High-bays: It's all about the details
By Stan Walerczyk
Introduction
With technology and experience advancing so
rapidly, this is my fifth article on this subject. It started with ‘Comparing
Fluorescents and HID’, 9/98, Energy User News, then came ‘Essay By Invitation’,
4/99, LD+A, followed by ‘Essay By Invitation’, 6/01, LD+Aand ‘Essay By
Invitation’, 2/02, LD+A. Like the previous articles, this one should be taken
as a stop in the road on an endless trip, instead of a final destination.
Intent
Customers deserve more than what is really
marketing hype from hibay manufacturers and sales people. Several T5HO and T8
hibay manufacturers have marketing literature that tries to show that their
products are the best thing since sliced bread. There are also HID
manufacturers that do basically the same for what they sell; for example you do
not need 10 F54T5HOs to be the equivalent of magnetically ballasted 450W PS MH.
I do not like to do business with any party that does not provide accurate and
balanced information. In reality, the footcandles per watt performance of PS or
ceramic MH with high performance dome and electronic ballast is very similar to
T5HOs or T8s with electronic ballasting and good reflectors. Because MH
electronic ballast pricing is significantly coming down T5, T5HO and
electronically ballasted PS MH hibays may cost nearly the same. Although some
of the dimming electronic MH ballasts do cost significantly more, their
flexibility and performance can often provide the best total solution in some
applications. Don’t automatically jump on the T5HO bandwagon, like so many
have. Any of these advanced lighting technologies - T8s, T5HOs, extra-long life
CFLs (compact fluorescent lamps), induction, PS (pulse start) MH (metal halide)
or ceramic MH may be the best solution for specific applications. The intent of
this article is to provide information so you can decide the best technology
for various applications.
Definition of Hibay
Although some people call it a hibay if mounted
over 25 feet high and a lowbay if less than 25 feet high, I do not make that
distinction. I often see typical HID lowbays, the ones with large diameter
relatively flat dome and large drop lens, in ‘hibay’ applications and typical
HID hibays in ‘lowbay’ applications (often because hibays cost less than
lowbays). I am not making a firm distinction between hibays and lowbays.
Quality of Light
In the past horizontal footcandle measurement was
the most common way to evaluate if the lighting was adequate or not. The Ninth
Edition of The IESNA Lighting Handbook has made big strides to expand what
constitutes good lighting. This includes glare, contrast ratios, shadows, color
appearance, vertical footcandles and horizontal footcandles. I highly recommend
reading chapters 10, 19 and 20 of the IESNA Handbook as well as the new IESNA
Recommended Practices For Lighting Industrial Facilities and Sports &
Recreational Area Lighting. www.iesna.org
Although fluorescent lamps are available with up
to 95 CRI, the lumens are much less than for 8586 CRI fluorescents. Most
fluorescent hibays have 85 – 86 CRI lamps, which have better color rendering
than all HID, except the new ceramic MH lamps, which have 90 – 96 CRI without
sacrificing light output. There are also 5000K 90 CRI PS MH lamps that have
slightly less photopic lumens per watt than lower Kelvin and lower CRI PS MH
lamps, but the higher scotopic/photopic ratio, described in the next section,
can compensate for the lower photopic lumens.
For some applications, well designed linear
fluorescent hibays are better than well designed HID hibays with regard to
glare, contrast ratios and vertical footcandles. Following are two application
examples. Imagine yourself playing volleyball. As you follow the high arching
ball coming towards you, would you prefer having to look up into a point source
HID hibay or a 4’ or 8’ long fluorescent hibay with four F54T5HOs or six
F32T8s? Imagine yourself as a forklift driver having to deal with vertical
surfaces and load and unload pallets in high warehouse racks. Compare vertical
footcandles with well designed 4’, 8’ or extended row linear fluorescent hibays
mounted in the middle of rack aisle row parallel to the racks with well
designed HID hibays mounted in the middle of rack aisle row. Envision how
easily a loaded pallet can block the light from the point source HID lamp.
For other some applications, like retail, PS or
ceramic MH in clear prismatic hibay domes provide more uniform uplight, can be
considered more aesthetically pleasing, and maintain the traditional hibay look,
compared to most fluorescent hibays with or without uplight.
There often needs to be more than just hibays for
good lighting. Lower mounted hooded industrials or other task lights are often
required in industrial settings. Dimmable PAR-halogens are very helpful for
dances, plays and presentations in gymnasiums. Emergency lighting is usually
required.
Two Ways to Measure Light
The long established way of measuring the amount of
light has been with photopic lumens, which are the lumens listed in lamp
catalogs. Another way is combining photopic and scotopic lumens, based on Dr.
