{"id":4523,"date":"2026-09-15T15:13:10","date_gmt":"2026-09-15T07:13:10","guid":{"rendered":"https:\/\/cnkuangya.com\/?p=4523"},"modified":"2026-09-15T15:13:26","modified_gmt":"2026-09-15T07:13:26","slug":"spd-backup-fuse","status":"publish","type":"post","link":"https:\/\/cnkuangya.com\/de\/blog\/spd-backup-fuse\/","title":{"rendered":"Ben\u00f6tigt ein \u00dcberspannungsschutzger\u00e4t (SPD) eine Vorsicherung oder einen Leitungsschutzschalter? Ein praktischer Auswahlleitfaden"},"content":{"rendered":"<p class=\"wp-block-paragraph\">Ein \u00dcberspannungsschutzger\u00e4t sch\u00fctzt elektrische Anlagen vor transienten \u00dcberspannungen, aber was sch\u00fctzt das SPD, wenn ein interner Fehler oder Kurzschluss auftritt?<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Hier kommt die <strong>SPD-Vorsicherung oder der Leitungsschutzschalter<\/strong> ins Spiel.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Es gibt jedoch keine allgemeing\u00fcltige Regel wie:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\">\u201cJeder Typ-2-Ableiter ben\u00f6tigt eine 125-A-Sicherung.\u201d<\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">oder:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\">\u201cEin 40-kA-\u00dcberspannungsschutzger\u00e4t (SPD) sollte mit einem 40-A-Leitungsschutzschalter abgesichert werden.\u201d<\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">Beide Aussagen k\u00f6nnen falsch sein.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Richtig <strong>Vorsicherung f\u00fcr \u00dcberspannungsschutzger\u00e4te (SPD)<\/strong> Die Auswahl h\u00e4ngt vom genauen SPD-Modell, dem vorgeschalteten \u00dcberstromschutz, dem prospektiven Kurzschlussstrom, dem Leiterquerschnitt, der Systemkonfiguration und den Herstellerangaben ab.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Einige SPDs k\u00f6nnen \u00fcber die vorhandene vorgeschaltete Sicherung oder den Leitungsschutzschalter abgesichert werden. Andere erfordern einen separaten Vorsicherungsschutz. Manche Produkte haben den Vorsicherungsschutz sogar bereits im SPD integriert.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Die wichtigste Regel ist daher einfach:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>Do not select an SPD backup fuse only from the SPD&#8217;s In, Imax or Type classification. Always check the manufacturer&#8217;s declared backup protection and the actual installation conditions.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Kurze Antwort: Ben\u00f6tigt ein \u00dcberspannungsschutzger\u00e4t (SPD) eine Vorsicherung?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Ein SPD ben\u00f6tigt m\u00f6glicherweise eine Vorsicherung oder einen Leitungsschutzschalter, aber nicht jede Installation erfordert eine separate Absicherung.<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If the existing upstream overcurrent protective device already satisfies the SPD manufacturer&#8217;s permitted protection arrangement, an additional backup fuse may not be required.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If the upstream protective device exceeds the manufacturer&#8217;s permitted value, or if the SPD instructions specify dedicated branch protection, an additional <strong>SPD-Vorsicherung oder der Leitungsschutzschalter<\/strong> Absicherung erforderlich sein.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Das bedeutet, die richtige Frage lautet nicht einfach:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\">\u201cWelche Sicherungsgr\u00f6\u00dfe sollte ich installieren?\u201d<\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">Fragen Sie stattdessen:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>\u201cErf\u00fcllt der vorhandene vorgeschaltete Schutz bereits die Anforderungen f\u00fcr diesen spezifischen SPD?\u201d<\/strong><\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Wichtigste Erkenntnisse<\/h1>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Ein SPD und eine Sicherung oder ein Leitungsschutzschalter erf\u00fcllen unterschiedliche Schutzfunktionen.<\/li>\n\n\n\n<li>An SPD&#8217;s internal thermal disconnector does not automatically replace external short-circuit or overcurrent protection.<\/li>\n\n\n\n<li>Nicht jeder SPD erfordert eine separate Vorsicherung.<\/li>\n\n\n\n<li>The upstream protective device must be compared with the SPD manufacturer&#8217;s declared limits.<\/li>\n\n\n\n<li>Eine gr\u00f6\u00dfere Sicherung ist nicht automatisch besser.<\/li>\n\n\n\n<li>Eine kleinere Sicherung ist nicht automatisch sicherer, da eine ungeeignete Dimensionierung zu unerw\u00fcnschten Abschaltungen f\u00fchren kann.<\/li>\n\n\n\n<li>Die Ampere-Nennwerte von Sicherungen und Leitungsschutzschaltern sollten nicht als direkt austauschbar betrachtet werden.<\/li>\n\n\n\n<li>Die Anforderungen an AC-\u00dcberspannungsschutzger\u00e4te (SPD) und PV-DC-\u00dcberspannungsschutzger\u00e4te m\u00fcssen getrennt bewertet werden.<\/li>\n\n\n\n<li>Der prospektive Kurzschlussstrom am Installationsort ist von Bedeutung.<\/li>\n\n\n\n<li>Leiterquerschnitt und Leitungsl\u00e4nge des SPD m\u00fcssen ebenfalls ber\u00fccksichtigt werden.<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Welche Funktion hat eine Vorsicherung f\u00fcr ein SPD tats\u00e4chlich?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Ein SPD und eine \u00dcberstromschutzeinrichtung l\u00f6sen unterschiedliche elektrische Probleme.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Ein typisches Netz-SPD wird parallel zum Stromkreis geschaltet.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Im Normalbetrieb f\u00fchrt es wenig oder keinen Laststrom. Bei einer transienten \u00dcberspannung wird das SPD leitf\u00e4hig und leitet den Sto\u00dfstrom \u00fcber seinen vorgesehenen Schutzpfad ab.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Eine Sicherung oder ein Leitungsschutzschalter hat einen anderen Zweck.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Seine Aufgabe ist prim\u00e4r die Unterbrechung von anhaltenden \u00dcberstr\u00f6men oder Fehlerstr\u00f6men.<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Ger\u00e4t<\/th><th>Hauptfunktion<\/th><th>Haupts\u00e4chlich ausgelegt f\u00fcr<\/th><\/tr><\/thead><tbody><tr><td>SPD<\/td><td>Begrenzt transiente \u00dcberspannungen und leitet Sto\u00dfstr\u00f6me ab<\/td><td>Blitz- und Schalt\u00fcberspannungen<\/td><\/tr><tr><td>Sicherung<\/td><td>Unterbricht \u00fcberm\u00e4\u00dfige Str\u00f6me<\/td><td>\u00dcberstrom und Kurzschluss<\/td><\/tr><tr><td>Leitungsschutzschalter<\/td><td>Unterbricht \u00fcberm\u00e4\u00dfige Str\u00f6me und erm\u00f6glicht Trennung\/Schaltung<\/td><td>\u00dcberlast und Kurzschluss<\/td><\/tr><tr><td>Interner SPD-Trennschalter<\/td><td>Trennt ein defektes oder \u00fcberhitztes Schutzelement<\/td><td>Ende der Lebensdauer oder anomaler interner Zustand des SPD<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">Daher:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>SPD \u2260 Sicherung<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">und:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Sicherung \u2260 SPD<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Sie bieten einen komplement\u00e4ren Schutz.<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"576\" src=\"https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-fuse-circuit-breaker-comparison-1024x576.jpg\" alt=\"SPD fuse and circuit breaker protection device comparison\" class=\"wp-image-4525\" srcset=\"https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-fuse-circuit-breaker-comparison-1024x576.jpg 1024w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-fuse-circuit-breaker-comparison-300x169.jpg 300w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-fuse-circuit-breaker-comparison-768x432.jpg 768w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-fuse-circuit-breaker-comparison-1536x864.jpg 1536w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-fuse-circuit-breaker-comparison-18x10.jpg 18w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-fuse-circuit-breaker-comparison-600x338.jpg 600w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-fuse-circuit-breaker-comparison.jpg 1672w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption class=\"wp-element-caption\">Ein SPD begrenzt transiente \u00dcberspannungen, w\u00e4hrend Sicherungen und Leitungsschutzschalter prim\u00e4r f\u00fcr den \u00dcberstrom- und Fehlerschutz eingesetzt werden.