Central unit RZ-24  with power supply & tripping device

For power supply and evaluation of fire detectors


  • Complies with the requirements of the norm EN 14637
  • Tested and approved by the DIBt (German institute for building engineering)
  • With integrated manual release button
  • Due to its high power (900 mA), even large hold-open system can be operated with just one central unit
  • Optionally available in a large casing, with sufficient space for additional components such as relay boards or an emergency power supply (see Additional components for RZ-24)
  • Also suitable for EX-proof hold-open systems


  • All essential functions (power supply, control of the release devices such as smoke detectors, Reset, hand release button)  are combined in one device, so that only fire detectors and electromagnets have to be connected
  • Resetting the hold-open system after an alarm is also done with the central unit
  • In addition to the alarm in case of fire, malfunctions such as short circuits or wire breaks in the system are also detected
Additional functions & components

Product information

Supply voltage85 VAC - 265 VAC, 50/60 Hz
Power consumptionabout 30 W, own consumption about 30 mA
Additional switching contactpotential-free contact 8 A/<250 V~/AC1 (relay fallen off = tripping)
Secondary output voltage24 VDC ±5 %
Secondary total load0.9 A supply of fire detectors, electromagnets and other consumers)
Operating temperature-25 °C to +40 °C
IP ratingIP 64 when IP 64 cable inlets are used
Casingplastic casing in ABS, light grey, with 4 threads M16 for cable inlets
Emergency power supplyon demand, up to max. 12 minutes (at a consumption of 70 mA)
Keys on the casing integrated hand release key (1)
integrated RESET key (2)
key quitting horn: switches the horn off after an alarm. (4)
Indications on the casingGreen LED = "operation" (normal operation) (3)
Red LED = "alarm" (error or alarm) (3)
Dimensions122 x 124 x 55 mm (height x width x depth)

Functions of the central unit RZ-24

  • Manual release of the hold-open system by means of either the integrated hand-release switch or an additional one (mounted in the immediate vicinity of the fire door).
  • Tripping the hold-open system by the connected fire detectors or by the potential-free contact of a fire alarm central.
  • Reset of the complete hold-open system: first, use the hand-release switch to reset the fire detector and then the reset switch on the central unit RZ-24 to reset the whole system.
  • Automatic RESET after a power cut (NOT after a manual tripping or a fire alarm !!)
  • Integrated overcurrent protection: if there are too many consumers connected, the power supply automatically cuts off.
  • Potential-free contact for signalling the tripping, e.g. for sending the alarm-status to a cental control system, an additional warning device, etc. If there is a door drive integrated in the hold-open system, the contact is used to cut the power supply of the door operator in the event of an alarm, so that the door is closed mechanically (door closer, closing spring or counterweight).
  • Status indication for normal operation and alarm on the cover of the central.

Additional functions – optional

  • Rechargeable battery buffering: depending on the consumption of the connected fire detectors, electromagnets and other consumers – up to 12 minutes can be bridged in the event of failure of the 230 VAC supply (usable capacity 0.022 Ah).
  • Additional relay contacts (circuit boards with one, two or four relay contacts, each a change-over contact 2 A/30 VDC).
  • Additional circuit board for the automatic reset of the RZ-24 central unit after a power outage or fire alarm (however, the tripping fire detector has to be reset additionally by means of a hand-release switch).
  • Further options on demand.

More information on Additional functions and accessories for central unit RZ-24

All dimensions in mm

Installation guidelines

  • For the wiring work, the housing has 4 cable inlets M16 with IP 64 screwed cable glands at the bottom (the larger housing has 6 cable inlets)
  • If required, the housing can be mounted with the cable inlets facing upwards. For this, simply turn the cover. However, it should be taken into account that protection class IP 64 is no longer given for cable entries from above!
  • In Germany (consult regulations in your own country), when determining the number of required fire detectors, it has to be taken into consideration that an additonal fire detector has to be installed near the RZ-24 when the central unit is not placed within the detection range of one of the detectors mounted on the door!
  • The scope of supply of the RZ-24 also contains a 3.9 kΩ resistor, needed when connecting the fire detectors RM 4000/WM 4000.
  • For explosion-proof hold-open systems, the control unit RZ-24 must be installed outside the hazardous area! There is a special version with fireproof casing available upon request for installation within the hazardous area.

Inputs / Outputs

Central unit RZ-24 - inside


  • Mains connection
  • Fire alarm loop: 24 V feed-in of the smoke/heat detectors and evaluation of the status informations
  • External hand release switch (is integrated in the fire alarm loop)


  • Feed-in of the hold-open system (e.g. electromagnets)
  • Feed-in of additional consumers as e.g. external signallers. They allow to signal the closing of a fire protection closure during alarm acoustically and also optically.
  • Potential-free relay contact for relaying the tripping (only for hold-open systems without door operator).

Block diagram

EX Hold Open System Components

A 3.9 kΩ resistor is inserted at the terminals 4 and 5 in the factory. This resistor has to be removed before connecting the fire detectors and then inserted in the last detector of the detection loop.

Central unit RZ-24 for hold-open systemspdf2020/02/11
DWG Central Unit RZ-24, 040553dwg2018/10/08

Order Information

DescriptionPart No.
RZ-24 central unit with power supply and tripping device, 0.9 A040553
RZ-24 central unit with power supply and tripping device, 0.9 A, IP 64, 202x152x90 mm (big casing)040554