Sam Berman’s and others’ work. I believe that the latter is more based on how
the human eye really perceives light at common interior light levels. The
various lighting studies by Berman, et. al. over the last 15 years have
concluded that general lighting with high scotopic to photopic ratios (S/P),
typically characterized by high color temperature lamps, provide better visual
acuity. ‘Visual Acuity Depends on the Color Temperature of the Surround
Lighting’ by Mojtaba Navvab, which was published in Summer 2001 Journal of the IES
and ‘Using Visual Acuity to Measure Display Legibility’ by Sheedy and Bailey, Work
With Display Units 94, Creico et-al. Elsevier, Amsterdam, 1995, show
significant visual acuity gains and faster reading times when using high S/P
general lighting. The easiest to read is Berman’s ‘The Coming Lighting
Revolution in Lighting Practice’ in October 2000 Energy User News, which is
downloadable at www.energyusernews.com
Personal experience can be more relevant than
research. What do you think is brighter in an apples to apples comparison, a
new 38,000 photopic lumen 400W MH or a new 50,000 photopic lumen 400W HPS?
People that I have talked with that have seen this comparison have said the MH,
even though it has 24% less photopic lumens. You can do the same exercise with
5000K and 3500K F32T8s that have the same CRI and photopic lumens. Guess what
the answer is -- the scotopically enhanced 5000K.
In the past fluorescents had the edge regarding
availability of high scotopic/photopic ratios. But 5000K PS MH lamps are being
introduced.
Whichever camp you are in, the two tables in the
Table Time section provide useful information based on photopic lumens and also
task modified lumens.
It requires experience and expertise to properly
design lighting systems based on S/P ratios, because color tone preferences and
ambiance issues can be very important.
Hopefully lamp manufacturers will provide more S/P
ratios in their catalogs, websites or spec sheets.
Be aware that the IESNA does yet not accept the
principle that light levels can be reduced below IESNA’s existing illuminance
recommendations by the use of scotopic enriched lighting.
Temperature - Lamps
The light output of HID lamps is relatively
constant with relationship to temperature. On the other hand the light output
of most fluorescents is very dependant on ambient temperature. If the ambient
temperature is cold or ranges from cold to normal, the problem can usually be
taken care of with tube guards, lenses and/or enclosed fixtures, because they
can raise the ‘ambient temperature’ right next to the lamps. With certain
ballasts, sealed fixtures and tube guards, T8s and T5HOs can be operated
slightly below –18o C (0o F). The downside is that any tube
guard or lens will block some of the light. For fairly hot applications, vents
in the reflectors, which also provide some uplight, and no cover over the
reflectors can dissipate heat from near lamps. If the ambient temperature is
too hot or ranges from cold to hot, there is no easy solution.
Optimal ambient temperatures are listed for
specific fluorescent lamp type in the Hibay Options Section. When the ambient
temperature frequently reaches 49o C (120o F) at mounting
height, which is not that uncommon in warehouses that do not have adequate
venting or air conditioning, PS or ceramic MH may be a better option than
fluorescent. For the majority of applications temperature is not a major
concern for fluorescent lamps in hibays, except for biaxial lamps. The table’s
light output quantities are based on optimal temperatures and can be easily
modified for other temperatures. You can get lumen and temperature tables from
the lamp manufacturers. However, this does not accurately predict how lamps
will perform in specific hibays under various ambient temperatures. Hibay
manufacturers should be able to provide this data.
The major lamp manufacturers are working on adding
amalgam or using some other technology so T5HOs will be able to provide more
light at cold and maybe also hot temperatures. Some fixture manufacturers are
working on heating or cooling the ‘cold spots’ of T8 and T5HO lamps to increase
light output.
In areas with skylights, the daylight contribution
can often mitigate the reduced light output from fluorescents when they are the
hottest.
Don’t base your decision solely on point-by-point
computer layouts when comparing, for example, T8 vs. T5HO. What looks best that
way is often not reality. At certain temperatures a specific T5HO hibay
outperforms a specific T8 hibay and at another temperature the same T8 hibay
outperforms the same T5HO hibay. Some manufacturers have less concern for
thermals than others. Bottom lenses, uplight vents in reflectors, etc, can
complicate the basic rule that T8s provide more light when it is cooler and
T5HOs provide more light when it is hotter.
Temperature – Ballasts
Temperature is usually not a concern with HID
magnetic ballasts, but may be one with at least some HID electronic ballasts.
