UL 1333 FEP Hook-Up Wire 22 AWG — 150°C at 300 Vac, with a Litz Definition That Differs from Its Neighbour
UL 1333 in 22 AWG is a single-conductor appliance wiring material with extruded FEP insulation, rated 150°C maximum at 300 Vac, with a uniform 13 mils minimum average wall and 12 mils minimum at any point. Alongside conventional solid and stranded construction, the style permits Litz cable magnet wire — but the way UL 1333 defines that construction is not the same as the definition used in UL 1331, and the difference is worth understanding before either style is specified. CableApex supplies UL 1333 22 AWG as a UL Recognized Component — file on record.
Each Strand Is a Conductor
UL 1333 states its Litz construction directly: the Litz cable conductor consists of single-strand magnet wire, Recognized Component magnet wire (OBMV2) rated at a minimum of 150°C, and each single magnet wire strand is a conductor. UL 1331 words the same construction differently — there the individual strands are cabled together to form a conductor. The physical article in both cases is a bundle of individually enamelled fine magnet wire strands, but the framing differs in what the style treats as the conductor unit, and consequently in how the assembly is described and verified.
What follows from this in practice is the same in both styles and worth stating plainly: because every strand carries its own enamel film rather than being bare copper, the effective AWG of the finished conductor cannot be established by measuring a diameter. UL 1333 specifies that the AWG size is to be determined by the DC Resistance Test per UL 1581. That test measures what the conductor actually does electrically, which is the only meaningful basis for sizing a conductor made of many insulated elements. When ordering Litz-conductor product, the target effective AWG should be stated as a resistance-verified figure rather than assumed from strand count alone.
Litz Construction Compared Across the Two Styles
| Aspect | UL 1333 (this page) | UL 1331 |
|---|---|---|
| Style wording | Each single magnet wire strand is a conductor | Strands cabled together to form a conductor |
| Magnet wire category | R/C (OBMV2), minimum 150°C | R/C (OBMW2), minimum 150°C |
| AWG determination | DC Resistance Test per UL 1581 | DC Resistance Test |
| Insulation wall | 13 mils avg / 12 mils min | 20 mils avg / 18 mils min |
| Voltage rating | 300 Vac, 600 V peak tag available | 600 Vac |
| Mandatory Litz marking | Yes, on tag or reel | Yes, on tag or reel |
Solderable Magnet Wire and Termination
The mandatory marking applied to Litz product under this style — “Litz conductors are manufactured using solderable magnet wire” — is not merely a traceability note. It records a property that determines how the lead is terminated. Solderable magnet wire carries an enamel formulated to break down at soldering temperature, so the strands can be tinned directly without the strand-by-strand mechanical or chemical stripping that non-solderable enamels require. On a 22 AWG Litz lead with a high strand count, that difference is the difference between a practical production termination and one that is not viable at volume. Confirm the intended termination method when ordering, since it affects how the lead ends should be prepared and supplied.
UL 1333 22 AWG Specifications
| Item | Specification |
|---|---|
| UL Style | 1333 — single conductor with extruded insulation |
| Temperature Rating | 150°C maximum |
| Voltage Rating | 300 Vac; tag may also indicate 600 Volts Peak for electronic use only |
| Conductor | 22 AWG, solid or stranded, or Litz cable magnet wire, R/C (OBMV2) rated minimum 150°C (style range 30–10 AWG) |
| Litz AWG determination | By DC Resistance Test per UL 1581 |
| Insulation | Extruded FEP, 13 mils minimum average thickness, 12 mils minimum at any point |
| Optional Covering | Extruded FEP, 10 mils minimum at any point; or glass braid, 7 mils minimum at any point |
| Flame Rating | Horizontal flame; VW-1 vertical flame test available |
| Oil Rating | Optional — 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 |
Applications
Within its permitted use — internal wiring of appliances — UL 1333 22 AWG in Litz construction suits lead-out wiring for high-frequency transformer and inductor windings where the thin 13 mils wall keeps the lead compact at the bobbin exit and the solderable magnet wire allows direct tinned termination onto a board. In solid or stranded construction the same gauge serves general hook-up and control wiring in dense internal harnesses at 300 Vac, or in electronic circuits where the 600 V peak tag applies. Optional 80°C oil resistance and optional gasoline resistance are available where lubricant or fuel contact is expected. For applications outside internal appliance wiring, confirm application suitability before specifying.
Key Features
- Litz cable magnet wire construction with each strand recognised as a conductor
- Effective AWG determined by DC Resistance Test per UL 1581
- Solderable magnet wire permits direct tinned termination at high strand counts
- 13 mils thin wall keeps Litz leads compact at bobbin and connector exits
- 300 Vac base rating with optional 600 V peak electronic use tag
- UL Recognized Component — file on record
Request a Quote
CableApex supplies UL 1333 22 AWG from 100 m per color and responds to B2B inquiries within 12 hours. For Litz construction, state the target effective AWG, the operating frequency range and the intended termination method; for solid or stranded, state construction, colors and covering option. Include the 600 V peak tag and any oil or gasoline requirements in your inquiry below.
Other UL 1333 sizes: 20 AWG · UL 1331 FEP Wire (150°C / 600 Vac, Litz) · UL 1330 FEP Wire (200°C / 600 Vac)
