BS 7671: 2018 (2022) REQUIREMENTS FOR ELECTRICAL INSTALLATIONS Flashcards
Which regulation in BS 7671 defines the comprehensive list of installations to which it applies?
Section 514 Identification and Notices
What does a regulation ending in a “200 series number” indicate in BS 7671?
It is a regulation specific to the UK.
According to the provided information, what is the purpose of load shedding?
To reduce the impact of excessive loads during peak demand
What is the legal status of BS 7671: 2018 (2022) The IET Wiring Regulations, 18th Edition?
Non-statutory document
When was Amendment 2 of BS 7671: 2018 published, and when did it become the sole regulation?
Published in March 2022, became sole regulation in September 2022
What is the expected timeframe for the release of the 19th Edition of BS 7671?
Between 2025 and 2029
: Which chapter of BS 7671 sets out the scope of the regulations?
Chapter 11: Scope
What is the purpose of Chapter 36 in BS 7671?
To address the continuity of services, especially in emergency situations
In which chapter of BS 7671 can you find information about protection against electric shock?
Chapter 41: Protection Against Electric Shock
What is the main goal of fault protection in BS 7671?
To reduce the risk through contact with live parts during a fault
What is the purpose of the contents pages in BS 7671?
To list the topics covered in each part, chapter, or section
Which document specifies legal regulations that may be used as a tool for prosecution in a court of law if an electrical installation is not safe or suitable?
Electricity at Work Regulations (EWR)
What is the primary reason for the publication date of BS 7671 amendments being six months earlier than their implementation date?
TT
Why is additional source electrode connection necessary in PME (TN-C-S) systems?
To provide alternate paths for diverted neutral current
In a TN-S earthing system, what is typically used as the installation’s means of earthing?
Separate supplier’s earth
Which section of BS 7671 focuses on the assessment of maximum demand and diversity?
Section 311
What is the purpose of conducting an external earth fault loop impedance (Ze) measurement?
To calculate the prospective fault current (PFC)
According to BS 7671, why should every circuit be independent?
To ensure each circuit has its own line and neutral conductors
In Chapter 32 of BS 7671, what external factors are considered when deciding on the type of wiring system to install?
Environmental, such as temperature and moisture,
Utilization, such as the purpose of the installation,
Building materials, such as construction materials
What does Chapter 33 of BS 7671 primarily address?
Compatibility of electrical equipment
In Chapter 36 of BS 7671, what is the main consideration for circuits that require a continuous supply of electricity?
Using uninterrupted power supplies (UPS)
Which main risks associated with electricity are addressed in Part 4 of BS 7671?
Electric shock and overcurrent
What is the primary purpose of protection against electric shock in BS 7671?
To prevent electric shock hazards
In Part 4 of BS 7671, what does “fault protection” primarily aim to achieve?
Reducing the risk through contact with live parts during a fault
What is the primary purpose of basic protection in electrical installations?
To reduce the risk of electric shock
In BS 7671, what protective measure is the most commonly used for electrical installations to prevent electric shock?
Automatic disconnection of supply (ADS)
What is the purpose of protective earthing in electrical circuits?
To carry fault current and form part of the earth fault loop path
When should additional protection, such as an RCD, be provided in electrical circuits?
In circuits supplying socket outlets for Ordinary Persons
In a TN system, what is the purpose of the protective conductor (cpc)?
To carry fault current and connect exposed conductive parts to earth
Why are metallic enclosures required for consumer units in domestic installations?
To prevent the spread of fire in case of loose connections
In BS 7671, when should arc fault detection devices (AFDDs) be installed?
In certain residential premises with listed requirements
What are the two primary sources of overcurrent in electrical circuits?
Overload and fault current
Which protective device is commonly used to address overcurrent due to overload?
Circuit Breaker
In what situations should electrical equipment be spaced from stored or manufactured combustible material?
In locations with a fire risk due to stored or manufactured material
What is the primary purpose of arc fault detection devices (AFDDs) in electrical circuits?
To detect variations in the current sine wave
In BS 7671, what is the standard distance above which live parts are considered out of reach in controlled or supervised installations?
2.5 meters
What is the primary role of obstacles as a means of basic protection in electrical installations?
To prevent intentional contact with live parts
In electrical installations, what does the IPXXB rating for holes in enclosures mean?
Holes up to 12 mm in diameter are allowed
What is the primary purpose of placing electrical equipment out of reach in controlled or supervised installations?
To prevent accidental contact with live parts
In electrical installations, what is the primary purpose of a residual current device (RCD)?
