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 489-6

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

NEW! Very low protection level of only 220V / 370 V (approx. 1/4 compared to conventional single-stage arresters)
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 protection and flashover paths for optimum arresters

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

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



  • Low protective voltage: Two-stage module for optimum protection of your KNX components in case of overvoltage events
  • KNX-TP or auxiliary voltage: The same module can be used for KNX bus or KNX auxiliary voltage, both terminal sets included.
  • Solid protective earth connection: PE connection with low impedance that allows uncut routing.



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. DIN / IEC 61643certified lightning and surge protection system, tested for use in KNX-TP bus systems.



In the video linked below, we explain this protection module for KNX-TP and KNX auxiliary voltage and offer you background knowledge on overvoltages and protection systems. You can also jump to these chapters by marking YouTube.

  • 00:00 Welcome and announcement of the sales campaign (this was 2018).
  • 01:46 How does a surge protector work, specifically for protecting bus systems and equipment?
  • 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 action referred to in the video was in summer 2018 and is no longer active. The technical information is unaffected.




  • Area of application: Two-stage surge arrester for protecting the KNX installation (system devices, actuators, sensors, insulation of bus lines)
  • Protection levels: Innovative two-stage protection with combination of short response time and high discharge capacity for best protection level
  • PE connection: Low-impedance PE connection for uncut connection for lightning current equipotential bonding with 2.5 mm².
  • Protectionlevel rt / sw: < 220 V at C2 with 1 kA (this is about a quarter compared to conventional single-stage arresters)
  • Protection level sw / PE: < 220 V at C2 with 1 kA (this is about a quarter compared to conventional single-stage arresters)
  • Protection level rt / PE: < 370 V at C2 with 1 kA (this is about one half compared to conventional single-stage arresters)
  • Overall protection: 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 one-twentieth compared to conventional single-stage protection elements.
  • Certification: 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).
  • KNX Partner: Specially developed for KNX-TP and KNX auxiliary voltage, manufactured and tested by us, we are a KNX manufacturer.
  • Made in Germany


  • Protection of KNXpower 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 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 KNX IP interfaces / routers: We recommend a protection module just before the KNX TP connections of KNXnet/IP interfaces and KNXnet/IP routers, if 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 the 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% safety. 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 reaction time and low protection level of 220 / 370 V at 1 kA, is able to offer a very high level of protection for KNX systems, especially if they are installed at several points in the system. We assume a protection level that is 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.
  • 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 lightning energy is possible. Although insulations are designed for 4,000 V, lightning generates voltages of up to several hundred thousand volts. For this reason, insulations are at risk, especially if they are very close to / come into 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 routing cables are ideal for this.

    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 into the house through the foundation earth electrode and thus to 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 protective module directly to the KNX-TP and auxiliary voltage connections of all KNX power supplies. Please connect the PE connection of these two protective modules to the same PE terminal block to which the PE connection of the KNX power supply is connected.
  • What endangers the insulation?
    Ein Blitzschlag bedeutet eine Entladung zwischen Wolke und Erde über eine Luftstrecke, die kurzzeitig leitfähig ist. Ausgehend von dem Blitzkanal als stromdurchflossener Leiter wird ein elektrisches und ein magnetisches Feld um diesen herum erzeugt. Diese Felder koppeln kapazitiv und induktiv in Leitungen und Leiterschleifen ein und ändern die Potentiale in allen metallischen Leitern im gesamten Gebäude. Die nahe Erde kann nur einen Teil der Blitzenergie aufnehmen. Etwa die Hälfte der Energie wird durch den Fundamenterder über PE in das Gebäude geleitet. Damit steht bei einem nahen Blitzschlag die Potentialausgleichsschiene und damit der gesamte PE über den Fundamenterder unter einem sehr hohen Spannungspotential von mehreren zehntausend Volt. Diese Potentialunterschiede wollen sich untereinander und zur fernen Erde in der über den Netzanschluss erreichbaren Trafostation (und je nach Netzform auch zur Erde der benachbarten Gebäude) hin ausgleichen. Um diesen Weg nehmen zu können, versucht die Blitz

