SIS Wire

Additional Information

What is SIS Wire?

The term SIS wire refers to a range of single-core conductors with cross-linked polyethylene (XLPE) insulation, intended for use in electrical switchboards and panels with voltages up to 600v. NEC Table 310.104(A) defines type SIS as switchgear and switchboard wire with flame-retardant thermoset insulation suitable for continuous operation at temperatures up to 90°C. These constructions are dual-rated under several UL standards and comply with CSA SIS and CL1251 types.

What are the Intended Applications of SIS Wire?

SIS wire is designed exclusively for dry locations, where it is used to wire electrical switchgear, control panels, substations, and associated equipment. NEC categorizes SIS conductors from 14 AWG to 4/0 AWG with a maximum operating temperature of 90°C. Because 14 AWG is the smallest recognized SIS size, wires between 18 AWG and 14 AWG are typically marked “Suitable for switchboard use.”

SIS Wire for Panel Builders

Panel builders often use SIS wire for internal wiring in control panels, switchboards, relay panels, transformer panels, UPS controls, and power distribution equipment. For UL 508A panel shops, SIS wire supports organized wiring inside protected enclosures where correct gauge, color, insulation type, voltage rating, temperature rating, and product documentation matter.

SIS wire is commonly selected for switchboard and control panel applications because its XLPE insulation provides strong thermal stability and resistance to moisture, oils, chemicals, and hydraulic fluids. This makes it a practical option for demanding panel environments where engineers or shop leads may prefer SIS over standard PVC-insulated wire.

AWC supplies SIS wire in multiple sizes, colors, and constructions to support panel shop inventory, project-based builds, replacement needs, and repeat production work. Contact Allied Wire & Cable for help with SIS wire availability, cut-length needs, documentation, or product selection for your control panel, switchgear, UPS, relay, transformer, or distribution equipment application.

How is SIS Wire Constructed?

SIS wire features a single tinned copper conductor, offered in solid or stranded designs depending on the size. Constructions between 18 AWG and 12 AWG may be solid or stranded, while larger sizes are stranded only. The insulation is XLPE, a thermoset compound known for its durability, resistance to moisture, chemicals, and oils, and inherent flame-resistant properties. Most SIS constructions meet WV-1 fire test requirements.

SIS Dual Ratings

Many SIS wires carry additional UL ratings, including:

• UL 3173: Internal appliance wiring; 125°C; 600 volts; 26–9 AWG; must pass horizontal flame test.
• UL 3195: Internal wiring; applies only to 8 AWG conductors.
• UL 3196: Internal wiring; covers 7–2 AWG.
• UL 3320: Motor lead and internal appliance wiring; 30–2 AWG; 90°C; 600V AC continuous; insulation must withstand 2,500-volt surge; may be labeled “2,500 volts peak — for electronic use only.”

Does Allied Wire & Cable Carry Other SIS Wire Brands?

AWC also supplies SIS wire from Belden, including Belden SIS Hook-Up Wire.

SIS Wire Specifications

Contact us for assistance selecting SIS wire for your application..