HID Accent Lighting Systems

62 Pages·1998·1 MB·English

by  Dorene Maniccia

Specifier Reports
HID Accent Lighting Systems
Low-wattage high-pressure sodium and metal halide
lamps and accent luminaires
Volume 4 Number 2 October 1996
Program Sponsors
CINergy
Energy Center of Wisconsin
Introduction
Iowa Energy Center
Lighting Research Center Low-wattage high-pressure sodium (HPS) and metal halide (MH)
New England Electric Companies* lamps are increasingly popular among lighting specifiers (see
Figure 1). These high-intensity discharge (HID) lamps are rated at
New York State Energy Research
175 watts (W), have higher efficacy, longer average rated life, and
and Development Authority
greater light output than the incandescent lamps typically used for
Northern States Power Company accent lighting applications. Some low-wattage HID lamps also offer
Southern California Edison Company color properties comparable to those of incandescent sources. As a
result, low-wattage HID systems can be used in applications that
United States Department of Energy
require efficacious sources with high intensities, good color rendering
United States Environmental properties, and long life. However, because low-wattage HID systems
Protection Agency
are relatively new, specifiers and users may have questions about the
*The New England Electric Companies include performance of these systems in accent lighting applications. The
New England Power Service Company, New electronic ballasts developed for some low-wattage HID lamps also
England Power Company, Massachusetts
add decisions in the specification process.
Electric Company, The Narragansett Electric
Company, and Granite State Electric Company.
Figure 1. Low-Wattage HID Accent Lighting of a
Grocery Store Floral Display
Contents
Introduction...............................................1
Lamps.........................................................2
Ballasts.......................................................6
Luminaires.................................................8
Alternative Technologies.......................13
Performance Evaluations.......................13
Further Information ...............................15
Data Table Terms & Definitions...........16
List of Tables...........................................18
Publication Ordering Information.........48
from DELTA Portfolio, Vol.1 No.1
In this issue of Specifier Reports, the and appearance to luminaires for incandes-
Findings
National Lighting Product Information cent lamps.
• With a few exceptions, low- Program (NLPIP) evaluates the following Low-wattage HID lamps are also
wattage HID lamps meet characteristics of HID accent lighting alternatives for incandescent reflector
their manufacturer-
systems: lamps that do not meet the lamp efficacy
reported ratings.
•Photometric performance of low-wattage requirements of the Energy Policy Act of
• Tilting universal-burn MH HID lamps from six manufacturers. 1992 (EPACT) (U.S. Congress 1992).
lamps has little effect on •Effects of tilting on the light output of State energy codes that establish power
their light output.
medium-base, universal-burn MH lamps. limits for lighting, usually based on
• Electronic ballasts for ASHRAE/IES Standard 90.1, are also
•Effects of voltage variation on the light
double-ended MH lamps more easily met with HID systems than
output, color, and lamp power of double-
provide more consistent with incandescent systems. Although
lamp performance over ended MH lamps from four manufactur-
lamp manufacturers offer incandescent
variations in supply voltage ers, operated on electronic and magnetic
reflector lamps that do meet EPACT
than magnetic ballasts do. ballasts.
requirements (see NLPIP’s Specifier
•Ease of aiming and relamping of recessed Reports: Reflector Lamps), the efficacies of
and semi-recessed adjustable luminaires and these lamps are still significantly lower
track luminaires from seven manufacturers. than those of low-wattage HID lamps.
Table 1 on p. 19 lists the manufacturers
of HID lamps and their telephone num-
bers. Tables 2–4 on pp. 20–29 list
manufacturer-reported information for
many of the lamp characteristics de-
Lamps scribed in this report. Information about
NLPIP’s evaluation of HID lamps is
Specifiers have used incandescent reflec- available in “Lamp Evaluations” on p. 13.
tor (R) and parabolic aluminized reflector The results of the evaluations appear in
(PAR) lamps to illuminate displays and Tables 5 and 6 on pp.30–31.
