APPLICATION NOTE
An In-Depth Examination of an Energy
Efficiency Technology
Efficient Lighting
Using Full-Size
Fluorescent Lamps
and Fixtures
Summary ............................................. 1
How This Technology Saves
Energy ................................................. 2
Types of Energy-Efficiency
Measures ............................................. 3
Applicability ........................................ 8
Field Observations to Assess
Feasibility ............................................ 9
Estimation of Energy Savings ......... 11
Cost and Service Life ....................... 11
Laws, Codes, and Regulations........ 13
Summary
Fluorescent lighting is the preferred
system for general lighting in many
commercial applications. Many types of
ballasts, lamps, and fixtures are available for energy-efficient, cost-effective,
high-quality installations. This Application Note reviews these components,
including their operating characteristics
and application.
Full-sized fluorescent systems (those
with lamps an inch or more in diameter)
can be optimized in a number of ways.
Simply removing lamps in overlit areas
often yields large energy savings and
rapid paybacks. The right lamp-ballast
combination can improve efficiency significantly. For example, nearly any facility using magnetic ballasts and T12
lamps can be retrofitted with electronic
ballasts and T8 lamps for energy savings. Improving fixtures so that light is
distributed efficiently can also reduce
energy use as well as improve visual
comfort.
Energy savings of 50 to 80 percent are
possible with retrofits of old fluorescent
systems. Designs for new construction
can also be significantly more efficient
than conventional practice. Continued
energy savings can be assured by
proper maintenance, including a program of inventory control, and a welldesigned operation and maintenance
program that includes relamping and
cleaning schedules.
Definitions of Key Terms ................. 14
References to More Information...... 15
Major Manufacturers ........................ 15
Copyright © May 1997, Pacific Gas and Electric Company, all rights reserved.
Revised 4/25/97
How This Technology
Saves Energy
A fluorescent lighting system (Figure 1)
consists of a line voltage and/or lowvoltage controls to switch the lights
on/off or dim them; a ballast1, which is a
power regulator; a lamp which gener-
visible photons, or “fluoresce.” About 22
percent of the energy used by the lamp
is converted to light. Altering the phosphors produces different qualities of
white light.
While several mechanisms exist to
strike the arc, all fluorescent lamps use
a power conditioning device called a
20a Lighting Circuit (480/277v or 208/120v)
Line Voltage
Switching
Light Fixture
Ballast
Breaker
Panel
Lamps
Other
Lighting
Circuits
Other
Switched
Zones
Other
Lights on
Switch
Low Voltage Controls
(Timers, Occupancy, Dimming, etc.)
Figure 2: Schematic of Fluorescent Lighting System (Source: E Source)
ates light; and a fixture that houses the
lamp and determines distribution of the
light. A luminaire is a complete lighting
unit including lamp(s), ballasts, reflectors, and shielding and diffusion components.
ballast which amplifies line voltage to
start the lamp, and limits current to
maintain its arc. Ballasts also ensure
control and safety in a variety of failure
modes. For optimum performance, a
particular ballast must match a specific
lamp’s current requirements.
The basic fluorescent lamp contains
low-pressure mercury vapor and inert
gases in a partially evacuated glass
tube (Figure 2) lined with specially formulated compounds called phosphors.
The action of an electric arc in this atmosphere causes the phosphors to emit
Visible Photon
-
UV Photon
+
+
+
Hg
+
1
Bold italicized words are defined in the section
titled “Definition of Key Terms”
©
PG&E Energy Efficiency Information “Full-Size Fluorescents”
Figure 1: Fluorescent Lamp
Operation (Source: E Source)
Page 2
Three different methods can start fluorescent discharge in lamps. With a few
exceptions, the starting method of the
lamp and the ballast must match.
(Mismatches either do not start, or burn
out the lamp, the ballast, or both.) Preheat starting is an older method that
causes flickering for several seconds
before the lamps ignites. Rapid starting
is the most common method; lamps
come on within a second with only a
brief flicker. Instant starting jolts the
lamp with a high-voltage (400 to 1,000
V) pulse that starts it in under a tenth of
a second.
