183: Fire Detection and Alarm System Basics

Topics related to fire alarm systems and component can be reviewed in the following categories:

• Initiating Devices (detectors, manual call points, input modules, etc.)
• Notification Appliances (sounder flashers, output modules)
• Control Panels (fire panels, fire and extinguishing panels, F&G panels)
• Power Supplies (main power supply, batteries or UPS)
• Codes & Standards (electrical, safety, etc.)

Initiating Manually:

Manual fire alarm stations (Pull Boxes)

• Manual Stations/Fire Alarm Boxes/Pull Stations
  • Very good smoke and fire detector!
  • Red color
  • Must be reset manually after operation
• Types:
  • Single action (Direct)
  • Double action (Indirect): Reduce malicious false alarm, Lifting the cover and pulling the handle or break the glass and push the button

Initiating Automatically:

1- Smoke Detectors: Detect and respond to the smoke from a fire

1-1- Spot type Detector

1-2- Duct Detector

• For Heating ventilation, air conditioning system or HVAC
• To prevent uncontrolled spread of the smoke in the area
• Monitor air
• Control system fans
• Not a substitute for area detectors

1-3- Linear Beam Detector

• Use to cover large spaces

1-4- Air Sampling Detector

2- Heat Detectors: Detect and respond to the heat from a fire

2-1 Spot type Detector

• Fixed Temperature
• Rate of Rise (More than 15 degrees per Min.)
• Rate of compensation
  • Tubular shell and two expansion struts
  • Under compression and fitted with an open contact
  • Shell an struts have different coefficient of expansion
  • Shell expands and lengthens slively
  • Struts lengthen at slower rate than the shell
  • Device initiates an alarm faster than fixed temperature device
• Heat Detector structure for resetting:
  • Non restorable

• Designed with a fusible element that melts rapidly at a predetermined temperature
• Detection element must be replaced after operation

• • Restorable

• Automatically resets itself
• Contains a chamber with flexible diaphragm and calibrated vent
• Air in Chamber expands faster than it can escape
• Expanding air moves diaphragm so contact closes and alarm initiates

2-2- Linear Heat Detector

• Installed in loops around the protected premises
• Responds like a spot type heat detectors
• Types:

• Fixed Temperature
• Rate of Rise
  • Uses metal tubing
  • Tubing installed in loops
  • Air within tubing expand and move diaphragm and close the contact

2-3- Fiber Optic Sensor Cable

• In harsh environment
• Sensor Cable is designed for useful life of 30 years!

3- Flame detector or Radiant energy detector

• Ultra Violet (UV)
• Infrared (IR)
• Responds to radiant energy
• Use to sense smokeless combustible liquid and gas fire which can expand rapidly

4- Gas Detector

5- Interfaces

The main signals in the building through interfaces are related to Sprinkler system.

Sprinkler is a heat activated fire detector and extinguishing device which after activation and water flow, below signals related to pipe and valve must be monitored.

• Water flow switches
• Valve tamper switches
• Supervisory devices

Sprinkler system types:

• Wet Pipe
• Dry Pipe
• Deluge
• Pre action

Sprinkler system signals:

5-1- Water flow switches

• Vane Type

Vane or Paddle inserted in the sprinkler system pipe

Vane operate the switch initiating alarm when water flow

• Pressure Type

5-2- Valve Tamper Switch

Indicates when valve is not fully open

5-2-1- Tank Water Level Switch

5-2-2- Tank Temperature Switch

• Storage tank in climate that experience very low temperature
• Prevents from freezing

5-2-3- Tank Pressure Switch

• For high (excess) and low pressure
• Either supervisory

5-2-4- Water Pressure Switch

• Monitors pressure of water entering the building from the city water utility
• Supervises supply pressure
• Are installed at the alarm valve
• High and low pressure are monitored

5-2-5- Air Pressure Switch

• Dry pipe and pre action systems do not have water in piping
• Some systems charged with inert gas
• High and low air pressure are monitored

5-2-6- Room Temperature Switch

• Monitors room temperature to prevent freezing
• Frozen water damages the pipes

5-2-7- Fire Pump Supervision

• Provide sufficient pressure to deliver water
• Supervised conditions:
• Pump running
• Power failure and phase reversal
• Fuel level or source
• Failure to start

1. A) Audible Appliances:

• Horn
• Bell
• Buzzer
• chime

1. B) Visual Appliances:

• Strobe
• Sign

1. C) Combination Appliances (Audible-Visual)

Audible Notification:

• Creat a distinictive sound
• Operate in continuous and temporal modes
• Bell (striking a gong with a hammer)
• Most modern horns are electronic
• Chimes use in places like hospital in which a state of panic by building occupant might be concern.
• Temporal Signal (March time)

Additional Audible Application:

• Used for severe weather condition
• Uses a different signal pattern (for example to notify the building occupants to move to designated safe area of the building)

Visual Notification:

• Supplement audible devices
• Alert hearing impaired individual

Textural appliances Notification:

May be signs or other means of displaying a message to meet the needs of occupant and operator of facilities

