Elastomers for Electrical Equipment Enclosure Requirements

The UL standard used to evaluate elastomeric gasket materials is UL 157, Gaskets and Seals. In addition to certifying gaskets materials to UL 157, UL offers Component Recognition for UL 50E “Electrical Equipment Enclosures.” UL’s extensive certification program for elastomeric materials facilitates the acceptance of these components in end products.

Both solid and cellular gasket materials can be evaluated to UL 50E, but not all materials require the UL 50E Compression test. Solid gasket materials and cellular gasket materials used in electrical enclosures where the seal is intended to be under continuous compression for the life of the seal (e.g. gaskets used in pilot lights, selector switches and viewing windows) are not required to comply with the UL 50E Compression Test. The UL 50E Compression Test applies only to cellular gasket materials used in periodic recompression applications where the seal may periodically be broken and must be reestablished (e.g. door or cover seals on electrical enclosures).

UL 50E certifies with the following ratings:

  • “UL 50E” applies only to solid gaskets. These gaskets need not comply with the Compression Test but are considered suitable for either Continuous Compression or Periodic Recompression applications.
  •  “UL 50E Continuous Compression” applies to cellular gaskets that have not been evaluated to the Compression test requirements. Gaskets are only suitable for Continuous Compression applications.
  •  “UL 50E Periodic Recompression” applies to cellular gaskets that comply with the Compression Test requirements. Gaskets are considered suitable for either Continuous Compression or Periodic Recompression applications.

The first edition of UL 50E, Enclosures for Electrical Equipment, Environmental Considerations, incorporates a new “Compression Test” in addition to tensile strength, elongation and volume change requirements previously in effect. The effective date of September 4, 2012 originally set for compliance with the new Compression Test was extended to September 4, 2015 to permit additional time for gasket manufacturers and their customers to attain certification with respect to the new requirement.