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Can I install a general use ordinary location ICP to control a circuit that extends into a hazardous classified location?

Posted By Underwriters Laboratories, Tuesday, March 01, 2011
Updated: Wednesday, January 09, 2013

Question

Can I install a general use ordinary location Listed industrial control panel (ICP) to control a circuit that extends into a hazardous classified location? If not, what ICPs are suitable for use in this application and how can these panels be identified? Are these the same as ICPs that are Listed for installation in the hazardous area?

Answer

No, industrial control panels Listed for use in ordinary locations are Listed under the product category Industrial Control Panels (NITW), and are not intended for controlling circuits extending into a hazardous classified location. Industrial control panels (ICPs) that would be suitable for this application are Listed under the product category Industrial Control Panels Relating to Hazardous Locations (NRBX), located on page 249 in the 2010 UL White Book. The Guide Information for NITW can be located on page 235 in the 2010 UL White Book. The Guide Information for these categories can also be found online at www.ul.com/database and entering the category code NITW or NRBX in the category code search field.

Industrial control panels Listed under NITW are intended for installation in accordance with Article 409 of ANSI/NFPA 70,National Electrical Code(NEC) and unless otherwise marked, are intended for general-use industrial applications for control of heaters, lighting, motors or pump loads, or a combination of these loads, and are intended for installation in accordance with chapter 4 of theNEC.

Products Listed under (NRBX) are intended for installation in unclassified (ordinary) locations. They are provided with intrinsically safe (low energy) circuit(s) as indicated on the product, for extension into a hazardous (classified) location.

For intrinsically safe circuits, the energy level available in the hazardous location under normal and abnormal conditions is sufficiently low as not to cause ignition of the specified explosive atmospheres. To maintain the low energy levels, it is necessary that the intrinsically safe and associated equipment be installed and interconnected in accordance with the instructions provided. The intrinsically safe circuit wiring must be routed in a separate raceway or otherwise reliably segregated from all power and other circuit wiring to preclude excessive currents and voltages from being impressed on the intrinsically safe circuit, rendering it non-intrinsically safe.

Control panels intended for installation in hazardous (classified) locations are covered under Control Panels and Assemblies for Use in Hazardous Locations (NNNY), located on page 244 in the 2010 UL White Book.

The UL Mark is a clear indicator regarding the intended application for each of these UL Listed services:

NITW panels: The UL Listing Mark will contain one of the following product identities, "Open Industrial Control Panel,” "Enclosed Industrial Control Panel” or "Industrial Control Panel Enclosure.”

NRBX panels: The UL Listing Mark will contain one of the following product identities, "Industrial Control Panel Relating to Hazardous Locations” or "Enclosed Industrial Control Panel Relating to Hazardous Locations” and the statement "with Intrinsically Safe Circuit Extensions.”

NNNY panels: The UL Listing Mark will contain one of the following product identities, "Control Assembly Body for Hazardous Locations,” "Control Assembly Cover for Hazardous Locations” or "Control Panel for Hazardous Locations.”

In addition, UL Listed NRBX and NNNY panels will be externally marked to indicate the intended Class, Division and Group associated with the end-installation.


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Tags:  March-April 2011  UL Question Corner 

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