Surge arrester for KNX-TP and auxiliary voltage - 1000 amps (type 3)


Surge arrester for KNX-TP and auxiliary voltage - 1000 amps (type 3)

Item number 489

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Suitable for protection of Timberwolf Server, Loxone Miniserver, KNX power supply, KNX line amplifier, KNX line coupler, KNX area coupler, KNX USB interface, KNXnet/IP Tunneling IP Interface and KNXnet/IP Router and all KNX devices. According to DIN / IEC 61643 zertified lightning and surge protection system, tested for use in all KNX-TP bus systems.

Newly designed surge protection element with two protection levels. The protective cascade combines a high discharge capacity with a particularly short response time, resulting in a low protective voltage. Compared to conventional KNX surge arresters, up to 20 times better protection is achieved for the connected KNX devices.

NEW!  Very low protection level of only 220V / 370 V
NEW!  Fast response from 40 ps (approx. 1,000 times faster than conventional single-stage arresters)
NEW!  Combination of two stages with a total of five protective and flashover paths for optimum discharge

NEW!  PE connection with very low contact resistance for uncut and low-impedance connection with 2.5 mm² to lightning current equipotential bonding
NEW!  Including two terminals each rt/sw and ge/ws for use with KNX-TP or KNX auxiliary voltage



In the video we explain this surge protection for KNX-TP and KNX auxiliary voltage. The chapters in the video are:

  • 00:00 Welcome and announcement of the sales campaign (this was 2018).
  • 01:46 How does a surge protector work, especially for the protection of bus systems and devices?
  • 04:55 Important key figures for the evaluation of a surge protector
  • 09:08 Energy content of a lightning strike
  • 10:28 Conventional surge protection for KNX, response times, protective voltage, limitations
  • 14:22 What does the innovative new generation BlitzART KNX surge protection do better?
  • 17:57 How great is the danger from lightning for bus systems and devices?
  • 19:14 Announcement of further BlitzART modules for RS-485, CAN, RS-232, 1-Wire
  • 19:38 Installation recommendations for KNX surge protection

Note: The promotion mentioned in the video was in summer 2018 and is no longer active. The technical specifications are unaffected.




  • Design: Module with open REG housing
  • Mounting on DIN rail: Fully assembled with base for DIN rail
  • Terminals: TWO sets of terminals for KNX-TP and KNX auxiliary voltage (two pairs each of rt/sw and ge/ws bus terminals)
  • PE connection: Pre-assembled with washers, spring washer, nut and crimp connector for 2.5 mm².



  • Multi-stage surge arrester for protecting the KNX installation (system devices, actuators, sensors, insulation of bus lines).
  • Innovative two-stage protection with combination of short response time and high discharge capacity for best protection level
  • Low-impedance PE connection for uncut connection for lightning current equipotential bonding with 2.5 mm².
  • Protection level between core rt / sw at C2 with 1 kA: only 220 V (this is about a quarter compared to conventional single-stage arresters)
  • Protection level between core sw / PE at C2 with 1 kA; only 220 V (this is about a quarter compared to conventional single-stage arresters)
  • Protection level between core rt / PE at C2 with 1 kA: only 370 V
  • Due to the combination of short response time and low protection level, this surge arrester minimises the load on connected KNX devices and all insulation to about 1/20th compared to conventional single-stage protection elements.
  • This surge arrester for information technology systems has been certified according to IEC 61643-21-2001 + A1:2009 test C2 for "fast rising edge" (corresponds to type 3).
  • Specially developed for KNX-TP and KNX auxiliary voltage, manufactured and tested by us. We are KNX manufacturer.
  • Made in Germany

Intended use / area of application / intended use:

This KNX surge arrester of category C2 (comparable to Type 3) 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 KNX bus system and the equipotential bonding rail in the event of direct and close lightning strikes and discharges the partial lightning current into the earthing system.We recommend the combination with a surge arrester for power supply networks Type 1 and Type 2 as well as the use of several of these KNX BlitzART modules in the KNX system.

