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Solid THHN/THWN-2 WireFrom $0.20/ft -
Solid THHN/THWN-2 WireFrom $0.20/ft - Solid THHN/THWN-2 WireFrom $0.20/ft
- Solid THHN/THWN-2 WireFrom $0.20/ft
Parent SKU : 18SIS-3173
SKU : 18SIS-3173-500-BK
"The professional standard for high-density control panels—engineered with high-performance XLPE insulation and tinned copper for maximum reliability in environments up to 125°C."
The 18 AWG SIS wire is a specialized high-temperature conductor designed for precision electrical systems, fully compliant with UL 3173 standards. It is the primary choice for utility-scale switchgear, industrial control panels, and transformer leads. Our Cross-linked Polyethylene (XLP) insulation is thermoset, meaning it provides superior resistance to melting or deformation even when exposed to high-thermal stress or accidental contact with soldering equipment.
125°C Heat Resistance: Rated for continuous use in extreme thermal environments where standard building wire (90°C) fails.
Tinned Copper Conductor: Features a tin coating over the stranded copper to prevent corrosion and ensure effortless soldering and termination in high-humidity panels.
Chemically Cross-Linked (XLP): The insulation is chemically bonded to ensure it maintains structural integrity under extreme heat.
UL 3173 / CSA CL1251 Rated: Fully compliant with industrial standards for switchgear, control circuits, and internal appliance wiring.
ENGINEERING OVERVIEW: 18 AWG SIS UL 3173 600V
APPLICATION: Internal wiring of switchboards, control panels, and power distribution equipment.
VOLTAGE: Rated for 600 Volts.
CONDUCTORS: 16-strand soft drawn tinned coated copper per ASTM B33 and B174.
INSULATION: Cross-linked polyethylene (XLP), Type SIS.
TEMPERATURE: 125°C (257°F).
NOMINAL OD: 0.111 inches (2.82 mm).
Electrical Switchgear: The primary choice for internal wiring of utility-scale substations and distribution panels.
Control & Relay Panels: Ideal for high-density wiring of industrial relays, contactors, and terminal blocks.
Motor & Transformer Leads: Used for internal coil leads and motor connections that operate at elevated temperatures.
Commercial Lighting: A popular choice for high-intensity discharge (HID) or specialized industrial lighting fixtures.
Industrial Computers: Providing stable power and signal within heavy-duty manufacturing computer cabinets.
Technical Note: All values are nominal and subject to industry tolerances and manufacturer corrections. Specifications are subject to change without notice. It is the buyer’s responsibility to verify that all materials meet the specific requirements of the project and comply with local electrical codes.
| Wire Size (AWG/MCM) | 18 AWG |
| Conductor Material | Tinned Copper |
| Conductor Type | Stranded |
| Strand Count | 16 |
| Outer Diameter (OD) (in/mm) | 0.111 in. / 2.82 mm |
| Conductor Count | 1 |
| Shield | Unshielded |
| Insulation Type | XLPE |
| UL Listing Numbers | UL 3173 |
| Voltage Rating | 600V |
| Submersible | No |
| Temperature Rating | 125ºC |
| Standards | UL Type AWM Style 3173 CSA CL1251 UL Horizontal Flame Test CSA FT2 Flame Test |
| Miscellaneous Information | All values are nominal and subject to correction. |
| Primary Applications | Switchboards, Control and Power Circuits, Applications up to 125° and 600 volts. |
| Common Uses |
|
| Weight per Foot | 0.01 lb |
In-stock orders placed before 3pm EST typically ship within 1-2 business days. Our business days are Monday through Friday; we do not process orders on Saturday, Sunday, or major US Holidays.
You will receive an e-mail with a tracking number within 1-2 business days from the time its shipped. You will also be able to view your order status and tracking numbers in your account order history.
Expedited shipments are delivered Monday-Friday except on US Holidays. The order must be placed before 12pm CST to ship same day ( Mon-Fri Only).
You have 30 days from the day you receive the item to contact us for a return. Returns are subject to a 30% Restocking Fee.
Please contact us at help@wireamerica.com to request a return authorization. Have your order number or name the order was placed with ready and we will email you an RMA (return) number and instructions for return. Currently, we do not offer exchanges. A new order must be placed if you need a different item. If you provide the new order number at the time of your return request, the restocking fee may be lowered.
Orders on any items with a material value of $50 or less are non-returnable.
Parent SKU : 18SIS-3173
SKU : 18SIS-3173-500-BK
Parent SKU : 18SIS-3173
SKU : 18SIS-3173-500-BK
"The professional standard for high-density control panels—engineered with high-performance XLPE insulation and tinned copper for maximum reliability in environments up to 125°C."
The 18 AWG SIS wire is a specialized high-temperature conductor designed for precision electrical systems, fully compliant with UL 3173 standards. It is the primary choice for utility-scale switchgear, industrial control panels, and transformer leads. Our Cross-linked Polyethylene (XLP) insulation is thermoset, meaning it provides superior resistance to melting or deformation even when exposed to high-thermal stress or accidental contact with soldering equipment.