Even if the HID electronic ballast is rated for 90o C (194o
F), one ballast manufacturer recommends a maximum ambient temperature of 40o
C (104o F), and another one recommends 55o C (131o
F). If heat sinking in ballast compartments improves, then electronic HID
ballasts will be able to be used in higher ambient temperatures.
Temperature is definitely a concern with
fluorescent electronic ballasts.
Hot temperatures can dramatically reduce the life
of many electronic fluorescent ballasts. A typical maximum ballast case
temperature rating is 70o C (158o F), which can often be
reached when the ambient temperature is 57o to 60o C (135o
to 140o F). It really depends on how the fixture dissipates heat. At
70o C (158o F) ballast case temperature the rated ballast
life is often listed at 60,000 hours. At about 10o C (18o F)
higher ballast case temperature, ballast life may be reduced to 30,000 hours.
At about 10o C (18o F) lower ballast case temperature,
ballast life may be increased to 90,000 hours.
I highly recommend fluorescent hibay manufacturers
that have good heat sinks and venting in the ballast compartment. Several
companies have introduced 90o C T5HO ballasts, which help reduce
this potential problem. But the 90o C ballasts only have a 3 year
warranty when the case temperature is between 70o and 90o C,
and do not yet have a proven track record.
Ballast temperature tends to be more problematic
in T5HO than T8 hibays, because T5HO hibays are narrower so the heat is
condensed from the lamps and ballasting. The heat has caused many T5HO ballasts
to fail prematurely. There are several large national companies that have had
so many problems with poorly designed T5HO hibays that they do not want to
consider them in any new projects.
One ballast manufacturer began including a strip
of mylar in a percentage of their T5HO ballasts. If the film shows that the
maximum ballast case temperature rating was exceeded, the manufacturer does not
have to replace the ballasts during the warranty period. This is fair, because
ballast manufacturers should not have to replace ballasts that were not
operated according to guidelines. Other ballast manufacturers are considering
similar measures.
In unconditioned spaces that can get hot, I
typically specify that fluorescent hibay manufacturers need to guarantee that
at an ambient temperature of 52o C (125o F) the maximum
electronic ballast case temperature will not exceed 70o C (158o
F). Many fluorescent manufacturers, that do not provide large ballast
compartments or ballast compartment venting and use steel instead of much
better heat sinking aluminum, cannot honor that guarantee. Ideally their design
should prevent ballast case temperature from exceeding 60o C (140o
F), for extra ballast life.
Lamp Lumen Maintenance The amount of light that a
lamp provides as it ages is much more important than when it is brand new. Many
people use mean or design lumens, which is the percentage of light measured at
40% of rated life compared to initial light output. This is usually listed in
lamp catalogs. I prefer end of rated life lumen maintenance, which provides
worst-case information (I know of very few facilities that group relamp, which
is typically recommended at 70 – 80% of rated lamp life). End of life lumen
maintenance is usually not listed in lamp catalogs but can be obtained from
lamp manufacturers. Yes, PS and ceramic MH have much better lumen maintenance
than standard MH. But with typical magnetic lead ballasts, which are also
called CWA (constant wattage autotransformer) ballasts, the lumen maintenance
of PS and ceramic MH still pales in comparison to high performance
fluorescents. With magnetic lag ballasts, which include reactor and modified
reactor (HX) types, PS and ceramic MH’s lumen maintenance is substantially
improved, because the current waveform is much more sinusoidal. Up another
notch to electronic ballasts that have avalanche enhanced starting and high
frequency current waveforms, the lumen maintenance of PS and ceramic MH get
closer to the lumen maintenance of high performance fluorescent. It appears
that the more dimming with electronic ballasts, lumen maintenance can near 80%
at end of life for PS MH lamps. So be leery of comparisons from fluorescent
hibay manufacturers that only use the worst case 65% mean or 45% end of life
lumen maintenance for standard MH and 75% mean or 65% end of life for PS MH.
Dimming electronic ballasts for PS and ceramic MH allow for a good lumen maintenance
system. A closed loop photocontrol system can be placed in each hibay, so a new
lamp will be under-driven and as the lamp ages, it is driven harder. T5HOs and
high performance T8s have mean and end of life lumen maintenance from 90 to
95%.
Luminaire Efficiency
Higher luminaire efficiency is not always better.
A bare lamp fixture has 100% luminaire efficiency, but only 50% of that light
may actually be useable. Although lowering HID lamps or having slanted biaxial
lamps extending down below the bottom of the hibay improves luminaire
efficiency it may reduce the amount of light that hits the target area.
