I'm installing a fuse panel as part of my 12 volt upgrade on my '52. I know the original circuit breakers were only 30A and 15A, but what amperage should my new circuits be? I'm installing a 12 slot panel and am planning on running everything through that. I also have installed a LMC HD headlight harness, so I've moved the power out of the light switch to the battery.

 

it all depends on how you branch your circuits and what wire size you use. Install the fuse block as close to the power source as possible. If it is a higher current circuit, run the fuse block side to the control side of a relay. Cooling fan, fuel pump, head lamps etc.

 

Fuses are sized to protect the wiring, based on gauge, OR a lesser amount if you want to protect the equipment served. If you google "auto wire amp ratings" you'll find lots of charts.

 

Every electrical component has a maximum amperage that needs to be protected by a fuse rated for a lower amperage and a wire size sufficient to carry that amperage. If there is a problem with the circuit you want the fuse to
go before the component is destroyed or the wire burns. There are lots of automotive publications that give amperage and wire size for automotive electrical components.

 

In my last reply I need to correct the statement about Amperage.
If the devise uses up to say 12 amps the fuse would need to be 15 amps to assure enough power to run the devise before the fuse goes. Even if it uses 10 amps you'd still want to use a 15 amp fuse. In either case the wire would need to be able to handle more than 15 amps.

 

I've been using 14GA wire, which seems tough enough for a 12V system, I hope.

 

It really depends on the watts the devices attached to the circuit require. Volts x amps = watts. A 20 watt device at 6 volts would require 3.3 amps. The same 20 watt device at 12 volts requires 1.7 amps. Conversely, a 20 amp, 12v cigar lighter uses 240 watts or 40 amps at 6 volts.

So, choose the devices you want to place on a circuit, add up their watts or amps and do a little quick math. Don't know their requirements? Normally not difficult to find spec sheets online or look in the owner's manual of most cars to get an idea of the power required.

To learn about automotive electrics go to Autoshop101.com, click 'Online Instruction' on the left margin and begin with 'Electric Fundamentals'. It cracks me up how much time guys will spend on researching how to smear some bondo and sand it back off yet avoid learning about automotive electrics. If you use the site I mentioned you'll probably have fun and kick some electron butt when you're done. Shoot, you might even begin to finally understand The Big Bang Theory. LOL

 

Thanks for the math lesson. Doesn't seem so tough.

 

Thanks for the web site.