merchandise because of their color
properties and their diversity of size, beam
Operation and Construction
intensity, and beam spread. Compared to
existing HID lamps, these incandescent HID lamps start when a high voltage [3–5
lamps were relatively expensive to operate kilovolts (kV)] is applied to the electrodes
because of their relatively short lives and through a gas mixture in a discharge
low efficacies. Conversely, HID lamps (arc) tube. The discharge tube of an MH
offered long average rated life and high lamp contains mercury and halide com-
efficacies but were too large and produced pounds and usually is made of quartz,
too much light to be effective in accent although ceramic is sometimes used (see
lighting systems. New low-wattage HID sidebar “Ceramic Discharge Tubes for
lamps offer much longer life and better MH Lamps” on p. 3). The discharge tube
efficacy than incandescent lamps, and their of an HPS lamp contains mercury, sodium
color rendering characteristics approach amalgam, and xenon, and it is made of
those of incandescent lamps. These new ceramic which resists the corrosive
HID lamps also are available in compact sodium environment better than quartz. A
sizes. Luminaires for these low-wattage ballast supplies the starting voltage that
HID lamps frequently are similar in size strikes an arc within the discharge tube of
an HID lamp.
As pressure and temperature increase,
the materials within the discharge tube
Comparison of 100-W PAR Lamps
vaporize and emit light and ultraviolet
(UV) energy. A bulb, usually made of
Incandescent MetalHalide Incandescent MetalHalide
Flood Flood Spot Spot borosilicate glass, provides a stable
thermal environment for the discharge
CBCP(cd) 2,400 15,000 6,600 28,000
tube and reduces the amount of UV
InitialLightOutput(lm) 1,200 6,500 1,200 7,000 radiation that the lamp emits. MH lamps
often have a phosphor finish on the inside
AverageRatedLife(h) 2,000 7,500 2,000 7,500
of the bulb that both diffuses the light and
2 Specifier Reports: HID Accent Lighting Systems
Light Output
Ceramic Discharge Tubes
Figure 2. Low-Wattage, Medium-Base
Ratings. Initial light output is the quan- for MH Lamps
ED17 MH Lamp
tity of light in lumens (lm) produced by GE Lighting and Philips
the lamp when it is new, usually after Lighting Co. have introduced
operating for 100 hours (h). Manufactur- MH lamps with ceramic
Outer bulb
discharge tubes. According to
ers report the light output of a lamp in its
the manufacturers, ceramic
recommended operating position. For
discharge tubes offer 10 to
universal-burn lamps, some manufactur- 20% more light output,
Quartz discharge tube
ers report light output for both vertical improve color stability and
Gas mixture
and horizontal operating positions uniformity compared with MH
Discharge tube support lamps with quartz discharge
(see “Tilting” on p.4).
tubes, and increase the color
For PAR (parabolic aluminized reflec-
rendering index (CRI) value
tor) lamps, manufacturers commonly to more than 80 (see p. 5).
provide the light intensity and beam
spread instead of the initial light output.
Base
Manufacturers report the light intensity at
the center of the beam as the center beam
candlepower (CBCP) or the maximum
beam candlepower (MBCP), measured in
candelas (cd). The beam spread is de-
Figure 3. Low-Wattage, Medium-Base scribed by the beam angle at which the
ED17 HPS Lamp lamp produces 50% of its CBCP, as shown
in Figure 4. Lamp manufacturers provided
the initial light output, CBCP, and beam
Outer bulb angle for each of the MH PAR lamps
included in this report; these values
Ceramic discharge tube appear in Table 4 on p. 26.
In NLPIP’s photometric measurements,
Gas mixture
most of the lamps equaled or exceeded
their rated light output, although all of the
Discharge tube support
MH PAR lamps had lower CBCP ratings in
NLPIP’s test than manufacturers reported.
Base Figure 4. Beam Angle
changes the lamp’s color properties. HPS
lamps sometimes have a diffuse finish,
similar to that used in incandescent
lamps, on the inside of the bulb to diffuse
the light output. Figures 2 and 3 illustrate a = beam angle
the construction of typical low-wattage,
medium-base HID lamps.
With an appropriate ballast and control
system, HID lamps with wattages as low
as 100–150-W can be dimmed. See
NLPIP’s Lighting Answers: Dimming
a
Systems for High-Intensity Discharge
Lamps (1994).