No matter what type of hibay, a bottom lens will
reduce luminaire efficiency about 10 percentage points. So if a hibay without a
lens has a 75% luminaire efficiency, adding a lens would bring it down to about
67%. All listed luminaire efficiencies in this article are with open bottom -
without a lens.
Metal Domes
Most generic round metal dome hibays provide 70 to
80% luminaire efficiency. Either all of the light can be directed down or there
can be some slats, which provide some direct uplight.
Faceted Metal Domes
These provide higher luminaire efficiencies than
basic spun aluminum domes. They are also available with additional inner
reflector. Luminaire efficiencies can range from 80 to 94%.
Glass Lined Domes
They are also available with additional inner
reflector. Luminaire efficiencies can range from 80 to 94%.
Prismatic Reflectors
These dome shaped reflectors are available in
glass and acrylic. These cost more than metal domes, but provide higher
luminaire efficiency, mainly because some of the light is prismatically
reflected instead of surface reflected, and a small portion of the light passes
through the dome to provide side and up lighting. Luminaire efficiency can be
around 93%, but how much of the side and uplight is really useful for specific
applications? Clear ribbed or prismatic reflectors can often help eliminate the
‘cave effect’ by brightening the ceiling and upper walls, which can be very
important in numerous applications. But the uplight is often wasted with dark
colored ceilings. Contrast ratios are really only improved with white ceilings.
Ceilings can often be quite well lit without any direct uplight. An example are
highly polished or waxed gym floors, which reflect a lot of downlight up to the
ceiling and upper walls. Excessive dirt depreciation in dirty environments is a
definite possibility. Also the lower wattage pulse start MH lamps are only
rated for 15,000 hours, so having to replace lamps more often may not be cost
effective. However, dimming electronic ballasts could be used with a higher
wattage 20,000 hour rated lamps, consuming the same wattage as lower wattage
lamps Several manufacturers provide outer prismatic reflector and inner metal
reflector systems. Luminaire efficiency can exceed 93% with more of the light
directed down.
Metal Linear Reflectors
Most manufacturers use 95% reflective enhanced
aluminum, which is very scratch resistant. There is also a new 98% reflective
silver, not film, which may cost 20 to 40% higher to end customer. 90 – 94%
reflective white reflectors are often a good option for low mounted hibays to
reduce glare. Based on physics, higher luminaire efficiencies are possible with
reflectors with 5/8” diameter linear T5HO lamps than 1” diameter T8s, biaxial
lamps or triple loop CFLs. T5HOs are the closest to a line source or linear point
source.
Without playing games, the best luminaire
efficiency for T5HO and T8 hibays with metal reflectors that I seen is about
93%. Luminaire efficiencies are typically lower for other fluorescent hibays
with metal reflectors.
I strongly agree with ‘Photometry for T5
High-Output Lamps and Luminaires’ by John Zhang and Peter Ngai at
Peerless/Lithonia. It was published in the Journal of the IES.
It promotes a new protocol for T5HO luminaire efficiency. It is foolish for
luminaire manufacturers to state over 100% luminaire efficiency, because
luminaires are tested at 25o C (77o F), while T5HO lamps
provide optimal light output at 35o C (95o F). One way to
supposedly get over 100% luminaire efficiency is to allow the heat of the T5HO
lamps to increase the temperature next to the lamps in a luminaire that the
heat cannot easily escape from close to the lamps, so although the true ambient
temperature is still 25o C, the modified ambient temperature by the
lamps is 35o C. Another way to supposedly get over 100% luminaire
efficiency is to do the testing at 25o C and use a multiplier for
the lamps.
Luminaire Dirt Depreciation (LDD)
LDD is not included in the table, because I have
not seen substantial information on this. In dirty environments, LDD can be
more significant than lamp lumen maintenance, but the jury is out on how
various lamp types and mounting are specifically affected.
An advantage of horizontal fluorescent lamps is
that about 40% of the light comes from the bottom half of the lamps without
having to bounce off a reflector or refractor like a vertical HID lamp has to.
A negative of horizontal fluorescent lamps is that dirt can land and stay on
the top of them more easily than on vertical HID lamps. Also, since there is
more surface area, it can take more time to clean a linear fluorescent than an
HID hibay.
LDD can be very significant with clear ribbed or
prismatic domes, and over time can block most of the side and uplight in dirty
applications. Where pole changers are used, hibays are not usually cleaned. If
a person gets to the hibay to change a lamp, it is maybe 50/50 if he or she
cleans the inside and the odds are high that outside of the dome will not be
cleaned.
Glass reflectors may get less of a static charge
than various plastics and metals, which may result in less dirt accumulation.