    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 outer conductor, 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 its connections to the low-voltage network. In addition, if the shield of KNX bus cables is connected to the PE, this shield is subjected to lightning voltage via the PE in the event of a close lightning strike. From there, the overvoltage can seek 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 during a close lightning strike want to equalise. The equalisation takes the path of least resistance. The BlitzART KNX surge arrester offers the overvoltage a simple path by creating a massive short-circuit almost immediately in the event of a sudden voltage increase, via which the potentials can equalise. The BlitzART KNX surge arrester involves the two connected KNX cores and PE and creates a short-circuit between all three connections. This offers the overvoltage an immediate and low-impedance equalisation, so that potential differences are considerably reduced and insulation and components are thus protected.
    Such an overvoltage event is completed in this area of the cabling after twenty millionths of a second. 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-connected mode.
  • Why was this BlitzART KNX surge arrester designed with five switching and surge paths?
    Each component for surge protection has its own characteristics with regard to 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 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 on 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. Has something been 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 an interference fit in the factory with a total of 36 connection points. This connection technique is mechanically very stable (pull-out force 900 N), at the same time very low-impedance (less than 200 µOhm), permanently gas-tight and can carry high currents (500 amps permanently). With this - and with the crimped 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. Same PE terminal blocks: If devices are protected by a surge arrester that themselves have a mains voltage connection with protective earth conductor (for example KNX power supplies, actuators with mains voltage connection), then the PE connection of the surge arrester should be 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 on the shortest path 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 partially useful for interference suppression) has been connected to PE. In this case, the PE of the surge arrester should be routed to the same PE terminal block to which the shield has been connected. Such shield connections should be tied over the entire shield circumference with special clamps; the often braided braids are electrically unfavourable for discharging transient overvoltages).
  2. Ordentliche Arbeitsweise: Führen Sie den PE-Anschluss bitte mit größter Sorgfalt aus. Verquetschen Sie ausschließlich diejenigen Leiterklassen im richtigen Querschnitt, die für den verwendeten Quetschkabelschuh jeweils zugelassen sind und verwenden Sie hierfür auch die korrekte Quetschzange (wenn Sie den mitgelieferten Quetschkabelschuh verwenden. lesen Sie bitte in den technischen Daten nach). Schrauben Sie die Mutter am Anschluss gut fest (Anzugsmomente in den technischen Daten beachten). Verlegen Sie die Leitung auf dem kürzesten Weg zum PE-Klemmenblock und schrauben Sie die Leitung auch dort ordentlich fest (Angaben des Klemmenherstellers beachten, insbesondere zum Gebrauch von Adernendhülsen und zu den für diese Klemme erlaubten Querschnitte). Vermeiden Sie unbedingt eine räumliche Schleife im Gebäude zu bilden (um Induktion bei Blitzschlag zu vermeiden) und wickeln Sie keinesfalls die PE Leitung um etwas herum (keine Spule bauen). Es ist wichtig, dass diese Anschlüsse mechanisch fest, dauerh
  • I have external lightning protection, do I 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 (according to the corresponding 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 an internal lightning protection prevents this by short-circuiting all metallic conductors with each other. This BlitzART KNX surge arrester is an important component of such an internal lightning protection on the Type 3 level and takes over 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, and which must be installed by an expert for lightning protection systems.
  • KNX devices have built-in surge protection, is a separate arrester necessary?
    Richtig, in den meisten Geräten sind kleine Schutzdioden eingebaut, üblicherweise bestehend aus einem einzigen Element. Diese Schutzelemente sind für das Bestehen des gesetzlich vorgeschriebenen Surge-Tests dimensioniert. In diesem Test fließen kurzzeitig geringe Ströme von 10 bis 24 A. Das ist bei weitem nicht ausreichend, um Blitzteilströme zu tragen. Zudem wirken diese eingebauten Schutzelemente nur zwischen den BUS-Leitungen (Querspannung), jedoch nicht gegenüber PE (Längsspannung). Nur hiermit würden die Isolationen der KNX Spannungsversorgung und der Busleitungen nicht geschützt. In den meisten Fällen wird bei direktem oder nahem Blitzschlag die Überspannung durch PE (und womöglich die Außenleiter) in das Haus geführt. Daher muss für optimalen Schutz der Isolierungen und Bauteile ein Ausgleich aller Leitungen untereinander ("Querspannung") und auch mit PE ("Längsspannung") erfolgen, damit sich alle Anlagenbestandteile auf dem gleichen Potential befinden. Dieser BlitzART KNX Überspannun
  • When does the BlitzART KNX surge arrester trip?
    Above approx. 150 V and a rising speed of the voltage that is typical for overvoltage events with a correspondingly steep rising edge.
  • Is a BlitzART KNX surge arrester destroyed by lightning?
    No, this has never happened. If this should ever happen, let us know, we will certainly find a very accommodating compensation.