0(cid:176)
(center beam)
Specifier Reports: HID Accent Lighting Systems 3
Tilting. In accent lighting systems, HPS lamps at 50% of rated lamp life and for
luminaires and lamps are often tilted so MH lamps at 40% of rated lamp life. Ac-
that their light output can be aimed. All cording to manufacturer ratings, light
low-wattage HPS and most medium-base output typically decreases by the percent-
low-wattage MH lamps are designed for ages shown in the chart below. NLPIP did
universal operating positions. Manufactur- not measure LLD for this report.
ers recommend that double-ended lamps
be operated, and even stored, horizon-
Lamp Lumen Depreciation Over Time
tally. Outside the specified operating
range, which is available from the manu-
Decrease Decrease
facturers, the light output of a low wattage at50% at40%
MH lamp may decrease and its color ofRated ofRated
LampType CRI LampLife LampLife
appearance may shift.
NLPIP evaluated the effects of tilting
HPS 60–69 10–20% NA
on the light output of medium-base,
universal-burn MH lamps and found HPS ‡ 70 20–25% NA
insignificant changes in light output when
MHmediumbase all NA 15–40%
lamps were tilted. See “Lamp Evaluations”
on p. 13 for details about the evaluation. MHdoubleended all NA 10–20%
Lamp lumen depreciation (LLD). LLD
Efficacy
describes the gradual decrease in a lamp’s
light output as the lamp ages. The primary Efficacy is the initial light output of a lamp
cause of LLD in HID lamps is the evapora- divided by its active power, expressed in
tion of tungsten from the electrodes, which lumens per watt (LPW). Lamp efficacy
blackens the inside of the discharge tube. values listed in Tables 2–4 on pp. 20–29
A secondary cause of LLD in MH lamps is include only the active power of the lamp
degradation of the bulb’s phosphor finish, and do not include ballast power. Low-
if it has one. wattage HPS lamps have efficacies between
Manufacturers usually use a lumen 40–73 LPW. Low-wattage MH PAR lamps
maintenance curve to illustrate the de- range in efficacy from 46–70 LPW. Other
creasing light output of a lamp over its life. low-wattage MH lamps range in efficacy
They also publish “mean lamp lumen” from 60–95 LPW.
values, which indicate a lamp’s light output
at a certain percentage of lamp life. Most
manufacturers report mean light output for
Safety Precautions for MH Lamps Shrouded MH and MH PAR Lamps
MH lamps operate at very high pressures and may burst when they are
operated outside normal electrical and thermal parameters or are near
the end of their life. As a safety precaution, Underwriters Laboratory
(UL) Standard 1572-1990 requires that luminaires that use MH lamps
have a lamp containment barrier to prevent injury from broken lamps
(UL 1990). Luminaires that have a lamp containment barrier are referred
to as enclosed luminaires; those without such a barrier are referred to
as open luminaires. A lamp containment barrier is not required if the
lamp manufacturer specifies that the lamp can be used in open lumi-
naires, or if the major axis of the lamp is oriented – 15(cid:176) from vertical
when the luminaire is installed as intended (UL 1990).
Some low-wattage MH lamps can be used in open luminaires. These
lamps have a glass shroud inside the outer bulb that surrounds the
discharge tube (photo, bottom row). If the tube bursts, the shroud pre-
vents the outer bulb from shattering. MH PAR lamps also may be used
in open luminaires because they have a hard glass lens that contains
the discharge tube (photo, top row).
4 Specifier Reports: HID Accent Lighting Systems
Color discharge tubes and high-CRI HPS lamps
HID Lamp Shapes
undergo minimal color shift over time.
Manufacturers use two measures to
The shape and size of an HID
specify lamp color: correlated color Lamp aging. As an MH lamp operates, lamp’s outer bulb is desig-
temperature (CCT) and color rendering nated by a letter, or group of
the mixture of the vaporized metal halides
index (CRI). letters, followed by a number.
changes, which changes the lamp’s CCT
The letter(s) describes the
(Meyer and Nienhuis 1988). Manufactur- shape of the bulb (see be-
CCT. The correlated color temperature
ers customarily report color shift due to low), and the number de-
(CCT) describes the color appearance of a lamp aging as the maximum change in scribes the bulb’s diameter in
lamp in terms of a reference light source eighths of an inch (in.). For
CCT from its initial value to its value at 40%
(blackbody radiator) operated at a given example, a T10 lamp is
of the lamp’s rated life. NLPIP did not
tubular in shape and has a
temperature, measured in kelvin (K).
