Fire detection for suppression system FDU WRS LK


The fire detection unit FDU LK could be assembled with any and operating every electric extinguishing. If it senses over temperature it releases the electric power of 24V DC 10 W to the magnetic valve. Lower warning temperature and pressure check of the agent cylinder could be set voluntary. The release by signals of electric linear sensors or temperature switches is optional as well as manual release.




Green screen displays

Functionality ok


In the following example two temperature sensors are connected and are reading

the ambient temperature. Sensor 3 and 4 are shunted by a jumper and therefore

not active. The number of transferred messages (225) to the server is listed in parentheses.









Flashing yellow screen displays



If no sensor or jumper is connected, then the display shows < Err! >

as it is shown for example on the next photo at location T4.


If the background is yellow there is a problem, which is determined not only by the

missing sensors but either the disconnection of the solenoid or pressure sensor or it

is detecting low pressure of the agent container as well as a short circuit. A warning

message appears even if only one of the following momentums exists.



Pressure switch:



The terminals for the pressure switch and the solenoid coil are strong spring connectors

at the printed circuit board. Here is a sketch of the wire diagram thereof.

A cable set could be supplied on request.


























However, this feature requires the assembly of two resistors of 500 Ω and 1 kΩ 1 W

connected direct to the terminals of the pressure switch as shown. The wiring of the

terminal to the solenoid of the magnetic valve is also monitored. The following example

of the display shows everything is in good order except the pressure sensor, which

perceives no pressure indication.


PDF download: >> FDU_SNS_ASSY_V8








Flashing red screen displays

Fire Alarm


Now all 4 sensors are connected to the PCB, one measures the temperature

of 138 °C, which means fire in the engine compartment and therefore the

24 VDC 10 W power output was released to the solenoid and the fire alarm

is displayed on the screen. The alarm and a lower warning temperature could

be freely set.The indication board prevents optical and acoustical signals to the

driver. As an option the separate horn could be connected amplifying the noise to

90 dB in case of fire. The time of sounding could be set voluntary.
















No connection or short circuit

No connection, low pressure or short circuit

sensor not in place or missing shunt



Easy Assembly of FDU-SNS in

the engine compartment



1) Attach the body with cable ties to the top of the compartment and supply 24 VDC. Brown (+).



2) Check the distance to the hot spots and cut a ½ inch Marten hose to this length and push the free end of the SEH sensor through it.



3) Press the sensor head completely into the Marten hose.



4) Lose the nut of the cable gland and insert the other end of the spiral hose.



5) Plug the free connector into the corresponding socket at the circuit board and remove the black shunt.



6) Screw the cable gland nut and close the cover of the body water tight (lP 65). Check that the rubber gasket in the lid of the body will not be damaged.



7) Place the sensor head above the dangerous hot spots .

Detector head is very sensitive for short response.

Handle with care.





Attach the SNS body with cable ties at the top of the engine

compartment and supply 24 VDC to the cable. Brown wire (1) for plus blue wire (2) for ground. Check the bar code is visible.


• Standard type has 5 sensors

• Option up to 6 engine boxes

• Up to 30 fire sensors could

  communicate with the display





Fire detector SNS

We like Blackay and

Rotarex Compact Line Systems






Tel.: +33 6 14 47 23 34





Copyright © 2019 | Manfred K. Müller Temperature Controls