LEDsmagazine.com JULY/AUGUST 2017 29
indoor lighting | LED TUBES
In existing buildings with older fluores- cent lamps and fixtures, lighting retro- fits can deliver significant energy savings,
improve light quality, and reduce maintenance costs. An increasingly popular solution is to retrofit fluorescent fixtures with
tubular light-emitting diode (TLED) retrofit
options (also known as LED tubes).
TLEDs can be easy to install, offer longer life, and reduce energy usage compared
to fluorescent lighting as noted in a US
Department of Energy (DOE) Caliper Snapshot report on linear LED lamps (http://bit.
ly/2sDMi9B; see the news story at http://bit.
ly/2eUS409). But there are tradeoffs, especially when a dimming control system is
already in place, and high-performance dimming functionality is desired.
Before deciding on a TLED retrofit, consider the type of lighting performance necessary in the space. If the lighting needs to
be fine-tuned and/or dimmed to low levels,
TLEDs may not be able to deliver these benefits. Here we will consider three common-ly-used TLED retrofit scenarios.
TLEDs retrofitted with existing
fluorescent ballasts (UL Type A)
In the first scenario, the fluorescent lamps
are replaced with specialized LED lamps
that work with the existing ballasts. This
type of TLED lamp has sophisticated internal electronics that simulate the electrical
characteristics of a fluorescent lamp, essentially tricking the ballast into thinking a fluorescent lamp is still connected (Fig. 1).
A significant benefit of this option is
that installing TLEDs into existing fixtures
requires minimal labor and no modification
to existing wiring or sockets. It is a very sim-
ple solution but not without risks. The addi-
tional circuitry typically adds cost to the LED
lamp and decreases its efficiency compared to
an LED lamp used in conjunction with an LED
driver. Compatibility issues can also make this
seemingly simple solution complicated, and
may result in poor dimming performance.
TLEDs wired directly to line
voltage (UL Type B)
The second scenario has one component — a
lamp with an integrated line-voltage driver —
and requires very little rewiring (Fig. 2). The
installer need only remove the ballast and
directly connect line voltage to the existing
sockets, then plug the TLED into the sockets.
But, in the future, an installer may be
unaware that the wiring was changed and
may plug a fluorescent bulb into the socket —
in which case, the line voltage will overload
the lamp and may pose a safety issue. Installers who choose to implement Scenario 2 are
required by code to educate future users by
installing an informational sticker that clearly
indicates fixture wiring is non-standard.
This scenario also increases labor costs,
as changes must be made to the line-voltage wiring, and existing sockets may need
to be replaced.
TLEDs supplied with dedicated
LED drivers (UL Type C)
The third option involves a TLED retrofit kit
consisting of LED drivers, LED lamps, and
labels that have been tested to meet the requirements of UL 1598C. The installer removes the
existing fluorescent lamps and ballast, then
wires in the new LED driver (Fig. 3).
The third scenario is a certified, reliable
solution where all the supplied components
have already been tested together as a system. The lamp remains low voltage, eliminating the risks associated with line-voltage
sockets. It is also possible to add dimming
capability by using a dimmable LED driver
and a compatible control system.
The risk in using the retrofit kit is that if
existing control wires are not already run
to the fixture (such as Lutron EcoSystem or
0–10V wires), adding a dimmable LED driver
may be more complicated than a non-dim-mable driver.
Scenario 3 is labor intensive but offers predictable, warrantied performance, and the
driver/control compatibility can be confirmed in advance.
Consider TLED tradeoffs and
If the application will benefit from high-performance LED dimming, the best practice
Tackle TLED tradeoffs to manage
Tubular LED upgrades of fluorescent fixtures offer efficacy, energy consumption, and lifetime
advantages over traditional fluorescent lighting, but it is essential to consider the options and
tradeoffs when dimming and controls are involved, says ETHAN BIERY.
E THAN BIERY is LED engineer leader at
Lutron Electronics ( lutron.com).
FIG. 1. A UL Type A TLED works with an existing ballast as a replacement for a
fluorescent lamp by using internal electronics to “trick” the ballast into behaving as
though a fluorescent tube is still connected.