Lamps with CCTs of 3100 K or less measure color shift due to lamp aging for diameter of 10/8, or 11/4, in.
this report; manufacturer-supplied color
usually are considered warm in appear- B: bulged
shift values are provided in Tables 2-4.
ance, those with CCTs of 4000 K and BD: bulged dimpled
greater are cool, and those with CCTs T: tubular
Tilting. Tilting MH lamps can also cause
between 3100 and 4000 K are considered TD: tubular dimpled
color shift because it changes the mixture
neutral. Low-wattage MH lamps typically of the vaporized metal halides. NLPIP did E: elliptical
have CCTs of 2700–4300 K; low-wattage
not measure color shift from tilting for ED: elliptical dimpled
HPS lamps have CCTs of 2200–2800 K. In
this report, but recommends that specifi- PAR: parabolic aluminized
NLPIP’s evaluations, the median CCTs for ers evaluate the specific lamp, ballast, and reflector
most lamps were close to their rated
luminaire combination in a mock-up to
values; a few differed by 500 K or more.
determine possible effects of tilting on
MH-lamp color.
CRI. The color rendering index (CRI)
value of a lamp describes the shift in color
Manufacturer variation. Lamps from
appearance of a set of reference color
different manufacturers that have the
samples when illuminated by the lamp,
same rated CCT, and even new lamps
compared with the color appearance of the B-shaped BD-shaped
from the same manufacturer, can have
(bulged) (bulged dimpled)
same color samples when illuminated by a
different color appearances and undergo
reference light source of comparable CCT
color shift at different rates. To reduce
(IESNA 1993). The maximum CRI value is
the likelihood of noticeable color differ-
100. Low-wattage MH lamps commonly
ences between lamps, NLPIP recom-
have CRI values of 65–96. Low-wattage
mends that specifiers use lamps from the
color-corrected HPS lamps typically have
same manufacturer whenever possible
CRI values of 65–85. HPS lamps with CRI
and that specifiers encourage group
values greater than 60 are called color- T-shaped TD-shaped
relamping in their installations.
improved lamps; HPS lamps with CRI (tubular) (tubular dimpled)
values of 70 or greater are called high CRI
lamps. In NLPIP’s evaluations, the median Life
values for most lamps were within five
Most lamp manufacturers report the
points of their rated CRI values; a few
average rated life of a lamp, which is the
differed by more than five points.
number of hours at which 50% of the
lamps in a large test group are still
Color Shift and Variation operating under standard test conditions. E-shaped ED-shaped
For HID lamps, lamp life ratings are (elliptical) (elliptical dimpled)
HID lamps with the same rated CCT can
based on a 10-hours-on-1-hour-off operat-
appear to be different in color because of
ing cycle. Lamp life decreases if the lamps
color shift and variations in manufactur-
are on for less than 10 h per start. Operat-
ing. Color shift occurs when a lamp’s CCT
ing lamps for 5, 2.5, and 1.25 h per start
changes due to age, a change in the lamp’s
decreases life by approximately 25, 50,
position, or a variation of the supply
and 60%, respectively (GE Lighting 1993;
voltage. MH lamps are more susceptible to
Venture Lighting 1991). Lamp manufac-
color shift than HPS lamps; in fact, color
turers generally publish derating factors PAR-shaped
concerns are often cited by specifiers as
so that specifiers can estimate average life (long neck) (regular)
the principal barrier to more widespread
for different operating cycles.
use of MH lamps. Manufacturers report
that newer MH lamps with ceramic
Specifier Reports: HID Accent Lighting Systems 5
For universal-burn lamps, many manu- the amount of UV energy emitted by
facturers report different life values for specific HID lamp types. UV filters
horizontal and vertical positions. sometimes are used in applications where
Universal-burn lamps have longer average fading is of concern.
rated lives for vertical positions than for
horizontal positions. For example, the
average rated life of a 100-W MH lamp is
10,000 h for the horizontal position and
15,000 h for the vertical position. NLPIP
did not measure lamp life for this report.
