Fireman’s switch PV: How does it work?

Photovoltaic fireman's switch for automatic and manual disconnection of the PV strings

With the QFire Switch fireman's switch, all lines from the disconnection box on the roof are galvanically isolated from the PV generator in the event of switching. This means that all DC cables in the building are de-energized. Switching takes place via the control box, which is ideally installed near the inverters or connected to another point in the AC grid.

The main advantage of the system with AC-coupled switch-off is that, for example, in the event of a fire, there is no need to search for a switch or it is no longer accessible. When the AC grid is switched off, the DC lines from the switch box on the roof are also automatically disconnected. When the AC grid is reconnected, the system automatically goes back into operation.

The Q3 QFire fire switches are certified to IEC 60947-3 and are planned to customer specifications and built by us in Kaufbeuren - Made in Germany. If required, we combine all connection technology components - overvoltage protection, string current measurement, etc. - and integrate them into the switch-off box. This box is also customized in terms of the number of strings to be switched off. If metal enclosures are required for industrial applications - no problem!

The inverter is usually installed centrally in the building near the domestic power distribution. This can be switched off, as can all the electricity in the house. What cannot be switched off is the voltage coming from the modules: up to 1,000 volts of direct current remain in the building. Please note: from 120 V direct current, this is considered life-threatening.

This applies not only to the fire department in the event of a fire, according to their "Recommendation for action on photovoltaics", a minimum distance of up to 5 meters (depending on whether spraying or extinguishing jet) must be maintained from live parts, but also to maintenance and cleaning work, etc. Self-protection takes precedence over external protection.

Therefore, the unanimous wish is for a safe disconnection device for photovoltaic modules in order to be able to completely de-energize the building in the event of a fire, including the DC side.

QFire is a PV generator disconnection device for the automated galvanic isolation of PV strings in accordance with DIN EN 60947-3:2020.

The set consists of a control box and one or more switch box(es).

The QFire control box is installed centrally near the inverter or in another accessible location. The QFire switch boxes are installed near the module at the roof entrance, from where all cables coming from the roof can be switched off safely and without arcing using special high-performance relays. This means that the entire direct current supply can be interrupted from a central point.

The QFire fireman's switch is switched off

• Manually on the control box
• via an external EMERGENCY OFF or key switch
• Coupled via fire alarm control panel
• AC coupled via the power grid in the event of a power failure - if the grid is reconnected, the system automatically goes back into operation
• due to undervoltage caused by cable breakage or severe fluctuations in the AC grid

We will be happy to send you an offer, free of charge and without obligation, of course. Please let us know in advance:

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Central emergency shutdown for PV systems, customized variants adapted to the respective system

Suitable for fire alarm systems, can be connected to fire alarm control panel

Suitable for all modules/inverters, regardless of manufacturer

Switches back on automatically after a power failure

Safe disconnection of the PV generator even in an emergency

Arc-free switching thanks to modern switching technology

Complete set; modularly expandable and easy to install

Control box can be switched on and off using an external key switch

AC-coupled, can therefore be triggered at any time via the mains supply

Status can be transmitted to the alarm center via a potential-free contact