1. E1 – Electrical Fundamentals
# 4 - Symbols and Wiring Diagrams

2. Electrical Loads Loads Examples: Consume electricity Do work Motors
Solenoids
Heaters
Lights
© 2005 Refrigeration Training Services - E1#4 Symbols and Wiring Diagrams v1.2

3. Motors Common symbols: (Letters tell what motor is represented) COMP
EFM
IFM
COMP
EFM
IFM
COMPressor
Evaporator Fan Motor
Indoor Fan Motor
COMP
CFM
OFM
CFM
OFM
COMP
Condenser Fan Motor
Outdoor Fan Motor
© 2005 Refrigeration Training Services - E1#4 Symbols and Wiring Diagrams v1.2

4. 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 - E1#4 Symbols and Wiring Diagrams v1.2

5. Magnetic coil energized
Solenoid Valve
Magnetic coil energized
Plunger pulled up
Power off
Plunger drops
This solenoid valve is in the NC (normally closed) position. The flow of liquid or vapor is stopped.
When the magnetic coil is energized the plunger is raised and fluid passes under the disk and through the pipe in the direction of the arrow stamped on the side of the valve.
Fluid flows
Plunger
Fluid stops
Seat
© 2005 Refrigeration Training Services - E1#4 Symbols and Wiring Diagrams v1.2

6. Heaters Convert electrical energy to heat
Symbol for resistance heaters:
Examples of heaters:
Auxiliary strip heaters
Crankcase heaters
© 2005 Refrigeration Training Services - E1#4 Symbols and Wiring Diagrams v1.2

7. R B G Signal Lights R Red B Blue G Green, etc.
Used to show when something is operating,
or when there is a problem.
Symbol for signal lights: R B G
Letter in the center denotes bulb color:
R Red
B Blue
G Green, etc.
© 2005 Refrigeration Training Services - E1#4 Symbols and Wiring Diagrams v1.2

8. 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 E2 Subject 3 “Contactors and Motor Starters”
© 2005 Refrigeration Training Services - E1#4 Symbols and Wiring Diagrams v1.2

9. Contactor Cutaway LINE 1 Power In CONTROL CIRCUIT 2 Coil 3 Contacts
LOAD
CONTROL CIRCUIT
LINE
1 Power In
2 Coil
3 Contacts
4 Power Out
© 2005 Refrigeration Training Services - E1#4 Symbols and Wiring Diagrams v1.2

10. Symbols for Contactors
Coil
Contact
Single pole
Double pole
Triple pole
115v
v, 1
v, 3
Symbols are shown “de-energized” (no power) with contacts “normally open”
© 2005 Refrigeration Training Services - E1#4 Symbols and Wiring Diagrams v1.2

11. Visualizing symbols with power on
The following slide illustrates what happens when the power is turned on
© 2005 Refrigeration Training Services - E1#4 Symbols and Wiring Diagrams v1.2

12. Contactor coil “energized”
Contacts close
Coil
Contact
Single pole
Double pole
Triple pole
115v
v, 1
v, 3
© 2005 Refrigeration Training Services - E1#4 Symbols and Wiring Diagrams v1.2

13. 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 - E1#4 Symbols and Wiring Diagrams v1.2

14. Coil “de-energized” (no power)
Symbols for RELAYS
Coil “de-energized” (no power)
Normally Open
“NO”
1 2
Single pole
Double pole
Triple pole
#1 NO
#2 NC
#1 NC
#2 NO
#3 NC
Normally Closed
“NC”
© 2005 Refrigeration Training Services - E1#4 Symbols and Wiring Diagrams v1.2

15. Visualizing symbols with power on
The following slide illustrates what happens when the power is turned on
© 2005 Refrigeration Training Services - E1#4 Symbols and Wiring Diagrams v1.2

16. Coil “energized” (powered up)
Symbols for RELAYS
Coil “energized” (powered up)
Normally Open
“NO”
1 2
Single pole
Double pole
Triple pole
#1 NO
#2 NC
#1 NC
#2 NO
#3 NC
Normally Closed
“NC”
© 2005 Refrigeration Training Services - E1#4 Symbols and Wiring Diagrams v1.2

17. 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 - E1#4 Symbols and Wiring Diagrams v1.2

18. Single Throw Switch Symbols
Switch closed
Switch open
Single Pole – Single Throw
(SPST) L1
Switch closed
Switch open L2
Double Pole – Single Throw
(DPST)
© 2005 Refrigeration Training Services - E1#4 Symbols and Wiring Diagrams v1.2

19. Double Throw Switches Each switch position closes a circuit
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20. Single Pole - Double Throw (SPDT)
Contacts 1-2 closed
Contacts 1-2 open 2 1
Contacts 1-3 open
Contacts 1-3 closed 3
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21. Double Pole – Double Throw (DPDT)
Contacts 1-3 closed
Contacts 1-2 closed 2 1 3 5
Contacts 4-5 closed 4 6
Contacts 4-6 closed
© 2005 Refrigeration Training Services - E1#4 Symbols and Wiring Diagrams v1.2

22. Thermostats
COOL
OFF
HEAT ON
FAN
AUTO B O W Y G R 70 80 60 50
Symbol depicts a bimetal spring which closes and opens the contacts
Tstats are usually shown in their “normal” position, which is open
© 2005 Refrigeration Training Services - E1#4 Symbols and Wiring Diagrams v1.2

23. 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 - E1#4 Symbols and Wiring Diagrams v1.2

24. 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
the arm closes the contacts
© 2005 Refrigeration Training Services - E1#4 Symbols and Wiring Diagrams v1.2

25. Pressure Controls Symbol depicts a bellows which operates the contacts
Pressure safety controls are usually shown in their “normal” position, which is closed
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26. Low Pressure Control
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27. 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
the arm opens the contacts
© 2005 Refrigeration Training Services - E1#4 Symbols and Wiring Diagrams v1.2

28. 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 - E1#4 Symbols and Wiring Diagrams v1.2

29. Fuses and Overloads
Symbols for safety devices, such as fuses and overloads, are usually shown closed
© 2005 Refrigeration Training Services - E1#4 Symbols and Wiring Diagrams v1.2

30. Safety Device Symbols Fuses Overloads Bimetal overload:
High heat and high amperage open this overload switch.
Thermal overload relay:
Excessive amperage heats the thermal element, which opens the switch.
Magnetic overload relay:
Excessive amperage creates a magnetic field, which opens the switch.
© 2005 Refrigeration Training Services - E1#4 Symbols and Wiring Diagrams v1.2

31. Introduction to Wiring Diagrams
The following slide is a diagram of an attic exhaust fan
The fan is controlled by a standard switch
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32. Attic Exhaust Fan FM Switch controls fan L1 N
© 2005 Refrigeration Training Services - E1#4 Symbols and Wiring Diagrams v1.2

33. 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 - E1#4 Symbols and Wiring Diagrams v1.2

34. Simple Circuit for Attic Exhaust Fan
Add a Thermostat FM
© 2005 Refrigeration Training Services - E1#4 Symbols and Wiring Diagrams v1.2

35. END OF Symbols and Wiring Diagrams
© 2005 Refrigeration Training Services - E1#4 Symbols and Wiring Diagrams v1.2