Ballasts
Warm-Up and Restrike Time
Ballasts provide the proper voltage to
Warm-up time is the time required for a start lamps, and they regulate starting and
cold HID lamp to start and reach a stable operating current. Many low-wattage HID
operating temperature and pressure. lamps can operate on either magnetic or
Some manufacturers publish warm-up electronic ballasts, although electronic
times to 100% of maximum light output; ballasts are not presently available for all
others publish warm-up times to 95, 90, lamp types. Electronic ballasts are lighter
or 80% of maximum light output. Most and smaller than their magnetic counter-
HPS and MH lamps listed in Tables 2–4 parts. They require less power to operate
on pp. 20–29 have rated warm-up times to lamps but have higher initial costs.
90% of maximum light output of 2–5 Magnetic ballasts for low-wattage lamps
minutes (min). operate the lamps at 60 hertz (Hz);
If an HID lamp is extinguished, it must electronic ballasts can operate the lamps
cool before being restarted. Restrike time at 60 Hz or at much higher frequencies,
is defined as the time required before the such as 25 kilohertz (kHz).
lamp will restart (IESNA 1993), although Table 1 on p. 19 lists the manufacturers
some manufacturers publish restrike of ballasts for HID lamps and their
times as the time required for the lamp to telephone numbers. Specifiers should
cool, restart, and reach 90% of maximum contact ballast manufacturers for compre-
light output. The time required for the hensive ballast information and specifica-
lamp to restart and warm up again is tions before specifying a ballast. Every
usually longer than the warm-up time for ballast should have an American National
a cold lamp. HPS lamps have shorter Standards Institute (ANSI) code that
restrike times than MH lamps. NLPIP did identifies the electrical operating charac-
not measure warm-up or restrike times for teristics of the lamp it will operate.
this report.
Electronic Ballasts for Low-Wattage
Fading HPS Lamps
In addition to light [between 380 and Philips Lighting’s high-CRI HPS lamps
770 nanometers (nm)], low-wattage HID operate on series controller ballasts, also
lamps also emit ultraviolet (UV) energy called hybrid ballasts, from Advance
(between 280 and 380 nm). MH lamps Transformer Co. These ballasts use an
usually emit more UV energy than do electronic circuit in series with a mag-
HPS lamps. If objects such as denim blue netic transformer and operate the lamps
jeans, meats, and museum artwork and at 60 Hz. Philips claims that these ballasts
artifacts are exposed to high levels of compensate for variations in supply
these wavelengths for an extended time, voltage and thus provide uniform light
the color of these items may fade. Both source color characteristics within a – 10%
MH and HPS lamps emit more UV than line voltage variation and constant lamp
incandescent lamps. Specifiers should voltage and power over lamp life (Philips
consult lamp manufacturers to determine Lighting 1991; Brabham 1990).
6 Specifier Reports: HID Accent Lighting Systems
Electronic Ballasts for Low-Wattage decreases light output, increases CCT,
MH Lamps and decreases lamp power. Lamps oper-
ated by electronic ballasts maintain more
NLPIP identified two manufacturers of
consistent performance than those
electronic ballasts for low-wattage MH
operated by magnetic ballasts because
lamps: OSRAM SYLVANIA INC. and WPI
electronic ballasts maintain constant
Electronics. According to OSRAM
voltage to the lamp regardless of the
SYLVANIA, its ballast is designed specifi-
supply voltage.
cally to operate its own 70-W double-
NLPIP evaluated the ability of ballasts
ended MH lamp.
to maintain lamp light output, CCT, and
WPI’s ballasts operate lamps at 60 Hz,
power during fluctuations of the supply
whereas OSRAM SYLVANIA’s ballasts
voltage (see “Ballast Evaluations” on p. 14
operate lamps at between 20 and 25 kHz.
for more information). NLPIP varied the
Lamps operated at a frequency above
supply voltage to four 70-W double-ended
8 kHz can experience acoustic resonance,
MH lamps operating on 120-volt (V),
which can cause light output to fluctuate
60-Hz magnetic and 120-V electronic
and lamps to flicker or even extinguish.
ballasts and obtained the following results:
OSRAM SYLVANIA’s ballast operates
lamps at a center frequency of 22.5 kHz
and periodically shifts frequency up or
down 2.5 kHz to overcome acoustic
resonance, stabilize lamp operation, and
minimize flicker (Faehnrich et al. 1988).