Baseline Fluorescent Lighting
System
The typical or “baseline” system in
commercial facilities uses 4-foot lamps
in a 2’ by 4’ fixture installed in the grid of
a suspended ceiling. The lamps are one
and one-half inches in diameter, commonly called “F40/T12,” where “40” indicates nominal power consumption in
watts and “12” denotes diameter in
eighths of an inch. The ballast uses
magnetic transformers operating at line
frequency (60 cycles per second). Although there are more efficient types,
today’s magnetic ballasts are sometimes called “energy-efficient magnetic
ballasts” because they are slightly improved from those manufactured before
the early 1980s.
Energy-Efficient Fluorescent
Lighting System
An energy-efficient fluorescent system
look much like the baseline, but its
components and configuration significantly reduce energy consumption. If
overlighting existed, there may be fewer
©
lamps in the fixture. The fixture may be
below the ceiling, lighting ceiling and
walls as well as floor. There may be a
metallized reflector in the fixture to more
efficiently distribute the light from the
lamps. Instead of T12s, lamps will be
skinnier “T8” units, only one inch in diameter. The ballast will use electronic
switching to regulate power to the
lamps, operating at high frequency
(greater than 20,000 cycles per second). Compared to T12/magnetic technology, T8 lamps and electronic ballasts
have better lumen maintenance, an optimal
operating
temperature
that
matches conditions in fixtures more
closely, and higher intrinsic efficiency
because of the greater frequency of excitation in the arc.
Types of EnergyEfficiency Measures
Fluorescent lighting can be optimized in
several ways: correcting overlit situations by delamping, using the highest
efficacy lamp-ballast systems, and applying appropriate control strategies.
Each of these measures is discussed
below.
Savings from Reducing Overlighting
Many spaces simply have too much
electric lighting, and substantial energy
can be saved by reducing total light
output. This can be done by removing
lamps, converting 3- or 4-lamp fixtures
to 1-, 2-, or 3-lamp fixtures, retrofitting
with lower output lamp-ballast systems,
or using dimming or other control systems. Such retrofits typically provide
PG&E Energy Efficiency Information “Full-Size Fluorescents”
Page 3
large energy savings and rapid paybacks. Reducing light output should be
done with attention to the quality of the
resulting light, its distribution, surface
brightness, and glare potential.
Illuminance is measured in footcandles, using an illuminance meter. The
Illuminating Engineering Society of
North America recommends typical average illuminance levels in its Lighting
Handbook, 8th edition. If measurements
in a space show that average levels are
significantly higher than these, the
space is a candidate for some kind of
light output reduction.
Reducing overlighting saves energy and
reduces the cost of lamp and ballast replacement. There are no disadvantages
as long as the distribution of light is not
compromised.
Case Study: Light Levels Affect
Efficiency Opportunities at
University Facilities
At a large university, foot-candle measurements showed some spaces overlit
and some underlit. In one building,
classroom light levels exceeded 75
footcandles, and one-third of the lamps
were removed to reduce light to the design level of 60 footcandles. With a
switch to electronically ballasted T8
lamps, this resulted in energy savings of
over 50 percent with a payback of under
two years.
In the nearby library, however, half the
ceiling-mounted fluorescent fixtures had
been disconnected years ago as an
“energy savings” measure and light levels were below recommendations. A retrofit with electronically ballasted T8
lamps increased light output to design
©
levels, with minimal energy savings and
a payback of nearly 5 years.
Improving Fixture Efficiency
Distributing light efficiently is as important as generating it efficiently, and can
dramatically affect visual comfort.
Fixture efficiency refers to how well the
unit gets the light from the lamps out of
the fixture. The main components of a
typical fluorescent direct downlight fixture are the housing, a lens or louver
system, and possibly a reflector. See
Figure 3.
Reflector Retrofits
Reflectors are specially shaped retrofittable metal sheets that improve (or
attempt to improve) the efficiency of and
distribution of light from conventional
ceiling-mounted fluorescent downlight
fixtures. They can significantly decrease
the internal losses of fixtures and widen
or narrow their light distribution, often
allowing significant energy savings from
delamping.
Fixture Housing
Reflector
Parabolic Louver
Figure 3: Typical Fluorescent
Downlight Fixture (Source: Metal Optics)
PG&E Energy Efficiency Information “Full-Size Fluorescents”
Page 4
Reflectors are available from over two
dozen manufacturers. Innovative designs, mounting methods, and usable
lamp combinations have improved performance and simplified installation, and
many millions of square feet of space
have been upgraded using them. A typical retrofit, including labor, costs about
$75 per 2’ x 4’ fixture.
