Surge arrester for RS-232 - 5000 amps (type 2)


Surge arrester for RS-232 - 5000 amps (type 2)

Item number 452

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Newly designed protection element for overvoltages and overcurrents with THREE protection levels. The protection cascade combines a high discharge capacity with an extremely short response time and ultra-fast current limiting, resulting in a superior protection effect.

NEW!  Surge arrester and overcurrent protection in one module, certified for 5,000 amps (pulse class C2, tested at 10,000 V)
NEW!  Clamping voltage only 10 V on the device side (after 1 µs)
NEW!  Combination of three stages with a total of 12 protection and flashover paths

NEW!  PE connection with very low contact resistance for uncut and low-impedance 2.5 mm² connection
NEW!  Including two sets of terminals green, grey and orange for three-pole connection of D+, D- and GND

NEW!  Now also available as SparPack or SuperSparPack with addition (one piece for five pieces or two pieces for 10 pieces)

This lightning protection module is designed for all RS-232 connections and bus systems regardless of the protocol used with them:

  • RS-232: Any RS-232 serial interface, RS-232 connections Timberwolf Server, Loxone RS-232 Extension.


  • Design: Module with open REG housing
  • Mounting on DIN rail: Fully assembled with base for DIN rail
  • Terminals: Two times three terminals green, grey and orange for three-pole RS-232 connection
  • PE connection: Pre-assembled with washers, spring washer, nut and crimp connector for 2.5 mm².
  • Quantity according to order, please also note our SparPacks and SuperSparpack



  • Three-stage surge arrester including overcurrent protection to protect the serial RS-232 installation.
  • Combination of short response time, high discharge capacity and fast current limitation
  • Short response time of the entire module of less than 40 ps
  • A total of 12 protective paths, consisting of six bidirectional flashover paths plus three protective paths via diodes plus three protective paths via current limiters
  • High discharge capacity and low dynamic resistance due to parallel-acting protective gaps
  • Low-impedance PE connection for uncut connection for lightning current equipotential bonding with 2.5 mm².
  • Protection level on the bus side between D+ against GND:  < 717 V (for pulse class C2,  10,000 V (1.2/50 us) / 5,000 A (8/20 us) - on the unit side, however, only for 1 µs, thereafter terminal voltage 10 V
  • Protection level on the bus side between D- against GND:  443 V (for pulse class C2,  10,000 V (1.2/50 us) / 5,000 A (8/20 us) - on the unit side, however, only for 1 µs, afterwards terminal voltage 10 V
  • Due to the combination of short response time, low protection level and fast current limiting, this protective element minimises the load on the protected devices in the RS-232-based bus system as well as on the insulation on the device side to practically zero.
  • This surge arrester for information technology systems has been certified according to IEC 61643-21-2001 + A1:2009 test C2 for "fast rising edge" and corresponds to arrester type 2.
  • Made in Germany

Intended use / scope of application / intended use:

This RS-232 surge arrester of category C2 / Type 2 according to IEC 61643-21 is intended for installation in distribution cabinets and junction boxes in dry residential and business premises, control cabinets in industry and automation systems. It serves as a surge arrester between electrical conductors of the RS-232 bus system and the equipotential bonding rail in case of direct and near lightning strikes as well as overvoltages from switching operations, and discharges the partial lightning current into the earthing system.We recommend combining it with a surge arrester for power supply networks Type 1 and Type 2 and using several of these RS-232 BlitzART modules in the system.

This module is designed for all RS-232 bus systems without restrictions.

  • Surge arrester as part of the internal lightning protection for RS-232-based bus systems
  • Arrester for overvoltages from galvanic, inductive and capacitive coupling due to near lightning (atmospheric overvoltage)
  • Arresters for overvoltages due to remote lightning strikes (e.g. in transmission networks)
  • Arresters for overvoltages due to switching operations in low, medium and high voltage networks (switching overvoltage)
  • Self-resetting, fast-acting overcurrent protection device, thus protection even against low overvoltages (e.g. 12 V on the bus-side connections in the event of incorrect wiring).

Note: This module has three protective effects, which differ depending on the connection side. The power stage acts on the bus side of the module and can equalise or dissipate 5,000 amps. Both connection sides are connected via a three-pole overcurrent protection stage. The downstream ultra-fast fine stage initially acts on both connection sides at the start of an overvoltage event, but as soon as the overcurrent protection stage is activated, the current flow between the two sides is limited so that the voltage equalisation of the fine stage only has an effect on the device side (as long as the event lasts) and drastically reduces the terminal voltage there again. For details, please refer to Function and Effect below.

