SECTION 4 GUIDE FOR PREPARATION OF DIAGRAMS,

CHARTS, TABLES AND MARKING

FOREWORD
Various types of diagrams and charts are required to be prepared during the planning and execution stages
of an electrical installation work. It is therefore necessary to define the different types of diagrams, charts
and tables, their purposes and format and the guiding principles for preparing them for the sake of
uniformity.
This Section 4 of the Code covers general guidelines on the subject. A list of relevant Indian Standards is
given at Annex A.
The guidelines for marking of conductors given in 3.6. Table 1 are in line with the guidelines accepted
internationally on such matters. They provide for a common basis for understanding and identifying
conductors and apparatus terminals, but more important, ensure safety to operating, maintenance personnel.
1 SCOPE
This Indian Standard (Part 1/Sec 4) of the Code covers guidelines for preparation of diagrams, charts and tables in
electrotechnology and for marking of conductors.

2 REFERENCES
The standards listed in Annex A contain provisions, which through reference in this text,
constitute provisions of this standard. At the time of publication, the editions indicated
were valid. All standards are subject to revision, and parties to agreements based on this
standard are encouraged to investigate the possibility of applying the most recent editions
of the standards.
3 PREPARATION OF DIAGRAMS, CHARTS AND TABLES
3.0 General
3.0.1 Diagram
A diagram may show the manner in which the various parts of a network, installation, group of apparatus
or items of an apparatus are interrelated and or interconnected.
3.0.2 Chart
A chart may show the interrelation between:
a) different operations,
b) operations and time,
c) operations and physical quantities, and
d) states of several items.
3.0.3 Table
A table replaces or supplements a diagram or a chart.
3.1 Classification According to Purpose
The main classifications are:
a) Explanatory diagrams,
b) Explanatory charts or tables,
c) Wiring diagrams or wiring tables, and
d) Location diagrams or tables.
3.1.1 Explanatory Diagrams
Explanatory diagrams are intended to facilitate the study and understanding of the functioning of an
installation or equipment. Three types are defined below:
a) Block Diagram — Relatively simple diagram to facilitate the understanding of the principle of
operation. It is a diagram in which an installation or equipment together with its functional interrelationships
are represented by symbols, block symbols or pictures without necessarily showing all the connections.
b) Circuit Diagram — Explanatory diagram intended to facilitate the understanding of the functioning
in detail. It shows by symbols an installation or part of an installation and the electrical connections and
other links concerned with its operation.
c) Equivalent Circuit Diagram — Special type of circuit diagram for the analysis and calculation of
circuit characteristics.
3.1.2 Explanatory Charts or Tables
Explanatory charts or tables are intended to facilitate the study of diagrams and to give additional
information. Two examples are given below:
a) Sequence Chart or Table — Gives the successive operation in a specified order.
b) Time Sequence Chart or Table — Is one which in addition takes account of the time intervals
between successive operations.
3.1.3 Wiring Diagrams or Wiring Tables
Wiring diagrams are intended to guide the making and checking of the connection of an installation or
equipment. For an equipment, they show the internal or external connections or both. The diagrams may
sometimes show the layout of the different parts and accessories, such as terminal blocks and the wiring
between them.
3.1.3.1 Unit wiring diagram
Diagram is representing all connections within a unit of an installation.
3.1.3.2 Interconnection diagram
Diagram representing the connections between the different units of an installation.
3.1.3.3 Terminal diagram
Diagram showing the terminals and the internal and/or external conductors connected to them.
NOTE — Any of the wiring diagram may be replaced or supplemented by a table.
3.1.4 Location Diagrams or Tables
A location diagram or table contains detailed information about the location of parts of the equipment, for
example, terminal blocks, plug-in units, sub-assemblies, modules, etc. It shows the item designations used
in related diagrams and tables.
NOTES:
1 A location diagram need not necessarily be to scale.
2 Several types of diagrams may be combined into a single diagram, forming a mixed diagram. The same
drawing may form both an explanatory and wiring diagram.
3.2 Classification According to Method of Representation
3.2.1 The method of representation is distinguished by:
a) the number of conductors, devices or elements represented by a single symbol (see 3.2.1.1);
b) the arrangement of the symbols representing the elements or parts of an item of apparatus (for
example, detached or assembled) (see 3.2.1.2); and
c) the placing of the symbols to correspond with the topographical layout of the devices (see 3.2.1.3).
3.2.1.1 Number of conductors
According to the number of conductors, devices or elements represented by a single symbol, the two
methods of representation as given below may be distinguished.
a) Single-line Representation — Two or more conductors are represented by a single line.
In particular, a single line may represent:
1) circuits of a multi-phase system,
2) circuits which have a similar electrical function,
3) circuits or conductors which belong to the same signal path,
4) circuits which follow the same physical route, and
5) conductor symbols which would follow the same route on the diagram.
Several similar items of apparatus may accordingly be represented by a single symbol.
b) Multi-line Representation — Each conductor is represented by an individual line.
3.2.1.2 Arrangement of symbols
