Installed at a minimum conductor length of 10 meters (30 feet) from the electrical service panel
The component assembly consisting of one or more Type 5 components (typically MOV or SASD)
Must comply with limited current tests and In
Not tested as standalone devices to intermediate and high current faults
Discrete component surge suppressors such as surge components (MOV or SASD)
May be mounted on a PCB connected by leads
Can be utilized within an enclosure with mounting means and wiring terminations
Not tested too low, intermediate or high fault currents
Must be mounted within another enclosure
Testing is Key
Critical to UL listing is standardized testing. This table details the testing regulations for Type 4 and Type 5 SPD component assemblies.
Type 4 SPD
Type 5 SPD
I Leakage (initial)
Dielectric Voltage Withstand
Vn (Before and After In)
Nominal Discharge Current (In)
Measured Limiting Voltage (MLV)
Fault and Overcurrent
I Leakage (initial)
After Obtained UL certification, manufacturer take responsibility to meet standards seriously. All of SPDs include clear and permanent required markings to ensure the solutions you choose meet UL 1449.
Nominal discharge current (In) rating
Maximum continuous operating voltage rating (MCOV)
Voltage protection rating (VPR)
Measured limiting voltage (MLV)
Date or period of manufacture
Short circuit current rating (SSCR)
Type 4 component assemblies and Type 5 SPDs require MLV, MCOV, operating voltage, and In ratings. For Type 5 SPDs these ratings may be provided in data sheets.
Glossary of Key Terms
Fault current – Current from power system that flows in a short circuit
Maximum continuous operating voltage (MCOV) – Maximum amount of voltage that can be applied continuously to SPD
Measured limiting voltage – Maximum magnitude of voltage measured when In is applied
Nominal discharge current (In) – Peak value of current (8 x 20 wave shape) driven through the SPD 15 times (SPD must remain operational)
Nominal operating voltage – Normal AC power voltage of the system
Nominal voltage (Vn) – DC voltage measured across the SPD when 1mA flows
Short circuit current rating (SCCR) – Suitability of an SPD to withstand a declared short circuit from the power source
Voltage protection rating (VPR) – Voltage rating selected from a list of preferred values when a combination wave of 6kV 3kA is applied
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