Understanding reflector technology is
simplified by remembering a few rules:
• Reflector design—not material—is
the key to performance.
• Highly efficient reflectors often require relocation of existing lamps to
avoid glare and provide optimal light
distribution.
• No single retrofit reflector kit will
work well in all situations. Even in a
building with one type of fixture, several
reflectors may be used, each designed
for the best pattern of light distribution
for its position.
• The potential to improve fixture
efficiency depends mostly on the geometry and efficiency of the existing
fixture, not that of the reflector kit.
• Savings analysis of proposed retrofits is best done room by room, not by
fixture type throughout a large or diverse facility.
• Delamping is the heart of reflector
energy savings. A frequent claim is
that reflectors will allow 50 percent delamping with little or no reduction in the
fixture’s light output. Apart from the
temporarily higher lumen output of
newly replaced lamps, this is a difficult
©
goal to achieve, and is less a function of
how good the reflector is than how bad
the existing fixture is. In any application,
delamping should be considered carefully, bearing in mind that it may also be
possible to delamp without a reflector.
Case Study: Reflector Retrofit. In
1986, the Facilities Management Office
of Columbia University renovated its
ceiling lighting to improve energy efficiency. The retrofit included delamping
and adding specular reflectors to enhance the light reaching the workplane.
One lamp was removed from each of
the three-lamp 2 x 4 recessed fixtures,
and the single-lamp magnetic ballast
serving it was disconnected. One of the
remaining 40-watt T12 lamps was exchanged for a Thrift/Mate® lamp
equipped with a current reducer that cut
light output and remaining wattage by
30 percent. The built-in task lighting
fixtures (each using a single F40 T12
lamp) were not altered.
Ambient light levels in the open-plan
office area dropped from about 35 footcandles (fc) to 20 to 25 fc, Levels under
the task lights just above each desk remained at 120 to 150 fc. Some occupants found this contrast so great that
they kept the task lights off, and used
incandescent desk lamps instead. A
more careful upgrade was pursued in
late 1992. All lamps were replaced with
3,500 K T8s, two-lamp instant-start
electronic ballasts replaced the magnetic units, and better specular reflectors were installed. Task light fixtures
were equipped with plug-in power reducers that reduced light output and
wattage by 50 percent.
As a result, ambient light levels were
raised to 30 to 35 fc while task light lev-
PG&E Energy Efficiency Information “Full-Size Fluorescents”
Page 5
els dropped to 60 to 70 fc. The better
color rendering of the T8 lamps improved the overall appearance, and the
reduced contrast between task and ambient eased complaints of glare and excessive brightness. Total wattage was
cut another 20 percent. Overall payback
was slightly over three years, and occupants liked the change.
Diffusers, Lenses, and Louvers
Diffusers and lenses are similar devices: thin plastic sheets covering recessed fluorescent fixtures at ceiling
level. They differ dramatically in efficiency, however. Diffusers are milkywhite translucent sheets that disperse
light nearly equally in all directions.
They
are
notoriously
inefficient
(approximately 70 percent) because of
their high light absorption. Lenses redirect light rather than diffuse it, and efficiency can be as high as 95 percent.
Lenses can be differentiated from diffusers by their clear material and micropatterns of surface prisms.
Most lenses and diffusers are made
from one of three types of plastic:
acrylic, polycarbonate, or polystyrene.
Many older units were made from polystyrene because it is the cheapest. But
it also has the highest flame spread and
smoke production, and is unacceptable
to most building codes. Polystyrene
lenses also yellow more quickly than
other plastics, making them good candidates for replacement during an upgrade. Polycarbonate is the strongest,
ideal for outdoor and institutional fixtures subject to abuse, such as in prisons. It is also the most expensive, and
yellows with age and exposure to UV
radiation. Acrylic is the choice for most
fixtures. It exhibits low flame spread and
©
smoke production, can be stabilized
against UV degradation and costs less
than polycarbonate.
Louvers are used to control glare from
ceiling-mounted downlight fixtures. The
most common type is the parabolic louver, which uses carefully curved reflective surfaces that pass light downward
but cut off any view of the lamp from
other angles. Fixtures with welldesigned parabolic louvers are very optically efficient, which may allow energy
savings by reducing fixture counts.