  • Bus side: After the tripping of all three protection stages, the gas voltage arresters act on the bus side and equalise up to 5,000 amperes.
  • Device side: After all three protection stages have tripped, the overcurrent protection reduces the current flow between both sides to 200 mA per path, the fine stage on the equipment side now reduces the protection voltage to 10 V.

Design / Connection Recommendations:

  • Typically, installations with RS-232 are set up as serial connections between two points.
  • If only one protection module is to be used, then we recommend installing this protection module on the side with the more valuable device (usually the server). The device side points to this valuable device and is connected close to it.
  • In the case of long connections or two valuable devices, you should use two of these modules and install them antiserially (the device sides of the modules facing the devices and the bus sides facing each other).


  • PLCs, gateways, devices with RS-232: This module is compatible with all RS-232 bus systems, regardless of protocol. It can be used with all servers, PLCs, gateways and devices with this interface
  • Timberwolf Server: This module is compatible with the RS-232 interfaces on all models of Timberwolf Server.
  • Loxone Extensions: This module is compatible with the Loxone RS-232 Extension.

The capacitive load of the two data lines of the RS-232 connection by this surge arrester is approx. 400 picofarad.


  • What is the function of the BlitzART RS-232 surge arrester?
    The BlitzART RS-232 surge arrester reduces the consequences of a near and far lightning strike by quickly equalising all connected wires with each other with the lightning current potential equalisation and an almost complete interruption of the current flow between the bus and the device side of the module. This equalisation and blocking significantly reduces voltages and thus protects components and insulation of the devices and bus lines.
  • Reduced means "not complete"?
    No system in the world can offer 100% safety. However, depending on the design, it is possible to significantly reduce the probabilities of damage caused by lightning. This BlitzART RS-232 surge arrester, with its extremely short response time and low protection level, is able to provide the best available level of protection for RS-232 systems. Especially when these arresters are installed at several locations in the system. On the device side of the module, the overvoltage is practically completely eliminated. Even with a massive overvoltage of 10,000 V and 5,000 A (8/20 µs) on the bus side, the protective voltage on the device side is only 10 V at a few mA after 1 µs. This excludes any damage to the RS-232 components on the unit side.
    For maximum effectiveness of the arresters, we recommend supplementing the low-voltage part of the system with arresters for power systems type 1 and type 2 (or combination arresters type 1/2). Consult a specialist company for advice.
  • What are the planning and installation recommendations for the best protection?
    Please plan one or more modules per RS-232 bus, depending on the size of the bus system.

    Install one module in close proximity to the protection of the master system, i.e. the PLC, gateway, server or extension. Loop the RS-232 connections directly through the device side of the module to the RS-232 bus (which you connect to the bus side).

    If the bus is longer (more than 50 m), we recommend installing another module in the middle of the bus. In this case, connect the RS-232 bus only to the bus side of the module. RS-232 connections do not support branching, so do not connect devices on the device side to protective modules installed in the middle of the bus.

    For very long RS-232 connections, install another module every 50 m (normally such distances with RS-232 can only be achieved with repeaters, the BlitzART module should then protect this repeater).

    Most important additional measure: Have internal lightning protection (Type 1 and Type 2 arresters) installed for energy-technical networks.
  • The RS-232 bus can be galvanically separated from everything else as a SELV system and the lines are shielded. How can an overvoltage, a lightning strike destroy this?
    Nothing is perfect, not even foil shields. Therefore, capacitive and inductive coupling of the lightning energy is possible in principle. In addition, the insulations are designed for 4,000 V, but lightning generates voltages of up to several hundred thousand volts. This is why all insulations are at risk, especially when very close to / in contact with PE, neutral and all outer conductors. We recommend separate routing of all lines of information technology systems, as well as signal and bus lines of power supply lines. Separate metallic and closed cable trays or ducts for cable routing would be ideal.

