Not only fire doors need hold-open systems
FAHO has developed an overflow unit with fire protection properties for overflow and afterflow openings.
Openings in fire protection walls are not only closed by fire doors. There are also many smaller openings. Just like doors, these should normally be open so air can circulate. But in case of fire, they need to close. However, an overflow opening cannot be closed by a door. Rather, in the event of an alarm, a calcium-silicate block is pushed into the wall opening by a spring. The expanded graphite on the outside of the block expands and closes the opening.
But how does a hold-open system work in such a case?
Company FAHO has developed a sophisticated, self-sufficient system, the overflow element ARÜ, approved by the DIBt as a “fire-resistant closure type ARÜ of special design and application”. Here, all components are fitted in the smallest possible space. DICTATOR’s new RZ-24-05 central unit for hold-open systems is the ideal solution here due to its very small size. It is no bigger than a normal manual switch, but it includes all main functions (power supply, evaluation unit and controller) in one single device. In the case of the ARÜ, the RZ-24-05 is supplied in a custom version with the logo of the FAHO company.
There are a smoke detector RM 4000 and a DICTATOR electromagnet connected to the central unit. The electromagnet keeps the spring tensioned, which pushes the aforementioned calcium-silicate block into the opening in the event of an alarm. Despite its small diameter, the magnet has a high holding force of 600 N and is equipped with longer connection strands to make wiring within the hold-open system as easy as possible.
The hold-open system for supply and exhaust air openings and pressure equalisation openings in fire walls has been approved by the Deutsches Institut für Bautechnik in Berlin (DIBt) (approval no. Z-6.5-2217).
The ARÜ overflow element is used in wall openings for overflow ventilation or air extraction systems or also for pressure relief in fire protection airlocks. It is self-sufficient, i.e. it can easily be fitted to individual ventilation openings and does not require a complicated control system or connection to a building fire alarm system.
A view into the ARÜ. In the middle you can see the “heart” of the hold-open system: the central unit RZ-24-05, no bigger than a light switch, the smoke detector RM 4000 at the top right, the tensioned spring held by the magnet and the calcium silicate block that is pushed into the ventilation opening in case of fire.
On the left, the ARÜ can be seen in its normal state. The magnet is energised by the RZ-24-05 central unit and can thus keep the spring in a tensioned state. The calcium-silicate block thus remains inside the ARÜ. In the event of a fire, smoke penetrates the ARÜ 90, the smoke detector RM 4000 integrated in it is triggered and the RZ-24-05 central unit switches off the current to the magnet. The spring presses the calcium-silicate block into the overflow opening and closes it fireproof. It is not possible for the fire to spread via ventilation ducts. See video here.
The dimensions of the entire “hold-open system” depend on the diameter of the overflow opening. They are 411 x 300 x 200 mm for the smallest version. This is why DICTATOR’s space-saving components are so important.
Related projects
Automated fire door in the showroom of a car dealership
Automation solution for 93 m wide sliding door in shopping center
Custom gate operator for sliding fire door in a bus factory
