Fire Alarms Flashcards
Basic components of a FA system
Initiating devices
Alarm/Signalling devices
Control Panel (FACU)
What is the purpose of initiating devices and some examples?
Detect the presence of a fire manually or automatically
- Smoke detectors
- Heat Detectors
- Pull Stations
- Flame detectors
What are 3 types of signalling devices?
Bells
Horns
Strobes
What is the control panel (FACU) ?
Contains power supply and circuitry for operating, monitoring and troubleshooting
Annunicator Panel
- A device used to visually display signals received from a FA system.
- Usually located at main entrances
- Typically graphical
What is an ancillary device?
A device from another protection system that is actuated by the FA system.
Examples of ancillary devices?
Fan shutdowns Fan start up Fire door magnets Door lock releases Elevator homing Plenum dampers Fire phones City tie module (CTM)
What are the 3 communication systems?
Simplex
Half duplex
Full duplex
Simplex system
One way only
Half duplex system
both ways but only one way at a time (share channel)
Full duplex system
Both ways at the same time (2 channels)
Single stage FA system
- Any initiating device will cause signalling devices to be activated.
- Schools, apartments, warehouses, and industrial plants
Two stage FA system
- Any initiating device will first activate an alert signal and if not responded to within 5 min. an alarm signal will sound
- Hospitals, manors, airports, hotels, department stores.
The alert signal for a 2 stage system is meant for?
- Designated persons who may activate the GA at any time
- Allows supervisory staff to investigate and react as needed
- Requires trained personnel 24/7
The first alert on 2 stage system is commonly ____ bell strokes/min and the full alarm is ____ bell strokes/min.
20
120
What is a Zone in a building FA system?
A defined location that is covered by initiating devices on one circuit (non-addressable circuit)
A zone with a defined area with assigned initiating devices is?
Addressable
What typically determines the number of zones needed?
Size of the building
Occupancy type of the building
A building with an area of _____ square meters or less than ___ stories may be on a single zone.
2000
3
Hospitals must have ____ of zones
100s
Nursing homes must have how many zones?
2 zones per floor
What does AHJ stand for ?
Authority
Having
Jurisdiction
Pull station specs
- Use a N.O. single pole switch operated by pull handle
- Glass or brittle plastic rod used to indicate which station was pulled
- Psychological deterent
- Bright red and must be visible from front and sides
Pull stations are mounted?
1.05m to 1.15m AFF to centre
Within 1 arm length
Where are pull stations installed?
On all floors including basements, corridors, large assembly rooms > 60 people, lobbies, exits to stairwells and building exits.
A 2 stage pull station has a _________ along with standard handle.
Key operated switch
Pull handle initiates the alert and key switch initiates the alarm.
What are the 4 types of heat detectors?
- Fixed temp
- Rate of rise
- Combo fixed and rate of rise
- Line type (LTHD)
Fixed temp heat detector types and temperatures
- Restorable or non restorable
- Common fixed temps are 58 °C/135 °F
90 °C/194 °F
Restorable type heat detector specs
- Bimetallic strip causes contact closure when it bends due to temp rise
- When temp falls contacts open
- Can be tested using approved heat device
Non restorable heat detector specs
- 1/3 the price of restorable
- Heat causes solder pot to melt allowing spring loaded set of contacts to close
- Temp decreases no means to reset
- Centre red disk drops down to indicate tripped
Rate of rise heat detector specs
- Designed to operate anytime the temp of ambient air rises more than 9 °C (or 6°C) 14 °F per minute regardless of actual temp.
- Faster response then fixed temp det.
- Not suitable for areas where rapid changes in temp are normal. ie. kitchens, boiler rooms, xfmr vaults etc.
Line type heat detector specs and how is it activated?
- Not a ‘spot type” device
- Heat sensitive polymer melts and short 2 conductors or a thermistor core conducts.
- Good for long areas ie. cable trays
- Suppression usually accompanies alarm
Heat detectors should only be used where?
Property detection alone is required
Heat detectors are not a ?
Life safety device
What provides the earliest warning of a fire condition?
