Section 39.212. Mechanical and thermal protection

(a) If exposed to mechanical injury, suitable casing, armor, or other means shall be employed to prevent injury or disturbances to conductors, their insulation, or supports. Conductors used as meter loops shall be substantially supported clear of objects other than their insulating supports, and separated from each other, or shall be in approved conduit or substantial noncombustible, nonabsorptive casings.

(b) If conductors with combustible insulating coverings are closely grouped, as sometimes on the rear of switchboards or in cableways, they shall have a substantial noncombustible outer covering. Conductors in very hot locations shall have a noncombustible insulating covering.

(c) Bare conductors shall be used only for switchboard, panelboard, or storage battery connections; or for electrolytic, low voltage furnace, or low voltage welding circuit, and similar connections; or for trolley wires, third rails, and other contact conductor, and parts at different potentials. Such bare conductors shall be fixed at adequate separations by the use of suitable supports. Except at the point where a permanent ground connection is made such conductors within buildings shall be kept insulated from the ground. Bare conductors shall not be used where inflammable gases or explosives are liable to exist in large quantities. Reference should also be made to § § 39.199 and 39.213 (relating to guarding or isolating live parts; isolating or guarding).