Lamps operated at 60 Hz do not experi-
ence acoustic resonance (Rasch and
Ballast and voltage effects on lamp performance
Statnic 1991).
Magnetic Electronic
Results of NLPIP Ballast Evaluations At130V At110V At130V At110V
Fluctuations in the supply voltage can Lamp
+16to+26% -18to-28% 0to+2% -2to-6%
affect an MH lamp’s light output, color, LightOutput
and power. Depending on the ballast
NoChangeto NoChangeto
CCT -100to-400K +300to+600K
used, higher voltage generally increases -100K +200K
light output, decreases CCT, and in-
LampPower +13% -14to-29% NoChange NoChange
creases lamp power; lower voltage
Specifier Reports: HID Accent Lighting Systems 7
Figure 5. Components of an
Adjustable Accent Luminaire
Recessed in a Ceiling
Luminaires
9
10
8
NLPIP evaluated the ease of aiming and
1
relamping of recessed and semi-recessed
adjustable luminaires and track luminaires 2 7
from seven manufacturers for this report. 6
Table 1 on p. 19 lists the manufacturers
of HID accent luminaires and their
telephone numbers. Tables 7–12 on pp.
32–45 contain manufacturer-supplied
information for HID accent luminaires. 3
NLPIP’s methods for evaluating lumi- 4 5
naires are described in “Luminaire 1 Luminaire housing
2 Junction box
Evaluations” on p.14. The results of
3 Trim
NLPIP’s evaluations of HID accent
4 Reflector cone
luminaires are listed in Tables 13 and 14 5 Ceiling
on pp. 46–47 and described in “Results of 6 Ballast
7 Yoke assembly
NLPIP Luminaire Evaluations” on p. 11.
8 Lamp socket (Adapted with permis-
9 Lamp sion from Kurt Versen
10 Upper reflector Inc. 1995)
Luminaire Types
Recessed and semi-recessed adjust-
able luminaires. Recessed and semi-
recessed HID accent luminaires appear
very similar to recessed and semi-
recessed accent luminaires for incandes-
cent lamps. Figures 5 and 6 illustrate the
components used in typical recessed and Figure 6. Components of an
semi-recessed adjustable accent lumi- Adjustable Accent Luminaire
naires, respectively. Semi-Recessed in a Ceiling
Track luminaires. Track and track 10
6 1
luminaires for HID lamps are similar to
track luminaires for incandescent lamps.
They mount similarly, have similar
2
optional accessories for additional optical
control, and allow track heads to be
electrically controlled individually or in 7
groups. The track head is the part of the 8
luminaire that moves along the track and 5
usually comprises the lamp housing, 3
lamp, socket, and reflector cone. The 9
track head also typically contains the
1 Luminaire housing 4
ballast for the HID lamp, unless the 2 Junction box 11
specifier chooses a monopoint mount,
3 Trim
when the ballast is recessed into the 4 Reflector cone
ceiling plenum. 5 Ceiling
The track can be recessed into the 6 Electronic ballast and ignitor
7 Yoke assembly
ceiling, mounted to the surface of the
8 Lamp socket
ceiling, or suspended from the ceiling
9 Lamp (Adapted with permis-
(pendant mounted). The track luminaires
10 Transformer sion from INDY Lighting
can be suspended from the track with a 11 Lamp housing Inc. 1995)
8 Specifier Reports: HID Accent Lighting Systems
pendant mount, as shown in Figure 7. prevents damage to the lamp and ballast if
Some individual track luminaires can be there is a voltage surge.
mounted directly to a junction box in the
ceiling without a track (see Figure 8).
