Key Updates in Edition 4 (UL 62368‑1)
1. Removal of Legacy Component Acceptance (Clause 4.1.1)
The standard no longer allows components certified under IEC 60950‑1 or IEC 60065 to be used without re-evaluation.
This means all components and subassemblies must now be assessed against the requirements of IEC/UL 62368‑1, potentially requiring retesting or redesign.
2. Expanded and Clarified Terminology and Scope
Definitions—including those for audio amplifiers, loudspeaker drivers, liquid cooling systems, and battery-related terms—have been refined or added to clarify applicability to modern equipment types.
3. Battery Safety Enhancements (Annex M)
Annex M includes more detailed and broader :
Now applies to all types of secondary lithium batteries, whether portable or stationary.
More rigorous requirements for charging, protection circuitry, and fire enclosures.
4. Fire Protection & Ignition Source Clarifications
New rules and figures help clarify fire enclosure requirements, particularly for top, bottom, and side openings.
For loudspeaker drivers and assemblies, a specific provision now allows them to not require fire enclosures—offering design relief without compromising safety.
5. Liquid-Filled Components and Cooling Systems
Significant updates relate to liquid-filled and liquid-cooled components—especially modular systems exceeding 1 liter—reflecting the rise of direct liquid cooling in high-performance/data‑center equipment.
6. External Circuits & Surge Protection
A new table detailing requirements for external circuits, including surge protection in line with IEC 61000‑4‑5 (surge standard), relevant to network and communication equipment.
7. Terminology & Editorial Clarifications
Wording updates—such as replacing “may” with “can” or “shall”—help clarify whether provisions are optional or mandatory.
Additional refinements cover tool access, electronic measurement practices, overvoltage categories (including DC systems), and improved instructions across various clauses and annexes.
8. Thermal & Burn Hazard Enhancements
Touch-temperature limits for TS1 (touch-safe zone) are more stringent, especially for wearable devices like smartwatches—ensuring safety under normal, abnormal, and single-fault conditions.
Wireless power transmitter testing (Clause 9.6): now includes a defined test (Part A and B) to ensure foreign metallic objects don’t exceed temperature thresholds, and stipulates that the transmitter’s surface temperature must remain below TS2 limits.
9. Overvoltage Categories for DC Systems
Overvoltage categories are now explicitly defined for DC power distribution systems, extending application of insulation requirements to all systems powered beyond just AC mains.
10. Reworked Annexes & Testing Clarifications
Annex E (test conditions for audio amplifiers) was comprehensively overhauled for better applicability to modern designs without adding new burdens.
Several annexes (e.g., G.15 and others) have updated test methods, compliance criteria, and technical figures to support accurate, consistent implementation.
Summary Table: What’s New in Edition 4
| Area | What’s Changed |
|---|---|
| Legacy Components | No longer accepted under old standards → now re-evaluate |
| Terminology & Scope | Clarified definitions (amplifiers, batteries, cooling, etc.) |
| Battery Safety (Annex M) | Broader scope and stricter requirements for lithium systems |
| Fire Protection | New enclosure rules and relief for loudspeaker assemblies |
| Liquid Cooling Systems | Enhanced provisions for modular, > 1 L systems |
| External Circuits | Surge protection tables for communication equipment |
| Thermal/Burn Hazards | Lower skin-contact temps, new WPT testing protocol |
| Overvoltage Categories | Now includes DC power distribution systems |
| Annexes & Tests | Revisions for audio, LFC, and insulation testing clarity |
What This Means for Manufacturers & Designers
Retest or re-certify components previously accepted under older safety standards.
Pay close attention to battery system compliance, especially for lithium-based energy storage.
Review fire-protection designs and test plans—audio systems and loudspeakers may now avoid enclosures under specific conditions.
For equipment using liquid cooling or wireless power, ensure thermal hazards are appropriately addressed via updated testing.
Update documentation and measurement procedures to align with revised terminology and measurement requirements.
Watch the adoption timeline—UL’s Edition 4 is expected to be enforced from mid-to-late 2025, notably around July 31, 2025, across North America and EU market
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