Installation of Industrial Control Panels

This month, the topic is the Installation of Industrial Control Panels.

An industrial control panel is an assembly of two or more components consisting of one of the following:

1. Power circuits components only; e.g. motor controllers, overload relays, fused disconnect switches, and circuit breakers
2. Control circuit components only, e.g. pushbuttons, pilot lights, selector switches, timers, switches, control relays
3. A combination of power circuit and control circuits [NFPA 70-2011]

Industrial control panels do include the controlled equipment, but does include all terminations, wiring, enclosures, and other ancillary devices required to connect the components [NFPA 70-2011].

The minimum installation requirements for an industrial control panel is that it meets the requirements detailed in the National Fire Protection Association (NFPA), National Electric Code, NFPA 70-2011, Article 409, Industrial Control Panels.  There are two types of requirements within NFPA 70-2011, Article 409: Installation (marking), and Construction requirements. 

An industrial control panel is required to have a label on the enclosure with the following information:

1. Manufacturer’s name, trademark, or other descriptive marking
2. Supply voltage, number of phases, frequency, and full-load current for each incoming supply
3. Short-circuit current rating (SCCR) of the industrial control panel using an approved method, unless the industrial control panel only contains control circuit components
4. Electrical diagram number(s) or the number of the index to the electrical diagrams
5. Enclosure type
6. If the industrial control panel is intended for a service entrance application, it shall be marked accordingly
7. Industrial control cabinets supplied by more than one power source shall be marked

Industrial control panels are also required to have specific components within the industrial control panel analyzed for proper and safe operation.  This includes:

1. Overcurrent protection (internal or external)
2. Equipotential bonding of all grounded parts
3. Proper wiring space and wiring utilization
4. Proper spacings between adjacent components
5. Proper disconnecting means for all motor loads

Industrial control panels for use in the US are not required to be Listed or Approved by an OSHA Nationally Recognized Testing Laboratory (NRTL), but it is a good idea.  As the reader will note, there are minimal operational or product safety requirements defined in the NFPA 70-2011, Article 409.  From a product safety standpoint, NFPA 70-2011, Article 409 does not have requirements regarding leakage current, that the internal components are used in accordance with their operating limitations, or that the industrial control equipment does not create a safety hazard when exposed to normal or abnormal operating conditions.

Evaluation of an industrial control panel to product safety standards will reduce the potential of the equipment presenting a product safety hazard.  The most notable safety standard for an industrial control panel in the US is Underwriters Laboratories (UL), Standard for Industrial Control Panels, UL 508A.  However, UL 508A is in a transition phase where it will soon be obsolete.  To harmonize with international standards, UL will be moving to the UL, Low-Voltage Switchgear and Controlgear, UL 60947 series of standards.  There will be a number of standards for specific components used for industrial control panel and auxiliary equipment applications. 

After 2012 January, all industrial control panels will be evaluated to UL 60947 unless the manufacturer request’s the industrial control panel be evaluated to UL 508A.  After 2017 January, all industrial control panels must be evaluated to UL 60947 to maintain Listing or Approval.

To ensure the best installation of an industrial control panel, the equipment should be Listed or Approved to UL 508A or UL 60947 by an NRTL and installed in accordance with the requirements of NFPA 70-2011, Article 409.  In addition, a Risk Assessment should be conducted to ensure that operational and safety requirements not identified in the standards have been accounted for.

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