This document discusses solid state lighting (SSL) and LED lighting as alternatives to traditional lighting sources. It provides the following key points:
1. CRI (Color Rendering Index) is an outdated measure that does not accurately evaluate how well modern light sources render color. CQS (Color Quality Scale) is being developed by NIST to replace CRI. LEDs score well on CQS but can sacrifice efficiency to score high on CRI.
2. SSL fixtures provide consistent light output because the entire unit is designed together, unlike lamps that experience light loss when installed due to fixture design. SSL has a lifespan of 100,000 hours with minimal lumen depreciation over time.
3. Traditional
2. Problems with CIE’s CRI
CQS Color Quality Scale
“ Color rendering: Effect of an illuminant on the color appearance of
objects by conscious or subconscious comparison with their color
appearance under a reference illuminant „ —CIE 17.4, )
International Lighting Vocabulary, (Schanda 2002)
CQS is being developed by NIST (National Institute of Science) to replace
the outdated CRI measurements
The human eye works optimally when objects are illuminated with
noonday sunlight (6500K). The white light from the sun includes all
the light spectra from Blue to Red in equal proportions. We see the
spectra an object reflects and does not absorb. If a light source does
not have the full spectrum of the sun then objects do not appear
their natural color.
CQS will replace CRI. Some of the CRI procedures will be retained but the
test will test for a light to saturate the colors at the end of the
spectrums. Light that score well on the CRI test will suffer under the
CQS test.
SSL technology using High Brightness white LEDs score very high on CQS
and low on CRI. LEDs can be made to score well under the CRI test
but must sacrifice at least 20% of the efficiency to do so, and then
would no longer render color as well.
Is it reasonable to use CRI as a measure of a SSL? Inteltech will provide
whatever the customer wishes, but if efficiency and good color
rendering is desirable then CQS is the preferred standard.
• Outdated and inaccurate for modern
light sources
•Only applies to lights below 5000K
• Does not measure a light source’s
ability to render color faithfully.
• Does not work with modern LED
technology because it penalizes lights
that can fully saturate colors especially
those that contain blue and green.
• A score of 100 can be achieved with
light sources which can illuminate the
8 low saturated colors used in the test,
but fail to render bright colors
accurately.
• For instance, an incandescent lamp
will score 100, but the light makes an
object appear dull.
• Manufacturers like GE and Sylvania in
an attempt to offer full color rendering
to their incandescent lamps are
adding rare-earth phosphors to add
blue and green/yellow spectra.
3. Benefits of SSL Lighting
Lamp/Bulbs vs Luminaires
What do you get when you add four oranges to four apples? If you
multiply four cows times four cows, do you get 16 squares cows?
Math can be tricky, so can lighting system comparisons.
A designer must be careful when comparing different lighting
technologies for a project. A common error is to compare a
lamp/bulb to a luminaire. A luminaire, by definition, is the
combination of a ballast, enclosure, light source, and lens. A
luminaire has both an optical efficiency and a power efficiency. Both
efficiencies must be considered when selecting a luminaire. A
lamp/bulb is placed in an enclosure and usually filtered with a lens.
It is correct to compare one luminaire lumen output to another
luminaire lumen output.
For example, a 200 watt incandescent lamp may put out 3200 total
lumens, but when placed in a can light fixture 50% of the lumens are
lost to internal reflection and focusing. So the usable light output is
only 1600 lumens.
A SSL fixture is a complete unit: ballast, enclosure, and lens are integral
to the design. The lumen level specified is the lumen level you will
get.
A CFL (Compact Fluorescent) may put out 70 Lm/watt bare bulb, but
when placed in a can light only 35 Lm/watt is usable. The fixture
also builds up heat and shortens the bulb life appreciably.
A bare 4’ T8 or T5 lamp may put out 100 Lm/watt as specified on a data
sheet. But the lamp is part of a lighting fixture which includes the
ballast, the enclosure, and the front cover. Now the lumen output is
reduced over 60% in some fixtures. What happens when the high
voltages attract dust which coats the lens and lamps? The efficiency
suffers even more.
