Introduction to Electrical control wiring

Power Rails

 Vertical lines on a ladder diagram representing supply power.

Hot Rail

 The left vertical rail that provides the energized power source.

Neutral Rail

The right vertical rail that completes the circuit back to the source.

Conductor

 A wire or path that allows electrical current to flow.

Insulation

 Material covering a conductor to prevent short circuits and protect users.

Wire Size (AWG)

 Gauge system where smaller numbers indicate larger wire diameter.

Solid Wire

 Single conductor wire used for fixed installations.

Stranded Wire

 Flexible multi-strand wire used where bending or movement occurs.

Copper Conductor

 Most common conductor material due to low resistance.

Aluminum Conductor

 Lighter but higher resistance; used in power distribution.

Ladder Diagram

 A schematic that represents control circuits using horizontal rungs and vertical power rails.

Rung

 A single horizontal line representing one circuit path.

Current Path

 Flow of electricity from the hot rail, through devices, and to neutral.

Load Device

 Any output that consumes power (motor, lamp, solenoid

Control Device

 A switch or input device that controls current flow in a rung.

Normally Open (NO) Switch

 A switch that does not conduct until actuated.

Normally Closed (NC) Switch

 A switch that conducts until actuated.

Momentary Switch

 A switch that only stays actuated while pressed.

Maintained Switch

 A switch that stays in its last position after being pressed.

Selector Switch

 Rotary switch used to select modes (Auto/Manual/Off).

Limit Switch Position-sensing switch triggered by machine movement.

Float Switch

 Liquid-level switch that actuates based on buoyancy.

Pressure Switch

 Activates when a system reaches a set pressure.

Temperature Switch Opens or closes based on temperature conditions.

Solenoid Electromagnetic device that creates linear motion when energized.

Pilot Light

 A small light used to indicate system status.

Motor Starter Coil

 Magnetically actuated coil used to start motor contactors.

Relay Coil

 Electromagnetic coil that actuates relay contacts.

Lamp Load

 A lighting device used as an output in ladder circuits.

Heating Element

 A resistive load that converts electrical energy into heat.

Relay Contacts

 Switches controlled by relay coils, not by manual operation.

NO Contact (Relay)

 Opens the circuit until the relay coil energizes.

NC Contact (Relay)

 Closes the circuit until the relay coil energizes.

Overload Contact

 A protective NC device that opens when a motor overload occurs.

Coil Symbol

 Represents a relay or motor starter coil that energizes mechanical contacts.

Interlock Contact

 Prevents unsafe or undesired operations between circuits.

Wire Number

 A unique identifier for a conductor in a schematic.

Component Label

 A letter-number combination identifying devices (ex: CR1, M1).

Terminal Number

 Identifies connection points in a terminal block.

Schematic Labeling Standard

 Ensures wiring and components are consistently identified.

Ground Symbol

 Represents earth ground connection.

Chassis Ground

 Ground reference tied to equipment frame.

chematic Diagram

 Shows electrical connections logically, not physically.

Wiring Diagram

 Shows physical wire routing and device placement.

Pictorial Diagram

 Shows pictures of components rather than symbols.

One-Line Diagram

 Simplified diagram showing electrical power flow.

Ladder Diagram (Control Diagram)

 Represents industrial control logic using rungs and rails.

Lockout/Tagout Point

 Location where stored energy must be isolated before servicing.

Proper Wire Strip Length

 Ensures secure terminal connection without exposed copper.

Tight Terminal Rule

 Loose terminals create heat and arcing hazards.

Correct Gauge Rule

 Using wire too small for load causes overheating.