Smoke detectors
3 main types of smokies?
- Photoelectric
- Ionization
- Beam
Photoelectric smokie specs
- Uses a light source and light detector
- Requires visible smoke to operate
- Smoke entering the chamber affects the beam of light causing N.O. contact to close
- Test with a can of smoke
- Install in bedrooms, hallways
2 types of photoelectric smokies
Light scattering
Light obscuration - BEST - Fail Safe
Ionization smokie AKA?
Product of combustion type
Ionization smokie specs
- Detects first stage of fire (incipient)
- Very sensitive
- Have small amount of radio active material btwn 2 plates
- Under normal operation a very small ionization current flows and if particles of visible or invisible smoke enter the chamber current flow is interrupted causing a N.O. contact to close
Beam type smokie specs
- Used for very long and/or tall rooms (stratification)
- Transmit light across the room to detect smoke
Reflective type beam smokie specs
- Has wiring at only one end
- Not good for narrow spaces < 1m away from trusses etc.
End to end type beam smokie specs
- Needs wiring at both ends to the transmitter and receiver
- Better for narrow spaces
UV/IR detectors specs
- Flame detector (stage 3)
- Usually accompany suppression
- Best for detecting flammable liquid fires
- UV detects natural gas, butane, propane (blue)
- IV detects gasoline, jet fuel, diesel (red)
List 6 signalling devices
- Vibrating bells
- Single stroke bells
- Chimes
- Horns and sirens
- Visual devices
- Loud speakers
Most common size vibrating bell?
10”
Where are single stroke bells typically used?
- Used in 2 stage systems
- Can provide individual notes for coded signals
Chimes have a _____ intensity and are generally used for alert systems in ________ areas.
Low intensity and generally used for alert systems in quiet areas (hospitals, manors etc.)
Where are horns/sirens used?
In areas of high noise or where bells are used for other purposes
Where are visual devices used?
In areas with high noise or where occupants have hearing impairments
(not used as replacement or audible devices)
Loud speakers specs
- Can be used instead of bells
- May provide evacuation instructions
- If used for other purposes, FA must have precedence
Maximum height for annunciator panel?
2.4m
F.A.C.U specs
- Contains relay/solid state circuitry to operate signalling devices when initiating devices are activated
- Has power, trouble and alarm LEDs or text screens
- Contains power supply and stand by 24VDC battery and charger
- Pushbuttons for testing and silencing
Max height for a FACU?
8’ or 2.4m to the top
How does electrical supervision work?
- FA control unit always monitors initiating and signalling zones for faults (opens/grounds)
- Uses low level current (40mA) through closed loop
- If loop opens or has a ground fault, panel will signal a trouble condition
The standby power for a FA system must provide supervisory current for ____ then a further ____ of continuous alarm.
24 hours
5 min
Class A wiring
- Wiring starts and ends at the panel
- Requires about twice as much wire as Class B
- Will still function if an open occurs in a conductor
IDC stands for?
Initiating device circuit
Class B wiring
- Wiring starts at panel and ends at end of line resistor (EOL)
- EOL mounted in a separate box beyond last initiating/signalling device
- EOL values differ btwn I/S zones and btwn manufacturers
Even though FA circuits operate at low voltage they are deemed as ?
Class 1 circuits (see 16-010 CEC)
Signalling circuit specs
- 24VDC
- Each device incorporates a diode which blocks supervisory current when not in alarm
- If panel goes into alarm, zone polarity is reversed on signalling circuits by the panel, putting the devices into action.
SDC and NAC
Signalling Device Circuits (Canada)
Notification Appliance Circuit (NAC)
Flashover is the transition between
Stage 2 (smouldering) and Stage 3 (Flame)
Four stages of a fire
- Incipient
- Smouldering
- Flame
- Heat
Four classes of fire
- Class A - wood, paper and rags
- Class B - vapour, air, gas and paint
- Class C - electrical
- Class D - combustible metals
Successful combustion requires what 4 components?
Heat
Oxygen
Fuel
Chain Reaction
The primary purpose of a FA system is?
