UL offers iQ for Surge-Protective Devices, a free online database that gives you the ability to find, verify and specify a surge protective device by selecting from a set of over 20 parameters to meet your specific application. Watch the video to learn how UL iQ can help you find the SPD you are looking for.



Surge protective devices (SPDs), intended to afford protection from electrical surges and spikes, including those caused directly and indirectly by lightning, are utilized as both complete devices and as components within electrical equipment installed in AC and DC power systems.

The use of SPDs is often specified by the end user or mandated by code or local requirements. For example, NFPA 780 and UL 96A (Standard for Installation Requirements for Lightning Protection Systems) require the use of surge protection as an integral part of a lightning protection system. Additionally, the National Electric Code, NFPA 70, requires surge protective devices (Article 285) to be installed:

  • Where disconnecting means has been designated as supplying an emergency system load in elevators, dumbwaiters, escalators, moving walks, platform lifts, and stairway chairlifts
  • For critical operations data systems of information technology equipment
  • For Industrial machinery with safety interlock circuits
  • In or on the fire pump controllers
  • In or on all emergency systems switchboards and panelboards
  • At all facility distribution voltage levels in critical operations power systems (COPS)

The use of SPDs have increased due to the proliferation of more complex electronics, LED lighting, photovoltaics and microprocessor controlled devices that are more susceptible to damage due to surges caused by lightning and switching disturbances. Surge protection needs within a building will vary depending on the surge withstand capability of the equipment being protected, level of protection desired, geography or location of the equipment and the functional criticality of the equipment.


UL evaluates SPDs to the following standards for compliance and safety:

  • U.S. – UL 1449, Standard for Surge Protective Devices (SPDs)
  • Canada – CSA C22.2 NO. 269 Series of SPD Standards
  • International – IEC/EN 61643-11, -311, -321, -331, IEC 61643-31, IEC 61051

UL provides investigations, testing
and certification services for the following types of surge protective devices:

  • Permanently-Connected – Types 1, 2 and 3 SPDs
  • Cord Connected – Type 3 SPDs
  • Outdoor-Use (RV) Cord Connected – Type 3 SPDs
  • Direct Plug-In – Type 3 SPDs
  • Receptacle Type – Type 3 SPDs
  • Open-Type – Types 1, 2 and 3 SPDs
  • Molded Case SPDs – Types 1 and 2 SPDs
  • SPDs Certified for Use in Specified Equipment – Types 1 and 2 SPDs
  • Circuit Breakers/SPDs – Types 1 and 2 SPDs
  • Photovoltaic (PV) – Types 1, 2, 4 Component Assembly and Type 5 Component SPDs
  • DC SPDs – Types 1, 2, 3 and 4 Component Assembly and Type 5 Component SPDs
  • Modular component SPDs – Types 1, 2, 3 and 4 Component Assembly and Type 5 Component
  • Discrete component SPDs – Type 4 Component Assembly and Type 5 Component, includes:
    • SPDs Metal Oxide Varistors (MOVs)
    • Gas Discharge Tubes (GDTs)
    • Silicon Avalanche Diodes (SADs)/Avalanche Breakdown Diodes (ABDs)
    • Hybrid Devices consisting of MOVs, GDT, SADs and/or other components
  • IEC/EN 61643-11 – CB Certificate (IEC 61643-11), Informative Test Report (CE), Test Type Certificates, UL EU Mark, D Mark, UL Certification to IEC Publications (VZCC)
  • IEC 61643-31 – Informative Test Report (CE)
  • IEC/EN 61643-311, -321, -331 – Informative Test Report (CE), Test Type Certificates, UL EU Mark, D Mark, UL Certification to IEC Publications (VZCC)
  • IEC 61051 – Informative Test Report (CE), UL Certification of Component Varistors to IEC Standards (YURA2)


With combined testing of SPDs, UL can simultaneously provide global market access solutions for the UL Mark in North America, as well as other certifications for markets around the world. One certification process allows you to profit from faster speed to market. This streamlined and accelerated process helps save time and money through a well-proven global certification program.

UL’s proven expertise in safety science and engineering enables us to serve the entire SPD industry, from simple SPDs for light commercial and residential applications to complex SPDs that monitor and record the number of surges and indicate the status of an SPD. Our extensive, flexible service portfolio covers research and development, global market access, installation and end use.

View the scope and table of contents for the UL Standard that applies to your regulatory or engineering needs.