UL 60950 vs UL 62368-1 — Migration Guide for IT Equipment Manufacturers

UL 60950-1 and its IEC twin IEC 60950-1 governed information-technology equipment safety for two decades. UL 62368-1 (IEC 62368-1) supersedes it. As of 20 December 2020, 60950-1 is fully withdrawn for new submissions in the major target markets — US, Canada, EU, and most aligned regions. Existing certifications were grandfathered with phased deadlines that have largely passed. If you are still designing to 60950-1 in 2026, you are designing for a market that no longer exists.

The change is not paint-by-numbers. 60950-1 was a prescriptive standard — it told you what creepage and clearance distances to use, what insulation thickness to apply, what marking text to print. 62368-1 is a hazard-based standard built on three pillars:

• Energy source classification — every energy source in the product (electrical, thermal, mechanical, radiated, chemical) is classified as Class 1, 2, or 3 based on the harm it can cause.
• Body part classification — who can contact the energy: ordinary person, instructed person, or skilled person.
• Safeguards — basic, supplementary, reinforced — designed and tested to reduce energy that reaches the body part.

What energy classes mean in practice

• ES1 — no sensation or pain. Below ~30Vrms AC, 60V DC, and below specified current limits. Touchable by ordinary persons.
• ES2 — painful but not injurious. 30–60Vrms AC, 60–120V DC range, with current limits. Accessible to instructed persons; ordinary persons need a basic safeguard.
• ES3 — injurious. Above ES2 limits. Requires reinforced or double safeguards before ordinary-person access.

"The shift from 'follow the table' to 'classify the source, classify the user, prove the safeguard' adds engineering hours up front, but it surfaces hazards that 60950-1's tables sometimes hid. We catch issues in design review now that we used to catch at certification." — Pioneer Horizon compliance manager

For a design team this means safety analysis starts at the schematic stage, not at the certification submission stage. The hazard analysis document becomes a deliverable, not an afterthought.

Insulation requirements look similar between the two standards at first glance — clearance, creepage, solid insulation, with comparable distance tables. The differences are subtle but material.

Creepage and clearance

62368-1 Annex S retains a table-based approach for mains-circuit creepage and clearance, with values largely consistent with 60950-1. For circuits below 420V peak (the common case for IT and audio/video), the practical numbers are unchanged. Where 62368-1 diverges is in Annex G, which allows determination of distances by impulse test instead of table — useful when your transformer has been characterised but doesn't quite hit the table value with margin.

Solid insulation

60950-1 specified solid insulation by thickness (typically 0.4mm minimum for reinforced). 62368-1 specifies it by either thickness or by an electric-strength test — so a thinner, properly tested insulation can qualify. This matters most for transformer designs and for opto-isolator selection (where the part datasheet must reference 62368-1 explicitly, not just 60950-1).

Pollution degree

The pollution degree definitions are aligned, but 62368-1 is more explicit about what conditions constitute PD2 vs PD3 inside a sealed enclosure. For outdoor or industrial-environment products, you may end up at PD3 where you used to claim PD2 — which increases creepage requirements meaningfully. Re-run the table for any product moving from 60950-1 to 62368-1 with a non-trivial outdoor or dusty use case.

Working voltage determination

• Peak working voltage is now the dominant parameter for clearance.
• RMS working voltage drives creepage.
• Both must be calculated for steady-state and for transient (impulse) conditions; the worst case sets the requirement.

The audit message: your old 60950-1 evaluation report numbers will not directly transfer. The safety engineer must re-derive working voltages, re-check distance tables under the new standard, and document the result. Plan for two to four engineer-weeks per product family for this re-derivation.

62368-1 changes how fire safety is evaluated. 60950-1 prescribed fire enclosures around components above certain power thresholds and required specific material flammability ratings. 62368-1 introduces the Potential Ignition Source (PIS) concept and asks you to engineer the enclosure of materials based on the ignition energy actually available.

Power source classes (PS1, PS2, PS3)

• PS1 — power source under 15W. No fire enclosure required for adjacent flammable materials.
• PS2 — 15–100W. Fire enclosure required; V-1 material acceptable.
• PS3 — above 100W. Reinforced fire-enclosure rules; typically V-0.

Identifying PIS components

A PIS is any component that, under fault conditions, may ignite. Resistors above defined dissipation, electrolytic capacitors above defined voltage/capacitance product, transformers, FETs in switching power stages, and certain connectors all need PIS analysis. The deliverable is a list of PIS components in the design with the safeguard for each — either limited fault energy (PS-class containment) or a fire enclosure.