When designing a lighting system make sure the comparisons are done
luminaire to luminaire to get an accurate analysis.
• High Efficacy Luminaires
• 46 Lumens/watt (5000K)
• 38 Lumens/watt (4000K)
•100,000 hour life (DC version)
• Uniform light output
•Uniform color output
• Full dimming with 0-10V Control
• Low voltage DC operation
• High Voltage AC operation (coming)
• Four light color temperatures
• 5000K (most efficient)
• 4000K
• 3400K
• 2900K (least efficient)
• Compact, flush mount design
• Rugged, impact resistant, immune to
moisture
• Uses inexpensive plastic ceiling box
for installation (no cans)
• UL Approved for Class 1 and Class 2
wiring methods
4. Luminaire Life Expectancy
• Incandescents are being banned!
The incandescent lamp is being banned from retail sales beginning in
2012 in the USA and Canada. Toshiba of Japan is stopping
production in 2010. Certain higher efficiency units will be sold for a
while but eventually the goal is to eliminate this technology from
the face of the earth. Installing incandescents in a new building will
result in substantial replacement cost within just a few years.
Incandescent lamps have changed very little from Edison’s first creation.
Edison founded GE after he invented the light bulb. GE is now selling
it’s lighting division because the lighting technology is ancient.
There are an estimated 4 billion Edison sockets in the USA alone, it
is staggering worldwide. Some improvements have occurred over
the hundred years since then: for instance, the lamps use an inert
gas to keep the filament from burning up instead a vacuum, also
halogen has been added to help filament particles recombine on the
filament to extend the life. Rare-earth phosphors are added to
brighten the light so it will render color more accurately (see CRI
discussion).
The first lamps were 2% efficient in creating light, 98% was heat. They are
now approaching 20% efficiencies. Average Lm/watt for all
incandescent lamps is about 10 Lm/watt according to the DOE.
Some can reach 22 Lm/watt but have limited 1000 -2000 hour
lifetimes.
The very nature of the filament structure makes them vulnerable to
shock. The pressurized versions are dangerous. They run extremely
hot and create heat loads on the air conditioning systems, and when
improperly vented literally kill themselves.
The incandescent also suffers from rapid lumen loss. This complicates a
lighting system design. The designer must over-design the lumen
output because the actual performance will be 20% less over the life
of the bulb.
Since non-SSL lamps/bulbs are part of a
luminaire, how do we measure the life
you get from the system of parts? Add in
the fact that most of the fixtures are
made in China these days, the quality is
very poor. The ballast can fail, the socket
wears out, the connections corrode. How
many fluorescent fixtures are replaced
due to broken connectors? How often will
you replace a ballast? How often will the
front lens need replacement due to
discoloration and yellowing?
Silescent lights are milled from 6061
recycled aluminum and can be recycled
over and over again. Silescent lights are
designed and made in America, by
Americans. The milled aluminum is hard
anodized to make it impervious to
corrosion. The fixtures are then powder
coated to create a durable, lasting finish
of any color. They can literally vanish into
the ceiling. The lifetime specification is
the entire fixture not just the lamp.
5. Is the CFL the final
solution?
The mercury question?
• How may people and businesses really bother following the suggestions
offered by the D.O.E.? Most end up I the trash. Count the number of
ither items that must used to clean up the mean and be disposed of
along with the CFL. The DOE is desperate or they would not recommend
this lamp.
1. Before Clean-up: Air Out the Room
• Have people and pets leave the room, and don't let anyone walk through the breakage area on
their way out. Open a window and leave the room for 15 minutes or more. Shut off the central
forced-air heating/air conditioning system, if you have one.
2. Clean-Up Steps for Hard Surfaces
• Carefully scoop up glass fragments and powder using stiff paper or cardboard and place them in
a glass jar with a metal lid (such as a canning jar) or in a sealed plastic bag. Use sticky tape, such as
duct tape, to pick up any remaining small glass pieces and powder. Wipe the area clean with damp
paper towels or disposable wet wipes. Place towels in the glass jar or plastic bag. Do not use a
vacuum or broom to clean up the broken bulb on hard surfaces.
