E 1 Electrical Fundamentals 4 Symbols and Wiring

E 1 – Electrical Fundamentals # 4 - Symbols and Wiring Diagrams

Electrical Loads • Loads – Consume electricity – Do work • Examples: – Motors – Solenoids – Heaters – Lights © 2005 Refrigeration Training Services - E 1#4 Symbols and Wiring Diagrams v 1. 2 2

Motors Common symbols: (Letters tell what motor is represented) COMP EFM IFM COMPressor Evaporator Fan Motor Indoor Fan Motor COMP CFM OFM Condenser Fan Motor Outdoor Fan Motor COMP © 2005 Refrigeration Training Services - E 1#4 Symbols and Wiring Diagrams v 1. 2 3

Solenoid • When current flows through a coil of wire it creates a magnetic field • This will cause an action in a relay or valve • Electrical symbol for a solenoid coil: © 2005 Refrigeration Training Services - E 1#4 Symbols and Wiring Diagrams v 1. 2 4

Solenoid Valve Magnetic coil energized Plunger pulled up Power off Plunger drops Plunger Fluid stops Fluid flows Seat © 2005 Refrigeration Training Services - E 1#4 Symbols and Wiring Diagrams v 1. 2 5

Heaters • Convert electrical energy to heat • Symbol for resistance heaters: • Examples of heaters: – Auxiliary strip heaters – Crankcase heaters © 2005 Refrigeration Training Services - E 1#4 Symbols and Wiring Diagrams v 1. 2 6

Signal Lights Used to show when something is operating, or when there is a problem. Symbol for signal lights: B R G Letter in the center denotes bulb color: R Red B Blue G Green, etc. © 2005 Refrigeration Training Services - E 1#4 Symbols and Wiring Diagrams v 1. 2 7

Contactor • It is a mechanical switch, operated by a magnetic coil • Energizing the coil closes the contacts • Power flows through the contacts to the load • For more on contactors: – See Topic E 2 Subject 3 “Contactors and Motor Starters” © 2005 Refrigeration Training Services - E 1#4 Symbols and Wiring Diagrams v 1. 2 8

Contactor Cutaway LINE 1 Power In CONTROL CIRCUIT 2 Coil 3 Contacts 4 Power Out LOAD © 2005 Refrigeration Training Services - E 1#4 Symbols and Wiring Diagrams v 1. 2 9

Symbols for Contactors Coil Contact Single pole 115 v Double pole 208 -230 v, 1 Triple pole 208 -230 v, 3 Symbols are shown “de-energized” (no power) with contacts “normally open” © 2005 Refrigeration Training Services - E 1#4 Symbols and Wiring Diagrams v 1. 2 10

Visualizing symbols with power on • The following slide illustrates what happens when the power is turned on © 2005 Refrigeration Training Services - E 1#4 Symbols and Wiring Diagrams v 1. 2 11

Contactor coil “energized” Contacts close Coil Contact Single pole 115 v Double pole 208 -230 v, 1 © 2005 Refrigeration Training Services - E 1#4 Symbols and Wiring Diagrams v 1. 2 Triple pole 208 -230 v, 3 12

Relays • Similar to contactors • Usually under 20 amp capacity • Contacts may be: – Normally open (NO) – Normally closed (NC) – Or a combination of NO and NC © 2005 Refrigeration Training Services - E 1#4 Symbols and Wiring Diagrams v 1. 2 13

Symbols for RELAYS Coil “de-energized” (no power) Normally Open “NO” 1 Single pole Double pole Triple pole #1 NO #2 NC #1 NC #2 NO #3 NC 2 Normally Closed “NC” © 2005 Refrigeration Training Services - E 1#4 Symbols and Wiring Diagrams v 1. 2 1 2 3 14

Visualizing symbols with power on • The following slide illustrates what happens when the power is turned on © 2005 Refrigeration Training Services - E 1#4 Symbols and Wiring Diagrams v 1. 2 15

Symbols for RELAYS Coil “energized” (powered up) Normally Open “NO” 1 Single pole Double pole Triple pole #1 NO #2 NC #1 NC #2 NO #3 NC 2 Normally Closed “NC” © 2005 Refrigeration Training Services - E 1#4 Symbols and Wiring Diagrams v 1. 2 1 2 3 16

Introduction to switches • Switches open and close contacts to control a load – Contact: • the conducting part of a switch – Poles: • the number of contacts in a switch – Throw: • the number of closed contact positions per pole © 2005 Refrigeration Training Services - E 1#4 Symbols and Wiring Diagrams v 1. 2 17

