Cable Selection and Wiring Systems Flashcards
7 cards from real PART P practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Cable Selection and Wiring Systems flashcards as text
What does the abbreviation 'MICC' stand for in cable terminology?
Answer: Mineral Insulated Copper Clad
MICC stands for Mineral Insulated Copper Clad — these cables use compressed magnesium oxide as insulation and a seamless copper outer sheath, making them extremely fire resistant and suitable for emergency systems.
What is the maximum continuous conductor operating temperature for standard PVC insulated and sheathed cables (e.g., twin and earth)?
Answer: 70°C
Standard PVC insulated cables have a maximum continuous operating temperature of 70°C; exceeding this causes the PVC insulation to soften and degrade, reducing insulation resistance and creating a fire or shock hazard.
In which situation would XLPE (cross-linked polyethylene) insulated cable be preferred over standard PVC cable?
Answer: When higher operating temperatures or better chemical resistance is required
XLPE cables can operate continuously at 90°C conductor temperature and offer superior chemical and UV resistance compared to PVC, making them suitable for more demanding environments.
When steel conduit is used as a wiring enclosure in a domestic installation, how must it be connected to the earthing system?
Answer: It must be bonded to the main earthing terminal to ensure a fault return path
Metal conduit is an extraneous conductive part that could become live under fault conditions, so it must be bonded to the main earthing terminal to provide a fault current return path and allow the protective device to operate.
What is the primary function of PVC cable trunking in a domestic or light commercial electrical installation?
Answer: To provide a neat, organised, and protected route for multiple cables
Cable trunking provides a protected, organised enclosure for routing multiple cables, keeping them tidy, accessible for future maintenance, and shielded from mechanical damage.
When new brown/blue cables (post-2004 colours) are joined to an existing installation using old red/black cables, what action must be taken?
Answer: A warning notice indicating mixed cable colour codes must be fixed at the consumer unit
BS 7671 Regulation 514.14 requires a durable warning notice to be fixed at the consumer unit (and any joint boxes) stating that wiring of two colour codes is present, ensuring future electricians are not misled.
What key advantage does Steel Wire Armoured (SWA) cable offer over standard twin and earth cable when supplying an outdoor detached garage or outbuilding?
Answer: Its steel wire armour provides mechanical protection, allowing direct burial or exposed runs without additional conduit
SWA cable's steel wire armour gives it inherent mechanical protection against impact and crushing, allowing it to be buried directly or surface-mounted outdoors without the need for additional conduit.