Ferrules: why hexagonal crimping makes the difference

Ferrules are one of those things everyone assumes are fine as long as the wire stays put. Yet a large share of faults in control panels start exactly here.

What goes wrong with a bad crimp

Pliers with flat jaws squash the ferrule flat. The wire is then tight on two sides and loose on the other two. The contact area is far smaller than it looks, and all the current runs through it.

Less contact area means more resistance, and resistance becomes heat. That heat makes the copper expand and contract, so the joint slowly loosens. That is how you get a connection that works for months and then suddenly does not.

Hexagonal or square crimping compresses the ferrule evenly from all sides. The wire is enclosed all round and the pressure is the same everywhere.

The size has to match

A ferrule too large for the wire will not grip no matter how hard you squeeze. Too small and you cut strands while inserting. Use the colour code: it is standardised, so grey is 0.75 mm², red is 1.0 mm², black is 1.5 mm². That saves guessing.

For two wires in one ferrule you need the twin entry type. Stuffing two wires into a regular ferrule works exactly as badly as it sounds.

Method

Do not strip too long. The insulation should reach the collar of the ferrule, with no bare copper visible between ferrule and insulation. Stripped too long means bare copper beside the terminal, and that is where it shorts.

Do not twist the strands before inserting. With fine stranded copper you push strands outwards that then end up alongside the ferrule.

Tug the wire after crimping. If it moves, the size or the crimp is wrong. Redoing it takes ten seconds, hunting for it later takes an evening.

A hexagonal crimping set for 0.08 to 16 mm² covers nearly everything you meet in a house, a panel or a camper.

Where it matters most

Anywhere that vibrates or gets warm. A camper, a boat, a trailer, a panel with frequency drives. In a fixed installation in a dry meter cupboard a mediocre crimp still gets away with it. On the road it does not.