<\/figcaption><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Warum kann ein SPD einen Vorsicherungsschutz ben\u00f6tigen?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Viele spannungsbegrenzende SPDs verwenden nichtlineare Komponenten wie Metalloxid-Varistoren.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Bei normaler Systemspannung verbleibt das Schutzelement in einem hochohmigen Zustand.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Bei einem Sto\u00dfstrom \u00e4ndert sich sein elektrisches Verhalten schlagartig und es leitet den Sto\u00dfstrom ab.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u00dcberspannungsschutzkomponenten k\u00f6nnen jedoch aufgrund folgender Faktoren das Ende ihrer Lebensdauer erreichen oder besch\u00e4digt werden:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>wiederholte Sto\u00dfstrombelastung,<\/li>\n\n\n\n<li>schwere Sto\u00dfstromereignisse,<\/li>\n\n\n\n<li>tempor\u00e4re \u00dcberspannung,<\/li>\n\n\n\n<li>inkorrekte Systemspannung,<\/li>\n\n\n\n<li>anormale Fehlerzust\u00e4nde,<\/li>\n\n\n\n<li>oder interne Degradation.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Wenn ein Schutzelement einen niederohmigen Fehler aufweist, muss die Installation in der Lage sein, den resultierenden netzfrequenten oder Gleichstrom-Fehlerstrom sicher abzuschalten.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Deshalb k\u00f6nnen Datenbl\u00e4tter von \u00dcberspannungsschutzger\u00e4ten (SPD) Parameter enthalten wie:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>maximale Vorsicherung,<\/li>\n\n\n\n<li>maximaler netzseitiger \u00dcberstromschutz,<\/li>\n\n\n\n<li>Backup-Schutz,<\/li>\n\n\n\n<li>Kurzschlussfestigkeit,<\/li>\n\n\n\n<li>Isccr,<\/li>\n\n\n\n<li>SCCR,<\/li>\n\n\n\n<li>oder empfohlenes Schutzger\u00e4t.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">F\u00fcr AC-Niederspannungs-\u00dcberspannungsschutzger\u00e4te (SPD) ist die aktuelle internationale Produktnorm <strong>IEC 61643-11:2025<\/strong>, welche Anforderungen und Pr\u00fcfverfahren f\u00fcr SPDs zum Anschluss an Wechselstromkreise bis 1.000 V Effektivwert abdeckt.<br><a href=\"https:\/\/webstore.iec.ch\/en\/publication\/65314\" target=\"_blank\" rel=\"noreferrer noopener\">IEC 61643-11:2025 \u2014 offizielle IEC-Seite<\/a><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Interner SPD-Trennschalter vs. externer Vorsicherung<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Eine h\u00e4ufige Frage lautet:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\">\u201cWenn mein SPD bereits \u00fcber einen internen Trennschalter verf\u00fcgt, warum wird dann noch eine weitere Sicherung ben\u00f6tigt?\u201d<\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">Da sie nicht notwendigerweise die gleiche Funktion erf\u00fcllen.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Interner SPD-Trennschalter<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Der interne Trennschalter ist im Allgemeinen mit der \u00dcberspannungsschutzkomponente innerhalb des SPD verbunden.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Wenn beispielsweise ein MOV einen unsicheren thermischen Zustand erreicht, kann der interne Mechanismus das defekte Element trennen.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Bei vielen modularen SPDs ist dieser Zustand mechanisch mit einer Statusanzeige gekoppelt.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The window may change from green to red, depending on the manufacturer&#8217;s design.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Externer Vorsicherungsschutz<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">The external fuse or circuit breaker is part of the installation&#8217;s fault-current protection and coordination.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Je nach SPD kann dies dazu beitragen:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>den Kurzschlussstrom im SPD-Zweig zu unterbrechen,<\/li>\n\n\n\n<li>zugeh\u00f6rige Leiter zu sch\u00fctzen,<\/li>\n\n\n\n<li>eine sichere Trennung zu erm\u00f6glichen,<\/li>\n\n\n\n<li>and keep the installation within the SPD manufacturer&#8217;s tested fault conditions.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Daher:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>Ein interner thermischer Trennschalter sollte nicht automatisch als Ersatz f\u00fcr eine externe SPD-Vorsicherung betrachtet werden.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">Die Produktdokumentation muss dennoch gepr\u00fcft werden.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Ben\u00f6tigt jedes SPD eine separate Vorsicherung?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Nein.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Es gibt drei h\u00e4ufige Situationen.<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Installationsbedingung<\/th><th>Separater Vorsicherungsschutz<\/th><\/tr><\/thead><tbody><tr><td>Existing upstream device is within the SPD manufacturer&#8217;s permitted conditions<\/td><td>Oft nicht erforderlich<\/td><\/tr><tr><td>Existing upstream device exceeds the manufacturer&#8217;s permitted limit<\/td><td>Ein dedizierter Schutz kann erforderlich sein<\/td><\/tr><tr><td>SPD verf\u00fcgt \u00fcber einen gepr\u00fcften integrierten Vorsicherungsschutz<\/td><td>Zus\u00e4tzliches Vorsicherungsger\u00e4t ist unter den spezifizierten Bedingungen m\u00f6glicherweise nicht erforderlich<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">Dies ist einer der wichtigsten Punkte bei <strong>SPD-Vorsicherung<\/strong>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Sie k\u00f6nnen die Entscheidung nicht allein auf Basis folgender Punkte treffen:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Typ 1,<\/li>\n\n\n\n<li>Typ 2,<\/li>\n\n\n\n<li>Typ 1+2,<\/li>\n\n\n\n<li>In,<\/li>\n\n\n\n<li>Imax,<\/li>\n\n\n\n<li>Uc,<\/li>\n\n\n\n<li>Ucpv.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Zwei Typ-2-\u00dcberspannungsschutzger\u00e4te (SPD) mit \u00e4hnlichen Spannungs- und Imax-Werten k\u00f6nnen unterschiedliche Anforderungen an den Vorsicherungsschutz haben.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">F1 und F2: Verst\u00e4ndnis des SPD-Vorsicherungsschutzes<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Installationspl\u00e4ne f\u00fcr SPDs verwenden h\u00e4ufig zwei Bezeichnungen:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>F1 = vorgeschaltete Schutzeinrichtung des Systems<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>F2 = dedizierte SPD-Vorsicherung<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Eine vereinfachte Anordnung kann wie folgt aussehen:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Einspeisung \u2192 F1 \u2192 Verteilungssystem<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">wobei das SPD parallel geschaltet ist \u00fcber <strong>F2<\/strong> wo ein dedizierter F2-Schutz erforderlich ist.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Bei der Auswahl einer <strong>Vorsicherung f\u00fcr \u00dcberspannungsschutzger\u00e4te (SPD)<\/strong>, sollte die erste Frage daher nicht lauten:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\">\u201cWelche Sicherungsgr\u00f6\u00dfe sollte ich kaufen?\u201d<\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">Fragen Sie stattdessen:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\">\u201cKann die vorhandene F1 bereits den f\u00fcr diesen SPD erforderlichen Schutz bieten?\u201d<\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">If F1 meets the manufacturer&#8217;s conditions, F2 may not be necessary.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Wenn F1 gr\u00f6\u00dfer als der zul\u00e4ssige Wert ist, kann eine dedizierte F2 erforderlich sein.