Russ Bellinis said:
It is based on ohm's law. I think it is talking about 2.3 amps at 110 volts. When you lower the voltage, you can increase the amperage, so at 12-14 volts you can probably safely handle 10 amps.
I have to correct this one. The voltage controls the current through the wire, but the wire does not know the voltage, only the current. 2.3 amps is 2.3 amps. The wire has a resistance, as pointed out later, and hence will drop a certain voltage through the wire dependent only on the current. This generates heat, which is the reason for the limitation of current in the wire for safety reasons.
However, in the DCC bus application, the voltage drop through the wire becomes important to us before the safetly implications kick in, depending on the bus length. Without going through the process, the general answer is that #18 is probably a bit small for your bus, #16 would be ok, #14 would be even better.
Since you have #18, you could double up the bus with that, and be fine, too.