FAQ's for SPDs (Surge Protective Devices)

Surge Protective Devices General FAQs
 

Q. How do I know which SPD to buy?
A. SPDs are designed to protect different power sources. While single phase and split phase circuits are straight forward, 3-phase power sources require the correct SPD. This application note shows how to determine the power source and select the correct SPD.

Q. Where can I find an explanation of the terms associated with the SPDs specifications and applications?
A. This application note provides definitions commonly used when specifying and installing SPDs.

Q. Are the Mersen Surge Trap SPDs lightning arrestors?
A. Mersen Surge Trap SPDs alone are not lightning arrestors. An SPD cannot protect against a direct lightning strike. A UL96 lightning protection system is used for direct lightning strikes. The UL96 specification requires a UL96 SPD be used on the incoming power of the protect location. The Surge Trap SPD can protect against indirect lightning strikes such as trees, ground strikes, and power lines. This video explains indirect lightning strikes.

Q. How should I mount an SPD?
A. For the maximum protection, SPDs should be mounted as directed for the specific device. Please visit the Application Notes page for mounting instructions for each SPD Series.

Q. Can I extend the wires of the SPD for my installation?
A. SPD wiring should be kept as short as possible for maximum protection. When installing an SPD with pre-wired leads, the excess wire should be cut. See this application note for the effects of lead length and routing, and connection of SPD wiring.

Q. Can I use multiple SPDs in a facility or home?
A. Yes. Layering or cascading SPDs provide a higher level of protection from voltage disturbances in a residence or facility. The glossary application note explains where the different SPD type rating can be used.

Q. Do SPDs have a finite life?
A. Yes. Each time the SPD protects against an overvoltage or transient, a portion of the SPD’s MOVs are depleted. This is true with all SPDs. The Surge Trap SPD have LEDs, switch contacts, and indicator flags to alert to the end of life of the SPD. The life span of an SPD depends on the frequency of voltage disturbances.

Q. How are SPDs mounted?
A. The Surge Trap SPDs have different mounting methods, depending on the Series and application. Industry standard knockout are sizes are used for the STXH and STXR Series. The STLC SPD mounts in most residential 1” pitch load centers. The STP Series SPDs mount on standard 35mm DIN rail. STPT2 Solar PV DIN rail mount SPDs are available in 600-, 1000-, and 1500-volt models.

Q. What do the KA ratings mean?
A. Please download this application note for an explanation of the different types of power disturbances and how the short circuit ratings and where they are required.