Fire-Extinguishing System, Basic Function - GF86.10-P-9900A

Model All (CAR) with code Z21 (Fire extinguishing system) 

Courtesy of MERCEDES-BENZ USA

Overview 

This document contains information on:

• General 
• Function requirements 
• Function 
  • Selftest 
  • Monitoring 
  • Pressure monitoring 
  • Output of fault messages 
  • Activate fire-extinguishing system 

General 

The fire-extinguishing system can fight fires under the vehicle and in the engine compartment. The fire extinguishing system can be actuated manually or automatically. Extinguishing powder is used to fire fighting.

The nozzles on the fire extinguishing system are distributed on the vehicle floor and the engine compartment as follows:

• 2 nozzles in area of rear bumper
• 3 nozzles on left passenger compartment armor plate
• 3 nozzles on right passenger compartment armor plate
• 2 nozzles in left and right front upper engine compartment
• 2 nozzles in area of front bumper

Function requirements 

• Vehicle speed v < 10 km/h

Function 

Selftest 

When circuit 15 is switched on, the LED in the fire-extinguishing system button and the LED in the emergency fresh-air system/fire-extinguishing system activation button in the Guard operating unit light up for approx. t = 1 s. If the LED's still illuminate after expiration of this time, the fire extinguishing system and emergency fresh air system control unit recognizes a fault and the function of the fire extinguishing system is limited. The warning buzzer is actuated and the a message is indicated in the instrument cluster.

Monitoring 

The fire extinguishing system and emergency fresh air system control unit monitors the following component parts for signal failure and plausibility:

• Emergency fresh air system/fire extinguishing system activation button
• Fire extinguishing system button
• Fire extinguishing system temperature sensor
• Extinguishing agent tank squib

Pressure monitoring 

The pressure in the extinguishing agent tank is detected by the extinguishing agent tank pressure sensor. The fire extinguishing system and emergency fresh air system control unit directly reads in the signals from the fire extinguishing agent tank pressure sensor. At a pressure of approx. p < 40 bar or in the case of a detected fault in the fire-extinguishing system, the fire extinguishing system and emergency fresh-air system control unit outputs a warning message via the warning buzzer, the LED in the fire-extinguishing system button and the instrument cluster.

Output of fault messages 

A message is output by the instrument cluster in the event of a malfunction to indicate errors to the driver.

Activate fire-extinguishing system 

The fire extinguishing system can be actuated manually or automatically.

Automatic actuation:

Temperature monitoring consists of two temperature sensor circuits that enable automated staggered actuation and redundancy in the sensor circuits.

The temperature sensor circuit 1 includes the following temperature sensors:

• Fire-extinguishing system temperature sensor (b)
• Fire-extinguishing system temperature sensor (c)
• Fire-extinguishing system temperature sensor (e)

The temperature sensor circuit 2 consists of the following temperature sensors:

• Fire-extinguishing system temperature sensor (a)
• Fire-extinguishing system temperature sensor (d)
• Fire-extinguishing system temperature sensor (f)

The fire extinguishing system temperature sensors permanently sense the ambient temperature. The fire extinguishing system and emergency fresh air system control unit directly reads in the signals from the fire extinguishing system temperature sensors.

If the temperature threshold of approx. T = 160°C is exceeded at just one of the two temperature sensor circuits, the fire extinguishing system and emergency fresh-air system control unit activates the fire-extinguishing system. Automatic actuation of the system does not take place at this time, but it can be actuated manually via the fire-extinguishing system button at any time.

If the temperature threshold of approx. T = 160°C is exceeded at both temperature sensor circuits within t = 90 s, the fire extinguishing system is actuated automatically by the fire extinguishing system control unit and the emergency fresh-air system. The extinguishing agent tank opening mechanism is actuated.

Manual activation:

To actuate the fire-extinguishing system manually, first actuate the emergency fresh-air system/fire-extinguishing system activation button in the Guard operating unit. The LED in the fire-extinguishing system button starts to flash for approx. t = 6 s. The warning buzzer additionally issues a warning tone in the Guard operating unit. During this time, the fire-extinguishing system can be actuated by pressing and holding the fire-extinguishing system button (at least t = 1.5 s). The fire extinguishing system and emergency fresh-air system control unit directly reads in the status of the emergency fresh-air system/fire extinguishing system activation button and the fire extinguishing system button, actuates the LED in the fire extinguishing system button and the warning buzzer, and starts to extinguish by actuating the opening mechanism of the extinguishing agent tank.

To prevent smoke or extinguishing powder from entering into the vehicle interior, the "recirculated air" function is activated in the case of automatic actuation or when the emergency fresh-air system/fire-extinguishing system activation button is pressed, and ventilation is deactivated temporarily. The fire extinguishing system and emergency fresh-air system control unit transmits the associated request directly to the special vehicle multifunction control unit (MPM). The special vehicle multifunction control unit (MPM) passes on the request to the climate control unit via the CAN for the vehicle interior.

The air recirculation function can be stopped at any time by actuating the air-recirculation mode button at the air conditioning control panel.

	Function schematics
	Function schematic for fire-extinguishing system	Model 223 with code Z21 (Fire extinguishing system)	PE86.10-P-2500-97A
	Further basic functions
	Air-recirculation mode, basic function		GF83.40-P-1002A
	Component descriptions
	Fire extinguishing system and emergency fresh-air system control unit, component description	Model 223 with code Z21 (Fire extinguishing system)	GF86.10-P-2119A
	Fire extinguishing system temperature sensor, component description	Model 223 with code Z21 (Fire extinguishing system)	GF86.10-P-2126A