Page 100 - Electrician - TT (Volume 1)

ELECTRICIAN - CITS

It is a simple system and cheapest method of wiring. Mainly used for temporary wiring purpose. It is installed 1.5
metres above the ground level. Single core VIR or PVC insulated cables are used. Porcelain or wooden cleats
of two way , three way, four way etc are available. For fixing cleats on wall wooden plugs (gutties) and wood
screws are used. For avoiding sag in the cable , cleats are provided every 60.cm distance. In branch circuit the
distance between cable should be 2.5 cm. In sub main circuit the distance between cable should be 4 cm. The
cables are prevented to avoid coming in contact with other conductors , gas or water mains. Cross - cleated
cables should be separated by an insulating bridge piece which should at least maintain a distance of 1.3 cm
between the cable. In this wiring , joints are to be maid in wooden or other insulating material junction boxes with
porcelain connectors inside. Two wires should never be placed in the same grove of the cleats. Life of this wiring
is approximate 5 – years. This wiring is not used in damp walls or ceiling. Wiring must be enclosed in conduit if
the wire is passing through a wall or a floor.
Advantage
The wiring can be completed very fast.

Faults can easily be located
Disadvantage
It collects dust over the wire
There is no protection from mechanical injury
Casing and capping

Wooden casing and capping wiring
This wiring is suitable for low voltage domestic installation. In this system of wiring vulcanised rubber-insulated
cables or PVC insulated cables are used. It is not suitable in damp places. The casing and capping should be
of well seasoned teak wood or any other hard wood . Before the installation of casing capping it should be well
varnished from all sides with shellac varnish. The casing is fixed by means of flat head counter sunk wooden
screws to the wooden plugs(gutties) on wall or ceiling. The distance between two casing fixing wooden screws is
not exceeding 90 cm for sizes up to 64 mm and not exceeding 60 cm for sizes above 64mm casing . The capping
is fixed on casing by means of round head brass screws at a distance not exceeding 15 cm cross-wise for all
sizes up to 64 mm casing capping. For cap sizes above 64.mm the screws are fixed at an interval of 22.5.cm
cross-wise on capping. The life of this wiring is approx. 20 years. While laying out the casing try to avoid corners
and crossing of cables as far as possible .If this cannot be avoided ,then use wooden corners and bridge pieces.
This type of wiring is commonly used in residential and office buildings. The selection of casing and capping size
depends up on the number of wires drawn through the groves. Any number of wires of the same polarity , either
phase or neutral , may be laid in the same grove. The opposite polarity of wires should never be laid in one grove.
In this type of wiring, there is a clearance of 0.32 cm thick space between the wall or ceiling and the casing by
means of porcelain insulators .
Advantage
• Mechanical protection is good
Disadvantage

• There is great risk of fire in this system
• It is difficult to find fault
• If it is not damp proof it absorbs moisture easily
• Its erection is not very simple and requires more time

• Skilled labour is required

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CITS : Power - Electrician & Wireman - Lesson 20-25 CITS : Power - Electrician & Wireman - Lesson 20-25