IEC 60691:2015

Overview

IEC 60691:2015 (Edition 4.1 consolidated) - "Thermal-links - Requirements and application guide" - is an international standard from IEC that specifies uniform requirements, test methods and application guidance for non-resettable thermal-links used to protect electrical appliances, electronic equipment and their components against excessive temperatures under abnormal conditions. The standard principally applies to thermal-links intended for indoor use, with rated voltage up to 690 V a.c. or d.c. and rated current up to 63 A. It excludes extreme environments (corrosive or explosive atmospheres) and circuits outside the 45–62 Hz a.c. frequency range.

Key topics and technical requirements

• Scope and applicability: Indoor equipment protection; simple forms (melting strips/wires) allowed if expelled molten material cannot create hazard, especially for hand‑held or portable devices. Annex H covers packaged assemblies (thermal‑links in housings with terminals/leads).
• Electrical limits: Rated voltage ≤ 690 V, rated current ≤ 63 A; dielectric strength and insulation resistance test schedules defined.
• Temperature classification and tests: Holding temperature (Th), rated functioning temperature (Tf), maximum temperature limits and ageing/conditioning procedures (including conductive heat ageing options).
• Interrupting and overload performance: Defined interrupting current tests, transient overload and limited short‑circuit tests; the starting temperature for interrupt current testing was revised in this edition.
• Mechanical and constructional requirements: Lead secureness tests (tensile, thrust, bending/twist), contact and terminal requirements, creepage/clearance minimums.
• Resistance to tracking: Proof Tracking Index (PTI) minimum increased to 175 (previously 120).
• Marking and documentation: Requirements for marking, packaging labels and manufacturer documentation; corrigendum (Aug 2016) and Amendment 1 (2019) clarifications included.
• Manufacturer validation: Mandated validation programme and specific normative annexes (A–H) giving application guidance and additional tests (seal ageing, identification, packaged assemblies).

Applications and practical value

• Protects motors, transformers, heaters, consumer appliances, and electronic equipment from hazardous overheating under fault or abnormal conditions.
• Useful when designing thermal protection features where a single‑use thermal device is required to interrupt a circuit at a defined temperature.
• Supports component selection, design validation and compliance testing for safety engineers, product designers, and quality managers.

Who should use this standard

• Appliance and equipment manufacturers
• Component designers and thermal protection product suppliers
• Test laboratories and conformity assessment bodies
• Safety engineers specifying over‑temperature protection and compliance teams preparing technical files

Related standards

• The edition is harmonized with US practice and cites the basis of harmonization as UL 1020 (fifth edition, withdrawn 2003). Users should consult other national or regional safety standards as required for complete product compliance.

Keywords: thermal protection of equipment, thermal-links, thermal-link packaged assemblies, PTI, interrupting current, holding temperature.