Hi, I'm installing a cutoff switch in my car. The fuse I want to use is 30amps. I'm unable to locate a 30 amp preferably a rocker style but a toggle switch will due.2 questions Am I correct in assuming I need a 30amp switch? Where can I find one.The boys amp; a few other stores including radio shack doesn't have them Thanks
You're probably better off using a relay, controlled by a switch, rather than just hot wiring the switch itself.
Yes, if you want to put a 30 amp circuit in, you need to use a switch rated at 30 or more amps. The amp rating on the switch is the maximum it was designed to handle. You could use a 30 A fuse and a 50 A switch if you wanted to. The fuse should be rated at the same rating as the lowest rated component. Example, if you have wires that can handle, 20 amps, a relay rated for 40 and a switch rated for 30, you would need to put a 20 A fuse in (max). The power consumption of whatever you're trying to power doesn't matter for this purpose. It has to simply be less than the fuse. That being said, I agree with JetDoc. Use a relay. There are 4 terminals on the relay. Two for the switch and two for the device. You put your 30 A circuit in and feed constant power to the proper terminal. Then feed the device from the relay (which should be rated at at least 30 A). Then you put constant power to a switch. Any switch would be fine. Relays use hardly any power. From the switch you run a line to one terminal on the relay and the final terminal is grounded. I added a picture of a common relay. All relays should have a mini schematic on them to tell you what terminal is what on the bottom. For example, this one has terminals 30, 85, 86,and 87. 86 and 85 should be used on this one for the constant power and a feed to the device. It doesn't matter which is which. 30 and 87 should be the the switch and ground. Again, doesn't matter which is which. Some specify which to use as a ground, but it doesn't usually matter. Ignore the relay on the left. That's a 5 pin and you don't need it.