To detect and disconnect in the event of a fault current to earth
What is the purpose of supplementary equipotential bonding in electrical installations?
To ensure equal voltages exist between equipment under fault and extraneous parts
In BS 7671, what type of equipment is permitted for double or reinforced insulation?
Class II equipment
What is the primary purpose of electrical separation in electrical circuits?
To create an independent circuit unaffected by earth
In electrical installations, what is the purpose of separated extra-low voltage (SELV) and protective extra-low voltage (PELV) systems?
To provide basic insulation
What does the value of earth fault loop impedance (Zs) indicate in an electrical installation?
The suitability of the circuit’s protective devices
In TT systems, what is the primary reason for using residual current devices (RCDs)?
To provide protection against electric shock
When is it necessary to use an RCD with a rated current not exceeding 30 mA in electrical installations?
In circuits supplying luminaires within domestic installations
What is the primary purpose of protective equipotential bonding in electrical installations?
To connect metal gas or water pipes to the earth
Which section of BS 7671 provides requirements for automatic disconnection of supply (ADS)?
Section 411
What is the purpose of the protective equipotential bonding conductor complying with Chapter 54 in electrical installations?
To connect extraneous conductive parts to the earth
In BS 7671, what are the required disconnection times for final circuits with a rated current not exceeding 63 A and a nominal voltage to earth of 230 V in a TT system?
0.4 seconds
When should additional protection by means of a residual current device (RCD) be provided in socket outlets?
In socket outlets with a rating up to 32 A with restricted use
In BS 7671, what is the purpose of Class II equipment?
To provide basic protection
What is the primary purpose of the IPXXD rating for accessible top surfaces of enclosures?
To prevent objects measuring 1 mm in diameter and 100 mm long from entering
Which of the following is NOT an overcurrent protective device?
Lighting rods
What is the purpose of a fuse in an electrical circuit?
To interrupt the circuit when current exceeds a certain level
What is NOT a characteristic of a rewirable fuse (BS 3036)?
High breaking capacity
What is the purpose of the breaking capacity (kA) rating for a fuse?
To specify the maximum fault current the fuse can safely disconnect
Which type of fuse is generally used for high prospective fault currents and comes in gG and gM categories?
BS 88 fuse
What is the primary function of miniature circuit breakers (MCBs)?
To provide protection against overloads
Which type of MCB is suitable for circuits with inrush currents, such as those with small to medium motors?
Type C MCB
What is the purpose of residual current devices (RCDs)?
To detect and disconnect circuits with ground faults
What is the main advantage of residual current breakers with overload (RCBOs)?
They combine overcurrent protection with ground fault protection
Why is it important to periodically press the test button on RCDs and RCBOs?
To keep the mechanical parts working effectively
Which devices melts and breaks the circuit when the current exceeds its rating?
Fuse
What is the purpose of the “Ia” rating for fuses and circuit breakers?
It’s the disconnection current rating
BS 88 fuses are generally incorporated into what type of bodies?
Sealed cylindrical ceramic bodies
What is the main advantage of BS 88 fuses like HRC (High-Rupturing Capacity) fuses?
They have high short-circuit breaking capacity
Miniature Circuit Breakers (MCBs) are commonly used for the protection of:
Final circuits
What type of MCB is typically used for circuits with small to medium motors or fluorescent luminaires?
Type C
What is the primary purpose of Residual Current Devices (RCDs)?
To protect against earth faults
What does RCBO stand for?
Residual Current Breaker with Overload
Which section of BS 7671 provides guidelines for calculating disconnection times for short circuits?
Section 461
What does the term “electromagnetic interference (EMI)” refer to in electrical installations?
Unwanted electromagnetic radiation causing device malfunction
Which section of BS 7671 deals with isolation and switching requirements for electrical installations?
Section 461
In a TN system, when must both live conductors be isolated using a double-pole switch in a household installation?
For all circuits
What is the main purpose of providing means of switching equipment off for mechanical maintenance?
To prevent injury to maintenance personnel
Emergency switching is typically provided in installations to:
Quickly remove unexpected dangers
Which device is commonly used for emergency switching in industrial settings?
Emergency Stop Button
Why is it important to standardize the colors used to identify conductors in electrical circuits?
It reduces the risk of dangerous situations
If equipment does not hold a British Standard, what must the designer do to ensure its safety level is similar to BS Standards?
Verify that the equipment is of a similar standard to BS Standards
What factors are considered when selecting equipment for an electrical installation under Section 512?
Operational conditions, voltage, current, frequency, power, and compatibility with other installed equipment.
