Tubes in Troffers:
Technology Options in
Commercial Recessed Lighting
Presented by: Ramin Faramarzi, PE | Prepared by: Grant Davis
Technology Test Centers | Southern California Edison
EEI National Key Accounts Workshop
Caesars Palace, Las Vegas, NV
October 6–9, 2013
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What are we talking about?
1. Fluorescent Troffers
2. LED Tubes in a Fluorescent Troffer
3. LED Troffers
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What’s the difference?
Can one replace another?
What do I need to be aware of?
Why can’t I get a rebate for LED tubes?!?!
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Agenda
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Technology Test Centers
Lighting Technology
Fluorescent Troffers
LED Tubes in a Fluorescent Troffer
LED Troffers
Key Takeaways
More Information
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Integrated Demand Side Management (IDSM) Laboratories
TECHNOLOGY TEST CENTERS
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Controlled Environment
Laboratories
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Controlled Environment Laboratories (Cont.)
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Photometric Laboratories
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Linear Fluorescent and LED
LIGHTING TECHNOLOGY
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Fluorescent Lamp Technology
• Operation
– Arc between cathodes stimulates mercury vapor atoms
– Mercury vapor atoms give off ultraviolet (UV)
photons
– UV stimulates phosphor coating,
causing it to emit
phosphors
visible light
mercury vapor
cathode
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Linear Fluorescent Lamps
• Many sizes and wattages
– Most common
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Straight and U-bent
2’ and 4’ lengths
F32T8: Fluorescent, 32 watt, Tube, 8/8” diameter tube
F28T5: Fluorescent, 28 watt, Tube, 5/8” diameter tube
• Different color temperature and color rendering options
• Bare lamp efficacy ranges from 60–100 lm/W
• 24k–46k hour life
– Depends on lamp, ballast, and hours per start
• “Area Source”
– Large, diffuse luminous area (ex.: 4’ long, 1” diameter!)
– Light comes out in all directions along axis of lamp (360 °)
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Linear Fluorescent Ballasts
• Required to operate a fluorescent lamp
– Provides high starting voltage to strike arc
– Limits current
– Enables dimming and control
• Technology improvements
– Magnetic  Electronic (more efficient)
– Instant Start  Program Rapid Start (longer lamp life)
– Fixed output  Step Dimming  Continuous
Dimming (controllability/energy savings)
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Linear Fluorescent Luminaires
• Hold and protect lamps
• Photometry
– Efficiently direct light where it’s needed
– Control unwanted glare
• Aesthetics/architectural design
• Provide electrical and control interfaces
• Limited thermal management
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The Linear Fluorescent System
• Fluorescent Lamp(s)
+ Fluorescent Ballast
+ Fluorescent Luminaire
= Fluorescent System
The lighting designer or end user
can mix and match compatible
lamps, ballasts, and luminaires,
depending on the desired cost,
performance, and design.
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Linear Fluorescent Summary
Advantages
• High efficacy
– 60–100 lm/W (bare lamp)
• Excellent color
– 80+ CRI common
• Dimmable
– With dimming ballast
• Long life
Disadvantages
• Temperature sensitive
– Not too hot, not too cold
• Dimming expensive
– Ballasts + Control System
• Disposal issues
– Lamps contain mercury
– 24k–46k hours
• Inexpensive lamps
– $2–$4 per lamp
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LED Technology
• A semiconductor device that only lets current
flow in one direction (direct current, DC)
• Light emitting diodes (LEDs) emit photons of
light when current flows through
(electroluminescence)
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LED Chips
• Also known as devices/packages
– Multiple chips/devices/packages can be arranged in an
array/module to increase overall light levels
• Many different form factors and performance
options
• Tightly integrated and engineered with thermal
management, driver, and optical components
• Not specified or serviced by end user
• Typical performance range
– 100+ lm/W (bare package), 80+ CRI, 50k–100k hours
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LED Drivers
• Required to operate an LED module/array
– Converts high voltage AC to low voltage DC
– Similar in purpose to a fluorescent ballast
• Regulates voltage and current
• Enables dimming and control
• Can be a discrete component in larger
luminaires (ex., street lights)
– Typically, tightly integrated into luminaire design,
and is not user serviceable
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LED Optics
• LEDs are directional, point sources
– Light comes out in a narrow direction
– Light comes from a small, concentrated area (point)
• Sophisticated optics are required to
– Extract as much light from the chip as possible
– Bend and direct it in the desired directions
– Each layer of optics, lenses, and diffusers decreases
efficiency, so it’s tough to match the diffused light
from a fluorescent lamp in an interior application
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LED Thermal Management
• Thermal management is critical
• Higher temperatures result in
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Decreased light
Decreased life
Decreased efficacy
Decreased color quality
Color shifts
• Well designed LED systems have engineered
thermal management (typically heat sinks)
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The LED System
• LED chip/device/package
Each component is tightly
integrated and engineered with
+ Driver
the others, unlike traditional
lighting technologies where you
+ Optics
can mix and match lamps,
+ Thermal Management
ballasts, and luminaires. The enduser buys a complete system.
