When seeing applications for low-voltage surge arresters that allow installation up to 4,000A, especially in Class B, a questioning technical person naturally wonders—and they do: how is it possible to connect a surge arrester to a 4,000A MCCB (Molded Case Circuit Breaker)?

Then suddenly, you see a fuse being recommended in between, and a technician on a forum asks: “Why are we protecting the surge arrester with a fuse?”

Of course, the same handful of people immediately step in with panic and explain confidently: “We are not protecting the surge arrester; it is protecting us.” The man continues to ask, “Well then, why do we put a fuse in front of the surge arrester?”

Immediate explanations follow: “Because at high currents, the surge arrester must trip the fuse and prevent energy from reaching the system.”

But wouldn’t you only be protecting the surge arrester itself by placing a fuse in front of a parallel-connected protection product? In other words, if the fuse you installed trips, won’t the systems fed by that 4,000A line continue to suffer damage?

The man gives up and stops asking. Because that handful of surge arrester importers or salespeople on the forum eventually wear him down.

Surge arrester importers recommend a 125A fuse for Class B and a 63A fuse for Class C if they are to be used for larger systems in surge arrester applications. Technicians who know how a surge arrester functions also know that a surge arrester has no chance of tripping a 125A fuse during a phase-to-ground short circuit.

To trip a 125A fuse during a phase-to-ground short circuit, a residual current device (RCD) could be used, but that cannot be used either because it doesn’t hold and constantly trips in surge arrester applications.

In systems where surge arresters are required, by using Trimbox new generation surge arresters, you eliminate the obligation to place an additional fuse in between, provide protection for all classes with a single product, and additionally perform overvoltage protection.

Simple precautions sometimes save lives. The best investment we can make for our family, our business, and our environment is protective measures. With Trimbox and GNDSeries, you can be protected from electricity-related damages and electrical contact fires caused by them.

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