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Electrical Wiring Diagram Symbols 

87 terms by keith_spring 

Electrical Wiring Diagram Symbols commonly found in HVAC wiringdiagrams

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 & ressure activated

Low Pressure Switch Normally Open Closes on increase

(rise)/Opens on decrease (drop) (vacuum & pressure activated) 

Cooling ThermostatNormally OpenCloses on increase (rise)/Opens on decrease (drop)(temperature activated)

Heating ThermostatNormally Closed Opens on increase (rise)/Closes on

decrease (drop)(temperature activated)

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High Liquid Level SwitchNormally Closed Opens on increase (rise)/Closes ondecrease (drop)(liquid level activated)

Low Liquid Level SwitchNormally Open Closes on increase (rise)/Opens ondecrease (drop)(Liquid Level activated)

Flow Switch (positive)Normally Open

Closes on flow or movement(air, water, liquid flow or movement)

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

Normally Open Contacts

Normally Closed Contacts

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Magnetic Circuit Breaker  

Series Trip

Disconnect Switch

Thermal Circuit BreakerSeries Trip

Normally Open

Spring ReturnLimit Switch

Normally Closed

Spring Return

Limit Switch 

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Held ClosedSpring ReturnLimit Switch

Held OpenSpring Return

Neutral PositionSpring ReturnLimit Switch

Maintained PositionLimit Switch

Selector Switch

Slide Switch

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Cam Activated Swtich

Cam Activated Switch

Double Pole Double Throw Switch

Single Pole Double Throw 3 Position Switch

Single Pole Double Throw Switch

Single Pole Single Throw Switch 

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Push ButtonNormally OpenSingle CircuitMomentary, Spring Return

Push ButtonNormally ClosedSingle CircuitMomentary, Spring Return

Momentary Push ButtonDouble CircuitMomentary, Spring Return

Maintained Push Button

Double Circuit

Normally OpenedEnergized Time ContactContactaction retarded when coil is

ENERGIZED

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Normally Closed EnergizedTime ContactContact action is retardedwhen coil is ENERGIZED

Normally Open De-energizedTime ContactContact action is retardedwhen coil is DE-ENERGIZED

Normally Closed De-energizedTime ContactContact action is retardedwhen coil is DE-ENERGIZED

Fixed ResistorGlow CoilStrip Heater

Variable Resistor  

Tapped Resistor

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Thermistor

Heater type Resistor

Transformer (variants)

Capacitor

Coil (variants)

Fuse

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Ground Connection 

Thermal Overload

Thermocouple

Light 

Multiple Conductor Cable 

Fusible Link 

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Bi-Metal Switch

Connectors

ElectrodeIgnitor

Crank Case Heater

Meter

Variable Inductor

Fixed Inductor

Solenoid

Multi Pole Double Throw Switch

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Transformer - Auto AdjustableTapped

Foot SwitchNormall O en

Variable Transformer

Foot SwitchNormally Closed

Current Transformer

Electrically Operated Switch* Indicates magnetic coil,motor, orthermal element

Auto Transformer

Multi Pole Single Throw Switch

Fixed Iron Core Coil

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Fixed Air Core Coil

Adjustable Iron Core Coil

Adjustable Air Core Coil

MotorSingle Phase2 Lead

Motor Single Phase 3 Lead

Motor 3 Phase 3 Lead

Motor 3 Phase 6 LeadDual Windings

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Headset

Horn or Siren

Bi-Metallic Thermal Overload

Diode 

Bi-Metallic Thermal Overload

with heater

Microphone 

Headset 

Horno r siren 

Buzzer or bell 

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Push to Test Lamp

Shielded Cable

Push to Test Lamp