Besides energy and maintenance cost
savings, LED technology offers instant-on
operation (compatibility with occupancy
sensors), improved lumen maintenance,
universal operating position, good color
quality, very little radiated heat and other
advantages relative to HID.
LED retrofit lamps feature a base
that screws into existing HID sockets.
Generally, they are available in 30–400
watts (W) for replacement of 50–1,000W
HID lamps. A popular example is replacing 400W metal halide lamps with
150–200W LED lamps. LEDs feature
correlated color temperatures of 2,000–
5,000K and color rendering typically in
the low 80s. The majority carry an L70
service life of 50,000 hours, backed by a
5–10 year warranty. Depending on operating hours and local energy costs, short
payback periods are possible.
As with tubular LED lamps, the
lamp may operate with or bypass the
existing ballast, offering options with
differing advantages. Ballast-driven
or plug-and-play lamps screw into the
existing socket. They operate on the
existing ballast, so it’s important to
verify the lamp is compatible with the
ballast technology. Light output generally ranges from around 2,000 to 20,000
lumens. While typically the quickest and
lowest-cost option, operating the lamp
on the existing ballasts adds 40–60W to
the load, while the ballast itself presents
a point of failure for the system.
Line-driven lamps operate on line
voltage, eliminating the ballast and its
load. Light output generally ranges from
around 1,500 to 15,000 lumens. Some of
these products qualify for DesignLights
Consortium (DLC) listing. Many utility
rebate programs use the DLC’s Qualified
Products List to qualify eligible products.
While saving more energy, this option
typically imposes a higher installed cost
because of the electrical labor required to
bring line voltage to the sockets.
A third option is a retrofit kit, which
packages the lamp with such components
as secondary optics to provide a repeatable solution that is effectively a new
luminaire. Often, an external LED driver
replaces the ballast. The retrofit permanently switches the luminaire from HID
to LED. Many of these products are DLC-listed. Retrofit kits typically package with
standard drivers that feature 0–10V leads
that optionally connect to lighting control systems, creating opportunities to
accelerate energy cost savings by implementing control strategies.
A lighting retrofit’s primary purpose
is to save energy while maintaining or
improving lighting quality. While offering
viable retrofit options, LED replacement
lamps and retrofit kits require careful selection and application to achieve
Light output and distribution
Overall, light levels and quality should
satisfy owner expectations based on
need. The majority of LED replacement
lamps use a corncob design that generally
mimics an HID lamp’s emission. In addition, directional PAR lamps and retrofit
kits often feature a flat chip-on-board
design. Well-designed products should
not compromise light distribution.
Light output should be compared
based on the application’s required light
levels and the competing technologies’
depreciation, luminaire optical
efficiency and so on. If the lamp is directional, it is often desirable to consider
center-beam candlepower as part of
HID luminaires are often installed in
rugged applications with extreme environmental conditions. The selected lamp
should be suitable for the application
and not compromise the specific job for
which the HID luminaire was selected.
Ideal applications are damp or dry
spaces that are not subject to extreme
temperatures or heavy particulates. If
needed, ask the manufacturer to provide
testing data or other evidence of performance claims.
A related factor is the existing sockets’ condition. If it isn’t good, it may need
to be replaced. In addition, determine
whether the existing socket is medium
or mogul; LED replacement lamps tend
to be heavier than HID lamps and require
a socket that can handle their weight.
The majority of LED replacement lamps
are not controllable. LED retrofit kits
typically package with dimmable drivers that can connect to control systems,
leading to additional energy cost savings, increased flexibility and potentially
extended lamp life.
With up to 50 percent energy cost
savings and potential maintenance
savings, LED replacement lamps
and retrofit kits offer an increasingly
viable retrofit option for HID luminaires. However, products must be
carefully matched to applications to
ensure desired performance and lighting quality. As with any retrofit, a trial
installation is often recommended prior
to major commitment.
HID to LED
HIGH-INTENSITY DISCHARGE (HID) LAMPS, notably metal halide and high-pressure sodium, are widely installed in industrial, retail, and other applications.
In recent years, the LED revolution has produced retrofit options promising up to
50 percent energy savings and long service life. Utilities now increasingly support
these options with nearly 120 rebate programs offering an average $110 per LED
retrofit lamp, according to BriteSwitch.
DILOUIE, L.C., is a journalist and educator specializing in the lighting industry. Learn
more at ZINGinc.com and LightNOWblog.com. S H