= LED System
• The system is only as strong as its weakest link!
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LED Summary
Advantages
• High efficacy
– 100+ lm/W (bare package)
• Excellent color
– 80+ CRI common
• Dimmable
– With dimming driver
(common)
• Long life
– 50k–100k hours
• Recyclable
Disadvantages
• Temperature sensitive
– Thermal management critical
• Emerging technology
– Performance uncertainties (life,
dimming, color)
– Application considerations
• High initial cost
• Overall experience is highly
application dependent
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The Baseline
FLUORESCENT TROFFERS
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Troffers
• Found everywhere; lighting workhorses
• Most common type of recessed lighting
• Typically 2’x4’, 2’x2’, or 1’x4’
– Designed for acoustical T-bar ceiling grids
– Hard/surface mount options also available
• Many lens/optical and aesthetic options
– Lenses, louvers, baskets, colors
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Fluorescent Troffers
• Specify/add lamp(s) and ballast to form a
complete fluorescent system
• 2’ or 4’ T8 or T5 lamps are most common
• Electronic dimming ballasts will become
common in CA (due to T24 2013)
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Fluorescent Troffer Characteristics
• Basically, a simple sheet metal box that holds the
ballast and lamps, except…
• The optics are very sophisticated
– Take full advantage of fluorescent lamp
characteristics; uses 360 degrees of light coming from
lamp, and controls/directs it to create a uniformly lit
space with minimal glare
– Not much diffusion is needed, since fluorescent lamps
are already diffuse area sources
• Fluorescent troffers are built around
fluorescent lamp technology
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Option A
LED TUBES IN A
FLUORESCENT TROFFER
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LED Tubes
• LEDs arranged in a
fluorescent tube form factor
• Typically lower wattage
than the lamps they’re replacing
• Idea: Open an existing fluorescent troffer, and
replace the fluorescent lamps with LED tubes
• Sounds good, right?
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Application Considerations
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Photometry
Thermal management
Ease of retrofit
Safety
Age/condition of existing luminaire
Controllability
Savings
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Photometry
• LEDs are directional point sources
– Light comes out in one direction, in a narrow beam angle, and in very
concentrated “hot spots”
– Typically, LED tubes only provide down light, compared to
fluorescent, which provides light in 360 degrees along lamp axis
– Existing luminaire is designed for fluorescent tube photometry;
installing LED tubes prevents the luminaire from doing its job
• Typically, LED tubes will significantly change the lighting
uniformity of the space
– Can increase illuminance directly beneath luminaire, but illuminance
will decrease to the sides (common trick by LED tube salespeople)
– The only way to address uniformity is to relocate luminaires, which
incurs significant design and construction costs, and defeats the
purpose of the retrofit
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Thermal Management
• LEDs need engineered thermal management
– Fluorescent tube form factors (glass/plastic enclosures) don’t
provide a path for heat to exit the tube
– The two pins at each end of the tube are for carrying electricity;
not a significant heat sink
– Some LED tubes have a heat sink built into the top half of the
tube, but this ensures the tube only has down light, which still
means poor photometry; also, heat still builds up inside
luminaire cavity with no place to go
• LEDs built into a fluorescent tube form factor will either:
– Have a shorter life due to poor thermal management, or
– Have lower efficacy and light output due to intentionally reduced
operating power in order to reduce operating temperature
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Ease of Retrofit
• Most LED tubes require an external driver that is installed in place
of the fluorescent ballast
– Requires gutting the fluorescent troffer to remove/bypass the existing
ballast and most of the existing wiring, and install the LED driver and
rewire
– This requires significant labor by an electrician
• Some LED tubes can take 120 V directly
– Still requires gutting the fluorescent troffer to remove/bypass the
existing ballast and most of the existing wiring, and rewire
• Very few LED tubes can run directly from a fluorescent ballast
– A true “lamp only replacement”
– But, ballast compatibility and performance are severely limited
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Safety
• What happens to the luminaire system once it’s
retrofitted with LED tubes?