Connecting to circuit depends on:

• Appliance
• Current
• Voltage requirement

Buildings control systems:

• Elevator control
• Fan control
• Stair pressurization
• Door control

• Elevator control
  • Control building elevator during emergency
  • Recall elevator to safe location

Sprinklers in elevator machine rooms or shafts:

• System stops power to elevator (by shunt trip function)

Protects equipment and indivisual:

• Prevents the equipment for being damage
• Prevents indivisual from being electrocuted

System may provide advanced warning:

• Fan control
• Stair pressurization
• Door control
• Supervisory

Damper Position Switch:

• Fire and smoke dampers located in HVAC systems
• Normally open
• Close during a fire to limit the spread of fire and smoke through HVAC systems
• Air Flow Indicator
• Verifies fan operation
• System needs to know if air is flowing or not flowing

Industrial process supervision:

• Provided for non-fire protection equipment including:
• Heating systems
• Pumps
• Ventilation systems
• Exhaus systems
• Off normal condition = Supervisory event

Fire alarm general specifications:

• System Center
• Connect Initiating Devices to Notification Appliances together to form a system.
• Supply power to Initiating Devices and Notification Appliances
• Monitor Initiating Devices and Notification Appliances for alarm condition (Supervision)

Fire alarm panel types and addressing methods:

• Conventional

• • Identifies fire location by zones. Zone refer to device types and areas of the building.

• Intelligent (Addressable System)

• • Introduced by Siemens in 1982.
  • Identifies specific initiating devices.
  • Mix different devices on a single circuit.

How panel monitors the field devices?

• Conventional System:

By passing the small current through circuit and monitoring the current received at the control panel.

• Addressable System:

By pulling the addresses of each the device programmed in the system to assure that devices properly

How is the operation of the fire panel?

• Via Person Machine Interface (PMI)

How Information displayed in the fire panel?

• LED Indicator
• Text in LCD (liquid crystal display)
• Graphics

Event Types in fire alarm panels:

• Alarm: fire condition
• Supervisory: off-normal condition
• Trouble (fault): part of system not properly working

Fire alarm circuit types:

• IDC: Initiation Device Circuit
  • Support Limited amount of devices
  • Smoke detectors need current
  • Thermal detectors and manual stations do not!
• NAC: Notification Appliance
• SLC: Signalling Line Circuit

Fire alarm circuit classes:

• Class B
• Class A

Power supplies are divided to two main categories:

1- Primary: From power provider company (main supply)

2- Secondary: When power failure occurs: Battery back-up or UPS (Uninterruptible power supply)

Devices required to operate on secondary power

In power Failure under the worst case (Design):

• all devices must operate for 24 Hour continuously
• Secondary power for about 15 minutes

General points:

• Systems are required to meet design and local codes.
• Codes increase system effectiveness and reliability.
• Codes save lives.
• The private sector creates and drives the codes.
• Voluntary system produces a balanced standard.

About NFPA (National Fire Protection Association):

• Was stablished in 1896.
• Fire prevention advocate.
• Authoritative source on public safety.
• Standards reflect cross section of interests.
• Based on input from:
  • Regulatory officials
  • Manufacturers
  • End users

About NFPA 72:

• Provide requirement for alarm system:

• • Installation
  • Performance
  • Testing
  • Inspection
  • Maintenance

• NFPA system classification:
• Sounds an alarm
• Manual or automatic operation
• Auto operation: Sprinkler system, Carbon dioxide discharge, Smoke detection, heat detection
• Auxiliary Fire Alarm Systems.
• Central Station Fire Alarm System.
• Combination Systems.
• Household Fire Alarm System.
• Municipal Fire Alarm System.
• Proprietary Supervising Station Fire Alarm System.
• Protected Premises (Local) Fire Alarm System.
• Public Fire Alarm Reporting System.
• Remote Supervising Station Fire Alarm System.

About UL (Underwriters Laboratories):

• Equipment must pass rigorous testing procedure
• UL develops standards and test procedures
• Fire detection and alarm equipment must be listed

About FM Approvals (Part of FM Global):

• FM Approvals tests systems
• Provide certification

About VdS (Vertrauen durch Sicherheit):

• VdS inspects and certifies products
• Inspection on Site
• VdS laboratories conduct tests for products used for fire and intrusion prevention.
• All tests are based on VdS rules.
• Fire: Smoke detectors, Sprinkler systems, Gas extinguishing systems, etc.
• Intrusion: Lock systems, Intruder alarm systems, Safes and strong rooms, Locks for bikes and motorbikes, etc.
• VdS supports manufacturers in obtaining the CE-marking and the declarations of conformity.

Other related abbreviations:

• ICC (International Code Council)
• AHJ (Authority having jurisdiction)

Each municipality in USA sets:

• System requirements
• Identifies codes to enforce
• Identifies an official to enforce the code
• Responsible official called AHJ:
• Qualified inspector
• Building official
• Fire marshal
• Check for compliance

Based on Siemens Online training courses