Residential electrical installation - Circuits

Subdivision

The proper separation of circuits provides service continuity and eases rapid location of fault

National standards commonly recommend the subdivision of circuits according to the number of utilization categories in the installation concerned (see Figure Q10):

• At least one lighting circuit, each circuit supplying several rooms for a maximum surface of 50 m²,
• At least one socket-outlets circuit rated 16 A (rating according to National socket-outlet system), each circuit supplying a reasonable number of socket-outlets in series, taking into account the wiring cross-section area used (1.5 mm² or 2.5 mm²), the wiring lengths (voltage drops) and the temperature rise effects on each connection, according to the foreseeable applications used.
• One dedicated circuit for each "high load" appliance such as washing machine, dish-washer, cooker etc. Water heater and fixed heater units shall be connected by terminals (not socket-outlet neither connector).

Fig. Q10 – Circuit division according to application

Recommended number of socket-outlets and fixed lighting points

An example of recommended number of socket-outlets and fixed lighting points, according to the applications and the locations in dwellings, are given in Figure Q11

Fig. Q11 – Recommended minimum number of lighting and power points in residential premises

Room function	Minimum number of fixed lighting points	Minimum number of 10/16 A socket-outlets
Living room	1	5
Bedroom, lounge, living and dining room	1	3
Kitchen	2	4
Bathroom	2	1
Entrance, hall, stairs	1	1
Cellar, storage space	1	1
Laundry room	1	2

Protective conductors

Implementation of a protective conductor (PE) for all circuits is required by IEC and most of national installation rules

IEC 60364 and most national standards require implementation of protective conductor for each circuit. This practice is mandatory where equipment provided for earthing (Class I) may be connected or installed, and shall be seen as the general case for all circuits including circuits supplying socket outlets.

The protective conductors must connect the earthing contact in each socket-outlet to the main earthing terminal at the origin of the installation.

Furthermore, in some countries, 16 A (13 A in UK) household socket-outlets must be provided with shutters, at least in rooms where children are often present, and in places where water is present.

Cross-section area of conductors

The cross-section area of conductors and the rated current of the associated protective device depend on the load(s) connected to the circuit, the ambient temperature, the material of construction where the cables are located, the type of installation, and the influence of neighboring circuits (refer to Sizing and protection of conductors ).

Moreover, the conductors for the phase, the neutral and the protective conductors of a given circuit must have the same cross section area up to 32 A circuits.