DC System Grounding Installation | Grounding & Earthing System

This article is about DC System Grounding Installation, Checklist & Requirements of Grounding Earthing System as per International Codes and standards for Commercial Buildings, Plants and Refinery Projects.

DC System Grounding Installation | Grounding Earthing System

1. A 2- wire, dc system supplying premises wiring and operating at greater than 50 volts but not greater than 300 volts shall be grounded.
2. Exception No. 1: A system equipped with a ground detector and supplying only industrial equipment in limited areas shall not be required to be grounded.
3. Exception No. 2: A rectifier-derived dc system supplied from an ac system complying with NEC 250.20 shall not be required to be grounded.
4. Exception No. 3: Direct-current fire alarm circuits having a maximum current of 0.030 amperes as specified in NEC Article 760, Part III, shall not be required to be grounded. [NEC 250.162 (A)]
5. The neutral conductor of all 3-wire, dc systems supplying premises wiring shall be grounded. [NEC Art. 250.162 (B)]
6. DC systems to be grounded and supplied from an off-premises source shall have the grounding connection made at one or more supply stations. A grounding connection shall not be made at individual services or at any point on the premises wiring. [NEC Art. 250.164 (A)]
7. DC systems to be grounded and supplied from an on-premises source shall have the grounding connection made at one of the following: (1) The source (2) The first system disconnect means or overcurrent device (3) By other means that accomplish equivalent system protection and that utilize equipment listed and identified for the use (NFPA 70 NEC Art. 250.164 (B))
8. The size of the grounding electrode conductor for a dc system consisting of a 3-wire balancer set or a balancer winding with overcurrent protection as provided in NEC 445.12 (D) shall be not smaller than the neutral conductor and not smaller than 8 AWG copper or 6AWG aluminum. [NEC Art. 250.166 (A)]
9. The size of the grounding electrode conductor for a dc system other than as in NEC 250.166 (A) above, shall be not smaller than the largest conductor supplied by the system, and not smaller than 8 AWG copper or 6 AWG aluminum. [NEC Art. 250.166 (B)]
10. The size of the grounding electrode conductor that is the sole connection to rod, pipe, or plate grounding electrodes shall not be required to be larger than 6 AWG copper wire or 4 AWG aluminum wire. [NEC Art. 250.166 (C )]
11. The size of the grounding electrode conductor that is the sole connection to concrete encased electrodes shall not be required to be larger than 4 AWG copper wire. [NEC 250.166 (D)]
12. The size of the grounding electrode conductor that is the sole connection to a ground ring shall not be required to be larger than the conductor used for the ground ring. [NEC 250.166 (E)]
13. The size of the DC bonding jumper shall not be smaller than the system grounding conductor. (NEC 250.168)
14. Except as otherwise permitted in NEC 250.34 for portable and vehicle -mounted generators, an ungrounded dc separately derived system supplied from a stand-alone power source ( such as an engine- generator set) shall have a grounding electrode conductor connected to an electrode that complies with NEC 250 Part III to provide for grounding of metal enclosures, raceways, cable, and exposed non-current-carrying metal parts of the equipment . The grounding electrode conductor connection shall be to the metal enclosure at any point on the separately derived system from the source to the first system disconnect means or overcurrent device, or it shall be made at the source of the separately derived system that has no disconnecting means or overcurrent devices. The size of the grounding electrode conductor shall be in accordance with NEC 250. 166 above.
    (NEC 250.169)”
15. The color code for battery rack and other equipment grounding conductors for Ungrounded Systems for Industrial Facilities shall be green.
16. The color code for battery rack and other equipment grounding conductors for Grounded Systems for Special Applications ( i.e., Negative or Positive Grounded Conductors Systems) shall be green, or green with yellow stripes.

International Standard and Codes for DC System Grounding

1. Non-Hazardous Indoor Enclosures, Installation and Pre-Commissioning
2. Boxes, Enclosures, and Accessories Materials Selection & Requirements
3. SAES-J-902 — Electrical Systems for Instrumentation.
4. SAES-J-601 — Emergency Shutdown and Isolation Systems.
5. Use of Grounding In Electrical System