gr33n
Member
- Location
- Columbia, MD
Hello world. Perhaps this question has been answered before. I would much appreciate any help on this issue or be referred to a NEC article that may help me define the following scenario.
A custom built MCC with a 250A service (and main disconnect) was designed to power various motor loads. As it usually happens, the scope of the project changed and an extra 100HP motor was added, elevating the service to 350A. The 100HP VFD for this new motor had to be mounted externally but adjacent to the MCC given its size. However the client says that he doesn't have a switchboard that can accommodate 350A, but can however supply separate power for the external 100HP VFD from a different switchboard.
Each VFD inside the original MCC has its own branch fused disconnect switch.
Question: Can the client install a fused switch disconnect for this 100HP VFD inside the original MCC although its power would come from a different source and even though the main disconnect switch of the MCC won't power it down? I am hesitant to have a branch inside the MCC that won't be powered off when the MCC's main disconnect is down.
Any NEC articles preventing this? I suppose that they can feed separate power to this new 100HP load but with a complete independent fused disconnect switch box installed also outside the existing MCC.
Any thoughts? Thanks!
A custom built MCC with a 250A service (and main disconnect) was designed to power various motor loads. As it usually happens, the scope of the project changed and an extra 100HP motor was added, elevating the service to 350A. The 100HP VFD for this new motor had to be mounted externally but adjacent to the MCC given its size. However the client says that he doesn't have a switchboard that can accommodate 350A, but can however supply separate power for the external 100HP VFD from a different switchboard.
Each VFD inside the original MCC has its own branch fused disconnect switch.
Question: Can the client install a fused switch disconnect for this 100HP VFD inside the original MCC although its power would come from a different source and even though the main disconnect switch of the MCC won't power it down? I am hesitant to have a branch inside the MCC that won't be powered off when the MCC's main disconnect is down.
Any NEC articles preventing this? I suppose that they can feed separate power to this new 100HP load but with a complete independent fused disconnect switch box installed also outside the existing MCC.
Any thoughts? Thanks!
