UL 508B
Outline of Investigation for Relays Used in Information Technology Equipment

Edition Number:2SCC Approved:--
Edition Date:2006-11-15DOD Approved: --
Price Code:AANSI Approved: --


    1 Scope

    1.1 This Outline of Investigation covers the requirements applicable to relays intended for use in accordance with the Standard for Safety of Information Technology Equipment Including Electrical Business Equipment, UL 1950.

    1.2 The relays covered are limited to those with air gap isolation or a barrier of solid insulation between coil and contacts (electromechanical types) or between input and output circuits (solid state types). This separation between coil and contacts or input and output circuits shall comply with the requirements for basic, double, or reinforced insulation as specified in UL 1950.

    1.3 Limiting impedance, as described in the Standard for Industrial Control Equipment, UL 508, is not considered a suitable means of isolation between input and output circuits.

    1.4 An optical isolator may be used in solid state relays to comply with the air gap or solid insulation requirement.

    Expand All

    • Outline Title Page
    • Table of Contents
      • Body
          • 1 Scope
          • 2 Glossary
          • 3 General
          • 4 Spacings
          • 5 Securement of Wiring and Parts
          • 6 Flammability of Materials
          • 7 Electric Strength Test
          • 8 Primary Power Isolation (optional)
          • 9 Safety Interlocks (optional)