{"id":7342,"date":"2026-01-21T12:19:09","date_gmt":"2026-01-21T11:19:09","guid":{"rendered":"https:\/\/q3-energie.de\/pv-firefighter-safety-switch-for-photovoltaic-systems\/"},"modified":"2026-07-03T14:52:33","modified_gmt":"2026-07-03T12:52:33","slug":"pv-firefighter-safety-switch","status":"publish","type":"page","link":"https:\/\/q3-energie.de\/en\/technic\/pv-firefighter-safety-switch\/","title":{"rendered":"PV Firefighter Safety Switch for Photovoltaic Systems"},"content":{"rendered":"\n
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PV Firefighter Switch: PV Generator Disconnection for Photovoltaic Systems<\/h1>\n\n\n\n
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Technical explanation of safe PV generator disconnection \u2013 from DC string disconnection to optional AC-side shutdown logic.<\/strong><\/h2>\n\n\n\n
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What is a PV firefighter switch? \u2192<\/a><\/div>\n\n\n\n
Combining DC and AC shutdown \u2192<\/a><\/div>\n\n\n\n
How can a PV system be disconnected safely? \u2192<\/a><\/div>\n\n\n\n
When is a PV firefighter switch required? \u2192<\/a><\/div>\n<\/div>\n<\/div>\n\n\n\n
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\"QFire<\/figure>\n<\/div><\/div>\n<\/div>\n<\/div><\/div>\n\n
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What is a PV Firefighter Safety Switch?<\/h2>\n\n
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A PV firefighter safety switch is a safety device designed to selectively disconnect photovoltaic DC circuits at string level. It is intended to protect firefighters, emergency responders and service personnel, particularly during fires or rescue operations in buildings equipped with photovoltaic systems. Since PV modules continuously generate DC voltage whenever exposed to light, the DC cables between the PV generator and the inverter remain live even after the AC side has been disconnected.By disconnecting the PV strings at string level, multiple modules can be safely isolated at a defined point close to the roof or building entry. As a result, no dangerous DC voltage remains on the cables between the firefighter safety switch and the inverter.This shutdown principle has proven to be technically robust, economically efficient and highly practical, particularly for commercial and industrial photovoltaic systems. Module-level shutdown systems are used in certain applications but usually involve increased technical effort, additional system complexity and higher costs.Modern firefighter safety switches with string-level disconnection can be integrated into fire protection and PV planning concepts and can be triggered manually or via external control signals such as emergency stop buttons or fire alarm systems. <\/p>\n<\/div>\n\n\n\n

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Selective DC string disconnection<\/h3>\n<\/div>\n\n\n\n
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Galvanic isolation according to IEC 60947-3<\/h3>\n<\/div>\n\n\n\n
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Protection for firefighters and emergency responders<\/h3>\n<\/div>\n\n\n\n
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Automatic or manual emergency shutdown<\/h3>\n<\/div>\n<\/div>\n<\/div>\n\n

Modern systems such as the QFire PV firefighter safety switch support automatic and manual emergency shutdown and are designed for safe PV generator disconnection according to IEC 60947-3.<\/strong><\/h4>\n\n
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Why PV Systems Need Emergency DC Shutdown?<\/h2>\n\n\n\n
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Photovoltaic systems can generate DC voltages of up to 1,500 V. Even when the inverter is switched off, the DC string cables may remain live.In emergency situations, this can:<\/p>\n\n\n\n

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Complicate rescue operations<\/strong><\/h4>\n<\/div>\n\n\n\n
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Endanger firefighters and emergency responders<\/strong><\/h4>\n<\/div>\n\n\n\n
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Delay firefighting operations<\/strong><\/h4>\n<\/div>\n\n\n\n
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A firefighter safety switch enables galvanic disconnection of the PV strings directly at the building entry point or close to the roof entry.<\/p>\n<\/div>\n\n\n\n

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\"QFire<\/figure>\n<\/div>\n<\/div>\n\n\n\n

The challenge of DC voltage: photovoltaic systems continuously generate voltage when exposed to light. Disconnecting the AC side alone does not automatically make a PV system DC-safe.<\/h4>\n<\/div><\/div>\n\n
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How Does a PV Firefighter Safety Switch Work?<\/h2>\n\n\n\n

A firefighter safety switch disconnects the PV strings automatically or manually from the inverter by galvanic isolation in emergency situations. Typical system components include: <\/p>\n\n\n\n

