Portable Cord Types: SOOW, SJOOW, SJT & More

Portable cord — also called portable power cable, flexible cord, or simply "SO cord" — is a flexible, multi-conductor cable designed for temporary connections between portable equipment and a power source. It powers everything from job site tools and stage lighting to industrial motors and food service equipment. The NEC® designates portable cord types using a letter code that tells you the jacket material, voltage class, and temperature rating. This guide decodes every common type so you can specify the right cord for your application.

How to Read a Portable Cord Type Designation

Portable cord type designations follow a standardized letter system defined by the NEC® (Article 400) and UL. Each letter in the designation describes a specific construction characteristic. Reading from left to right:

So when you see SOOW, you can decode it as: Service grade (600V) + Oil-resistant jacket + Oil-resistant conductor insulation + Weather resistant. Or SJTW: Service Junior (300V) + Thermoplastic conductor insulation + Weather resistant.

Service Grade (S-Type) — 600V Portable Cord

Service grade portable cords carry a 600V rating and are built for heavy-duty industrial and commercial applications. The heavier jacket and insulation provide the mechanical toughness and voltage class needed for construction sites, manufacturing equipment, temporary power distribution, and stage/event power.

SOOW — The Industrial Standard

SOOW is the most widely specified portable cord for industrial and commercial use. Both the outer jacket and the individual conductor insulation are oil-resistant synthetic rubber (typically EPDM or neoprene), making the cable resistant to oils, solvents, chemicals, and abrasion. SOOW is rated 600V and 90°C, and carries a "W" rating for outdoor and wet locations.

The rubber construction gives SOOW excellent flexibility, even in cold temperatures — it remains pliable down to approximately -40°C (-40°F), which is critical for outdoor winter construction and cold storage facilities. The oil-resistant jacket handles contact with hydraulic fluid, cutting oils, and fuel without degrading.

SOOW is available from 18 AWG through 2 AWG in standard configurations, with conductor counts ranging from 2 to 44 or more. Common configurations include 10/3, 12/3, and 14/3 for tool and equipment cords, and higher conductor counts (10/12, 10/16, 10/24) for multi-circuit portable power distribution. Ramcorp stocks SOOW portable cord in a wide range of sizes, as well as STOOW 600V and SEOOW 600V portable cord for specialized applications.

Best applications: construction site tools, industrial portable equipment, temporary power distribution, mining equipment, stage and event power, welding machine leads (small), and any 600V portable connection exposed to oil, weather, or physical abuse.

SOW — Oil-Resistant Jacket, Standard Insulation

SOW has an oil-resistant outer jacket but uses standard (non-oil-resistant) rubber conductor insulation. It is rated 600V with a "W" weather/water resistance rating. SOW costs slightly less than SOOW because the individual conductor insulation is not oil-resistant — only the outer jacket is.

SOW is suitable for heavy-duty applications where the cable jacket may contact oil or chemicals but the individual conductors inside are protected by the jacket and are unlikely to be exposed directly. In practice, SOOW has largely replaced SOW in most specifications because the cost difference is minimal and double oil resistance provides better long-term reliability.

Best applications: heavy-duty portable equipment where oil exposure is limited to the outer jacket surface.

STOW — Thermoplastic Insulation, Oil-Resistant Jacket

STOW uses thermoplastic (PVC) construction for both the jacket and conductor insulation, with oil-resistant and weather-resistant properties. It is rated 600V. The thermoplastic construction is less flexible than rubber at low temperatures but costs less to manufacture.

STOW is less common than SOOW in industrial settings because PVC stiffens in cold weather and does not offer the same level of oil and chemical resistance as rubber. However, it serves well in moderate-temperature applications where the 600V rating is needed but the full chemical resistance of SOOW is not required.

Best applications: 600V portable equipment in temperature-controlled environments, indoor industrial tools, and applications where cost is a factor and cold-weather flexibility is not needed.

Service Junior (SJ-Type) — 300V Portable Cord

Service Junior cords carry a 300V rating and use a lighter construction than S-type cords. They are designed for lighter-duty equipment — appliances, office equipment, small power tools, and portable lighting. The thinner jacket and insulation make SJ cords more flexible and lighter weight than their S-type counterparts, but they cannot be used on circuits exceeding 300V.

SJOOW — Light-Industrial Oil-Resistant Cord

SJOOW is the 300V equivalent of SOOW — oil-resistant jacket, oil-resistant conductor insulation, weather resistant. It provides the same chemical and environmental resistance as SOOW in a lighter, more flexible package for 300V applications.

SJOOW is popular for food service equipment (commercial kitchens, food trucks), portable lighting, small power tools, and light industrial equipment where 300V is sufficient and oil or grease exposure is likely. The rubber construction maintains flexibility in cold conditions, and the oil-resistant insulation handles the greases and cleaning chemicals common in food service environments.

