QFire BIG PV Firefighter Safety Switch for Large Solar Systems
Modular and expandable DC shutdown system with galvanic isolation – designed for large and complex photovoltaic installations.
Application Area of the QFire BIG PV Firefighter Safety Switch
The QFire BIG PV firefighter safety switch was developed specifically for large commercial and industrial photovoltaic systems. By providing galvanic isolation of PV strings according to IEC 60947-3, the system enables safe shutdown of the DC cables between the PV generator and the inverter – for example in case of fire, maintenance or service work.
With a central Control Box, project-specific DC Switch Boxes, optional cluster technology and external emergency stop integration, QFire BIG can be flexibly integrated into a wide range of photovoltaic system concepts.
Large Industrial and Commercial Roofs
Multiple Roof Areas
Expandable Photovoltaics Projects
Multiple Inverters & MPP Trackers
Complex System Structures
Increased Safety Requirements
The modular system architecture is particularly suitable for complex rooftop structures, multiple generator fields and large PV systems with many strings. Depending on the system size, Switch Boxes for 2 to 24 strings are available – with system voltages up to 1,500 V DC and up to 20 A per string.
For large sites, several QFire systems can be controlled centrally via the QFire Cluster Control Box. This enables multiple buildings or separate generator fields to be shut down from one central point.
Optional components include surge protection, external emergency stop buttons, key switches, status contacts and online monitoring via QFire.LIVE.
QFire BIG is a PV firefighter safety switch system for large solar installations with multiple generator fields, complex rooftop structures and increased safety requirements.
Modular System Architecture for Generator-Side PV Shutdown of the PV Firefighter Safety Switch
QFire BIG enables galvanic isolation of PV strings between the generator field and the inverter. Typical system components include:
Separation of control logic [2] and DC switch boxes [1]
Expandable with additional switch boxes
Integration of fire alarm system and/or external emergency stop buttons [3]
Centralised or cluster-based shutdown
The QFire BIG system has a modular structure and consists of a central Control Box, optional Cluster Control Boxes and DC Switch Boxes for up to 24 strings per box.
The Switch Boxes are built project-specifically and can optionally be equipped with surge protection and fuses.
Optional components are:
■ Fire alarm system integration
■ Integrated surge protection
■ Integrated fuses in the positive and/or negative poles
■ External emergency stop button
■ Cluster technology for multiple roof areas
■ Online monitoring
■ Time delay module for sequential shutdown of large systems
In the event of shutdown, all strings are galvanically isolated so that the cables between the QFire Switch Box and the inverter become de-energised.
This separation of control and switching functions enables flexible adaptation to system size, rooftop structure and safety requirements.
Galvanic Isolation of DC Strings
In the event of activation, the QFire PV firefighter safety switch galvanically isolates all connected PV strings on both poles according to IEC 60947-3. This reliably disconnects the positive and negative conductors of each string from the inverter – for maximum safety during fire and emergency situations.
Clear distinction from motor switch solutions
Two-pole disconnection of positive and negative conductors
Safe interruption of the DC connection
DC-side shutdown directly at string level instead of AC-side isolation only
Suitable for system voltages up to 1,500 V DC and up to 20 A per string
Galvanic isolation completely interrupts the electrical connection between the PV generator and the inverter. After activation, the cables downstream of the QFire Switch Box are de-energised.
This principle significantly reduces DC-related hazards during fire emergencies and helps maximise safety for firefighters, emergency responders and service personnel.
At the same time, galvanic isolation remains effective regardless of the PV system configuration, string length or the number of connected generator fields.
QFire BIG Control Box for Large PV Systems
Central control and coordinated shutdown of PV strings
The QFire Control Box operates with dedicated system logic. This ensures that the shutdown function remains clearly defined and reliably controllable, even in complex system structures with multiple roof areas or long cable routes.
The Control Box is the central control element of the QFire BIG generator shutdown system. It processes all incoming control signals and coordinates the connected Switch Boxes. In the event of activation, the Control Box initiates a defined and safe shutdown of all connected DC strings – regardless of quantity, distance or system size.
By clearly separating control logic and DC switching function, the electrical structure remains transparent and standards-compliant. The Control Box itself does not switch DC loads but acts as a central logic and interface level. This makes the system particularly suitable for larger and complex photovoltaic systems with multiple generator fields or future expansion requirements.