[1] Switching units installed close to the roof entry point [2] Control unit located near the inverter [3] Optional external emergency stop and connection to a fire alarm system<\/strong><\/h3>\n\n\n\n

Optional components include:\u25a0 integration of a fire alarm system\u25a0 integrated surge protection\u25a0 integrated fuses in the positive and\/or negative pole\u25a0 cluster technology for multiple roof areas\u25a0 integration into an AC-side shutdown concept <\/p>\n\n\n\n

In the event of shutdown, all PV strings are galvanically isolated so that the cables between the firefighter safety switch and the inverter become de-energised.<\/p>\n\n\n\n

Flexible integration for different photovoltaic system concepts \u2013 from small commercial installations to large-scale PV systems with multiple generator fields.<\/strong><\/h4>\n<\/div>\n\n\n\n
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\"Structure<\/figure>\n<\/div><\/div>\n<\/div>\n\n
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Technical Requirements for Modern PV Firefighter Safety Switches<\/h2>\n\n\n\n
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Modern firefighter safety switch systems must meet a wide range of technical requirements:<\/p>\n\n\n\n

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Certified according to IEC 60947-3<\/strong><\/strong><\/strong><\/h3>\n<\/div>\n\n\n\n
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System voltages up to 1,500 V DC<\/strong><\/strong><\/strong><\/h3>\n<\/div>\n\n\n\n
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String currents up to 20 A per string<\/strong><\/strong><\/strong><\/h3>\n<\/div>\n\n\n\n
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Safe shutdown without arcing<\/strong> – through galvanic isolation<\/h3>\n<\/div>\n\n\n\n
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Robust enclosures for outdoor installation (IP66\/IP67)<\/strong><\/h3>\n<\/div>\n\n\n\n
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Integration of surge protection and\/or string fuses<\/strong><\/h3>\n<\/div>\n\n\n\n
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Basic Principle of DC-Side Shutdown<\/h2>\n\n\n\n
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In photovoltaic systems, DC voltage is generated directly within the PV generator. This means that DC cables can remain critical even when only the AC supply has been disconnected.QFire addresses this issue by disconnecting the PV strings at string level close to the roof entry point or near the PV modules. The goal is to safely de-energise the cables between the switching unit and the inverter in the event of emergency shutdown. <\/p>\n\n\n\n

Advantages of this shutdown principle<\/strong><\/p>\n\n\n\n

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DC-side shutdown directly within the PV system<\/strong><\/h3>\n<\/div>\n\n\n\n
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Galvanic isolation of all PV strings<\/strong><\/strong><\/h3>\n<\/div>\n\n\n\n
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Reduction of dangerous DC voltage during fire emergencies<\/strong><\/strong><\/strong><\/h3>\n<\/div>\n\n\n\n
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Shutdown close to the roof entry point or near the PV modules<\/strong><\/strong><\/strong><\/strong><\/h3>\n<\/div>\n\n\n\n
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The QFire PV firefighter safety switch is designed for safe DC-side shutdown of photovoltaic systems. Unlike purely AC-side shutdown concepts, the DC voltage generated by the PV system is disconnected directly at the source.This helps prevent dangerous DC voltage from continuing to enter the building through the string cables during fire or emergency situations. Shutdown is achieved through galvanic isolation of all active conductors (positive and negative) for each PV string. After activation, the PV strings are de-energised so that no dangerous DC voltage remains on the cables or at the inverter inputs. <\/p>\n<\/div>\n\n\n\n

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Galvanic Isolation of PV Strings<\/h2>\n\n\n\n
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In the event of emergency shutdown, the QFire PV firefighter safety switch disconnects all connected PV strings galvanically and on both poles according to IEC 60947-3. Both the positive and negative conductors of each string are reliably isolated from the inverter to maximise safety during fire and emergency situations.<\/p>\n\n\n\n

