Heating, Alarms

Question 1

What are the two types of hot water heating systems?

Answer 1

Stored hot water and instantaneous

Question 2

How does an immersion heater system work?

Answer 2

An element is constructed with a resistance wire that will get hot as current flows through is and this heats up the water.

A thermostat will disconnect the supply when the right temperature is met

Question 3

What is a typical setting for a thermostat in a heating system and why is this temperature used?

Answer 3

A typical setting for stored hot water is around 55-60 degrees. This is cold enough that it does not scold the user and hot enough that kills of legionella

Question 4

What does BS7671 require an immersion heater to have in terms of circuitry

Answer 4

BS7671 requires an immesion heater to have its own circuit and connected to a switch/fused connection installed adjacent to the cylinder. Connected by heat resistant flex

Question 5

Describe briefly how an instantaneous hot water system works?

Answer 5

An instantaneous how water system works by high power water heaters heat the water as it flows through the device. they do not store water internally

Question 6

What are the two different types of alarm configurations?

Answer 6

Open circuit and closed circuit

Question 7

Describe how an open circuit alarm operates

Answer 7

An open circuit alarm is incomplete or ‘open’ and detection devices close to initiate an alarm condition

Question 8

Describe an advantage and disadvantage of an open circuit alarm

Answer 8

Advantages are detectors are connected in parallel with the circuit, which makes it easy to connect or disconnect sensors

Disadvantages are if a circuit conductor is broken the alarm will not operate when required.

Question 9

What is an EOL in an open circuit alarm system?

Answer 9

An (EOL) resistor is an end of line resistor. located at the last call point of an alarm system. A monitoring voltage is applied to the circuit, resulting current will be low. When a detector closes the resistor will be shorted out and this will result in a greatly increased current which will initiate the alarm

Question 10

Describe briefly how a closed circuit alarm works

Answer 10

Is describe as a closed or ‘complete’ circuit. The detection devices open to break the circuit.

Question 11

Describe the advantages and disadvantages of a closed circuit

Answer 11

The advantages of a closed circuit are that it is considered ‘fail safe’. As if any connection is broken the alarm will operate.
Disadvantages are that the circuit must be interupted to insert additional sensors

Question 12

What are the two things fire alarm systems aim to protect?

Answer 12

Life and property

Question 13

What are the two types of call points used when a fire system is in place to protect life?

Answer 13

These are manual call points and automatic detectors.

Question 14

Name two types of alarm used used in a fire alarm designed to protect life?

Answer 14

Audible alarm and a remote alarm receiving centre which will contact emergency services

Question 15

What will a fire alarm protecting unmanned properties automatically do?

Answer 15

An unmanned property fire alarm will automatically contact the emergency services

Question 16

Give an example of different types of fire detectors?

Answer 16

Smoke detectors
Heat detectors
Flame detectors

Question 17

Typically is a fire alarm circuit open or closed?

Answer 17

A fire alarm circuit is typically wired in closed circuit configuration.

Question 18

How far must a firefighter have to search to find fire location

Answer 18

30 Metres

Question 19

What type of cables are used in fire alarm systems and how long will they withstand a fire?

Answer 19

FP200 and MIMCS cable ‘Mineral insulated copper clad’. These should withstand a fire for up to 120 minutes.

Question 20

List different types of intruder alarms

Answer 20

Break glass detectors
Door and window contacts
Passive infrared movement detectors
Ultrasonic movement detectors
Microwave movement detectors 
Beam break detectors

Question 21

How are intruder alarm circuits typically configured?

Answer 21

Intruder alarms are typically configured in closed circuit. They also use additional tamper circuits which have different polarities to make it difficult to short out.

Question 22

What are the two types of emergency lighting systems?

Answer 22

Maintained and non-maintained

Question 23

What is an emergency lighting system used for?

Answer 23

Used to supply occupants with sufficient lighting to get to emergency exit. Not to be confused with standby lighting which is used in normal activities

Question 24

What is maintained emergency lighting?

Answer 24

These are lighting luminaries which are illuminated at all times. Mains power will charge the battery and continue to run in the event of a power loss. Typically used for exit signs.

Question 25

What are non-maintained emergency lighting systems?

Answer 25

These are emergency lighting luminaries that are only used during a power failure. At other times lighting is off. These are usually tested regularly to ensure run time is sufficient. This is carried out by inserting ‘Fish tail’ keys to simulate power loss.