Adjustability and Maintenance
This option usually is called a mono-
point mount. NLPIP evaluated the ease of use of some
Manufacturers of track luminaires for of the components illustrated in Figures 5
HID lamps offer accessories that change and 6, some of which are used to adjust
the optical control of the luminaire. These and aim HID accent luminaires. When
options include spread lenses that convert these components are easy to use, the
a round beam into an elongated beam and labor costs of installing and maintaining
barn doors, louvers, and tubular shields the luminaires are minimized. Components
(“snoot” shields) that help prevent direct that are easy to use also make the lumi-
glare. Specifiers should request the naire less susceptible to being incorrectly
photometric information of a luminaire adjusted or damaged during installation
with any desired options before specifying and maintenance.
the options. Filters also are available in
many colors to change the color appear- Yoke assembly. The yoke assembly is
ance of the light. used to aim the lamp. Some manufactur-
Tracks have one, two, or three circuits, ers provide mechanisms on the yoke so
allowing switching of up to three groups that it can be locked into position once
of track heads. An individual track head the luminaire is aimed. Some lockable
can also have its own switch at its connec- yokes have wing nuts that can be tightened
tion to the track so that each head can be by hand, while other yokes have bolts that
switched independently. Some track should be tightened with a wrench.
luminaires offer a ballast fuse, which
Figure 7. Pendant-Mounted Figure 9. Horizontal and Vertical
Track Luminaire Aiming with Yoke Assembly
a. Horizontal
Horizontal rotation
Lower ring allows
0(cid:176) horizontal rotation
of yoke assembly
b. Vertical
Figure 8. Monopoint Mounting of a Aimed angle
Track Luminaire
0(cid:176) aiming
Yoke assembly
allows vertical
adjustment
0(cid:176)
Specifier Reports: HID Accent Lighting Systems 9
Adjustable luminaires can be aimed Figure 10. Interchangeable Reflectors
vertically and horizontally using the yoke
assembly as illustrated in Figure 9 on p. 9.
Recessed adjustable luminaires typically
have vertical aiming ranges from 0–45(cid:176) ,
where 0(cid:176) is straight down, and horizontal
rotation ranges from 0–360(cid:176) . Semi-
recessed adjustable and track luminaires
typically have vertical aiming ranges from
0–90(cid:176) and horizontal rotation ranges from
0–360(cid:176) .
Upper reflector. The upper reflector
directs light out of the luminaire in a
specific direction and pattern. Three
reflector system types are used in accent
luminaires: interchangeable, adjustable, Figure 11. Adjustable Reflector
and fixed.
An interchangeable reflector system
allows a user to change the reflectors on-
site if necessary. Luminaires that use
tubular MH and HPS lamps often have
interchangeable reflector systems. Manu-
facturers commonly offer reflectors having
spot, medium flood, and flood distribu-
tions. The number of available reflectors
and distributions varies by luminaire.
Figure 10 shows a luminaire that has two
interchangeable reflectors.
Adjustable reflector systems usually
have a mechanism that moves the
reflector which changes from a spot to a some viewing angles. A semi-specular
flood distribution. Luminaires with finish scatters the light and provides a
adjustable reflectors usually house T10 brighter cone appearance.
HPS lamps. Figure 11 shows a luminaire Reflector cones for recessed adjustable
with an adjustable reflector. accent luminaires are typically round,
A fixed reflector system is neither although rectangular cones are available.
adjustable nor interchangeable. Lumi- Cones are available with either a flat or
naires for ED17 and B17 lamps have fixed angled cut, as shown in Figure 12 on
reflector systems and upper reflectors. p. 11. Angle-cut cones typically are avail-
A PAR lamp has an integral reflector, able in 20, 30, 35, and 45(cid:176) angles; some
so luminaires for PAR lamps do not manufacturers offer custom angles. The
require an upper reflector and have a angle-cut cone enables the specifier to aim
fixed reflector. the lamp at greater vertical angles than
the flat-cut cone allows, without trapping
Reflector cone. The reflector cone as much light within the luminaire.
provides a finished appearance to the Manufacturers use either springs or
luminaire, redirects any stray light from tension clips to attach reflector cones to
the upper reflector, and controls glare. the luminaire. Springs usually attach to
Reflector cones are available in either the reflector cone and to the yoke and pull
specular (polished) or semi-specular the reflector cone flush with the trim ring.
finishes in colors such as clear, gold, Tension clips usually mount on the back
black, bronze, and pewter. The most side of the reflector cone and require the
common combination of finish and color is installer to push the reflector cone flush
specular clear, which is a shiny silver with the trim ring. If the cone is not flush,
finish. Specular cones often appear dark light can escape between the reflector
because they reflect almost no light at cone and trim ring. Sometimes manufac-
10 Specifier Reports: HID Accent Lighting Systems