switches melt. You guys are acting like if the switch says 20 then there is no way it can fail. I am telling you from experience that things fail. And when they do they often start fires. DON'T BE STUPID. Hella includes a relay because they don't want to see a fire. Period. Sorry for the harsh words, but anyone who wires a high amp accessory without a relay is either inexperienced or foolish. Or both.

 

Wrong. If that switch fails you have no protection. You're relying on the numbers and missing the entire point- safety. What happens if that switch fails?

 

Im going to have to agree with Rubberfrog on this one. I went to school for Math and Engineering (Electrical) and did plant industrial maintenance (480-600v 3 phase) and currently do Risk Management which my job is primarily to check safety devices on equipment to ensure protection on persons and company property. A switch rated to handle a current but has no way of protecting itself or the circuit would not pass. As I said before also, I had a switch melt on me and am very thankful it did not start a fire because I was moving too fast and didnt protect neither my circuit nor my investment.

 

Im not trying to act like I know whats going on when it comes to electricity. Im just speaking off of what I have learned, and from what ive seen other people learn.

Would a properly sized in line fuse keep these switches from melting or failing causing fires? Or maybe incorrectly gauged wiring could have been used? When the rocker melted from the train horns, what size wiring was used to switch; was there an in line fuse? I just think maybe we should throw some solutions out there, instead calling people stupid.

 

Well I dont think anyone is calling anyone else stupid. Im certainly not. But yes an inline fuse would be a protective device and should be used in any circuit. I cant speak for anyone else but in my case I replaced the 20A fuse and a 20A bladed circuit breaker simply because I didnt want to keep having to replace the fuse if needed. However, im my case I should have left the fuse because it provies a permenant disconnect of power whereas the breaker will open when too much current flows through (it gets hot) and it will close (when it cools) and allows current to continue to flow. This likely kept happening until a few things happened

1) the switched melted and
2) the battery could not take any more and gave up the ghost.....LOL