Electrical Thumb Rules You MUST Follow (Part 6)PostedNOV 29 2013byJIGUPARMARinENERGY AND POWERwith2 COMMENTS

Electrical Thumb Rules You MUST Follow, Part 6 (On photo: View in the Transformer Room in the underground area during White House renovation on March 26, 1952 - via trumanlibrary.org)

Continued from:Electrical Thumb Rules You MUST Follow (Part 5)

12 electrical thumb rules to follow:1. Transformer earthing wire / Strip size2. Motor earthing wire / Strip size3. Panel earthing wire / Strip size4. Electrical equipment earthing5. Earthing wire (As per BS 7671)6. Area for transformer room: (As per NBC-2005)7. Span of transmission line (Central electricity authority)8. Max. lock rotor amp for 1-phase 230V motor (NEMA)9. Three phase motor code (NEMA)10. Service factor of motor11. Type of contactor12. Contactor coil1. Transformer earthing wire / Strip sizeSize of T.C or DGBody EarthingNeutral Earthing

55 KW506 mm GI Strip

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3. Panel earthing wire / Strip sizeType of PanelBody Earthing

Lighting & Local Panel256 mm GI Strip

Control & Relay Panel256 mm GI Strip

D.G & Exciter Panel506 mm GI Strip

D.G & T/C Neutral506 mm Cu Strip

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4. Electrical equipment earthingEquipmentBody Earthing

LA (5KA,9KA)253 mm Cu Strip

HT Switchgear506 mm GI Strip

Structure506 mm GI Strip

Cable Tray506 mm GI Strip

Fence / Rail Gate506 mm GI Strip

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5. Earthing wire (As per BS 7671)Cross Section Area of Phase, Neutral Conductor(S) mm2Minimum Cross Section area of Earthing Conductor (mm2)

S 200 HP11.1511111

Go back to Rules11. Type of contactorTypeApplication

AC1Non Inductive Load or Slightly Inductive Load

AC2Slip Ring Motor, Starting, Switching OFF

AC3Squirrel Cage Motor

AC4,AC5,AC5a, AC5b,AC6aRapid Start & Rapid Stop

AC 5aAuxiliary Control circuit

AC 5bElectrical discharge Lamp

AC 6aElectrical Incandescent Lamp

AC 6bTransformer Switching

AC 7aSwitching of Capacitor Bank

AC 7bSlightly Inductive Load in Household

AC 5aMotor Load in Household

AC 8aHermetic refrigerant compressor motor with Manual Reset O/L Relay

AC 8bHermetic refrigerant compressor motor with Automatic Reset O/L Relay

AC 12Control of Resistive Load & Solid State Load

AC 13Control of Resistive Load & Solid State Load with Transformer Isolation

AC 14Control of small Electro Magnetic Load (72 VA)

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12. Contactor coilCoil VoltageSuffix

24 VoltT

48 VoltW

110 to 127 VoltA

220 to 240 VoltB

277 VoltH

380 to 415 VoltL

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