330.30(D) MC Cable. Unsupported Cables.
Code Change Summary: New code language was added to allow certain MC cables to remain unsupported when flexibility is necessary.
Sometimes, wiring methods require flexibility or movement. If installing an MC cable because flexibility is needed after installation to allow for equipment movement or vibration, supporting the cable rigidly in place would defeat the purpose.
Now MC cable, of the interlocking type, can remain unsupported up to 3 ft. from the last point where the cable is securely fastened for the following installations:
- Where flexibility is necessary to minimize the transmission of vibration from equipment.
- To provide flexibility for equipment that requires movement after installation.
Below is a preview of the NEC®. See the actual NEC® text at NFPA.ORG for the complete code section. Once there, click on the “free access” tab and select the applicable year of NFPA 70 (National Electrical code).
2011 Code language:
330.30(D) Unsupported Cables. Type MC cable shall be permitted to be unsupported where the cable:
(1) Is fished between access points through concealed spaces in finished buildings or structures and supporting is impractical; or
(2) Is not more than 1.8 m (6 ft) in length from the last point of cable support to the point of connection to luminaires or other electrical equipment and the cable and point of connection are within an accessible ceiling. For the purpose of this section, Type MC cable fittings shall be permitted as a means of cable support.
2014 Code Language:
330.30(D) Unsupported Cables. Type MC cable shall be permitted to be unsupported where the cable:
(1) Is fished between access points through concealed spaces in finished buildings or structures and supporting is impractical.
(2) Is not more than 1.8 m (6 ft) in length from the last point of cable support to the point of connection to luminaires or other electrical equipment and the cable and point of connection are within an accessible ceiling. For the purpose of this section, Type MC cable fittings shall be permitted as a means of cable support.
(3) Is Type MC of the interlocked armor type in lengths not exceeding 900 mm (3 ft) from the last point where it is securely fastened and is used to connect equipment where flexibility is necessary to minimize the transmission of vibration from equipment or to provide flexibility for equipment that requires movement after installation.
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330.30(D) MC Cable. Unsupported Cables.
Below is a Real Question from our Electrical Continuing Education Courses for Electrical License Renewal:Which of the following MC cables can remain unsupported for the last 3 ft. as it connects to an air compressor motor?
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