QFire BIG PV Firefighter Safety Switch:
Cluster Technology for Large PV Systems
Cluster technology enables the central shutdown of multiple generator fields via a common control logic.
QFire BIG Cluster Control Box for Central Shutdown of Distributed Generator Fields
Additional higher-level, star-shaped shutdown architecture
For large and complex photovoltaic systems with multiple roof areas or generator fields, the Cluster Control Box expands the QFire BIG system with a higher-level, star-shaped shutdown architecture.
The Cluster Control Box extends the functionality of the QFire BIG generator shutdown system for installations with multiple roof areas, halls, building sections or widely distributed generator fields. It acts as a higher-level distribution and coordination unit and enables star-shaped connection of multiple Switch Boxes or system segments.
With this cluster architecture, large and spatially complex photovoltaic systems can be shut down reliably and simultaneously. The shutdown logic remains clearly defined – regardless of the number of connected Switch Boxes or the physical size of the installation.
This makes the QFire BIG PV firefighter safety switch system with Cluster Control Box particularly suitable for industrial buildings, commercial facilities, logistics centres and projects with future expansion requirements.
Triggering Methods and Interfaces
Plug + Play Installation
QFire BIG Switch Box – Modular DC Shutdown with Galvanic Isolation
For safe shutdown up to 1,500 V DC / 20 A per string
The QFire BIG Switch Boxes perform galvanic isolation of the PV strings directly at the generator field. They provide the central DC switching function of the system and ensure safe, standards-compliant isolation of the connected strings in the event of shutdown.
Thanks to the modular design, the Switch Boxes can be flexibly adapted to different system structures – from smaller sub-generators to large photovoltaic systems with multiple roof areas and high string counts.
Each Switch Box performs galvanic isolation of the connected PV strings directly at the installation point.
QFire BIG PV Firefighter Safety Switch: Project-Specific Instead of Off-the-Shelf
QFire BIG Switch Boxes are designed, planned and manufactured project-specifically. String count, connection technology, protection components, enclosure sizes and interfaces are individually adapted to the respective system structure.
The result is not an off-the-shelf standard product, but a technically clean, standards-compliant and future-proof shutdown solution – Made in Germany.
String Count
■ Switch boxes from 2 to 24 PV strings
■ Flexible string reductions between input and output
Connectors and Connection Options
■ Standard: MC4-Evo2 by Stäubli
■ Alternatives such as H4, Sunclix or terminal connection technology possible
DC Surge Protection
■ Optional integrated surge protection
■ Standard: Q3 surge protection T1+2 up to 1,500 VDC
■ Alternative surge protection manufacturers available on request
PV Fuses
■ Optional integrated PV fuses
■ Available in the positive and/or negative pole
Project Inquiry for QFire BIG PV Firefighter Safety Switches
Would you like to configure the QFire BIG system for a specific project, have technical details reviewed or select the right system configuration for your photovoltaic installation?
Using the following inquiry form, we collect all relevant project data in a structured and traceable way.
You can also submit wiring diagrams, string plans or other technical documents directly with your inquiry. Based on this information, we review the technical requirements, configure the QFire BIG system for your project and coordinate the required components.
If we need additional information, we will contact you. Otherwise, you will receive a project-specific quotation.
PV Firefighter Safety Switch Project Inquiry
Project-specific inquiry for configuring the QFire system, selecting the right components and preparing a quotation.
Technical Documents for PV Firefighter Safety Switches
Datasheets, certificates and technical documentation for QFire BIG and LITE, Control Boxes, Switch Boxes and accessories.
Functionality + Technology QFire PV Firefighter Safety Switch
Technical fundamentals of DC-side disconnection, system design, triggering methods and galvanic isolation.
FAQ on PV Firefighter Safety Switch
Answers to frequently asked questions about application, standards, triggering concepts, mandatory requirements, and operation of firefighter switches.
Technical Articles and Industry News About PV Firefighter Safety Switches
The use of firefighter safety switches in photovoltaic systems is widely discussed within the solar industry — particularly regarding safety, standards and emergency response concepts.
Here you will find selected technical articles, industry news and technical background information related to PV firefighter safety switches.
When Is a Firefighter Safety Switch Required for Photovoltaic Systems?
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Generator-Side Shutdown Using a Firefighter Safety Switch
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Q3 QFire PV Firefighter Safety Switch Receives IEC 60947-3 Certification
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