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Powerful Modular Surge Protection with Fault Detection: M-LB-4000


Pluggable Surge Protection System for Signal Circuits

M-LB-4000 surge protection system

Pepperl+Fuchs adds the powerful M-LB-4000 to its portfolio of surge protection systems. The two-part system is based on a modular design consisting of a base module and a protection module. The latter contains the entire protection function. Thanks to this modularity of the M-LB-4000, installation and maintenance are simple and convenient. The base modules are mounted onto a standard 35 mm DIN-rail, while the protection modules can be plugged effortlessly into the base modules. This means that the M-LB-4000 does not require any tools for installation, and also enables devices to be replaced during operation without disrupting the existing wiring. While the base module remains in the mounting position, the protection module can be easily removed and replaced. An interruption of the signal circuit is avoided by the innovative mechanics in the base module.

The loop disconnect function of the M-LB-4000 also allows for isolated tests and loop checks during commissioning and maintenance of the system. To do this, the protection module is simply unplugged, rotated by 180°, and then plugged back in. The integrated disconnect function then automatically breaks the circuit, allowing personnel to work safely on the signal circuit.

Slim and Smart

With a width of only 6 mm, the modules of the M-LB-4000 surge protection system are especially compact and require little space in the control cabinet. Despite its slim design, the M-LB-4000 has high functionality: In addition to reliable protection against overvoltage, the system offers continuous self-monitoring. Each module has a status display on the front, signaling its status at all times. A two-part fault status module is also capable of monitoring several surge protection modules and forwarding the fault message to the control room. In this way, faults can be detected remotely and resolved immediately.

The new M-LB-4000 surge protection system is available both as an intrinsically safe variant for hazardous areas and without intrinsic safety for non-Ex areas. With a temperature range of -40 °C to +80 °C, it can be used in a wide range of applications. Consequently, the M-LB-4000 reliably protects signal circuits from damage caused by surge events and contributes to more plant availability in all branches of industry. 

Highlights of M-LB-4000

  • Easy replacement due to pluggable modules
  • Protection function in the replaceable protection module
  • Hot-swappable during operation without interruption of the signal circuit
  • Loop disconnect feature for easy maintenance and commissioning
  • Compact width of only 6 mm
  • Continuous self-monitoring with status indication
  • Global certifications


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The new surge protection system M-LB-4000 offers reliable diagnostics, easy handling and a space saving housing design. Learn more here!