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2002 Changes to the NEC®
PART I   Hi Res - Cable/DSL        Page 9 of 13

Sections

250.6 Objectionable Current Continued

Wiring Errors

Objectionable current will flow on metal parts when the grounded neutral conductor from one system is connected to a circuit of a different system. Figure 250–32

Objectionable current will flow on metal parts when the equipment grounding (bonding) conductor is used as a grounded neutral conductor.

Example: A 240V time-clock motor is replaced with a 120V time-clock motor and the equipment grounding (bonding) conductor is used to feed one side of the 120V time clock. Another example is a 120V water filter wired to a 240V well-pump motor circuit, with the equipment grounding (bonding) conductor used for the neutral. Figure 250–33

Using the equipment grounding (bonding) conductor for the neutral is also seen in ceiling fan installations where the bare equipment grounding (bonding) conductor is used as a neutral and the white wire is used as the switch leg for the light, or where a receptacle is added to a switch outlet that doesn’t have a neutral conductor. Figure 250–34

Author’s Comment: Neutral currents always flow on a community metal underground water piping system because the grounded neutral conductor from each service is grounded to the underground metal water pipe. Figure 250–35

Dangers of Objectionable Current

Objectionable current on metal parts can cause electric shock, fires, and improper operation of sensitive electronic equipment and circuit-protection devices.

Shock Hazard. When objectionable current flows on metal parts, electric shock and even death can occur (ventricular fibrillation) from elevated voltage on the metal parts. Figure 250–36


Figure 250–32
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Figure 250–33
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Figure 250–34
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Figure 250–35
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Figure 250–36
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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
ISBN: N/A
MultiMedia: Tape & CDROM & DVD

DVD/CD Return Policy: Unopened sealed DVD's or CD's may be returned within 10 days and we will credit your credit card or issue a refund for the price of the item(s). Opened items may not be returned unless they arrive defective.

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