Household and similar electrical appliances - Safety - Part 2-21: Particular requirements for storage water heaters
1Key Takeaways
Household and similar electrical appliances-Safety- Part2-21:Particular requirements for storage water heaters The standard, published by the International Electrotechnical Commission (IEC), provides specific safety requirements for storage water heaters. It covers general testing conditions, markings, protect…
2Expert Interpretation
An in-depth interpretation of the IEC 60335-2-21:2022 international safety standard for storage-type electric water heaters, covering technical revisions, testing requirements, safety precautions, and national variations, provides professional guidance for water heater manufacturers and testing agencies.
IEC 60335-2-21:2022 Standard Overview and Technical Evolution
The seventh edition of IEC 60335-2-21:2022, published by the International Electrotechnical Commission, is a specialized technical specification for the safety requirements of storage-type electric water heaters. This standard, supplementing the general safety requirements of IEC 60335-1, provides detailed safety provisions specifically addressing the unique risks of storage-type water heaters. This revision cancels the 2012 sixth edition and the 2018 revised edition, constituting a comprehensive technical overhaul.
Analysis of major technical changes
The 2022 version of the standard has undergone a number of important technical changes compared to the previous version: First, the standard text is fully aligned with IEC 60335-1:2020; second, a number of annotated contents have been converted into normative texts, involving clauses 1, 5.2, 15.3, 19.1-19.4, 22.47, 22.104, 22.110 and the introduction to Appendix AA; in addition, the restrictions on the use of appliance input sockets have been updated (Clause 25.1).
| Technical Change Project | 2012+AMD1:2018 Edition | 2022 Edition | Impact Analysis |
|---|---|---|---|
| Standard Alignment | Based on IEC 60335-1:2010 | Fully aligned with IEC 60335-1:2020 | Stricter technical requirements |
| Annotation conversion | Informative annotation | Normative requirements | Strengthened legal binding force |
| Input socket restrictions | General requirements | Specific restrictions | Clearer design constraints |
Scope of application and product definition
This standard applies to storage-type electric water heaters with a rated voltage not exceeding 250 V single-phase appliances and 480 V other appliances, including DC-powered and battery-powered appliances. The scope of application is extended to appliances that are not for normal household use but may pose a danger to the public, such as appliances used by non-professionals in shops, light industry, and on farms.
Application Case: For immersion heating units, the standard specifically specifies additional requirements for retrofitting into heat-exchange closed water heaters; see Appendix AA for details. Australia, the Netherlands, and New Zealand have additional restrictions for this type of product, requiring that the heating unit be tested and verified with the water tank model and brand listed in the instruction manual.
Detailed Explanation of Key Safety Requirements
Electrical Safety Protection
Chapters 8-17 of the standard detail electrical safety requirements, including protection of live parts, starting characteristics, power input, heating tests, leakage current, and electrical strength. Particular emphasis is placed on leakage current testing requirements at operating temperature; additional leakage current testing requirements apply to China.
Mechanical and Structural Safety
Chapters 20-22 specify stability, mechanical strength, and structural requirements. For closed water heaters, a pressure relief device is required. South Africa requires the device to operate before the water temperature reaches 99°C, and the UK requires it to operate before 100°C.
| Safety device type | Actuation temperature requirement | Applicable countries | Pressure requirements |
|---|---|---|---|
| Pressure and temperature sensitive relief device | Actuation before 99°C | South Africa | Inlet pressure 2MPa |
| Actuated before 100°C | UK | - | |
| Thermal circuit breaker | Single-pole disconnect | Japan (single-phase) | - |
| Thermal circuit breaker | All-pole disconnect | France | - |
Comparison of national requirements
The standard lists in detail the differences in special requirements of different countries, reflecting the technical preferences and regulatory traditions for water heater safety in different regions.
| Country/Region | Special Requirements | Technical Parameters | Implementation Impact |
|---|---|---|---|
| Japan, Norway | Maximum Water Temperature Limit | 99°C | Energy Efficiency Design Adjustment |
| South Africa | High Temperature Water Heater Pressure Requirements | 130°C Only Rated pressure ≥ 0.4 MPa | Higher structural strength requirements |
| Denmark, Finland, Norway, Sweden | Minimum rated pressure | 1.0 MPa | Stricter material requirements |
| Australia, New Zealand, South Africa | Additional marking requirements | Clause 7.1 | Complex labeling design |
Test Methods and Evaluation Criteria
Temperature Test Requirements
The standard specifies detailed temperature test methods, including surface temperature measurement probes (Figure 102) and examples of thermocouple locations (Figure 103). Table 101 specifies the maximum temperature rise limits for externally accessible surfaces under normal operating conditions.
Software Evaluation Requirements
Appendix R specifies normative requirements for software evaluation, reflecting safety considerations in the context of the intelligentization of modern home appliances. For smart water heaters with control software, a rigorous software security assessment is required.
Implementation Recommendations and Compliance Strategies
Design Phase Considerations
Manufacturers should fully consider the national requirements of target markets during the initial stages of product design. It is recommended to adopt the highest compliance standard design principle to ensure that products meet the most stringent market requirements and avoid the increased costs associated with subsequent design changes.
Testing and Verification Strategy
Establish a comprehensive testing and verification plan, focusing specifically on performance testing of thermal protection devices, leakage current testing, and structural strength testing. For products exported to multiple countries, it is recommended to plan a differentiated test matrix.
Document and Labeling Management
Prepare markings and instructions in strict accordance with the requirements of Chapter 7 to ensure that the specific marking requirements of different national markets are met. It is recommended to establish a multi-language and multi-version document management system. Compliance Case Study: An international water heater manufacturer successfully implemented a single product platform to meet the needs of major global markets by establishing a database of standard differences. This enabled them to meet the specific requirements of different countries through simple software configuration and minor component adjustments, significantly reducing compliance costs. Standard Development Trends and Outlook: With the advancement of smart home and IoT technologies, future standards for storage-type electric water heaters may evolve in the following directions: enhancing cybersecurity requirements, improving remote control security specifications, and strengthening the integration of energy efficiency and safety considerations. Manufacturers should closely monitor technical developments within IEC TC 61 and proactively plan for the next generation of product technologies. The Committee recommends that countries adopt the contents of this publication within 12-36 months of publication. Manufacturers should fully utilize this transition period to complete product upgrades and build testing capabilities to ensure a smooth transition to the new standard requirements.