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Loose wires/lamp connections?
Quality of work by electrician?
Short circuits/fire hazard?
Validity of UL rating?
• What happens when an LED tube “burns out”
– …and a facility manager comes along and tries to
install a regular fluorescent lamp?
– Instant burnout!
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Age/Condition of Existing
Luminaire
• Most fluorescent troffers that are candidates for retrofit
are old, worn out, and inefficient
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Seen several re-lampings and ballast replacements
Dirt/fingerprints on optical surfaces
Yellowed/cracked/bent lenses
Out-of-date/less efficient optical designs
Sagging/bent/misaligned enclosures
• Do you typically put a new engine in an old, worn out
car? (No, typically you buy a newer car!)
– Should you put a new light engine in an old, worn out
luminaire? (No, typically you buy a newer one!)
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Controllability
• Some LED tubes are dimmable
– This is a function of the driver
• Most LED tubes are not dimmable
– Limited to on/off control
– Won’t help meet 2013 T24
• In either case, any existing fluorescent control
system likely won’t be compatible, since
existing fluorescent ballasts are removed
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LED Tube Savings (oxymoron)
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Some LED tubes have similar efficacy to fluorescent lamps
Many LED tubes have lower lumen output than fluorescent lamps
Most LED tubes have lower demand than fluorescent lamps
So, if you replaced your fluorescent lamps one-for-one
– You’d have significant energy savings, but at the cost of a roughly
equivalent drop in illuminance levels, so you’re not saving anything
• And, if you installed enough LED tubes to match the fluorescent
illuminance levels
– You’d have roughly no energy savings, but at the cost of a adding
additional luminaires, so you’re not saving anything
• And we’re still not considering photometry, thermal management,
ease of retrofit, safety, condition of existing luminaire, or
controllability, all of which make the picture even uglier!
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Option B
LED TROFFERS
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LED Troffers
• Same form factor as a fluorescent troffer
– Intended to install, look, and smell like a
fluorescent troffer
• But inside…
– An engineered LED system
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LED Troffer Characteristics
• Not a simple sheet metal box
– An integrated system with LED chips, driver, optics, and
thermal management
– A complete, “sealed” unit; typically not serviceable
• Try to deliver all the advantages of both LED
technology and fluorescent troffers
– Without the disadvantages of using LED tubes in a
fluorescent troffer
• Even though an LED troffer looks and performs like
a fluorescent troffer, the entire luminaire is built
from the ground up around LED technology
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SCE Lab Project Example:
LED Recessed Luminaire
• Evaluated approximately
15 LED products from 8
major manufacturers
• Compared to 12
fluorescent products with
various lamp and optical
configurations
• Many of the LED
troffers performed well,
but the cost still needs to
come down
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Important Note:
LED Tubes v. LED Troffers
• LED tubes in a fluorescent troffer is not the
same as an LED troffer
LED tubes
Fluorescent Troffer
+
LED Troffer
?
≠
=
NO!
• LED troffers are typically a better choice
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The Baseline, Option A, or Option B?