Dirt may affect specular surfaces more, because,
both optical control and reflectivity decrease.
I have not seen any thing definitive on how HID and
linear fluorescent hibays compare with regard to LDD. If anybody knows of good
documentation on this subject, please send it to me.
No matter what type of hibay, it is important to
be aware of various types of dirt. There is dust type of dirt that mainly
adheres when it fall on top of a surface. There are also oily, grimy and
electrostatic types of dirt that can easily adhere to vertical as well as
horizontal surfaces.
The lamp compartments in both fluorescent and HID
hibays can be sealed, have filtered air vents, have chimneys and incorporate
other ways to reduce LDD.
Lamp Life
HID lamps are rated at 10 hour cycles and
fluorescents are typically rated for 3 hour cycles. A majority of hibay
applications have at least 10 hour cycles. Running many fluorescents at 10 hour
cycles will significantly increase rated lamp life. But there is a catch to
this.
Most T8 lamp life is based on being driven with
rapid start ballasts. For hibay applications, 1.14 to 1.20 BF (ballast factor)
ballasts are usually the most appropriate, and the only ballasts currently
available with this high BF are instant start, which can greatly reduce T8 lamp
life in short cycles, which can often occur with occupancy sensors. For T8
hibay applications with instant start ballasts, it is highly recommended to use
high lumen F32T8s that are rated for at least 24,000 hours at 3 hour cycles and
30,000 hours at 12 hour cycles, both with instant start ballasts. Don’t just
look in a lamp catalog. For example, one lamp manufacturer listed 30,000 hour
rated life for one of their F32T8 lamp types in their 2002 catalog, but that
lamp life rating is based on using a specific program start ballast. That lamp
only has a 15,000 hour rating with instant start ballasts. You can get accurate
lamp life ratings based on specific ballast types from various manufacturer’s
websites, headquarters and local reps. A number of ballast manufacturers are
developing high BF program start ballasts for T8s, which could work out great for
occupancy sensor applications, but consume slightly more wattage.
T5HO lamp life is based on program start ballasts,
so lamp life does not degrade that much with short cycles. Be careful, because
there are some instant start ballasts for T5HOs, which cost less and use less
wattage, but lamp life can go down the tubes. It is my understanding that the
major lamp manufacturers may not warranty their lamps with instant or rapid
start ballasts.
Some ballast experts say that PS MH lamp life can
be increased 25% with electronic ballasts that have avalanche starting, but we
will have to wait for lamp manufacturers to make that claim. Lumen maintenance
is still good at end of life, and extended lamp warranties have been provided.
The old workhorse, 400W standard MH lamps can
often last 30,000 hours, but are only rated for 20,000 hours because lumen
maintenance gets very low past 20,000 hours.
No matter the lamp type, at least 20,000 hour
rated lamps are recommended for hibay applications.
Lamp Maintenance
Standard and pulse start MH lamps should be turned
off at least once every week to reduce the risk of nonpassive failures in lamps
which are not containment ‘O’ rated. I like the ‘spin’ in the term ‘nonpassive
failure’, after seeing the damage done to fixtures from this. It is surely not
passive. It is worth noting that the number of MH lamps with the ‘O’ rating are
increasing, which encourages the use of open luminaires.
HID people often state ‘why would you want to buy
and replace all of those fluorescent lamps in each fixture?’. Fluorescent
people tend to often reply ‘with only one lamp in a hibay, when that lamp burns
out, you need to replace it ASAP, because with the one lamp out, there is one
big dark space’ unless the system was designed for significant lighting
overlap. For some applications it is a big plus to use a pole changer to
replace HID lamps. If a pole changer can not be used, like when there is a
bottom lens or wire cage, then maintenance is often better (a.k.a. less urgent)
with multiple T8s and T5HOs than with single HID lamps.
When maintenance costs are very high, induction
systems may be the best option.
Controls Historically controls have been very limited
with HID lamps and magnetic ballasts, because of lamp warm up and restrike
times. For example, in most gyms, the HID hibays are turned on at the beginning
of the day and left on until closing, because of the long warm up and restrike
times. High/low control systems can save some energy, but it is not one-to-one
between wattage and light output. For example, if the light level is at 40%,
the wattage may be about 60% of maximum, only saving 40%. HID lamp life can
suffer with high/low magnetic systems. In many applications the highlow feature
simply masks the fact that you have to run the system at 50% load, even when
the lights aren’t needed at all. The low wattage of most high/low control
systems is usually higher than the maximum wattage of the equivalent F54T5HO or
F32T8 system. HID dimmable electronic ballasts are much more control friendly.
