Wiring: Types, Joints and Installation
Overview
Wiring systems form the backbone of electrical installations. For ITI Electrician Semester 3 (NCVT), candidates must understand different wiring types (cleat, casing-capping, conduit, batten), types of joints (married, britannia, tee), and installation rules as per IS 732 and IE Rules 1956. This chapter covers materials, advantages, disadvantages, and practical installation guidelines that appear repeatedly in NCVT theory and practical papers.
Typed Notes
Types of Wiring Systems
1. Cleat Wiring: PVC/VIR cables supported on porcelain cleats fixed to walls. Cheapest, temporary, easy to inspect but not aesthetically pleasing. 2. Batten Wiring: TRS/PVC cables fixed on wooden battens using tinned brass clips. Suitable for dry indoor locations. 3. Casing-Capping: Cables run inside a wooden casing covered by capping. Good appearance but not suitable for damp/humid areas. 4. Conduit Wiring: Cables drawn through GI or PVC conduit pipes. GI conduit is used in factories; PVC conduit in domestic/commercial buildings. It is the safest and most expensive system.
Types of Electrical Joints
Proper joints ensure low resistance and mechanical strength. 1. Married (Pig-tail) Joint: Used for joining thin wires (below 10 sq mm). Conductors are twisted together — simple and quick. 2. Britannia Joint: Used for thick conductors (above 10 sq mm) for straight-through connection. A binding wire is wrapped tightly around the overlapping conductors. 3. Tee (T) Joint: Used to take a branch connection from a main conductor. Also called a tap joint. All joints must be soldered and insulated with PVC tape to prevent short circuits and corrosion. Joints must NOT be left inside conduit pipes.
Installation Rules and Standards
Key rules as per IS 732 and IE Rules 1956: (a) Minimum height of switch board from floor: 1.25 metres. (b) Minimum height of ceiling fan from floor: 2.4 metres. (c) Earth wire colour: Green or Green-Yellow. (d) Phase wire colour: Red (R), Yellow (Y), Blue (B). (e) Neutral wire colour: Black. (f) Minimum conductor size for domestic wiring: 1.5 sq mm. (g) Spacing between two clips in batten wiring: 10 cm for horizontal runs. (h) All metallic conduits must be earthed. (i) Looping system (not joint system) is preferred in modern wiring to avoid joints in walls.
Conduit Wiring — GI vs PVC
GI (Galvanised Iron) Conduit: Used in factories, workshops, and outdoor locations. Provides excellent mechanical protection. Must be earthed compulsorily. Joined using couplers and locknuts. Bending done with conduit bending machine. PVC Conduit: Lightweight, rust-proof, cheaper than GI, used in domestic and commercial wiring. Not suitable for very high temperature areas. Bending done using a spring bender or hot sand method. Conduit fill rule: Total cable cross-section area should not exceed 40% of conduit internal cross-section area. Standard conduit sizes: 20 mm, 25 mm, 32 mm, 38 mm diameter.
Topics & Sub-topics
Har topic ke saath sub-topics aur example — chapter ka complete coverage.
01Wiring Systems Types
- Cleat, casing-capping (old)
- Batten wiring (TRC caps)
- Conduit — surface / concealed (modern)
Aajkal concealed conduit wiring — plaster ke andar pipe, switch box par switch.
02Electrical Joints
- Straight twist, married joint
- T-joint, western union
- Soldering + insulation tape
Western union joint overhead service wire ke liye — strong aur neat.
03Installation Rules (IE)
- Height of switch board 1.3-1.5 m
- Earth wire compulsory
- Independent control per room
Bathroom ke switch board bahar — safety ke liye.
04Distribution Board (DB)
- Main MCB + RCBO/RCCB
- Sub-circuits: light, power separate
- Labelling of circuits
Har circuit ka MCB alag — galti ek circuit mein ho to poora ghar andhera nahi.
Key Concepts
Revision ke liye ek nazar — exam se pehle yahi padhna hai.
- 01Cleat wiring uses porcelain/PVC cleats and is the cheapest, temporary wiring system — not suitable for permanent installations.
- 02Casing-capping wiring uses a wooden channel (casing) with a lid (capping) and is suitable for dry places only; not used in damp locations.
- 03Conduit wiring (GI or PVC) is the safest, most durable wiring system — GI conduit is used in factories and workshops for mechanical protection.
- 04Britannia joint is used for straight-through joining of thick conductors (above 10 sq mm); married joint is used for thin conductors (below 10 sq mm).
- 05As per IE Rule 51, all wiring must be done with ISI-marked cables and minimum conductor size for domestic wiring is 1.5 sq mm.
Questions & Solutions
Pehle khud try karo — phir solution kholo. Yahi tariqa topper banata hai.
What is the difference between a Married joint and a Britannia joint? Where is each used?
Why is GI conduit wiring considered the safest wiring system? List two locations where it is preferred.
State any four colour codes for wiring as per IS 732 and their significance.
What is the looping system of wiring? Why is it preferred over the joint system?
List the installation rules for switchboard height, ceiling fan height, and conduit fill percentage as per standards.
Wiring types include cleat (cheapest/temporary), batten, casing-capping (dry places only), and conduit (safest/most expensive). Joints — married for thin wires, britannia for thick wires, tee for branch connections — must be soldered and insulated. Installation follows IS 732 and IE Rules 1956: correct wire colours, minimum heights, earthing of conduits, and looping system preferred over joint system in modern installations.
Chapter-end quiz
4 MCQsOption tap karo — turant pata chalega sahi ya galat, explanation ke saath.
Q1.Which type of wiring is MOST suitable for a factory workshop requiring maximum mechanical protection?
Q2.A Britannia joint is used for conductors of cross-section area:
Q3.As per IS 732, what is the colour of the Earth (protective) conductor?
Q4.What is the maximum percentage of conduit internal area that cables should occupy as per the conduit fill rule?
Mark karo — dashboard par progress dikhega.