Ramcorp stocks SJOOW portable cord in common sizes for commercial and light-industrial applications.

Best applications: commercial kitchen equipment, food service, portable lighting, light-duty power tools, and 300V circuits with oil or grease exposure.

SJT — General-Purpose Thermoplastic Cord

SJT uses a thermoplastic (PVC) jacket and PVC conductor insulation. It is the most common cord type for indoor appliances, office equipment, and consumer electronics — the standard power cord on vacuum cleaners, floor fans, and office equipment. SJT is rated 300V and 60°C (or 90°C for SJT-2 variants).

SJT is not oil-resistant and not rated for outdoor use. It is the most economical portable cord type and is suitable for any indoor, dry-location 300V application where oil resistance and extreme flexibility are not required.

Best applications: indoor appliances, office equipment, consumer power cords, and light-duty indoor portable equipment.

SJTW — Weather-Resistant General-Purpose Cord

SJTW adds a "W" weather/water resistance rating to the SJT construction. The PVC formulation is modified for UV and moisture resistance, allowing outdoor use. SJTW is the standard cord type for outdoor extension cords, holiday lighting, landscape equipment, and any 300V portable connection that will be exposed to weather.

Best applications: outdoor extension cords, holiday and landscape lighting, outdoor power tools, and portable outdoor equipment at 300V.

SJOW — Rubber Jacket, Standard Insulation

SJOW has an oil-resistant rubber outer jacket with standard (non-oil-resistant) rubber conductor insulation. It is rated 300V with weather resistance. Like SOW, it has been largely superseded by SJOOW in most specifications because the cost difference is small.

Best applications: 300V portable equipment where jacket oil resistance is needed but individual conductor oil resistance is not critical.

Portable Cord Type Comparison

Conductor Sizes, Counts, and Ampacity

Portable cord is available in conductor sizes from 18 AWG through 2 AWG (and larger for specialty applications), with conductor counts from 2 to 44 or more. The conductor size determines the current-carrying capacity (ampacity), which must match the circuit breaker or overcurrent protection serving the cord.

Ampacity values are for 3-conductor cords based on NEC® Table 400.5(A)(1) at 30°C ambient. Actual ampacity may be reduced by ambient temperature, number of conductors, and duty cycle. Always verify with the applicable NEC® table for your specific cord type and configuration.

Conductor counts follow standard configurations. 2-conductor cords (no ground) are used for double-insulated equipment. 3-conductor cords (hot, neutral, ground) are the most common for 120V single-phase equipment. 4-conductor cords handle 240V single-phase (two hots, neutral, ground) or 208V three-phase (three hots, ground). Higher conductor counts — 5, 7, 10, 12, 16, 24, and beyond — are used for multi-circuit portable power distribution panels, stage lighting, and industrial control applications.

NEC® Requirements for Portable Cord

NEC® Article 400 governs the use of flexible cords and cables. Key requirements that affect portable cord selection:

Permitted uses (400.10): Portable cord is permitted for connection of portable equipment, temporary wiring (per Article 590), pendant connections, wiring of fixtures, and connection of moving parts. It is not permitted as a substitute for fixed wiring — you cannot run portable cord through walls, ceilings, floors, or above suspended ceilings as permanent wiring.

Not permitted uses (400.12): Portable cord cannot be used as a substitute for the fixed wiring of a structure, where run through holes in walls, ceilings, or floors, where run through doorways, windows, or similar openings, where attached to building surfaces (except with listed cord clips for temporary decorative lighting), or where concealed by walls, floors, or ceilings.

Ampacity (400.5): The ampacity of portable cord is determined by NEC® Table 400.5, which lists maximum current for each conductor size based on cord type and number of conductors. These values are generally lower than the ampacity of building wire of the same gauge because portable cord operates in a bundled configuration with reduced heat dissipation.

Overcurrent protection (400.13): Portable cord must be protected by an overcurrent device (fuse or breaker) rated no higher than the ampacity listed in Table 400.5 for the specific cord type and size.

Grounding (400.22 / 400.23): For equipment that requires grounding, the portable cord must contain an equipment grounding conductor. The grounding conductor must be identified by green or green-with-yellow-stripe insulation per 400.23.

Splicing (400.9): Flexible cord may not be spliced except where permitted and in accordance with 400.9 methods. In general, damaged portable cord should be replaced, not repaired with tape or splice kits on the job site.

S-Type vs. SJ-Type: When Voltage Class Matters

The most fundamental choice is between S-type (600V) and SJ-type (300V). This is not just a voltage rating — it determines the jacket thickness, insulation thickness, and overall mechanical toughness of the cord.

