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Can the wiring of normal and emergency power circuits be intermixed in luminaires?

Posted By Underwriters Laboratories, Sunday, November 01, 2009
Updated: Friday, February 08, 2013

Question

Can the wiring of normal and emergency power circuits be intermixed in luminaires?

I have an installation of a series of ten, row-mounted, 2 by 4 fluorescent troffer luminaires listed as surface-mounted fluorescent luminaires. They are provided with two circuits integral to the luminaire and also with wiring harnesses to connect those two circuits from one luminaire, end-to-end to another in a row-mount application. Every third luminaire is on the emergency lighting circuit. One of two circuits in the luminaire is connected to the normal power circuit and the other is supplied by the emergency power circuit. Do these rows of luminaires count as one emergency luminaire? Also, does the listing of these luminaires allow the wiring of the emergency and normal power circuits to be intermixed in the luminaires that are not part of the emergency lighting circuit?

Answer

When a series of listed luminaires are row-mounted end to end, that does not make the assembly one luminaire. The luminaires in question are listed under the product category Fluorescent Surface Mounted Luminaires (IEUZ), located on page 157 of the 2009 UL White Book. These luminaires are evaluated for compliance with the Standard for Safety for Luminaires, UL 1598. Luminaires that are specifically listed for use as emergency lighting are listed under the product category Emergency Lighting and Power Equipment (FTBR), located on page 142 in the 2009 UL White Book. Luminaires listed under (FTBR) would be evaluated for compliance with the Standard for Safety for Emergency Lighting and Power Equipment, UL 924.

A "normal” UL 1598 luminaire can certainly be part of the facility’s emergency lighting system. If the facility has a transfer switch which feeds an emergency lighting panel, the branch circuits from that panel can feed UL 1598 listed luminaires and thus they will serve both on normal power and as emergency luminaires during a power outage. However, the wiring of the normal and emergency power circuits cannot be intermixed in the luminaires that are not part of the emergency lighting circuit.

NEC Section 700.9(B)(2) requires that wiring from an emergency source to the emergency load be kept entirely independent of all other wiring and equipment wiring except for wiring supplied from two sources in exit or emergency luminaires. In order to comply with NEC 700.9(B)(2), the luminaires connected to the emergency lighting circuit (wired in a continuous row with other luminaires not supplied by this emergency panel), would need the emergency feed to exit the row and re-enter at the next designated emergency luminaire (separate conduit run), or the emergency feed would need to use a separate channel from the normal power conductors within the continuous row (with separate conduit entries / knockouts to accommodate the separation). There should be either a fixed barrier or a similar means of securing these separate circuits from intermixing within the non-emergency luminaire; this isn’t a requirement of UL 1598 because it does not anticipate the use.

Read more by UL

Tags:  November-December 2009  UL Question Corner 

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