Grounding & Bounding. 1. Bonded Connected to establish electrical continuity and conductivity.

Transcription

1 & Bounding Article 100 Definitions 1. Bonded Connected to establish electrical continuity and conductivity. 2. Raceway fittings bonds sections of raceway Bonding jumper bonds receptacles to boxes Threaded entry bonds raceway to box B Main Bonding Jumper and System Bonding Jumper Bonds equipment ground to service neutral 1. At service disconnecting means 2. Can be conductor, screw, or strap (250.28) 4. Ground (the earth) Grounded means connected to earth or some conductive body that extends the ground connection to earth (structural steel) Article System & equipment grounding 2. Location of grounding connections 3. Types of electrodes 4. Sizing of grounding and bonding conductors 5. Methods of grounding and bonding Definition - Supply Side Bonding Jumper - Installed on supply side of the service equipment and between source of a separately derived system and the first disconnecting means. Effective Ground Fault Current- A path to open over current device.

2 Ground fault Unintentional electrical connection between hot and or neutral conductor to equipment grounding conductor,metal enclosures, raceway, equipment or earth Informational Note Ground fault current path (electrons trying to get back to source not earth or ground) General requirements for grounding or bonding 250.4A1 Electrical systems are grounded to limit the voltage imposed by lightning (high voltage surges also primary to secondary voltage contact) and to stabilize the voltage to earth A2 Equipment grounding metal parts of electrical equipment are grounded to earth to reduce voltage on parts from lightning so as to prevent fires from arcs within the building. WARNING Failure to ground these metal parts can result in a possible fire and or electric shock. Equipment bonding objective is to quickly remove ground fault voltage by opening the circuit protection device A4 Bonding electrically conductive materials 250.4A5 Effective ground fault current path (earth is not an effective ground fault current path) 250.4B1 electrical equipment B3 Bonding of electrical equipment

3 B4 Path of fault current Objectionable currents (ground and neutral bonded after service equipment, electrons travel back to source on all paths) B Stopping objectionable currents Connection of grounding and bonding equipment Systems 50v or more must be grounded. Systems less than 50v supplied by a service larger than 150 volts must be grounded on the secondary side D1 System bonding size Table (C)1(Secondary side) D Info. Note1 Not separately derived system C - Grounded Conductor brought to the service A Separately derived system A1 Unspliced System Bonding Jumper - Installed at the same location the GEC TERMINATES TO THE NEUTRAL A1b Installed grounding and electrode conductor at neutral point to a grounding electrode A5 Electrode Conductor, Single Separately Derived System - shall be sized from table (C)1 from the ungrounded conductors of the derived system.

4 250.30C Outdoor Sources (new grounding requirements) A Separate Buildings supplied by a feeder A Exception electrode conductor not needed electrode system All grounding electrodes present must be bonded together 1. Metal water pipe 10 long in contact with earth 2. Metal frame of building if 10 is in contact with earth 3. Metal frame connected to ground rod 4. Concrete encased electrode (rebar stub) Underground systems A2 Metal Frames In-Ground Support Structures Electrode installation requirements A1 Underground water pipe supplementary ground rod (250.3D2) Auxiliary electrode (use this if required by manufacturer or engineer) (can not eliminate equipment ground) Lightning Protection Electrode B Securing and Protection of GEC D1 GEC Taps Multiple Disconnects Table Size grounding electrode conductor Largest conductor required for a rod electrode is a #6 Ufer ground largest conductor required #4

5 250.68A Termination of grounding electrode conductor C GEC and Bonding Jumpers Connections C2 Metal Frame of a Structure used as a Bonding Jumper Service Raceways and Enclosures B Methods of bonding at Service Intersystem Bonding Termination Bonding other enclosures (listed reducing washers) Bonding of 277v or 480v A GROUNDED CONDUCTOR, BONDING CONDUCTORS AND JUMPERS C SIZE: Supply Side Bonding Jumper (table (C)1 &12.5%rule) Bonding of water piping including sprinkler system (csst gas pipe) C Structural steel D1 Exception 2 Bonding jumper not required if water pipe is bonded to metal frame being used as a grounding electrode Lightning protection grounding electrode must be bonded to building grounding electrode system EMT or other metal conduit serving as equipment grounding conductor i Transformer secondary up to 50v not required to be bonded If cord and plug connected non-current carrying metal parts must have grounding connection. & Bonding

6 Types of Equipment grounding conductors Identification of grounding conductor Use Of Equipment Conductor & Exception Equipment grounding conductor sizing from T B Equipment grounding conductor must be contained within the same raceway cable or trench (exception for motors 6 ) Equipment grounding conductors passing through a box need not be connected to box but. If a slice is made you must bond equipment-grounding conductor to the box H6 Equipment Bonding Jumper in Parallel of equipment in Patient Health care areas Equipotential Plane AG BUILDINGS 547.5(F) Separate Equipment Conductor (NOT REQUIRED TO BE COPPER UNDER 2014 NEC) Equipotential planes and bonding of equipment Equipotential Bonding permanently installed pools (pool equipment grounding) Equipotential Bonding Hydromassage Tub

7 & Bonding