Use S-type cords on construction sites, in industrial plants, for temporary power distribution, and anywhere the cord will be subjected to heavy physical abuse, vehicle traffic, or 480V circuits. Use SJ-type cords for appliances, office equipment, 120V portable tools in clean environments, and other light-duty applications where the heavier S-type construction is unnecessary.

When in doubt, specify S-type. The additional cost is modest, and the heavier construction provides a safety margin against physical damage, especially on job sites where cords get run over, stepped on, and dragged across rough surfaces.

Rubber vs. PVC (Thermoplastic) Construction

The choice between rubber and PVC construction affects flexibility, chemical resistance, temperature performance, and cost.

Rubber (SOOW, SJOOW, SOW, SJOW) — Rubber-jacketed cords use EPDM, neoprene, or similar synthetic rubber compounds for the jacket and/or conductor insulation. Rubber provides superior flexibility at all temperatures, especially cold weather — SOOW remains flexible down to -40°C while PVC cords become stiff and less flexible in cold temperatures. Rubber also resists oils, chemicals, and abrasion better than PVC and has excellent memory — it returns to its original shape after being coiled, kinked, or compressed.

PVC (SJT, SJTW, STOW) — PVC-jacketed cords are less expensive and lighter weight than rubber equivalents. PVC performs well in moderate temperatures and is adequate for indoor, dry-location applications without chemical exposure. However, PVC becomes stiff and less flexible in cold temperatures, is not inherently oil-resistant, and has lower abrasion resistance than rubber.

For any application involving outdoor use in cold climates, oil or chemical exposure, or heavy physical abuse, rubber construction (SOOW or SJOOW) is the clear choice. PVC cords (SJT, SJTW) are appropriate for controlled indoor environments where cost is the primary concern.

Portable Cord Applications by Industry

Construction

SOOW is the standard portable cord on construction sites. It powers hand tools, temporary lighting, welders, and power distribution panels (spider boxes). The 600V rating, rubber construction, and oil/weather resistance handle the abuse of a job site — UV exposure, concrete dust, vehicle traffic, rain, and temperature extremes. Most specifications require SOOW for any cord used outdoors on a construction project.

Entertainment and Events

Stage lighting, sound systems, and event power distribution rely heavily on SOOW portable cord, often in high conductor counts (10/12, 10/16, 10/24, 12/7) for multi-circuit dimmer and distribution runs. The flexibility of rubber construction makes it easy to coil, deploy, and strike quickly — essential for touring productions and temporary event installations. Entertainment industry specifications typically require SOOW with specific color coding (often black jacket with colored conductors per ESTA standards).

Food Service and Commercial Kitchen

Commercial kitchens need oil-resistant, water-resistant cord that handles grease, cleaning chemicals, and wet floors. SJOOW is the standard choice for 120V kitchen equipment — fryers, mixers, slicers, and prep equipment. The 300V rating is sufficient for 120V circuits, and the oil-resistant rubber construction handles the kitchen environment. For 208V or 240V three-phase kitchen equipment, SOOW is required.

Manufacturing and Industrial

Portable cord connects portable motors, hand tools, test equipment, and temporary power feeds on the plant floor. SOOW is the default for any 480V or 600V portable connection. For portable equipment on 120V or 208V circuits, SJOOW provides adequate voltage class with a more flexible profile. In environments with cutting oils, hydraulic fluid, or chemical exposure, always specify the double "OO" (oil-resistant jacket AND conductor insulation).

Mining

Mining applications require cords that meet MSHA (Mine Safety and Health Administration) standards in addition to UL and NEC® requirements. Mining-grade portable cord (Type G, Type G-GC, Type SHD-GC) is a specialized category beyond the scope of this guide, but standard SOOW is used for many surface mining and support applications where MSHA mining-grade cord is not required.

Quick Selection Guide

1. Determine the voltage — Circuits above 300V (208/240V three-phase, 277V, 480V) require S-type (600V) cord. Circuits at 300V or below (120V, 208V single-phase, 240V single-phase) can use SJ-type (300V) cord.
2. Assess the environment — Outdoor, wet, or oil exposure? Specify "OO" and "W" (SOOW or SJOOW). Indoor only, clean and dry? PVC types (SJT, SJTW) may be sufficient.
3. Check the temperature range — Cold weather or cold storage below 0°C? Rubber construction only (SOOW, SJOOW). Moderate indoor temperatures? PVC is acceptable.
4. Size the conductors — Match conductor AWG to the circuit ampacity per NEC® Table 400.5. For extension cords, a common industry rule of thumb is to upsize one gauge for runs over 50 feet, and two gauges for runs over 100 feet, to reduce voltage drop.
5. Count the conductors — 2-conductor for double-insulated equipment. 3-conductor for standard 120V grounded equipment. 4-conductor for 240V or 208V three-phase. Higher counts for multi-circuit distribution.
6. Check for industry-specific requirements — Construction sites typically require SOOW per specification. Food service may require NSF-listed cord. Entertainment may require ESTA-compliant cord. Verify the applicable standard before ordering.

