UL1591 FEP Wire

UL 1591 FEP Wire — 150°C, 300 Vac Fine-Gauge Appliance Wiring with Plated Conductor Options

UL 1591 is a single-conductor appliance wiring material with extruded FEP insulation, rated 150°C maximum at 300 Vac with a horizontal flame rating, evaluated under UL Subject 758. It covers conductor sizes from 32 AWG through 16 AWG in solid or stranded construction, with a single insulation specification of 16 mils minimum average thickness and 13 mils minimum at any point applied across the whole range. What sets this style apart within the FEP family is the conductor: UL 1591 explicitly recognises silver plated conductor, nickel coated copper conductor, and nickel or tin plated conductor alongside plain copper. CableApex supplies UL 1591 as a UL Recognized Component — file on record.

A Fine-Gauge Style with a Defined Upper Limit

The 32 AWG to 16 AWG span places UL 1591 firmly in fine-gauge territory. It does not extend into the heavy conductors covered by UL 1330 or UL 1331, both of which run to 4/0 AWG. That narrower scope is reflected in the insulation: one wall figure rather than a bracket table, because the conductor range is tight enough not to require one. For designers, the practical effect is that any gauge within the style carries the same 16 mils nominal wall, so the finished diameter varies only with the conductor itself.

Why Conductor Plating Is Specified in This Style

Bare copper oxidises, and at elevated temperature it oxidises faster. In a wire rated to 150°C and expected to remain terminable and electrically stable over a long service life, the surface condition of the conductor matters as much as its cross-section. UL 1591 addresses this by recognising four conductor treatments within the style description.

Silver plated conductor offers the lowest contact resistance of the group and excellent solderability, and is the traditional choice for high-frequency and RF-adjacent circuits where surface conductivity governs. Nickel coated copper trades some conductivity for markedly better oxidation resistance at sustained high temperature, and is the usual selection where the lead sits at the upper end of the temperature range for extended periods. Nickel plated conductor serves a similar purpose. Tin plated conductor is the general-purpose option: it protects the copper surface, keeps the conductor readily solderable with standard process chemistry, and is the most economical of the four. The correct choice depends on the termination method, the operating temperature the lead actually sees, and whether contact resistance is critical to the circuit — state the requirement at time of order.

UL 1591 Alongside UL 1592

UL 1591 has a close counterpart in UL 1592. The two share the same 32 AWG to 16 AWG conductor range, the same 300 Vac rating, and the same 16 mils minimum average FEP wall. They differ in two respects. UL 1592 is rated 200°C against 150°C here, and it constrains tinned copper conductor to 26 AWG through 16 AWG with a minimum strand diameter of 15 mils, where UL 1591 places no such restriction on its plating options. Where the design needs the full 200°C class, UL 1592 is the style; where 150°C is sufficient and conductor plating flexibility across the full 32 AWG range matters, UL 1591 is the closer match.

Permitted Use and Ordering

The permitted use for UL 1591 is internal wiring of appliances. For applications outside internal appliance wiring, confirm application suitability before specifying. Marking follows UL Subject 758 marking requirements, and RoHS/REACH documentation is available on request. CableApex supplies UL 1591 from 100 m per color, in solid or stranded construction with the conductor plating specified at order, and answers B2B inquiries within 12 hours with pricing, lead time and packing details. Browse the UL 1591 products below by AWG size, or submit your specification through any product page inquiry form.