Why is it important for cable joints and equipment to be accessible under Section 513?
To enable safe inspection, testing, and maintenance.
Which section of BS 7671 specifies the requirements for conductor identification by color, letters, or numbers?
Section 514.
What does Section 521 emphasize regarding line and neutral conductors?
They should be run together to reduce electromagnetic effects.
What does Regulation 522.6.201 address when cables are installed below a floor or in ceilings?
How deep the cables can be installed.
What is the most common practice when installing cables through joists, according to the IET On-Site Guide?
Drilling holes along the center of the joist
Which protection measures should be taken to protect cables installed within a wall at a depth of 50 mm or less from the surface?
Using prescribed zones of protection or providing additional mechanical protection
When cables are installed in metal stud walls, what additional protection must be provided according to Section 522.6?
RCD with a rating not exceeding 30 mA
In the context of electrical installations, what does SELV stand for?
Separated Extra-Low Voltage.
What is the primary purpose of Regulation 522.6.201 regarding cable installation below a floor or in ceilings?
To prevent damage to cables during installation
When is the use of steel conduit or trunking not practical in wall installations, according to Approved Document A?
When chasing deeper than one-third of the wall thickness is required
What is the purpose of prescribed zones of protection in electrical installations?
To protect cables from mechanical damage.
What additional protection is required for cables installed within a wall built with metal studs?
RCD with a rating not exceeding 30 mA
What external influences on wiring systems are covered in Section 522?
Ambient temperature, heat sources,
Water, humidity , impact, vibration, seismic effects and
Solar radiation and air movement only.
How can electromagnetic effects be reduced in wiring systems, as mentioned in Section 521?
By running line and neutral conductors together
What is the primary goal of Regulation 522.6.201 regarding cable installations below a floor or in ceilings?
To protect cables from mechanical damage
In wiring systems, what are SELV and PELV circuits typically used for?
Ensuring electrical safety.
What does Section 522.6 recommend when installing cables in metal stud walls?
RCD with a rating not exceeding 30 mA
What is the maximum depth for notches in a joist, according to the provided information?
0.07 × joist depth.
What is the primary concern when installing cables within a wall at a depth of 50 mm or less from the surface?
Protection from damage, including nails and screws.
Why are prescribed zones of protection commonly used when running cables within walls?
To protect cables from damage, even when they cannot be seen.
What is the purpose of using steel-wire armoured (SWA) or mineral-insulated (MI) cables in specific installations?
To provide a higher level of mechanical protection.
In an electrical installation, why is it crucial to consider the impact of external influences on wiring systems?
To prevent damage and ensure the system’s reliability and safety
What does Regulation subsection 522.8 primarily address in electrical installations?
Mechanical stress on cables
How does soft copper in electrical cables react to improper support?
It stretches, leading to reduced conductor size and potential overheating or breakage
According to Regulation 522.8.4, how should conductors or cables be supported when not continuously supported?
By using suitable means at appropriate intervals to prevent damage by their own weight.
What provides guidance on the ‘appropriate’ intervals for cable support in electrical installations?
IET OSG Table D1 (or Table 3.5 in your document)
In what situations does the weight of wiring within vertical trunking become a concern?
When the top bend is a right angle
What happens to PVC insulation in cables when exposed to high temperatures due to load current and bending pressure?
It softens and becomes prone to splitting, especially when subjected to pressure from bending.
What does Regulation 522.8.3 primarily concern regarding wiring systems?
Radius of bends to prevent conductor and termination damage.
When planning cable routes, what should be considered regarding bends and the number of bends in the wiring system?
Consider the number and tightness of bends to prevent undue stress and strain on cables.
Which section of BS 7671 provides guidance on conductor sizing and temperature limits under normal operating conditions?
Section 523.
What factors can affect the resistance of conductors in an electrical installation?
Ambient temperature, proximity to heat sources, and insulation material.
What does the adiabatic equation help determine in electrical installations?
The minimum size of a protective conductor (cpc) or earthing conductor under specific fault currents for specific durations.
What is the factor ‘k’ in the adiabatic equation based on?
How the cpc is installed (e.g., within a cable or separate).
In which chapter of BS 7671 would you find information about protection against electric shock and overcurrent protection?
Chapter 53.
What does ‘selectivity’ mean in the context of protective devices?
The coordination of devices to ensure local devices disconnect before main fuses or circuit breakers
Which chapter of BS 7671 addresses earthing arrangements and protective conductors?
Chapter 54.
When must metallic pipework, such as gas and water pipes, be bonded in electrical installations?