  • Surge protection device as part of the internal lightning protection for KNX bus systems
  • Arrester for overvoltages from galvanic, inductive and capacitive coupling due to close lightning strike (atmospheric overvoltage)
  • Arresters for overvoltages due to distant lightning strikes (e.g. in transmission networks)
  • Arrester for overvoltages due to switching operations in low, medium and high voltage networks (switching overvoltage)
  • Protects the insulation and electronics of KNX power supplies, line and area couplers, all connected bus devices and the insulation of the bus cabling by compensating and discharging overvoltages.
  • Extended protection in case of distributed installation of several such surge arresters in the bus system by multiple connection of the KNX installation to the equipotential bonding (such a connection is only made for a short time to compensate for the overvoltage)

This module has no functional direction, the connected bus lines and devices are equally protected on both sides of the surge protection module. When the bus signal is passed through the module, the reaction is slightly faster; we recommend connecting the more sensitive KNX devices on the side with the shorter bus line.

Design recommendations:

  • Protection of the KNX power supply: We recommend installation directly parallel to the power supply (for KNX-TP and auxiliary voltage, if used) to protect the insulation of the AC/DC converter in the KNX power supply.
  • Protection of the KNX system devices: If line amplifiers, line couplers or area couplers are installed that are connected more than 20 m away from a protected KNX power supply, we recommend a second protection module in front of the component. This protects these system devices and their insulation between the bus connections.
  • Protection of the KNX IP interfaces / routers: We recommend a protective module just before the KNX TP connections of KNXnet/IP interfaces and KNXnet/IP routers, as long as the distance from the respective protected KNX power supply exceeds 20 metres.
  • Protection of KNX servers: A protection module in series before the KNX TP connection of servers such as Timberwolf Server, TP-UART, Loxone Miniserver, Loxone KNX Extension, etc.
  • Recommendation: Additionally at all transition points between two protection zones (floor passage, lines to outbuildings and gardens).


  • KNX-TP: Compatible with KNX-TP for all bus lines and KNX devices.
  • KNX auxiliary voltage: Compatible with KNX auxiliary voltage for all bus lines and KNX devices.
  • Timberwolf Server: Compatible with KNX-TP connection on Timberwolf Server or TP-UART modules.
  • WireGate Server: Compatible with KNX-TP connection to TP-UART modules.
  • Loxone Miniserver 1: Compatible with KNX-TP connection on Loxone Miniserver 1
  • Loxone Miniserver 2: Compatible with KNX-TP connection to KNX Extension, connected via Lox Link to Loxone Miniserver. For the protection of LOX Link we recommend our surge arresters for CAN bus.

The capacitive load of the KNX bus by this surge arrester is 1 nF, which corresponds approximately to the capacitive load of 10 m bus line.



  • What is the function of the BlitzART KNX surge arrester?
    The BlitzART KNX surge arrester reduces the consequences of a near and far lightning strike by quickly equalising all connected cores with each other with the lightning current equipotential bonding. This equalisation reduces voltages and thus protects components and insulation of the KNX devices and the KNX bus lines.
  • Reduced means "not complete"?
    No system in the world can offer 100% security. However, depending on the design, it is possible to greatly reduce the probabilities of damage caused by lightning. This BlitzART KNX surge arrester, with its short response time and low protection level of 220 / 370 V at 1 kA, is able to provide a very high level of protection for KNX systems. Especially when these are installed at several points in the system. We assume a protection level about 20 times better than conventional single-stage arresters. For maximum effectiveness, we recommend supplementing the low-voltage part of the system with arresters for power systems type 1 and type 2 (or combination arrester type 1/2). Please consult a specialist company for advice.
  • As a SELV system, the KNX is electrically isolated from everything else and the lines are shielded. How can an overvoltage or lightning strike destroy this?
    Nothing is perfect, not even foil shields. In principle, capacitive and inductive coupling of the lightning energy is possible. Although insulations are designed for 4,000 V, lightning generates voltages of up to several hundred thousand volts. Insulations are therefore at risk, especially if they are very close to / in contact with PE, neutral and all external conductors. We recommend routing all cables of information technology systems separately from power supply cables. Closed metallic cable trays or ducts for cable routing are ideal for this purpose.

