ient equipment over the past 10 years.
High-efficiency electronic ballasts represent over half of new ballast sales in the U.S., and that share will grow rapidly
because magnetic ballasts are effectively banned for many linear fluorescent lamps beginning in 2005
(see Electronic ballasts).
What Are the Options?
There are two basic categories of full-size fluorescent ballasts: electronic and magnetic.
Figure 1
shows both types.
Magnetic ballasts provide output power to the lamp at line frequency (60 cycles per second in North America and 50 cycles
per second in many other regions of the world).
Electronic ballasts use semiconductor technology to convert incoming 60-cycle power to drive the lamps with high-
frequency current of 20,000 cycles per second or more. Electronic ballasts are more efficient in a number of ways. Most
notably, they waste less power internally than magnetic ballasts, saving 3 to 8 watts per ballast. Because of their higher
frequency, they drive lamps about 10 percent more efficiently than 60-cycle magnetic ballasts do. And those electronic
ballasts with dimming capability save energy in multiple ways. For example, lumen compensation eliminates the need to
overlight spaces when lamps are new, and reducing electric light levels when daylight is available also results in savings.
Some well-publicized failures of certain early-generation electronic ballasts made users wary of the technologys reliability.
However, manufacturers have worked hard to dispel these concerns with a combination of improved design and higher-
quality control standards in
components and assembly. Today,
electronic ballasts from established
suppliers are just as reliable, if not
more so, than magnetic ballasts.
In September 2000, the U.S.
Department of Energy (DOE) issued
regulations that effectively banned the
use of new magnetic ballasts for the
most common types of T12 fluorescent
lamps. The regulations include ballasts
that are manufactured on or after April
1, 2005, sold on or after July 1, 2005,
or incorporated into a luminaire by a
luminaire manufacture on or after April
1, 2006. Although the rules do not
specifically ban magnetic ballasts, they
establish minimum ballast efficacy
factors (BEFs) that are hard to achieve
with a magnetic ballast. The rules do
not cover ballasts for T8 lamps,
because market forces are driving the
use of electronic ballasts for most T8
applications.
Figure 1: Whats in a ballast?
Electronic ballasts reduce energy use primarily because fluorescent lamps
operate more efficiently at frequencies above 20 kilohertz than when operated
at 50 or 60 hertz.
Notes: EMI = electromagnetic interference;
IC = integrated circuit; PF = power factor;
THD = total harmonic distortion;
Underwriters Laboratories
Integrated-circuit electronic ballast
Standard magnetic ballast
Gap for
optional
control
circuitry
Magnetic output
transformer
Magnetic
transformer for
voltage supply and
current limiting
(copper windings
around steel core)
Bimetal switch for
thermal protection
(UL Class P)
Register for
bleed-off
discharge of
capacitor
Capacitor
for PF correction
Capacitor
for lamp
starting
Integrated chip
for voltage
THD, starting,
PF correction
Power
conditioner
for IC chip
EMI filters
and rectifier
Copyright © 2005 - Platts, a Division of The McGraw-Hill Companies, Inc. All Rights Reserved Disposing of Old Ballasts
Magnetic ballasts produced through 1979 used polychlorinated biphenyls (PCBs) as an insulating
material. Some magnetic ballasts produced between 1979 and 1984 used diethylhexylphthalate
(DEHP). Because PCBs and DEHP have been associated with adverse health effects, ballasts
containing these compounds cannot be discarded in ordinary landfills in some jurisdictions. Millions of
ballasts containing these compounds are still operating in buildings today. Although one option for
avoiding disposal costs when upgrading lighting systems is to disconnect PCB- or DEHP-containing
ballasts and leave them in place with new ballasts, this is not a long-term solution. In the event of a
building fire, these compounds could be dispersed through the site, render the building uninhabitable
for many years, and lead to massive cleanup costs. The better approach is to develop a comprehen-
sive recycling/disposal strategy for old ballasts in conjunction with a lighting system upgrade. See
Environmental, Health and Safety Online
for more information on magnetic ballast disposal.
Ballast factor. Ballasts can underdrive or overdrive a given lamp to produce lower or higher light output.
