T2 Flashcards
In Relation to intruder alarm systems explain the function and operation of the Tamper Circuirt
The function of the tamper circuit is to generate an alarm condition when deliberate interference with the systems components is detected,
In a four wire zone circuirt when the front cover of one of the connected field sensors/contacts is removed an anti tamper device is triggerd by the opening of a dedicated tamper proof contact this change of state raises the alarm whether the alarm is set or unset
Design a intruder alarm system to provide security protection for a 3 bedroom house
Magnetic reed switch-Front door,kitchen door, garage door.
Remote keypad- inside front door and garage door.
Inertia sensor- ground floor and upstairs windows.
Passive infrared sensor- garage and 1st floor landing.
External bell- front of the house 1st floor.
Main control panel- garage
The maximum distance in metres between manual call points
60 meters
The maximum mounting height of manual call points above the finished floor level
1.2 meters
Four locations where manual call points within a building are mandatory
-at every final exit
-Accommodation stairways
-refuge areas
-staircase landings
-defined escape routes
Category L fire alarm systems are divided into 4 systems
L1- automatic detection in every space
L2- automatic detection in escape routes and adjoining rooms with special area added.
L3- automatic detection In escape routes and adjoining rooms.
L4- automatic detection in escape routes only
Maximum demand for electrical tariffs for industrial consumers:
1: the period of minutes in which the meter records the consumers highest level of electricity during the day.
2: the consequence for the consumer of their agreed maximum import capacity (MIC) is too low
1: 15 minutes
2:if the consumers MIC is too low, they may incur a excess capacity charge
State the type of earthing system which utilities a PEN conductor and identify the section of the earthing system where the conductor is employed.
TNCS earthing system
TNCS earthing system employs a pen conductor between the source of the supply and the consumers intake
Specify four types of alarm sensors typically found connected to a domestic intruder alarm system
panic attack button- exit/entry or bedroom
Magnetic reed switch contact- front or/and back door
Passive infra red sensor- hallway or upstairs landing
Inertia sensors- windows
Disadvantage of a closed detection loop circuit
An alarm contact sensor or terminal contacts could be potentially shorted out by a prospective intruder without any indication been given this would permit the opening of any of sensor contacts without raising the alarm
How to overcome a closed loop detection circuit
Connecting a EOL ( End of line) resistor across the supply after the last sensor provides monitoring for the both short and open circuit conditions and removes the danger
Distinguish between the two types of heat detectors normally connected to a fire alarm system
Fixed temperature- these are designed to operate when they reach a pre selected threshold temperature.
Rate of rise Temperature- these are designed to operate when the sensed temperature rises abnormally quickly
Suitable location/application for the installation for an ionisation smoke detector
Ionisation smoke detectors are suitable for use in areas containing flammable materials such as cloakrooms or janitor rooms, use these detectors where rapid open flame fires are likely
List 3 considerations which influence the choice of a fire alarm detector for a particular application
Cost of detector
The nature of the fire hazard
The speed of response required
Ease of maintenance
The minimum number of sounder/bell circuits that are required to be connected to a buildings fire alarm control panel
Two sounder circuits
Suitable Plc output type to switch each of the following
An Indicator lamp
DC relay
Thyristor
Transistor
Explain the purpose of a opto coupler and operation of the circuit
Device that allows the transmission of signal between parts of two circuits whilst providing electrical isolation between two circuits
When a current runs through the led it emits lights the photo transistor detects light and allows current to flow through resistor
Advantage and disadvantage of a Relay
Advantage- simple and can switch Ac to Dc
Disadvantage- they suffer from contact bounce and short mechanical life
Advantage and disadvantage of a transistor
Advantage- Cheap and no moving parts and silent
Disadvantage- Can only switch DC and False triggering
Snubber circuit
Helps prevent false triggering
Liminates RFI
Radio frequency interference
Protection against contact with live parts
Double installation
Non conducting location
Earth free local equipment bonding
Electrical separation
Touch voltage
In the event that a earth fault occurs the voltage that a person or animal is exposed at he point of the fault
How to protect electric shock in normal services
Protection by insulation of live parts
Protection by barriers
Protection by obstacles
RCD protection
Protection against electric shock in the event of a fault
Protection by non conducting location
Protection by earth free local equipment bonding
Reasons for bonding
To limit touch voltage
To prevent fire hazard
To prevent electrical shock in humans and livestock
To ensure all metalwork in the installation is at the same potential
Four benefits of installing smart meters
Reduce time wasting in meter readings
Have instant access to information on energy use
Lower carbon footprint
Take control on how much you spend
3 main types of protection
Perimeter protection- where the detectors are located to protect the perimeter
Space or shell protection: where detectors are located to protect open areas within the premises
Trap protection: where detectors are deliberately located to trap intruders
Use white light for false alarms
Open loop detection disadvantages
Vulnerable to tampering
Inconvenient for testing
Closed loop detection circuit advantages and disadvantages
Advantages- if someone cuts wire it will set off alarm
Disadvantages - contacts can be shorted out
Effects of lighting strike
Thermal effects
Mechanical effects
Electrical effects
Main components of a lightning protection system
Air termination
Down conductors
Earth electrodes
Bonding( to prevent side flashing)
How do you prevent side flashing
Bonding all metalwork on or around a structure is bonded to the lightning protection system
Draw building diagram with earth bonding on each bottom corner of the house
3 type of fire alarms
Ion
Smoke
Heat
Benefits of MCBS or fuses
Tamperproof
Locking devices can be attached
Do not normally require replacement
Enables supply to be restored immediately