<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"576\" src=\"https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-protection-f1-f2-diagram-1024x576.jpg\" alt=\"F1 and F2 SPD backup protection diagram\" class=\"wp-image-4526\" srcset=\"https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-protection-f1-f2-diagram-1024x576.jpg 1024w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-protection-f1-f2-diagram-300x169.jpg 300w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-protection-f1-f2-diagram-768x432.jpg 768w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-protection-f1-f2-diagram-1536x864.jpg 1536w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-protection-f1-f2-diagram-18x10.jpg 18w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-protection-f1-f2-diagram-600x338.jpg 600w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-protection-f1-f2-diagram.jpg 1672w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption class=\"wp-element-caption\">F1 ist die vorgeschaltete Schutzeinrichtung des Systems, w\u00e4hrend F2 bei Bedarf eine dedizierte SPD-Absicherung darstellt.<\/figcaption><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">This principle is demonstrated clearly in several manufacturer&#8217;s published installation guides, which we will examine later.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">7 Regeln f\u00fcr die korrekte Auswahl der SPD-Vorsicherung<\/h1>\n\n\n\n<h2 class=\"wp-block-heading\">Regel 1: Beginnen Sie mit dem exakten Datenblatt des SPD<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Es gibt keine universelle <strong>Vorsicherung f\u00fcr \u00dcberspannungsschutzger\u00e4te (SPD)<\/strong> Gr\u00f6\u00dfe.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Always start with the exact manufacturer&#8217;s datasheet or installation instructions.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Achten Sie auf Formulierungen wie:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Maximale Vorsicherung<\/li>\n\n\n\n<li>Max. netzseitiger \u00dcberstromschutz<\/li>\n\n\n\n<li>Vorsicherung<\/li>\n\n\n\n<li>Back-up-Schutz<\/li>\n\n\n\n<li>Empfohlene Schutzeinrichtung<\/li>\n\n\n\n<li>Maximale vorgeschaltete Sicherung<\/li>\n\n\n\n<li>Kurzschlussfestigkeit<\/li>\n\n\n\n<li>Isccr<\/li>\n\n\n\n<li>SCCR<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">\u00dcbernehmen Sie keinen Sicherungswert von einem anderen SPD, nur weil beide Ger\u00e4te vom Typ 2 sind oder beide einen Imax-Wert von 40 kA aufweisen.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Produktaufbau und gepr\u00fcfte Koordination k\u00f6nnen unterschiedlich sein.<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"576\" src=\"https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/check-spd-datasheet-before-backup-fuse-selection-1024x576.jpg\" alt=\"Checking SPD datasheet before selecting backup fuse\" class=\"wp-image-4528\" srcset=\"https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/check-spd-datasheet-before-backup-fuse-selection-1024x576.jpg 1024w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/check-spd-datasheet-before-backup-fuse-selection-300x169.jpg 300w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/check-spd-datasheet-before-backup-fuse-selection-768x432.jpg 768w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/check-spd-datasheet-before-backup-fuse-selection-1536x864.jpg 1536w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/check-spd-datasheet-before-backup-fuse-selection-18x10.jpg 18w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/check-spd-datasheet-before-backup-fuse-selection-600x338.jpg 600w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/check-spd-datasheet-before-backup-fuse-selection.jpg 1672w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption class=\"wp-element-caption\">Der Vorsicherungsschutz sollte anhand des spezifischen Datenblatts des SPD ausgew\u00e4hlt werden und nicht anhand eines universellen Sicherungswertes.<\/figcaption><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Regel 2: Zuerst den vorhandenen vorgeschalteten Schutz pr\u00fcfen<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Angenommen, ein SPD-Hersteller erlaubt:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Maximaler Vorsicherungsschutz = 125 A gG<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">und das System verf\u00fcgt bereits \u00fcber:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>F1 = 63 A gG<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Wenn alle anderen Anforderungen des Herstellers erf\u00fcllt sind, bietet die vorhandene Vorsicherung m\u00f6glicherweise bereits den erforderlichen Schutz.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Die Installation einer weiteren 125-A-Sicherung macht die Anlage nicht automatisch sicherer.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Betrachten Sie nun:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>F1 = 250 A gG<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Wenn der SPD nur f\u00fcr eine maximale Vorsicherung von 125 A gG zugelassen ist, erf\u00fcllt der vorhandene 250-A-Schutz m\u00f6glicherweise nicht mehr die Anforderungen des SPD.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Eine dedizierte <strong>Vorsicherung f\u00fcr \u00dcberspannungsschutzger\u00e4te (SPD)<\/strong> Absicherung kann dann erforderlich sein.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Deshalb muss F1 \u00fcberpr\u00fcft werden, bevor F2 hinzugef\u00fcgt wird.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Regel 3: \u00dcberpr\u00fcfung des prospektiven Kurzschlussstroms<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Die Amperezahl der Sicherung allein reicht nicht aus.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Sie m\u00fcssen auch den verf\u00fcgbaren Fehlerstrom am Installationsort ber\u00fccksichtigen.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Derselbe SPD kann je nach Installationsort mit sehr unterschiedlichen Fehlerbedingungen konfrontiert sein.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Zum Beispiel:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Ein kleiner nachgeschalteter Verteiler kann einen relativ niedrigen prospektiven Kurzschlussstrom aufweisen.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Ein industrieller Hauptverteiler in der N\u00e4he eines Transformators kann einen deutlich h\u00f6heren verf\u00fcgbaren Fehlerstrom aufweisen.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Bewerten Sie daher immer die Kombination aus:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>SPD + Vorsicherung + verf\u00fcgbarer Kurzschlussstrom<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Dies ist besonders wichtig bei:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Industriever teiler,<\/li>\n\n\n\n<li>gro\u00dfe Gewerbegeb\u00e4ude,<\/li>\n\n\n\n<li>sekund\u00e4rseitige Transformatoren-Verteiler,<\/li>\n\n\n\n<li>gro\u00dfe PV-Anlagen,<\/li>\n\n\n\n<li>Energiespeichersysteme,<\/li>\n\n\n\n<li>und elektrische Hochstromsysteme.<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Regel 4: Dimensionieren Sie eine Vorsicherung f\u00fcr einen \u00dcberspannungsschutz (SPD) niemals auf  Basis von Imax<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Betrachten Sie einen Typ-2-\u00dcberspannungsschutz mit folgender Kennzeichnung:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>In = 20 kA<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Imax = 40 kA<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Ein sehr h\u00e4ufiger Fehler ist:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\">\u201cDer SPD hat 40 kA, daher sollte er mit einer 40-A-Sicherung abgesichert werden.\u201d<\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">Das ist nicht korrekt.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Imax = 40 kA<\/strong> beschreibt eine Sto\u00dfstromcharakteristik in Verbindung mit der relevanten Impulsstromform.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A <strong>40-A-Sicherung<\/strong> ist ein Bemessungswert f\u00fcr eine \u00dcberstromschutzeinrichtung.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Diese Werte beschreiben unterschiedliche elektrische Ph\u00e4nomene.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Daher:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>The SPD backup fuse rating cannot be calculated directly from the SPD&#8217;s Imax value.