Circuits Electrical Wiring

Electrical systems An electrical system must meet several conditions to be satisfactory. It must: 1.) Be safe 2.) Be convenient 3.) Be expandable 4.) Look neat 5.) Provide sufficient current

Service entrance Electrical power comes to the home or farm by overhead or underground wires The power company provides a transformer, service drop, and appropriate wiring to an entrance head An entrance head is a waterproof device used to attach exterior wires to interior wires of building.

Service entrance cont’d Most modern systems have entrance cables that are buried underground Eliminates the need for entrance head Transformers convert high voltage from the power lines to 240 volts from home to farm installations The service drop is an assembly of electrical wires, connectors, and fasteners used to transmit electricity from the transformer to the entrance head and on to the service entrance panel

Service entrance cont’d The service entrance panel is a box with fuses or circuit breakers where electricity enters a building Wires feed from the service drop through the insulated entrance head or underground cables to a meter box The electric meter plugs into the meter box The power continues on to the service entrance panel for distribution to branch circuits

Branch Circuits Most circuits begin from the service entrance panel Branch off into a variety of purposes Generally includes only 1 motor or series of outlets or a series of lighting fixtures It is important to provide the correct size of wire and fuse or circuit breaker for the load on each circuit

Fuses A plug or cartridge containing a strip of metal that meets when more than a specified amount of current passes through it Fuses have to be replaced after it blows

Circuit Breaker A switch that trips and breaks the circuit when more than a specified amount of current passes through it It can be reset after it trips

Caution with fuses and circuit breakers! Fuses and circuit breakers are used to protect circuits from damage and fire Never destroy this protection by installing fuses or breakers with a larger ampere rating than recommended for the size of wire being protected

Meter All electricity that passes through the system is measured by the meter in kilowatthours Kilo = 1,000 Watthour = the use of 1 watt for 1 hour. Ex: A 100 watt bulb that burns for 1 hour will consume 100 watthours of electricity

Meter cont’d Kilowatthour = use of 1,000 watts for 1 hour Meters will convert any amount of electricity into kilowatthours Ex: A power company representative reads the meter at regular intervals and the customer is billed according to the number of kilowatthours used