Means of Disconnect

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bdktoys

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York, Pa.
I'm a little confused with how the code has explained means of disconnect for a motor controller.
I understand that per 430.101 and 440.11 I am required to have a means of disconnect for the motor controller to HVAC equipment as well as any other equipment that has a controller.
When disconnecting the controller, does that mean that I must de-energize power to the entire control panel? (ie. the line side of the Circuit Breaker supplied with a piece of equipment control panel) or is the circuit breaker supplied with the equipment ok to serve as my disconnect. Keeping in mind that there is still energized power to the line side of the circuit breaker. The controller cabinet is not totally de-energized.
Where it gets more confusing, section 430.103 allows the diconnecting means in the same enclosure at the controller.
And lets not forget Arc-flash requirements in this mix of things.

My current issue is that I have a roof top HVAC unit with a control panel that has a main circuit breaker. Do I need a disconnect switch ahead of the controller?
Thank you for your help.
 
440.11 General. The provisions of Part II are intended to require disconnecting means capable of disconnecting airconditioning and refrigeration equipment, including motor-compressors and controllers from the circuit conductors.

So if the circuit breaker supplied with the equipment disconnects power from the controller (not necessarily the control cabinet) you do not need another disconnect. Think about the intent of the rule. You want to be sure that the unit is shut off while you work on it so nothing comes on unexpectedly. As long as the breaker in the unit is turned off then there is no chance that motor can come on and rip your fingers off.
 
Yes, I agree with everything you have stated. However, the disconnecting circuit breaker is located within the control cabinet/controller itself. What you are saying is correct about the motor not being able to start and cause harm. Where my concerns are if you are replacing starters, relays and other componets withing the control cabinet. You have not totally de-energized that cabinet because the line side of the circuit breaker is still hot.. At this point, you also have to be concerned with Arc Flash issues.
The code is telling me that we need a disconnect for BOTH the motor AND controller. (430.101 and 430.102.)Where is the point where I must de-energize the controller. Is the circuit breaker in the control cabinet/controller satisfactory to be used as that means of disconnect?
 
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