That is very unlikely at the low voltages we are dealing with unless there is a defect in the insulation. What does get transmitted through the insulation is the electromagnetic waves which could cause interference to adjacent wires, but a dead short is highly unlikely.

If you are experiencing a dead short between 2 insulated wires touching each other at a nominal 20V, there has to be metal to metal contact somewhere.

Peter

The effect here is 'induction' and when it is intended is very useful - Transformers being the example we are most commonly exposed to in our Hobby but I agree with Peter that at the low voltages we are talking about here, any detectable short-circuit would be unlikely.

On the other hand, those of us that deal in the IT world are well aware of the problems that can arise from incorrect shielding and a good example is twisted-pair Network cabling. Interference or 'cross-talk' from one pair to another can be quite a problem which is why Ethernet cable is twisted within the sheathing in a very specific manner and even bending the wire incorrectly can lead to degradation of the signal.

Without seeing your setup Silvano it's hard to imagine what may be the issue but don't overlook things such as any staples used to secure cabling, or a single stray strand of twisted-flexible wire that might be making contact with an adjacent terminal, or two adjacent plugs with exposed screws making contact.

These shorts can be hard to track down and it can be helpful to 'divide and conquor' your wiring to find the culprit. Isolate the circuit that is giving problems, and make sure it's disconnected at both ends, then start your troubleshooting wire by wire, preferably using a multi-meter set at the lowest resistance setting and then the highest just to be sure.

Hope this helps

Steve

I'm not sure what you mean by sheathed wires. That in electrical terms normally means it has a metallic covering either as a braid or foil which is used for added protection or shielding as previously mentioned by Steve. Based on your previous description I do not believe you are using sheathed wires. However, if you are and depending on how the sheathing is connected on each wire (normally grounded at one end) you could have a potential of creating a short if the sheathing on one wire is connected to the brown "O" and the sheathing on the other wire is incorrectly connected to "B' for some reason. If that were the case touching the sheathing together from these two wires would create a short.

Marklin wire for whatever reason does not have the voltage rating (or any other information) marked on the insulation. However, other manufacturers' insulation quite often shows that the insulation is good to 300 V for this gauge of wire. Therefore, even though it is very thin, contact between the insulation of two wires at 20 V should not have any possibility of creating a short circuit. You need to look elsewhere as to where you are getting metal to metal contact between the two wires that is causing you the grief. As Steve pointed out it is usually at a termination point where you can have a very fine single strand of wire sticking out and touching the adjacent connection or even the screws from adjacent banana plugs touching each other. Moving the wires to separate the insulation contact may be enough to move the touching strand of wire or screw contact to eliminate the short circuit, but not the overall problem.

Peter

A single wire (solid core or stranded core) covered with PVC, nylon, etc. is referred to as an insulated wire. A group of insulated wires bundled together and covered by another material becomes a cable. That additional covering can be considered the sheathing and can be metal, nylon, PVC, various layers of different material depending on intended use, and so on. In Canada a good example would be our NMD90 house wiring. For a normal 15 A circuit the NMD90 cable consists of a Black insulated wire, a White insulated wire, and a bare copper wire, all covered by a nylon sheath if installed in wood frame walls, or similar CORFLEX type cable with an interlocking aluminum or steel sheath if being installed in metal stud walls.

For us in model railroading we generally use insulated wires for the power, accessory and lighting feeds, possibly twisted pair cables for communication and feedback circuits, and I know some modelers use telephone cable for their signal controls. So what you use depends on what the voltage and current draw is expected to be.

I assumed in your posting that you meant insulation by sheathing, but based on your problem I just wanted to rule out the possibility of you actually using metallic sheathed cables that could have the sheathing connected differently between 2 cables.

Cheers
Peter

No I am not thinking of shielded wire per-se, however, the thought crossed my mind that he may be using shielded wire since he is getting a short circuit by touching the two wires together on their insulated portion.

Perhaps in the UK sheathing and insulation are interchangeable words. However, as per my follow-up post a single wire here is normally referred to as an insulated wire, not a sheathed wire. A cable on the other hand containing several insulated wires has an outer sheathing that can be metallic, nylon, PVC or other material.

It's a matter of terminology as used in the electrical trade that can cause misunderstandings as to what is actually meant if someone refers to sheathing.

Cheers
Peter