Jointing and Soldering

Jointing and Soldering Points : jointing and soldering, jointing of bare copper conductors, jointing of insulated conductors, jointing of metal-sheathed cables, jointing of heavy cables, general precautions of jointing and soldering Joints between conductors are today carried out with the aid of mechanical junctions, and for small cables in particular the system of making twisted, scarf and married joints has been shifted to telegraph wires and temporary wiring. Usually the wires and cables are manufactured in 100 meters lengths. For house wiring, the length may be more or less that 100 meters. It is very necessary that the joints should be mechanically and electrically strong. Its importance is realized when damages are caused by bad joints. Hence, ii is worthwhile to have good practice for making efficient joints. Jointing of bare Copper Conductors In providing a joints of any kind, contact surfaces must be made such that the resistance of the electrical path does not exceed to ‘that of the unbroken conductor. In this case it can be achieved by thoroughly cleaning and ‘wire brushing, followed by a coating of tinning to prevent oxidation before applying pressure between the surfaces to be joined. Jointing of Insulated Conductors The outer braid should he removed by slicing with a pocket-knife, ensuring that the rubber and the conductors are not cut or nicked. The serving tape should he removed and the braiding cut back farther than the rubber arid the conductor, thus preventing moisture being carried along the braid to the conductor itself. A good compounded insulating tape should be used to provide a sea! For the outer braiding. Jointing of metal-sheathed cables In jointing of metal sheathed cables, the same care must be taken as in jointing the insulated conductors and in addition an mechanically and electrically continuous joint must be made in the metal sheath. This is normally affected by means of suitably designed metal junction boxes with mechanical gripping devices to provide satisfactory and speedy methods of jointing without the use of solder. Jointing of Heavy cables The jointing of heavy cables, and particularly those of multicore type employing copper, aluminum or lead sheaths, is a matter for considerable skill and care. Jointing of this type of cable is carried out in a specially designed cable box designed to carry all such jointing suitably insulated and protected and ‘providing continuity for the metal sheath either by means of mechanical grips or wiped glands connecting the sheaths of the cables to be joined together via the box itself. General Precautions of Jointing and Soldering (1) The jointing should be carried out as far as possible in switches, ceiling roses or in junction boxes.
(2) It should never be done inside the conduit.
(3) It new installations or repairing works, it should be made strong mechanically as well as electrically.
(4) It is preferable to solder the joint.
(5) The soldered joint should be taped.