Fixture Wire
NEC® Article 402, Table 402.3

F Fixture wire, standard stranding
FF Fixture wire, flexible stranding
G Glass braid
H 75°C insulation
HH 90°C insulation
K Aromatic polyimide tape insulation
N Nylon jacket
P Fluorinated ethylene propylene insulation
R Thermoset insulation
S Silicone (Thermoset) insulation
T Thermoplastic insulation
X Cross-linked synthetic polymer insulation
Z Modified tetrafluoroethylene insulation
-1, 2, 3 Insulation thickness, thinnest to thickest for some types. Actual insulation
thickness varies, with insulation types and AWG size.
Examples: SF-1–Silicone rubber fixture wire
TFF–Thermoplastic, flexible stranded fixture wire

Fixture Wire – NEC® Article 402, Table 402.3

Overview:
Fixture wire is a type of electrical wire designed for use in lighting fixtures, signs, and control circuits. The National Electrical Code (NEC®) defines different types of fixture wires based on insulation type, stranding, and temperature rating.

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Fixture Wire Designations and Meanings

The following codes are used to specify fixture wire properties:

Stranding Type:

• F – Standard stranding fixture wire.
• FF – Flexible stranding fixture wire.

Insulation Material:

• G – Glass braid insulation.
• H – 75°C temperature-rated insulation.
• HH – 90°C temperature-rated insulation.
• K – Aromatic polyimide tape insulation (high-temperature applications).
• N – Nylon jacket for additional protection.
• P – Fluorinated ethylene propylene (FEP) insulation.
• R – Thermoset insulation.
• S – Silicone-based (thermoset) insulation.
• T – Thermoplastic insulation.
• X – Cross-linked synthetic polymer insulation.
• Z – Modified tetrafluoroethylene (TFE) insulation.

Insulation Thickness Classification:

• -1, 2, 3 – Denotes insulation thickness, with "1" being the thinnest and "3" being the thickest for specific wire types. Actual thickness varies depending on insulation material and wire gauge.

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Examples of Fixture Wire Types:

• SF-1 – Silicone rubber fixture wire.
• TFF – Thermoplastic, flexible stranded fixture wire.

Fixture wires must comply with NEC® standards to ensure safety, proper insulation performance, and durability in lighting and control circuit applications.