3. Clean-up Steps for Carpeting or Rug:
• Carefully pick up glass fragments and place them in a glass jar with metal lid (such as a canning
jar) or in a sealed plastic bag. Use sticky tape, such as duct tape, to pick up any remaining small
glass fragments and powder. If vacuuming is needed after all visible materials are removed,
vacuum the area where the bulb was broken. Remove the vacuum bag (or empty and wipe the
canister), and put the bag or vacuum debris in a sealed plastic bag.
4. Clean-up Steps for Clothing, Bedding, etc.:
• If clothing or bedding materials come in direct contact with broken glass or mercury-containing
powder from inside the bulb that may stick to the fabric, the clothing or bedding should be thrown
away. Do not wash such clothing or bedding because mercury fragments in the clothing may
contaminate the machine and/or pollute sewage.
• You can, however, wash clothing or other materials that have been exposed to the mercury
vapor from a broken CFL, such as the clothing you are wearing when you cleaned up the broken
CFL, as long as that clothing has not come into direct contact with the materials from the broken
bulb. If shoes come into direct contact with broken glass or mercury-containing powder from the
bulb, wipe them off with damp paper towels or disposable wet wipes. Place the towels or wipes in
a glass jar or plastic bag for disposal.
5. Disposal of Clean-up Materials
• Immediately place all clean-up materials outdoors in a trash container or protected area for the
next normal trash pickup.
• Wash your hands after disposing of the jars or plastic bags containing clean-up materials.
• Check with your local or state government about disposal requirements in your specific area.
Some states do not allow such trash disposal. Instead, they require that broken and unbroken
mercury-containing bulbs be taken to a local recycling center.
6. Future Cleaning of Carpeting or Rug: Air Out the Room During and After Vacuuming
• The next several times you vacuum, shut off the central forced-air heating/air conditioning
system and open a window before vacuuming.
• Keep the central heating/air conditioning system shut off and the window open for at least 15
minutes after vacuuming is completed.
• The CFL or Compact Fluorescent Lamp is
a fluorescent tube bent around itself with
the ballast in the base. It suffers all the
same problems of the larger tube lamps.
• Life expectancy is about 10,000 hours
with the best units. However, since these
lamps have starter filaments, the act of
turning them on and off will shorten their
life. Life is also affected by heat, many fail
in a short time.
• CFLs are fragile. Since the Edison socket
does not give positive feedback, you do
not know how hard to twist the bulb. A
little too much pressure, and the thin
glass envelope cracks, destroying the
lamp. Screwing it in with just gripping the
base isn’t practical with small can light
fixtures.
• CFLs require time to warm up to full
brightness. They either do not dim at all
or dim very little with visible flicker and
audible noise.
•Other lamps that contain mercury are:
•Mercury Vapor
• All fluorescents
• High Pressure Sodium (HPS)
• HID’s
6. SSL advantages to TCO
• Total Cost of Ownership
Installing a lighting system is a commitment to keep it operating at peak performance.
Everyone has experienced entering a store or hotel where the overhead or cove
lighting is banks of fluorescent lights. The lamps are invariably mismatched in
color from warm to cool white, sometimes in the same fixture. I doubt the
lighting designer had those particular mixtures in mind. Manufacturers do not
guarantee their light will match light color or light output to another
competitors lamp. And yet, facilities managers buy from whatever source is
available at the lowest cost.
Many of the lamps invariably flicker due a failing ballast, lamp wear, or a poor
connection. They usually hum at the line frequency. Looking up at the hundreds
of bulbs you can see the bare lamps covered in dust and those that have lenses
are discolored or dirty. The dust is charged by the high voltages and is attracted
to the lamps and fixtures. It is impossible to keep them clean. Dirt affects light
output and therefore system efficiency. So who is supposed to keep this system
efficient, you are. It certainly was not designed to be efficient by itself.
