UL 50 2020-10 PDF

Full title and description

UL 50:2020 — Enclosures for Electrical Equipment, Non‑Environmental Considerations. This standard sets construction and performance requirements, tests and labeling practices for enclosures intended to house electrical equipment in non‑hazardous locations (covers the common NEMA/Type designations used for indoor and outdoor electrical enclosures).

Abstract

UL 50:2020 provides the non‑environmental construction and performance requirements used to evaluate enclosures for electrical equipment. It defines enclosure types (e.g., Type 1, 2, 3, 4, 4X, 6P, 12, 13, etc.), material and fastening requirements, mechanical and electrical safety considerations, and the standardized tests used to verify protection against incidental contact and ingress under specified conditions. The October 15, 2020 revision clarified and updated test orientations, material allowances, and several test procedures; this 2020 edition was later superseded by a 2024 edition.

General information

• Status: Superseded — replaced by UL 50, Edition 14 (published February 29, 2024).
• Publication date: October 15, 2020.
• Publisher: Underwriters Laboratories (UL).
• ICS / categories: 21.180 — Housings, enclosures, other machine parts (Electrical equipment enclosures / NEMA type classifications).
• Edition / version: UL 50:2020 (commonly referenced as the 2020 revision). Note: an updated edition (Edition 14) was published on February 29, 2024.
• Number of pages: Approximately 69 pages (UL 50:2020 published technical document length).

Scope

This standard applies to enclosures for electrical equipment intended for installation and use in non‑hazardous locations. It covers indoor enclosure types (for example Types 1, 2, 5, 12, 12K and 13) and indoor/outdoor enclosure types (for example Types 3, 3R, 3S, 3X, 3RX, 3SX, 4, 4X, 6 and 6P). UL 50 addresses construction, mechanical strength, basic ingress protection for personnel and equipment, required markings and basic performance tests; environmental construction/performance details are addressed in companion documents (for example UL 50E / CSA counterparts).

Key topics and requirements

• Definitions and classification of enclosure types (NEMA/Type designations and intended application: indoor vs outdoor, corrosion resistance levels).
• Material and construction requirements (metallic and non‑metallic materials, sheet thicknesses, seams, welds, fasteners, hinges, latches, and observation windows).
• Mechanical protection and strength tests (edge/sharpness, mounting integrity, door/hardware strength and operation).
• Ingress protection and hosedown tests, orientation of samples during testing, and conduit misalignment/attachment tests for hubs.
• Gasket, sealant and closure performance (tensile/elongation tests, aging alternatives, gasket seating, torque requirements for conduit hubs).
• Corrosion protection and coating/finish thickness verification (including allowable test methods for metallic coating thickness).
• Labeling, marking and required documentation (type designation, ratings, material identification and manufacturer information).
• Requirements for special constructions such as ventilated or encapsulated enclosures and provisions for observation/inspection windows.

Typical use and users

Used by enclosure manufacturers, electrical and controls OEMs, specifiers, product designers, safety and compliance engineers, testing laboratories, certification bodies and procurement teams. Typical applications include motor control centers, junction and pull boxes, electrical control cabinets, telecom cabinets, instrumentation enclosures and general equipment housings requiring defined degrees of protection in industrial, commercial and utility settings.

Related standards

Commonly used alongside or referenced with: UL 50E (Enclosures for Electrical Equipment — Environmental Considerations), CSA C22.2 No. 94.x series (Canadian enclosure standards), NMX/J harmonized Mexican standards, the National Electrical Code (NFPA 70), and related UL standards such as UL 94 (flammability of plastics), UL 467 (grounding/bonding), UL 514 series (outlet boxes and fittings) and other product‑specific UL or IEC test standards referenced in annexes.

Keywords

enclosure, electrical enclosure, UL 50, NEMA type, ingress protection, gasket, hosedown test, conduit hub, corrosion protection, enclosure labeling, non‑environmental considerations, UL 50:2020

FAQ

Q: What is this standard?

A: UL 50:2020 is the Underwriters Laboratories standard that specifies non‑environmental construction and performance requirements for enclosures that house electrical equipment in non‑hazardous locations.

Q: What does it cover?

A: It covers enclosure design and construction details, classification by enclosure type (common NEMA/Type designations), mechanical and ingress protection tests, gasket and seal requirements, material and finish considerations, and required markings and documentation. Environmental performance details are addressed in related documents such as UL 50E.

Q: Who typically uses it?

A: Enclosure manufacturers, OEMs, electrical designers, compliance and safety engineers, test laboratories, and purchasing/specification teams that need to ensure enclosures meet defined protection and safety requirements for specified applications.

Q: Is it current or superseded?

A: The October 15, 2020 edition (UL 50:2020) was an important revision but has been superseded. UL released Edition 14 of UL 50 on February 29, 2024; users should reference the 2024 edition for the latest requirements and use UL 50:2020 only where specifically required for legacy product certification or historic reference.

Q: Is it part of a series?

A: Yes. UL 50 is part of a family of enclosure standards and is commonly used together with UL 50E (environmental considerations) and several other product and test standards (UL 94, UL 514 series, CSA/ANECE harmonized enclosure standards) that together define full product requirements for different environments and jurisdictions.

Q: What are the key keywords?

A: enclosure, NEMA type, ingress protection, gasket, hosedown, conduit hub, corrosion, UL 50, electrical equipment enclosures.