The revision of Art. 426-28 of the 1999 NEC exempts mineral-insulated (MI) metal-sheathed cables embedded in noncombustible mediums (such as cement or asphalt) from ground-fault protection required for fixed outdoor electric deicing and snow melting equipment. Ground-fault protection devices, as the 1996 NEC requires, are incompatible with existing panelboards and increase material costs by $300 per circuit.
“MI cables are now more cost efficient,” says Ed Slagis, vice president of Delta-Therm Corporation. “The code change recognizes the inherent safety of MI heating systems by making them the only electric systems no longer requiring ground-fault protection measures.”
Made of noncombustible material and constructed of copper or copper resistance conductors, MI cables are insulated with magnesium oxide and encased in a seamless copper sheath. For more than 30 years, Slagis’ company has specialized in the design and manufacture of electric and hydraulic heating systems as well as UL-listed controls and monitor panels.
