These are some the decisions which the electrical contractor must make when
designing installation which meets the requirements the customer and the IEE
Regulations.2. V/Am V
Since this less than the maximum permissible value for lighting circuit 6.2. were able route the cable under the floor, clipped direct conduit or
trunking wall, may able use 6mm cable for this load.5kw) 6.6kw) 40
Key Facts
Volt drop
Maximum permissible volt drop on
230V supplies:
● for lighting 6. the volt drop for this cable length and load equal to:
4 06
3
.Basic Electrical Installation Work
302
Now test for volt drop: from the table shown Table 14.4 Cable Size for Standard Domestic Circuits
Type final circuit Cable size
(twin and
earth)
MCB
rating,
Type (A)
Maximum floor
area covered
by circuit (m2
)
Maximum
length of
cable run (m)
Fixed lighting 1. must, therefore, use installed reference method of
Table 4.5 30
13A socket outlets (Ring circuit) 2.5 30
Storage radiator 2.0 35
Cooker (oven and hob) 6.
In this table, assuming standard 230V domestic installation, hav-
ing sheathed earth PME supply terminated 100A HBC fuse the
mains position.3 the volt drop per ampere per metre
for 10mm cable 4.5 100 90
13A socket outlets (Ring circuit) 4.
If you are unsure the standard fuse and MCB rating protective devices, you can refer to
Fig.9 10mm
cable satisfies the current and drop voltage requirements when the circuit protected by
an MCB.5 60
Immersion heater 2.
Compare the values column with those column When the cable clipped
direct wall surface the current rating higher because the cable cooler.4mV. the
alternative route was longer, you would need test for volt drop before choosing the
cable.5 30
13A socket outlets (Radial circuit) 2. You can see how the
current carrying capacity cable varies with the installed method looking Table 4.4 gives guide cable size.
Table 14. However, for standard
domestic circuits, Table 14.4 Appendix the IEE Regulations.0 40
Shower (up 9. This cable run loft that gets hot summer and has thermal insulation
touching one side the cable.0 40
Shower (up 7.0 40
Fixed lighting 1.5 30
Cooker (oven only) 2. Final circuits are fed from consumer unit, having Type B,
MCB protection and wired PVC insulated and sheathed cables with cop-
per conductors having grey thermoplastic PVC outer sheath white
. 3.
Cable size for standard domestic circuits
Appendix the IEE Regulations (BS: 7671) and Appendix the IEE On
Site Guide contain tables for determining the current carrying capacities of
conductors which looked the last section.5V
IEE Regulation 525 and Appendix 12.9V
● for other uses 11