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Clear distinction from motor switch solutions<\/strong><\/strong><\/h3>\n<\/div>\n\n\n\n
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Two-pole disconnection of positive and negative conductors<\/strong><\/strong><\/strong><\/h3>\n<\/div>\n\n\n\n
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Safe interruption of the DC connection<\/strong><\/strong><\/strong><\/h3>\n<\/div>\n\n\n\n
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DC-side shutdown directly at string level instead of AC-side isolation only<\/strong><\/strong><\/strong><\/h3>\n<\/div>\n\n\n\n
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Suitable for system voltages up to 1,500 V DC and string currents up to 20 A<\/strong><\/strong><\/strong><\/h3>\n<\/div>\n<\/div>\n\n\n\n
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\"Galvanic<\/figure>\n<\/div>\n\n\n
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Galvanic isolation completely interrupts the electrical connection between the PV generator and the inverter. After activation, the cables downstream of the QFire switching unit are de-energised. This principle significantly reduces DC-related hazards during fire emergencies and helps maximise safety for firefighters, emergency responders and service personnel. This shutdown principle significantly improves safety during fire and emergency situations by reliably interrupting dangerous DC voltage. At the same time, galvanic isolation remains effective regardless of the PV system configuration, string length or the number of connected generator fields. <\/p>\n<\/div>\n<\/div>\n<\/div><\/div>\n\n

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Reliable Triggering: Emergency Shutdown Mechanisms for PV Firefighter Safety Switches<\/h2>\n\n
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Multiple triggering methods ensure reliable shutdown in emergency situations \u2014 manually, automatically or via external control signals.<\/h4>\n\n

The QFire firefighter safety switch can be triggered in several different ways. In addition to manual shutdown via the control unit or external emergency stop buttons, the system also responds automatically to defined fault conditions. In the event of grid failure or undervoltage, the relays automatically open and galvanically disconnect the connected PV strings from the inverter. This ensures that the safety function remains active even if the supply voltage fails.The system also detects cable breakage or voltage drops within the control circuit and automatically initiates a safe shutdown. <\/p>\n\n

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Manual shutdown via main switch<\/strong><\/h3>\n<\/div>\n\n\n\n
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External emergency stop or key switch<\/strong><\/h3>\n<\/div>\n\n\n\n
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Automatic shutdown in case of grid failure<\/strong><\/h3>\n<\/div>\n\n\n\n
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Undervoltage detection<\/strong><\/h3>\n<\/div>\n\n\n\n
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Cable break monitoring<\/strong><\/h3>\n<\/div>\n\n\n\n
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Potential-free interfaces for fire alarm systems<\/strong><\/h3>\n<\/div>\n<\/div>\n\n\n\n
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Fail-Safe PrincipleIf the supply voltage fails or the control line is interrupted, the QFire PV firefighter safety switch automatically switches off and galvanically disconnects the PV strings from the inverter.The fail-safe principle increases safety during fire emergencies and helps minimise the risk of unintentionally live DC cables. <\/h4>\n<\/div>\n<\/div>\n\n
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Emergency Shutdown Options for the QFire PV Firefighter Safety Switch<\/h2>\n\n\n\n
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QFire LITE<\/h3>\n\n\n\n

QFire LITE <\/strong>is a standardised solution for DC-side PV string disconnection in photovoltaic systems. The shutdown is performed via the Switch Box, which is installed close to the PV modules or near the roof entry point.The system is triggered via a simple and clearly defined control interface, for example by an external emergency stop button or control signal. <\/p>\n\n\n

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QFire BIG<\/strong><\/h3>\n\n\n\n

QFire BIG <\/strong>includes a central Control Box with extended functionality for controlling the connected Switch Boxes.The Control Box provides visual status indication and supports integration of external emergency shutdown devices as well as connection to fire alarm systems (FAS) for automatic triggering. <\/p>\n\n\n

