location of disconnects

[herve]

I am trying to get clarification regarding the location of disconnects for motors (1 to 10 hp and 460V) in a production facility environment. These motors are either controlled using a variable frequency drive or a simple start/stop switch. I have seen installations where the disconnect feeding the VFD or start/stop switch is remotely located and is capable of being locked in the open position. A contractor is currently telling me that this is not sufficient, but instead that the disconnect must be local to the motor regardless of whether it can be locked in the open position. Can anyone shed some light on this issue.....

 

[don_resqcapt19]

Re: location of disconnects

The exception that permits a remote lockable motor disconnect was changed for the 2002 code. It can only be used where a local disconenct would be impracticable or introduces additional or increased hazards to persons or property or in industrial installations, with written safety procedures, where conditions of maintenance and supervision ensure that only qualified persons service the equipment. This is a change from the 1999 code where a remote lockable disconnect was always permitted. See 430.102(B) and its exceptions.
Don

 

[Len_B]

Re: location of disconnects

I have seen installations where the disconnect feeding the VFD or start/stop switch is remotely located and is capable of being locked in the open position.

Herve, as you state that this is a "production facility", I assume that it is an industrial facility. You are correct, provided that this lockable VFD(controller) disconnect mechanically opens all ungrounded conductors (a lockable start/stop selector switch by itself controlling a contactor coil would not be suitable.) In an industrial facility, where the "controller(in this case, VFD) disconnecting means" is lockable and disconnects all three phase conductors, the normal installation method would be to also use it as the "motor disconnecting means." A separate local disconnect at the motor would not be required due to exceptions allowed under 430.102 (B)(b)

ART 430.102
Under 600v the controller diconnecting means must be within sight(and less than 50 ft per definitions) of the motor controller per 430.102(A). The controller is not required to be in sight from the motor.
The controller disconnecting means shall also be permitted as the motor disconnecting means 430.102(B)

The motor disconnecting means shall be "in sight" of the motor. See exceptions under 430.102(B) that would allow motor disconnecting means to be out of sight of he motor. (a)...impracticle, additional hazards... (b)...industrial...where conditions of maintenance and supervision ...

Either of these exceptions, if applicable, would allow one lockable disconnect to serve as both controller and motor disconnect while not in sight of the motor.

Suggest to your contractor to read 430.102 more thoroughly.

Len

[ March 07, 2003, 04:55 PM: Message edited by: Len_B ]