However, they can also create a “dark
ceiling” effect that can make a space
appear gloomy, so should be specified
with caution. Areas that support intensive work on video display terminals
(VDTs) are a common application for
parabolic louvers, as the dark ceiling
effect minimizes the reflected glare in
the VDTs.
High-Efficiency Lamp-Ballast
Systems
There are many choices for upgrading
lamps and/or ballasts in full-size fluorescent systems. The system most
common in commercial facilities uses
T12 lamps and magnetic ballasts.
“Energy Saving” Lamps
In the 1970s, manufacturers found that
adding krypton to the standard argon
gas fill suppressed both energy consumption and light output. Thus was
born the “energy saving” (ES) lamp—a
term that can be misleading. Lamp-only
efficacies are relatively high, but these
lamps are no more efficient than standard magnetically ballasted T12s, and
electronically ballasted T8s can beat
them in most cases. ES lamps now
PG&E Energy Efficiency Information “Full-Size Fluorescents”
Page 6
make up a substantial part of the available fluorescent sources. Nearly all are
T12s, however, and they have several
operational limitations. Brand names for
this lamp category include GE’s
WattMiser®, Osram Sylvania’s SuperSaver®, Philips’ Econowatt, and DuroTest’s WattSaver®. The primary attraction is their drop-in energy savings potential for the multitude of existing T12
applications, especially those that are
overlit. Some facility managers prefer
ES “retrofits” since no ballast change is
required, and thus no need for any real
electrical work. A typical ES lamp-only
retrofit costs about $7 per lamp including labor, produces 15 percent energy
savings with a 10 percent loss of light
output, and has a simple payback of
about two years.
ES lamps have a higher rate of lumen
depreciation than standard lamps, are
very sensitive to operating current, and
cannot be deeply dimmed or run on lowballast-factor ballasts (those that intentionally provide reduced light output).
They also perform poorly in cold temperatures and should not be run with
cathode-cutout ballasts. Perhaps worst,
they may either impede the path to future upgrades (such as dimming) or give
the impression that because “energy
saving” lamps are in place, maximum
efficiency has been achieved. When investigating ES lamps, compare rated
“mean lumens” with “initial lumens” to
assess long-term performance, and remember that their primary means of
wattage reduction is lower light output.
Electronic Ballasts
Fluorescent technology took a major
leap forward with the electronic ballast,
using semiconductors to rectify incom©
ing 60 Hz to direct current (DC), and a
high-frequency inverter to convert DC to
20,000 Hz (or higher) current to the
lamp. Other solid-state components
control or filter power to minimize harmonic distortion, maintain a high power
factor, and shape the power waveform.
Electronic ballasts typically cut internal
power losses 3 to 8 watts per ballast
(from about 16 watts per ballast), operate lamps 10 percent more efficiently,
cut losses by driving more lamps per
ballast, are less affected by temperature
and voltage variations, automatically
de-energize failed lamps, improve lamp
efficiency by increasing the optimal
lampwall temperature, and eliminate
visual flicker. These improvements can
combine to create very large energy
savings—up to 90 percent.
A typical electronic ballast/T8 lamp retrofit using 2-lamp ballasts costs about
$30 per lamp (including all materials
and labor), saves 35 percent of energy
while boosting light output by 7 percent,
and has a payback of 4 to 5 years. Using four-lamp ballasts cuts costs further
while producing greater savings; payback drops to under 3 years.
Hybrid Ballasts
Ballasts that cut out cathode heating
after starting and running the lamp
briefly are known as hybrid ballasts.
These ballasts use magnetic technology
to power the lamp and electronic technology to control power to the cathodes.
(“Hybrid” is also used by some to describe discrete electronic ballasts. Here,
we equate “hybrid” ballasts with cathode-cutout operation at 60 Hz.) These
60 Hz devices are very popular for energy savings, since they power T8 or
PG&E Energy Efficiency Information “Full-Size Fluorescents”
Page 7
T12 lamps with some of the efficiency
gains of electronic ballasts while costing
significantly less.
Light output and efficacy of hybrid ballasts are about 5 to 7 percent lower than
that of equivalent electronic ballasts.
Hybrids are limited to two-lamp varieties, and lamps are wired in series. Most
sources agree that eliminating cathode
heating does not reduce lamp life. However, combining low ballast factors
with cathode cutout may reduce lamp
life (just as with instant-start ballasts),
because lamp current and attendant
cathode heating are significantly reduced. Hybrids also should not be used
in cold locations.
