When working at construction area or for temporary work space,the electrical supplies that we provided can save our times and can speed up the working progress.Because the power tools and lighting or others equipment needed the power supply to completed the tasks.
We must ensure the temporary electrical supply that we install for construction works must in safe condition and comply with wiring regulation and suitable with working area hazards such as explosive or confined space.
The power supply wiring also must be of robust construction to cover electrical requirement and heavy duty to stand from environment such as rain,wind and sun also rough handling.It important to make the wiring condition is safe for our workers from electrical shock and others injuries.
Why temporary electrical power supply important for construction area?
Regarding from electrical regulation,all socket outlets, plugs and couplers must be of the industrial type to BS 4343 and specified by IEE Regulation.It explosion proved,heavy duty and high durability for rough working condition.
IEE Regulation 604-02-02 recommends the following voltages for the distribution of electrical supplies to plant and equipment on construction sites:
1) 400 V three phase
For supplies to major items of plant having a rating above 3.75 kW such as cranes and lifts. These supplies must be wired in armoured cables.
2) 230 V single phase
For supplies to items of equipment which are robustly installed such as flood-lighting towers , small hoists and site offices. These supplies must be wired in armoured cable unless run inside the site offices.
3) 110 V single phase
For supplies to all portable hand tools and all portable lighting equipment.The supply is usually provided by a reduced voltage distribution unit which incorporates splash-proof sockets fed from a centre-tapped 110 V transformer. This arrangement limits the voltage to earth to 55 V, which is recognised as safe in most locations.
* For critical area such as confined spaces,the value of power supply is low and for safety purpose we can used extra low voltage (SELV) for power supply.
Safety interlock for socket outlet and plugs
For safety purpose,we must ensure the industrial plugs have a safety locked to prevents a tool from one voltage being connected to the socket outlet of a different voltage.It can cause a tools damage or serious injury for workers.Normally it have a standard color code to easy identification such as below :
- 440 V – red
- 230 V – blue
- 110 V – yellow
- 50 V – white
- 25 V – violet