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Article 409

Industrial Control Panels

Part I. General

409.1 Scope. This article covers industrial control panels intended for general use and operating at 1000 volts or less.

Informational Note: ANSI/UL 508A, Standard for Industrial Control Panels, is a safety standard for industrial control panels.

409.3 Other Articles. In addition to the requirements of Arti‐ cle 409, industrial control panels that contain branch circuits for specific loads or components, or are for control of specific types of equipment addressed in other articles of this Code, shall be constructed and installed in accordance with the appli‐ cable requirements from the specific articles in Table 409.3.

Part II. Installation

  1. Conductor — Minimum Size and Ampacity. The size of the industrial control panel supply conductor shall have an ampacity not less than 125 percent of the full-load current rating of all heating loads plus 125 percent of the full-load current rating of the highest rated motor plus the sum of the full-load current ratings of all other connected motors and apparatus based on their duty cycle that may be in operation at the same time.
  2. Overcurrent Protection.
  1. General. Industrial control panels shall be provided with overcurrent protection in accordance with Parts I, II, and IX of Article 240.
    1. ARTICLE 409 — INDUSTRIAL CONTROL PANELS
      Table 409.3 Other Articles
      Equipment/OccupancyArticleSectionBranch circuits210
      Luminaires410
      Motors, motor circuits, and controllers430
      Air-conditioning and refrigerating440
      equipmentCapacitors 460.8, 460.9Hazardous (classified) locations 500, 501, 502, 503, 504, 505Commercial garages; aircraft hangars; motor fuel dispensing facilities; bulk storage plants; spray application, dipping, and coating processes; and inhalation anesthetizing locations511, 513, 514, 515, 516, and517 Part IVCranes and hoists 610Electrically driven or controlled irrigation machinesElevators, dumbwaiters, escalators, moving walks, wheelchair lifts, and stairway chair lifts675620Industrial machinery 670Resistors and reactors 470Transformers 450Class 1, Class 2, and Class 3 remote-control, signaling, and power-limited circuits725
  2. Location. This protection shall be provided for each incoming supply circuit by either of the following:
    1. An overcurrent protective device located ahead of the industrial control panel.
    2. A single main overcurrent protective device located within the industrial control panel. Where overcurrent protection is provided as part of the industrial control panel, the supply conductors shall be considered as either feeders or taps as covered by 240.21.
  3. Rating. The rating or setting of the overcurrent protective device for the circuit supplying the industrial control panel shall not be greater than the sum of the largest rating or setting of the branch-circuit short-circuit and ground-fault protective device provided with the industrial control panel, plus 125 percent of the full-load current rating of all resistance heat‐ ing loads, plus the sum of the full-load currents of all other motors and apparatus that could be in operation at the same time.

Exception: Where one or more instantaneous trip circuit breakers or motor short-circuit protectors are used for motor branch-circuit short- circuit and ground-fault protection as permitted by 430.52(C), the procedure specified above for determining the maximum rating of the protective device for the circuit supplying the industrial control panel shall apply with the following provision: For the purpose of the calcula‐ tion, each instantaneous trip circuit breaker or motor short-circuit protector shall be assumed to have a rating not exceeding the maximum percentage of motor full-load current permitted by Table 430.52 for the type of control panel supply circuit protective device employed.

Where no branch-circuit short-circuit and ground-fault protective device is provided with the industrial control panel for motor or combination of motor and non-motor loads, the rating or setting of the overcurrent protective device shall be based on 430.52 and 430.53, as applicable.

  1. Short-Circuit Current Rating.
  1. Installation. An industrial control panel shall not be installed where the available short-circuit current exceeds its short-circuit current rating as marked in accordance with 409.110(4).
  2. Documentation. If an industrial control panel is required to be marked with a short-circuit current rating in accordance with 409.110(4), the available short-circuit current at the indus‐ trial control panel and the date the short-circuit current calcu‐ lation was performed shall be documented and made available to those authorized to inspect the installation.

