Article 430.102(A) - Disconnector within Sight

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Re: Article 430.102(A) - Disconnector within Sight

Friebel,
Your quote regarding the stop start pushbutton station serving as the controller disconnecting means is not entirely accurate. If I wanted to work on the controller itself I could not isolate the load side of the start-stop contacts using the pushbutton station since 480 Volt power would still be available to the open and close contacts via the power supply from the MCC.
Given that you would not do this knowing you could go to the MCC and put the MCCB in the open position and lock it out, then go work on the controller. This is the issue I have with this article, as trained operators would never get into this situation, so I am still asking for someone show me the reason as to why this is.

[ April 05, 2004, 04:10 PM: Message edited by: wjrez ]
 
Re: Article 430.102(A) - Disconnector within Sight

This specific topic (disconnects for MOVs) received much debate in Code Making Panel 11 during the 2002 cycle.

Essentially, a disconnect, "in sight from the CONTROLLER," is the fundamental requirement. The controller for the MOV is usually an integral part of the MOV; therefore the disconnect must be in sight from the MOV. The ability to lock it is irrelevant for MOVs below 600V.

It is also important to note that FPN 1 DOES NOT NESSECARILY EXEMPT any of the ?additional hazards? listed unless a specific additional hazard can be demonstrated. For example, per 430.108 through 430.110 every switch in the circuit must essentially be ?motor rated.? The list of switches and disconnects given generally meets that requirement, unless the motor is over 100hp AC or 40hp DC. (The FPN doesn?t mention DC motors at all).

The reason is that these switches may be called upon to do more than simply isolate the motor circuit, they may be called upon to interrupt it (possibly locked rotor) ? that?s where the ?additional hazard? comes in.

Push buttons are not motor controllers per 430.81 (A), so they don?t enter the picture either.
 
Re: Article 430.102(A) - Disconnector within Sight

a co worker of mine would argue in favor of the disconnect at the mov. he worked at a cement plant and the mov was energized by mistake. that mistake dumped 3,000 pounds of cement onto 3 people before it was shut off. no one was hurt fortunately.

a friend of mine also lost his leg due to not having a local disconnect at the motor.
 
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