Single Throw Switch Symbols Switchclosed open Switch Single Pole – Single Throw (SPST) L 1 L 2 Switchclosed open Switch Double Pole – Single Throw (DPST) © 2005 Refrigeration Training Services - E 1#4 Symbols and Wiring Diagrams v 1. 2 18

Double Throw Switches • Each switch position closes a circuit © 2005 Refrigeration Training Services - E 1#4 Symbols and Wiring Diagrams v 1. 2 19

Single Pole - Double Throw (SPDT) open Contacts 1 -2 closed 2 1 3 Contacts 1 -3 closed open © 2005 Refrigeration Training Services - E 1#4 Symbols and Wiring Diagrams v 1. 2 20

Double Pole – Double Throw (DPDT) 1 -2 closed Contacts 1 -3 2 1 3 5 4 6 Contacts 4 -6 4 -5 closed © 2005 Refrigeration Training Services - E 1#4 Symbols and Wiring Diagrams v 1. 2 21

AT FF ON O COO L © 2005 Refrigeration Training Services - E 1#4 Symbols and Wiring Diagrams v 1. 2 70 80 AUTO • Symbol depicts a bimetal spring which closes and opens the contacts • Tstats are usually shown in their “normal” position, which is open 60 50 N FA Thermostats HE B G O 50 R 60 Y 70 80 W 22

Symbols for Thermostats Cooling thermostat In actual operation As the temperature goes up the rise in temperature causes the bimetal to expand the expanded bimetal raises the arm the raised arm closes the contacts © 2005 Refrigeration Training Services - E 1#4 Symbols and Wiring Diagrams v 1. 2 23

Symbols for Thermostats Heating thermostat In actual operation As the room temperature falls the fall in temperature causes the bimetal to contract the contracted bimetal pulls down on the arm closes the contacts © 2005 Refrigeration Training Services - E 1#4 Symbols and Wiring Diagrams v 1. 2 24

Pressure Controls • Symbol depicts a bellows which operates the contacts • Pressure safety controls are usually shown in their “normal” position, which is closed © 2005 Refrigeration Training Services - E 1#4 Symbols and Wiring Diagrams v 1. 2 25

Low Pressure Control © 2005 Refrigeration Training Services - E 1#4 Symbols and Wiring Diagrams v 1. 2 26

Symbols for Pressure Controls Low pressure control In actual operation As the system pressure falls the fall in pressure causes the bellows to deflate the deflated bellows pulls down on the arm opens the contacts © 2005 Refrigeration Training Services - E 1#4 Symbols and Wiring Diagrams v 1. 2 27

Symbols for Pressure Controls High pressure control In actual operation As the system pressure rises the rise in pressure causes the bellows to inflate the inflated bellows raises the arm the raised arm opens the contacts © 2005 Refrigeration Training Services - E 1#4 Symbols and Wiring Diagrams v 1. 2 28

Fuses and Overloads • Symbols for safety devices, such as fuses and overloads, are usually shown closed © 2005 Refrigeration Training Services - E 1#4 Symbols and Wiring Diagrams v 1. 2 29

Safety Device Symbols Bimetal overload: High heat and high amperage open this overload switch. Thermal overload relay: Excessive amperage heats thermal element, which opens the switch. Magnetic overload relay: Excessive amperage creates a magnetic field, which opens the switch. © 2005 Refrigeration Training Services - E 1#4 Symbols and Wiring Diagrams v 1. 2 30

Introduction to Wiring Diagrams • The following slide is a diagram of an attic exhaust fan – The fan is controlled by a standard switch © 2005 Refrigeration Training Services - E 1#4 Symbols and Wiring Diagrams v 1. 2 31

Attic Exhaust Fan L 1 N Switch controls fan FM © 2005 Refrigeration Training Services - E 1#4 Symbols and Wiring Diagrams v 1. 2 32

Adding controls to the diagram • A thermostat replaces the standard switch • This allows the fan to operate automatically, based on attic temperatures © 2005 Refrigeration Training Services - E 1#4 Symbols and Wiring Diagrams v 1. 2 33

Simple Circuit for Attic Exhaust Fan L 1 N Add a Thermostat FM © 2005 Refrigeration Training Services - E 1#4 Symbols and Wiring Diagrams v 1. 2 34

© 2005 Refrigeration Training Services - E 1#4 Symbols and Wiring Diagrams v 1. 2 35