Material certifications you'll be asked for

• PCB substrate — UL 94 V-0 with file number cited in the report.
• Plastic enclosures — UL 94 rating matching the PS class, with the minimum wall thickness tested and certified.
• Wire insulation — VW-1 or equivalent for any wire passing through a fire-relevant zone.
• Adhesives and labels in proximity to PIS components — flammability rating cited.

The submission expects the bill of materials to carry a UL or equivalent component file number for every safety-critical material. Missing certifications drive more re-submission cycles than any other single cause we've seen in the migration. Audit your BOM for component-level certifications early — not at submission.

For BOM-level material discipline that pairs cleanly with this, see RoHS-3 phthalate compliance.

The test programme under 62368-1 overlaps significantly with 60950-1 but adds and refines several tests, particularly around battery safety and stored energy.

Tests carried forward (with minor tweaks)

• Hi-pot (dielectric withstand) — same approach, voltages may differ based on the new working-voltage calculation.
• Leakage current — same approach; limits aligned with the body part / energy source matrix.
• Temperature rise — same approach; criteria expressed against ES/PS thresholds.
• Humidity preconditioning — typically 48 hours at 25°C / 93% RH, then hi-pot.
• Abnormal operation (single fault) — broader set of fault conditions to evaluate.

Tests new or significantly expanded

• Battery safety (Annex M) — much more explicit for lithium-ion. Short-circuit, overcharge, forced discharge, mechanical abuse for batteries above defined capacity. If your product contains a Li-ion cell, expect a separate Annex M evaluation that 60950-1 effectively delegated to other standards.
• Stored energy testing — capacitors above defined charge are evaluated for residual voltage after disconnect. ES classification depends on the result.
• Glow wire / needle flame — applicable to PIS-adjacent plastics. Acceptance criteria are explicit.
• Drop test — for hand-held products, with body-part exposure as the pass/fail criterion.

Test sequence and sample preparation

62368-1 is fussier than 60950-1 about sample preparation order. Humidity conditioning before dielectric testing, dielectric testing before insulation-resistance, abnormal operation on dedicated samples (not the ones used for normal-operation tests). Plan for at least four production-representative samples per programme; six is safer.

Lab and report turnaround

For products that fit cleanly inside one Annex (basic IT equipment, audio/video), a competent lab will turn an evaluation in 8–10 weeks. Products with batteries, novel topologies, or multi-jurisdictional submissions can stretch to 16+ weeks. The most common cause of slip: incomplete construction-detail documentation arriving at the lab. Send everything — Gerbers, schematics, BOM with material certs, transformer construction sheets, enclosure flammability evidence — in the first package.

For a manufacturer with one or more products currently certified under UL 60950-1, the migration is a structured project rather than a redesign. Here's the playbook we run with customers.

Step 1 — Inventory and triage (Week 1)

• List every certificate (UL, CB, ENEC, etc.) referencing 60950-1.
• Note the expiry date and the target market for each.
• Cluster products by topology — products with identical power architecture can usually share an evaluation strategy.

Step 2 — Gap analysis per product (Weeks 2–4)

• Re-derive working voltages and re-check creepage/clearance under 62368-1 tables.
• Identify PIS components and verify enclosure materials match required PS class.
• Confirm every BOM line that contributes to safety has a component-level file number or equivalent reference.
• Identify battery, capacitor stored-energy, and abnormal-operation tests that were not in the original 60950-1 evaluation.

Step 3 — Design changes (Weeks 4–10)

The most common changes we see in practice:

1. Opto-isolator swap to a part with explicit 62368-1 reinforced rating in the datasheet.
2. Transformer redesign or re-certification to align with new working-voltage calculations.
3. PCB layout tweak to lift one creepage distance that was at the 60950-1 minimum.
4. Material change on an interior cable jacket that was VW-1 but unrated for needle-flame in the new PIS analysis.

Step 4 — Lab submission and follow-up (Weeks 10–22)

Submit with a complete construction file the first time. Budget for one round of clarification questions from the lab even on a clean submission — the test engineer always finds something to ask about.

What it costs

For a single product family, typical end-to-end cost: $25–60k in lab fees plus 4–8 engineer-weeks. Multi-product families with shared architecture can amortise to half that per product. Skipping migration is more expensive — markets enforce 62368-1 today, and a withdrawn product line costs more than a re-certified one.

If you're staring at a list of 60950-1 certificates expiring through 2026, our compliance team can run a fixed-cost migration inventory in five working days.