285: Signal exchange in fire alarm system

Signals in fire alarm systems can be categorized as:

1- Fault (trouble)

• Maintenance is required
• Panel shows the type of fault and location (text, yellow colour LEDs, etc.)

2- Alarm

• Identifying the reason of alarm and dealing with emergency or fire is required
• Panel shows the type of alarm and location (text, red colour LEDs, etc.))

3- Supervisory

• For alert and information
• Panel shows the type of supervisory and location (text, yellow colour LEDs, etc.)

There are different ways to send signals to other systems (third parties) or receive signals from them.

1- Exchanging analogue signals (In/Out): Range of values

• 4-20 mA
• 2-10 V
• 0-20 V
• Exchanging specific protocols (languages) such as Modbus through RS485

2- Exchanging digital signals and dry contacts (In/Out): high or low, open or close

• Output through the relays, NO (normally open) or NC (normally close):
  • Monitored output
  • Non-monitored output: If outputs or inputs are not monitored, the normally closed dry contact is preferred. Because by losing the signal at one side and displaying the open relay (NC to NO) status, diagnosis will be possible in another side.
• Output, voltage (24VDC): When allocating this type of output, the current required for activation must be taken into account. The output module must be able to supply the current required for activation.
  • Monitored output
  • Non-monitored output
• Input voltage (24VDC): usually for monitoring the dry contacts
  • Monitored output
  • Non-monitored output

We have different fire safety systems which each one has its own specific requirement for exchanging the signals. Also operators for different applications need different information.

Where is the destination of the signals?

• Fire brigades as an emergency call
• Central control rooms or monitoring area (PLC, SCADA, monitoring software)
• Related electrical systems such as HVAC
• Related control systems such as BMS, CCTV and Access control system

Outgoing signals:

• Sending general fault of the system (in case of any fault in the system)
  • Batteries: physical defect, low charge, problem in connections etc.
  • Peripheral equipment (Detectors, Call points, Alarm devices, Modules): physical defect, calibration problems, end of lines problem, configuration changes etc.
  • Panels: physical defect or software problem
  • Power supplies: Failure or power outage
  • Cables: Short circuit, open circuit, voltage drop, electromagnetic fields etc.
  • Earth fault: for cables or devices
• Sending general alarm of the system (in case of any alarm in the system)
  • Peripheral equipment (Detectors, Call points, Modules)
• Sending specific alarm or fault for specific zones or addresses as required
• Sending a signal for activation of the dampers or shutting down the HVAC
• Sending a signal to control the door (open the lock, opening the door, closing the door)

Incoming signals:

• Receiving the signals related to status of the ventilation system
• Receiving the status of the doors via limit switches. access control systems or intruder alarm systems

Outgoing signals:

• Sending the signal in case of the fault (General or Specific)
  • Gas sensors
  • Gas calibration
• Sending Alarm Level 1 of gas detectors (First stage of alarming)
• Sending Alarm Level 2 of gas detectors (Second stage of alarming)
• Sending signals during the isolation (inhibition) of a system
• Sending signals for tripping a machine or shut down a system

Incoming signals:

• Receiving signal to isolate alarms for special application
• Receiving signal to activate alarms (without gas detection) for special application

Signal exchange for different extinguishing systems (Water, Water mist, Foam, Halon, CO2, Inert gas, Chemical agent, Aerosol etc.) are slightly different. But in general, the signals sent and received are very similar.

Outgoing signals:

• Sending the signal in case of the fault (General or Specific)
  • Detection parts (Detectors, Call points, Modules)
  • Alarm parts (Alarm devices, Modules)
  • Extinguishing parts (Electrical and Mechanical)
• Sending fire alarm signal of the extinguishing system
  • Usually for detection in one zone which does not extinguishing the system
• Sending pre-discharge alarm signal of the extinguishing system
  • Usually for detection in two or more zones which release the extinguishing agent
• Sending the signal which confirms that agent is released or shows the flow of the agent in the pipes via flow switches. (extinguishing triggered)
• Sending the signal which shows the loss of agent in the cylinders when agent has leakage or has been discharged (via gauges, weighing devices, beam sensors, level meters etc.)
• Sending the signal while system is blocked (manually blocked or via signals and buttons)
• Sending signals during the isolation of the detection and alarm devices related to extinguishing system (signals)
• Sending signal for activation of the solenoid valves in other adjacent system with common detection lines and different extinguishing systems
  • Solenoid valve of water or foam system (deluge)
• Sending signal for activation of the dampers or shutting down the HVAC

Incoming signals:

• Receiving signal related to status of the ventilation system
• Receiving supervisory signals related to valves (open, close, incorrect status).
• Receiving supervisory signals related to doors (open, close).
• Receiving supervisory signals for activation of the valves in other adjacent system with common detection lines and different extinguishing systems
  • Valves of water or foam system (deluge)
  • Agent discharged