Components, Symbols, and Circuitry of Air-Conditioning Wiring Diagrams

Electricity for Refrigeration, Heating and Air Conditioning 7th Edition

Chapter 5 Components, Symbols, and Circuitry of Air-Conditioning Wiring Diagrams

Components, Symbols, and Circuitry of Air-Conditioning Wiring Diagrams

Upon completion of this chapter the student will be able to:

• Explain what electrical loads are and their general purpose in heating, cooling, and refrigeration systems

• Give examples of common loads used in heating, cooling, and refrigeration systems

• Identify the symbols of common loads used in heating, cooling, and refrigeration systems

• Explain the purpose of relays and contactors in heating, cooling, and refrigeration systems

• Identify the symbols of relays and contactors in heating, cooling, and refrigeration systems

Components, Symbols, and Circuitry of Air-Conditioning Wiring Diagrams

Upon completion of this chapter the student will be able to:

• Explain the purpose of switches and the types used in heating, cooling, and refrigeration systems

• Identify the symbols of switches in heating, cool ing, and refrigeration systems

• Identify the symbols and purpose of other miscel laneous controls in heating, cooling, and refrigera tion systems

• Identify the different types of wiring diagrams used in the industry and the purpose of each

• Read simple schematic diagrams• Read advanced schematic diagrams

Key Terms

• Contractor• De-energized• Disconnect Switch• Energized• Factual Diagram• Fuse• Heater• Installation Diagram• Load• Magnetic Overload• Magnetic Starter• Motor• Normally• Normally Closed• Normally Open

Key Terms

• Pictorial Diagram• Pilot Duty Device• Pole• Pressure Switch• Push-button Switch• Relay• Schematic Diagram• Signal Light• Solenoid• Switch• Thermal Overload• Thermostat• Throw• Transformer

Loads

• Loads are electrical devices that consume electricity to do useful work.• Load are devices such as motors, solenoids, resistance heaters and other current-

consuming devices.• Load are the most important part of a heating, cooling, or refrigeration system

because they do all the work in the system.

Motors

• A motor is an electrical device that consumes electric energy to rotate a device in an electric system.

• Motors are used in the industry to rotate devices such as compressors, condenser fan motors, pump, and other units that require rotating movement.

Motors

Solenoids

• The solenoid is a device that creates a magnetic field when energized and causes some action to an electric component such as a relay or valve.

• A solenoid is considered to be a load because it consumes electricity to do useful work.

Heaters

• Heaters are loads that are found in many systems and wiring diagrams.• A heater takes electrical energy and converts it to heat.• In some cases, electric resistance heaters are used to heat homes.

Heaters

Signal Lights

• A signal light is a light that illuminated to denote a certain condition in a system.• The letter inside the signal light symbol denotes the color of the signal light.• A signal light is used to show that a piece of equipment is operating or that it is

operating in an unsafe condition.

Contactors and Relay

• Contractors and relays are devices that open and close a set or sets of electric contacts by action of solenoid coil.

• The contactor or relay is composed of a solenoid and the contacts.• When the solenoid is energized, the contacts will open or close, depending on their

original position.

Contactors and Relay

Terms

• Normally refers to the position of a set of contacts when the device is de-energized.• Normally open is a set of contact that are normally open, however, when the relay is

energized the contacts are closed.• Normally closed is a set of contact that are normally close, however, when the relay is

energized the contacts are open.

Magnetic Starters• A magnetic starter is the same type of device as a contactor in terms of the ampere

rating of the device.

Switches

• A switch is a device that opens and closes to control some load in an electric circuit.• Electric switches can be opened and closed by temperature, pressure, humidity, flow

or by some manual means.• The throw indicates how the switch may be operated.

Switches

Terms

• The disconnect switch is used to open and close the main power source to a piece of equipment or load.

• The push-button switch is a symbol used to open and close a set of contacts by pressing a button.

• Thermostats are mechanically operated switches used in most control systems.• Pressure switches are used for different functions in modern control circuits.

Safety Devices

• Safety devices are important in today’s modern systems.• The fuse is the simplest type of overload devices.• The fuse is effective against a large overload, but it is less effective against small

overloads.• The thermal overload is operated by heat.• The magnetic overload is operated by magnetism, which is directly proportional to the

current draw.

Transformers

• The transformer decreases or increases the incoming voltage to a desired voltage.

Schematic Diagrams

• Most modern heating, cooling and refrigeration systems are becoming more complex with more controls and safety devices.

• The schematic diagram is the most useful and easiest to follow of any electric diagram.

• The schematic diagram tells how, when and why a system works.• The schematic wiring diagram includes the symbols and the line representations so

the user can easily identify loads and switches along with the circuits.