What wire should I use for a CDU

From the gauge to the length, choosing the right wire is key to the operation of a CDU and point motor. Read this quick guide to the best wire for your CDU.

When it comes to model railways, a CDU or Capacitor Discharge Unit makes a big difference to the reliable operation of solenoid-type switch motors.  If you’re unsure what a CDU is the sister post to this article, what is a CDU and why do you need one, will help.

But to ensure that your CDU, whether it’s from Gaugemaster or BLOCKsignalling  is functioning properly, it’s essential to use the correct wire for the job. Using any old wire that you have laying around isn’t recommended and there are a few things to keep in mind when selecting the wire for your model railway CDU:

Recommended wire gauge For CDUs

The gauge of wire refers to its thickness. A thicker wire will be able to handle more current, while a thinner wire will have less resistance. For CDUs, it’s recommended to use a wire gauge of at least 16 AWG (American Wire Gauge) / 18 SWG (Standard Wire Gauge) approx. 1.22mm.

Stranded vs. Solid

There are two types of wire construction: stranded and solid. Stranded wire is made up of multiple small wires twisted together, while solid wire is a single piece of wire. Stranded wire is more flexible and easier to work with, but can also be more expensive. For a CDU, stranded wire is recommended for its flexibility and ease of use.

Length for CDU wiring

The length of the wire will depend on the size of your model railway layout and the distance between the CDU and the track. It’s important to measure carefully and ensure that the wire is long enough to reach the track without any tension or strain. When using a single CDU to power multiple solenoid motors, I put the CDU in the equidistance to all the points and then use daisy-chained terminal blocks or a distribution board to connect to the individual solenoids. (The distribution board takes the CDU output as its input and provides a number of output terminals for the point motors).

In summary, when selecting the wire for your model railway CDU, it’s essential to choose a wire gauge of at least 18 SWG/AWG, stranded construction for flexibility, PVC insulation for durability, and the appropriate length for your layout. By following these guidelines, you can ensure that your CDU is functioning properly and that your model railway runs smoothly.

If this has proved useful, you might be interested in my round-up of must-have books for model railway electrics. And finally, if you’re looking for more information on electrics for railways, subscribe to my free newsletter where I regularly cover this topic.

Founder of ModelRailwayEngineer, Andy Leaning

Andy is a lifelong modeler, writer, and founder of modelrailwayengineer.com. He has been building model railways, dioramas, and miniatures for over 20 years. His passion for model making and railways began when he was a child, building his first layout at the age of seven.
Andy’s particular passion is making scenery and structures in 4mm scale, which he sells commercially. He is particularly interested in modelling the railways of South West England during the late Victorian/early Edwardian era, although he also enjoys making sci-fi and fantasy figures and dioramas. His website has won several awards, and he is a member of MERG (Model Railway Electronics Group) and the 009 Society.
When not making models, Andy lives in Surrey with his wife and teenage son. Other interests include history, science fiction, photography, and programming. Read more about Andy.

Afflliate disclosure:The links on this page may take you to carefully selected businesses, such as Hornby, Amazon, eBay and Scale Model Scenery, where you can purchase the product under affiliate programmes. This means I receive a small commission on any orders placed although the price you pay does not change. You can read my full affiliate policy here. I also sell my my own ready to use, pre-made and painted buildings and terrain features. browse the range.

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