5.5 Flexible Cords & Fixture Wires (0405)

Flexible Cords & Fixture Wires (NEC Articles 400 and 402)

Quick Answer: Article 400 governs flexible cords and cables — permitted only for specific applications such as pendant fixtures, appliance drops, and movable equipment; it is never a substitute for fixed wiring. Article 402 governs fixture wires used inside luminaires and in raceways to wire fixtures. Both have their own ampacity tables (Table 400.5(A) for cords, Table 402.3 for fixture wires).

Permitted Uses of Flexible Cord — 400.10(A)

Flexible cords and cables may be used for:

1. Pendants — luminaires suspended by their cord.
2. Wiring of luminaires and the connection of utilization equipment designed for cord-and-plug connection.
3. Connection of movable equipment such as elevators, cranes, hoists, and trolleys.
4. Appliances designed or listed for cord connection.
5. Listed data processing cables and listed audio/video cables.
6. Connection of luminaires where the cord is visible and within 3 ft (900 mm) of the luminaire.
7. Temporary wiring per Article 590.

Prohibited Uses — 400.12

Flexible cord shall not be used:

1. As a substitute for the fixed wiring of a structure — 400.12(1).
2. Where run through holes in walls, structural ceilings, suspended or dropped ceilings, or floors — 400.12(2).
3. Where run through doorways, windows, or similar openings — 400.12(3).
4. Where attached to building surfaces — 400.12(4).
5. Where concealed by walls, floors, or ceilings, or located above suspended or dropped ceilings — 400.12(5).
6. Where installed in raceways, except as otherwise permitted in the Code — 400.12(6).
7. Where subject to physical damage — 400.12(7).

The first and fifth items are the ones an inspector writes up most often on a commercial job: a cord dropped through a ceiling tile to a workstation, or a cord stapled along a wall to reach a piece of equipment, is a fixed-wiring substitution and is a violation no matter how neatly it was done.

Permitted vs Prohibited — At a Glance

Cord Types — Table 400.4

Common cord types include S, SJ, SJO, SO, STO, SEO. The letters indicate insulation, jacket, and service rating:

• S — extra-hard usage, thermoset insulation and jacket, 600 V.
• SJ — junior hard service, 300 V; the "J" always means the 300 V junior class.
• SO / SEO / STO — extra-hard usage with an oil-resistant jacket; the middle letter identifies the jacket material (O oil-resistant thermoset, E thermoplastic elastomer, T thermoplastic).
• SJO / SJEO / SJTO — the same jacket options in the 300 V junior class.

Read the letters, not the trade name: an SJ-family cord in a location that calls for extra-hard usage — a stage, a shop, a portable sign — is a violation even though the cord looks robust.

The ampacity of each cord is found in Table 400.5(A); the type and configuration also limit use by temperature and dampness per Article 400.

Flexible Cord Ampacity

Use the ampacities in Table 400.5(A)(1) for 3-conductor cords or 400.5(A)(2) for 2-conductor cords. For example, an 18 AWG SJO cord has an ampacity of 7 A (3-conductor) and 16 AWG is 10 A. Cord selection must consider the appliance's marked current and the overcurrent protection per 240.5; the overcurrent device protecting the cord shall not exceed the cord's ampacity.

Overcurrent protection — 240.5

240.5(A) requires flexible cord to be protected by an overcurrent device in accordance with its ampacity from Table 400.5(A)(1) or (A)(2). 240.5(B) then lists the situations in which that protection is considered supplied by the branch-circuit device: 240.5(B)(1) covers the supply cord of a listed appliance or luminaire (the listing already coordinates cord and load); 240.5(B)(2) covers fixture wire; 240.5(B)(3) covers listed extension cord sets; and 240.5(B)(4) covers field-assembled extension cord sets. Where the appliance nameplate specifies a maximum overcurrent device, that rating controls. Protecting a cord with a device larger than the cord's ampacity, outside of those listed allowances, is a violation regardless of the appliance's marked current.

Fixture Wires — Article 402

Fixture wires are used inside or to wire luminaires and in raceways connecting fixtures. Types include:

• SF, SFF — silicone, fixture wire.
• TF, TFF — thermoplastic fixture wire.
• AF — asbestos fixture wire (largely historic; asbestos is prohibited for new work).
• RFH — rubber, fixture, high-temperature.
• KF, KFF — polyimide fixture wire for very high temperature.

Two different tables live in Article 402 and candidates swap them constantly: Table 402.3 lists the fixture-wire types, insulations, and permitted applications, while Table 402.5 gives the allowable ampacity:

402.6 sets 18 AWG as the minimum fixture-wire size. 402.12 covers overcurrent protection, and 240.5(B)(2) permits fixture wire to be tapped to a branch circuit of the rating listed there — 18 AWG up to 50 ft of run length on a 20 A circuit, 16 AWG up to 100 ft on a 20 A circuit, and 14 AWG and larger on branch circuits per the table.

Fixture wire installation — 402.6 through 402.11

402.10 Uses Permitted limits fixture wire to installation in luminaires and similar equipment where enclosed or protected and not subject to bending or twisting in use, and for connecting luminaires to the branch-circuit conductors supplying them. 402.11 Uses Not Permitted makes clear that fixture wire shall not be used as branch-circuit conductors except as permitted elsewhere in the Code. 402.7 governs the number of fixture wires in a conduit, by reference to the Chapter 9 tables. Match the fixture wire's temperature rating to the luminaire's marked supply-conductor temperature — a 90 °C conductor landed in a fixture marked for 150 °C supply conductors will cook.

Cord Length and Overcurrent Protection

Article 400 sets no general maximum cord length, and the exam will not ask for one. What it does ask is whether the use is permitted at all: a cord run from a receptacle to permanently installed equipment, through a wall, or above a ceiling is a fixed-wiring substitution under 400.12 regardless of length or gauge. Extension cords are a temporary convenience, not a wiring method; where cord-connected equipment is permanent, the correct correction is to install a branch circuit and an outlet at the equipment.

Inspector Focus

Verify: (1) flexible cord is used only for a 400.10(A) permitted use; (2) the cord is not run through walls or openings, concealed, or attached to building surfaces; (3) the cord type carries the right service class for the location (extra-hard usage where required) and its ampacity from Table 400.5(A)(1) covers the appliance's marked current; (4) fixture wire type comes from Table 402.3 and its ampacity from Table 402.5, with the temperature rating matching the luminaire marking; and (5) the overcurrent device protecting the cord is at or below the cord's ampacity, unless one of the 240.5(B) listed-assembly allowances applies.