The relationship between light output and wattage can be much more linear and
efficacy and lamp life may be improved. But the restrike and warm up times are
often still too long for turning completely on and off with occupancy sensors.
Gyms are a very good application. For activities such as conference basketball
games, the light levels can be set at max overhaul or just over court area. For
activities such as PE classes, the lights could be dimmed significantly, which
saves considerable electricity. Because fluorescents are instant on, they are
the most suitable for controls. In gyms, we have found that the burn time is
often reduced 20% replacing HID with fluorescent, because the staff can turn
the lights off when the gym is not used and turn them back on when it is used.
Switches and occupancy sensors can be used to turn on and off all of the lamps.
Although fluorescents have instant on, it takes a short time to reach full
brightness, especially in cold environments. In order to provide sufficient
light right after a sensor turns on a single or bank of fluorescent hibays, it
is often recommended to include more lamps in each hibay in warehouse rack
aisles. An example is to use 6-F54THOs instead of 4-F54THOs to replace a 400W
MH or HPS hibay. Since the burn time is usually greatly reduced, there are
usually substantial KWH savings to offset the use of the two additional lamps
to attain sufficient instant light levels. There are many dimming ballasts for
various fluorescent lamps. Some are proprietary, which only work on one
company’s system and others are nonproprietary, such as 0 – 10V. But if you are
not aware, all 0-10V systems don’t work the same way. Digital addressable logic
interface (DALI) may revolutionize the dimming electronic ballast industry.
Each ballast can be controlled independently or with multiple groups. This
system also has two-way communication, which can allow facility managers to
identify on their computers, burned out lamps and ballasts. DALI is not
proprietary, so several manufacturers are making interchangeable ballasts and
controllers. But until addressing and commissioning become much more simplified
and pricing comes down, I do not think that DALI is ready for prime time.
Regarding fluorescent ballasts, dimming does not
always save as much as you may think. Dimming ballasts are typically program
start, which maintains lamp cathode heating, and as dimming brings down the
light level, cathode heating increases. Both dimming and non-dimming program
start ballasts have a significantly lower BEF (ballast efficacy factor) than
extra-efficient instant start T8 ballasts.
BEF = (ballast factor x 100) /system wattage
This is one reason why instant start T8 systems can save more wattage than program start T5HO systems.
Daylight Harvesting
Although this could be part of the controls
section, this subject deserves more. Warehouses, big box retail, industrial
facilities and gyms are great applications for skylights, which can save KWH
and more important – peak load. I hate to see hibays fully on during the middle
of the day that are underneath or right next to skylights. What a waste! A
photoswitch that has sufficient dead band can work even with a regular magnetic
ballasted HID hibay. Performance is better with a magnetic high/low HID hibay
and dual stage photoswitch. Dimming electronic ballasted HID and a continuous
photocontrol is even better. Daylight harvesting is very easy with
fluorescents, because they have instant on with no restrike time. Fluorescent
hibays can be staged dimmed (step controlled) with multiple fixed output
ballasts and continuously dimmed with dimming ballasts. In addition to windows and
skylights another good application is installing a photocell to fluorescent
hibays close to large roll up doors to turn off power when there is sufficient
day lighting. It is critical to budget sufficient time and money to properly
commission occupancy sensors, photocontrols and other controls.
Miscellaneous
While electronic ballasts can only be mounted up
to 12 or 25 feet from lamps, many magnetic ballasts can be remote mounted 100+
feet from lamps, as long the proper gauge wire is used. In the case of pulse
starting HID lamps, a remote ignitor is used.
Lamps, driven by magnetic ballasts, will flicker
(due to re-ignition every half line cycle), which can be a problem. There is no
120 Hz flicker with electronic ballasts. Some electronic ballasts can be
operated by DC.
Magnetic ballasts can cause stroboscopic effects,
like making a working circular saw or drill press look like they are turned
off. HPS provides more stroboscopic effect than MH. This potential danger can
be reduced by having close-by hibays on different input power phases or having
electronically ballasted task lights. Because electronic ballasts operate at
such high frequencies, there are no stroboscopic effects.
For emergency lighting and instant on, most HID
hibays require an additional high wattage quartz lamp. Since fluorescents are
instant on, back-up quartz lamps are not necessary.
Magnetic ballasts are much more prone to obnoxious
buzzing than electronic ones.
There are some magnetic and magnetic ballasts that
drive two MH lamps, which saves some wattage.
Several manufacturers have or will have 480V T5HO
and T8 ballasts.
