10.4 Electrical Signs & Outline Lighting (Article 600)

Scope (600.1)

Article 600 covers electric signs and outline lighting, including fixed, stationary, and portable signs. The 2020 NEC added definitions and rules for retrofit kits — host signs, retrofit kits (general use), retrofit kits (sign-specific), and subassemblies — reflecting the growing practice of retrofitting existing signs with new lighting technology.

Definitions (600.2)

• Electric sign: A fixed, stationary, or portable electrically illuminated utilization equipment, sign, or outline lighting system — including neon, LED, and fluorescent.
• Outline lighting: An arrangement of incandescent, neon, LED, or other lamps, or electric-discharge tubing mounted on a building or other structure to outline a shape or call attention to a feature.
• Skeleton tubing: Neon or electric-discharge tubing that is field-installed, not part of a listed sign.
• Section sign: A sign with a listed subassembly that is field-assembled.
• Retrofit kit (new in 2020): A kit of components listed for retrofitting an existing host sign.

Disconnecting Means (600.6)

The disconnect for a sign, outline lighting system, or controller must isolate all ungrounded conductors of the sign or system and must not serve other loads. Per 600.6(A), the disconnect may be located in one of four ways:

1. (A)(1) At the point of entry — At the point where the feeder or branch circuit enters the sign enclosure, sign body, or pole.
2. (A)(2) Within sight — Within sight of the sign, or out of sight but capable of being locked in the open position per 110.25.
3. (A)(3) Within sight of the controller — Within sight of the sign controller (if applicable).
4. (A)(4) Remote location (new in 2020) — If located remote from the sign, sign body, or pole, the disconnect must be mounted at an accessible location available to first responders and service personnel, AND marked with a label at the sign location identifying it as the disconnect for that sign. The label must comply with 110.21(B).

Marking of the Disconnect (600.5(B), new in 2020)

The disconnecting means must be marked to identify the sign/outline lighting/controller it controls. Exception: an external disconnect mounted on the sign body, enclosure, pole, or controller is not required to identify the sign it controls.

Common Exam Traps on 600.6

• A sign disconnect that also feeds a receptacle or lighting circuit violates "shall not serve other loads."
• A disconnect out of sight of the sign must be lockable per 110.25 — locking by a padlock that the installer provides is acceptable only if the disconnect is listed or designed to accept it.
• A remote disconnect (the 2020 addition) requires a label at the sign identifying the disconnect location; otherwise first responders cannot find it.

Grounding and Bonding (600.7)

Signs, outline lighting, and their metal parts must be grounded per Article 250. The equipment grounding conductor must be sized per 250.122 and must be run with the circuit conductors. Bonding must ensure continuity between metal parts of the sign and the equipment grounding conductor. Exposed non-current-carrying metal parts likely to become energized must be bonded.

Field-Installed Skeleton Tubing (600.21)

Skeleton tubing is neon or electric-discharge tubing installed in the field, not as part of a listed sign. Key requirements:

• Listed components and tubing.
• Proper spacing and support per 600.21(C).
• The secondary circuit from the transformer/power supply must be run in listed neon tubing or GTO cable.
• The metal parts of the skeleton tubing system must be bonded.
• A disconnect must isolate the skeleton tubing system.

Transformers and Electronic Power Supplies (600.24, 600.32)

Rating and Sizing (600.24)

• Transformers and electronic power supplies for signs must be rated for the load — the secondary current and voltage must match the connected tubing load.
• The primary side must be protected by an overcurrent device rated not more than the transformer primary rating.
• The secondary open-circuit voltage must not exceed the rated value of the tubing and connectors.

Secondary-Circuit Ground-Fault Protection (600.23(B))

Section 600.23(B) requires secondary-circuit ground-fault protection on transformers and electronic power supplies used with signs and outline lighting — every type except those that supply Class 2 output circuits. The trigger is the equipment, not the branch-circuit rating and not whether the sign is outdoors: a 20A indoor neon sign needs it just as much as an outdoor one. Two exceptions apply: a transformer with an isolated ungrounded secondary whose open-circuit voltage is 7500 V or less, and a transformer with an integral porcelain or glass housing for the neon tubing that requires no field wiring of the secondary circuit.

• For outdoor signs and signs in damp or wet locations: GFCI protection on the secondary is required.
• The protective device must be listed for the purpose.
• Exception: where the secondary is not grounded and the listed transformer/power supply incorporates its own protection, an additional device may not be required.

A common exam scenario: a neon sign supplied by a transformer with a 10,000 V secondary. Because the open-circuit secondary voltage exceeds 7500 V, neither exception applies and secondary-circuit ground-fault protection is required — indoors or out. The protection senses a fault on the secondary side, which is where most sign fires start, and de-energizes the circuit.

Listing and Marking (600.4)

• Signs and outline lighting must be listed per 600.4(A) unless field-assembled skeleton tubing under 600.21.
• Marking per 600.4(D) — the 2020 NEC requires markings to be visible prior to servicing, not necessarily visible to the public. They may be on the back of the sign or inside the access panel.
• Required markings: manufacturer, voltage, current, input wattage, and the listing mark.
• Retrofit kits must be marked per 600.35.

Retrofit Kits (600.35, new in 2020)

A retrofit kit must be listed for use in the host sign. The kit must include instructions for installation, wiring methods, damaged-part inspection, and marking. The host sign must be inspected for damage before the retrofit kit is installed. Wiring methods must follow 600.33 (retrofit kit wiring).

Branch Circuit Sizing (600.5)

The branch circuit supplying a sign or outline lighting system must be sized for the continuous load — the sign is considered a continuous load per 422.10(A) if it operates for 3 hours or more. Branch circuit conductors must be sized at 125% of the sign load per 422.10(A). The overcurrent protection must also be rated for the continuous load.

Worked Example — Outdoor Sign Installation

A 120V outdoor neon sign on a 20A branch circuit is being installed on a building façade. Required steps:

1. Disconnect per 600.6 — either at the point of entry to the sign, within sight of the sign, or out of sight and lockable per 110.25. If located remotely (600.6(A)(4)), a label must be at the sign identifying the disconnect location. The disconnect must serve only the sign and isolate all ungrounded conductors.
2. Mark the disconnect per 600.5(B) — identify the sign it controls.
3. Grounding per 600.7 — the sign enclosure, transformer enclosure, and metal parts must be grounded per Article 250 with an EGC sized per 250.122.
4. Transformer per 600.24 — rated for the secondary load; primary overcurrent protection rated not more than the transformer primary rating.
5. Secondary-circuit ground-fault protection per 600.23(B) — required because the sign transformer does not supply a Class 2 output circuit and its open-circuit secondary voltage is above 7500 V.
6. Branch circuit sizing per 600.5 and 422.10(A) — conductors at 125% of the continuous sign load.
7. Listing and marking per 600.4 — sign listed, manufacturer's nameplate with voltage, current, and wattage, visible prior to servicing.