Residential electrical installation - Circuits

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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):

FigQn08.jpg

Fig. Q8: Circuit division according to utilization

  • 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
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 

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. Q11)

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.[1] (assuming the same material for the conductors concerned, i.e. all copper or all aluminium).

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.

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            
FigQn11a.jpg
1.5 mm2
(2.5 mm2)
2,300 W Circuit-breaker Fuse 16 A   
10 A
10/16 A
FigQn11b.jpg
2.5 mm2
(4 mm2)
4,600 W Circuit-breaker Fuse 25 A
20 A
Individual-load circuits
Water heater
FigQn11c.jpg
2.5 mm2
(4 mm2)
4,600 W Circuit-breaker Fuse 25 A
20 A
Dish-washing machine
FigQn11d.jpg
2.5 mm2
(4 mm2)
4,600 W Circuit-breaker Fuse 25 A
20 A
Clothes-washing machine
FigQn11e.jpg
2.5 mm2
(4 mm2)
4,600 W Circuit-breaker Fuse 25 A
20 A
Cooker or hotplate
FigQn11f.jpg
6 mm2
(10 mm2)
7,300 W Circuit-breaker Fuse 40 A
32 A
Electric space heater
FigQn11g.jpg
1.5 mm2
(2.5 mm2)
2,300 W Circuit-breaker Fuse 16 A
10 A

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)


References

  1. ^ Here we speak about household installation where conductors used are isolated conductors or multi-core with PE included and in that case PE conductors is allowed to have same c.s.a. as active conductors.


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