Residential electrical installation - Circuits

The distribution and division of circuits provides comfort and facilitates rapid location of fault

Subdivision

National standards commonly recommend the subdivision of circuits according to the number of utilization categories in the installation concerned (see Fig. Q8):

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Fig. Q8: Circuit division according to utilization

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• At least 1 circuit for lighting. Each circuit supplying a maximum of 8 lighting points
• At least 1 circuit for socket-outlets rated 10/16 A, each circuit supplying a maximum of 8 sockets. These sockets may be single or double units (a double unit is made up of two 10/16 A sockets mounted on a common base in an embedded box, identical to that of a single unit
• 1 circuit for each appliance such as water heater, washing machine, dish-washing machine, cooker, refrigerator, etc. Recommended numbers of 10/16 A (or similar) socket-outlets and fixed lighting points, according to the use for which the various rooms of a dwelling are intended, are indicated in Figure Q9

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Room function	Minimum number of fixed lighting points	Minimum number of 10/16 A socket-outlets
Living room	1	5
Bedroom, lounge, bureau, dining room	1	3
Kitchen	2	4(1)
Bathroom, shower room	2	1 or 2
Entrance hall, box room	1	1
WC, storage space	1	-
Laundry room	-	1

(1) Of which 2 above the working surface and 1 for a specialized circuit: in addition an independent socket-outlet of 16 A or 20 A for a cooker and a junction box or socket-outlet for a 32 A specialized circuit

Fig Q9: Recommended minimum number of lighting and power points in residential premises 

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Protective conductors

The inclusion of a protective conductor in all circuits is required by IEC and most national standards

IEC and most national standards require that each circuit includes a protective conductor. This practice is strongly recommended where class I insulated appliances and equipment are installed, which is the general case.
The protective conductors must connect the earthing-pin contact in each socket-outlet, and the earthing terminal in class I equipment, to the main earthing terminal at the origin of the installation.
Furthermore, 10/16 A (or similarly sized) socket-outlets must be provided with shuttered contact orifices.

Cross-sectional-area (c.s.a.) of conductors

(see Fig. Q10)

The c.s.a. of conductors and the rated current of the associated protective device depend on the current magnitude of the circuit, the ambient temperature, the kind of installation, and the influence of neighbouring circuits Moreover, the conductors for the phase wires, the neutral and the protective conductors of a given circuit must all be of equal c.s.a. (assuming the same material for the conductors concerned, i.e. all copper or all aluminium).

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Fig. Q10: Circuit-breaker 1 phase + N - 2 x 9 mm spaces

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Figure Q11 indicates the c.s.a. required for commonly-used appliances
Protective devices 1 phase + N in 2 x 9 mm spaces comply with requirements for isolation, and for marking of circuit current rating and conductor sizes.

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Type of circuit single-phase 230 V 1 ph + N or 1 ph + N + PE		c. s. a. of the conductors	Maximum power	Protective device
Fixed lighting		1.5 mm2 (2.5 mm2)	2,300 W	Circuit-breaker Fuse	16 A    10 A
10/16 A		2.5 mm2 (4 mm2)	4,600 W	Circuit-breaker Fuse	25 A 20 A
Individual-load circuits
Water heater		2.5 mm2 (4 mm2)	4,600 W	Circuit-breaker Fuse	25 A 20 A
Dish-washing machine		2.5 mm2 (4 mm2)	4,600 W	Circuit-breaker Fuse	25 A 20 A
Clothes-washing machine		2.5 mm2 (4 mm2)	4,600 W	Circuit-breaker Fuse	25 A 20 A
Cooker or hotplate(1)		6 mm2 (10 mm2)	7,300 W	Circuit-breaker Fuse	40 A 32 A
Electric space heater		1.5 mm2 (2.5 mm2)	2,300 W	Circuit-breaker Fuse	16 A 10 A

(1) In a 230/400 V 3-phase circuit, the c. s. a. is 4 mm² for copper or 6 mm² for aluminium, and protection is provided by a 32 A circuit-breaker or by 25 A fuses.

Fig. Q11: C. s. a. of conductors and current rating of the protective devices in residential installations (the c. s. a. of aluminium conductors are shown in brackets) 

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