The fan-forced evaporator unit in the display case was not properly secured, and thus was able to vibrate constantly while in operation; these vibrations were carried along the copper refrigerant lines, causing the pipes to rub against the electrical conduit in the wall soffit and make them vibrate as well. Galvanic corrosion occurred, in which the copper refrigerant pipes were in physical contact with the aluminum electrical conduit, causing the conduit to erode over time. Galvanic corrosion and vibration – as well as jagged edges and stretched wires resulting from poor workmanship during the installation – eventually resulted in the electrical wires inside the conduit missing chunks of their plastic insulation. The conduit was rendered un-grounded (there was no separate ground wire; the metal conduit itself was designed to function as the ground, so the disintegration of the conduit rendered the system un-grounded).