bgreenier
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- Proctorsville Vermont USA
what are the NEC requirements for disconnect needs for field mounted motor VFDs<
what are the NEC requirements for disconnect needs for field mounted motor VFDs<
The VFD is a motor controller and must have a line side disconnect within sight from the VFD. The motor also requires a disconnect within sight from the motor. If the VFD disconnect is also within sight from the motor you don't need a second disconnect. If the VFD disconnect is not within sight from the motor, you will need a second disconnect within sight from the motor, unless you installation meets one of the exceptions. 430.102
The VFD is a motor controller and must have a line side disconnect within sight from the VFD. The motor also requires a disconnect within sight from the motor. If the VFD disconnect is also within sight from the motor you don't need a second disconnect. If the VFD disconnect is not within sight from the motor, you will need a second disconnect within sight from the motor, unless you installation meets one of the exceptions. 430.102
How is it you come to the conclusion this is not enforceable?:?Good explanation.
Though not enforceable part of code, I want to point out the informational note after that section mentions adjustable speed drives as being a potential reason to meet the exception. I would guess most AHJ would allow such exception to be used in this case.
Originally Posted by don_resqcapt19
The VFD is a motor controller and must have a line side disconnect within sight from the VFD. The motor also requires a disconnect within sight from the motor. If the VFD disconnect is also within sight from the motor you don't need a second disconnect. If the VFD disconnect is not within sight from the motor, you will need a second disconnect within sight from the motor, unless you installation meets one of the exceptions. 430.102
Originally Posted by kwired
Good explanation.
Though not enforceable part of code, I want to point out the informational note after that section mentions adjustable speed drives as being a potential reason to meet the exception. I would guess most AHJ would allow such exception to be used in this case.
How is it you come to the conclusion this is not enforceable?:?
The informational note is not discussing the disconnect for the controller. It is discussing using the controller disconnect for the motor disconnect.
However, if you are discussing only that part about not necessarily needing a motor disconnect if there is a VFD, then, I would point out, the informational note is the non-enforceable part.
ice
What is your point, what you said is pretty much what I meant ...
I read your post several times and I didn't get that. My bad.
ice
Thank youI'll let you go this time
For my work, the exceptions are well enough defined. I have only put in one disconnect "in sight of the motor" in the last 45 years. And that one was our choice - for maintenance convenience.... All I was mentioning was that the exceptions allow for not having a disconnect at the motor for certain conditions but those conditions are not really that defined in the actual code. ..
Thank you
For my work, the exceptions are well enough defined. I have only put in one disconnect "in sight of the motor" in the last 45 years. And that one was our choice - for maintenance convenience.
But I don't do commercial buildings either. Maybe the exceptions are not well defined for those applications - that I don't know.
ice
bgreenier,
Just a word of advice. If you do install a disconnect between the VFD and the motor, you should interlock the disconnect to the VFD so that if the VFD were running and someone throws the disconnect the VFD stops. I have personally seen VFDs grenade when they are outputting nearly full voltage and the disconnect is thrown in. A smaller drive may be ok, but larger drives, especially large drives with long motor leads have a tendency to blow the caps.