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QFire LITE shutdown can be triggered by:<\/strong><\/h4>\n\n\n\n
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AC-coupled shutdown via the grid supply in case of power failure \u2013 automatic restart <\/strong>when the grid returns<\/strong><\/h5>\n<\/div>\n\n\n\n
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External emergency stop<\/strong><\/h5>\n<\/div>\n\n\n\n
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Undervoltage caused by cable breakage or strong AC grid fluctuations<\/strong><\/h6>\n<\/div>\n<\/div>\n\n\n\n
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QFire BIG shutdown can be triggered by:<\/strong><\/h4>\n\n\n\n
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AC-coupled shutdown via the grid supply in case of power failure \u2013 automatic restart <\/strong>when the grid returns<\/strong><\/h5>\n<\/div>\n\n\n\n
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External emergency stop<\/strong><\/h5>\n<\/div>\n\n\n\n
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Undervoltage caused by cable breakage or strong AC grid fluctuations<\/strong><\/h6>\n<\/div>\n\n\n\n
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Manual shutdown via the Control Box <\/strong><\/strong><\/h6>\n<\/div>\n\n\n\n
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Connection to a fire alarm control panel<\/strong><\/strong><\/h6>\n<\/div>\n<\/div>\n<\/div>\n\n\n\n
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Discover QFire LITE \u2192<\/a><\/div>\n<\/div>\n<\/div>\n\n\n\n
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Discover QFire BIG \u2192<\/a><\/div>\n<\/div>\n<\/div>\n<\/div>\n\n\n\n
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Suitable external switches for PV firefighter safety switches (emergency stop, key switch, break-glass emergency stop)<\/h3>\n\n\n\n
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QFire BIG Control Unit \u2013 Central Control of the Firefighter Safety Switch System<\/h2>\n\n\n\n
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Monitoring of control signals<\/strong><\/strong><\/h3>\n<\/div>\n\n\n\n
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Status indicator<\/strong><\/strong><\/h3>\n<\/div>\n\n\n\n
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Control of individual or multiple Switch Boxes<\/strong><\/strong><\/h3>\n<\/div>\n\n\n\n
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Triggering via defined control interfaces<\/strong><\/strong><\/h3>\n<\/div>\n\n\n\n
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Potential-free interfaces for fire alarm systems (FAS\/FACP)<\/strong><\/strong><\/h3>\n<\/div>\n\n\n\n
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The Control Box is the central control element of the QFire PV firefighter safety switch system. It processes incoming control signals and transmits the shutdown commands to the connected Switch Boxes in the event of activation. Triggering is performed via a clearly defined control interface, for example through an external firefighter emergency button, a fire alarm system or an AC-coupled shutdown in case of grid failure.<\/p>\n\n\n\n

The DC-side shutdown itself is performed exclusively inside the Switch Boxes. The Control Box is responsible only for safe system control and monitoring.<\/h4>\n<\/div>\n<\/div>\n<\/div>\n<\/div><\/div>\n\n
\"Cluster<\/span>
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Cluster Control Box for Multiple Roof Areas and Generator Fields<\/h2>\n\n\n\n
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Star-shaped connection of multiple Switch Boxes<\/strong><\/strong><\/strong><\/h3>\n<\/div>\n\n\n\n
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Simultaneous shutdown of multiple roof areas<\/strong><\/strong><\/strong><\/h3>\n<\/div>\n\n\n\n
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Suitable for large and complex photovoltaic systems<\/strong><\/strong><\/strong><\/h3>\n<\/div>\n\n\n\n
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For larger photovoltaic systems with multiple roof areas or generator fields, the QFire Cluster Control Box is used. It enables central control of several Switch Boxes installed in different locations. The Switch Boxes are connected to the Cluster Control Box in a star-shaped configuration. This allows multiple roof areas or generator sections to be shut down centrally and simultaneously. <\/p>\n<\/div>\n\n\n\n

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Using cluster technology, complete PV system sections or multiple roof areas can be shut down simultaneously. This is particularly advantageous for commercial, industrial and large-scale solar installations<\/strong> with several generator sections or feed-in points. The cluster architecture also allows flexible expansion for large and complex photovoltaic system structures. <\/p>\n<\/div>\n<\/div>\n<\/div><\/div>\n\n

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The Switching Unit \u2013 DC-Side PV String Disconnection<\/h2>\n\n\n\n
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Two-pole galvanic isolation<\/strong> of the positive and negative conductors of each PV string<\/h3>\n<\/div>\n\n\n\n
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Designed for PV systems up to 1,500 V DC and 20 A per string<\/strong><\/h3>\n<\/div>\n\n\n\n
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Optional integrated surge protection and\/or integrated fuses in the positive and negative poles<\/strong><\/strong><\/strong><\/h3>\n<\/div>\n\n\n\n
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Depending on the configuration, multiple PV strings can be integrated into a single Switch Box. Optional surge protection modules can also be included to provide additional protection against transient overvoltages. <\/p>\n\n\n\n

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The Switch Box performs the actual DC-side shutdown of the PV strings. Each string is galvanically isolated on both poles so that no dangerous DC voltage remains at the output of the Switch Box after activation. <\/h4>\n<\/div>\n<\/div>\n<\/div><\/div>\n\n
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Standards and Regulations for PV Firefighter Safety Switches<\/h2>\n\n\n\n

The requirements for shutdown devices in photovoltaic systems are based on various standards and technical regulations. Important references include: <\/p>\n\n\n\n

\u25a0<\/strong> DIN VDE 0105-100 \u2013 Operation of electrical installations<\/h3>\n\n\n\n