At the point of entry or within 600 mm of the meter or isolation point.
What does Section 543 of BS 7671 mainly address in electrical installations?
Equipment that may cause electromagnetic interference.
What are some types of equipment that may have high protective conductor currents?
EqEquipment with filtered power supplies, such as computers and photocopiers.uipment with filtered power supplies, such as computers and photocopiers.
Which section of BS 7671 covers the sizing and connection of bonding conductors for protective multiple earthing (PME) systems?
Section 544
In a TN-S installation, if a building is supplied using a cable with a 16 mm2 earthing conductor, what is the minimum size of the main protective bonding permitted for that building?
16 mm2
What is the primary concern when wiring is installed within vertical trunking?
Preventing the cable from being cut due to the trunking’s weigh
According to Regulation 522.8.4, what is the purpose of supporting conductors or cables at appropriate intervals?
To prevent the conductors or cables from suffering damage by their own weight.
What source of stress and strain can affect cables when they are bent too tightly?
Damage to the conductor insulation.*
According to Regulation 522.8.3, what should the radius of every bend in a wiring system be to avoid damage to conductors and terminations?
The radius should be such that conductors or cables do not suffer damage and terminations are not stressed.
Which section of BS 7671 outlines the maximum operating temperatures of conductors based on their insulating material?
Section 523
What factor affects the resistance of conductors in an electrical installation and must be considered during the design and installation stages?
Temperature, ambient conditions, and proximity to heat sources.
What does the adiabatic equation help determine in electrical installations?
The minimum conductor size needed to handle specific fault currents for specific durations
What is the factor ‘k’ in the adiabatic equation primarily based on?
How the cpc is installed (e.g., within a cable or separate).
Which chapter of BS 7671 primarily deals with the selection and installation of devices used for protection, isolation, switching, and control purposes?
Chapter 53.
What does ‘selectivity’ refer to in the context of protective devices?
The coordination of devices to ensure that local devices disconnect before main fuses or circuit breakers.
Which chapters are included in Part 6 of BS 7671?
Chapter 64 and Chapter 65
What does Chapter 64 of BS 7671 primarily cover?
Requirements for the inspection, testing, and certification of initial verifications
In which part of BS 7671 would you find requirements for electrical installations in special locations or environments?
Part 7
What is the main purpose of Part 7 in BS 7671?
It identifies and specifies requirements for special installations and locations with unique risks
According to Section 701 of BS 7671, where can you find baths or showers for general use?
Anywhere that a bath or shower is located for general use
What are the zones used to classify areas with different levels of risk in locations with baths or showers, according to BS 7671?
0, 1, 2, 3
In Zone 0 of a bath or shower location, what is the maximum height above the floor for the area of water containment?
2.25 meters
What are the minimum IP ratings required for equipment in Zone 1 of a bath or shower location, according to Table 3.9 of BS 7671?
IPX4
According to Regulation 701.411.3.3, what type of protection should all circuits within a location containing a bath or shower have?
RCD protection with a maximum rating of 30 mA
What is the primary purpose of supplementary equipotential bonding in locations with baths or showers?
To maintain the potential between exposed metalwork and extraneous conductive parts to 50 V AC or less
Which new chapter was introduced into BS 7671:2018 (2022) to address the requirements for electrical installations related to prosumers and alternative energy sources?
Chapter 82
What is the term ‘prosumer’ as defined in Chapter 82 of BS 7671:2018 (2022)?
Someone who consumes and produces electricity, either for their own use or to feed into the public network
What does ‘island mode’ refer to in the context of Chapter 82 of BS 7671?
An operating mode where an electrical installation is disconnected from the public supply network but remains energized by locally generated or stored electricity*
Which of the Appendices in BS 7671 provides definitions for multiple source, DC, and other system arrangements?
Appendix 11
In Section 701 of BS 7671, which of the following locations would NOT fall under its scope?
Changing rooms
According to Table 3.8 in BS 7671, what is the maximum height for Zone 2 in a location with a bath or shower?
0.6 meters
In Zone 2 of a bath or shower location, what is the maximum height for the area from the floor to which equipment can be installed?
2.25 meters
What is the primary consideration when selecting electrical equipment for locations with baths or showers, according to BS 7671?
IP ratings of equipment and accessories
What is the maximum resistance between the metal part of a location and the MET (Main Earthing Terminal) to omit supplementary equipotential bonding, as per BS 7671?
1667 ohms
In BS 7671, which section provides guidance on electrical installations in exhibitions, shows, and stands?
Section 740
