Competency 8

[HOME]

8.1 State the purpose of a consumer’s unit.

The purpose of the consumer unit is to house the different components used:-

1.     Isolation of the consumer unit from the supply.

2.     Protections for Circuit segregation (separation)

                                                  

8.2 List the standard sizes of main cables entering a consumer’s unit.

The standard sizes of main cables entering a consumer’s unit are:

1.      6 mm²

2.      10 mm²

8.3 State the common ratings of main fuse/circuit-breaker likely to be     found in a consumer's unit installed in domestic premises.

Ratings depend on the total maximum load of the outgoing circuits.

Ratings of main fuses

1. 45A
2. 60A

Ratings of main circuit breakers

1. 40A
2. 45A
3. 63A
4. 100A

8.4 List the standard size of fuse likely to be found in a consumer’s unit.

Fuse	Colour	Typical Uses
5 amp	White	Lighting / small plug circuits
15 amp	Blue	Immersion/storage heaters
20 amp	Yellow	Smaller radial circuits / water heaters
30 amp	Red	Ring circuits (sockets), cookers, showers, radial circuits
45 amp	Green	Cookers/showers

8.5 Interpret the colour code of fuses.

Consumer unit with fuses

Colour -code for rewirable fuses

Rewirable fuses

Consumer unit with Circuit Breakers 

Note: Circuit breakers are replacing fuses as the latter are becoming obsolete.

Regulations recommend that New buildings must be equipped with these devices and at least a RCD.  

Ratings of outgoing circuit breakers

Circuit breaker	Typical Uses
6 amp	Lighting
10 amp	Lighting / small plug circuits
16 amp	Immersion/storage heaters
20 amp	Smaller radial circuits / water heaters
25 amp
32 amp	Ring circuits (sockets), cookers, showers, radial circuits
40 amp
45 amp	Cookers/showers

MAIN SWITCH