MCC requirements

[Deke12754]

I'm having some issues with an AHJ in another state. Our company builds custom motor control cabinets. These are large usually 7' tall and 4' to 6' wide. The inspector is insisting that we meet the code requirements for wire fill in are wire ducts inside the cabinet. He also has problems with the co- mingling of the control voltage wire 24 volt - 120 volt with the high voltage wire ( 480 volts ). Are cabinets are very meticulous and we've never had any problems with these issues before. Although I know that the AHJ has the last say what are your thoughts. Thank you.

 

[jim dungar]

I'm having some issues with an AHJ in another state. Our company builds custom motor control cabinets. These are large usually 7' tall and 4' to 6' wide. The inspector is insisting that we meet the code requirements for wire fill in are wire ducts inside the cabinet. He also has problems with the co- mingling of the control voltage wire 24 volt - 120 volt with the high voltage wire ( 480 volts ). Are cabinets are very meticulous and we've never had any problems with these issues before. Although I know that the AHJ has the last say what are your thoughts. Thank you.

Panel wire duct is not an NEC raceway, it is a wire management item instead (like wire ties and spiral wrap). although I suppose an arguement could be made that it is a wireway. What actual NEC articles is the AHJ citing?

 

[Minuteman]

The inspector is insisting that we meet the code requirements for wire fill in are wire ducts inside the cabinet. He also has problems with the co- mingling of the control voltage wire 24 volt - 120 volt with the high voltage wire ( 480 volts ).

I love it when they have a problem and are not specific. Did you ask him to quote a CODE reference that you violated for duct fill?

We are still in the 2002 cycle. 300.3(C)(1) says if the voltages are 600v or less and the conductors all have a rating of the largest voltage, then they can co- mingle. Just use 600v rated wire for the 480, 120 and 24volt circuits.

 

[petersonra]

Plastic wire duct usually has a manufacturer's limit on fill, 40% seems to be the number I recall. If you are in violation of the manufacturer's directions...

He should probably not be sticking his neck into an equipment design issue in any case, especially if this is a UL listed assembly. If this is just a big box with a bunch of starters jammed in it, he may have legitimate concerns.

I am not a big fan of co-mingling the 24, 120, and 480V wiring either, but every MCC I have ever seen does it to some extent.

 

[infinity]

I don't see how a listed piece of equipment built to a UL standard is required to comply with the NEC. Is the equipment designed and built this way and so listed?

 

[petersonra]

I don't see how a listed piece of equipment built to a UL standard is required to comply with the NEC. Is the equipment designed and built this way and so listed?

I don't see how an unlisted piece of equipment is either.

Premises Wiring (System). That interior and exterior wiring,
including power, lighting, control, and signal circuit
wiring together with all their associated hardware, fittings,
and wiring devices, both permanently and temporarily installed,
that extends from the service point or source of
power, such as a battery, a solar photovoltaic system, or a
generator, transformer, or converter windings, to the outlet(
s). Such wiring does not include wiring internal to appliances,
luminaires (fixtures), motors, controllers, motor
control centers, and similar equipment.