According to the arrangement of the symbols representing the elements or parts of an item of apparatus on
the diagram, the methods of representation are given below:
a) Assembled Representation — The symbols for the different parts of an item of apparatus or of an
installation or equipment are drawn in close proximity on the diagram.
b) Semi-assembled Representation — The symbols for the different parts of an item of apparatus or of
an installation are separated and arranged in such a way that the symbols for mechanical linkages between
the parts which work together may be drawn easily.
c) Detached Representation — The symbols for the different parts of an item of apparatus or of an
installation are separated and arranged in such a way that the circuits may easily be followed.
3.2.1.3 Topographical representation
The positions of the symbols on the diagram correspond wholly or partly to the topographical (physical)
location of items represented.
The following are examples where topographical representation may be used.
a) Wiring diagrams,
b) Architectural diagrams, and
c) Network diagrams.
NOTE — Several of these methods of representation may be used on the same diagram.
3.3 Item Designation
3.3.1 Item is a term used for component equipment, plant, unit, etc, which is represented by a graphical
symbol on a diagram. The item designation is shown at an appropriate place near the graphical symbol of
the item. This designation correlates the item on different diagrams, parts list, circuit descriptions and in
the equipment.
3.3.2 An item designation may be used for general or special purposes depending on the kind of information
required. Guidelines on assignment of item designation, groups together with standard letter codes for the
same are covered in IS 8270 (Part 2).
3.4 General Rules for Diagrams
3.4.1 Paper sizes for drawings shall preferably be according to the international A-series (see IS 1064).
The choice of drawing sizes should be decided after taking into account the necessary factors enumerated
in 2.2 of IS 8270 (Part 2).
3.4.2 In IS 2032 series, different kinds of symbols as well as symbols of different forms are shown. All the
possible examples are also not covered there. Any symbol may be composed using the guidance from
relevant Part of IS 2032 and Part 1/Section 3 of the Code. The basic rules for the choice of symbols shall
be:
a) to use the simplest form of symbol adequate for the particular purpose,
b) to use a preferred form wherever possible, and
c) to use the chosen form consistently throughout the same set of documentation.
3.4.3 Specific guidelines on the application of IS 2032 (All parts) from the point of view of choice of
alternative symbols, symbol sizes, line thickness, orientation of symbols and methods of indicating symbol
location are covered in IS 8270 (Part 3).
3.5 Interconnection Diagrams and Tables
3.5.1 Interconnection diagrams and tables provide information on the external electrical connections
between equipment in an installation. They are used as an aid in the fabrication of wiring and for
maintenance purposes. Information on the internal connections of units are normally not provided but
references to the appropriate circuit diagram [see IS 8270 (Part 4)] may be provided.
3.5.2 The diagrams may employ single or multiple representation and may be combined with or replaced
by tables, provided clarity is maintained. Tables are recommended when the number of interconnections is
large.
3.5.3 Guidance on layout, identification and types of interconnection diagrams and tables are given in IS
8270 (Part 5).
3.6 Marking and Arrangement of Conductors
3.6.0 General
3.6.0.1 The purpose of marking is to provide a means whereby conductors can be identified in a circuit and
also after they have been detached from the terminals to which they are connected. Main marking is a
system of marking characterizing each conductor or group of conductors irrespective of their electrical
function. Supplementary marking is used as supplement to a main marking based on the electrical function
of each conductor or group of conductors.
3.6.0.2 The various methods of marking applicable to electrical installations and the equipment which form
part of them are covered in IS 5578.
3.6.1 Identification of Insulated and Bare Conductors
For the purposes of this Code, the provisions of Table 1 shall apply for the general application of marking
conductors in installation. The rules also apply for marking conductors in assembles, equipment and
apparatus. Reference is also drawn to the provision contained in relevant Indian Standard.
3.6.2 Arrangement of Conductors
Bus-bars and main connections which are substantially in one plane shall be arranged in the order given in
either 3.6.2.1 or 3.6.2.2 according to the system. The relative order remains applicable even if any poles of
the system are omitted.
3.6.2.1 AC systems
The order of phase connection shall be red, yellow and blue:
a) When the run of the conductors is horizontal, the red shall be on the top or on the left or farthest away as
viewed from the front.
b) When the run of the conductors is vertical, the red shall be on the left or farthest away as viewed from
the front.
c) When the system has a neutral connection in the same place as the phase connections, the neutral
shall occupy an outer position.
d) Unless the neutral connection can be readily distinguished from the phase connections, the order
shall be red, yellow, blue and black.
3.6.2.2 DC systems
The arrangement shall be as follows:
a) When the run of the conductors is horizontal, the red shall be on the top or on the left or farthest away as
viewed from the front.
b) When the run of the conductors is vertical, the red shall be on the left or farthest away as viewed from
the front.
c) When the system is 3-wire with the conductors in the same place, the neutral shall occupy the
middle position.
 Table 1 Alphanumeric Notation, Graphical Symbols and Colours
(Clause 3.6.1)

