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Are dry type transformers with expanded metal bottoms suitable for installation on combustible floors?

Posted By Underwriters Laboratories, Sunday, September 01, 2002
Updated: Thursday, February 14, 2013

Question: Dry type transformer

Are dry type transformers with expanded metal bottoms suitable for installation on combustible floors?

Answer

Dry type transformers with expanded metal bottoms are not suitable for installation on combustible floors. They are required to be enclosed. The enclosure houses all uninsulated live parts. However, the bottom of the enclosure does not need to be provided (or may have openings) for transformers intended to be pad mounted. These types of transformers are required to be marked, "Not For Use on Combustible Floors.” Dry type transformers are Listed under the category "Power and General Purpose Transformers, Dry Type” (XQNX). The UL Guide Information can be found on page 124 of the 2002 General Information for Electrical Equipment Directory (White Book). The Standard used to investigate products in this category is UL 1561, "Dry-Type General Purpose and Power Transformers.”


 Question: Incandescent recessed luminaire

Are all incandescent recessed luminaires (fixtures) Listed for installation in a sloped ceiling?

Answer

Not all Listed Incandescent Recessed Luminaires (IEZX) are suitable for use in sloped ceilings. There are UL Listed Incandescent Recessed Luminaires (IEZX) (located on page 44 of the 2002 General Information for Electrical Equipment Directory, the White Book) specifically designed for use in sloped ceilings. These luminaires are constructed with the recessed housing mounted at an angle to the plaster (mounting) frame. There are no special markings required on these luminaires since the intended use and mounting orientation is obvious. They are tested with the lamp pointing straight down during the normal temperature test.

"Standard” flat ceiling type incandescent recessed luminaires, without the sloped recessed housing, are typically not evaluated for use in a sloped ceiling, unless specifically requested by the manufacturer. This orientation option would also be outlined in the installation instructions.

Presently, there are several "standard” flat ceiling type recessed luminaires that have been evaluated for use in a sloped ceiling and are marked as being suitable for use in sloped ceilings when used with specific trims.


HID luminaire

There have been some issues regarding HIDluminaires. A new style lamp is available that is intended to fit into a special lampholder. Can the new lamp be used in old fixtures?

Answer

Replacing the existing lampholder of an HID luminaire with a "special” lampholder should be considered a significant alteration of the UL Listed product in the field. As such, UL does not know what effect this alteration may have on the safety of the product unless the alteration is specifically evaluated by UL.

Luminaires are marked with the ANSI designation of the lamps that are intended to be used in the luminaire. The Listing of the HID luminaire only extends to the lamps that are marked on the product. Even if the new lamp fits into the existing lamp holder, the combination is not considered to be listed without further evaluation by UL.


 

Question: Manufactured wiring system

How does an AHJ in the field differentiate between a Wiring Assembly and a Manufactured Wiring System? Article 604 of the NEC applies to Manufactured Wiring Systems. What article of the NEC applies to Wiring Assemblies?

Answer

Manufactured Wiring Systems are Listed under the category "Manufactured Wiring Systems (QQVX) located on page 94 of the 2002 White Book and covered under Article 604 of the NEC. These systems are investigated for compliance with the Standard for Manufactured Wiring Systems, UL 183.

Manufactured Wiring Systems typically employ modular nonstandard configuration connectors to interconnect the various parts of the system.

Wiring assemblies are Listed under the category "Wiring Assemblies” (QQYZ), located on page 95 of the 2002 White Book. A wiring assembly is a collection of Listed parts, factory assembled in accordance with NEC requirements applicable to the wiring methods and parts employed. They are Listed as a Wiring Assembly and are intended to be installed in accordance with the NEC articles covering the individual parts’ intended use. UL requires the packaging of a Listed Wiring Assembly to include an itemized identification of the parts that make up the assembly, as well as the installation instructions to enable the AHJ to determine the acceptability of the installation.

A typical assembly, for example, might consist of a length of Listed flexible, liquid tight conduit, with Listed fittings installed at each end, and prewired with 14 AWG, THWN conductors for connecting between an air conditioning unit and its disconnect.

Wiring assemblies are Listed under the category "Wiring Assemblies” (QQYZ) also located on page 95 of the 2002 White Book. The "Product Identification” portion of the UL Listing Mark will appropriately identify the product as either a manufactured wiring system or a wiring assembly.


Tags:  September-October 2002  UL Question Corner 

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