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"683\" src=\"https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-imax-vs-backup-fuse-rating-1024x683.jpg\" alt=\"40 kA SPD Imax is not equal to a 40 A backup fuse\" class=\"wp-image-4527\" srcset=\"https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-imax-vs-backup-fuse-rating-1024x683.jpg 1024w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-imax-vs-backup-fuse-rating-300x200.jpg 300w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-imax-vs-backup-fuse-rating-768x512.jpg 768w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-imax-vs-backup-fuse-rating-18x12.jpg 18w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-imax-vs-backup-fuse-rating-600x400.jpg 600w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-imax-vs-backup-fuse-rating.jpg 1536w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption class=\"wp-element-caption\">SPD-Sto\u00dfstromnennwerte wie Imax k\u00f6nnen nicht direkt in einen Ampere-Wert f\u00fcr eine Vorsicherung umgerechnet werden.<\/figcaption><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">Wenn Sie sich \u00fcber den Unterschied zwischen In, Imax, Up und Iscpv unsicher sind, lesen Sie unsere <a href=\"https:\/\/cnkuangya.com\/de\/blog\/dc-spd-specifications\/\" target=\"_blank\" rel=\"noreferrer noopener\">Leitfaden f\u00fcr DC-SPD-Spezifikationen<\/a>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Das Verst\u00e4ndnis dieser Parameter verhindert einen der h\u00e4ufigsten Fehler bei der Auswahl von \u00dcberspannungsschutzger\u00e4ten (SPD).<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Regel 5: \u00dcberpr\u00fcfen Sie den Leiterquerschnitt<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">The manufacturer&#8217;s maximum backup-fuse value does not mean that the largest permitted fuse should always be installed.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Die Schutzeinrichtung muss zudem auf Folgendes abgestimmt sein:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Kabelquerschnitt,<\/li>\n\n\n\n<li>Leiterisolierung,<\/li>\n\n\n\n<li>Anschlusskapazit\u00e4t,<\/li>\n\n\n\n<li>Verdrahtungsart,<\/li>\n\n\n\n<li>Installationstemperatur,<\/li>\n\n\n\n<li>enclosure conditions,<\/li>\n\n\n\n<li>and local electrical requirements.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">For example, if an SPD permits a maximum backup fuse of 125 A, that does not automatically mean every installation should use a 125 A fuse.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Maximum<\/strong> is a limit, not always a recommendation.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Rule 6: Do Not Assume a Fuse and Circuit Breaker Are Equivalent<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">A fuse and a circuit breaker can both provide overcurrent protection, but their operating characteristics are different.<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Faktor<\/th><th>Sicherung<\/th><th>Stromkreisunterbrecher<\/th><\/tr><\/thead><tbody><tr><td>Replacement after operation<\/td><td>Must normally be replaced<\/td><td>Can normally be reset after investigation<\/td><\/tr><tr><td>Time-current behavior<\/td><td>Depends on fuse class and rating<\/td><td>Depends on breaker type and trip curve<\/td><\/tr><tr><td>Short-circuit capability<\/td><td>Can be very high<\/td><td>Depends on breaker breaking capacity<\/td><\/tr><tr><td>Surge impulse behavior<\/td><td>Depends on fuse characteristics<\/td><td>Depends on breaker characteristics<\/td><\/tr><tr><td>Trennung<\/td><td>Requires suitable holder\/switching arrangement<\/td><td>Often convenient<\/td><\/tr><tr><td>Koordinierung<\/td><td>Must match SPD data<\/td><td>Must match SPD data<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">Daher:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>Do not assume that a 125 A gG fuse can automatically be replaced by a 125 A circuit breaker.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">Manufacturers can specify different protective-device combinations.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For example, Schneider Electric publishes coordination tables pairing particular SPD models with specific protective-device ratings rather than applying one universal breaker value.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Rule 7: Separate AC and PV DC Requirements<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Do not copy an AC SPD backup-protection rule directly into a photovoltaic DC system.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">PV systems have different:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>voltage characteristics,<\/li>\n\n\n\n<li>fault-current behavior,<\/li>\n\n\n\n<li>source characteristics,<\/li>\n\n\n\n<li>protection devices,<\/li>\n\n\n\n<li>and disconnection requirements.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">SPDs designed specifically for the DC side of photovoltaic installations are covered by <strong>IEC 61643-31:2018<\/strong>, which applies to PV DC SPDs up to 1,500 V DC.<br><a href=\"https:\/\/webstore.iec.ch\/en\/publication\/26931\" target=\"_blank\" rel=\"noreferrer noopener\">IEC 61643-31:2018 \u2014 official IEC page<\/a><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This is why an AC SPD backup-fuse example should never automatically be applied to a 1,000 V or 1,500 V PV system.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Real Manufacturer SPD Backup Fuse Examples<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">The following <strong>SPD backup fuse examples<\/strong> come from published manufacturer technical information.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">They are useful because they demonstrate that backup-protection requirements vary significantly between products.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Do not copy these values to another SPD without checking its own datasheet.<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Manufacturer Example<\/th><th>Published Information<\/th><th>What It Demonstrates<\/th><\/tr><\/thead><tbody><tr><td>Schneider Electric Resi MAX<\/td><td>Backup fuse only required if not already provided in mains; published table shows no F2 required in one F1 \u2264125 A \/ Isc &lt;50 kA arrangement<\/td><td>Existing upstream protection may sometimes provide the required backup protection<\/td><\/tr><tr><td>Phoenix Contact VAL-SEC<\/td><td>Published guidance allows installation without additional F2 up to specified upstream conditions; if dedicated F2 is used, 125 A gG is recommended in the example<\/td><td>F2 is not automatically required<\/td><\/tr><tr><td>DEHNguard SE CI<\/td><td>Integrated backup fuse; manufacturer states no additional backup fuse required up to its specified 25 kArms short-circuit condition<\/td><td>Backup protection can be integrated into the SPD<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">Let&#8217;s look at these examples more closely.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Example 1: Schneider Electric \u2014 Existing F1 Can Sometimes Replace F2<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Schneider Electric&#8217;s Resi MAX installation instructions provide an especially useful example.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For the documented SPD arrangement, Schneider states that the backup fuse is:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\">required only if suitable protection is not already provided in the mains.<\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">The document lists <strong>\u2264125 A gL\/gG<\/strong> backup protection and shows a case where:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>F1 \u2264125 A<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">und:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Isc &lt;50 kA<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">can result in:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>No need for F2<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">under the manufacturer&#8217;s stated conditions.