Now add in scheduled maintenance replacement for lamps and ballasts. Given the
poor lumen maintenance of the lamps, new lamps next to older lamps is readily
discernable. Therefore entire banks are replaced whether they need it or not.
This brings to question then, how many of these lamps actually reach full life
since they don’t wait for them to burn out? This impacts cost directly in parts
and labor to keep the system operating.
This is a system designed to be a maintenance headache from the moment it is
installed to the day the building is physically destroyed. This is what I mean
about True Cost of Ownership.
Incandescent lamps are no better than fluorescent given their short life spans. The
basic life is measured by taking a group of 100 lights, turning them on, then
measuring how long it takes for half of them to completely die. That number is
the basic life of the lamp. The useful life is about 60% of that due to lumen loss
over time. So a 1000 hour lamp is usually replaced in 600 hours due to lumen
loss, not at the 1000 rated life. This means you will replace this lamp 100 times
in the life of one Silescent fixture.
Now imagine a 30 foot ceiling with both of these systems installed needing constant
maintenance. An auditorium is particularly bad since people would notice burnt
out lights and flickering ones immediately. Color matching is imperative. Once
the chairs are installed, just how easy is it to change the lamps or clean the
fixtures? All these aspects affect Cost of Ownership. Now read the section to
the left and see how a system can be created for zero maintenance.
The Silescent Light reduces the Total Cost of
Ownership to a facility manager. The expected
life is over 100,000 hours of operation. Assuming
10 hours of operation at full power every day of
the year, the light will lose 30% of its initial
lumen output in 27 years. The 30% number was
selected based on a study that people working in
a building did not notice the light loss until 30%
was reached. It has become an accepted
standard of life for LEDs.
The Silescent Light will continue to slowly decay
linearly until zero light output is reached. There is
no filament to break or connection to corrode.
The Silescent Light requires zero maintenance,
there is nothing to replace. However, Inteltech
recognizes the fact that after 27 years a facility
manager may want to begin re-lamping the
facility. A program may be instituted where the
lights can be returned to the factory for re-
lamping for a nominal fee, far less than replacing
the fixture. Of course, by then who knows what
will be possible.
The lumen output of today’s LEDs is expected to
double every 18 months for the foreseeable
future. They already exceed the CFL in efficiency
when compared fixture to fixture. This means in
27 years the only lights in the world will be LEDs.
Are you sure you want to design a new facility
with outdated technologies?
7. The right decision pays over
time…
• Designing “Green”
Designing “Green” means some hard choices must be
made. The old way of doing things must be abandoned
for newer technologies. Newer technologies cost more
because manufacturing volumes are low.
“Green” also means looking at the total impact our
decisions cost us, society, and the natural environment.
For instance, when choosing a lighting system based on
mercury such as fluorescents, HIDs, Mercury vapor,
HPS, etc. versus using a technology made from sand.
Although the DOE attempts to explain the hazard
away, it is still hazardous waste and must be dealt with
by someone. We must pay for it’s safe disposal or
recycling either through taxes, direct cost, or
environmental impact. We must pay attention at all
times where these products end up. Since our society is
rapidly becoming one of no responsibility, no one pays
attention and so they end up in our landfills.
SSL technology uses no toxic materials and is 98%
recyclable. The aluminum fixture can be recycled if
needed or simply re-lamped after 25 years.
System cost:
• Initial component cost
• Installation cost
• Operational cost
• Energy cost
Direct energy
HVAC energy
• Ongoing maintenance
• Component replacement
• Labor cost
• Purchasing
• Storage
• Maintenance Personnel
• Equipment
• tools
• ladders
• man-lift
• Add all these costs over the life of
the building when comparing lighting
technologies.
