We are having some debate here about the requirement of a disconnect on every industrial control panel. Would someone comment on whether a disconnect is required on a control panel that is 120 VAC with maybe a PLC and some relays terminals etc in it, to control a simple machine? No three phase or motors.

 

You should review NFPA 79 "Electrical Standard for Industrial Machinery" (USA requirements). This answers your question.

Additionally in the USA it is a UL requirement per UL 508A "Industrial Control Panels" Sec. 66.6

http://multiterra.mooload.com/file.php?file=files/1137687305/Machine_Disconnect_Switch.zip

 

The rule of thumb that we use and I believe it is pretty close to code: If it isnt in the same room as the breaker or diconnect that supplies the device OR if it is in the same room and more than 25 feet away from the disconnect or breaker that supplies the device.then install one on the cabinet.

Gerald Beaudoin

 

A "supply circuit disconnecting means" is required; for a machine with motor loads of up to 2hp, that means can be a plug/receptacle as long as the plug is "located within sight of the operator station" and is "readily accessible." If the plug/receptacle is rated at over 20A, it also has to be locking.

So, the rough answer is "no." You might still want one for convenience, or to meet plant specific Lockout/Tagout requirements, or just because the customer spec requires it. NFPA 70 is a little hazy on this; a better reference is NFPA 79, which you guys should get a copy of if you're building panels or machines, even small ones.