UL’s safety and performance standard for Surge Protective Devices (SPD), formerly known as Transient Voltage Surge Suppressors (TVSS), is UL 1449. This standard applies to end-users, manufacturers, and specifiers.
|At a Glance: |
As a generalization, UL addresses electrical product safety in areas that involve a risk of fire, electric shock, or injury to persons. UL verifies the safe operation of SPDs through a listing or component recognition process including a series of stringent destructive and non-destructive tests. These ensure safe operation during normal operation and at the unit’s end of life.
End-of-life characteristics are particularly important because SPDs are placed in harm’s way and can affect the rest of the electrical distribution system. Areas of interest include fault current testing, thermal issues, touch-safety, etc.
Nationally Recognized Testing Laboratories (NRTLs – such as UL, CSA, Intertek, MET Labs, etc.) provide a valuable service to specifiers and end-users by testing the performance of all SPDs the same way. This is the only ‘common’ testing format in the industry, making it an important barometer of performance.
- SPDs are marked with a Voltage Protection Rating (VPR) that is obtained during the Nominal Discharge Current test using a 6 kV, 3 kA Combination Wave Generator. The VPR marking replaces the previously used SVR marking. It should be noted that the VPR is obtained using a much higher short-circuit surge current.
- SPDs are marked with a Nominal Discharge Current Rating that is verified to ensure that the SPD is fully operational when subjected to 15 surges at the marked level. Nominal Discharge Current Ratings include 20 kA, 10 kA, 5 kA and 3 kA.
- SPDs are marked with an SPD “Type” that indicates where the SPD can be installed within the electrical system. For more information on SPD types, see What is SPD section on this website.
- Conditions of Acceptability – One important aspect of SPDs that is often misunderstood is the difference between a “Listed” and a “Component Recognized” SPD. A listed SPD is one that has met all the requirements of the UL 1449 standard. A component recognized SPD is one that may not have been subjected to all the requirements of the UL 1449 standard and will have “conditions of acceptability”. Contact the SPD manufacturer to determine the conditions of acceptability.