8. Green… at what cost?
• Energy Efficacy
– A Fixture Comparison
A small candle 0.1 Lumen/watt
Kerosene Lamp 1.4 Lumen/watt
Small fluorescent 2 Lumen/watt
Incandescent (regular) 2.5-7 Lumen/watt
Halogen 5-11 Lumen/watt
CFL 35 Lumen/watt
Silescent SSL (color dep) 26-47 Lumen/watt
4’ T5 (fixture dep) 35-50 Lumen/watt
4’ T8 (fixture dep) 40-60 Lumen/watt
Traditional light made form burning fuels is quite low.
People turning to the old ways, thinking they are
saving the planet, are quite mistaken. Converting
fuels to electricity and then to light is about 2000
times more efficient.
It’s fashionable to be “green” these
days, but just how committed are we?
Some terms:
Fixture Efficacy =
Lumens Out/Power into Fixture
Lm/watt
System Efficacy=
Total Lumens Out/Power into System
Lm/watt
Installation Fixture Cost=
Components+installation
Long term recurring maintenance
costs
9. AC vs DC Lighting Systems
• Efficiency vs Efficacy
Designers, engineers, contractors, building owners, and whoever
may in charge of the design, construction, and maintenance of
a building need to understand the difference between
Efficiency and Efficacy.
Efficiency deals with the ratio of Power In/Power Out. This usually
has no units attached to it since watts are divided by watts and
is a ratio. For instance, a power supply may be 90% efficient at
converting power. The 10% is loss in heat and EMI radiation.
Efficacy defines efficiency between different units. For instance in
lighting systems, the ratio is Total Lumen Output/Total Power
Consumed is the System Efficacy. This is very difficult to
measure in a building and must be calculated as the sum of the
efficacies of each component. The total power in is also
difficult to measure unless that power is solely used by the
system.
Efficacy may also be specified for a single luminaire as the Total
Lumen Output/Total Luminaire Power. This number takes into
account the losses both in electrical power (ballasts and wiring)
and lumen losses in the fixture due reflection and filtering. The
luminaire must be tested in a laboratory to determine its total
lumen output. If you change the bulb, you get a diferent value.
Since bulbs and lamps come from many manufacturers, the
value is really a “best guess”.
The mechanical part of the fixture has a lumen efficiency which is
the Total Usable Lumens Out/ Total Lumens Produced (by
lamp). Most fixtures range in efficiencies between 30-70%.
Obviously, the less the light is reflected or filtered, the more
light you will get. It is not sufficient to look at lamp/bulb lumen
output numbers when designing a system, The fixture will
determine the final lumen output.
AC lighting is the normal route most designers
take. AC distribution uses high voltage, so it uses
less copper per watt. However, AC systems suffer
voltage loss just like DC systems. The longer the
wire the more loss in voltage. Current is not lost
in the wire, it uses up the voltage to get to its
destination. Voltage dependent components
such as incandescent lights will be visibly dimmer
the longer the wire run.
DC lighting systems are Low Voltage. The
maximum voltage allowed is 30 VDC. Wires
limited to 60 watts maximum can be ran without
conduit under Class 2 wiring practices by the
NEC. Wires handling 60-1000 watts must be ran
as Class 1 wiring, just like High Voltage.
Silescent brings to the lighting designer a real low
voltage solution. Each light contains a ballast
which is 92% efficient at converting the power to
drive the LEDs. The ballast also automatically
adapts to voltage loss in the wiring so that each
light is perfectly matched to every other light in
the system. A large , remote mounted power
supply can be used to provide multiple 25 amp
circuits and act as a system power source. The
power supply offers many advantages to the
building owner and the power generation
company.
(continued)
10. Lamp Life Facts
• LLF (Light Loss Factor)
A clean new fixture with a brand new bulb puts out the
maximum lumens the fixture will ever produce. It’s all
downhill from there with standard lamps. The first loss
occurs as the lamp gradually fades from initial lumen
output to average lumen output over its life. The
second loss occurs as the fixture and lamp get coated
with dust and grime. Lights placed in areas where oils
and grease are prevalent will lose even more lumens.
