Grounding Metal Boxes Nec Code

The purpose statement of the nec section 90 1 a states the purpose of this code is the practical safeguarding of persons and property from hazards arising from the use of electricity in other words it all comes back to protecting people and property from the inherent hazards of using electricity.

Grounding metal boxes nec code. 250 148 continuity and attachment of equipment grounding conductors to boxes. Lightning systems must be bonded per nec 250 106 250 4 a 1 250 4 b 1 and nfpa 780 section 4 14. Have a local inspector approve your wiring plans before you begin work. Grounding with conduit.

In some installations using metal conduit the raceway the conduit boxes and connectors serve as the ground for the circuit. This is directly evident when we take a look at the grounding and bonding requirements. Wiring in pvc conduit must have at least 18 inches of cover. For instance one may allow plastic boxes while another requires metal boxes.

The national electrical code defines a wet location as an area that is subject to saturation with water or other liquids and unprotected locations exposed to the weather. Wiring buried inside rigid metal rmc or intermediate metal imc conduit must have at least 6 inches of earth cover. The national electric code has another definition for damp locations that is more subjective but if you think the receptacle is going to get wet use an in use. It s not unusual for adjacent towns to have very different codes.

This refers to the metal race ways metal cables boxes panelboards nipples transformers. Local building departments often modify the nec and you must satisfy those local codes. National electrical codes nec 250 5 grounding and bonding grounding and bonding electrodes include a metal underground water pipe in direct contact with earth for 10 feet or more a metal frame of a building or structure a concrete encased electrode or a ground ring nec 250 28 grounding and bonding grounding and bonding a main bonding jumper or the green bonding screw provided by the panel. Backfill surrounding conduit or cables must be smooth granular material without rocks.

The circuit equipment grounding conductor for an isolated ground receptacle installed in accordance with 250 146 d isn t required to terminate to a metal box. We also see hesitation when people are instructed to bond their gas pipes to the grounding and lightning systems nec 250 104 b 250 52 b 1 and nfpa 54 section 7 13 as well. Where circuit conductors are spliced within a box or terminated on equipment within or supported by a box any equipment grounding conductor s associated with those circuit conductors shall be connected within the box or to the box with devices suitable for the use in accordance with 250 148 a.