409.30 Disconnecting Means. Disconnecting means that supply motor loads shall comply with Part IX of Article 430.

409.60 Grounding. Multisection industrial control panels shall be bonded together with an equipment grounding conductor or an equivalent equipment grounding bus sized in accordance with Table 250.122. Equipment grounding conduc‐ tors shall be connected to this equipment grounding bus or to an equipment grounding termination point provided in a single-section industrial control panel.

Part III. Construction Specifications

409.100 Enclosures. Table 110.28 shall be used as the basis for selecting industrial control panel enclosures for use in specific locations other than hazardous (classified) locations. The enclosures are not intended to protect against conditions such as condensation, icing, corrosion, or contamination that may occur within the enclosure or enter via the conduit or unsealed openings.

409.102 Busbars and Conductors. Industrial control panels utilizing busbars shall comply with 409.102(A) and (B).

  1. Support and Arrangement. Busbars shall be protected from physical damage and be held firmly in place.
  2. Phase Arrangement. The phase arrangement on 3-phase horizontal common power and vertical buses shall be A, B, C from front to back, top to bottom, or left to right, as viewed from the front of the industrial control panel. The B phase shall be that phase having the higher voltage to ground on 3- phase, 4-wire, delta-connected systems. Other busbar arrange‐ ments shall be permitted for additions to existing installations, and the phases shall be permanently marked.

409.104 Wiring Space.

  1. General. Industrial control panel enclosures shall not be used as junction boxes, auxiliary gutters, or raceways for conductors feeding through or tapping off to other switches or overcurrent devices or other equipment, unless the conductors fill less than 40 percent of the cross-sectional area of the wiring space. In addition, the conductors, splices, and taps shall not fill the wiring space at any cross section to more than 75 percent of the cross-sectional area of that space.
  2. Wire Bending Space. Wire bending space within indus‐ trial control panels for field wiring terminals shall be in accord‐ ance with the requirements in 430.10(B).

409.106 Spacings. Spacings in feeder circuits between uninsu‐ lated live parts of adjacent components, between uninsulated live parts of components and grounded or accessible non– current-carrying metal parts, between uninsulated live parts of components and the enclosure, and at field wiring terminals shall be as shown in Table 430.97(D).

Exception: Spacings shall be permitted to be less than those specified in Table 430.97(D) at circuit breakers and switches and in listed compo‐ nents installed in industrial control panels.

409.108 Service Equipment. Where used as service equip‐ ment, each industrial control panel shall be of the type that is suitable for use as service equipment.

Where a grounded conductor is provided, the industrial control panel shall be provided with a main bonding jumper, sized in accordance with 250.28(D), for connecting the groun‐ ded conductor, on its supply side, to the industrial control panel equipment ground bus or equipment ground terminal.

409.110 Marking. An industrial control panel shall be marked with the following information that is plainly visible after instal‐ lation:

  1. Manufacturer’s name, trademark, or other descriptive marking by which the organization responsible for the product can be identified.
  2. Supply voltage, number of phases, frequency, and full- load current for each incoming supply circuit.
  3. Industrial control panels supplied by more than one elec‐ trical source where more than one disconnecting means is required to disconnect all circuits 50-volts or more within the control panel shall be marked to indicate that more than one disconnecting means is required to de- energize the equipment. The location of the means necessary to disconnect all circuits 50-volts or more shall be documented and available.
  4. Short-circuit current rating of the industrial control panel based on one of the following:
    1. Short-circuit current rating of a listed and labeled assembly
    2. Short-circuit current rating established utilizing an approved method
    Informational Note: ANSI/UL 508A, Standard for Indus‐ trial Control Panels, Supplement SB, is an example of an approved method.Exception to (4): Short-circuit current rating markings are not required for industrial control panels containing only control circuit components.
  5. If the industrial control panel is intended as service equipment, it shall be marked to identify it as being suita‐ ble for use as service equipment.
  6. Electrical wiring diagram or the identification number of a separate electrical wiring diagram or a designation referenced in a separate wiring diagram.
  7. An enclosure type number shall be marked on the indus‐ trial control panel enclosure.

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