Conductors should be visible all throughout a cleat wiring. In temporary installations wiring is often done over bobbin or knob insulators in place of cleats. Whenever the wires pass through a floor or through a space where some damage is apprehended, they should be provided with an additional protection of a special strong covering up to a height of 1.5 metres above the floor level.
For this purpose, while the wiring passes through a wall or a partition, it should be taken inside a tube or a pipe or a conduit made of non-inflammable and non-hygroscopic material. Porcelain wall-pipe, lead wall-tube, iron conduit etc. are the examples of this type of covering.
Wooden Plug:
The wooden plug which is to be fixed up and cemented into the wall must be made of good teak wood or some other hard wood. Its length must not be less than 5 cm (2 inches). The outer surface area of the plug should be at least 1.9 cm x 1.9 cm (3/4″ x 3/4″), while the area of inner surface which remains grouted into the wall should be at least 2.54 cm x 2.54 cm (1″ x 1″).
Where the work is done with great care, two dents of at least 1.27 cm (1/2″) in diameter and 0.846 cm (1/3″) deep are made on opposite sides of the plug. Later a hole is made into the wall, and when the wooden plug is set into the hole and cemented, some cement is forced into the dents and this keeps the plug durably fixed in position.
ADVERTISEMENTS:
At first straight marking is done by holding a taut piece of thread along the path of the wiring. Later, holes are made into the wall along the said marking at regular intervals of 45 cm (1 1/2 ft.) or 60 cm (2 ft.). The wooden plug is so set that its outer surface remains 0.635 cm (1/4”) lower into the hole than the wall surface.
Later this is made flush with the wall by means of cement. Square holes are to be made where small bobbin insulators are used [see. fig. 127 (b)]. The screws with which cleats are fixed should be immersed in oil before use. This prevents the growth of rust on the surface of the screws and helps to tighten up the screws properly.
Installation of Wiring:
Wiring is installed along the wall below the beam. If it is to be taken from one room into the next, a hole is drilled into the common wall. A tube made of porcelain or metal is set into the hole, and wiring is taken through the tube. This is called the wall-tube. The length of the tube should be selected according to thickness of the wall. If the tube is made of metal, two bushes made of wood or ebonite are to be so fitted at its two ends that at the time of drawing the wires, the insulation of the wires must not get rubbed against the sharp edges of the tube and thereby get damaged.
Usually two pieces of wires are drawn through the same wall-tube. In case of a.c. circuit, particularly, this practice must be followed where metal tube is used; otherwise there will be a constant loss of electric energy due to heating of the tube.
If there are wooden beams in a house, cleats may be directly fixed on the beam for drawing wires up to ceiling roses. But if there be an iron beam, then space permitting, a piece of wood may be tightly fitted on one side of the beam and cleat is fitted on this piece of wood. This is shown in fig. 119.
If space is not sufficient for fixing a piece of wood on the side of the iron beam, at first pieces of wood are clamped at intervals to the bottom of the beam and then the cleats are fixed on these wood pieces. This is shown in fig. 120. The spacing between two consecutive pieces of wood should be such that the wiring must not sag within a few days due to its own weight.
If the wires are to be drawn under the iron beam from one cleat to the next, arrangements are provided as shown in fig. 121(b). Here clamp is made of hoop iron or flat iron. For heavy wiring or for lasting and durable job, one has to make two wrought iron clamps. A tapped hole is made at one end of each clamp with a set-screw fitted there so that this end may be screwed to the beam. This is shown in fig. 121 (a).
Spacing between Wires in Cleat Wiring:
The spacing between wires drawn through the cleats depends upon (1) line voltage, and (2) type of circuit. What is ‘type of circuit’ will be clear from table no. 15.
Installation of Cleat Wiring:
Work is first started from the ceiling rose or from the lamp bracket at the farthest point of the load circuit. At this point a round wooden block with two holes drilled on it for taking out the wire leads is either screwed to a wooden plug or fixed with the beam as shown in fig. 122. This figure shows that, on the surface of the block a screw is set into a hole at the centre between two wires.
With this screw the block is fixed on the wooden plug. In case of a point with a bracket the length of wires kept outside the block must be somewhat in excess of that required for just passing through the bracket. But for a ceiling rose excess lengths of wires are not necessary—the ceiling rose is just set on a wooden block and the two wires are finally screwed to the terminals of the ceiling rose. Later, the wires are kept taut as they are drawn and fixed on the successive cleats for the progress of wiring.
The connection of a single lamp or a single fan is called a point: e.g. light point, fan point etc. In case of farthest point of the load circuit the neutral wire goes direct into a bracket or a ceiling rose and the live wire through a switch. But if there be a point mid-way of the circuit, a junction box has to be fixed there and connections are made through this box.
ADVERTISEMENTS:
The junction box should be made of wood or some-other good insulating material. From this box, with the help of porcelain or plastic connectors, live line is drawn up to switch terminal while neutral line is drawn up to ceiling rose for connection.
For the purpose of taking a connection or for jointing the wires, junction cut-out or line cut-out must not be used in any part of a wiring system. Jointing is made with the help of connectors inside a junction box. According to wiring regulation no other method of jointing wire to wire is permitted other than fixing a wire the terminal screw of a fitting. ‘T-joint’ is essential for taking live wire to the switch terminal or neutral wire to the lamp terminal. That is why a pair of connectors is to be used.
At the time of installation of a cleat wiring the point where a junction box is to be fixed, an oblong or rectangular wooden block is screwed on a wooden plug there and two connectors are placed inside that block. Suitable holes are drilled on at the sides of the block for the purpose of inserting or taking out wires. A wire is then drawn into the box through a hole, and its lead is tightly screwed to a connector.
Wall Tube or Pipe:
This tube is usually set near the ceiling corner. The space within the pipe should be sufficient to accommodate with comfortable inter-space the maximum number of wires to be drawn through it. With too many number of wires more than one tube may be necessary.
In that case pipes are set together at one place side by side. It has already been mentioned that such a tube may be made of porcelain or metal. Among metals lead, iron or steel is used. Steel pipe is also called steel conduit. The pipe is set inside the wall by means of cement. If conduit is used, its two rough ends are properly filed and two bushes made of hard wood or ebonite are fitted at these ends. This eliminates the possibility of damage of the insulation of wires when drawn through the pipes.
In case of a.c. wiring all the wires must be drawn through the same metal conduit. This is so essential that again and again this is mentioned for emphasis. Where wires are drawn outside from a room, the outer end of the pipe should be a bit more widened. Also this end should have a downward bend so that rain water or water from other sources may not get inside the pipe along the wires.
One can get a brief idea about arrangements of wires in a cleat wiring system from fig. 125. When one wire is drawn over or under another wire in a cross-wise manner, at least 1.27 cm (1/2″) spacing must be there between two such wires.
Drawing of Wires through Floors:
If the wires are to be drawn through a hole made in the floor, these must be drawn through a conduit pipe up to a height of 1.5 m (5 ft) above the floor level, and the lower end of the conduit should be flush with the ceiling below. As usual two ends of the conduit must be fitted with insulating bushes.
Board for Lamps and Fans:
If the board on which the switches, plugs etc. of a room remain fixed is made of wood, it should be a hinged box. This is known as double board. The bottom of this box remains screwed to wooden plug grouted in the wall. Switches, fan regulators etc., are fixed on the lid of the box and the connecting wires are placed inside the box. Holes are drilled at the sides of the box for leading wires to and from the board. The use of such boards facilitate the location of fault in the circuit.