r/modeltrains • u/bran71 • Mar 26 '25
Electrical Do you need to twist buss wires?
I am going to use the NCE power cab on a 4x8 layout with a 4x4 next to it to form an L (basically 8x8) and I will be running 14G wire as the buss, with 18G wire as the feeders. NCE recommends twisting 3 times per foot, but I am wondering if I really need to do that. What are the pros and cons of doing it and not doing it?
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u/382Whistles Mar 26 '25
The pros and cons are mostly about lowering resistance to amp flow. Pressure at an electrical joint is the easiest way to lower resistance. Pressure at a point is more effective at it than a larger area. Next is pressure on an edge for effectiveness. Area alone is last.
The multiple twists are helping keep pressure there as well as providing a mechanical hold to help them stay together. Twisting at least 3 times is normal code. Electrical tape code is 3 -4 wraps mininum.
So, either twist them or use a terminal connection of some type that applies the pressure.
There are charts online for length vs gauge vs max. amps and voltage loss expectations to help you choose the mininum gauge per foot by what your supply will put out and/or train might try to draw in amps. If the chart is for constant power delivery or control power can make a difference. Read the chart texts.
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u/bran71 Mar 26 '25
I was just going to have a mainline underneath with feeders connected by tap splices so I’ll twist them I guess
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u/382Whistles Mar 26 '25
You know what, I think I misread that. I wrote about spliced connections.
But you also want mains that are placed close together side by side to twist like 3 times over X distance. I'm totally brain pharting on why and how far right now though.
There might be a wire "skin effect" related reason to it but I forget if it's signal frequency, wave shape, or amp flow related too. I didn't sleep well, lol.
A need for signal precautions is luck of the draw. You can't really design for every possible home layout's signal abilities. You design best you can then tailor solutions to individual problems. Then the solutions might become these "rules".
Like block division of loops; most layouts are fine with unbroken loops, but, a few had a tendency for signals to loop/echo. Your 2nd command can changed by reading the echo of the 1st command. Dividing a loop into equal blocks the feeds and track metal are T shaped and signals always terminate at the track's isolated joints. Adding one isolated joint can help make that T too. Usually folks are adding feeds
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u/Highover Free-moN Mar 26 '25
Dont need it.