Control Strategies
Controls should be considered after
establishing the correct lighting level,
improving fixture efficiency, and using
high-efficiency lamps and ballasts. Like
other systems, fluorescents can take
advantage of a multitude of control
systems to create energy savings.
Energy Efficiency Measure
Reduce lighting levels
Install reflectors in fixture
Install new acrylic lenses
Install new parabolic louvers
Install electronic ballasts and T8 lamps
Control strategies
Strategies include simple manual on-off
systems that control individual lamps
within fixtures or groups of fixtures, occupancy sensor control, countdowntimer control (also called elapsed-time
switches), timeclock switches, building
energy management system strategies
such as “sweep” systems or scheduling
control, on-off photocell control, and
step-dimming or continuous dimming
using manual or automatic photocells.
Applicability
Full-size fluorescent systems are most
appropriate for general lighting in commercial, institutional, and industrial
spaces, except those with ceilings over
16 feet or so, which may be better
served by high-intensity discharge
(HID) lighting. Several energy-efficient
fluorescent options exist for virtually any
commercial lighting application.
Measures described above have the
general applicability shown in Table 1.
Application
Light levels exceed IES recommendations.
Existing fixtures provide poor light distribution (too wide or narrow); delamping retrofit
is contemplated; existing fixture is extremely
dirty or worn.
Old lenses worn, dirty, or yellowed, or made
of inferior material (polystyrene).
Glare is a problem for users, such as people working at video display terminals.
Nearly any facility using magnetic ballasts
and T12 lamps can make this change costeffectively.
Lights after business hours or when space
unoccupied; or on in brightly daylit spaces.
Table 1: Common Fluorescent System Applications (Source: E Source)
©
PG&E Energy Efficiency Information “Full-Size Fluorescents”
Page 8
Ballast Application
Field Observations to
Assess Feasibility
The following are general guidelines for
choosing among available ballasts:
• T8 lamps with non-dimming high
frequency electronic ballasts gives
excellent energy efficiency, wellestablished performance, and a wide
variety of suppliers. Most general illumination applications can use this simple
prescription. Reasonable light quality is
virtually assured. With this combination,
technological concerns give way to
questions of lighting design—mostly involving the distribution of light.
• Instant-start ballasts provide the
best efficacy and lighting utility. In applications for which no instant-start
products exist, or where duty cycles are
shorter than three hours, rapid-start
ballasts are the logical choice.
• For applications that suggest
emerging technologies, try products
on a small scale. Inspecting other installations can be helpful, but there is
no match for a trial under your specific
conditions, where any problems should
show up quickly.
• Developing a rigorous specification is an excellent way to protect the
organization purchasing the equipment.
• Third-party technical evaluations
are standard for lighting equipment;
any reputable supplier should be able to
provide independent reports, such as
the common ETL Lab tests, for their
products.
©
This section discusses observations
and checks to ensure that a fluorescent
system is appropriate for an application
and is installed and working properly.
Also covered are actions that can help
sustain energy savings achieved by efficient fluorescent systems.
Related to Applicability
The essential factor to consider is the
task for which lighting is needed. The
right lighting technology depends on the
task, level of quality desired, and
amount of light required. General guidelines on lighting design, which are observable in the field:
• The eye is more sensitive to contrast and differences in luminance
than to absolute lighting levels, so good
fluorescent design controls variations in
luminance.
• Lighting quality will usually be
much better served by removing
sources of glare and veiling reflection
than by supplying more light.
• Do not confuse requirements for
ambient lighting with the light needed
on tasks. It is often more attractive, and
clearly more energy efficient, to maintain ambient lighting at 10 to 30 footcandles and use efficient task lighting to
raise light levels on work surfaces to
recommended levels of 50 or more footcandles.
PG&E Energy Efficiency Information “Full-Size Fluorescents”
Page 9
• An easy way to check for magnetic vs. electronic ballasts is to use a
“strobe top”—typically available cheap,
or free, from sales representatives of
ballast manufacturers such as Motorola
or Magnetek. Spin the top under the
lighting system; if you see pattern lines,
the lights are operating at 60 Hz and
use magnetic ballasts that are retrofit
candidates; if the pattern is smooth with
no lines, the lights use high-frequency
electronic ballasts.
