In Europe cross-sectional area (or in some cases number of strands and diameter of each) is used. Wire size here is given in American Wire Gauge (AWG), but this measure isn’t used in the rest of the world.

Motor decoders used with DCC will also use Pulse-Width Modulation ( PWM) to control the motor, another form of variable-frequency AC using maximum frequencies around 15,000 - 30,000 Hz. This is typically low-voltage DC, but may also be Digital Command Control (DCC), which is a form of AC using variable frequency signals ranging from about 100 Hz to about 10,204 Hz (the normal maximum is around 8kHz). If you believe any of this material is in error, please send me an email at the address on the About the Site page.Ī model railroad uses wire to provide electricity to trains and to scenic elements (building lighting, for example). See the Derivation page for further information about these tables, and where their data came from. Follow your local electrical codes for anything those codes cover if they are more restrictive than what’s presented here, and even if low-voltage wire is exempt use them as a guide to maximum “safe” current levels. That doesn’t mean that it’s right, and it’s quite possible even with my numbers that a wire could get hot enough to damage a model.

What I’m presenting here is my current “best guess”, and what I’ll use for my own model railroad layout. I’m a hobbyist with some technical knowledge (just enough to hurt myself). One note of caution: I’m not an electrical engineer, or any kind of electrical expert. The type of electrical insulation used also is a significant factor. Wire in open air dissipates heat more efficiently than wire in a closed space.

More heat than can be dissipated will raise the temperature, until the wire or the insulation melts, or until objects adjacent to the wire reach their ignition point and catch fire. Ultimately this is related to the heat produced by current flowing through the wire, and the wire’s ability to dissipate that heat.

The ability of a wire to carry current without failure, known as its Ampere Capacity or Ampacity, depends on a number of factors including the diameter, voltage, frequency, composition, insulation and environment.

Wire ampacity chart