125°C Heat Resistance: Rated for continuous use in extreme thermal environments where standard building wire (90°C) fails.
Tinned Copper Conductor: Features a tin coating over the stranded copper to prevent corrosion and ensure effortless soldering and termination in high-humidity panels.
Chemically Cross-Linked (XLP): The insulation is chemically bonded to ensure it maintains structural integrity under extreme heat.
UL 3173 / CSA CL1251 Rated: Fully compliant with industrial standards for switchgear, control circuits, and internal appliance wiring.
ENGINEERING OVERVIEW: 18 AWG SIS UL 3173 600V
APPLICATION: Internal wiring of switchboards, control panels, and power distribution equipment.
VOLTAGE: Rated for 600 Volts.
CONDUCTORS: 16-strand soft drawn tinned coated copper per ASTM B33 and B174.
INSULATION: Cross-linked polyethylene (XLP), Type SIS.
TEMPERATURE: 125°C (257°F).
NOMINAL OD: 0.111 inches (2.82 mm).
Electrical Switchgear: The primary choice for internal wiring of utility-scale substations and distribution panels.
Control & Relay Panels: Ideal for high-density wiring of industrial relays, contactors, and terminal blocks.
Motor & Transformer Leads: Used for internal coil leads and motor connections that operate at elevated temperatures.
Commercial Lighting: A popular choice for high-intensity discharge (HID) or specialized industrial lighting fixtures.
Industrial Computers: Providing stable power and signal within heavy-duty manufacturing computer cabinets.
Technical Note: All values are nominal and subject to industry tolerances and manufacturer corrections. Specifications are subject to change without notice. It is the buyer’s responsibility to verify that all materials meet the specific requirements of the project and comply with local electrical codes.
| Wire Size (AWG/MCM) | 18 AWG |
| Conductor Material | Tinned Copper |
| Conductor Type | Stranded |
| Strand Count | 16 |
| Outer Diameter (OD) (in/mm) | 0.111 in. / 2.82 mm |
| Conductor Count | 1 |
| Shield | Unshielded |
| Insulation Type | XLPE |
| UL Listing Numbers | UL 3173 |
| Voltage Rating | 600V |
| Submersible | No |
| Temperature Rating | 125ºC |
| Standards | UL Type AWM Style 3173 CSA CL1251 UL Horizontal Flame Test CSA FT2 Flame Test |
| Miscellaneous Information | All values are nominal and subject to correction. |
| Primary Applications | Switchboards, Control and Power Circuits, Applications up to 125° and 600 volts. |
| Common Uses |
|
| Weight per Foot | 0.01 lb |
In-stock orders placed before 3pm EST typically ship within 1-2 business days. Our business days are Monday through Friday; we do not process orders on Saturday, Sunday, or major US Holidays.
You will receive an e-mail with a tracking number within 1-2 business days from the time its shipped. You will also be able to view your order status and tracking numbers in your account order history.
Expedited shipments are delivered Monday-Friday except on US Holidays. The order must be placed before 12pm CST to ship same day ( Mon-Fri Only).
You have 30 days from the day you receive the item to contact us for a return. Returns are subject to a 30% Restocking Fee.
Please contact us at help@wireamerica.com to request a return authorization. Have your order number or name the order was placed with ready and we will email you an RMA (return) number and instructions for return. Currently, we do not offer exchanges. A new order must be placed if you need a different item. If you provide the new order number at the time of your return request, the restocking fee may be lowered.
Orders on any items with a material value of $50 or less are non-returnable.
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Physical Specifications
Technical Specifications
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SIS wire is the industry standard for high-performance internal wiring. Its primary applications include the internal circuitry of electrical switchgear, control panels, and distribution boards. Because of its 125°C temperature rating and resistance to oils and chemicals, it is also widely used for transformer leads, industrial motor starters, and relay logic systems in utility substations. It is the preferred choice for any environment where high-density wiring requires both flexibility and superior heat resistance.
SIS Switchboard wire is rated for 125°C (257°F). This makes it significantly more heat-resistant than standard THHN wire (90°C). It is specifically designed to maintain its electrical integrity in the "hot zones" inside electrical cabinets and industrial machinery.
Yes. Because SIS uses Cross-linked Polyethylene (XLP) insulation, it is inherently resistant to moisture, oils, and various industrial chemicals. While it is perfect for damp environments inside panels, it is not intended for direct burial or submersion in water.
The two main differences are heat and flexibility. SIS is rated for 125°C, while THHN is limited to 90°C. Additionally, SIS features Tinned Copper and XLP insulation, which is more flexible and "dead-soft" compared to the stiffer PVC/Nylon jacket of THHN, making SIS much easier to route in tight control clusters.
Yes. Our 18 AWG SIS wire is fully certified to UL Type AWM Style 3173, ensuring it meets rigorous safety and performance standards for switchboard and control circuit applications.
The tin coating protects the copper from oxidation (turning green), which is common in high-heat or high-humidity environments. Tinned copper also makes the wire much easier to solder and provides a superior connection when used with crimp-on terminals.
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