\u25a0<\/strong> VDE-AR-E 2100-712 \u2013 Fire safety for photovoltaic systems<\/h3>\n\n\n\n

\u25a0<\/strong> IEC 60947-3 \u2013 Switches, disconnectors and switch-disconnectors for low-voltage applications<\/h3>\n\n\n\n

PV firefighter safety switches must reliably provide galvanic isolation of the photovoltaic system so that no dangerous voltage remains on the cables after shutdown.<\/p>\n<\/div>\n\n\n\n

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Normative FrameworkTechnical guidance is based, among other things, on VDE regulations such as DIN VDE 0100-712 and VDE-AR-E 2100-712, as well as recommendations issued by fire services for operations involving photovoltaic systems.For the switching devices themselves, the requirements of IEC 60947-3 are particularly relevant, as this standard defines the safe switching and isolation functions of switch-disconnectors. <\/h4>\n\n\n\n
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Are PV Firefighter Safety Switches Mandatory? \u2192<\/a><\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div><\/div>\n\n
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Frequently Asked Questions About PV Firefighter Safety Switches<\/h2>\n\n\n\n
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Ist ein Feuerwehrschalter f\u00fcr PV-Anlagen Pflicht?<\/div><\/summary>
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There is no universal legal requirement for PV firefighter safety switches.Whether a firefighter safety switch is required depends on local building regulations, the fire protection concept, project-specific requirements and the specifications of the fire service, insurer or system operator.<\/p>\n\n\n\n

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Learn More: Are PV Firefighter Safety Switches Mandatory? \u2192<\/a><\/div>\n<\/div>\n<\/div><\/details>\n\n\n\n
Wie funktioniert ein Feuerwehrschalter PV?<\/div><\/summary>
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A firefighter safety switch disconnects the PV strings on the DC side from the inverter.As a result, the cables between the Switch Box and the inverter become de-energised, while the PV modules themselves may continue to generate voltage when exposed to light.<\/p>\n\n\n\n

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Learn More About How the QFire Firefighter Safety Switch Works \u2192<\/a><\/div>\n<\/div>\n<\/div><\/details>\n\n\n\n
Was ist der Unterschied zwischen String- und Modulabschaltung?<\/div><\/summary>
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With string-level shutdown, multiple PV modules are disconnected together as one string, whereas module-level shutdown disconnects each individual module separately.String-level shutdown is considered a technically robust and economically efficient solution, particularly for larger commercial and industrial photovoltaic systems.<\/p>\n<\/div><\/details>\n\n\n\n

Wie viele Strings und MPPT kann eine QFire Schaltbox bedienen?<\/div><\/summary>
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A QFire Switch Box can support up to 12 MPPTs and up to 24 strings per system.By using additional Switch Boxes, the system can be expanded modularly. The architecture is scalable and can be adapted for larger photovoltaic installations.<\/p>\n\n\n\n

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Learn More About QFire BIG \u2192<\/a><\/div>\n<\/div>\n<\/div><\/details>\n<\/div>\n<\/div>\n<\/div>\n\n\n\n
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Here you will find an overview of all frequently asked questions about PV firefighter safety switches \u2192<\/a><\/div>\n<\/div>\n\n\n\n
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Plug & Play Installation of the QFire PV Firefighter Safety Switch<\/h2>\n\n\n\n
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Easy installation: no internal wiring of the control cables to terminal blocks required<\/strong><\/strong><\/strong><\/strong><\/h3>\n<\/div>\n\n\n\n
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Reduced installation effort: matching plug connectors supplied<\/strong><\/strong><\/strong><\/strong><\/h3>\n<\/div>\n\n\n\n
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Reduced risk of installation errors through clearly defined plug connections instead of individual terminal wiring<\/strong><\/strong><\/strong><\/strong><\/h3>\n<\/div>\n\n\n\n
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Project-specific configuration: connections adapted to the individual system layout<\/strong><\/strong><\/strong><\/strong><\/h3>\n<\/div>\n<\/div>\n<\/div>\n\n\n\n
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QFire systems are equipped with a plug-and-play connection concept designed to simplify and accelerate installation of the PV firefighter safety switch system. A key feature of this solution is the use of project-specific pre-wired connectors on both the Control Box and the Switch Boxes. <\/h4>\n\n\n\n