    There is a danger with applied shielding, especially if it is applied on both sides. In the event of a nearby lightning strike, the lightning voltage is conducted through the foundation earth electrode into the building and thus to the PE of the entire building. The shield is under voltage and may also have to compensate for currents. This stresses the shield itself and the insulation inside the bus cables. This surge arrester for RS-232 has a low-impedance PE connection and compensates for potential differences. Please connect the PE connection of the protective modules to the same PE terminal block to which the shielding is connected. From this terminal block, a length of at least 2 m should be maintained to the PAS (so that purely in terms of time a type 2 arrester can switch through first).
  • What endangers the insulation?
    A lightning strike means a discharge between cloud and earth via an air gap that is conductive for a short time. Starting from the lightning channel as a current-carrying conductor, an electric field and a magnetic field are generated around it. These fields couple capacitively and inductively into conductors and conductor loops and change the potentials in all metallic conductors throughout the building. The nearby earth can only absorb part of the lightning energy. About half of the energy is conducted into the building through the foundation earth electrode via PE. Thus, in the event of a nearby lightning strike, the equipotential bonding rail and thus the entire PE via the foundation earth electrode is under a very high voltage potential of several tens of thousands of volts. These potential differences want to equalise with each other and with the distant earth in the transformer station accessible via the mains connection (and, depending on the type of mains, also with the earth of the neighbouring buildings). In order to be able to take this path, the lightning voltage also tries to pass through the insulations (depending on the network form) to the neutral and outer conductors.
  • How does this BlitzART surge arrester protect?
    The different potentials that form in metallic conductors when lightning strikes close by want to balance each other out. The equalisation takes the path of least resistance. This BlitzART surge arrester offers the surge voltage a simple path by creating a massive short-circuit almost immediately in the event of a sudden voltage increase, via which the potentials can balance each other out. The BlitzART surge arrester involves the three connected wires and PE and creates a short circuit between all four connections. This provides immediate and low-impedance compensation for the overvoltage, so that potential differences are considerably reduced and insulation and components are thus protected.
    Such an overvoltage event is already completed after twenty millionths of a second in this area of the cabling. During this short time, the components convert several thousand W of heat. A lightning bolt has an average energy of 280 kWh, about one tenth of which is converted on the ground and in the installations.
  • Why are there 11 switching, protection and flashover paths in this BlitzART surge arrester?
    Each component for surge protection has its own characteristics in terms of reaction time, voltage limitation, tripping voltage, maximum voltage, discharge capacity, heat absorption, leakage current, capacitance and polarity. There is no component that is leading in all these characteristics, often one parameter is very strong, others are less so. So that we did not have to make a compromise with this BlitzART surge arrester, we combined several components with a total of 12 protection and overvoltage paths in a three-stage cascade in such a way that components with the shortest possible reaction time complement each other with components with a high ampere discharge capacity. In this way, we achieve a level of protection that was previously impossible.
  • I have taken the board out of the module. On the bottom of the board I see nine component pins that are not soldered. Was something forgotten here?
    No, these nine pins belong to the high-current PE connection. Over the four edges of each of the nine pins, the component is homogeneously cold-welded to the through-platings of the board by a factory press fit at 36 connection points. This connection technology is mechanically very stable (pull-out force 900 N), has very low resistance (less than 200 µOhm), is permanently gas-tight and can carry high currents (500 amperes permanently). With this - and the crimp cable lug for uncut PE_connection with high cross-section - we achieve a low-impedance PE connection.
  • Are there any tips for the connection to PE?
  1. Same PE terminal blocks: If devices are protected by a surge arrester that themselves have a mains voltage connection with a protective earth conductor (for example, a power supply unit for supplying the bus master and its server) then the PE connection of the surge arrester should be the same as the PE connection of the bus master.If the PE connection of the surge arrester is routed to the equipotential bonding with the same or lower impedance than the connection of the protective earth conductor of the device to be protected to the equipotential bonding. We therefore recommend routing the PE connection of the surge arrester by the shortest route to the same PE terminal block to which the protective earth conductor of the power supply unit to be protected is connected (if it is such a power supply unit).
    The same applies if the shield of the bus cabling (usually not recommended, but may be useful in part for interference suppression) has been connected to PE. In this case, the PE of the surge arrester should be connected to the same PE terminal block to which the shield was connected. Such shield connections should be tied over the entire shield circumference with special clamps, the often braided braids are electrically unfavourable for discharges of transient overvoltages).
  2. Proper working method: Please carry out the PE connection with the utmost care. Only crimp those classes of conductors with the correct cross-section that are approved for the crimping cable lug used in each case and only use the correct crimping pliers for this (if you use the crimping cable lug supplied. please refer to the technical data). Screw the nut on the connection tightly (observe the tightening torques in the technical data). Lay the cable along the shortest path to the PE terminal block and screw the cable properly there as well (observe the terminal manufacturer's specifications, especially regarding the use of wire-end ferrules and the cross-sections permitted for this terminal). Avoid forming a spatial loop in the building at all costs (to avoid induction in the event of a lightning strike) and never wrap the PE cable around anything (do not build a coil). It is important that these connections are mechanically strong, permanently gas-tight and have the best possible contact. Please remember, this must contact safely for decades. The design of the PE is safety-critical and must be done properly and correctly according to the applicable standards. Please leave this better to an electrical installation company.
  • I have external lightning protection, do I then need this BlitzART surge arrester at all?
    Yes, absolutely. If external lightning protection ("lightning conductor") is present, additional internal lightning protection is always required (in accordance with the relevant standards). After all, the lightning is conducted from the lightning conductor directly via the foundation earth electrode into the building onto the equipotential bonding rail. From there, the overvoltage tries to pass through to all neighbouring metallic conductors with a lower potential. Only internal lightning protection prevents this by short-circuiting all metallic conductors together. This BlitzART surge arrester is an important component of such an internal lightning protection at level C2 / Type 2 and takes over this task for the connected bus and its server. This is a supplement to the coarse and medium protection according to Type 1 and Type 2, which must also be installed by an expert for lightning protection systems.
  • Isn't surge protection built into the units?
    Correct, most units have small protective diodes built in, usually consisting of a single element. These protective elements are dimensioned to pass the legally prescribed surge test. In this test, only small currents of 10 to 24 A flow for a short time. This is by far not sufficient to carry partial lightning currents. Moreover, these built-in protective elements are only effective between the BUS lines (transverse voltage), but not against PE (longitudinal voltage). This means that the insulation of the servers, PLC, power supply and bus lines is not protected. In most cases, in the event of a direct or near lightning strike, the overvoltage is conducted through PE (and possibly via the outer conductors) into the building. Therefore, for optimum protection of the insulation and components, all lines must be balanced with each other and with PE so that all system components are at the same potential. This BlitzART surge arrester can dissipate about fifty times what small protective diodes in devices can achieve - plus also towards PE.
  • When does the BlitzART surge arrester trigger?
    The fine stage starts to conduct from about 28 V, the gas voltage arresters ignite from about 150 V and a rate of voltage rise that is typical for overvoltage events with a correspondingly steep rising edge. The overcurrent limiters are effective from 200 mA.
  • Is a BlitzART surge arrester destroyed by lightning?
    No, usually not, this module is capable of carrying lightning currents up to 5,000 amperes. If this should ever happen, please let us know, we will certainly find a very accommodating compensation.


