Cable Mechanical Protection
The PVC sheath must enter into any enclosure to protect the conductor insulation from damage. Once inside the enclosure, the sheath can be removed because the enclosure now provides mechanical protection for the cable insulation.
There should be sufficient cable slack allowed in an enclosure to facilitate the termination and remaking of cables. This will also facilitate any alterations to the circuit or replacement of accessories. See Figure 49.
Terminating Techniques
Screw Terminal
There are a variety of methods used to terminate conductors. One of the most common types is the screw terminal. Regardless of the type of terminal used it is important that the joint between the conductor and the terminal is electrically and mechanically sound, without putting undue pressure on the conductor or the terminal. In other words the terminal screw should be sufficiently tight. The conductor insulation should be removed far enough to allow the conductor enter the terminal. The conductor should be insulated right up to the metal of the terminal. Stranded conductors should be twisted to form a solid mass. The cable sheath should be removed a distance of at least 20 mm. This must be done to prevent surface leakage current, allow more flexibility at the termination and also to identify the core colour.
If the conductor is small in relation to the terminal, the conductor must be doubled back fully, neatly on itself. See Figure 52 for a correct termination.
Screw Head and Nut and Washer Terminals
When terminating conductors under screw-heads or nuts, it is best to form the conductor into an eye, using round nose pliers. The eye should be slightly larger than the screw diameter, but smaller than the outside diameter of the screwhead, nut or washer.
The eye should be placed in such a way that rotation of the screw head or nut tends to close the joint in the eye. If the eye is put the opposite way round, the motion of the screw or nut will tend to untwist the eye, and will probably result in poor contact. The conductor should be wound at least three quarter way round the screw. See Figure 55.
Clamp Type Terminal
These terminals are used in a similar manner to the screw type terminal. They provide heavier clamping, generally for terminating larger conductors. The clamping plate may be ribbed in order to put small indents into the conductor to provide better electrical and mechanical contact.