Ballast factor (BF) is the ratio of a lamp_s light output with a given ballast to the same lamps light
output when operated with a standard reference ballast in open air at 25° Celsius (C), using procedures
specified by the American National Standards Institute (ANSI). The ballast factor is between 0.86 and
0.92 for most ballasts with "normal" BFs. "Low"-BF ballasts have ballast factors as low as 0.68, and
"high"-BF ones are available with ballast factors up to 1.41. Lighting designers often use specific BF
equipment to fine-tune lighting systems and maximize the versatility of each lamp type.
How to Make the Best Choice
Ballasts are often the most expensive first-cost component of a lighting retrofit. Fluorescent lamp
ballasts typically cost between $5 and $50. However, ballasts for high-power lamps, such as T12/VHO
(very high output) lamps and some dimming electronic ballasts, can cost considerably more. There are
generally substantial discounts for the purchase of the large number of ballasts needed for new
construction or renovation. Ballasts last for 40,000 to 100,000 hours and operate with an electrical
efficiency of about 80 to 95 percent, consuming parasitic power of about one to a dozen watts.
Following are the best choices for ballasts:
Electronic (high-frequency) ballasts. Electronic ballasts are about 10 percent more efficient than
conventional line-frequency magnetic ballasts. They eliminate flicker and hum and are extremely cost-
effective. The most efficient ballasts are defined in terms of BEF (
Table 1
, page 3). There are a few
locations where it is still best to use magnetic ballasts: in recording studios, near radio-frequency
security systems (such as those in bookstores), and in other extremely sensitive electronic environments
that may be disturbed by high-frequency emanations from electronic ballasts. Although the U.S.
Department of Energy (DOE) ballast rule effectively eliminates most magnetic ballasts used with T12
lamps, magnetic ballasts should still be available for T8 lamps in these niche markets.
Purchasing Advisor
Lighting:
Fluorescent Ballasts
Copyright © 2005 - Platts, a Division of The McGraw-Hill Companies, Inc. All Rights Reserved Instant-start ballasts. This is the
most efficient type of ballast, but it
yields the shortest lamp life in most
applications. It is a good choice for
lamps that burn six hours or more
per start.
Programmed-start or programmed
rapid-start ballasts. Programmed-
start ballasts, also known as
programmed rapid-start ballasts, are
improved versions on the older
rapid-start technology that
maximizes lamp life in almost all
casesalthough there is some
penalty in efficiency. They are the
best choice in applications where
lights will frequently be turned on
and off.
Universal-input ballasts. These
ballasts typically accept any input
voltage between 120 and 277 volts.
They make retrofitting easier and
reduce stocking requirements, but
they are slightly less efficient than
dedicated-voltage ballasts.
Dimming ballasts where appropriate. Fully dimmable fluorescent ballasts enable strategies such as automatic daylight
dimming, lumen maintenance (automatically adjusting ballast power to compensate for the gradual loss of light output
that all fluorescent lamps experience), occupancy-controlled and -scheduled dimming, and manual task dimming
(whereby the occupant uses a rotary or sliding dimmer switch or PC control). Several dozen models of continuously
dimming ballasts for full-size fluorescent lamps are now available in the U.S. market, and prices are dropping into the
low-$30 range for two-lamp dimming ballasts.
Finally, check with manufacturers to make sure that lamps and ballasts are compatible. Most lamps are only compatible
with one starting method; the exceptions are high-performance T8s, which can be rapid- or instant-started, and some
rapid-start lamps that can be preheat-started.
Whats on the Horizon?
Wireless technology is playing an expanding role in a range of applicationsincluding cell phones, computer
peripherals, and Internet connectionsand wireless lighting controls are not far behind. Wireless controls for limited
niches such as conference rooms and classrooms have been available for a number of years, but they are expensive
and are sold based on the amenities that they provide. Newer systems that are more widely applicable and provide
energy savings and load-shedding capabilities are in the works. Look for the first major products to appear in 2006.
Copyright © 2005 - Platts, a Division of The McGraw-Hill Companies, Inc. All Rights Reserved
Table 1: High-performance T8 ballasts
According to the definition from the Consortium for Energy Efficiency, high-
performance T8 ballasts must have a ballast efficacy factor (BEF) at least as
high as the ones shown here.
Notes: BEF= 100 x (ballast factor/ballast input
power in watts); BF= ballast factor;
NA = not applicable.
a. BF
0.85
b. 0.85<BF
1.0
c. BF
1.01
Source: Platts; data from Consortiu