UL 1331 FEP High Temperature Wire 20 AWG — 150°C at 600 Vac with a 2-mil Minimum FEP Covering Option
UL 1331 in 20 AWG is a single-conductor appliance wiring material with extruded FEP insulation, rated 150°C maximum at 600 Vac. At 20 AWG the base insulation falls in the style’s 30–10 AWG bracket at 20 mils minimum average thickness, 18 mils minimum at any point. Where this style differs from its FEP neighbours is the covering specification: UL 1331 permits an extruded FEP covering at 2 mils minimum thickness, against a 10 mils minimum in both UL 1330 and UL 1333. CableApex supplies UL 1331 20 AWG as a UL Recognized Component — file on record.
Why a 2-mil Covering Changes What Is Possible
A covering adds to the finished outside diameter on every side of the wire, so its minimum thickness sets a floor on how much the wire grows when a second layer is applied. At 10 mils minimum — the figure specified in the neighbouring FEP styles — adding a covering to a 20 AWG conductor is a meaningful dimensional change that has to be accounted for in harness fill, bushing sizing and termination hardware. At 2 mils minimum, the same second fluoropolymer layer can be applied with a fraction of that increase.
The practical consequences are threefold. A dual-layer FEP construction becomes viable on fine conductors where a 10-mil covering would push the wire outside its dimensional envelope. A contrasting-colour outer layer can be applied purely for circuit identification, using a thin covering rather than a full second wall, which is useful where a harness needs more colour combinations than the base insulation range provides. And where a modest increase in cut-through margin is wanted without the bulk or the friction change of a glass braid, the thin FEP covering supplies it while keeping the smooth low-friction outer surface that makes the wire easy to pull through passages.
Covering Minimums Across the Three FEP Styles
| Style | FEP covering minimum | Glass braid minimum | Base rating |
|---|---|---|---|
| UL 1331 (this page) | 2 mils | 7 mils | 150°C / 600 Vac |
| UL 1330 | 10 mils or heavier | 7 mils or heavier | 200°C / 600 Vac |
| UL 1333 | 10 mils | 7 mils | 150°C / 300 Vac |
UL 1331 20 AWG Specifications
| Item | Specification |
|---|---|
| UL Style | 1331 — single conductor with extruded insulation |
| Temperature Rating | 150°C maximum |
| Voltage Rating | 600 Vac |
| Conductor | 20 AWG, solid or stranded, or Litz cable conductor of R/C (OBMW2) magnet wire rated minimum 150°C (style range 30 AWG–4/0 AWG) |
| Insulation | Extruded FEP, 20 mils minimum average thickness, 18 mils minimum at any point |
| Optional Covering | Extruded FEP, 2 mils minimum thickness; or glass braid, 7 mils minimum thickness |
| Flame Rating | Horizontal flame; VW-1 vertical flame test available |
| Oil Rating | Optional — 60°C or 80°C oil resistant |
| Gasoline Resistance | Optional |
| UL Recognition | UL Recognized Component — file on record |
| Marking | Per UL Subject 758 marking requirements; Litz product additionally marked “Litz conductors are manufactured using solderable magnet wire” |
| Permitted Use | Internal wiring of appliances |
| RoHS / REACH | Documentation available on request |
Dual Oil Temperature Options
UL 1331 lists optional oil resistance at either 60°C or 80°C, where UL 1330 specifies a single 80°C oil option. Having two temperatures available matters when an appliance design has oil exposure in more than one zone at different thermal levels — a lower-temperature reservoir or drip area and a hotter compartment nearer a motor or element. Both can be served from the same style and the same 20 AWG gauge, with the tag marking reflecting the applicable rating for each. Optional gasoline resistance is available in addition. All optional ratings are specified at time of order rather than being standard on supplied product.
Applications
Within its permitted use — internal wiring of appliances — UL 1331 20 AWG suits internal control and signal conductors, sensor leads and light-duty power connections in appliances operating at 600 Vac in zones reaching 150°C. The thin FEP covering option makes this size practical where a dual-layer fluoropolymer construction or an added identification colour is wanted without a significant diameter penalty. In Litz construction the same gauge serves high-frequency winding leads. Where lubricant or fuel contact is expected, specify the applicable 60°C or 80°C oil rating or gasoline resistance. For applications outside internal appliance wiring, confirm application suitability before specifying.
Key Features
- FEP covering from 2 mils minimum — thinnest of the three FEP styles
- Dual-layer or colour-identification constructions with minimal diameter increase
- 150°C maximum at 600 Vac; FEP base wall 20 mils average at 20 AWG
- Optional oil resistance at either 60°C or 80°C, plus gasoline resistance
- Solid, stranded or Litz cable conductor construction available
- UL Recognized Component — file on record
Request a Quote
CableApex supplies UL 1331 20 AWG from 100 m per color and responds to B2B inquiries within 12 hours. Specify conductor construction (solid, stranded or Litz), base and covering colors, covering type and thickness, and any oil or gasoline requirements through the form below.
Other UL 1331 sizes: 18 AWG · UL 1330 FEP Wire (200°C / 600 Vac) · UL 1333 FEP Wire (150°C / 300 Vac)
