Understanding Power & Control Cables for Industrial Applications

Updated: August 20, 2025

TL;DR: Power cables carry load current; control cables carry low-level signals. Most industrial work is ≤1 kV; MV/HV needs dedicated designs. Key refs: NEC 310, 336, 392, 725, 727; UL 1277 (TC-ER); UL 2277 (VFD motor leads); OSHA 1910.305 (tray use). Choose TC-ER for fixed tray power, VFD-rated for drives, PLTC/ITC for controls, THHN in raceway, and SOOW for temporary power. Do: IR test, maintain separation per 725.136, support tray exits, respect bend radius. Don’t: dump everything in trays, overbend, or mis-terminate shields. Suffolk County projects should confirm details with the AHJ and PSEG Long Island. For quick product detail see the tray cables guide or call (631) 283-3600.

What they are

Power cables deliver energy to equipment and distribution. Typical choices include THHN/THWN-2 in raceway, Type TC-ER in trays, or MC where mechanical protection is required. See stocked copper THHN building wire.

Control cables carry commands, interlocks, and instrumentation signals. Use shielded constructions where noise is a risk and follow NEC separation rules by Article/Section.

Voltage bands

• Low voltage (≤1,000 V): Most plant power, VFD outputs, and control circuits. NEMA WC 70/ICEA S-95-658 covers many 2 kV-and-below constructions.
• Medium voltage (1–35 kV): Different insulation systems and terminations; coordinate with the AHJ and utility.
• High voltage (>35 kV): Specialized transmission/distribution only.

Core standards to reference

• NEC: 310 (conductors), 336 (Type TC), 392 (cable trays), 725 (power-limited control), 727 (Type ITC), plus 250 and 300 where applicable.
• UL 1277: Electrical power and control tray cables, including TC-ER.
• UL 2277: Flexible motor supply cable used with VFDs.
• OSHA 1910.305: Wiring methods in general industry, including tray use and support.

Selection cheatsheet

• Fixed power in trays: Type TC-ER per UL 1277. Support with Cable Trays & Struts.
• Motors and VFD outputs: Use VFD-rated cable per UL 2277. Conduit drops available from metallic conduit.
• Control and instrumentation: Choose PLTC or ITC; follow 725.136 for separation. Protect runs with wire protection.
• Temporary power and tools: SOOW/SJOOW cords; see SOOW portable cords.
• Raceway building wire: THHN/THWN-2 per NEMA WC 70/ICEA S-95-658. Stock available under copper THHN.

Dos and don’ts that prevent callbacks

Do

• Inspect and test before pulling. IR and continuity early.
• Maintain separation where required by 725.136; cross at right angles to reduce coupling.
• Support correctly. Article 392 for trays; 336.10(7) for limited exposed TC-ER runs. Use listed hardware like threaded rods & accessories.
• Respect bend radius and termination instructions.

Don’t

• Dump everything in trays. OSHA 1910.305 limits what’s allowed and requires support.
• Mix circuit classes without following Article 725.
• Overbend multi-conductor and VFD cables.

Suffolk County AHJ reminder

Always confirm requirements with your Authority Having Jurisdiction and PSEG Long Island before submittals or energization.

Ready-to-pull materials

Start with Cable Trays & Struts, THHN building wire, SOOW cords, metallic conduit, and wire protection. For Suffolk County assistance, call (631) 283-3600.

Author: Revco Editorial Team — Electrical Content Editor
Technical Reviewer: Revco Applications Team — NY-licensed electricians

Business/Operations disclaimer: This guide is for general educational purposes. It does not replace the NEC, local amendments, manufacturer instructions, or utility requirements. Product specifications and availability can change without notice. Verify all details with your AHJ and the manufacturer before purchasing or installing.

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Since 1978, Revco Lighting + Electrical Supply has been Long Island’s trusted source for quality products, expert support, and personalized service. With six branches across Suffolk County and a dedicated team, we help contractors, builders, and facilities teams get the job done right. Whether you need everyday electrical essentials or project-driven solutions, we’re here to make sure you have what you need, when you need it.

Sources

• UL 1277: Electrical Power and Control Tray Cables
• UL 2277: Flexible Motor Supply Cable
• OSHA 29 CFR 1910.305: Wiring methods
• NEMA WC 70/ICEA S-95-658: Contents and scope