Electrical Wiring Diagram Symbols

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Electrical Wiring Diagram Symbols commonly found in HVAC wiring diagrams

High Voltage, Factory Wired

Low Voltage, Factory Wired

High Voltage, Field Wired

Low Voltage, Field Wired

High Pressure Switch
Normally Closed
Opens on increase (rise)/Closes on decrease (drop)
(vacuum & pressure activated)

Low Pressure Switch
Normally Open
Closes on increase (rise)/Opens on decrease (drop)
(vacuum & pressure activated)

Cooling Thermostat
Normally Open
Closes on increase (rise)/Opens on decrease (drop)
(temperature activated)

Heating Thermostat
Normally Closed
Opens on increase (rise)/Closes on decrease (drop)
(temperature activated)

High Liquid Level Switch
Normally Closed
Opens on increase (rise)/Closes on decrease (drop)
(liquid level activated)

Low Liquid Level Switch
Normally Open
Closes on increase (rise)/Opens on decrease (drop)
(Liquid Level activated)

Flow Switch (positive)
Normally Open
Closes on flow or movement
(air, water, liquid flow or movement)

Flow Switch (negative)
Normally Closed
Opens on flow or movement
(air, water, liquid flow or movement)

Normally Open Contacts

Normally Closed Contacts

Disconnect Switch

Magnetic Circuit Breaker
Series Trip

Thermal Circuit Breaker
Series Trip

Normally Open Spring Return Limit Switch

Normally Closed Spring Return Limit Switch

Held Closed Spring Return Limit Switch

Held Open Spring Return Limit Switch

Neutral Position Spring Return Limit Switch

Maintained Position Limit Switch

Selector Switch

Slide Switch

Cam Activated Swtich

Single Pole Single Throw Switch

Single Pole Double Throw Switch

Single Pole Double Throw 3 Position Switch

Double Pole Double Throw Switch

Push Button
Normally Open
Single Circuit
Momentary, Spring Return

Push Button
Normally Closed
Single Circuit
Momentary, Spring Return

Momentary Push Button
Double Circuit
Momentary, Spring Return

Maintained Push Button
Double Circuit

Normally Opened Energized Time Contact
Contact action retarded when coil is ENERGIZED

Normally Closed Energized Time Contact
Contact action is retarded when coil is ENERGIZED

Normally Open De-energized Time Contact
Contact action is retarded when coil is
DE-ENERGIZED

Normally Closed De-energized Time Contact
Contact action is retarded when coil is
DE-ENERGIZED

Fixed Resistor
Glow Coil
Strip Heater

Variable Resistor

Tapped Resistor

Thermistor

Heater type Resistor

Transformer
(variants)

Coil
(variants)

Fusible Link

Ground Connection

Multiple Conductor Cable

Thermocouple

Thermal Overload

Bi-Metal Switch

Connectors

Electrode
Ignitor

Crank Case Heater

Meter
* denotes type

Variable Inductor

Fixed Inductor

Multi Pole Double Throw Switch

Multi Pole Single Throw Switch

Electrically Operated Switch
* Indicates magnetic coil,motor, or thermal element

Foot Switch
Normally Open

Foot Switch
Normally Closed

Auto Transformer

Current Transformer

Variable Transformer

Transformer - Auto Adjustable Tapped

Fixed Iron Core Coil

Fixed Air Core Coil

Adjustable Iron Core Coil

Adjustable Air Core Coil

Motor
Single Phase
2 Lead

Motor
Single Phase
3 Lead

Motor
3 Phase
3 Lead

Motor
3 Phase
6 Lead
Dual Windings

Bi-Metallic Thermal Overload

Bi-Metallic Thermal Overload
with heater

Microphone

Horn or Siren

Buzzer or Bell

Push to Test Lamp

Shielded Cable

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