    A further danger arises from the PE-connected protective conductor of KNX power supplies and in the case of applied shielding. In the event of a nearby lightning strike, the lightning voltage is conducted through the foundation earth electrode into the building and thus onto the PE of the entire building. This stresses the insulation within the power supply or bus lines. This KNX surge arrester has a low-impedance PE connection and compensates for potential differences. Connect this protection module directly to the KNX-TP and auxiliary voltage connections of all KNX power supplies. Please connect the PE connection of these two protection modules to the same PE terminal block to which the PE connection of the KNX power supply is connected.
  • 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 tries to pass through the insulations (depending on the network form) to the neutral and outer conductors.

    With regard to KNX, the lightning voltage also tries to pass through the insulation within the KNX power supply between the PE connection and the connections for neutral and phase conductors, which can destroy the KNX power supply. Although the KNX bus system is insulated with 4,000 V against all other lines and systems, this voltage is easily exceeded by the usual lightning voltages. On its way to the remote earth, the current destroys electronic components.

    The same applies to longitudinal voltages from KNX-TP and auxiliary voltage connections through the KNX power supply to their connections to the low-voltage network. In addition, if the shield of KNX bus cables is connected to PE, this shield is subjected to lightning voltage via the PE in the event of a nearby lightning strike. From there, the overvoltage can find its way through the core insulation and the insulation of the KNX power supply to its low-voltage connection and from there to the remote earth.
  • How does this BlitzART KNX 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. The BlitzART KNX 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 KNX surge arrester involves the two connected KNX wires and PE and creates a short circuit between all three 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 completed after twenty millionths of a second in this area of the wiring. 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. With the completion of the event, the components switch back to the non-switched-through mode.
  • Why was this BlitzART KNX surge arrester designed with five switching and surge paths?
    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 didn't have to make a compromise with this BlitzART KNX surge arrester, we combined several components with a total of five switching and surge paths in a cascade in such a way that components with the shortest possible reaction time complement each other with components with a high discharge capacity of up to 20,000 amperes once. By combining two stages, the maximum voltage at the bus is limited to approx. 220 / 370 V at 1,000 A in the standard test according to C2 (rapid rise).
  • I have removed the assembly from the module. On the underside 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 means of a factory press fit with a total of 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 with the crimp cable lug for uncut PE_connection with large cross-section - we achieve a low-impedance PE connection.
  • Are there any recommendations for the connection to PE?
  1. Equal PE terminal blocks: If a surge arrester protects devices that themselves have a mains voltage connection with a protective earth conductor (for example KNX power supplies, actuators with mains voltage connection) then the PE connection of the surge arrester should be the same.If the PE connection of the surge arrester is routed to the equipotential bonding with the same or a lower impedance than the connection of the protective earth conductor of the device to be protected to the equipotential bonding. We therefore recommend that the PE connection of the surge arrester be routed by the shortest route to the same PE terminal block to which the protective earth conductor of the device to be protected is connected.
    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. Crimp only those classes of conductors with the correct cross-section that are approved for the crimping cable lug used in each case and also 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 KNX surge arrester at all?
    Yes, absolutely. If there is an external lightning protection ("lightning conductor"), an 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 KNX surge arrester is an important component of such an internal lightning protection on level Type 3 and performs this task for the KNX bus and the KNX auxiliary voltage. 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.
  • KNX devices have built-in surge protection, is a separate arrester necessary?
    Correct, most devices 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, low currents of 10 to 24 A flow for a short time. This is by far not sufficient to carry partial lightning currents. In addition, these built-in protective elements are only effective between the BUS lines (transverse voltage), but not against PE (longitudinal voltage). Only this would not protect the insulation of the KNX power supply and the bus lines. In most cases, in the event of a direct or near lightning strike, the overvoltage is conducted into the house through PE (and possibly the outer conductors). Therefore, for optimum protection of the insulation and components, all lines must be equalised with each other ("cross voltage") and also with PE ("longitudinal voltage") so that all system components are at the same potential. This BlitzART KNX surge arrester can dissipate about fifty times what the protective diodes in the KNX devices themselves can do - plus also with respect to PE.
  • When does the BlitzART KNX surge arrester trip?
    Above about 150 V and a rate of voltage rise that is typical for overvoltage events with a correspondingly steep rising edge.
  • Is a BlitzART KNX surge arrester destroyed by lightning?
    No, usually not.