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><a href=\"https:\/\/download.schneider-electric.com\/files?filename=Instruction+sheet&amp;p_Doc_Ref=CLPDOC_W0001675\" target=\"_blank\" rel=\"noreferrer noopener\">Schneider Electric Resi MAX SPD installation instructions<\/a><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This is an excellent example of why installing an additional fuse automatically is not always correct.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Example 2: Phoenix Contact \u2014 Too Small Is Not Automatically Better<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Phoenix Contact provides a useful Type 2 SPD backup-fuse example for its VAL-SEC range.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Its published technical guidance explains that the device can be installed in the branch line without an additional F2 under specified upstream protection conditions.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Where a dedicated F2 is nevertheless required or desired, the document gives:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>125 A gG<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">as an appropriate value for the example.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">More importantly, Phoenix Contact also warns against selecting certain smaller backup fuses below <strong>80 A gG<\/strong> in that specific arrangement because their impulse withstand may result in unwanted operation during surge events.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><a href=\"https:\/\/assets.phoenixcontact.com\/file\/e01e5152-d450-43c3-aaa4-1a68dcc61f14\/media\/original?EN_Info_Vorsicherung_LoRes.pdf\" target=\"_blank\" rel=\"noreferrer noopener\">Phoenix Contact \u2014 The Right Backup Fuse for Surge Protective Devices<\/a><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Dies bedeutet <strong>nicht<\/strong> mean that every Type 2 SPD needs an 80 A or 125 A fuse.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">It demonstrates something more important:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>An SPD backup fuse must be coordinated with the specific SPD. Choosing the smallest possible fuse is not automatically the safest option.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Example 3: DEHN \u2014 Integrated Backup Protection<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Not every SPD requires an external backup fuse.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">DEHN&#8217;s <strong>DEHNguard SE CI<\/strong> Type 2 SPD includes an integrated backup fuse.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">DEHN states that no additional backup fuse is required for installations within the product&#8217;s specified maximum short-circuit current of <strong>25 kArms<\/strong>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><a href=\"https:\/\/www.dehn-international.com\/store\/p\/en-DE\/F1869543\/dehnguard-se-ci-with-integrated-backup-fuse?locale=en\" target=\"_blank\" rel=\"noreferrer noopener\">DEHNguard SE CI with integrated backup fuse<\/a><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This example shows why the statement:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\">\u201cEvery SPD must have a separate external fuse.\u201d<\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">is incorrect.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The correct arrangement depends on the tested product design.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Can an SPD Backup Fuse Be Too Small?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Ja.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A smaller fuse is not automatically safer.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The protective device must be capable of remaining intact during the surge conditions that the SPD is intended to handle while still interrupting a sustained fault when required.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If an undersized fuse operates unnecessarily during a surge, the SPD can become disconnected.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The electrical installation may then continue operating normally while surge protection has been lost.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This can be particularly difficult to notice in a parallel-connected SPD.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Phoenix Contact&#8217;s published example illustrates this issue by warning against certain undersized gG backup fuses in the specific Type 2 SPD arrangement described above.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Again:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>This is a product-specific example, not a universal minimum fuse value.<\/strong><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Can an SPD Backup Fuse Be Too Large?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Ja.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If the external protective device exceeds the maximum value permitted by the SPD manufacturer, the SPD may no longer be operating within the tested fault-protection arrangement.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For example, if a product states:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\">Maximum backup fuse: 125 A gG<\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">this should not be interpreted as:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\">\u201c125 A must always be installed.\u201d<\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">Instead it means that the protection arrangement should not exceed the manufacturer&#8217;s stated limit unless another approved configuration is provided.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The actual selection must still consider:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>upstream protection,<\/li>\n\n\n\n<li>conductor size,<\/li>\n\n\n\n<li>short-circuit current,<\/li>\n\n\n\n<li>SPD instructions,<\/li>\n\n\n\n<li>and installation design.<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Example: Small Commercial Distribution Board<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Consider a Type 2 SPD in a small commercial distribution board.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Assume:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Main upstream fuse F1 = 63 A gG<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">and the selected SPD permits:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Maximaler Vorsicherungsschutz = 125 A gG<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>the available short-circuit current is within the SPD&#8217;s declared capability,<\/li>\n\n\n\n<li>the wiring is suitable,<\/li>\n\n\n\n<li>and the manufacturer permits the arrangement,<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">then the existing 63 A upstream device may already provide the required backup protection.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Adding a second 125 A fuse would not automatically improve the system.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Example: Industrial Main Distribution Board<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Now consider a larger industrial panel.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Assume:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>F1 = 400 A<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">while the SPD permits:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Maximum backup protection = 125 A gG<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The upstream protection now exceeds the manufacturer&#8217;s stated limit.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A dedicated F2 may therefore be required.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The simplified arrangement may become:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>400 A upstream protection \u2192 SPD branch \u2192 approved F2 \u2192 SPD<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">However, the designer must still verify:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>prospective short-circuit current,<\/li>\n\n\n\n<li>breaking capacity,<\/li>\n\n\n\n<li>conductor cross-section,<\/li>\n\n\n\n<li>SPD short-circuit rating,<\/li>\n\n\n\n<li>fuse class,<\/li>\n\n\n\n<li>and manufacturer instructions.