• Use the highest practical CRI
One easy field test is to check light levels. Many spaces simply have too much
electric lighting, and substantial energy
savings can be had by reducing total
output. A simple check using a light
meter can help determine whether a
space has too much light.
Related to Energy Savings
For continued energy savings, system
maintenance is essential. Maintaining
light quality, output, and energy savings
requires three actions:
(color rendering index) lamp whenever possible. Objects and people not
only look better, but object clarity is actually improved. High-CRI lamps can
sometimes make up for a light level otherwise considered marginal.
• Design systems with components
• Lamps with high color tempera-
nance techniques, including cleaning
and relamping
tures at low light levels make spaces
appear cold and dim. Conversely, lamps
with low color temperature at high levels
of illumination make spaces look overly
colorful. Sources at about 3,500 K look
good over a wide range of illuminances.
The color temperature of full-sized fluorescent lamps is usually printed on the
glass envelope near one of the end
caps.
• There are general rules for spacing fixtures which help avoid major
footcandle variations within a space.
For example, placing a ceiling fixture
closer than one foot to a wall creates a
“hot spot” on the wall. Unless there is a
logical reason to vary lighting levels
(such as merchandising), avoid variances at task height directly below and
between fixtures by observing proper
spacing.
©
that minimize light loss over time, are
easy to maintain, and use the fewest
types of lamps
• Train personnel in proper mainte-
• Control purchasing and inventory
to ensure that only the right replacement components are available.
Field observations that may indicate inadequate maintenance include:
• Are the right replacement lamps
being used? Retrofits or installations
using expensive lamp types for higher
output or longer life can be thwarted in
the future by unauthorized or incorrect
replacements. Inspection can reveal if
this is taking place—one indicator is if
the color temperature of lamps does not
match.
• Are fixtures dirty? Are several
lamps burned out and in place? This
can reduce the amount of light and
prompt occupants to add inefficient task
PG&E Energy Efficiency Information “Full-Size Fluorescents”
Page 10
lighting or take it upon themselves to
replace a lamp—perhaps with an inappropriate unit.
• Are lights on at night when no one
is using the space? This might indicate need for a different control system,
or altered maintenance practices.
Estimation of Energy
Savings
With good design, lighting energy use in
most buildings can be cut by half to
more than 80 percent, compared to a
conventional, inefficient system 10 to 30
years old. The internal lighting load in
conventional office buildings of those
ages may be as much as 3 watts per
square foot. A building with more modern equipment is likely to require less
than half that and a state-of-the-art
system may use as little as 0.5 watts per
square foot.
Standard Savings Calculation
The following equations are recommended for estimating energy savings
from changes to the capacity of a fluorescent lighting system. Alternative
equations and more information concerning such estimates can be found in
the CEE program documentation filed
with the CPUC.
©
kWsavings = # fixtures ×
(Watts / fixturebase − Watts / fixtureas−built )
×Utilization_ factor ÷ 1,000
kWhsavings = kWsavings × hoursas−built
× HCIFkW
thermtakeback = kWsavings × 0.034 × hours
× HCIFheat / heating _ efficiency
HCIFkw and HCIFheat are the heat/cool
interaction factors which account for reduced electric air conditioning loads
and increased gas heating loads, respectively, due to the decreased lighting
energy. A table of these factors is in the
program documentation.
Utilization_factor is the ratio of “on” fixtures to the total installed fixtures. This
factor accounts for fixtures or lamps
which are not operational due to:
burned out lamps, failed ballasts, or not
turned on.
Cost and Service Life
Factors That Influence Service
Life and First Cost
Fluorescent lamp ballasts typically last
40,000 to 100,000 hours and cost from
$5 to $50 each, depending on type.
Four-foot fluorescents typically cost
from $1 to $10 each, although specialties such as eight-foot very-high-output
lamps can cost $20 or more. In general,
prices climb for lamps with 80+ CRI or
more, and for those in unusual sizes.
PG&E Energy Efficiency Information “Full-Size Fluorescents”
Page 11
Incandescent
1-3
7.5-9
Preheat
9-12
HO/VHO
Instant
7.5-15
18-20
Standard Rapid
20-24
0
Premium
20
10
30
Rated Lifetime (Thousands of Hours)
These lifetimes are based on three hours of operation per start.
