Programmable Disconnect

[SGWB]

Does anyone know if I can perform lockout using a safety PLC and motor contactors? We have a system that has 3 major devices (motor groups), each fed from the same power distribution panel. The suggestion was to install 3 sets of redundant motor contactors in the power distribution panel, and distribute main power (480VAC) to each device through a set of motor contactors. A safety PLC would remotely control power to each device by enabling or disabling the pair of motor contactors for each device. The decision to enable or disable would be based on the position of a lockable selector switch that would be set and locked by the user. The signal from the lockable selector switch would be fed into the Safety PLC. What do you think? Thanks.

 

[rbalex]

No. A motor disconnecting means must be of a type specified in Section 430.109. The list is exclusive ("shall be") and alternate methods are excluded.

 

[petersonra]

Does anyone know if I can perform lockout using a safety PLC and motor contactors? We have a system that has 3 major devices (motor groups), each fed from the same power distribution panel. The suggestion was to install 3 sets of redundant motor contactors in the power distribution panel, and distribute main power (480VAC) to each device through a set of motor contactors. A safety PLC would remotely control power to each device by enabling or disabling the pair of motor contactors for each device. The decision to enable or disable would be based on the position of a lockable selector switch that would be set and locked by the user. The signal from the lockable selector switch would be fed into the Safety PLC. What do you think? Thanks.

I think you are trying to make it too complicated to be safe. In any case, Bob is right about what is allowed to be a disconnecting means in the code.

 

[kwired]

Would you trust the thing to not start if your life depended on it, even in some abnormal situations? Types of disconnects that are required are by design not very likely to close a circuit at all when they are locked off.