UL 840 2022-04 PDF

Full title and description

UL 840 — Insulation Coordination Including Clearances and Creepage Distances for Electrical Equipment. This edition (Redline) was issued April 19, 2022 and provides an alternative, principle-based approach for specifying required through‑air clearances and over‑surface creepage distances for low‑voltage electrical equipment.

Abstract

UL 840 defines insulation coordination principles for electrical equipment design, replacing fixed spacing tables with requirements that account for working voltage, overvoltage category, pollution degree, material group and related factors. The standard is intended to harmonize spacing practices with international insulation coordination principles (aligned conceptually with IEC 60664) and to be used as an alternative approach where referenced by product‑specific UL standards.

General information

• Status: Active / Current.
• Publication date: Redline edition issued April 19, 2022 (Edition 3 redline to Ed.3‑2005).
• Publisher: UL Standards & Engagement (Underwriters Laboratories).
• ICS / categories: Electrical engineering (ICS 29.020) / Insulation and related topics (ICS 29.080).
• Edition / version: Edition 3 (Ed. 3, 2005 basis) with Redline revision dated 2022‑04‑19.
• Number of pages: Approximately 36–41 pages (PDF redline edition length varies by publisher distribution).

Scope

Sets out requirements and evaluation methods for determining through‑air clearances and over‑surface creepage distances used in the insulation coordination of electrical equipment rated for low‑voltage applications. The document covers principles useful to designers and testing bodies, measurement procedures for verifying clearances/creepage, and notes how influencing factors (mechanical movement, field alterations, contamination, material properties) must be considered when applying the requirements. It is intended to be used where a product‑specific safety standard references UL 840 as an acceptable alternative approach.

Key topics and requirements

• Principles of insulation coordination for electrical equipment design (working voltage, overvoltage category, insulation system concepts).
• Methods for sizing clearances (through‑air) and creepage distances (over‑surface) based on pollution degree and material group.
• Measurement procedures for verifying clearances and creepage distances on finished equipment (physical measurement rules and test guidance).
• Use of UL 840 as an alternative, principle‑based approach where product standards reference it; relationship and alignment with IEC 60664 insulation coordination principles.
• Consideration of environmental and installation factors (contamination, mechanical movement, field modifications) and their effect on required spacing.

Typical use and users

Commonly used by electrical product designers and engineers (power supplies, motors, drives, control equipment, switchgear), test laboratories and certification bodies, safety engineers, and manufacturers preparing documentation and layouts for product safety evaluations. Also referenced by standards writers when specifying insulation spacing alternatives for specific product categories.

Related standards

Closely related to and often used in conjunction with IEC 60664 (Insulation coordination for equipment within low‑voltage systems). UL 840 is referenced by many UL product standards (examples include UL 508, UL 508C and others dealing with industrial control and power conversion equipment) and cross‑references UL materials and insulation standards such as UL 746 series.

Keywords

Insulation coordination; clearance; creepage; creepage distance; through‑air clearance; pollution degree; material group; dielectric withstand; UL 840; electrical equipment safety; IEC 60664.

FAQ

Q: What is this standard?

A: UL 840 is a UL safety standard titled "Insulation Coordination Including Clearances and Creepage Distances for Electrical Equipment" that provides a principles‑based approach to determine required electrical clearances and creepage distances for low‑voltage equipment.

Q: What does it cover?

A: It covers methods and requirements for sizing and measuring through‑air clearances and over‑surface creepage distances, factors affecting insulation coordination (voltage, overvoltage category, pollution degree, material properties), and guidance on verification and measurement of those distances on equipment.

Q: Who typically uses it?

A: Product designers and electrical engineers, certification and testing laboratories, manufacturers preparing safety documentation, and standards developers who reference insulation coordination requirements for specific product categories.

Q: Is it current or superseded?

A: The Edition 3 redline (April 19, 2022) is published as the active / current redline revision to Edition 3 (2005 basis). Users should confirm the publisher's site or current UL catalog for any amendments after that date.

Q: Is it part of a series?

A: UL 840 is a standalone UL safety standard but it is frequently cross‑referenced by many UL product standards and relates conceptually to the IEC insulation coordination family (IEC 60664). It also cross‑references other UL material and insulation standards (for example UL 746 series) when assessing insulation systems.

Q: What are the key keywords?

A: Insulation coordination, clearance, creepage, pollution degree, material group, dielectric test, UL 840, IEC 60664.