Lamp holders deserve mention. European twist lock
sockets are highly recommended for both T8s and T5HOs. For T5HOs make sure that
the lamp holders are rated for the heat. I have seen some that were not and
melted. When retrofit standard MH with PS or ceramic MH, new high voltage pulse
rated sockets may be required. Sometimes mounting the new lamp holder is so much
of a problem, that replacing the entire fixture is less expensive.
Benchmark for Hibay Options
Let’s use the old workhorses, the 400W standard MH
and HPS with metal reflector dome that has less than 80% luminaire efficiency. If
you want to consider mercury vapor, 1000W mercury vapor provides about as much
light as 400W standard MH and HPS. Mercury vapor usually does not die, just
gets dimmer and dimmer over the years.
HPS Option
With its terrible CRI and S/P (scotopic/photopic)
ratio, HPS should be avoided for interior applications. Who wants to hang
around under ugly yellow light?
In the early to mid 90s some of the California
incentive programs basically covered the parts cost of HPS hibays to replace
mercury vapor and old style HO and VHO T12 fluorescents. So many gyms and
warehouses got new HPS hibays. Hopefully utility incentive programs will
finally eliminate incentives interior HPS applications some time.
Although it does not save any electricity, there
are two ways to greatly improve the typical 22 CRI of regular HPS lamps. One is
the color enhanced HPS lamps, which have 65 to 70 CRI, though life and lumen
ratings are greatly reduced, and the color temperature is still only 2200K. The
other is the quartz and ceramic MH retro lamps which are designed to be driven
by HPS ballasts and provide a CRI up to 90. The benefits are often worth the
cost.
Standard MH Option
Pulse start MH has so many advantages over
standard MH, that the latter should get a fond farewell and gracefully retire.
It is a shame how many new standard MH hibays are still being installed.
Some lamp manufacturer sales people try to push
the 360W energy saving standard MH lamps to replace 400W standard MH lamps on
existing ballasts, because it can be quick sale, and a contractor is not
necessary. Except for short term leases, I usually find better solutions.
Pulse Start MH with Magnetic Ballast Option
Moving the starter from the lamp to the ballast
allows for a higher performance arc tube in pulse start MH lamps. From the
design standpoint, 300, 320 or 350W pulse-start MH can replace 400W standard MH
one-for-one, or fewer 400 or 450W pulse start MH fixtures will be required in a
redesign. It is important to determine the exact type of existing 400W standard
MH lamps. If they are basic grade universal mount lamps that are only rated for
about 36,000 initial lumens, then 300 or 320W pulse start lamps and ballasts
may work very well. If the existing 400W lamps are vertical base up with
43,000+ initial lumens, then it may require a 350W pulse start replacement to
match the desired lumen package.
As stated previously there are several types of PS
MH magnetic ballasts, which vary in lamp lumen depreciation and cost. If the
line voltage is 277 and if power quality is good, 277V reactor ballasts are
recommended, because they save wattage compared to multi-tap CWA ballasts.
Existing hibays can be replaced or retrofitted
with ballast, socket and lamp kits. Especially with hook, cord and plug units,
it is often more cost effective to go with new hibays.
With a high performance dome and reflector, a 250W
pulse start MH lamp could maybe replace a generic hibay with 400W standard MH
and magnetic ballast, but the 250W lamps only have a 15,000 hour rated lamp
life.
Sometimes it is difficult justifying the extra
money for a high performance pulse start MH hibay, because basic grade spun
aluminum ones can often cost less than $100. Usually a lighting system with
low-cost basic-grade hibays will cost more than a lighting system with high
performance hibays, because either fewer or lower wattage high performance
hibays will be required.
Pulse Start MH with Electronic Ballast Option
In many applications the only way that PS MH can
really compete with fluorescent is if electronic ballasts are used with PS MH.
Most of the electronic PS MH ballasts are also
dimming, some down to 35%, which can save considerable energy. But in many
applications, dimming is not necessary or cost effective.
Electronic ballasts for 250 to 450W PS MH have
logged millions of machine/lamp hours. More manufacturers are coming out with
their own ballasts, which validates that these ballasts really do work. With
higher volumes and competition, pricing is dropping.
Not all PS MH electronic ballasts are created
equally. At least one manufacturer has avalanche enhanced ignition, which uses
a special wave shape to reduce the energy flow during the starting impulse. The
wave shape and lower energy availability while the electronics are not
thermionic means reduced loss of electrode material during the starting
sequence. This may help on lumen maintenance and lamp life.
Lamp replacement duration may be able to be
doubled in a yoked pair of fixtures with one ballast and two lamps. The ballast
will always start the lamp with the least resistance, so as the lamps age each
one will get about equal burn time.
