UL 1449 Adjunct Testing

Caution: Do not confuse the endurance (adjunct) testing discussed in this document with the safety testing that UL are usually associated with. UL 1449 certification does not automatically mean that a product also passes the adjunct endurance testing (which is optional), it only means that the product has passed safety guidelines.

Beginning with meetings in 1992 and culminating with a new standard at the end of 1995, the Federal Government commissioned Underwriters Labs (UL) to develop testing specifically to determine the effectiveness and reliability of surge protectors. UL was chosen for this task because they had the necessary experience, and already had a safety standard in place for surge protectors (UL 1449). The additional testing procedure for endurance was added to UL 1449 as adjunct testing. During 1996, the Federal Government followed up with a CID (Commercial Item Description) based on the UL 1449 adjunct testing. All Federal Government orders now require surge protectors to meet this CID.

The required Federal testing consists of Grades A, B and C, Classes 1, 2 and 3, and Modes 1 and 2. The Grade determines the level of surge voltage and current applied during testing, Grade A being the highest, consisting of 1000 surges of 6000V and 3000A. The Class specifies the let-through voltage, Class 1 being the best, not exceeding 330V. The Mode specifies whether ground is contaminated, Mode 1 being that ground is not contaminated.

ALL SurgeX® PRODUCTS ARE CERTIFIED GRADE A, CLASS 1, MODE 1:

  • SURVIVED 1000 SURGES OF 6000V, 3000A
  • NO FAILURES OR DEGRADATION
  • LET-THROUGH VOLTAGE DID NOT EXCEED 330V
  • GROUND WAS NOT CONTAMINATED

It is important to realize the difference between "let-through" voltage and "clamping" voltage. Clamping voltage often means the voltage at which the surge suppressor begins to work, not the suppressed voltage under actual worst-case test conditions. Further information on UL 1449 is available from SurgeX.

The important points for the prospective purchaser of surge protection equipment to keep in mind are:

  • Grade A guarantees protection from the worst surges normally found within a building during a lightning strike (as defined by IEEE/ANSI C62.41-1991).
  • Class 1 provides the best quality surge suppression.
  • Mode 1 guarantees that ground is not contaminated.
  • UL 1449 safety testing does not test for endurance.
  • UL endurance testing is optional. Manufacturers are not required to submit their products for endurance testing, but those who do can offer the customer a guarantee of performance.
  • There is no reason for manufacturers of quality products not to submit their surge protectors for endurance testing.
  • A product that does not have an endurance rating has no guarantee of performance.