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Wiring & power

How to wire a DCC track bus and feeders

Run a heavy pair of bus wires under the baseboard with regular droppers to the rails, so every part of the layout gets full power and shorts are detected reliably.

Time
Half a day
Difficulty
Medium
Cost
Moderate cost
Steps
6
Checked
Report a problem
Track bus and droppersA command station or booster feeds two heavier bus wires that run under the layout, one for each rail. Short, lighter dropper wires join every length of rail to the bus wire for that rail, so rail A is always fed from bus A and rail B from bus B.Command stationor boosterBus wire A (heavier wire) → rail ABus wire B (heavier wire) → rail BDroppers (lighter wire) join every length of rail to its own bus wirerail joiners
Track bus and droppers A command station or booster feeds two heavier bus wires that run under the layout, one for each rail. Short, lighter dropper wires join every length of rail to the bus wire for that rail, so rail A is always fed from bus A and rail B from bus B.

What you’ll need

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Before you start

  • Soldering flux fume (rosin/colophony) is a known cause of asthma and skin problems. Work in a well-ventilated room, use a temperature-controlled iron and a fume extractor if you solder often, and consider rosin-free flux (HSE INDG249).
  • Turn off track power before soldering to the rails.

Step by step

  1. Step 1: Size the bus

    Digitrax recommends a bus of at least 16 AWG on an average layout, and 12 AWG where you feed areas up to about 15 m (50 ft) from the booster. Size up for heavier current.

    Next: step 2

  2. Step 2: Run the bus

    Run a pair of bus wires under the baseboard. Digitrax advises twisting conductors to reduce radio interference and wiring radially ('star' fashion) from the booster rather than in loops.

    Next: step 3

  3. Step 3: Plan the feeders

    Drop feeders of 22–24 AWG to both rails roughly every 2–3 m (6–10 ft), with at least two sets per power district (Digitrax).

    Next: step 4

  4. Step 4: Solder the droppers

    Drill small holes beside the rail, solder droppers to the rail (or rail joiners) and connect them to the bus. Keep red to one rail and black to the other throughout the layout.

    Next: step 5

  5. Step 5: Don't add capacitors

    Digitrax says never place filters or capacitors across the track – they distort the DCC signal.

    Next: step 6

  6. Step 6: Do the coin test

    With power on, short the rails with a coin or screwdriver blade at points around the layout (about every 3 m / 10 ft). The booster should detect each short and shut down, then recover once it's removed. If it doesn't, add feeders there (Digitrax 'quarter trick').

Tips

  • Use one colour per rail everywhere and note which rail is which on your plan.
  • Leave a little slack in droppers so baseboards can move.

Questions people ask

Why can't I just rely on rail joiners?

Joiners loosen and corrode over time; feeders keep power and the DCC signal even across the layout so shorts are detected (Digitrax).

Is the coin test safe?

It's a standard check that boosters are designed to handle – keep it brief.

Sources

Checked 18 October 2026. We wrote this guide in our own words, using:

  1. Digitrax DCS240 command station manual (digitrax.com)
  2. HSE INDG249: Controlling health risks from rosin-based solder flux fume (hse.gov.uk)

Tags: AWG bus coin test feeders wiring

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Related guides

Printed from dcctrainautomation.uk/guides/wire-a-dcc-track-bus-and-feeders/ · Checked 18 October 2026 · General information only. Follow the maker’s instructions for your own equipment, and keep mains wiring inside properly made, enclosed power supplies.