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HISbox fireman switch – safe shutdown of PV strings in the event of fire
Photovoltaic systems continue to generate electricity even after the grid supply has already been switched off. This is precisely where a risk arises in the event of fire: DC cables inside the building remain live and can endanger emergency responders. The HISbox fireman switch ensures that DC voltage is reliably switched off in an emergency – automatically, quickly and in compliance with standards.
Maximum safety when it matters most
In the event of fire, every second counts. As soon as the fire brigade disconnects the building's main supply, the fireman switch for combiner boxes automatically de-energises the PV strings.
This allows rescue teams to extinguish fires safely, and the risks to people and buildings are significantly reduced.
Fire brigades, fire safety authorities and insurers increasingly demand this solution – the HISbox fireman switch meets exactly these requirements.
HISbox® PV combiner boxes at a glance
The Fireman Switch is one component of our PV combiner boxes. The overview page provides information on all components and on the right configuration for your system class.
Why a fireman switch is important for PV systems
PV modules continue to produce energy as soon as light hits them. Even in an emergency.
This means:
DC cables inside the building remain active without shutdown
Firefighting and rescue operations are hampered
Risks to emergency responders increase
Insurers may impose conditions if no shutdown device is in place
The HISbox DC fireman switch disconnects the DC strings at exactly the right point – at the building entry or directly near the modules. This prevents PV cables inside the building from continuing to carry voltage in the event of fire.
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We are happy to advise you on the right fireman switch solution
How the HISbox fireman switch works
Its operation is based on three intelligent triggering mechanisms that work independently of one another or in combination.
As soon as the fire brigade or service personnel interrupts the 230 V supply, the fireman switch automatically disconnects the PV strings from the inverter.
If the temperature inside the box rises above a critical value (e.g. 100 °C), the fireman switch trips automatically and prevents thermal risks.
For certain installation situations, a PV emergency-stop button can be integrated.
This allows the fireman switch to be triggered without having to shut down the entire building distribution.
After a fire or fault, as soon as the mains voltage and temperature are back within the safe range, the system reactivates automatically.
No manual reset is required – this saves time and simplifies recommissioning.
Variants for every system architecture
The HISbox series offers a wide range of fireman switch variants that adapt precisely to the design of modern PV systems. The combination of modular construction and project-specific configuration ensures that a fireman switch variant is available for every solar installation.
1 to 12 MPPTs, each with different numbers of strings
(ideal for small, medium and large rooftop systems)
1–8 strings per MPPT, matched to the manufacturer and inverter layout
with or without integrated surge protection (Type 2+3 or Type 1+2+3)
load-break switch and undervoltage release integrated as standard
polycarbonate or glass-fibre-reinforced plastic
transparent or opaque covers
protection rating up to IP65 for outdoor use
Request the right HISbox with fireman switch for your project now
Areas of application and technical highlights
The HISbox fireman switch is suitable for all systems in which DC cables are routed into the building or where increased fire safety requirements apply.
Commercial and industrial buildings
modern rooftop systems with many MPPT inputs
residential buildings where DC cables run through interior spaces
existing systems that are being upgraded to current fire safety requirements
repowering projects in which older PV systems are upgraded in terms of safety
Whether new build or refurbishment – the HISbox fireman switch offers the same reliable shutdown function everywhere.
The HISbox PV system fireman switch meets the highest requirements for safety, robustness and operational reliability:
System voltages up to 1000 V DC or 1500 V DC
automatic mains UVR release for building integration
temperature-controlled shutdown at 100 °C
robust, UV-resistant outdoor enclosures
protection rating IP54 to IP65
short shutdown times for maximum safety
integrated pressure equalisation to reduce condensation
automatic reactivation once a safe state is reached
These features make the HISbox one of the most reliable solutions for rooftop PV systems on the market.
HIS Renewables supports installers, planners and EPCs in selecting the right solar fireman switch and with all questions concerning:
MPPT and string sizing
selecting suitable safety and triggering variants
differences between module-level and building-level installation
standards & fire safety requirements
integration into existing HISbox or third-party systems
The result is a well-thought-out, safe and standards-compliant overall solution – with no additional planning effort for the project team.
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Questions about sizing, standards or integration? We support you from planning through to implementation.
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