Wire Gauge Selection Guide
Using the correct wire gauge ensures reliable power delivery and prevents voltage drop issues.
Quick Reference
| Application | AWG | Notes |
|-------------|-----|-------|
| Track Bus | 12-14 | Main power distribution |
| Sub-bus | 16-18 | Branch feeders |
| Feeders | 20-22 | Track connections |
| Accessories | 18-22 | Depends on current |
| LEDs | 24-28 | Low current |
| Decoder wiring | 30-32 | Very low current |
Track Bus Wiring
NMRA Recommendations (TN-9)
- Maximum 5% voltage drop
- 12 AWG for runs over 30 feet
- 14 AWG for most layouts
Bus Configuration
- Run as loop or dual-ended
- Twist wires to reduce interference
- Color code (red/black typical)
Feeder Wiring
Spacing
- Every 3-6 feet of track
- More in problem areas
- Essential for reliable DCC
Size
- 20-22 AWG adequate for feeders
- Keep feeders short (under 12")
- Solder directly to bus
Voltage Drop Calculation
V_drop = I × R × L × 2
Where:
- I = Current (amps)
- R = Resistance per foot
- L = Length (feet)
- 2 = Round trip
AWG Resistance (per 1000 ft)
- 12 AWG: 1.6Ω
- 14 AWG: 2.5Ω
- 16 AWG: 4.1Ω
- 18 AWG: 6.5Ω
Color Coding
Maintain consistent colors:
- Red: Rail A / Positive
- Black: Rail B / Negative
- Blue: DCC common
- Green: Ground/safety