Surge arrester type 2 for RS232 with three-stage protection system with disconnection of the current flow to the equipment side.

This surge arrester can discharge 5,000 amperes (8/20 µs, pulse category C2, fast rising edge). In addition, this protection system is equipped with the innovative ElabNET Current-Cut technology (self-resetting high-speed fuse 1µs). This enables additional protection even against low overvoltages (e.g. short-circuit with 48 V due to wiring errors).

This BlitzART protection system is thus a combined protection system consisting of a very powerful type 2 surge arrester plus a very sensitive overcurrent protection (200 mA / 1 µs). Within one microsecond, the overcurrent protection switches off a possible damaging current to the unit side which could still occur due to the remaining protection level of the other two stages. The reset after the overcurrent event occurs automatically within one millisecond.

This short-circuits overvoltages, compensates potential differences and additionally separates remaining overcurrents. Due to this special combination, the achievable equipment protection is at least ten times better compared to conventional protection systems without this third protection level.

Overview of the protection technologies included

  • Protection scope: Threestage protection of the connected devices and power supplies as well as the insulation of lines against overvoltage from near and far lightning strikes, against overvoltages caused by switching operations as well as protection between bus and device side against overcurrent already from 200 mA. This also limits equipotential bonding currents via bus and (especially) GND lines.
  • Total number of protection sections: 12 protection and flashover sections
  • Number of gas voltage arresters: Six flashover paths via two double-chamber gas voltage arresters (specified by the manufacturer with up to 20,000 amperes)
  • Number of diodes / TVS diodes: A total of three bidirectional TVS diode protection paths (reaction time a few dozen picoseconds)
  • Number of current limiters: Three overcurrent protection paths with fast, self-resetting current limiters (limiting in 1 µs, resetting 1 ms)
  • Type of surge arrester: Type 2
  • Certified current discharge: 5,000 amps at 8/20 µs (increased current load according to pulse class C2, fast rising edge).
  • Low impedance PE connection: PE connection with particularly low contact resistance, pre-assembled with washers, spring washer, nut and crimped cable lug for uncut connection to equipotential bonding up to 2.5 mm².
  • Overcurrent protection: Current-cut technology, based on three ultra-fast, self-resetting fuses in all line paths, tripping already at 200 mA within 1µs, disconnects the connection between bus and device side of the module
  • Automatic reset: Restoration of the connection between bus and device side within 1 ms after the overvoltage or overcurrent event.
  • PE connection: Pre-assembled with washers, spring washer, nut and crimp cable lug (DIN 46234) for connection to equipotential bonding up to 2.5 mm².

