169.667—Switchboards.
(a)
Each switchboard must be in as dry a location as praticable, accessible, protected from inadvertent entry, and adequately ventilated. All uninsulated current carrying parts must be mounted on nonabsorbent, noncombustible, high dielectric insulating material.
(c)
Each ungrounded conductor of a circuit must have at the point of attachment to the power source either—