Electrical Wiring and Cable Management Flashcards
6 cards from real ECS practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Electrical Wiring and Cable Management flashcards as text
What is the maximum number of conductors permitted in a conduit, and what principle governs this limit?
Answer: Limited by the cable fill ratio to allow heat dissipation and ease of cable installation
Conduit fill is limited by a fill ratio (typically 40% of conduit cross-section) to allow for heat dissipation and to make cable pulling and future modifications practical.
When using mineral-insulated (MICC) cable, what is the critical step required at each termination?
Answer: Sealing the termination to prevent moisture ingress into the mineral insulation
MICC cable uses hygroscopic mineral insulation that absorbs moisture, so each termination must be sealed with a purpose-made pot seal to maintain insulation integrity.
What is the correct procedure when cables must cross other services such as gas or water pipes?
Answer: Maintain minimum separation distances and ensure cables are protected where they cross
Electrical cables crossing other services must maintain minimum separation distances and be protected against mechanical damage at crossing points to prevent cross-service damage.
What does 'volt drop' mean in cable sizing, and why does it matter?
Answer: The reduction in voltage along a cable due to its resistance, which must stay within permitted limits
Volt drop is the voltage loss along a cable caused by conductor resistance; it must be limited (typically 3–5% for final circuits) to ensure equipment operates correctly.
Which cable installation method requires the installer to check for 'short-circuit withstand' in addition to current-carrying capacity?
Answer: Cables protected by fuses or circuit breakers where fault currents could be very high
Short-circuit withstand capacity ensures the cable can survive the thermal and magnetic stress of a fault current long enough for the protective device to operate.
What is the purpose of a draw wire (pull wire) left in conduit after installation?
Answer: To allow future cables to be pulled through the conduit without dismantling it
A draw wire left in conduit allows electricians to pull additional cables through in the future without needing to dismantle the installed conduit system.