Question
I've noticed that the color, size, and visibility of exit
signs varies greatly. Do UL requirements permit these
variances?
Answer: UL listed
exit signs must meet the requirements outlined in UL 924, the
Standard for Emergency Lighting and Power Equipment. These
fixtures are intended for installation in accordance with the National
Electrical Code, ANSI/NFPA 70, and the Life Safety Code,
ANSI/NFPA 101. Some of the listing requirements are as
follows.
Color — Typical exit sign letters are red, but UL
also lists signs with green lettering. The requirement for a
specific color may be included in state or local codes, but UL
has no color requirements.
Letter Size—UL 924 requires that exit sign letters
be at least 6 inches high. The 6-inch tall letters must be 2
inches wide (except for the 1): the stroke width must be 3/4
inch, and the spacing between the letters 3/8 inch. For larger
signs, the letters must increase in size proportionally, to
make them legible from a distance.
Luminance— The luminance specified in UL 924 and
NFPA 101 is 0.06 ft. lamberts. This is based on research
conducted by UL and industry in the mid-1970s that compared
the visibility of internally illuminated signs and signs with
self-contained energy sources.
Viewing Distance—All exit signs are evaluated for
a viewing distance of 100 feet, based on the requirements in
NFPA 101. In UL924, there are two tests that determine
compliance with these viewing distance requirements—UL's
analytical luminance visibility test conducted on a photometer
and a 100-foot observation visibility test. An exception to
this rule allows manufacturers to request that their
self-luminous or electroluminescent exit signs be tested at
50, 75, or 100 feet. UL would require these signs to be marked
with the legible viewing distance.
Self-luminous Materials—Self-luminous signs are
powered continuously by a self-contained energy source, other
than a battery. An example is radioactive tritium gas. Because
this gas has a limited life expectancy, UL requires a
replacement date to be marked on the sign. This date must be
visible after installation.
Photoluminescent Materials—Since photoluminescent
materials require exposure to light for activation of their
luminescent properties and have a limited life expectancy,
they may be used only in combination with other methods of
illumination.
Floor Proximity Egress Path Marking Systems—These
path marking systems are intended for indoor installation in
low level locations on floors, or on walls at or near the
floor, to provide a clearly marked path of escape during
emergency situations. Photoluminescent materials may be
evaluated for their suitability as a floor proximity marking
system in accordance with UL 1994, the Standard for Low Level
Marking and Lighting Systems.
Exit Fixture Retrofit Kits—Exit fixture retrofit
kits consist of parts and/or subassemblies intended for field
installation in listed exit fixtures. They are intended to
convert the light source of an exit fixture, i.e. incandescent
to fluorescent.
The names of listed exit sign manufacturers appear in the
product category Exit Fixtures (FWBO) in the Electrical
Construction Materials Directory (Green Book). The guide
card listing information also appears in the General
Information Directory (white book). Exit fixtures are
evaluated for installation at or near a ceiling or above a
door, unless marked for use at floor level. Exit fixtures that
are suitable for use at floor level have been subjected to
additional tests for mechanical abuse. Exit fixtures should
not be confused with "exit markers," which are
products that are UL classified for use in listed floor
proximity egress path marking systems.
Question
For outlet boxes that support ceiling suspended
fans, does UL consider out-of-balance fans?
Answer: Section 422-18(a) of the 1996 National Electrical Code permits
"listed" ceiling fans that do not exceed 35 lbs. to
be supported by outlet boxes identified for such use. Ceiling
fans exceeding 35 lbs. are required to be supported
independently of the outlet box, in accordance with Section
422-18(b).
Requirements for ceiling-suspended fan support for metallic
outlet boxes are located in UL 514A, the Standard for Metallic
Outlet Boxes. For nonmetallic boxes, the requirements can be
found in UL 514C, the standard for Nonmetallic Outlet Boxes,
Flush-Device Boxes, and Covers. Both of these standards
specifically include testing of the boxes using out-of-balance
fans.
For the ceiling-suspended fan support test, a ceiling fan
(weighing or ballasted to weigh 35 pounds) is installed in
accordance with the manufacturer's installation instructions.
Samples are tested in both the horizontal position and at an
incline of 30 degrees. A 40 gm (1.4 oz) weight (imbalance) is
placed on a single fan blade and a rigid-metal pipe is
connected to position the lower edge of the fan blade 12
inches from the ceiling. The fan is operated at a specified
speed for 24 hours to simulate an unbalanced fan and then the
outlet box is examined for damage. Next, one of the fan
mounting screws is loosened two full turns, and the fan is
operated for an additional 24 hours.
A UL listed outlet box intended to support a
ceiling-suspended fan is required to be marked
"Acceptable for Fan Support."
The special UL meetings for government inspectors
provide us an excellent opportunity to ask questions of UL
engineers and to clarify UL requirements. The "UL
Question Corner" answers questions of general interest
that are sent in from authorized governmental inspectors and
we believe will have interest for many inspectors.
Please send us questions you may have that are of
general interest, and we will have UL engineers answer them in
a future issue. If space does not permit answering all
questions received, we’ll see that you get an answer by
letter. Send your questions to:
UL Question Corner - IAEI News
PO Box 830848
Richardson, TX 75083-084
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