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Monday, January 21, 2019

Question:

I have noticed a Romex connector to Clamp individual Unjacketed MTW rated wires in a Machine tool Control Panel. Theses conductors will carry 400 volts to and from an Inverter type Motor Drive. Is this a violation of NEC or UL508?

Kurt Adlon

A

Answer:

Hey Kurt thanks for your question. The Word “Romex” is a registered trademark of Southwire Company. We have been asked to point that out, the correct term is Nonmetallic Sheathed Cable.

Machine Tool Wiring (MTW) is included in Table 310.104(A) with an intended application as machine tool wiring. The Informational Note refers to NFPA 79.

Nonmetallic-sheathed-cable Connectors (PXJV) are intended for use with nonmetallic-sheathed cable and sometimes other cable types. More information is available at:

http://productspec.ul.com/document.php?id=PXJV.GuideInfo

If the Industrial Control Panel is listed (UL 508A), ask the manufacturer and certifying laboratory how they determined the cable connector was suitable for that purpose. If the Industrial Control Panel is not listed (more likely) the AHJ is still responsible for approval. A "cable clamp" is generally not suitable for securing individual conductors so it would be not be acceptable based on 110.3(B).

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