19.1 Signs & Outline Lighting, Office Partitions, IT Rooms & Irrigation Machines (Articles 600, 605, 645 & 675)
Key Takeaways
Branch circuits supplying signs and outline lighting are limited to 20 A, except circuits supplying only neon tubing installations, which may be rated up to 30 A (600.5(B)).
Each sign must have a disconnecting means that opens all ungrounded conductors and is within sight of the sign, or lockable in the open position if not within sight (600.6).
Cord-and-plug connected freestanding office partitions may use a single extra-hard-usage cord of 12 AWG or larger, not over 2 ft long, supplying no more than thirteen 15 A, 125 V receptacles and no multiwire circuits (605.9).
In an information technology room qualifying under Article 645, a disconnecting means for the ITE and the dedicated HVAC must be controllable from a readily accessible location at the principal exit doors (645.10).
A center-pivot irrigation machine needs a grounding electrode system connected to the machine at its stationary point for lightning protection (675.15).
Electric signs and outline lighting (Article 600)
Branch circuits (600.5)
- Required sign outlet: each commercial building and each commercial occupancy accessible to pedestrians must have at least one sign outlet in an accessible location at each entrance to each tenant space, supplied by a branch circuit rated at least 20 A that supplies no other load. Service hallways and corridors used only for service are not considered entrances.
- Ratings: branch circuits supplying neon tubing installations may be rated up to 30 A; circuits supplying all other signs and outline lighting may be rated up to 20 A.
- Load: each required sign outlet counts at least 1,200 VA in the load calculation (120.14(F)).
Disconnecting means (600.6)
| Rule | Requirement |
|---|---|
| Required | Each sign and outline lighting system, or feeder or branch circuit supplying it, must have an externally operable disconnecting means that opens all ungrounded conductors and controls no other load |
| Location | At the point where the supply enters the sign enclosure or sign body, or within sight of the sign; where not within sight, the disconnect must be lockable in the open position (110.25) |
| Control switch rating (600.6(B)) | Switches, flashers, and similar devices controlling transformers and power supplies must be rated for inductive loads, or have an ampere rating at least twice the ampere rating of the transformer |
Ballasts, transformers, and power supplies
- Attics and soffits (600.21(E)): permitted where there is an access door at least 3 ft by 22½ in., and a passageway at least 3 ft high by 2 ft wide with a suitable permanent walkway at least 12 in. wide from the point of entry to each component.
- Suspended ceilings (600.21(F)): permitted above suspended ceilings if the enclosures are securely fastened in place and do not depend on the ceiling grid for support; they may not be connected to the branch circuit by flexible cord.
- Accessibility: ballasts, transformers, and electronic power supplies must be accessible and securely fastened in place.
Neon secondary wiring over 1000 V (600.32)
Neon secondary circuit conductors must be listed and insulated for the voltage and installed in raceway or listed for the use. The length of secondary conductors from the high-voltage terminal of the transformer or power supply to the first neon tube electrode may not exceed 20 ft in metal conduit or tubing, or 50 ft in nonmetallic conduit.
Other sign rules
- Signs must be listed and marked with the manufacturer, voltage, and current (600.3 and 600.4).
- Metal parts of signs and outline lighting must be grounded and bonded (600.7), and remote metal parts are bonded with listed bonding means.
- Signs and outline lighting located where they could be struck by vehicles must be at least 14 ft above areas accessible to vehicles, unless protected from physical damage (600.9).
Office furnishings (Article 605)
Article 605 covers electrical equipment, lighting accessories, and wiring systems used to connect, or contained within, office furnishings such as wired partitions.
Cord-and-plug connected freestanding partitions (605.9): individual partitions, or groups of interconnected partitions not exceeding 30 ft when assembled, may be connected to the building wiring by a single flexible cord and plug only if all of these are met:
- the cord is extra-hard usage, 12 AWG or larger, with an insulated EGC, and not longer than 2 ft;
- the receptacle supplying it is on a separate circuit serving only panels, with no other loads, and is located not more than 12 in. from the partition it connects to;
- the partitions contain not more than thirteen 15 A, 125 V receptacle outlets; and
- the partitions contain no multiwire circuits.
Partitions that are permanently connected to the building wiring use a Chapter 3 wiring method.
Information technology equipment rooms (Article 645)
Article 645 provides optional alternative wiring rules for an ITE room that meets all the conditions of 645.4: a disconnecting means complying with 645.10; a dedicated HVAC system or one with fire and smoke dampers; listed information technology equipment; occupation only by personnel needed to operate and maintain the equipment; and separation from other occupancies by fire-resistant-rated walls, floors, and ceilings with protected openings.
| Rule | Requirement |
|---|---|
| Branch circuits (645.5) | Conductors supplying one or more ITE units must have an ampacity of at least 125% of the total connected load |
| Power-supply cords | ITE may be connected by listed cords; flexible cords and interconnecting cables run under a raised floor must be listed for the use |
| Under raised floors (645.5(E)) | Branch circuits in raceways or listed cables, with the space under the floor accessible and used for wiring; ventilation of the underfloor area limited to the ITE room |
| Disconnecting means (645.10) | Remote disconnect controls for the ITE and the dedicated HVAC systems, located at an approved location readily accessible at the principal exit doors; a single means may control both; critical operations data systems may use alternative arrangements |
| Grounding (645.15) | All exposed non-current-carrying metal parts of the ITE system must be connected to an EGC, and signal reference structures bonded |
Electrically driven or controlled irrigation machines (Article 675)
Center-pivot and lateral-move irrigation machines are common on Minnesota farms. Article 675 covers machines with electrically driven towers or electric controls.
| Rule | Requirement |
|---|---|
| Ratings (675.7) | The machine's conductors and controller are sized from an equivalent continuous-current rating based on the motor loads and their duty cycle |
| Main controller and disconnect (675.8) | A main controller, plus a main disconnecting means at the point where power connects to the machine, or within sight and not more than 50 ft from the machine; the disconnect must be readily accessible and lockable in the open position, with a horsepower rating at least equal to the equivalent rating |
| Grounding (675.12) | The electrical equipment on the machine, its junction boxes, control panels, and motor enclosures must be connected to an EGC |
| Methods of grounding (675.13) | A machine with a stationary point (center pivot) is grounded by an EGC run with the supply conductors and connected to an equipment grounding terminal at the stationary point |
| Bonding (675.14) | The machine's metallic structure and metal conduit or cable sheaths are connected to the EGC; metal-to-metal contact with a part connected to the EGC is an acceptable bonding path |
| Lightning protection (675.15) | Where the machine has a stationary point, a grounding electrode system (Article 250, Part III) is connected to the machine at the stationary point |
Worked example: a retail tenant sign
A new retail tenant needs a 6 A LED channel-letter sign above its entrance.
- The required sign outlet at the tenant entrance is on a 20 A circuit that supplies no other load.
- The sign's disconnect is at the sign or within sight of it; if the switch is inside the store and out of sight, it must be lockable.
- The LED power supplies mounted above a suspended ceiling must be fastened to the structure, not hung from the grid.
What is the maximum rating of a branch circuit supplying an LED (non-neon) sign under 600.5(B)?
15 A
30 A
40 A
20 A
A group of freestanding office partitions is cord-and-plug connected under 605.9. What is the maximum length of the supply cord?
2 ft
12 in.
6 ft
15 ft
What does 675.15 require at the stationary point of a center-pivot irrigation machine?
A GFCI receptacle at the pivot point
A surge arrester on the incoming supply only
A grounding electrode system for lightning protection
A separate utility service dedicated to the machine
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