Electrical Symbols – Contacts, Switches, Contactors and Relays

Symbol

Name

Description 

Relay Contact Relay Contact Shown with relay in de-energized or in reset position. (Show relay coil designation near contact.)
Timing Relay Contact Timing Relay Contact TDC indicates contact closes at end of timing period. TDO contact opens at end of timing period.
Coil Coil

Relay, , circuit breaker, solenoid etc.

(Show device designation, X1)

Coil Timing Relay – TDPU indicates timing period starts when coil is energized. TDDO indicates timing period starts when coil is de-energized.
Latching Relay or Mechanically Contractor   Latching Relay or Mechanically    O=Operate; R=reset; TC=trip coil; CC=closing coil. (Coils may be seperated on diagram)
Knife Switch Knife Switch If shown closed, terminals must be added.
Switch General Switch – General Single pole, single throw.
Switch Switch One pole of multi-pole switch shown. Other poles shown elsewhere.
Pushbutton Pushbutton Momentary or spring return. Single Circuit(make)
Pushbutton Pushbutton Momentary or spring return. Single Circuit(break)
Pushbutton Pushbutton Momentary or spring return. Two Circuit.
Pushbutton Pushbutton Maintained, two circuit.
Pushbutton Pushbutton Maintained, single circuit.
Selector Switch Selector Switch Two position, maintained designate position shown; ie. A=Auto;
Selector Switch Selector Switch

Three position, SR indicates spring return from position so labeled.

“TRIP-NORMAL-CLOSE position shown.

Limit Switch Limit Switch Normally open – not applicable for Motor Operated Valves and Solenoid Valves.
Limit Switch Limit Switch Normall closed – not applicable for Motor Operated Valves and Solenoid Valves.
Used with other symbols to indicate device is adjustable   Used with other symbols to indicate device is adjustable
Polarity Markings Polarity Markings Direct current.
Instantaneous Polarity Markings Instantaneous Polarity Markings  
3-phase, 3-wire, delta 3-phase, 3-wire, delta  
3-phase, 3-wire, open delta grounded 3-phase, 3-wire, open delta grounded  
3-phase, 3-wire, wye 3-phase, 3-wire, wye  
3-phase, 3-wire, wye grounded neutral 3-phase, 3-wire, wye grounded neutral  
3-phase, 3-wire, zigzag 3-phase, 3-wire, zigzag  
3-phase, 3 wire zigzag, grounded neutral 3-phase, 3 wire zigzag, grounded neutral  
Connection to earth ground Connection to earth ground may be plant grounding system
Connection to chassis or frame Connection to chassis or frame  
Terminal Terminal may be added to any of the following symbols at connection points.
Short circuits  Short circuits  (not a fault)
Terminal Terminal designates termination of field run cables to main control board, main control board termination cabinet or emergency power board termination cabinet.
Flow Switch  Flow Switch  Closes on increase in flow at value shown.
Flow Switch Flow Switch Opens on increase in flow at value shown.
Flow Switch Flow Switch Closes on decrease in fow at value shown.
Flow Switch Flow Switch Opens on decrease in flow at value shown.
Liquid Level Switch Liquid Level Switch Opens on rising level (Closes on low level)
Liquid Level Switch Liquid Level Switch Closes on rising level (Opens on low level)
Pressure or Vacum Switch Pressure or Vacum Switch Closes on rising pressure switch.
Pressure or Vacum Switch Pressure or Vacum Switch Opens on rising pressure (Closes on increase in vacuum)
Temprature Switch Temprature Switch Closes on increasing tmp.
Torque Switch  Torque Switch  Opens on high torque.
Transductor Transductor Control winding shown with 5 loops. Power winding shown with 3 loops.
Transformer Transformer General, two winding
Autotransformer Autotransformer General
Transformer Transformer General, three winding
Current Transformer Current Transformer number represents quantity
Bushing Type Current Transformator Bushing Type Current Transformator  
Potential Transformer  Potential Transformer   Number represents quantity 
Fuse Fuse General
High Voltage Primary Fuse Cutout High Voltage Primary Fuse Cutout  
Lighting Arrester  Lighting Arrester  General Gap Type
Lighting Arrester  Lighting Arrester  Valve or film type
Circuit Breaker  Circuit Breaker  General
Power Circuit Breaker  Power Circuit Breaker  Show location of operating mechanism
Circuit Breaker Circuit Breaker 3-pole with magnetic – overload device in each pole.
Circuit Breaker Circuit Breaker 3-pole, drawout type (Used in metal clad switchgear groups)

 

 

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