Send to a Friend View / Add Comments  

Some of you have completed our Online Continuing Education Courses which include video instruction and know this is a very fast way to obtain your CEU credits from the comfort of the chair you're sitting in. For the rest of you we are sending a weekly series of newsletters featuring an instructional page complete with videos.

To view the videos you will need to download the free Real Player Download Real Player plugin for your browser - if you don't already have it. After installing Real Player, you can view the videos by clicking on one of these icons:

  • Click on this icon Hi Res - Cable/DSL if you have a cable or DSL connection.
  • Click on this iconLow Res - Modem if you have a Dial-up connection.

Below is the full course page which includes these videos:

2002 Changes to the NEC®
Article 647 Low Res - Modem Hi Res - Cable/DSL        Page 1 of 1

Qualified Person

A new Article covering the wiring requirements for “Sensitive Electronic Equipment Power or Balanced Power Systems” was added to the 2002 NEC. Balanced power is a separately derived 120V line-to-line, single-phase, 3-wire system with 60V to a grounded neutral conductor on each of two ungrounded conductors. ground from each ungrounded conductor. The purpose of a balanced power system is to reduce objectionable noise in sensitive electronic equipment locations. Its use is restricted to commercial and industrial occupancies that are under close supervision by qualified personnel [647.3]. Figure 647-1

This Article contains specific requirements for:

Panelboards -– 647.4(A)
Overcurrent Protection -– 647.4(A)
Junction Boxes -– 647.4(B)
Color Code Conductors -– 647.4(C)
Voltage Drop -– 647.4(D)
Grounding - 647.6
Receptacles (GFCI protected) - – 647.6
Receptacles (GFCI-protected) – 647.7
Lighting - – 647.8

Author’s Comment: Sensitive Electronic Equipment power systems cannot be installed in dwelling-units.

Intent: Balanced power systems have been permitted in the NEC since 1996, however it was located in Article 530 – Motion Picture and Television Studios and Similar Locations. Locations, therefore its use was limited to these applications. By locating the requirements in a separate Article, its use can be greatly expanded, but its use is limited to commercial or industrial occupancies.

Figure 647-1
Click on Image to Enlarge

Copyright © 2004 Mike Holt Enterprises,Inc.
1-888-NEC-CODE (1-888-632-2633)