Login  Register
  Optifuse for your fuse needs...

    PART NUMBER Search:
Become An OptiFuse Distributor
Become An OptiFuse Rep
Join the Optifuse Team
About OptiFuse Selection Guide Glossary of Terms Privacy Statement Site Map Contact OptiFuse

June 17, 2009
UL Listed vs UL Recognized


Why does UL (Underwriters’ Laboratory) make it so complicated??...
I’ll try my best to explain...
UL (as well as CSA and others) develop standardized tests for a variety of products including fuses and fuseholders.  Manufacturers then submit their products to UL for testing against these "standards".  For example, the UL standard for electronic glass fuses is UL 248-14. 
Any manufacturer can submit their product to UL for testing against a standard.  If their product passes all the tests in the standard, then that product is "listed" under that standard.  That product can then carry the UL Listed mark:
 UL Listed
Now let’s suppose for a moment that there is no UL standard for a particular product.  When this occurs, a manufacturer can submit their own product specifications to UL and UL will verify that the manufacturer meets their own specifications.  The UL verified product can now be mark with the UR mark
UL Registered
One point to note...
Different manufacturers might have similar products each marked "UR" but the specifications between manufacturers may vary greatly...
 In summary:
  • UL develops standardized test procedures and standards for specific products
  • Manufacturers can then submit their products to UL for testing against standardized tests
  • If the product passes the testing it becomes UL "listed".
  • If there is no standard UL test for a product then the manufacturer can still submit their product to UL for testing against their own specifications
  • If the product is verified to meet the manufacturer’s own specifications, then the products becomes UL "recognized"
  • Manufacturer’s specifications can greatly differ but still can be marked UR

UL maintains an online registry of all parts listed and recognized for each manufacturer.  Here is are the links to the OptiFuse UL information: 

UL Listed fuses
UL Recognized fuses
Thank you very much for your continued support or OptiFuse...

Jim Kalb

Home  |  Cross-Ref List   |  Products  |  Contact Us