This connector-based installation concept significantly simplifies on-site assembly. Only the grid connection and grounding still require internal wiring. As a result, installation times are reduced, wiring errors are minimised and installation reliability is increased \u2014 especially in larger photovoltaic systems with multiple Switch Boxes.. <\/p>\n<\/div>\n<\/div>\n<\/div><\/div>\n\n

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Time-Delayed Shutdown for Large-Scale and Megawatt PV Systems<\/h2>\n\n\n\n
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Optimised shutdown logic for large photovoltaic systems<\/strong><\/strong><\/strong><\/strong><\/h3>\n<\/div>\n\n\n\n
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Time-delayed shutdown of large generator fields<\/strong><\/strong><\/strong><\/strong><\/h3>\n<\/div>\n\n\n\n
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Adjustable delay times between 1 and 10 seconds depending on system size<\/strong><\/strong><\/strong><\/strong><\/h3>\n<\/div>\n<\/div>\n\n\n\n
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For very large photovoltaic systems with high installed capacity, a time-delayed shutdown sequence can be beneficial. The QFire control system can be configured so that individual generator fields or Switch Boxes are shut down sequentially with a defined time delay.This staged shutdown process helps reduce electrical and mechanical stress and ensures controlled shutdown behaviour in large-scale photovoltaic installations. <\/p>\n<\/div>\n<\/div>\n<\/div><\/div>\n\n

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Application Example \u2013 QFire LITE Firefighter Safety Switch for Facade PV Systems on High-Rise Buildings<\/h2>\n\n\n\n
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High-rise photovoltaic systems with string-level shutdown for each floor<\/h3>\n\n\n\n

Photovoltaic systems installed on high-rise buildings, where individual PV strings are routed separately along the facade and into the building for each floor, create special requirements for DC-side safety and shutdown concepts.In such applications, insurers and fire services often require a clearly defined, reproducible and automatically effective shutdown solution in case of fire emergencies. The QFire LITE firefighter safety switch is particularly suitable for these types of installations. <\/p>\n\n\n\n

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Typical Project Requirements\u25a0 One PV string per floor with separate building entry \u25a0 Different string bundling configurations at the inverter \u25a0 High requirements for personal and emergency response safety \u25a0 Central shutdown option for the fire service \u25a0 Compliance with applicable DC switching and fire protection requirements<\/h4>\n\n\n\n
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Learn More About the High-Rise PV Application with QFire LITE \u2192<\/a><\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div><\/div>\n\n
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Solutions for Different Types of Photovoltaic Systems<\/h2>\n\n\n\n
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PV firefighter safety switches can be integrated into a wide range of photovoltaic system concepts, including:<\/p>\n\n\n\n

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\u25a0<\/strong> Commercial photovoltaic systems<\/h3>\n\n\n\n

\u25a0<\/strong> Industrial and ground-mounted solar installations<\/h3>\n\n\n\n

\u25a0<\/strong> Rooftop photovoltaic systems with multiple inverters<\/h3>\n\n\n\n
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The modular QFire system enables safe shutdown of everything from small commercial PV systems to complex large-scale photovoltaic installations with multiple generator fields.<\/p>\n<\/div>\n<\/div>\n<\/div><\/div>\n\n

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Who Is the QFire BIG System Designed For?<\/h2>\n\n\n\n
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PV planners and consulting engineers<\/strong><\/strong><\/strong><\/strong><\/strong><\/h3>\n<\/div>\n\n\n\n
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Installers and EPC companies<\/strong><\/strong><\/strong><\/strong><\/strong><\/h3>\n<\/div>\n\n\n\n
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Operators of large-scale photovoltaic systems<\/strong><\/strong><\/strong><\/strong><\/strong><\/h3>\n<\/div>\n\n\n\n
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The QFire system was specifically developed to meet the requirements of planners, installers and EPC companies.Thanks to its modular architecture, clearly defined system logic and simplified installation concept, the system can be integrated into a wide variety of photovoltaic system designs in compliance with applicable standards. The combination of technical safety, scalability and easy handling makes QFire a future-proof solution for photovoltaic systems of all sizes.<\/p>\n<\/div>\n\n\n\n