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">This is why a backup-protection arrangement that works in a small distribution board cannot simply be copied into an industrial main panel.<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"576\" src=\"https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-protection-small-vs-industrial-panel-1024x576.jpg\" alt=\"SPD backup protection in small and industrial electrical panels\" class=\"wp-image-4529\" srcset=\"https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-protection-small-vs-industrial-panel-1024x576.jpg 1024w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-protection-small-vs-industrial-panel-300x169.jpg 300w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-protection-small-vs-industrial-panel-768x432.jpg 768w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-protection-small-vs-industrial-panel-1536x864.jpg 1536w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-protection-small-vs-industrial-panel-18x10.jpg 18w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-protection-small-vs-industrial-panel-600x338.jpg 600w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-protection-small-vs-industrial-panel.jpg 1672w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption class=\"wp-element-caption\">SPD backup protection must be coordinated with the actual upstream protection and short-circuit conditions of the installation.<\/figcaption><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">How Does SPD Backup Protection Work in a PV DC System?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Photovoltaic DC systems require additional care.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A PV DC SPD must be suitable for:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>the maximum PV system voltage,<\/li>\n\n\n\n<li>Ucpv,<\/li>\n\n\n\n<li>PV fault-current conditions,<\/li>\n\n\n\n<li>the relevant system topology,<\/li>\n\n\n\n<li>and the manufacturer&#8217;s specified disconnection arrangement.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">The exact <strong>Vorsicherung f\u00fcr \u00dcberspannungsschutzger\u00e4te (SPD)<\/strong> arrangement can depend on:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>maximum PV short-circuit current,<\/li>\n\n\n\n<li>number of parallel strings,<\/li>\n\n\n\n<li>existing string protection,<\/li>\n\n\n\n<li>array protection,<\/li>\n\n\n\n<li>SPD Iscpv,<\/li>\n\n\n\n<li>gPV fuse characteristics,<\/li>\n\n\n\n<li>and system voltage.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Before choosing backup protection, the SPD voltage itself must also be correct.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For more detail, see our <a href=\"https:\/\/cnkuangya.com\/de\/blog\/dc-spd-selection-guide\/\" target=\"_blank\" rel=\"noreferrer noopener\">DC SPD voltage selection guide for solar PV systems<\/a>.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Should a PV SPD Always Use a gPV Fuse?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Nein.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A gPV fuse is specifically designed for photovoltaic applications, but this does <strong>nicht<\/strong> mean every PV SPD requires a separate gPV backup fuse.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The manufacturer&#8217;s instructions must be checked first.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Depending on the system design, existing PV overcurrent protection may already form part of the approved protection arrangement.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If a gPV fuse is required, it must also be suitable for:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>DC voltage,<\/li>\n\n\n\n<li>current,<\/li>\n\n\n\n<li>breaking capacity,<\/li>\n\n\n\n<li>PV application,<\/li>\n\n\n\n<li>conductor size,<\/li>\n\n\n\n<li>and environmental conditions.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">For examples of PV-rated fuse links and holders, see KUANGYA&#8217;s <a href=\"https:\/\/cnkuangya.com\/de\/dc-fuse\/\" target=\"_blank\" rel=\"noreferrer noopener\">DC gPV fuse range<\/a>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The product page is useful for understanding available PV fuse formats, but final SPD coordination must still follow the SPD manufacturer&#8217;s technical data.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Where Should the SPD Backup Fuse Be Installed?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Where dedicated backup protection is required, it is normally positioned in the SPD branch so that fault current flowing to the SPD can be interrupted.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A simplified concept is:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Busbar \/ Supply \u2192 F2 \u2192 SPD \u2192 required protection path<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">However, the exact wiring depends on:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>TN-S,<\/li>\n\n\n\n<li>TN-C,<\/li>\n\n\n\n<li>TN-C-S,<\/li>\n\n\n\n<li>TT,<\/li>\n\n\n\n<li>IT,<\/li>\n\n\n\n<li>single-phase,<\/li>\n\n\n\n<li>three-phase,<\/li>\n\n\n\n<li>PV DC configuration,<\/li>\n\n\n\n<li>SPD protection modes.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Always follow the wiring diagram for the exact SPD.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Do Not Forget SPD Lead Length<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Adding a fuse or breaker should not result in unnecessarily long SPD connections.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">SPD connection conductors have inductance.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">During a fast-rising surge current, additional lead length can increase the voltage appearing across the protected equipment.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This means backup protection should be coordinated while keeping the SPD connection path short and direct.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For PV systems, there is also another distance issue: the distance between the SPD location and the inverter.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">These two distances should not be confused.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For a detailed explanation, see our guide to <a href=\"https:\/\/cnkuangya.com\/de\/blog\/spd-distance-from-inverter\/\" target=\"_blank\" rel=\"noreferrer noopener\">SPD distance from inverter and SPD connection lead length<\/a>.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Can One Breaker Protect Both the Load and the SPD?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Sometimes.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The existing protective device may be acceptable if:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>the SPD manufacturer allows it,<\/li>\n\n\n\n<li>its rating is within the required limit,<\/li>\n\n\n\n<li>the short-circuit conditions are acceptable,<\/li>\n\n\n\n<li>conductor protection is maintained,<\/li>\n\n\n\n<li>and the installation arrangement satisfies applicable requirements.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">However, a dedicated SPD breaker can also provide practical advantages such as easier isolation and maintenance.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Der wichtige Punkt ist:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>Dedicated protection does not automatically mean correctly coordinated protection.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">The device must still match the SPD manufacturer&#8217;s requirements.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">What Happens If the SPD Backup Fuse Opens?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Because many power SPDs are connected in parallel, the main electrical load can continue operating even after the SPD branch is disconnected.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">That means:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Power ON does not necessarily mean surge protection ON.<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If the backup fuse opens, the cause should be investigated rather than simply replacing the fuse and re-energizing the system.