BS 3456-3.21:1981

Foreword
Cooperating organizations
Specification
1 Scope
2 Definitions
3 General requirements
4 General conditions for the tests
5 Rating
6 Classification
7 Marking
8 Protection against electric shock
9 No requirement
10 Input and current
11 Heating
12 Operation under overload conditions
13 Electrical insulation and leakage current at
    operating temperature
14 Radio and television interference suppression
15 Moisture resistance
16 Insulation resistance and electric strength
17 Overload protection
18 No requirement
19 Abnormal operation
20 Stability and mechanical hazards
21 Mechanical strength
22 Construction
23 Internal wiring
24 Components
25 Supply connection and external flexible cables and
    cords
26 Terminals for external conductors
27 Provision for earthing
28 Screws and connections
29 Creepage distances, clearances and distances through
    insulation
30 Resistance to heat, fire and tracking
31 Resistance to rusting
32 Radiation, toxicity and similar hazards
Appendices
A Electronic circuits
B Measurement of creepage distances and clearances
C Classification of controls in accordance with the
    requirements of BS 3955 : Part 3 as type 1 or type 2
D Specification for flannelette material
Tables
1 No requirement
2 Permissible variations in rated input
3 Permissible temperature rises
4 No requirement
5 Test voltages
6 No requirement
7 No requirement
8 Permissible temperature rises under abnormal
    operation
9 Test force for screwed glands
10 No requirement
11 Size of flexible cord
12 Test figures for flexible cord pull and torque
13 No requirement
14 Conductor cross-sectional areas for which terminals
    shall be suitable
15 Dimensions of pillar type terminals
16 Dimensions of screw type terminals
17 Dimensions of stud type terminals
18 Axial pull on conductors
19 Torque values for screws and nuts
20 Creepage distances and clearances
Figures
1 Standard test finger
2 Test pin
3 No requirement
4 Diagram for leakage current measurement at operating
    temperature for single-phase connection of class II
    appliances
5 Diagram for leakage current measurement at operating
    temperature for single-phase connection of
    appliances other than those of class II
6 No requirement
7 No requirement
8 Diagram for electric strength test at operating
    temperature
9 No requirement
10 No requirement
11 No requirement
12 Impact-test apparatus
13 No requirement
14 Ball-pressure apparatus
15 Hot mandrel apparatus
16 Arrangement and dimensions of the electrodes for the
    tracking test
17 Apparatus for flexing test specified in 25.101
18 Schematic representation of cord anchorages

Safety requirements for heaters for heating water and the like. Includes aquarium heaters.