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Who Is the QFire LITE System Designed For?<\/h2>\n\n\n\n
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Installers and specialised electrical contractors<\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/h3>\n<\/div>\n\n\n\n
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Planners of smaller photovoltaic systems<\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/h3>\n<\/div>\n\n\n\n
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Electrical wholesalers and distribution partners<\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/h3>\n<\/div>\n\n\n\n
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The QFire LITE system is the standardised solution for small and medium-sized photovoltaic systems. It is based on the same proven safety principle as QFire BIG, but designed as a compact, non-expandable solution. QFire LITE is particularly suitable for straightforward photovoltaic system concepts where simple integration, a limited number of strings, clear system structures and cost-efficient implementation are key priorities.<\/p>\n<\/div>\n<\/div>\n\n\n\n

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View QFire BIG Product \u2192<\/a><\/div>\n<\/div>\n<\/div>\n\n\n\n
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View QFire LITE Product \u2192<\/a><\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div><\/div>\n\n
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Combined DC and AC shutdown for large PV systems<\/h2>\n\n\n\n
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In large PV systems, industrial projects and solar parks, the shutdown concept often has to be considered beyond the DC side alone. In practice, it may be necessary to disconnect the PV strings on the DC side close to the generator and, at the same time, shut down or block the AC side of the inverter or the feed-in path in a controlled manner. <\/strong><\/p>\n\n\n\n

QFire BIG can be integrated into such an overall shutdown concept. The QFire switch boxes provide generator-side galvanic isolation of the DC strings according to IEC 60947-3. In addition, the status contact of the QFire control box can be used project-specifically to provide an external AC-side shutdown signal \u2013 for example to a grid and system protection relay, an inverter enable input or a site-specific contactor solution. <\/p>\n\n\n\n

This makes QFire BIG particularly suitable for large commercial PV systems, megawatt projects, solar parks, industrial buildings and hybrid systems where DC string disconnection and AC-side enable interruption should not be considered separately.<\/p>\n\n\n\n

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Why is combined DC and AC shutdown useful in large PV systems?<\/h3>\n\n\n\n

In simple PV systems, it is often sufficient to disconnect the DC cables at a defined disconnection point. In larger installations or hybrid systems, the situation can be different. If, for example, a battery storage system is connected to the inverter or to the DC link, the DC link may remain charged. In unfavourable cases, this can lead to measurable voltage between the DC string cables and earth, even though the DC-side PV generator disconnection has already been triggered. <\/p>\n\n\n\n

For this reason, it can be useful or necessary in such systems to integrate both the DC side and the AC side into the shutdown concept at the same time. QFire BIG disconnects the PV strings on the DC side close to the generator. In parallel, an AC-side shutdown or enable circuit can be controlled via the status contact of the control box. This helps prevent the DC and AC side from reacting independently of each other during a shutdown sequence. <\/p>\n\n\n\n

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Can QFire BIG control a grid and system protection relay or inverter enable signal?<\/h3>\n\n\n\n

Yes. Depending on the project, the status contact of the QFire control box can be used to control external components. Typical applications include integration into a grid and system protection relay, an enable signal at the inverter or a site-specific contactor control on the AC side. <\/p>\n\n\n\n

In practice, the potential-free status contact is not used as a power switch, but as a signal or enable contact. For example, it can be integrated into the enable circuit of the grid and system protection relay. When QFire is switched off, the AC-side enable can also be interrupted at the same time. The grid and system protection relay or the downstream contactor solution then performs the actual AC-side shutdown. <\/p>\n\n\n\n

The exact wiring depends on the grid and system protection relay used, the inverter, the grid connection concept and the project requirements.<\/p>\n<\/div>\n\n\n\n

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How does the shutdown concept work in practice?<\/h3>\n\n\n\n

During a shutdown, QFire BIG performs the DC-side function: the connected PV strings are galvanically disconnected at the switch box close to the generator. This disconnects the DC cables from the QFire switch box towards the inverter. <\/p>\n\n\n\n

At the same time, the status contact of the control box can be used as a signal for the AC side. This signal can, for example, influence a grid and system protection relay, an inverter input or an external contactor control. In a typical setup, the grid and system protection relay then controls the AC contactors so that the feed-in path or AC path is also disconnected or blocked. <\/p>\n\n\n\n

This creates a coordinated shutdown concept: on the DC side, QFire BIG disconnects the PV strings; on the AC side, the enable signal or feed-in path is interrupted via the external components provided for this purpose.<\/p>\n\n\n\n

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For which systems is combined DC and AC shutdown particularly relevant?<\/h3>\n\n\n\n

Combined shutdown is particularly relevant for larger and more complex system structures. These include commercial rooftop systems, industrial PV systems, megawatt solar parks, PV systems with several inverters, hybrid systems with battery storage, systems with a central grid connection point and projects with special requirements regarding fire safety, grid connection or operational safety. <\/p>\n\n\n\n

