# Current chart for 110 volts and 12 volts?

Solar Expert Posts: 57 ✭✭✭✭

http://i384.photobucket.com/albums/oo289/easytim/wirechart.jpg

• Banned Posts: 17,615 ✭✭
Re: Current chart for 110 volts and 12 volts?

Where did you get that info? The relationship between current and wire size is Voltage independent.

Try the chart here:

http://www.powerstream.com/Wire_Size.htm
• Solar Expert Posts: 57 ✭✭✭✭
Re: Current chart for 110 volts and 12 volts?

It did not look right from the start, found it on the internet
• Solar Expert Posts: 10,300 ✭✭✭✭
Re: Current chart for 110 volts and 12 volts?

try this one
the wire size is dependent on many factors as what the current is, the length of the wire, at what temperature, and the voltage drop as a function of the base voltage for the voltage drop percentage.
• Registered Users Posts: 5
Re: Current chart for 110 volts and 12 volts?

The ampacity of the wire doesn't change because of voltage.
10 ga wire is 30 amps...always
12 ga wire is 20
14 ga wire is 15
Voltage drop is another matter altogether.
Re: Current chart for 110 volts and 12 volts?

Well--Ampacity of the wire in any particular application also depends on insulation type, ambient temperatures, conduit fill factor, etc., etc... The NEC tables have lots of options for different situations.

NEC (USA National Electric Code) is pretty conservative. Lots of the solar wiring is low voltage run in "free air" with lots of cooling from air flow. And so people do design for more current than NEC would allow.

Also note that for low voltage solar systems--we frequently have to use much heavier wire to keep voltage drop reasonable...

3% voltage drop on a 120 VAC wire is only 3.6 volts drop... Not a big issue. 3.6 volt drop on a 12 volt battery bus--would give us 8.4 volts at the load--Obviously, well below the 10.5 volts most 12 volt devices consider a "dead battery" voltage.

We do, however, try to be "safe" with our recommendations. It is difficult to know what anyone is doing as we are not there to watch / help / cause problems ourselves. :roll:

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 10,300 ✭✭✭✭
Re: Current chart for 110 volts and 12 volts?
The ampacity of the wire doesn't change because of voltage.
10 ga wire is 30 amps...always
12 ga wire is 20
14 ga wire is 15
Voltage drop is another matter altogether.

you are correct that the ampacity does not change because of the voltage, but the voltage does come into play for the percentage that the voltage drop presents at a particular current. voltage drops are quite dependent on many factors and is not a straight forward one rating for any length of any particular gauge number. what you cite is generally ok for most household utility ac circuits, but as bb said not for the smaller dc voltages. what you present is too overly simplified and is rare to apply well enough to the lower voltage dc seen in solar.
• Registered Users Posts: 5
Re: Current chart for 110 volts and 12 volts?

niel, thanks for the input. I wasn't addressing voltage drop in my post, just pointing out that the chart shown by the OP was flawed completely, and it should NOT be referenced for any amperage calculations. The chart shows the amperage rating being different at different voltages and that is completely incorrect. A basic understanding of OHMS law will make those calculations a simple matter. The suggestion that you could use a #10 wire for 100 amps is just absurd.