Re: [A/S] Re: 12 Volt Amp Limit?

[Rick Kunath <k9ao@xxxxxxxxxxx>]

> I disagree with the wire size/ amperage figures, though- I would go the same 
> as 120 volt power- #10- 30 amps, #12,- 10 amps, #14- 15 amps, etc..

Not exactly...

You may be able to tolerate a 3, 4 or maybe even a 6 volt drop with some 
electrical devices that are running on a 125 volt AC circuit at the 
receptacle. You can't tolerate this voltage drop on a 12 volt DC circuit.

Take a long hard look at the wire's resistance per 1000 feet. Divide it 
down to a per foot value and multiply that by the run length you are 
planning on doing. Make sure to double the wire footage if you are doing 
a red and black wire back to the 12 volt supply. Then take that 
resistance value and multiply it by the current you are planning on 
drawing, and you'll have the voltage drop the 12 volt device will see at 
the receptacle.

I think you'll be surprised at how much loss there is even with wiring 
rated per 125  AC volt usage.

On 12 volt DC circuits, it's usually the voltage drop value that drives 
using much larger wire gauge than the 125 VAC tables would suggest. So, 
it isn't safe to just use the 125 VAC ratings when sizing wire for a 12 
volt DC application.

It's all about voltage drop at the load. I'd up size the wire gauge 
appropriately.

Rick Kunath
WBCCI #3060