Signs, elevators and other special equipment

Chapter 6 of the NEC covers special equipment: electric signs, elevators and escalators, welders, information technology equipment, industrial machinery, cranes, X-ray equipment, induction heating, fire pumps and more. Each article modifies the general rules for equipment whose use or construction creates particular needs. Master exams pick a handful of these, usually the ones with a distinctive calculation or a distinctive disconnect rule. This lesson covers signs in Article 600, elevators in Article 620, welders in Article 630, information technology equipment rooms in Article 645, industrial machinery in Article 670, and a quick tour of other Chapter 6 articles, with a calculation for each where the article has one. Sections are cited by number and explained in our own words; values in examples are illustrative.

A sign, a crane and a welding bay

Brightwater's projects are converging. The Copper Kettle wants an illuminated sign for the banquet room's new entrance. Delgado Fabrication is adding a welding bay with four transformer arc welders and a small overhead bridge crane over the steel rack. And the Maple Street fourplex owner is pricing an elevator so tenants on the third floor can move furniture more easily. 'Chapter 6 is where the equipment people live,' Ray says. 'Each article has one or two numbers you need to know cold, and the rest you look up.'

Electric signs under Article 600

Article 600 covers electric signs and outline lighting, including neon, LED and fluorescent signs and the sections of buildings outlined with lighting. All signs and outline lighting systems must be listed and installed in conformance with the listing, under 600.3, unless they are field-assembled from listed components following the manufacturer's instructions. The most frequently tested rule is the sign outlet in section 600.5: each commercial building and each commercial occupancy accessible to pedestrians must have at least one outlet in an accessible location at each entrance to each tenant space for sign or outline lighting system use. The outlet must be supplied by a branch circuit rated at least 20 amperes that supplies no other load. For load calculations, section 220.14(F), in the 2023 edition, requires each such sign outlet to be counted at a minimum of 1,200 volt-amperes, a number that appears on exams often.

Section 600.5(B) also limits the rating of branch circuits that supply signs: circuits supplying signs with incandescent and fluorescent forms of illumination are limited to a stated rating, commonly 20 amperes, and circuits supplying only neon tubing installations are limited to a higher rating, commonly 30 amperes. Section 600.6 requires each sign and outline lighting system, or feeder circuit or branch circuit supplying a sign, to be controlled by an externally operable switch or circuit breaker that opens all ungrounded conductors and controls no other load. The disconnect must be within sight of the sign, or capable of being locked in the open position. Metal parts of signs must be bonded, and signs in wet locations must be suitable for the location.

Elevators and escalators under Article 620

Article 620 covers elevators, dumbwaiters, escalators, moving walks, platform lifts and stairway chairlifts. It works closely with ASME A17.1, the safety code for elevators, and the building and fire codes. The main exam topics are disconnecting means, separate branch circuits for car and machine room lighting, GFCI protection, selective coordination and standby power.

Section 620.51 requires a single means for disconnecting all ungrounded main power supply conductors for each elevator, located where it is readily accessible to qualified persons, and capable of being locked in the open position. The disconnect must be a fused motor circuit switch or a circuit breaker, it must not open the car lighting, receptacle and ventilation circuits, and it is commonly located inside the machine room or control room, within sight of the motor controller. Where sprinklers are installed in the hoistway, machine room or control room, a means is required to automatically disconnect the main power supply before the sprinklers discharge, commonly a shunt-trip breaker triggered by a heat detector, as the elevator code requires.

Separate branch circuits are required for the car lighting, receptacles, ventilation and accessories under 620.22; for the machine room and control room lighting and receptacles under 620.23; and for the hoistway pit lighting and receptacles under 620.24, so that a fault on the elevator power does not leave a technician in the dark. Section 620.85 requires GFCI protection for 125-volt, single-phase, 15- and 20-ampere receptacles in pits, in hoistways, on the cars of elevators and in escalator and moving walk wellways, and in machine rooms and control rooms in many cases. A dedicated receptacle for a sump pump in the pit is treated differently in some editions. Section 620.62 requires selective coordination where more than one driving machine disconnecting means is supplied by a single feeder, so that a fault in one elevator does not shut down all of them.

Welders under Article 630

Welders draw large currents for short periods, so Article 630 lets the supply conductors be sized for the welder's duty cycle rather than its full rated current. For individual transformer arc welders, section 630.11(A) requires the supply conductors to have an ampacity not less than the effective primary current marked on the nameplate, or, where that value is not given, the rated primary current multiplied by a factor from a table based on the duty cycle. The duty cycle is the share of a 10-minute period during which the welder can operate at its rated output. A lower duty cycle gives a lower multiplier. For a group of welders, section 630.11(B) permits the conductor ampacity to be based on the largest welders at full value and the rest at reduced values, because not all welders run at the same moment.