In such projects, EPCs and planners must ensure that the shutdown does not only work at one single component, but fits the overall system concept. QFire BIG provides the DC-side PV generator disconnection and the option of integrating AC-side shutdown logic via the status contact. <\/p>\n\n\n\n

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What should be considered during planning?<\/h3>\n\n\n\n

The AC-side shutdown is not carried out directly by the QFire switch box as a power switching device. QFire BIG provides the DC-side galvanic isolation and can supply a signal for the AC-side shutdown logic via the status contact of the control box. <\/p>\n\n\n\n

The design of the AC components \u2013 for example grid and system protection relay, AC contactors, inverter enable, grid connection and protection concept \u2013 is always project-specific. The specifications of the inverter manufacturer, the requirements of the grid operator, the grid connection concept and the applicable technical rules must be taken into account. <\/p>\n\n\n\n

For large PV systems, combined DC and AC shutdown should therefore be considered early in the planning process. This allows the switching logic, status indication, emergency stop concept, control cable, grid and system protection relay and inverter enable to be coordinated properly. <\/p>\n\n\n\n

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Note on AC-side shutdownQFire BIG does not replace the grid and system protection relay or the site-specific AC switching equipment. However, the QFire control box can provide a signal for external AC components via the status contact. The exact implementation is always project-specific and depends on the system concept, inverter specifications, grid connection conditions and the applicable local technical requirements. <\/strong><\/p>\n\n\n\n

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Fachbeitr\u00e4ge & Pressemeldungen zum Feuerwehrschalter f\u00fcr Photovoltaik<\/strong><\/p>\n\n\n\n

Der Einsatz von Feuerwehrschaltern in Photovoltaik-Anlagen wird in der Branche intensiv diskutiert \u2013 insbesondere im Hinblick auf Sicherheit, Normung und Einsatz im Brandfall. Hier finden Sie ausgew\u00e4hlte Fachberichte, Branchenmeldungen und technische Einordnungen.<\/p>\n\n\n\n

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Intersolar 2026: Q3 Energie pr\u00e4sentiert KI-Konfigurator f\u00fcr Photovoltaik-Feuerwehrschalter<\/h3>\n\u2192<\/span>\n<\/a>\n\n\n\"\"\n

Wann ist ein Feuerwehrschalter bei Photovoltaik-Anlagen notwendig?<\/h3>\n\u2192<\/span>\n<\/a>\n\n\n\"\"\n

Generatorfreischaltung mit dem Feuerwehrschalter<\/h3>\n\u2192<\/span>\n<\/a>\n\n\n\"\"\n

Q3 PV-Feuerwehrschalter \u201eQFire\u201c erh\u00e4lt Zertifizierung nach IEC 60947-3 <\/h3>\n\u2192<\/span>\n<\/a>\n\n\n\"\"\n

QFire PV Feuerwehrschalter Schulung: Praxisnahe Schulung f\u00fcr Planer und Installateure<\/h3>\n\u2192<\/span>\n<\/a>\n\n<\/div>\n<\/div>\n<\/div>\n<\/div><\/div>\n\n
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Q3 YouTube Video Explains the QFire PV Firefighter Safety Switch \u2013 Safe DC-Side Shutdown in Fire Emergencies<\/h2>\n\n\n\n

Building insurers, authorities and fire services increasingly require automatic shutdown solutions for photovoltaic systems during fire emergencies or rescue operations. The main concern is the dangerous DC voltage that may remain present in the DC cables even after the building\u2019s AC power supply has been disconnected. <\/p>\n\n\n\n

The firefighter safety switch enables safe DC-side shutdown of the PV strings directly at the building entry point or roof entry area. The system is triggered via a defined control interface, for example by disconnecting the building power supply, using an external firefighter emergency button or through connection to a fire alarm system. During activation, the PV strings are galvanically isolated so that no dangerous DC voltage is routed into the building. <\/p>\n\n\n\n

Once the power supply is restored after an emergency event, the system can automatically restart. Manual intervention at the photovoltaic system or on the roof is not required in this case. This ensures both operational safety and emergency response safety for the photovoltaic installation. <\/p>\n\n\n\n

The video clearly demonstrates the operating principle of a PV firefighter safety switch in a practical application scenario.<\/p>\n<\/div>\n\n\n\n

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