Surge arrester C2 for the KNX bus system with two-stage arrester system for optimum device protection.

This surge arrester has been certified for 1,000 amperes (8/20 µs) in pulse category C2, fast rising edge.

The two-stage BlitzART protection system is a cascaded protection consisting of a powerful and a fast surge arrester. This cascading improves the achievable equipment protection by a factor of about twenty compared to conventional single-stage surge arresters.

Overview of the included protection technologies

  • Protection scope: Two-stage protection of the connected devices and power supplies as well as the insulation of lines against overvoltage from near and far lightning strikes as well as against overvoltages caused by switching operations, including equipotential bonding (three connected conductors).
  • Total number of flashover paths: Five bidirectional protection and flashover sections for the equalisation of transverse and longitudinal voltages.
  • Number of gas voltage arresters: Three flashover paths via double-chamber gas voltage arresters (specified by the manufacturer as 20,000 amperes).
  • Number of TVS diodes: Two protective paths via bidirectional TVS protective diodes (reaction time of the PN transition specified by the manufacturer as 1 ps)
  • Type of surge arrester: C2 for information technology systems (corresponds to Type 3)
  • Certified current discharge: 1,000 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 crimping cable lug for uncut connection to equipotential bonding up to 2.5 mm².
  • Short reaction time: Reaction of the entire module, depending on the connection to the KNX bus, from 0.04 nanoseconds.

Operating range

  • Rated voltage: 28 V
  • Rated current: 6 A
  • Maximum continuous voltage: 48 V
  • Leakage current:  10 uA
  • Insulation resistance at rated voltage: > 2.4 MOhm
  • Capacitance rt / sw: 1 nF
  • Capacitance rt / PE: 0.5 nF
  • Capacitance sw / PE: 1 nF

Protection level (at 1,000 amps)

  • Data lines, sw / rt: 220 V (at pulse class C2) 1,000 A (8/20 us)
  • Data lines, sw / PE: < 220 V (for pulse class C2,  1.000 A (8/20 us)
  • Data lines, rt / PE: < 370 V (at pulse class C2,  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 1,000 amps (8/20 µs).
  • Test laboratory: Pulse and high current laboratory PHOENIX CONTACT, Blomberg; accredited according to DIN EN ISO / IEC 17025:2018 by the German Accreditation Body DAkkS with certificate DAkkS: D-PL-12161-03-00


  • Connections: On both sides with double plug-in terminal Wago 243 with four connections per potential, including 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
  • No polarity / functional direction: The module protects bus and devices equally on both sides

Potential equalisation connection

  • PE connection: Low-impedance connection between module and lightning current equipotential bonding through cold-welded connection terminal, spring-loaded screw connection, gas-tight crimp 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 washer, nut and crimp cable lug (according to DIN 46234)
  • Crimpable conductor class: For the supplied crimp cable lug, please use only stranded, fine-stranded or fine-stranded conductors with 2.5 mm² (conductor classes 2, 5 and 6 according to DIN/IEC 60228, our recommendation: H07V-K2.5 gn/ge).
  • Crimping pliers: For the supplied crimping cable lug, please only 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 on using other crimp terminals: Instead of the supplied crimping cable lug, you can also use others if you want to connect with a larger cross-section or use a solid conductor. Pay attention to the hole for M3. Crimping cable lugs with 4 and 6 mm² are available in the trade for this purpose. Please make sure to use the correct crimping tool for the respective crimping cable lug.

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 distributions 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)