A change recently made to article 426-28 of the National Electrical Code will make mineral-insulated (MI), metal-sheathed cables more affordable to install. At this year's annual meeting the National Fire Protection Association/National Electrical Code (NFPA/NEC) passed a revision exempting MI cables from the ground-fault protection normally required for fixed outdoor electric de-icing and snow-melting equipment. MI cables are made entirely of noncombustible material, constructed of copper or copper-resistance conductors, insulated with magnesium oxide and encased in a seamless copper sheath.

Ground-fault protection devices, as required by the 1996 NEC, are usually incompatible with existing panel-boards and thus increase installation material costs by about $300 per circuit. The 1999 NEC revision eliminates the need for ground-fault protection for MI cables.

Ed Slagis, vice president of Delta-Therm Corp., Wauconda, Ill, a manufacturer of electric and hydronic heating systems, says, "The National Electrical Code change recognizes the inherent safety of MI heating systems by making them the only electric systems no longer requiring ground-fault protection measures."

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