National Marine Electronics Association (NMEA) 2000 Practice Test

In NMEA 2000, the heavy cable carries two purposes: a power conductor to supply current to all devices, and a signal/data conductor for CAN bus communication. The power path must handle the total current with minimal voltage drop, so it uses a thicker gauge. The signal path carries only the small data current, so a smaller gauge is sufficient and more cost-effective. That’s why the practical pairing is a thicker gauge for power and a smaller gauge for signal data. A common and effective combination is 15 AWG for the power conductor and 18 AWG for the signal conductor—the heavier power leg reduces voltage drop, while the data leg remains robust enough for reliable communication. Choosing a thinner power conductor or a thicker signal conductor generally isn’t necessary and can add unnecessary cost or risk performance.