Overcurrent protection for transformer arc welders, under 630.12, is set at not more than a stated multiple, commonly 200 out of 100, of the maximum effective primary current or the rated primary current, and the conductors may be protected at not more than 200 out of 100 of their ampacity. A disconnect is required for each welder, with a rating not less than the conductor ampacity, under 630.13. Resistance welders have their own rules based on their duty cycle and demand. The multiplier values below are illustrative and match the pattern commonly found in the table; use your own book on the exam.

# Welder supply conductors from duty cycle (illustrative multipliers and group factors)
mult = {100: 1.00, 90: 0.95, 80: 0.89, 70: 0.84, 60: 0.78, 50: 0.71, 40: 0.63, 30: 0.55, 20: 0.45}
group = [1.00, 1.00, 0.85, 0.70]        # the rest at 0.60

def welder(i_primary, duty):
    return i_primary * mult[duty]

each = [welder(50, 50) for _ in range(4)]
each.sort(reverse=True)
total = sum(a * (group[i] if i < len(group) else 0.60) for i, a in enumerate(each))
print("Each welder:", ", ".join(f"{a:.1f} A" for a in each))
print(f"Group feeder: about {total:.1f} A")
print(f"Max breaker per welder at 200 out of 100: {2 * 50} A")

Each welder: 35.5 A, 35.5 A, 35.5 A, 35.5 A
Group feeder: about 126.0 A
Max breaker per welder at 200 out of 100: 100 A

Information technology equipment rooms

Article 645 applies to information technology equipment rooms that meet all of its conditions, including a disconnecting means, a separate heating, ventilating and air-conditioning system or fire-resistant separation, listed equipment, and occupancy limited to the people needed to operate and maintain the equipment. It is an optional article: a designer may choose to meet its conditions to use its relaxed rules for cables under a raised floor, or may simply wire the room under Chapters 1 through 4. Where Article 645 is used, section 645.10 requires a disconnecting means to remove power to all electronic equipment in the room and to the dedicated HVAC system serving it, with controls at the principal exit doors, unless the room qualifies for an exception, such as an integrated electrical system or a critical operations data system with specific protections. Exam questions on Article 645 usually test whether it applies and what the disconnect must control.

Industrial machinery under Article 670

Article 670 covers industrial machinery, defined broadly as a power-driven machine or group of machines working together, not portable by hand, used to process material by cutting, forming, pressure, electrical, thermal or similar techniques. The machine's electrical equipment is built to NFPA 79, Electrical Standard for Industrial Machinery, and Article 670 covers the supply side. A nameplate on each machine must give the supply voltage, phase, frequency, full-load current, maximum overcurrent device rating, short-circuit current rating, and the largest motor's current. Section 670.4(A) sets the supply conductor ampacity at not less than 125 out of 100 of the full-load current rating of all resistance heating loads, plus 125 out of 100 of the full-load current of the highest rated motor, plus the sum of the full-load currents of all other connected motors and apparatus that may be in operation at the same time. A disconnecting means must be provided for each machine, and the overcurrent protection must not exceed the nameplate maximum.

Other Chapter 6 articles at a glance

Several more Chapter 6 articles appear on exams from time to time. Article 610 covers cranes and hoists, with rules for runway conductors, disconnects at the runway and on the crane, and conductor sizing based on motor time ratings. Article 625, covered in lesson 8, is in Chapter 6. Article 640 covers audio signal processing, amplification and reproduction equipment. Article 660 covers X-ray equipment, with conductor sizing based on momentary and long-time ratings. Article 665 covers induction and dielectric heating equipment. Article 675 covers electrically driven or controlled irrigation machines. Article 690, 691, 692 and 694 cover PV, large-scale PV, fuel cells and wind, and Article 695 covers fire pumps, whose supply conductors and overcurrent protection follow unusual rules designed to keep the pump running until it destroys itself rather than trip in a fire.

Wrapping up the jobs

By the end of the week, Dana has three Chapter 6 checks in her job folder. The sign has its dedicated 20-ampere circuit, counted at 1,200 volt-amperes, with a disconnect at the parapet. The welding bay's feeder is sized at about 126 amperes using the duty cycle and group rules, with a disconnect at each welder. The crane has a runway disconnect and a crane disconnect as Article 610 requires. And the fourplex elevator, if the owner goes ahead, will need a lockable main line disconnect in the machine room, separate circuits for car lighting and pit lighting, and GFCI-protected receptacles in the pit. Ray reads the folder and nods. 'Now you know why Chapter 6 is worth tabbing article by article.'

2026 notes

In the 2026 edition, Chapter 6 is titled for specific equipment and some articles are reorganized, including the source articles that moved out of Chapter 6 into a group with storage and interconnection. Signs, elevators, welders and industrial machinery keep their article numbers, but check the section numbers and the values, such as the sign outlet load, in your own book.