Domestic Wiring System

In this sub-unit, we will come to know the various important factors, which are to be taken into considerations, while selecting type of wiring system to be used.These factors are durability, safety, appearance, cost, accessibility and maintenance cost, etc. Apart from above, the environmental conditions, such as temperature,humidity, indoor or outdoor, direct sunlight and corrosive acid fumes, etc., are also be taken into consideration. The following are the types of internal wiring usually employed in houses and industries.

i. Cleat Wiring

The wooden plugs (gutties) are fixed in the wall at regular interval of 30 - 60 cm apart. This distance should not increase in any case; otherwise there will be risk of wire/cable touching the wall. The cables/wires are supported and gripped between the porcelain cleat approximately 10 mm above the wall. Cleats are made in two halves, the base, which is grooved to accommodate the wire and the cap is put over it

ii. Wooden Casing Capping Wiring

The casing is the base unit in which U shaped grooves are made usually two in number, into which wires are laid in such a way that the wires of opposite polarity are laid in different groove. The second part is “capping” which is a rectangular strip of same size as casing

Usually these are made from seasoned teakwood free from knots and other defects. All the sides of casing and capping should be well varnished with a good quality varnish. The size of the casing capping to be used depends upon the number and size of the wires to be accommodated. Nowadays, wooden casing capping are being replaced very fast by plastic made casing capping (Channel), as the cost of wood is too high as compared to plastic. Secondly the outer look is very good and does not require any maintenance.

iii. Tough Rubber Sheathed Wiring (TRS or CTS) or Batten Wiring

This wiring also known as batten wiring system, in which Tough Rubber sheathed or Cab Type sheathed wires are used. The batten is prepared from seasoned teakwood. The minimum thickness of batten should not be less than 13 mm. In domestic wiring normally used width is 13, 19, 25, 31, 44 and 50 mm and is suitable for 2, 3, 4, 5, 6 and 7 wires, respectively.Joint link clips are fixed on batten with the help of nails. Wooden gutties are fixed in the walls at an interval of 75 cm. The batten is fixed on wall with the help of wooden screws and gutties. The wires are fixed on batten by means of joint link clips, already fixed on batten. This method is mostly used for all ordinary residential and non-residential installation, being cheap in cost, quick installation, fault finding and repair, etc. But it has a great disadvantage that this wiring is unsuitable where it is exposed to direct sunlight and rainfall. It is suitable where acidic and alkalis firms are present.

iv. Lead Sheathed or metal wiring
This system of wiring is also similar to that of T.R.S or C.T.S sheathed wiring system as in previous case. Here the wires are replaced by lead sheathed or metal sheathed wires/cables. Rest of the procedure such as fixing of batten on wall, fixing of lead sheathed wire in joint clips, etc is also the same. As these wires are covered, with extra coating of lead, not exceeding 15-mm thickness, this type of wiring is suitable on places exposed to direct sunlight, rain and damp situation. This type of wiring gives fairly good-looking and comparatively longer life.

v. Conduit Wiring
As the name indicates “Conduit Wiring” mean the wires are enclosed in steel pipe known as “ Conduit.” When this conduit is coated with enamel is known as black conduit and when galvanized it is known as galvanised conduit, to protect the pipe from corrosion and insulation damage to wires. There are three types of conduit wiring mostly in use.

a) Concealed Wiring: In this wiring system, the conduits are embedded into the walls and ceiling, with the plaster at the time of construction. These conduits should be mechanically as well as electrically continuous and connected to earth wire at some suitable places. The P.V.C wires are drawn into the conduit, by means of steel wire not less than 18 S.W.G. Number of inspection boxes are provided, in order to facilitate the drawing of wires in the conduits. Nowadays,P.V.C. conduit pipe is also available in the market, which do not require any threading for jointing the pipe. The joints are made with special solution. This type of wiring is not suitable for damp situation.

b) Surface Conduit Wiring: In this wiring the conduits are fixed on the surface of wall and ceiling with the help of conduit saddles, wooden screw and gutties.In damp situation, the conduit can be spaced from walls by means of wooden spacers, below the conduit along its length at regular intervals. The wires are drawn in the conduit with the help of steel wire. Junction boxes are provided to facilitate the drawing of wires in the conduit. This system of wiring is commonly used for industrial wiring, especially in three-phase wiring. As the,fault finding and repair is quick, easy in wiring, cheap in cost but not suitable for domestic wiring, as it does not give fairly good outlook.

c) Flexible Conduit Wiring: This wiring is carried out to provide mechanical protection to cable between conduit and machine. Generally this wiring is not used for wiring purposes. It is generally used for connecting conduit with machine terminal box in case of motor wiring, energy meter and main switches.

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