IEC 60335-2-21:2022

Overview - IEC 60335-2-21:2022 (Storage Water Heaters Safety)

IEC 60335-2-21:2022 is the seventh edition of the IEC safety standard for electric storage water heaters used in households and similar environments. It covers appliances intended to heat water below boiling temperature with rated voltages up to 250 V for single‑phase and 480 V for other appliances (including DC and battery‑operated units). This part 2 document supplements IEC 60335-1 and defines particular safety requirements, test conditions and constructional provisions specific to storage water heaters and certain retrofit immersion heater units (see Annex AA).

Key technical topics and requirements

• Scope and exclusions: Applies to domestic storage water heaters and some non‑household appliances used by laypersons. It excludes boiling/instantaneous water heaters, vending/commercial dispensers, industrial appliances and equipment for special atmospheres.
• Harmonization with IEC 60335-1: Text aligned with IEC 60335-1:2020; Part 2 is intended to be used in conjunction with the latest applicable Part 1 edition.
• Safety and construction: Requirements on construction, insulation, clearances, earthing, internal wiring, and mechanical strength to prevent electric shock, fire and mechanical hazards.
• Thermal protection: Mandatory protections such as thermal cut‑outs and temperature limits; requirements for pressure‑relief devices on closed water heaters (national variations apply).
• Leakage current and dielectric strength: Tests at operating temperature and additional leakage current provisions where applicable.
• Moisture, endurance and abnormal operation tests: Procedures to ensure reliability under expected service conditions.
• Immersion heater retrofit (Annex AA): Normative additional requirements for immersion heater units intended for retrofitting into heat‑exchange closed water heaters.
• Notable changes in 2022 edition:
  • Alignment with IEC 60335-1:2020
  • Several notes converted to normative requirements
  • Updated restriction on appliance inlet use (Clause 25.1)

Practical applications - who uses IEC 60335-2-21

• Manufacturers and OEMs designing and producing electric storage water heaters
• Test laboratories and certification bodies performing type and routine safety tests
• Compliance managers and regulatory authorities ensuring products meet international safety requirements
• Installers and specifiers who need to understand installation and marking requirements
• Product designers and safety engineers addressing thermal, mechanical and electrical hazards

Related standards and considerations

• Must be used together with IEC 60335-1 (general safety requirements for household appliances)
• Excludes appliances covered by IEC 60335-2-15 (boiling water), IEC 60335-2-35 (instantaneous heaters) and IEC 60335-2-75 (vending machines)
• National regulations (installation codes, health and labour authorities) and country‑specific deviations noted in the standard should be considered during design and certification.

Keywords: IEC 60335-2-21, storage water heaters safety, electric storage water heaters, household appliance standard, immersion heater retrofit, IEC 60335-1.