Protect lives
The secondary purpose of a FA system
Protect property and to initiate fire fighting in event of fire
3 systems that protect occupants of buildings and the structure itself from fire
- Passive
- Detection/Signalling
- Suppression
What does PASS stand for?
P - Pull pin
A - Aim
S - Squeeze
S - Sweep
What is a Class K fire?
Fires in cooking appliances that involve combustible cooking media
Minimum height of a fire bell?
1.8m to centre
Maximum height permitted for an EOL?
1.8m to top
Addressable system specs
- CPU/microprocessor controlled
- Field devices supervised digitally
- Can be pig tailed due to polling
- CPU polls each device for “state of health”
- Devices report back, OK, trouble or alarm
- No response, FACU goes into trouble
How are the devices addressed in addressable systems?
- Set with dip switches or rotary dial switches
- Assigned with a laptop via control panel
- May be assigned automatically by FACU
- Could be assigned one by one w/ portable handheld programmer
Purpose of fire alarm isolators?
Removes sections of zones in the event of a failure so the remaining devices can still function
4 types of sprinkler systems
- Wet-pipe system
- Dry-pipe system
- Pre-Action system
- Deluge System
Wet-pipe system specs
- Fastest response time
- Used on ordinary combustibles where freezing is not a concern
- Schools, hospitals, offices
For a flow and tamper circuit, if the N.O. flow switch closes it sets off an _____ and if the N.O.H.C tamper switch opens it sets off a ______.
Alarm
Trouble
Purpose of a jockey pump
- Boost the water pressure on the sprinkler side of the check valve
- Reduces false alarms caused by “water hammering”
- Typically have their own controls and are supervised by FACU
Dry-pipe system specs
- Used on ordinary combustibles where freezing is a concern
- Parkades, warehouses, unheated structures
- Pipes contain air or nitrogen instead of water
- Dry side has 3-5 ties the surface area of the wet side
Pre-action system specs
- Essentially a dry pipe system where the water is held back by an electronically controlled valve connected to the FACU
- Only after the fire detection system is activated will water enter the system pipes and each sprinkler head is individually activated
- Good for applications where accidental discharge of sprinklers would cause extensive damage like data centre and libraries
- Double interlocked: broken sprinkler head and IDC activation
Deluge system specs
- Designed for high hazard zones
- Pipes are dry and unpressurized, sprinkler heads are open, connected to a water source directly and water is held back by a valve
- When the system detects a fire, water is pumped through the systems pipes and is discharged through all the open heads flooding the affected area
- Majority of systems use foam-based agents
Type 1 FA system
Non indicating
Non-zoned
GA
Type 2 FA System
Indicating
Zoned
GA
Type 3 FA system
Indicating
Zoned
Coded
GA
Type 4 FA system
Indicating
Zoned
Alert/Alarm
Type 4 FA system
Indicating
Zoned
Coded
Alert/Alarm
Where are EOL usually located?
After last initiating or signalling device
After install of FA system, explain how to test supervised circuits.
Open each device cct - Trouble
Trip each device cct - Alarm
Verify each signal device
what are the three basic components of any FA system?
Initiating devices
Signalling devices
FACU
Define electrical supervison
The ability to detect a fault condition that would interfere with the normal operation of the circuit
What is the main difference between a single and multi zone FA system?
Single zone does not identify the location of the trouble
Multi zone does identify the location of the trouble
Besides fundamental function of detection and alarm, list 2 additional functions that a FA system may be capable of performing?
Actuating ancillary devices
Alert the fire department
What 2 possibilities may exist in an initiating circuit when an ohmmeter placed across the leads reads a short?
Device is tripped
Conductors shorted
Not wired properly
What type of battery is used as a standby power supply?
Rechargeable
What is the purpose of an EOL in a supervised FA system?
To permit supervisory current to flow
What is the essential difference between a Class A and Class B wiring system?
Class A - 4 wires from/to the panel, no EOL
Class B - 2 wires from panel, has EOL
State one advantage and one disadvantage of a Class A wiring system?
More reliable
More costly