Operating range

  • Rated voltage / Highest continuous voltage D+ against GND: -25 V to +25 V
  • Rated voltage / Maximum continuous voltage D- to GND: -25 V to +25 V
  • Leakage current D+ to GND:  1 uA
  • Leakage current D- to GND:  1 uA
  • Leakage current D+ to D-:  1 uA
  • Insulation resistance at nominal voltage:100 MOhm
  • Capacitance D+ to GND: 400 pF
  • Capacitance D- against GND: 400 pF

Protection level (for overvoltage 10,000 V and 5,000 Amps)

  • Data lines, D+ against GND: 717 V (for pulse class C2) 10,000 V (1.2/50 us) / 5,000 A (8/20 us)
  • Data lines, D- against GND: < 443 V (for pulse class C2,  10.000 V (1,2/50 us) / 5.000 A (8/20 us)
  • Current limitation: The remaining damaging current from the protection level is switched off by current cut after 1 µs.
  • Pulse recovery, D+ against GND: <1.09 ms (measured at 2000 V (1.2/50 us) / 1,000 A (8/20 us)
  • Pulse recovery, D- against GND: <0.93 ms (measured at 2000 V (1.2/50 us) / 1,000 A (8/20 us)

Test standards and certification

  • Certification: According to EN 61643-21:2001 + A1:2009 + A2:2013: according to pulse class C2 at 10 kV (1.2/50 us) / 5 kA (8/20 us).
  • Test laboratory: DEHN Prüf- und Testzentrum, Neumarkt, accredited according to DIN EN ISO/IEC 17025:2018 by the German Accreditation Body DAkkS.

Connections Bus side

  • Bus: Triple plug-in terminal block Wago 243 with four connections per potential and test opening.
  • Permissible conductor class: solid conductor with diameter 0.6 - 0.8 mm (conductor class 1 according to DIN/IEC 60228)
  • Stripping length: 5-6 mm
  • Overvoltage protection:The overvoltage protection by short-circuiting acts against the bus side of the module or PE, the device side is additionally disconnected by the overcurrent protection.

Connections on the unit side

  • Bus: Triple plug-in terminal Wago 243 with four connections each per potential and test opening
  • Permissible conductor class: solid conductor with diameter 0.6 - 0.8 mm (conductor class 1 according to DIN/IEC 60228)
  • Stripping length: 5-6 mm
  • Overcurrent protection: The current-cut overcurrent protection limits the current between the bus side and the device side of the module.

Potential equalisation connection

  • PE connection: Low-impedance connection between module and lightning current equipotential bonding by cold-welded connection terminal, spring-loaded screw connection, gas-tight crimped cable lug and uncut cable routing with 2.5 mm².
  • Connection terminal: Terminal with very high current carrying capacity, best long-term reliability due to permanently gas-tight connection of the terminal to the assembly by 36 homogeneously cold-welded contact points with a pull-out force of 900 N, thereby low-resistance contact resistance with < 200 µOhm,
  • Screw connection: pre-assembled connection with washers, spring lockwasher, nut and crimping cable lug (acc. to DIN 46234)
  • Crimpable conductor class: stranded, fine-stranded and finest-stranded conductors with 2.5 mm² (recommendation: H07V-K2.5 gn/ge; conductor classes 2, 5 and 6 according to DIN/IEC 60228).
  • Crimping pliers: Please use crimping pliers for uninsulated crimping cable lugs according to DIN/IEC 46234.
  • Stripping length: 5 mm
  • Connection thread: M3
  • Maximum tightening torque: 0.5 Nm
  • Breaking torque set screw: 1.5 Nm
  • Notes for larger cross-sections: The crimping cable lug can be exchanged by you, thus a larger cross-section or connection of solid conductors is possible.

Protection class Module

  • Protection class: III / SELV (according to EN60730)
  • Protection class: IP 00 (according to EN 60529)


  • Construction: Open REG housing
  • Mounting: This surge arrester is intended for fixed mounting on the top-hat rail in distribution boards inside buildings (DIN Rail 35 mm according to EN 50022).
  • Ambient temperature: -20°C to +70 °C
  • Humidity: 98% rH (without condensation)
  • Mounting: DIN Rail 35 mm (EN50022)
  • Material housing: Polyamide
  • Colour: Green
  • Dimensions: 76 mm x 22.5 mm x 40 mm (l x w x h with housing)
  • Weight: 39 g (with housing)