Fixture and bulb cleaning directly affect light output
and Cost of Ownership since someone must be paid to
clean the fixtures. This gets very expensive when these
fixtures are hard to reach.
Any high voltage source will charge dust particles. The
strike voltage in most fluorescent systems is over 600
volts. The higher the voltage, the more dust will be
attracted to the lamp. Think of the air purifiers sold to
remove dust and particulates from the air. These units
use very high voltages to the same thing.
A low voltage system will not charge the particles and
therefore stay cleaner naturally.
A lighting designer must consider in his
calculations at least a 10% loss of light
due to dust accumulation on the lens
and lamps (LLF). An additional 20%
loss must be factored in to cover light
loss due to aging of the lamp. This real
lumen out is the average lumen output
over the expected lamp life which is
about 30% less than the initial fixture
lumen output value.
For example, a 200 watt incandescent
halogen lamp may put out 3200
lumens. The fixture optical efficiency
may come in at 50%. This means that
the lumens able to escape the fixture
is usable light. The rest is lost to
internal reflection. Now the lumen
level is 1600 lumens. Now add in
lumen maintenance or LLF factors of
30% and the lumen output is 1120
lumens. This is the real light level over
the life of the lamp that this fixture will
put out as usable light.
11. DC System Design
• DC Lighting and Power Factor Correction (PFC)
Everyone is familiar with AC powered lights. Each AC powered Led light must convert the high
voltage AC to low voltage DC to operate. However, this process is complicated by laws
limiting Current Harmonics and Power Factor. The laws are trying to reduce energy
losses between the Power Generation Company and the Building. The technique for
solving the problem is called Power Factor Correction (PFC). Current distortion is a
different problem but the same fix solves both at once.
In an AC system each light must employ PFC circuitry to the ballast, this adds complexity which
increases cost and reduces reliability (more components). The main problem is with the
storage elements in the ballasts. For low voltage circuits, ceramic capacitors are used.
For high voltage circuits electrolytic capacitors are used. The ceramics have a long life,
electrolytics dry out and fail sooner. An AC ballast can be rated for 50,000 hours while a
DC ballast is rated for 100,000 hours. The difference affects the Cost of Ownership of a
system and must be factored in when deciding on AC or DC for your lights.
DC systems offers an alternative to each light needing the PFC circuitry. A remote power supply
connects to the AC mains and converts the AC voltage to a DC voltage in one place. The
power supply has the PFC circuitry built into it so the entire system appears as a resistive
load to the Power Generation Company. This means the Current Harmonic Distortion
and the reflected power are minimized which makes creating and distributing power
more efficient. This helps the power company be efficient which translates to less oil
and coal used to make electricity. PFC also helps reduce wire burn-out and transformer
burn-out, thereby reducing maintenance costs for the building owner. These remote
power supplies also provide immunity against brownouts and voltage dips. Each supply
can operate from 85V-265 VAC and will provide consistent power to the lights over this
input range. The supply also blocks any conducted noise to the power distribution
system that may come from the lights. The lights will be rock solid with fluctuating AC
power.
DC distribution is also inherently safer for everyone involved in installing and maintaining the
system. You can literally grab the wires directly with no harm. This was not possible
before Silescent technology produced lights with sufficient lumen output to be used to
for general lighting. The Silescent Lights will scale from 600 – 5000 Lumens. Right now
only 600, 1100, and 1700 levels are available.
The other reason low voltage DC is viable is the Silescent Light automatically adapts to voltage
loss in the wires. It is unresonable to expect a electrical contractor to lay out the system
always concerned about voltage loss. The adaptive nature of the Silescent Light allows
the contractor to wire the system with the shortest paths possible with the heavy wire.
He can create zones with the low voltage control wiring which is much smaller and more
flexible, by connecting the control input together to make a zone. The control wiring is
then returned to the control point rather than running power wiring to control points.
This saves money by reducing the labor and component cost to the contractor.
Hopefully, he will pass this savings on to the building owner.
