15 May 12 15:10
My office had a tech seminar with a VFD and Combination Motor Starter Manufacturer today, which sparked some debate within the office. I thought I would take this debate to the online community.
The manufacturer was exhibiting their Motor Starter package, which included a disconnect switch at the top that can be locked off, a motor starter below it, contacts below that, and solid state overload protection below that. The following was the question that sparked the debate.
Can the disconnect switch within the motor starter function as the disconnect switch for the motor starter (considered a controller) or does the NEC require an additional, external disconnect for the motor starter (controller)?
My research has lead me to the following observations.
1. NEC 430.102(A) requires a disconnect for a controller (which covers motor starters and VFDs)
2. NEC 430.102(B) requires a disconnect for a motor
3. NEC 430.102(B)(2) allows the disconnect for the controller to function as the disconnect for the motor if it is within sight of the motor
4. NEC 430.103 allows the disconnecting means to be permitted in the same enclosure with the controller.
So, it seems to me that the disconnect in the controller can function as the disconnecting means for the controller and motor as long as the controller is within sight of the motor. Is this correct?
The other side is that since the disconnect is inside the controller, the lugs will still be "hot" and could still present a shock hazard when performing maintenance on the controller.
All input is welcome!