June 2023

Question 1

List three organisations which issue cards that may be used on a
construction site to prove a level of competency.

Answer 1

Electrotechnical Certification Scheme (or ECS)
Construction Skills Certification Scheme (or CSCS)
Joint Industry Board (or JIB)

Question 2

Explain the operating principle of a 30 mA single-phase RCD

Answer 2

A coil detects the balance (1) between line and neutral current (1) and will trip the RCD
if any imbalance exceeds 30 mA (1).

Question 3

List the three main components of a UPS system supplying AC to a
computer system.

Answer 3

AC to DC battery charger/rectifier
Battery
DC to AC Inverter

Question 4

List three ways that heat can be transferred from an electric fire to heat a
room.

Answer 4

Conduction
Convection
Radiation

Question 5

Explain how a shaver socket, used in a domestic bathroom, provides shock
protection when somebody comes into contact with a live part

Answer 5

An isolating (1) transformer is used to remove the neutral to earth reference (1) and
thus remove the risk of a shock to earth (1).

Question 6

List three exposed conductive parts likely to be present in an industrial
electrical installation.

Answer 6

Cable tray
Basket
Metallic conduit
Metallic trunking
Metallic enclosure of a distribution board

Question 7

Explain when a Type B circuit breaker should be used in preference to a
Type C or Type D.

Answer 7

Where there is no significant inrush (1) current into equipment (1) within the circuit
protected (1).

Question 8

State the minimum IP level to provide basic protection for
a) the side of a domestic consumer unit.
b) the accessible top horizontal surface of a distribution board.
c) steel trunking containing unsheathed low-voltage cables.

Answer 8

a) IP2X (or IPXXB) (1)
b) IP4X (or IPXXD) (1)
c) IP4X (or IPXXD) (1)

Question 9

Explain why live conductor polarity must be verified at each 230 V BS 1363
socket-outlet in a domestic installation.

Answer 9

If the polarity of line and neutral are swapped (1), the plug-top fuse (1) will be in the
neutral. (1)

Question 10

Explain why the entire domestic installation must be safely isolated when
carrying out an external earth fault loop impedance Ze test for the premises.

Answer 10

The earthing conductor (1) must be disconnected (1) to remove parallel paths (1) from
the reading.

Question 11

List three materials which would require disposal as hazardous materials, if
present within equipment replaced during electrical fault rectification.

Answer 11

Asbestos.
Phosphorous.
Mercury.
Acid (or alkali)

Question 12

State what needs to be confirmed for supplementary bonding to be omitted
in a location containing a bath.

Answer 12

All circuits comply with ADS (or 411.3.2). (1)
All circuits have RCD protection. (1)
All extraneous-conductive-parts of the location are effectively connected to protective
bonding. (or comply with 411.3.1.2). (1)

Question 13

Explain why arc fault detection devices (AFDDs) are required to be installed
at the origin of socket-outlet circuits within Houses in Multiple Occupation
(HMOs).

Answer 13

AFDDs detect arc faults (1) which could be series (1) or parallel (1) faults and reduce
the risk of fire (1) in buildings having multiple people/difficult evacuation (1).

Question 14

State two sources for safety services as given in BS 7671.

Answer 14

Storage batteries
* Primary cells
* Generators
* Separate feeder

Question 15

Explain why continuity of conductors must be tested prior to insulation
resistance during the initial verification of a new circuit.

Answer 15

If the circuit isn’t continuous (1) then an insulation fault after a break may not be
detected (1).