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Electrical Skills - Wiring Diagrams

Basic Wiring: Chapter 2


Wiring Diagrams


In this module, we will review wiring diagrams. You will learn how to use a wiring diagram to wire a system. Skip to quiz!


Components


Recall that a wiring diagram is a blueprint of an electrical system. Wiring diagrams display:

  • The components in a system,

  • The wiring and

  • The flow of current

There are a few types of wiring diagrams, including:

  • Ladder diagrams, and

  • Schematic diagrams

For wiring, you will mainly use a schematic diagram. Being able to read a schematic diagram is one of the most important skills for wiring.

The schematic diagram will tell us what components are in the system. The diagram will also show us the wiring between each component.


Recall that a schematic diagram uses symbols to represent a component. In the image, you can see the symbols for a dual run capacitor, start capacitor, and a start thermistor.


You can also see the wiring between each component. In this image, a “YEL” wire runs from the start capacitor to the COM terminal on the dual run capacitor. “YEL” stands for a yellow wire.


Recall that wiring diagrams have:

  • Factory wiring, and

  • Field wiring.

Factory wiring has already been installed by the manufacturer. Any wires that are factory installed have already been wired.


Field wiring is wiring that must be done in the field. Any wire that is labeled field wiring must be connected by you.


Component Connections


Recall that we separate wiring into three categories:

  • Hot wires,

  • Neutral wires, and

  • Ground wires

Each wire has a different job in the circuit.

Each component in the circuit will need to have a hot wire. The hot wire is typically black or red. Some components in the circuit will need to have a ground and a neutral wire.


Recall that the hot wire delivers power to each component. You can think of the hot wire as delivering power from the source to the entrance of the component.


Recall that the neutral wire connects the last component in the circuit back to the power source. The neutral wire creates a complete path for current to flow.


Recall that the ground wire connects the circuit to the earth. The ground wire protects us if the system has a short circuit.


Series/Parallel


Recall that components can be wired in two ways:

  • Series, and

  • Parallel

A wiring diagram shows you if components are wired in series or parallel.


Recall that components wired in series only have one path for current to flow. The current moves from the exit of one component directly to the entrance of the next component.

For example, look at the diagram to the right. You can see that there are three switches.


These switches are in series with each other. There is only one path for current to flow once it exits a switch.


Components can also be wired in parallel. Recall that components in parallel have multiple paths for current to flow.


For example, look at the schematic diagram to the right. The OFM, COMP, and SR are wired in parallel. Current can flow through three paths once it exits the “21” terminal of the contactor.


Reading a Diagram


In the picture to the right, you can see a schematic diagram. Recall that a schematic diagram shows the wiring and components of a system.

L1 and L2 are the wires which go to and from the power source. L1 is the hot wire. It carries 120V to the components. L2 is the neutral wire. It carries 120V back to the source.


In this graphic, you can see the hot wire (L1) enters on the left side of the schematic. L1 brings power to the 11 terminal of the contactor switch. L1 also brings power to the CHS.


This same pattern continues throughout the diagram. The hot wire will carry the voltage to each component in the diagram.


L2 acts as the neutral wire for the circuit. You can find the neutral wire in the diagram at terminal 23 of the contactor.


On this diagram, you will find the ground wire symbol in the top left corner. You will also find a grounding symbol on the outdoor fan motor (OFM).


Note that the schematic diagram also includes the color of the wires. Above each wire you will see a label like “YEL” which stands for a yellow wire. “YEL/BLU” stands for a yellow and blue wire.


In this module, we explained the importance of a wiring diagram for wiring. The wiring diagram will show you the components in a system and how they are wired.




Question #1: A schematic diagram displays:

  1. Components in a system

  2. Wiring between components

  3. Both

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Answer: Both

A schematic diagram displays the components and wiring in an electrical system.


Question #2: Factory wiring is wired:

  1. In the field

  2. By the manufacturer

  3. By the business owner

  4. All of the above

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Answer: By the manufacturer

Factory wiring has been done by the manufacturer. All products they sell will come with factory wiring pre-installed.


Question #3: Field wiring is wired:

  1. On the job site

  2. By the manufacturer

  3. By the business owner

  4. All of the above

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Answer: On the job site

Field wiring is done on the job site. Field wiring is what you must wire in order for a system to function.


Question #4: Components in series have:

  1. One path for current to flow

  2. Two paths for current to flow

  3. Multiple paths for current to flow

  4. Both “B” and “C”

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Answer: One path for current to flow

Wires in series have only one path for current to flow. It will move from the exit of one component directly to the entrance of the next component.


Question #5: Components in parallel have:

  1. One path for current to flow

  2. Multiple paths for current to flow

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Answer: Multiple paths for current to flow

Components in parallel have more than one path for current to flow.


Question #6: L1 and L2 are:

  1. Your power source

  2. Components

  3. Contactors

  4. Relays

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Answer: Your power source

L1 and L2 are the incoming power for the system. L1 acts as the hot wire. L2 is the neutral wire.


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