A residential building has the following 10 lighting points (ii) 8 socket walls (iii) 1 electric cooker (iv) I water heater : As a technician, recommend a suitable cable sizes for each circuit, and justify your choice based on Load Standard building installation prices (C) safety

Here are the recommended cable sizes for each circuit, with justifications:

1. 10 lighting points

   • Recommended Cable Size: 1.5 mm² copper cable
   • Justification:
     • a) Load: Assuming 100W per lighting point, the total load is 1000W. At 230V, this draws approximately 4.35A. A 1.5 mm² cable can safely carry 16A-18A, which is well above this load.
     • b) Standard building installation practices: 1.5 mm² is the universally accepted minimum standard for residential lighting circuits, offering a cost-effective solution with adequate capacity.
     • c) Safety: This cable size is typically protected by a 6A or 10A Miniature Circuit Breaker (MCB), ensuring protection against overcurrent and thermal overload.

2. 8 socket walls

   • Recommended Cable Size: 2.5 mm² copper cable
   • Justification:
     • a) Load: General purpose socket circuits can experience varying loads from multiple appliances. A 2.5 mm² cable can safely carry 20A-27A, which is sufficient for typical domestic use, even with diversity.
     • b) Standard building installation practices: 2.5 mm² is the standard minimum size for general purpose socket circuits (radial or ring final) in residential installations, balancing capacity and cost.
     • c) Safety: This cable is typically protected by a 20A or 32A MCB, providing robust overcurrent protection and preventing overheating under normal and fault conditions.

3. 1 electric cooker

   • Recommended Cable Size: 6 mm² copper cable (for cookers up to approximately 8kW)
   • Justification:
     • a) Load: Assuming a typical electric cooker load of 8000W, the current drawn is approximately 34.78A at 230V. A 6 mm² cable can safely carry 32A-40A, making it suitable for this high-power appliance. (For cookers above 8kW, a 10 mm² cable would be recommended).
     • b) Standard building installation practices: 6 mm² is a common and accepted cable size for dedicated cooker circuits in residential buildings, providing sufficient capacity for most standard cookers.
     • c) Safety: This circuit is typically protected by a 32A or 40A MCB, which ensures the cable is protected from sustained overcurrents and potential fire hazards.

4. 1 water heater

   • Recommended Cable Size: 2.5 mm² copper cable (for heaters up to approximately 3kW)
   • Justification:
     • a) Load: Assuming a typical water heater load of 3000W, the current drawn is approximately 13.04A at 230V. A 2.5 mm² cable can safely carry 20A-27A, which is well within its capacity. (For higher power water heaters, e.g., 4.5kW-6kW, a 4 mm² cable would be recommended).
     • b) Standard building installation practices: 2.5 mm² is a common and cost-effective choice for dedicated 3kW water heater circuits in residential settings.
     • c) Safety: This circuit is typically protected by a 16A or 20A MCB, ensuring adequate overcurrent protection and preventing the cable from overheating.