The list of abbreviations used in a set of engineering drawings varies from office to office. Be sure to check the front section of the drawing set for the abbreviations used within.

#Number
ΩOhm
ΦPhase
AAmperes
ACAlternating Current
A/CAir Conditioning
AFCIArc Fault Circuit Interrupter
AHUAir Handling Unit
AICAmpere Interrupting Capacity
ALAluminum
ATSAutomatic Transfer Switch
ATCAutomatic Temperature Control
AWGAmerican Wire Gauge
BTUBritish Thermal Units
CConduit
CATVCable Television or Community Antennae Television
CBCritical Branch
C/BCircuit Breaker
CBMCertified Ballast Manufacturer
CCTCircuit (also: CIR, CKT)
CCTVClosed Circuit Television
CDCandela
CIRCircuit (also: CCT, CKT)
CKTCircuit (also: CCT, CIR)
CLFCurrent Limiting Fuse
CPTControl Power Transformer
CTCurrent Transformer
CUCopper
dBDecibel
DCDirect Current
DIADiameter
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EBEquipment Branch
ECElectrical Code or Electrical Contractor
EFExhaust Fan
ELEVElevator
EMEmergency
EMTElectrical Metallic Tubing
EPEmergency Power
EPOEmergency Power Off (Button or Switch)
EWCElectric Water Cooler
FFuse
FAFire Alarm
FAAFire Alarm Annunciator
FLAFull Load Amperes
FMCFlexible Metal Conduit
GGround
GFCI, GFIGround Fault Circuit Interrupter
GNDGround
GRMCGalvanized Rigid Metal Conduit
HOAHand-Off-Automatic Switch
HVACHeating, Ventilation, Air Conditioning
HZHertz
IEEEInstitute of Electrical and Electronic Engineers
IGIsolated Ground
IMCIntermediate Metal Conduit
INTInterlock
KCMILThousand Circular Mils
KVAKilovolt-Amperes
KVARKilovolt-Amperes Reactive
LFMCLiquid Tight Flexible Metal Conduit
LTGLighting
LRALock Rotor Amps
MCMetal Clad Cable
MCBMain Circuit Breaker
MCCMotor Control Center
MCPMotor Circuit Protection
MIMineral Insulated
MLOMain Lugs Only
MWMegawatt
NCNormally Closed
NECNational Electrical Code
NEMANational Electrical Manufacturers Association
NFPANational Fire Protection Association
NLNight Light
NONormally Open or Number
PPole
PBPush Button or Panic Button or Pull Box
PNLPanel
PWRPower
PTPotential Transformer
QTYQuantity
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REQRequired
RMCRigid Metal Conduit
RMSRoot Mean Squared
RNCRigid Non-Metallic Conduit
RTSRemote Test Station
RTURoof Top Unit
SPSpare
STShunt Trip
SWSwitch
SYMSymmetrical
TELTelephone
TGBTelecommunications Grounding Busbar
TMCBThermal Magnetic Circuit Breaker
UGUnder Ground
ULUnderwriters Laboratory
VVolt
VAVolt-Ampere
VTVoltage Transformer
WWatt or Wire
WHWater Heater
WPWeather Proof
XFMRTransformer
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