Motor field stop buttons and disconnects

joshtrevino

Member
Location
Beaumont, TX
I have a project in which there will be a centralized MCC powering motors throughout a facility. All motors will have a bucket mounted circuit breaker to serve as the controller disconnecting means. The circuit breakers in the MCC will be equipped for lockout, but will not be in sight of the motors that they are controlling.

Does NEC 430.102 require a field disconnecting means that is in sight of the motor?

Could this be accomplished with a field stop button in the motor control circuit?

Would a field HMI panel in sight of the motor with the ability to stop the motor over a network satisfy this requirement?
 

Smart $

Esteemed Member
Location
Ohio
I have a project in which there will be a centralized MCC powering motors throughout a facility. All motors will have a bucket mounted circuit breaker to serve as the controller disconnecting means. The circuit breakers in the MCC will be equipped for lockout, but will not be in sight of the motors that they are controlling.

Does NEC 430.102 require a field disconnecting means that is in sight of the motor?

Could this be accomplished with a field stop button in the motor control circuit?

Would a field HMI panel in sight of the motor with the ability to stop the motor over a network satisfy this requirement?
Yes, 430.102 requires a motor disconnect in sight of the motor... but the controller disconnect can serve as a motor disconnect if within sight of motor. If the controller disconnect is not within sight of motor, it can still be the required disconnect for the motor, but conditional (see 430.102(B)(2) Exception).

Any other means to stop the motor is not permitted.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
I have a project in which there will be a centralized MCC powering motors throughout a facility. All motors will have a bucket mounted circuit breaker to serve as the controller disconnecting means. The circuit breakers in the MCC will be equipped for lockout, but will not be in sight of the motors that they are controlling.

Does NEC 430.102 require a field disconnecting means that is in sight of the motor?

take a look at the exception allowed for industrial facilities.

Could this be accomplished with a field stop button in the motor control circuit?

a stop button is not a disconnecting means.

Would a field HMI panel in sight of the motor with the ability to stop the motor over a network satisfy this requirement?
an HMI is also not a disconnecting means.
The exception that is most helpful reads:

(b) In industrial installations, with written safety procedures,
where conditions of maintenance and supervision
ensure that only qualified persons service the equipment
 

kwired

Electron manager
Location
NE Nebraska
Yes, 430.102 requires a motor disconnect in sight of the motor... but the controller disconnect can serve as a motor disconnect if within sight of motor. If the controller disconnect is not within sight of motor, it can still be the required disconnect for the motor, but conditional (see 430.102(B)(2) Exception).

Any other means to stop the motor is not permitted.
Sorry but there are many ways to "stop" the motor, but limited ways of "disconnecting" it, which I know you are aware of just that your last sentence there maybe needs some clarification.
 

Smart $

Esteemed Member
Location
Ohio
Sorry but there are many ways to "stop" the motor, but limited ways of "disconnecting" it, which I know you are aware of just that your last sentence there maybe needs some clarification.
It said "Any other means...", i.e. aside from the means I mentioned. The only means I mentioned were motor disconnect and controller disconnect. I don't see how that can be construed... :happyno:
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
...
Any other means to stop the motor is not permitted.
Sorry but there are many ways to "stop" the motor, but limited ways of "disconnecting" it, which I know you are aware of just that your last sentence there maybe needs some clarification.
It said "Any other means...", i.e. aside from the means I mentioned. The only means I mentioned were motor disconnect and controller disconnect. I don't see how that can be construed... :happyno:
Those are means to disconnect the motor....means of stopping the motor include, but are not limited to means the disconnecting a motor.
 

Smart $

Esteemed Member
Location
Ohio
Those are means to disconnect the motor....means of stopping the motor include, but are not limited to means the disconnecting a motor.
So disconnecting a motor doesn't stop it? :blink:

The OP and my comment are not about stopping the motor. Don't be taking my comment out of context. ;)

Here, let me spell it out for you two...

Any means of stopping the motor other than the motor disconnect or controller disconnect is not permitted as the rquired disconnecting means..
 

kwired

Electron manager
Location
NE Nebraska
Your last line in post #2 is a lot different from the last line in post #7.
I agree, and after reading post 7 and then coming back to post 2, for some reason post 2 doesn't come to me the same way it did the first time around, but more than anything I wanted to clarify for anyone else reading that maybe has questions - basically what was said in post 7.
 

joshtrevino

Member
Location
Beaumont, TX
The exception that is most helpful reads:
In a project meeting someone said that NEC requires a field stop button within sight of the motor, however, it appears to me that a field disconnect is what is required and that NEC does not require the field stop button. Correct?

Also, per your comments above, a field stop button is not even a means of motor disconnect. Correct?
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
In a project meeting someone said that NEC requires a field stop button within sight of the motor, however, it appears to me that a field disconnect is what is required and that NEC does not require the field stop button. Correct?

Also, per your comments above, a field stop button is not even a means of motor disconnect. Correct?
The NEC does not require any "stop" buttons.
Stop buttons or any other device that does not directly interrupt the power to the motor is not a disconnect. The disconnect must physically disconnect the motor from the power source.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
In a project meeting someone said that NEC requires a field stop button within sight of the motor, however, it appears to me that a field disconnect is what is required and that NEC does not require the field stop button. Correct?

Also, per your comments above, a field stop button is not even a means of motor disconnect. Correct?
I do not believe there is any requirement in the NEC for a stop PB at all, in the field or anywhere else.

A PB of an appropriate type might be considered an adequate disconnecting means under certain conditions. See 430.109. I do not recall ever seeing this done though. It would have to open all the power conductors to the motor and not just the control circuit.

I suspect from the context of your question that the field stop PB being discussed is in the control circuit. if so, it is not a disconnecting means because it does not directly open the power conductors to the motor.

IME it is not unusual for a plant to have a practice of locating a stop PB or an emergency stop PB in the vicinity of at least some motors. This is not an NEC requirement though.
 

kwired

Electron manager
Location
NE Nebraska
IME it is not unusual for a plant to have a practice of locating a stop PB or an emergency stop PB in the vicinity of at least some motors. This is not an NEC requirement though.
That stop button or an E-stop button still is not a motor disconnecting means, it is nothing more then a control for the process, it may or may not remove all sources of energy to the equipment, but does open enough conductors to cause a change in operation of the equipment.

A stop button could operate a shunt trip on a breaker, but the breaker is the disconnect not the stop button.
 
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