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 about twenty times compared to conventional single-stage surge arresters.

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 near lightning strikes and discharges the partial lightning current into the earthing system.We recommend combining it with a surge arrester for energy networks Type 1 and Type 2 and using several of these KNX BlitzART modules in the KNX system.

  • Surge protection device as part of the internal lightning protection for KNX bus systems
  • Arresters for overvoltages from galvanic, inductive and capacitive coupling as a result of close lightning strikes (atmospheric overvoltages).
  • 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 in particular 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.

Overview of the included protection technologies

  • Scope of protection: 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 from switching operations, including equipotential bonding (three connected conductors).
  • Total number of flashover arresters: Five bidirectional protection and flashover arresters 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 µA
  • Insulation resistance at nominal voltage: > 2.4 MOhm
  • Capacitance rt / sw: 1 nF
  • Capacitancert / 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)
  • Datalines, sw / PE: < 220 V (for pulse class C2, 1,000 A (8/20 us)
  • Data lines, rt / PE: < 370 V (for 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, thus low 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 use only crimping pliers for uninsulated crimping cable lugs according to DIN/IEC 46234.
  • Stripping length: 5 mm
  • Connection thread: M3
  • Maximum tightening torque: 0.5 N m
  • Breaking torque of grub screw: 1.5 N m

Notes on using other crimping cable lugs: Instead of the crimping cable lug supplied, you can also use other crimping cable lugs if you want to connect with a larger cross-section or want to use a solid conductor. Pay attention to the hole for M3. Crimping cable lugs with 4 and 6 mm² are available commercially for this purpose. Please ensure that you use the correct crimping pliers 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 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)


<h1 style="box-sizing: border-box; margin-top: 0px; margin-bottom: 0.5rem; line-height: 1.1; font-size: 1.8rem; font-family: Custom-Font, Lato, sans-serif; letter-spacing: 0.5px; background-color: rgb(255, 255, 255);"><span style="font-size:24px;"><span style="box-sizing: border-box; color: rgb(85, 85, 85);"><span style="box-sizing: border-box;">SCOPE OF DELIVERY</span></span></span></h1> <p style="box-sizing: border-box;"><br /><span style="box-sizing: border-box; font-weight: bolder;">12 x Art-No: 489:</span>&nbsp;Surge arrester for KNX-TP and auxiliary voltage - 1000 Amp (Type 3)</p> <p style="box-sizing: border-box;">&nbsp;</p> <ul> <li><span style="color:#0d47a1;"><strong>Execution:</strong></span> Module with open REG housing</li> <li><strong><span style="color:#0d47a1;">For mounting on DIN top-hat rail:</span></strong> Ready mounted with base for top hat rail</li> <li><strong><span style="color:#0d47a1;">Connection terminals:</span></strong> TWO sets of terminals for KNX-TP as well as KNX auxiliary voltage (two pairs each of rt/sw and ge/ws bus terminals)</li> <li><strong><span style="color:#0d47a1;">PE connection:</span></strong> Pre-assembled with washers, spring lockwasher, nut and crimp connector for 2.5 mmu00b2.</li> <li><strong><span style="color:#0d47a1;">Number of pieces according to order, please also note our SparPacks and SuperSparpack</span></strong></li></ul>