1. Circuits
Electrical Wiring

2. 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

3. 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.

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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