Frequently Asked Questions

What is the difference between SOOW and SJOOW?

SOOW is rated 600V (Service grade) and SJOOW is rated 300V (Service Junior). Both have oil-resistant rubber jackets and oil-resistant rubber conductor insulation with weather resistance. SOOW has a heavier jacket and thicker insulation for its higher voltage rating, making it more mechanically rugged. Use SOOW for 480V or 600V circuits and heavy-duty industrial applications. Use SJOOW for 120V–300V circuits where a lighter, more flexible cord is preferred.

Can I use portable cord as permanent wiring?

No. NEC® 400.12 prohibits using flexible cord as a substitute for the fixed wiring of a structure. Portable cord cannot be run through walls, ceilings, floors, doorways, or windows, concealed behind building surfaces, or used as permanent branch circuit wiring. It is designed for temporary connections to portable equipment and must be visible and accessible along its entire length.

What is the difference between SJT and SJTW?

SJT is rated for indoor dry locations only. SJTW adds a "W" weather/water resistance rating, allowing outdoor use. The PVC jacket on SJTW is formulated to resist UV degradation and moisture penetration. For any cord that will be used outdoors — even occasionally — specify SJTW instead of SJT.

Why is SOOW preferred over SJT for construction sites?

SOOW provides four advantages critical for construction: (1) 600V rating covers all job site voltages including 480V, (2) rubber construction stays flexible in cold weather, (3) oil-resistant jacket and insulation handle fuel, hydraulic fluid, and concrete chemicals, and (4) the heavier rubber jacket resists the abrasion, crushing, and impact damage that construction site cords endure daily. Most construction specifications require SOOW, and OSHA inspectors routinely cite damaged cords, improper repairs, and missing grounds on job sites.

What gauge extension cord do I need?

Match the cord gauge to the amperage of the tool or equipment and the length of the run. For 15A circuits (standard 120V outlet), use 14 AWG for runs up to 50 feet, 12 AWG for 50–100 feet, and 10 AWG for runs over 100 feet. For 20A circuits, use 12 AWG for runs up to 50 feet and 10 AWG for longer runs. Undersized cords cause voltage drop that reduces tool performance, increases heat, and can create a fire hazard.

Can I repair a damaged portable cord with electrical tape?

NEC® 400.9 restricts splicing of flexible cords. In general, damaged portable cord should be shortened and re-terminated (if the damage is near one end) or replaced entirely. Tape repairs are not code-compliant for permanent use and are a common OSHA citation on job sites. For temporary emergency repair until a replacement cord is available, use a listed cord repair kit — not electrical tape — and replace the cord as soon as practical.

What does the "-2" suffix mean (e.g., SJTO-2)?

The "-2" suffix indicates a 90°C temperature rating on the conductor insulation, compared to the standard 60°C or 75°C rating. This is useful for equipment that generates significant heat at the cord connection point — such as industrial heaters, high-wattage lighting fixtures, and some commercial kitchen equipment. The higher temperature rating provides a safety margin against insulation degradation from heat.

Related Resources

• How to Read a Cable Print Legend: Markings, Codes & What They Mean
• UL Listings for Wire & Cable: What to Look For
• How to Choose the Right Cable for Your Project
• Tray Cable Applications & Selection Guide
• AWG Wire Gauge Guide: Sizes, Ampacity & Selection

Need Help Choosing the Right Portable Cord?

Our sales team can help you select the right portable cord for your project, provide technical specifications, or prepare a custom quote for bulk orders. Contact us today.

Contact Us Special Orders & Custom Cable

Disclaimer: This guide is provided for informational purposes only and is not installation advice. Installing wire & cable can be dangerous and pose a risk of possible electric shock or other hazards. Specifications, availability, and pricing are subject to change without notice. Always verify product specifications with the manufacturer's current datasheet before ordering. Consult a licensed professional and your local authority having jurisdiction (AHJ) before specifying or installing cable. Images are for illustration purposes and may not reflect actual installed products.

The information on this page is provided for general reference only and may contain errors or omissions. NEC® is a registered trademark of the National Fire Protection Association (NFPA®). UL® is a registered trademark of Underwriters Laboratories. OSHA is a registered trademark of the U.S. Department of Labor. All other trademarks, product names, and brand names referenced on this page are the property of their respective owners. Ramcorp Wire & Cable is not affiliated with or endorsed by these organizations unless explicitly stated.