What silicone insulation gives you
PVC insulation softens as it warms and goes stiff and eventually brittle as it cools. Silicone does neither across a much wider band, which is why it turns up around heaters, engine bays, ovens, lighting and anywhere a loom has to survive both a cold morning and a hot working temperature.
It is also far more flexible for the same conductor size, partly because the insulation itself is soft and partly because silicone wire is normally built with a much higher strand count. Where PVC hookup wire might use a few dozen strands, silicone wire of the same gauge often uses hundreds of very fine ones, and that is what lets it bend tightly and take repeated movement without work hardening.
The trade is mechanical. Silicone cuts, abrades and tears far more easily than PVC, so anywhere it passes an edge, through a bulkhead or against a moving part it needs a grommet, a sleeve or braiding over it. Fitted carelessly it will chafe through where PVC would have survived.
| Condition | Silicone | PVC |
|---|---|---|
| High or low temperature | Holds up across a wide band | Softens hot, stiffens cold |
| Repeated flexing | Very good, fine strands | Work hardens and fractures |
| Abrasion and edges | Poor, needs protection | Much tougher |
| Cost | Higher | Lower |
Fine strands, and why they need ferrules
The strand count that makes this wire flexible is also what makes it awkward in a screw terminal. Hundreds of very fine strands spread out under a clamping screw, some escape the terminal entirely, and the ones that are captured flow away from the pressure over time until the joint loosens.
A bootlace ferrule crimped on the end solves it completely. The strands are gathered into a solid sleeve, the screw clamps that sleeve, and the joint holds its torque. On this kind of wire a ferrule is not a refinement, it is the correct termination.
Do not tin the end instead. Solder creeps under sustained clamping pressure more than copper does, so a tinned end that is tight today is loose within months, and on fine stranded wire the wicking also creates a stiff point right where the wire wants to flex.
Gauge, current and the conditions around it
Conductor size is quoted in AWG or in square millimetres, and the two run opposite ways: a smaller AWG number means a larger conductor. What a given size can carry is not a single number, because it depends on how much the wire is allowed to warm and how easily that heat escapes.
The same wire carries less inside a bundle than it does in free air, less in a hot engine bay than in a cool cabinet, and less over a long run where voltage drop rather than heating becomes the limit. Silicone insulation tolerates a higher conductor temperature than PVC, which is part of why silicone wire is often quoted at a higher current for the same gauge, but the surrounding conditions still decide the real answer.
For a long run, size for voltage drop rather than for current alone. A cable comfortably rated for the current can still leave too little voltage at the far end, and on low voltage systems that shows up as equipment that misbehaves rather than as anything obviously electrical.
Tinned copper, and where it earns its cost
Bare copper oxidises. In dry indoor air that surface film is slow and harmless; in damp, salty or chemically active air it creeps along the strands under the insulation, raising resistance from the ends inwards and eventually turning a good joint into a warm one.
Tin plating on each strand slows that considerably, which is why marine and outdoor wiring specifies tinned copper as a matter of course. It also takes solder more readily and stays solderable after storage, which matters if the wire is going into a workshop drawer for a year before it is used.
For dry indoor equipment, plain copper is perfectly sound and cheaper. The decision is about the environment the wire will live in rather than about quality, and buying tinned for a bench project is spending money the job does not need.
