UL1333 FEP Wire

UL 1333 FEP Wire — 150°C, 300 Vac Thin-Wall Appliance Wiring with Litz Conductor Option

UL 1333 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 30 AWG through 10 AWG in solid or stranded construction, and uniquely among the FEP appliance wiring styles CableApex supplies, it also permits Litz cable magnet wire as a recognised conductor construction. The insulation is a single thin-wall specification — 13 mils minimum average, 12 mils minimum at any point — applied uniformly across the full conductor range. CableApex supplies UL 1333 as a UL Recognized Component — file on record.

The Thin-Wall FEP Position: 300 Vac at 150°C

UL 1333 is the lightest-wall member of the FEP appliance wiring group. At 13 mils minimum average, its insulation is roughly two-thirds the thickness of UL 1330 in the comparable 30–10 AWG bracket, which carries 20 mils. That reduction is deliberate: at 300 Vac rather than 600 Vac, the dielectric requirement is lower, and the thinner wall produces a smaller finished outside diameter and a lighter, more flexible conductor. In dense internal harnesses where dozens of conductors share a routing channel, or in equipment where wire mass matters, the thin-wall construction is often the reason UL 1333 is specified over a heavier-wall 600 V style that the circuit does not actually require.

Litz Cable Magnet Wire Construction

The Litz conductor option sets UL 1333 apart. A Litz conductor under this style consists of single-strand magnet wire — Recognized Component magnet wire (OBMV2) rated at a minimum of 150°C — where each individual magnet wire strand counts as a conductor in its own right. Because the strands are individually insulated by the magnet wire enamel rather than bundled bare, the effective AWG size is not determined by physical measurement but by the DC Resistance Test in accordance with UL 1581. Litz construction is chosen where high-frequency current is present: by subdividing the conductor into many individually insulated strands, it reduces the skin-effect and proximity-effect losses that degrade performance in transformer windings, induction heating coils, and switching power supply magnetics operating well above line frequency.

Wires supplied with Litz conductors carry an additional mandatory marking requirement. The tag or reel must be plainly marked: “Litz conductors are manufactured using solderable magnet wire.” This marking is not optional and is applied to all Litz-conductor product under this style.

Insulation, Covering and Tag Options

The extruded FEP insulation is specified at 13 mils minimum average thickness with 12 mils minimum at any point, applied uniformly from 30 AWG through 10 AWG — there is no wall-thickness bracket table in this style. An optional covering may be applied: either extruded FEP at 10 mils minimum thickness at any point, or a glass braid at 7 mils minimum, the latter adding abrasion resistance where the wire is drawn through tight passages or contacts sheet-metal edges. Optional 80°C oil resistance and optional gasoline resistance are available, and the tag may additionally indicate 600 Volts Peak for electronic use only where the internal circuit operates at elevated peak voltages. All optional ratings and markings are specified at time of order.

UL 1333 Among the FEP Appliance Wiring Styles

The FEP styles CableApex supplies differ chiefly in the combination of temperature rating, voltage rating and insulation wall. UL 1330 is the 200°C / 600 Vac member, covering 30 AWG through 4/0 AWG with a three-bracket wall table and the option of gasoline immersion resistance. UL 1333 sits at 150°C / 300 Vac with a single 13 mils thin wall over a narrower 30–10 AWG range, adding the Litz conductor option and the 600 V peak electronic tag. Where the design needs the higher temperature or the 600 Vac insulation class, UL 1330 is the appropriate style; where the circuit is 300 Vac or below and either thin-wall flexibility or Litz construction matters, UL 1333 is the closer match.

Permitted Use and Ordering

The permitted use for UL 1333 is internal wiring of appliances; tags may additionally indicate 600 Volts Peak for electronic use only. For applications outside internal appliance wiring, confirm application suitability before specifying. Marking follows UL Subject 758 marking requirements, with the additional mandatory Litz marking where Litz conductors are supplied. RoHS/REACH documentation is available on request. CableApex supplies UL 1333 from 100 m per color, in solid, stranded or Litz conductor construction, with or without the optional FEP or glass braid covering, and answers B2B inquiries within 12 hours with pricing, lead time and packing details. Browse the UL 1333 products below by AWG size, or submit your specification through any product page inquiry form.