Sl No. Designation of Conductors Identification by

^Alphanumeric Graphical Colour
Notation Symbol
(1) (3) (4) (5)
(2)
Phase 1 L1 Red
i) Supply ac system Phase 2 L2 Yellow
Phase 3 L3 Blue
Neutral N Black
Phase 1 U Red
Phase 2 V Yellow
ii) Apparatus ac system Phase 3 W Blue
Neutral N Black
Positive L+ + Red
iii) Supply dc system Negative L- - Blue
Midwire M Black
Phase L Red
iv) Supply dc system Neutral N Black
v) (single phase)
Protective conductor PE Green and Yellow
vi) Earth E No colour other than the
colour of the bare conductor.
If insulated, the colour for
insulation so chosen to avoid
those
Underlisted above for
consideration
vii) Noiseless (clean earth) TE
designation of other
viii) Frame or chassis MM —
conductors
—
ix) Equipotential terminal CC

ANNEX A
(Clause 2)
LIST OF INDIAN STANDARDS ON DIAGRAMS, CHARTS, TABLES AND MARKING
IS No. Title IS No. Title
Guide for the preparation of
1064 : 1980 Specification for paper standard sizes diagrams, charts and tables for
Graphical symbols used in 8270 electrotechnology:
2032 (Part 15) : electrotechnology: Part 15 (Part 1) : 1976 Definitions and classification
1976 Aircraft electrical symbols (Part 2) : 1976 Item designation
Electrical equipment used in medical (Part 3) : 1977 General requirements for diagrams
(Part 19) : 1977 practice (Part 4) : 1977 Circuit diagram
(Part 25) : 1980 Electrical installations in ships
Guide for marking of insulated (Part 5) : 1976 Interconnection diagrams and tables
5578 : 1984 conductors (Part 6) : 1983 Unit wiring diagrams and tables