Wires - Bus Wires and Feeder Wires

Wiring questions are common in the various discussion groups where I participate:

• What type of wire should I use?
• What are feeder wires for?
• What are bus wires for?
• Where do I need to put feeder wires?

These notes and recommendations are from my personal experience. As with anything in model railroading, some people will quote their own opinions as rules, which I'm not doing. I've had good luck following these standards that I've set for my own railroad, but your mileage may vary. 

Bus Wires

For a very simple layout, like the one I started with, I had two wires going from the power pack to the track and that was it. While that can still work, it's not the best approach for a layout of any size. The best design, regardless of whether you're doing DC or DCC, is to run heavy gauge bus wires under your layout. These bus wires are typically larger gauge (meaning a smaller number) and are more efficient carriers of electricity than nickel silver track is. 

I currently use 14 gauge stranded copper wire as my bus wires. I actually have three different pairs of bus wires in portions of the layout:

• Red/Black - track power
• Blue/Black - LED light strip power
• Green/Black - Tortoise power

When I get to the point of putting in lighting in structures, those LEDs will probably be connected to either the Blue/Black bus or a separate bus that could be controlled with a separate switch. 

These bus wires go out from their corresponding power supplies and "terminate" at the ends of the benchwork on a terminal strip. There's no reason to loop them back to complete the circuit. Instead, the circuit is completed through the device they are connected to. In the case of the track, the locomotive's circuitry completes the circuit. An example of a terminal strip is shown here:

There is also a smaller "Molex" style terminal strip that you can use for smaller diameter wire. Here's an example of that type of strip:

The red and black wires are connected to a detection coil, as well. These strips are available at Amazon for a few cents per strip and can be cut to length.

Feeder Wires

Feeder wires are probably the most important thing you can do to ensure good conduction of power to your locomotives. For my feeder wires, I use 20 gauge copper wire that I solder directly to the track. I use heatsinks while soldering. A heatsink is a piece of metal that clips onto the rail on either side of your solder joint to draw off the excess heat. I use alligator clips or metal hemostats, and this saves the plastic ties from melting. I also use a soldering iron with a pencil tip, which concentrates the heat on a smaller location, which also helps. 

Under the layout, I use 3M Scotchlok connectors to connect the feeder wire to the bus wire. Some people will argue that you should solder, but I prefer the connectors and have had no issues with them at all. Others will argue that the connectors will fail, etc.. but I have seen no evidence of this, as long as you're buying the quality connectors from 3M. There are some cheap knockoffs that aren't made as well. Here's what the connectors look like on after being connected to the bus wire:

This was one of the first sections I did. In my main yard, I actually ran a parallel set of bus wires and spaced the connections out to make them easier to see and to shorten the feeder wires a bit. 

The other feature I have on the mainline of my railroad is that I'm doing block detection using detection coils from RR-Cirkits. In order for this to work, I take the red feeder wire and pass it through the center of the coil. That coil is then connected to a circuit board using Cat 5 network cable. The downside is that the coils are only large enough to get three wires through, so if I have more than three feeders to a section of track that is being treated as a single block, I have to solder the feeders to each other. This is an example of the coil I'm talking about:

Placement of Feeder Wires

If you've just got a bunch of straight track and no turnouts/switches, I put feeders on every other section of 3' flex track. I've seen no issues with voltage drops in those short distances. Some people will argue that every piece of flex track needs feeders, but I choose not to follow that suggestion. 

Another factor affecting feeder wire placement is where your turnouts/switches are located. Most turnouts are set up with an insulated frog, which means the power will not flow through the turnout if the turnout is thrown against a section of track. While that may be fine, I choose to run feeders to every segment of track, as shown in this photo of my engine servicing track area. 

The red X's mark where I've added feeders. This allows engines to be powered on regardless of whether the turnout is routed to that segment of track or not. I follow the same practice anywhere I have a turnout. In this part of the layout, the positive feeder actually runs through a simple SPST switch, which allows me to kill power to that track or segment of track. This reduces the electrical load from sound-equipped engines that I don't always want "idling".