NEC 300.34 states that "Conductors of different systems, circuits, and voltages shall not be placed in the same wireway unless separated by a solid barrier."NEC 300.20 states that "Conductors shall be protected against physical damage."In your case, you have 108-#8 THHN cu wires, 6-#8 THHN cu gnd(480v), 18-#10 THHN cu, and 6-#10 THHN cu gnd (120v control) in a 6" x 6" metalic wireway. This is a violation of NEC 300.34 because the wires of different systems and voltages are not separated by a solid barrier. It is also a violation of NEC 300.20 because the wires are not protected against physical damage at the 90-degree bend.The wires are burning up inside the wireway because of the excessive heat that is being generated by the high current draw of the heating coil contactors and controls. The wires are not able to dissipate the heat because they are tightly bundled together in the wireway. The 90-degree bend in the wireway also creates a point of stress on the wires, which can cause them to break.

You must correct this installation immediately to prevent a fire hazard. You can do this by separating the wires of different systems and voltages by a solid barrier, and by providing protection against physical damage at the 90-degree bend. Flag for review