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">M\u00f6gliche Ursachen sind:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>an SPD internal fault,<\/li>\n\n\n\n<li>severe surge stress,<\/li>\n\n\n\n<li>tempor\u00e4re \u00dcberspannung,<\/li>\n\n\n\n<li>incorrect SPD selection,<\/li>\n\n\n\n<li>inappropriate backup protection,<\/li>\n\n\n\n<li>wiring faults,<\/li>\n\n\n\n<li>or abnormal system conditions.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">If you suspect the SPD itself has failed, see our guide on <a href=\"https:\/\/cnkuangya.com\/de\/blog\/how-to-know-if-an-spd-is-bad\/\" target=\"_blank\" rel=\"noreferrer noopener\">wie man erkennt, ob ein SPD defekt ist<\/a>.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Common SPD Backup Protection Mistakes<\/h1>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Irrtum<\/th><th>Why It Is Wrong<\/th><\/tr><\/thead><tbody><tr><td>40 kA SPD = 40 A fuse<\/td><td>Imax and fuse current rating describe completely different electrical quantities<\/td><\/tr><tr><td>Every Type 2 SPD needs 125 A<\/td><td>Backup protection is manufacturer-specific<\/td><\/tr><tr><td>Smaller fuse is always safer<\/td><td>It may disconnect unnecessarily during surge events<\/td><\/tr><tr><td>Internal SPD disconnector means no external protection is ever required<\/td><td>Internal and external protective functions are not necessarily identical<\/td><\/tr><tr><td>125 A fuse = 125 A breaker<\/td><td>Fuse and breaker operating characteristics differ<\/td><\/tr><tr><td>F2 must always be installed<\/td><td>Existing F1 may already meet the SPD requirement<\/td><\/tr><tr><td>Ignore prospective short-circuit current<\/td><td>SPD protection must be coordinated with available fault current<\/td><\/tr><tr><td>Use AC examples for PV DC SPD<\/td><td>AC and PV DC systems have different requirements<\/td><\/tr><tr><td>Choose only by Imax<\/td><td>Imax does not determine backup-fuse rating<\/td><\/tr><tr><td>Use maximum permitted fuse automatically<\/td><td>\u201cMaximum\u201d is a limit, not necessarily the ideal rating<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">SPD Backup Fuse Selection Checklist<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Before selecting an <strong>SPD-Vorsicherung oder der Leitungsschutzschalter<\/strong>, check the following:<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Siehe<\/th><th>Frage<\/th><\/tr><\/thead><tbody><tr><td>Exact SPD<\/td><td>What manufacturer and model is installed?<\/td><\/tr><tr><td>Anmeldung<\/td><td>AC or photovoltaic DC?<\/td><\/tr><tr><td>SPD-Typ<\/td><td>Type 1, Type 1+2 or Type 2?<\/td><\/tr><tr><td>Spannung<\/td><td>Are Uc\/Ucpv suitable for the system?<\/td><\/tr><tr><td>Upstream device<\/td><td>What is F1?<\/td><\/tr><tr><td>Manufacturer limit<\/td><td>What maximum backup protection is specified?<\/td><\/tr><tr><td>Dedicated F2<\/td><td>Is it actually required?<\/td><\/tr><tr><td>Fault current<\/td><td>What is the prospective short-circuit current?<\/td><\/tr><tr><td>Fuse class<\/td><td>gG, gPV or another specified type?<\/td><\/tr><tr><td>Leitungsschutzschalter<\/td><td>What curve and breaking capacity are required?<\/td><\/tr><tr><td>Conductors<\/td><td>Is the conductor cross-section suitable?<\/td><\/tr><tr><td>Terminals<\/td><td>Can the SPD terminals accept the selected conductors?<\/td><\/tr><tr><td>Lead length<\/td><td>Are SPD connection leads short and direct?<\/td><\/tr><tr><td>Earthing<\/td><td>Is the protection path correctly connected?<\/td><\/tr><tr><td>Indication<\/td><td>Can failure or disconnection be detected?<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">If several of these answers are unknown, selecting a backup fuse by guesswork is not appropriate.<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"576\" src=\"https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-fuse-selection-checklist-1024x576.jpg\" alt=\"SPD backup fuse selection checklist for electrical installation\" class=\"wp-image-4531\" srcset=\"https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-fuse-selection-checklist-1024x576.jpg 1024w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-fuse-selection-checklist-300x169.jpg 300w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-fuse-selection-checklist-768x432.jpg 768w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-fuse-selection-checklist-1536x864.jpg 1536w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-fuse-selection-checklist-18x10.jpg 18w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-fuse-selection-checklist-600x338.jpg 600w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-fuse-selection-checklist.jpg 1672w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption class=\"wp-element-caption\">Check the SPD model, upstream protection, short-circuit conditions, conductors and manufacturer requirements before selecting backup protection.<\/figcaption><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Relevant Standards to Check<\/h1>\n\n\n\n<h2 class=\"wp-block-heading\">IEC 61643-11:2025<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">IEC 61643-11 covers SPDs intended for connection to AC low-voltage power circuits and specifies performance and safety requirements, tests and ratings.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><a href=\"https:\/\/webstore.iec.ch\/en\/publication\/65314\" target=\"_blank\" rel=\"noreferrer noopener\">IEC 61643-11:2025<\/a><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">IEC 61643-31:2018<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">IEC 61643-31 applies specifically to SPDs intended for the DC side of photovoltaic installations up to <strong>1.500 V DC<\/strong>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><a href=\"https:\/\/webstore.iec.ch\/en\/publication\/26931\" target=\"_blank\" rel=\"noreferrer noopener\">IEC 61643-31:2018<\/a><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">IEC 60364-5-53<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">IEC 60364-5-53 covers the selection and erection of electrical equipment for protection, isolation, switching, control and monitoring.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The current IEC consolidated version includes the 2019 base publication plus amendments from 2020 and 2024.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><a href=\"https:\/\/webstore.iec.ch\/en\/publication\/104394\" target=\"_blank\" rel=\"noreferrer noopener\">IEC 60364-5-53:2019+A1:2020+A2:2024<\/a><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Applicable national standards, installation rules and manufacturer instructions must also be followed.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">H\u00e4ufig gestellte Fragen<\/h1>\n\n\n\n<h2 class=\"wp-block-heading\">Does Every SPD Need a Backup Fuse?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Nein.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A separate <strong>Vorsicherung f\u00fcr \u00dcberspannungsschutzger\u00e4te (SPD)<\/strong> is not always necessary.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If the existing upstream protective device already satisfies the manufacturer&#8217;s permitted backup-protection conditions, another fuse may not be required.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Some SPDs also include integrated backup protection.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">What Size Fuse Should I Use for an SPD?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">There is no universal fuse size for an SPD.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Use the exact SPD datasheet and check:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>maximum backup protection,<\/li>\n\n\n\n<li>existing F1,<\/li>\n\n\n\n<li>prospective short-circuit current,<\/li>\n\n\n\n<li>conductor size,<\/li>\n\n\n\n<li>and manufacturer instructions.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Do not calculate the fuse size from Imax alone.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">Does a Type 2 SPD Always Need a 125 A Fuse?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Nein.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">125 A appears in several manufacturer examples, but it is not a universal Type 2 SPD value.