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[ Challenge Yourself - Take Our FREE Grounding vs. Bonding Exam ]

Grounding versus Bonding — 2005 NEC®
PART I   Hi Res - Cable/DSL        Page 2 of 13

Sections

250.2 Definitions

Author’s Comment: Why is grounding so difficult to understand? One reason is because many do not understand the definition of many important terms. So before we get too deep into this subject, let’s review a few important definitions contained in Articles 100 and 250.

Bonding [100]. The permanent joining of metal parts together to form an electrically conductive path that has the capacity to conduct safely any fault current likely to be imposed on it. Figure 250–1

Author’s Comment: Bonding is accomplished by the use of conductors, metallic raceways, connectors, couplings, metallic-sheathed cables with fittings, and other devices recognized for this purpose [250.118].

Bonding Jumper [100]. A conductor properly sized in accordance with Article 250 that ensures electrical conductivity between metal parts of the electrical installation. Figure 250–2

Effective Ground-Fault Current Path [250.2]. An intentionally constructed, permanent, low-impedance conductive path designed to carry fault current from the point of a ground fault on a wiring system to the electrical supply source. Figure 250–3

The effective ground-fault current path is intended to help remove dangerous voltage from a ground fault by opening the circuit overcurrent protective device. Figure 250–4

Equipment Grounding Conductor [100]. The low-impedance fault-current path used to bond metal parts of electrical equipment, raceways, and enclosures to the effective ground-fault-current path at service equipment or the source of a separately derived system.

Author’s Comment: BThe purpose of the equipment grounding (bonding) conductor is to provide the low-impedance fault-current path to the electrical supply source to facilitate the operation of circuit overcurrent protection devices in order to remove dangerous ground-fault voltage on conductive parts [250.4(A)(3)]. Fault current returns to the power supply (source), not the earth!

According to 250.118, the equipment grounding (bonding) conductor must be one or a combination of the following. Figure 250–5

  • Wire Type. A bare or insulated conductor [250.118(1)]
  • Rigid Metal Conduit [250.118(2)]
  • Intermediate Metal Conduit [250.118(3)]
  • Electrical Metallic Tubing [250.118(4)]
  • Listed Flexible Metal Conduit as limited by 250.118(5)
  • Listed Liquidtight Flexible Metal Conduit as limited by 250.118(6)
  • Armor of Type AC cable [250.118(8)]
  • Armor of Type MC cable as limited by 250.118(10)
  • Metallic Cable Trays as limited by 250.118(11) and 392.7
  • Electrically continuous metal raceways listed for grounding [250.118(13)]
  • Surface Metal Raceways listed for grounding [250.118(14)]


Figure 250–1
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Figure 250–2
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Figure 250–3
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Figure 250–4
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Figure 250–5
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04. Grounding versus Bonding Library - DVDs
Grounding and bonding problems are at epidemic levels. Surveys repeatedly show a high percentage of power quality problems are due to poor grounding and bonding. Electrical theory has been applied to this difficult to understand Article, making it easier for students to grasp the concepts of grounding and bonding. Additionally, Mike has color coded the graphics so you can easily differentiate between grounding and bonding. For a limited time, you can order the Entire Grounding versus Bonding Library including the textbook, 2 videos, MP3 Audio CD and the Online Program for this great price. You save over $200!

Product Code: 05GBDVD
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