House wiring-Tools and Components-

Electrical Safety in House and industry

P.Raja,

Assistant Professor, EEE

NIT Trichy

Domestic wiring in a house requires a number of electric devices to runsimultaneously.

They should be independent of each other i.e. the working of one deviceshould not depend on the working of another device.

For example, the working of a fan should not be affected when a bulb inthe room gets fused.

In parallel circuits, if one appliance stops working, all other applianceswork as usual. Hence, parallel circuiting is used in house wiring or in

lights used to decorate buildings on occasions. This is done to ensure

that if one bulb fuses, the others remain functioning.

Typical House Wiring

Stair case wiring

Ceiling Fan Wiring

A: Fluorescent Tube

B: Power (220 Volts)

C: Starter

D: Switch (Bi-metallic

thermostat)

E: Capacitor

F: Filaments

G: Ballast

Fluorescent Lamp Connection

Tools

Multimeter

Soldering Iron

Wire StripperWire Cutter

Components

Bayonet Caps

Baton Lamp Holder

Angle holder

Ceiling Rose

Electric Socket and Plug cover

Plug with 3 pins

Colour Codes

Iron Clad Main Switch

Flush type Switch

Tumbler type Switch

MCBs

Basic Electrical Safety at House

Adequate electric wiring should be ensured along withincreased in load (appliances)

Cables and fitting deteriorate with time proper rewiring

Indications for potential safety problems:

Over heating of plugs, sockets and cables

Sparking/ arcing on fittings

Frequent Fuse/MCB operation

Always read the manufactures instruction manual beforeusing and keep the instruction for future reference.

Handling and Maintaining of Installation of Appliances

DO NOT drag an appliance by the flex(wire) or pull the flex to removethe plug from the socket

DO NOT plug any appliance into a light bulb holder

AVOID using multiple outlet adaptors; use fused multi-socket boardsinstead; better to have additional sockets fitted

REPLACE socket outlets if, after constant use, the plug fits loosely inthe socket or if it shows of heating; a loose contact is potentially

dangerous.

REPLACE plastic-type lamp-holders if they show signs of deteriorating cracking or discoloration. Replace them with heat-resistant types and

renew the flex.

DO NOT exceed the maximum bulb wattage recommended for fittings orlamp-holders.

DO ensure that all fluorescent fittings and metal chandeliers areEARTHED.

Handling and Maintaining of Installation of Appliances

DO check flexes regularly Electric iron, kettles and vacuum cleanersect.,

DO make sure that you have long enough flex to comfortably work.

DO NOT make joints in a given flex.

DO NOT repair defective flex or damaged; replace it.

DO NOT use telephone/alarm wire for any main-voltage appliances orconnections.

Electrical Safety in the Kitchen

Special care should be taken when using appliances in the kitchen,where the combination of electricity, water, trailing flexes and hot

surfaces makes it potentially more dangerous.

DO unplug an electric kettle before filling it and make sure that theelement is covered by the water.

DO NOT have flexes trailing across either the cooker or sink

DO NOT wrap flexes around kettles, irons or toasters while they are stillhot; the flexes may be damaged

DO NOT clean or wash any appliances while it is still plugged in.

DO NOT handle plugs or switches when your hands are wet.

Electrical Safety in the Bathroom

Special care should be taken when using appliances in Bathroom.Thats because the wet surroundings pose a greater risk of electricshock anywhere else in the house.

NO socket outlets, other than specially designed shaver outlets areallowed in bathroom.

All electric heaters and water-heaters in a bathroom fixed andpermanently wired; none should be used through a plug and socket.

Pull cord switch or by a switch located outside the bathroom

Safe Installation of Plug

Wiring a Plug Safely Connect each wire in appropriate terminal

No loose strands of wire exposed and all screws are fully tightened.

When the wires are securely connected to the terminals make sure that theflex is properly anchored in the plug by the cord grip.

Safety devices/installations

Fuse

MCB

RCD ELCB, RCCB

Surge Arrester

Earthing

RCDs Residual Current Devices

Additional protection against hazards of electric shock or fire

New domestic installation MUST be provided with an RCD on allsocket, water-heater and electric shower circuit.

It detects abnormal flow of electricity out of a circuit leak out.

Used to be called as ELCB Earth Leakage Circuit Breaker

RCDs are supplied in a range of current-carrying capacities andsensitivities. A high sensitivity 30 mA.

Test : All RCDs has test buttons. Test button should be operatedat regular intervals once in a month