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Published examples show SPDs with different arrangements, including:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>existing upstream protection,<\/li>\n\n\n\n<li>dedicated backup fuse,<\/li>\n\n\n\n<li>integrated backup fuse,<\/li>\n\n\n\n<li>or other specified protection.<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">Can I Use a Circuit Breaker Instead of a Fuse?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Sometimes.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">But the circuit breaker&#8217;s:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>current rating,<\/li>\n\n\n\n<li>trip characteristic,<\/li>\n\n\n\n<li>breaking capacity,<\/li>\n\n\n\n<li>surge behavior,<\/li>\n\n\n\n<li>and manufacturer-approved coordination<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">must be suitable.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Do not replace a specified fuse with a breaker simply because both devices have the same ampere rating.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">Does an SPD&#8217;s Red Indicator Mean Its Backup Fuse Has Blown?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Nicht unbedingt.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A red status indicator commonly relates to the condition of the SPD&#8217;s internal protection module or disconnection mechanism.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">An external backup fuse is a separate protective device.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Therefore, both the SPD status and the upstream or branch protection should be inspected.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">Can the Electrical System Keep Working After the SPD Fuse Opens?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Ja.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Because many power SPDs are connected in parallel, the protected load may remain energized even if the SPD has been disconnected.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This means surge protection can be lost while the equipment appears to operate normally.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">Does a PV DC SPD Always Need a gPV Backup Fuse?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Nein.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The requirement depends on:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>the exact SPD,<\/li>\n\n\n\n<li>its Iscpv or short-circuit data,<\/li>\n\n\n\n<li>manufacturer instructions,<\/li>\n\n\n\n<li>PV array design,<\/li>\n\n\n\n<li>available fault current,<\/li>\n\n\n\n<li>and existing overcurrent protection.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Never assume every PV SPD needs the same gPV fuse.<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"576\" src=\"https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/pv-dc-spd-gpv-backup-fuse-protection-1024x576.jpg\" alt=\"PV DC SPD and gPV fuse backup protection\" class=\"wp-image-4530\" srcset=\"https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/pv-dc-spd-gpv-backup-fuse-protection-1024x576.jpg 1024w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/pv-dc-spd-gpv-backup-fuse-protection-300x169.jpg 300w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/pv-dc-spd-gpv-backup-fuse-protection-768x432.jpg 768w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/pv-dc-spd-gpv-backup-fuse-protection-1536x864.jpg 1536w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/pv-dc-spd-gpv-backup-fuse-protection-18x10.jpg 18w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/pv-dc-spd-gpv-backup-fuse-protection-600x338.jpg 600w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/pv-dc-spd-gpv-backup-fuse-protection.jpg 1672w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption class=\"wp-element-caption\">PV DC SPD backup protection depends on the SPD data, PV system design, fault current and existing overcurrent protection.<\/figcaption><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">Is SPD Backup Fuse Rating Related to Imax?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Not directly.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Imax represents a surge-discharge current characteristic.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Fuse current rating relates to overcurrent protection.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A 40 kA Imax rating does not mean a 40 A backup fuse is required.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Schlussfolgerung<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">So, does an SPD need a backup fuse or circuit breaker?<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Sometimes yes\u2014but not always as a separate device.<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Richtig <strong>SPD backup fuse selection<\/strong> starts with the manufacturer&#8217;s technical data rather than a universal ampere rating.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The correct decision depends on the relationship between:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>SPD \u2192 F1 \u2192 F2 \u2192 available fault current \u2192 conductors \u2192 electrical system<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Before installing additional backup protection, first check whether the existing upstream device already satisfies the SPD manufacturer&#8217;s requirements.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If dedicated protection is required, verify:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>fuse class or breaker characteristic,<\/li>\n\n\n\n<li>maximum permitted rating,<\/li>\n\n\n\n<li>short-circuit capability,<\/li>\n\n\n\n<li>conductor size,<\/li>\n\n\n\n<li>system voltage,<\/li>\n\n\n\n<li>and installation arrangement.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Most importantly:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>Never select an SPD backup fuse only from Type 1 \/ Type 2, In or Imax. Use the exact manufacturer&#8217;s backup-protection requirements and the actual system conditions.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">For photovoltaic applications, you can also review KUANGYA&#8217;s <a href=\"https:\/\/cnkuangya.com\/de\/dc-spd\/\" target=\"_blank\" rel=\"noreferrer noopener\">DC surge protective devices for solar PV systems<\/a> when comparing Type 2 and Type 1+2 DC SPD options.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>","protected":false},"excerpt":{"rendered":"<p>A surge protective device protects electrical equipment from transient overvoltage, but what protects the SPD if an internal fault or short circuit occurs? This is where the SPD backup fuse or circuit breaker becomes important. However, there is no universal rule such as: \u201cEvery Type 2 SPD needs a 125 A fuse.\u201d or: \u201cA 40 [&hellip;]<\/p>\n","protected":false},"author":7,"featured_media":4524,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[35],"tags":[],"class_list":["post-4523","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-blog"],"blocksy_meta":[],"_links":{"self":[{"href":"https:\/\/cnkuangya.com\/de\/wp-json\/wp\/v2\/posts\/4523","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/cnkuangya.com\/de\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/cnkuangya.com\/de\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/cnkuangya.com\/de\/wp-json\/wp\/v2\/users\/7"}],"replies":[{"embeddable":true,"href":"https:\/\/cnkuangya.com\/de\/wp-json\/wp\/v2\/comments?post=4523"}],"version-history":[{"count":1,"href":"https:\/\/cnkuangya.com\/de\/wp-json\/wp\/v2\/posts\/4523\/revisions"}],"predecessor-version":[{"id":4532,"href":"https:\/\/cnkuangya.com\/de\/wp-json\/wp\/v2\/posts\/4523\/revisions\/4532"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/cnkuangya.com\/de\/wp-json\/wp\/v2\/media\/4524"}],"wp:attachment":[{"href":"https:\/\/cnkuangya.com\/de\/wp-json\/wp\/v2\/media?parent=4523"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/cnkuangya.com\/de\/wp-json\/wp\/v2\/categories?post=4523"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/cnkuangya.com\/de\/wp-json\/wp\/v2\/tags?post=4523"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}