The Newest UL 1449 Safety Standard is Now in Effect

The newest UL 1449 safety standard for Surge Protective Devices (SPD’s) is now in effect.  

Changes at a Glance:
  • Suppressed Voltage Rating vs. Voltage Protection Rating - The SPD’s let-through voltage is now measured as it is subjected to an IEEE defined 6kV/3kA “combination waveform".
  • Nominal Discharge Current - The SPD’s Nominal Discharge Current capability, up to 20 kA, is now reported with the suppressor’s specifications and on its labeling.
  • Suppressor Categories - The new standard categorizes SPDs as one of four designated types based upon whether or not they are a component, and where within an electrical distribution they are to be installed.
  • TVSS is now SPD - The term identifying a surge suppressor as Transient Voltage Surge Suppressor (TVSS) was retired and will now be called a Surge Protective Device (SPD).
  • Extended Scope - 3rd Edition UL now governs suppression products designed to protect on electrical circuits up to 1000 V.
A Closer Look at the Changes:

Suppressed Voltage Rating (SVR) versus Voltage Protection Rating (VPR)
With UL 1449 3rd Edition, the reference to the suppressor’s Suppressed Voltage Rating (SVR) was retired. With this newest Edition, the SPD’s VPR is determined as it is measured when the surge suppressor is subjected to an IEEE defined 6 kV/3 kA test waveform. The new standard includes testing additions and modifications that call for the SPD under test to be repeatedly subjected to high current test impulses to verify its Nominal Discharge Current capacities, along with tests to determine its Voltage Protection Rating (VPR). With the 2nd Edition, the suppressor’s SVR reported the device’s let through voltage as is it was called upon to conduct 500 amps of surge current.
The new VPR ratings are required to be displayed on the UL label for each SPD. A suppressor’s VPR will likely be reported at higher values than its corresponding SVR.

Nominal Discharge Current
UL 1449 3rd Edition now requires the manufacturers to select a Nominal Discharge Current value for the SPD product, and test the device at the selected level. The manufacturer can designate nominal discharge current to be between 3 kA and 20 kA. The SPD under test is subjected to 15 impulses at the manufacturer’s designated nominal discharge current value. Not only does the SPD have to safely withstand these test impulses, but so do any or all fusing devices, circuit breakers, or other types of overcurrent limiters that are installed internally or externally to the SPD, but which are contained within the suppression path between the SPD and its test inputs.

Suppressor Categories
UL 1449 3rd Edition categorizes SPD’s as four different types:
  • Type 1 suppression products are those products that were formerly referred to as secondary Surge Arrestors. These are permanently connected SPDs that are intended to be installed between the secondary of the distribution transformer supplying power to a facility, and the input side of the main circuit breaker in the distribution panel that is located at the facility’s electrical entrance.
  • Type 2 suppression products are those devices that were formerly referred to as TVSS equipment. They are permanently connected SPDs intended for installation on the load side of the main circuit breaker or other type of overcurrent protector including those that are intended to install upon branch distribution panels.
  • Type 3 devices are referred to as point of utilization SPDs. This equipment is intended to be installed at least 10 meters (32.8 feet) of conductor length away from the electrical distribution panel to its actual point of utilization. Type 3 suppressors include cord connected products, direct plug-in suppressors, receptacle type SPDs, and surge suppressors that are intended to install directly upon the equipment to be protected. The distance is exclusive of conductors provided with or used to attach the SPDs.
  • Type 4 surge suppressors regard SPD components. They include discrete components as well as component assemblies. With the 3rd Edition, Type 4 devices reflect what the 2nd Edition referred to as “UL Recognized” TVSS. Strikesorb is the only UL Recognized SPD which has successfully gone through the complete revised testing procedure of the new UL1449 3rd Edition standard. Strikesorb modules do not need any further testing according to UL1449 3rd Edition in order to meet the requirements for UL Listing.
TVSS is now SPD
The 3rd Edition term Surge Protective Device (SPD) encompasses both what we formerly called TVSS equipment, and products that were referred to as secondary surge arrestors.  With this new Edition, UL is using terminology consistent with global standards. The term Transient Voltage Surge Suppressor (TVSS) will no longer be used.

Extended Scope
3rd Edition presides over SPDs that install on circuits up to 1000 volts.  The UL 2nd Edition applied to suppression products intended for use on electrical circuits under 600 volts.