KEY TAKEAWAYS
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The Baseline:
Fluorescent Troffers
• Area source lamps (large luminous surface area)
– Provide uniform, diffused light
– Great for interior applications, where distance between
lamp and work plane is small
• Efficacious
– Similar to LEDs on a system level
• Luminaires and lamps are relatively cheap
• Here to stay for a while
– In existing applications
– Until cost of LED troffers comes down
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Option A:
LED Tubes in a Fluorescent Troffer
• Point sources (LEDs) packed in an area source form
factor (fluorescent tube)
– Requires more optics and diffusion to distribute light
– Tough to provide fluorescent-quality photometry
• May be efficacious
– In exchange for poor photometry and lower overall light
levels
• Other concerns
– Safety, ease of installation, condition of existing luminaire,
controllability, thermal management, savings
• Expect performance differences from fluorescent
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Option B:
LED Troffers
• An integrated, engineered LED system
– The LEDs and troffer were meant for one another
• Other benefits and features (varies)
– Long life, dimming, good photometry, good color,
energy savings (maybe), cost savings (maybe)
• Can be pricey
• Expect prices to drop and performance to
improve over time, gradually replacing
fluorescent troffers
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Fluorescent Troffers v. LED Troffers
Fluorescent troffers
• Built around fluorescent
lamp technology
– Workhorses
• Typically don’t make for
good LED tube retrofits
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Optics/photometry
Age/condition
Safety/ease of retrofit
Controllability
Thermal management
LED troffers
• Built around LED source
technology
• Able to provide good
photometry, controllability,
and long-term performance
If switching to LED technology, it’s much
better to replace an entire fluorescent
troffer with an integrated LED troffer
(a complete luminaire system),
rather than retrofit an existing fluorescent troffer with LED tubes
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Summary
Fluorescent troffer
• With fluorescent lamps
– A modern fluorescent troffer
with T8 or T5 lamps,
electronic ballast, and high
efficiency optics
– Still a great choice
• Retrofitted with LED tubes
– A new/old fluorescent troffer
retrofitted with LED tubes
– Proceed with caution
LED troffer
• A modern LED troffer with
integrated LED light engine
(a complete luminaire
system)
• Can be a great choice
– But make sure you do your
research
• Life cycle cost ↔ Initial cost
• Photometry ↔ Application
• Warranty ↔ Lifetime
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Questions
• Ramin Faramarzi, P.E.
– Manager, Technology Test Centers
– Southern California Edison
– ramin.faramarzi@sce.com
– (626) 633-7168
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Appendix
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Tubes in Troffers: Abstract
Commercial interiors have been dominated by T-bar ceilings
filled with the familiar 2'x4' or 2'x2' recessed "troffer" for
decades. This basic luminaire design has survived several
generations of lighting technology, including T12, T8, and T5
lamps, magnetic and electronic ballasts, and A-B switching all
the way through modern digital controls. Now, a new
generation of recessed LED luminaires and lamp replacements
are entering the market with promises of high quality light,
greater control, less maintenance, and lower operating costs.
Are they a no brainer? Find out why linear fluorescent lamps
won't go quietly, and what to consider before retrofitting your
troffers with LEDs.
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TTC’s Approach to Integrated
Demand Side Management
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Lighting Terminology
• Luminous flux (lumens, lm) – amount of visible (usable) light provided by
a source in all directions
• Illuminance (footcandles, fc) – amount of light falling on a point (ex.,
amount of light from entire room to light up point on desk)
• Photometry (polar plot, .IES file) – angular distribution of light due to
design of luminaire optics
• Correlated color temperature (CCT, °K) – color appearance of the light
itself (ex., “cool white,” “warm white,” cool office fluorescents compared
to warm home incandescents)
• Color rendering index (CRI, Ra, 0–100) – how accurately colors appear
under the light (ex., fresh fruit under fluorescent v. incandescent lighting)
• Power (watts, W) – electrical demand
• Luminous efficacy (lumens per watt, lm/W) – efficiency of luminaire
system (luminaire efficacy) or light source (bare lamp efficacy)
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Past TTC Lighting Projects
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Channel Letter Lighting
Linear Signage
OPEN Signs
Refrigerated Cases
Under-Cabinet Lights
Down lights
Troffers
Backlit Menu Boards
Dimming Ballasts
• Fluorescent Tube
Replacements
• Screw-in PAR Lamps
• MR16 Lamps
• Pathway Lights
• Street and Area Lights
• L-prize Lamp
• Screw-in A-lamps
• Plasma Luminaires
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DOE Lab Testing Example:
Fluorescent Lamps v. LED Tubes
SSL = solid state lighting (LED lighting)
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Resources
• SCE Energy Education Centers
– Introduction to Lighting – class about lighting technologies
– Beyond Efficient Lamps – class about luminaires
(specification, photometry, and application)
– Basics of LED Technology – class about LED light sources
(system components, advancements, and applications)
• SCE Account Manager
– Rebates, energy audits, design assistance
• US Department of Energy Solid State Lighting Program
– http://ssl.energy.gov
– http://lightingfacts.com
– Better Buildings Alliance, LED Troffer specification
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