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Illustrated Changes to the NEC, 2002 Edition - Part 2

Article 647

Sensitive Electronic Equipment

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.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.

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