UL Electrical Electronics Enclosure and Motors Classifications ( 50 & 508 )

  Instrumentation and Electronics
Rack Mounted Enclosure Manufacturers

UL Listed Enclosures

UL Electrical Electronics Enclosure and Motors Classifications 50 & 508

This material is derived from Underwriters Laboratories Inc. Enclosures for Electrical Equipment, UL 50 and 508. The information contained herein is not intended to be complete descriptions. Refer to U. L. Standard 50 & 508 for complete details.

UL 50 applies to enclosures for electrical equipment intended to be installed and used in non-hazardous locations in accordance with National Electrical Code, NFPA 70, Canadian Electrical Code, Part I, CSA C22.1, and within the provisions of the Mexico's Electrical Installations, NOM-001-SEDE, as follows:

  • Enclosures for indoor locations, Types 1, 2, 5, 12, 12K, and 13; and
  • Enclosures for indoor or outdoor locations, Types 3, 3R, 3S, 4, 4X, 6, and 6P.

UL 508 applies to industrial control devices, and devices accessory associated, for starting, stopping, regulating, controlling, or protecting electric motors. These requirements also cover industrial control devices or systems that store or process information and are provided with an output motor control function(s). This equipment is for use in ordinary locations in accordance with the National Electrical Code, NFPA 70.

These requirements cover devices rated 1500 volts or less. Industrial control equipment covered by these requirements is intended for use in an ambient temperature of 0 - 40°C (32 - 104°F) unless specifically indicated for use in other conditions.

Examples of industrial control devices are:

  • Manual, magnetic, and solid-state starters and controllers.
  • Thermal, magnetic, and solid-state overload relays.
  • Pushbutton stations, including selector switches and pilot lights.
  • Control circuit switches and relays.
  • Float, flow, pressure, and vacuum-operated switches.
  • Resistors and rheostats.
  • Proximity switches.
  • Time-delay relays and switches.
  • Resistors and rheostats intended for industrial heating and lighting, including those for motor generator fields.
  • Control devices intended for industrial heating and lighting.
  • Solid-state time-delay relays.
  • Programmable controllers.
  • Numerical control systems.
  • Lighting dimmer systems and controls.
  • Mercury-tube switches.
  • Definite purpose controllers.
  • Solid-state logic controllers.
  • Industrial microprocessor/computer systems.
  • Variable voltage autotransformer.
  • Motor starting autotransformer.

TYPE UL 50 and 508 Electrical Enclosure Application and Description
Type 1 Indoor use primarily to provide protection against contact with the enclosed equipment and against limited amount of falling dirt.
Type 2 Indoor use to provide a degree of protection against limited amounts of falling water and dirt.
Type 3 Outdoor use to provide a degree of protection against windblown dust and windblown rain; undamaged by the formation of ice on the enclosure.
Type 3R Outdoor use to provide a degree of protection against falling rain; undamaged by the formation of ice on the enclosure.
Type 4 Either indoor or outdoor use to provide a degree of protection against falling rain, splashing water, and hose-directed water; undamaged by the formation of ice on the enclosure.
Type 4X Same as type 4 except this one is corrosion resistant.
Type 6 Indoor or outdoor use to provide a degree of protection against entry of water during temporary submersion at a limited depth; undamaged by formation of ice on the enclosure.
Type 12 Indoor use to provide a degree of protection against dust, dirt, fiber flaying, dripping water, and external condensation of non-corrosive liquids.
Type 12K Indoor use to provide a degree of protection against dust, dirt, fiber flying's, dripping water, and external condensation of non corrosive liquids.
Type 13 Indoor use to provide a degree of protection against lint, dust seepage, external condensation and spraying of water, oil, and non-corrosive liquids.

UL standard writing organizations commonly recognized in North America. Their ratings are based on similar application descriptions and expected performance. UL and CSA both require enclosure testing by qualified evaluators.They also send site inspectors to make sure a manufacturer adheres to prescribed manufacturing methods and material specifications. NEMA, on the other hand, does not require independent testing and leaves compliance completely up to the manufacturer.

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