If branch circuits from a 120/240 volt panel are run in the same conduit as circuits from a 277/480 volt panel, is it a Code violation?

Running branch circuits from both a 120/240 volt panel and a 277/480 volt panel in the same conduit is not a code violation as long as certain conditions are satisfied. The National Electrical Code (NEC) permits the mixing of circuits with different voltage levels in the same conduit, given that they are properly insulated and meet the necessary requirements for spacing and separation.

In the scenario presented, as long as the circuits are appropriately rated and meet the NEC specifications for conductor insulation types, it is permissible to run them together. The voltage difference means that proper care must be taken to ensure that there is no risk of electrical interference, overheating, or safety hazards due to the voltage disparity. Additionally, we must ensure that the conduit is adequately sized to handle the heat generated based on the current-carrying conductors' cumulative ampacity.

Understanding these code provisions helps electrical professionals maintain safe practices while increasing flexibility in circuit design and installation. Therefore, declaring that this situation is a code violation would be incorrect, confirming that the correct answer is that it is not a violation under the stated conditions.