DC lighting systems offer alternatives to design and
installation unavailable to AC lighting systems. Let’s
explore how to go about doing it.
• First determine the lumens/square ft required for
each area. Ceiling height affects light levels because
light dissipates the farther it is from the light source.
Beam angles and fixtures also act to focus light for
specific tasks. Once the lumen/square ft is determined
the number of fixtures can be calculated and their
spacing in the ceiling determined.
• Silescent Lights are grouped by their control wiring,
not the power wiring. Size the power supplies to be
80% of the load. Assume that the power supply cost
will be around $0.35 to $0.50/watt. Size the power
wire to 12 gauge and use Class 1 wiring practices. Even
though it is low voltage the possibility of fire is
increased with the power levels involved (1000 watts
max per wire).
• If this is a large installation, contact Inteltech
Corporation for assistance on the layout. We have
software which can model your installation and
optimize the time and costs required. The wire
resistance of 12 gauge copper wire is 0.00187
Ohms/ft. Current flows in a circle and voltage is lost on
both the feed and the return wire. 12 gauge wire is
limited to a 20 amp breaker by NEC. The 80% rule
should apply for the breaker, so consider 16 Amp
loads flowing through the wire maximum design load.
This means a 1000 watt, 24VDC power supply would
feed two 12 gauge circuits or 3 14 gauge circuits. Since
the lights will be attached at intervals along the wire,
it is not a straightforward calculation as to the total
possible length. (continued next page)
12. DC Installation Guide
(cont)
Light Voltage Current
1 23.57 1.61
2 23.23 1.64
3 22.37 1.70
4 21.83 1.74
5 21.28 1.78
6 20.74 1.83
7 20.19 1.88
8 19.65 1.93
It should be becoming apparent that each light appears as a different resistance to the power supply.
Most lighting installations should have equally spaced lights and this method would work fine.
Locate the power supply as close as possible where it is convenient for mounting and inspection.
The distance to the AC breaker panel is not critical. The power supplies have universal AC voltage
input ranges from 85-265 VAC and will adjust to whatever power is available. The supply will also
maintain a constant voltage output at the output terminals. It is possible to adjust the supply to 30
volts legally to extend the wire run and allow a 14 volt drop. But this is the legal limit.
Let’s discuss a practical approach to designing your wiring runs, sizing your power supply, and choosing
your wire size. One note here is that a breaker is used to protect a wire from creating a fire under
a fault condition. A 12 gauge wire is protected with a 20 Amp breaker. Using the 80% rule for
breaker loading, a lighting string may draw 16 Amps continuously without overheating the wire.
It is important to note that wire conducts electricity. Electricity is the flow of electrons through the wire.
Voltage is the pressure which causes the current to flow from one end of the wire to the other. It is
the voltage that is lost when currents flow in wire, the current is unaffected by wire resistance.
Voltage loss is very important to calculate in a system since all electronic ballast are rated for an
operating range.
The second point is that the voltages available from the power company have a operating range. The
operating range for America is 105-132 VAC. A constant power device will draw less current at
higher voltages and more current at lower voltages. This is same principle behind motors that
must turn a loaded shaft. The motor will draw more current if the voltage droops. The reason is
the load is unchanged and the same power is needed to turn the shaft.
Let’s assume a Silescent 200i light is
spaced every 10 feet along the wire. The
light draws a constant 38 watts at full
power. Power equals voltage times
current. The light is a constant power
device and will adjust the current drawn
from the wire depending on the voltage
at the point where it is connected to the
wire. This is very different from an
incandescent bulb which will decrease its
current draw if the voltage decreases. But
this how the Silescent Light can produce
equal light output with varying input
voltages. Hopefully, you are beginning to
see the differences.
For example, if you have a 110 foot run of
12 gauge wire and placed at light every
10 feet, starting at 10 feet from the
power supply, the total load lighting load
would be 380 watts. The power supply
would see this load plus the loss in the
wiring. On the right is an example of
typical voltage loss due to wiring and how
the Silescent lights adjust for it.