Figure 4: Rated Lifetimes for Fluorescent Lamp Types (Source: E Source )
Fluorescent lamp life varies according
to type. Lifetime is the statistical point at
which 50 percent of the lamps in a given
batch have failed. The primary issues in
fluorescent longevity are the method
and frequency of starting. Fluorescent
lamps fail most commonly when their
cathodes, weakened by erosion through
starting and maintaining the electric arc,
physically break. Fluorescent lamps are
rated at three hours of continuous operation per start, unlike HID lamps,
which are rated at 10 hours per start.
Because of the impact of starting
method on lamp life, the different fluorescent groups exhibit varying lifetimes.
Figure 4 shows these ranges for a
three-hour duty cycle. Lamp life may be
reduced by 25 to 50 percent when operated with low-ballast-factor electronic
instant-start ballasts. “Premium” lamps
are built with heavy-duty cathodes and
thick phosphor coatings for extended
lifetimes.
The PG&E CEE program assumption for
fluorescent fixtures and ballasts is 16
years.
Operation and Maintenance
Requirements
Operation and maintenance practices
strongly influence energy savings of
fluorescent lighting systems, as noted
above. Energy dollars can be directly
lost through poor maintenance such as
failure to keep lighting controls operative (which increases burn time) and
failure to relamp promptly, leading occupants to install their own (usually incandescent) task lighting.
The following are some tips from practitioners for maintaining energy savings:
• During system design, minimize the
variety of lamps used. specific sockets.
• Choose fixtures that use lampspecific sockets.
Typical Service Life
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PG&E Energy Efficiency Information “Full-Size Fluorescents”
Page 12
• Convert lighting upgrade specifications into purchasing specifications.
Lamp Group
Wattage
Minimum
Efficacy
(lm/W)
Minimum
CRI
• Regularly train lighting maintenance
4-foot Medium Bipin
>35
<35
75
75
69
45
personnel.
2-foot U-shaped
>35
<35
68
69
64
45
• Budget and train for group relamp-
8-foot Slimline
>65
<65
80
80
69
45
ing.
8-foot HO
>100
<100
80
80
69
45
• Focus responsibility for lighting system maintenance on one person instead
of diffusing it among several.
Table 2: EPACT Lamp Standards
Laws, Codes, and
Regulations
• General lighting maintenance tasks
include:
• Lamp replacement or “relamping.”
EPACT
Spot relamping—lamp replacement as
needed, after burnout—is often practiced. However, group relamping—
which is changing groups of lamps that
have reached about 70 percent of their
rated life—will help maintain lighting
quality, and usually reduces labor costs.
The 1992 National Environmental Policy
Act (EPACT) legislation has a significant
effect
on
fluorescent systems. EPACT’s lamp requirements cover many (but not all) types of
fluorescents.
• Fixtures should be cleaned at
each relamping to maintain light output.
• Lenses and lamp sockets should
be replaced at every group reballasting.
• When ballasts eventually require
replacement, take care to reballast with
the same types of units. Incorrect replacement can reduce light output
and/or increase wattage.
• When
reballasting, fluorescent
lamp sockets should also be replaced.
Since the last ballast replacement, it is
likely that sockets have sufficiently oxidized to create resistance, shortening
lamp life and make starting more difficult.
©
The primary impact of these rules is to
increase the color rendering index
(CRI) of standard and high-output cool
and warm-white lamps. Table 2 summarizes the EPACT standards.
eASHRAE
90.1 and Title 24,
California Code of Regulations
Under the National Energy Policy Act of
1992, states are required to adopt
ASHRAE 90.1 1989 or else demonstrate
how an alternative is comparable. Title
24, Subchapter 4 contains mandatory
requirements for lighting systems and
equipment in nonresidential, high-rise
residential, and hotel/motel facilities.
The main provisions address controls,
requirements for lighting circuitry, and
minimum standards for luminaires.
PG&E Energy Efficiency Information “Full-Size Fluorescents”
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Definitions of Key Terms
input, expressed in lumens per watt.
signed to convert line current into the
proper voltage, amperage, and waveform to operate a fluorescent or highintensity discharge lamp.
• Electronic Ballast: Device using
solid-state components to provide current to a lamp at high frequency
(typically 25,000 to 60,000 cycles per
second), producing more light using
fewer watts than magnetic ballasts.
