Flexible tinned copper conductor with cross-linked polyethylene (XLPE) thermoset insulation, built to UL 44 for switchboards, panelboards, switchgear and industrial control panels. The only SIS cable in the world with UL-authorized laser marking.
SIS is the NEC type designation for thermoset-insulated switchboard and switchgear wire (NEC Table 310.104(A)). It is the conductor you find inside switchboards, panelboards, motor control centers and industrial control panels: short, tight, heavily terminated runs where space is scarce and heat builds up.
Next Wire SIS uses fine-stranded tinned copper for flexibility and clean terminations, covered with flame-retardant cross-linked polyethylene (XLPE). The cross-linking is what makes the insulation a thermoset: when it sees heat, it does not soften and run the way thermoplastic PVC does.
Next Wire is the first and only manufacturer in the world authorized by UL to apply permanent laser marking directly on SIS cable. No ink to rub off, no adhesive label to peel: the identification is part of the insulation, applied at the factory, so the marking you inspect in the panel is the marking that left the plant.
| SIS | THHN / THWN-2 | MTW | |
|---|---|---|---|
| Insulation | XLPE thermoset | PVC with nylon jacket (thermoplastic) | PVC (thermoplastic) |
| Standard | UL 44 | UL 83 | UL 1063 |
| Temperature | 90°C | 90°C | 90°C |
| Under heat | Cross-linked; does not melt and drip | Thermoplastic; softens as temperature rises | Thermoplastic; softens as temperature rises |
| Conductor | Flexible tinned copper | Bare copper, solid or stranded | Flexible copper, Class K style |
| Primary use | Wiring inside switchboards, panelboards, MCCs and control panels | Branch circuits and feeders in conduit and cable tray | Machine tool and industrial machinery wiring |
| Building raceway | Not for general raceway wiring | Yes, per NEC Chapter 3 | Not for general raceway wiring |
Need conduit wiring instead? See Next Wire THHN / THWN-2 building wire. For machine control wiring see MTW and the rest of our flexible industrial line.
Internal panel wiring for UL 508A shops and NFPA 79 machinery builds. Flexible enough to dress cleanly into ducts and around hinged doors.
Control and interconnect wiring between breakers, meters, relays and terminal blocks, where heat from adjacent gear is a design factor.
Compartment wiring and control circuits in MCCs, with XLPE insulation that holds its shape at elevated panel temperatures.
Factory wiring for panelboards and power distribution enclosures that need a compact, high-temperature conductor.
Controls wiring for UPS cabinets, transformers and power distribution units, where dense layouts and uptime matter.
Production runs for machinery and equipment builders, including US-Canada supply under UL 44 and CSA C22.2.
| Size | Cond. Dia. (mm) | Cond. Dia. (in) | Ins. Thick. (mm) | Nom. O.D. (mm) | Min. Ins. Thick. (in) |
|---|---|---|---|---|---|
| 14 AWG2.08 mm² | 1.911 | 0.075 | 0.76 | 3.431 | 0.135 |
| 12 AWG3.31 mm² | 2.406 | 0.095 | 0.76 | 3.926 | 0.155 |
| 10 AWG5.26 mm² | 3.044 | 0.120 | 0.76 | 4.564 | 0.180 |
| 8 AWG8.37 mm² | 3.845 | 0.151 | 1.14 | 6.125 | 0.241 |
| 6 AWG13.3 mm² | 5.178 | 0.204 | 1.14 | 7.458 | 0.294 |
| 4 AWG21.2 mm² | 6.507 | 0.256 | 1.14 | 8.787 | 0.346 |
| 2 AWG33.6 mm² | 8.188 | 0.322 | 1.14 | 10.468 | 0.412 |
| 1/0 AWG53.48 mm² | 10.418 | 0.410 | 1.4 | 13.218 | 0.520 |
| 2/0 AWG67.4 mm² | 11.813 | 0.465 | 1.4 | 14.613 | 0.575 |
| 3/0 AWG85 mm² | 13.059 | 0.514 | 1.4 | 15.859 | 0.624 |
| 4/0 AWG107 mm² | 14.733 | 0.580 | 1.4 | 17.533 | 0.690 |
Tinned flexible copper conductor. XLPE thermoset insulation. UL 44 · Rated 600V, 90°C. Dimensions are nominal; see the datasheet for tolerances and stranding.
Custom colors and special stripes available on request for high-volume orders.
SIS is the NEC type designation for thermoset-insulated switchboard and switchgear wire. It is a single-conductor, flexible copper wire insulated with cross-linked polyethylene (XLPE), used for wiring inside switchboards, panelboards, motor control centers and industrial control panels.
SIS uses cross-linked XLPE thermoset insulation and a flexible tinned copper conductor, and it is meant for wiring inside equipment. THHN/THWN-2 is a PVC and nylon thermoplastic building wire intended for conduit and cable tray. Both are rated 600V and 90°C, but they are built to different standards (UL 44 and UL 83) and used in different places.
Standard SIS is intended for switchboard and switchgear wiring and is not meant for general wiring in building raceways. If a job needs conduit, use a conductor marked and listed for that use, for example THHN/THWN-2, and confirm requirements with your authority having jurisdiction.
Standard SIS is intended for dry locations inside equipment. For wet or damp locations use a conductor that carries the appropriate wet-location rating, such as THWN-2.
Next Wire SIS is available from 14 AWG through 4/0 AWG in flexible tinned copper, rated 600V and 90°C. Standard colors are green, black, blue, red, gray and white. Custom colors and stripes are available on request for high-volume orders.
Next Wire is the only manufacturer in the world authorized by UL to laser-mark SIS cable. The marking is applied directly to the insulation at the factory, so there is no ink or adhesive label that can wear off or be removed.
Use the form below or call our sales contact directly. We reply within one business day with pricing, availability and the SIS datasheet.
Next Wire supplies SIS switchboard wire directly to panel shops, OEM manufacturers and electrical distributors across Texas and the Gulf Coast. Send the sizes, colors and footage and our team replies within one business day.