• Ballast Factor: The light output of a
• Fluorescent Lamp: A low-pressure
• Ballast: An electrical device de-
fluorescent lamp(s) operated on a ballast as a percentage of the light output
when
operated
on
a
standard
“reference” ballast. Ballasts with high
ballast factor put out more light from a
given lamp than ballasts with low ballast
factor.
• Color Rendering Index (of a light
source) (CRI): A measure of the degree
of color shift objects undergo when illuminated by the light source as compared with those same objects when illuminated by a reference source of
comparable color temperature. CRI
ranges from 0 to 100. Lamps with higher
CRI render colors more accurately than
lamps with low CRI. Incandescent lamps
have a CRI of 100, while fluorescent
lamp CRIs range from about 50 to
nearly 90.
• Color Temperature (of a light
source): The absolute temperature of a
blackbody radiator having a chromaticity
equal to that of the light source. Color
temperature is completely unrelated to
CRI, and is somewhat counterintuitive in
that lamps with lower color temperatures appear “warmer” or redder, while
lamps with higher color temperatures
appear “cooler” or more blue.
mercury electric-discharge lamp in
which a fluorescing coating (phosphor)
transforms the discharge energy of an
electric arc into light.
• Footcandle (fc): A unit of illuminance, equal to 1 lumen per square
foot2 or 10.76 lux
• High Output (HO): Ballasts and
lamps designed to operate with 800milliamp current to provide greater light
output.
• High-Intensity
Discharge (HID)
Lamp: An electric-discharge lamp in
which the light-producing arc is stabilized by wall temperature, and the arc
tube has a bulb wall loading in excess
of 3 W/cm 2 . HID lamps include groups
of lamps known as mercury, metal halide, and high-pressure sodium.
• Hybrid Ballast: A magnetic ballast
that shuts off heat to a lamp’s electrodes after the lamp has started.
• Instant Start: A lamp and ballast
system designed to start a lamp without
preheating electrode by providing a
high-voltage spark.
• Efficacy: The total light output of a
lamp divided by the total lamp power
©
PG&E Energy Efficiency Information “Full-Size Fluorescents”
Page 14
• Lumen (lm): The SI unit of light output. It is the light emitted through a unit
solid angle (1 steradian) by a point
source having a of 1 candela.
• Luminaire: Generic term for a complete lighting unit, consisting of lamp(s),
parts designed to distribute light from
the lamps, components to connect the
lamp to its power source, and an electrical device to provide that power.
• Magnetic Ballast: Typical fluorescent ballast consisting of a magnetic
coil and capacitor, designed to limit current and provide necessary starting
voltage for fluorescent lamps.
1616, e-mail [email protected],
web site www.cutter.com.)
4. Inter.Light electronic product and
supplier
database:
www.lightlink.com. Includes more than 1500
lighting companies with product
photos and catalog ordering functions.
5. Special Report on Lighting, “Energy
User News,” September 1996.
(Includes listings of manufacturers of
ballasts, reflectors, and lamps.)
Major Manufacturers
• Very High Output (VHO): Ballasts
GE Lighting
1975 Noble Road, #4295
Cleveland, OH 44112
Tel (216) 266-3947
Fax (216) 266-3381
and lamps designed to operate using
1,500 milliamp current in order to provide greater light output.
References to More
Information
Osram Sylvania Inc
100 Endicott Street
Danvers, MA 01923
Tel (508) 777-1900
Fax (508) 750-2089
1. E Source, “Lighting Technology Atlas,” Volume 1, 1994.
Advanced Transformer
10275 W. Higgins Rd.
Rosemont, IL 60018
Tel (847) 390-5000
Fax (847) 390-5109
2. Illuminating Society of North America, “Lighting Handbook: Reference
and Application,” 8th Edition, 1993.
3. Information Corporation, “1997 Energy Products Directory, The Sourcebook for Commercial Buildings,
3rd Edition,” 1997. (Contact Ira Kerchin, Editor, Technologies for Energy Management, Cutter Information Corporation, 37 Broadway, Suite
1, Arlington, MA 02174-5552, tel
(617) 641-5118 or (800) 964-5118,
fax (617) 648-8707 or (800) 888©
For more information on component
manufacturers and distributors, see
References 2, 3 and 5. Information on
this technology can also be found by
contacting relevant trade organizations,
such as the National Electrical Manufacturers’ Association and the Illuminating Engineering Society of North
America.
PG&E Energy Efficiency Information “Full-Size Fluorescents”
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