Dimming electronic ballasts can also help minimize
lamp types and help prevent maintenance people putting the wrong wattage lamp
in certain fixtures. For example, instead of using 175, 250 and 400W lamps,
just the longer life 400W ones can be used through out the facility with
dimming and wattage set for areas that require less light.
At least one lamp manufacturer makes PS MH lamps
that are specifically designed for electronic ballasts.
Ceramic MH with Magnetic or Dimming Electronic Ballast Option
Ceramic MH may be the future of metal halide.
320 – 400W ceramic MH lamps are becoming more
popular in retail and other applications where very high color rendering is
important. With the 92+ CRI, products may be more ‘sellable’ and artwork may
look better.
Although there are fluorescents that have CRI in
the nineties, the lumens drop about one third compared to ones with CRI in the
80s. Ceramic MH does not sacrifice light output for CRI. Lumens per watt for
ceramic MH is almost as good it is for PS MH.
Ceramic MH lamps use the same magnetic and electronic ballasts that PS MH lamps use.
Don’t get sticker shock with ceramic MH lamps;
pricing should come down over time. A less expensive alternative to ceramic MH
lamp may be the 90 CRI 5000K PS MH lamps.
CFL Option
CFLs have much lower lumens/watt than T8s and
T5HOs. There are often eight 42W triple-loop CFLs in one cavity, so ‘how good
can luminaire efficiency really be?’. Don’t be surprised if maintenance costs end
up devouring most of the electricity savings. At 80% of rated lamp life, which
is 6,000 to 14,000 hours depending on lamp manufacturer, cycle length and
ballast type, it can cost $60 to $80 per fixture to group relamp. Plus there’s
labor and often lift rental costs, which can be substantial.
One advantage of this option is that because most
CFLs have amalgam, light output is fairly even from 10o C (60o F)
to 70o C (140o F) ambient temperature.
There are new high wattage and extended life CFLs
that can make this option a lot better. These lamps provide up to 9,000 lumens
at 120W, which is still not that great of an efficacy. They are rated at 18,000
hours at 3 hour cycles and 20,000 hours at 12,000 hour cycles.
Biax Option
40, 50 and 55 watt T5 biax lamps used to be a good
option before the straight F54T5HO lamp evolved. Reflectors can be designed
much more efficiently for a straight lamp than for a biax lamp. A 55W biax lamp
has about the same catalog lumens as an F54T5HO. They even use the same
ballast. But a well designed hibay with four F54T5HOs outshines a well designed
hibay with 4–55W biaxial lamps by about 10%. Biax lamps are not cheap and are
rated for only 12,000 hours for the 55W, up to 20,000 hours for the 40W. At least
on lamp manufacturer may increase life on their 40W biax lamps from 20,000 to
25,000 hours, if program start ballasts are used.
Biax lamps are very temperature sensitive with
regard to light output. In a horizontal position the optimal ambient temperature
is about 30o C (86o F) with fairly steep fall off both
above and below. A couple of years ago, I looked at a cold storage area that
had some 40W biax hibays with no bottom lens. The ambient temperature was about
5o C (41o F), so the light output was only about 50%.
Because of this misapplication, the end customer did not want to even consider
other fluorescent options.
Several manufacturers that used to make biax
hibays have switched over to linear fluorescent hibays.
The new 80W 6000 lumen T5 biaxial lamp could be
useful for some applications, but it is only rated for 10,000 hours.
Induction Option
Induction systems are considerably less
efficacious than other high performance systems, but induction can reduce
maintenance costs more than any other system. When maintenance costs are very
high, induction systems can be cost effective. Examples are erecting a special
scaffold for hard to reach fixtures, renting an expensive lift, and draining a
swimming pool. For these types of applications it can be worth paying up to
$800 for a hibay that the lamp(s) and ballast(s) are rated for 100,000 hours.
Induction systems are a classic Catch 22. They cost so much because volume is
low and volume is low because the cost is so high. But volume is increasing and
pricing is dropping. Additional manufacturers are helping bring the pricing
down. Induction lamps can start at temperatures as low as –40o C and
F, but light output will be low unless bulb wall temperature or amalgam tip temperature
significantly increase. For cold or hot applications, we recommend working with
luminaire manufacturers that have experience with the intricacies of induction
systems.
F54T5HO Option
You probably already know that you can usually
replace a 400W standard MH that has a spun aluminum dome with a 4-F54T5HO
hibay, reducing wattage from about 458 to 234, but there is a lot more to be
aware of. Some T5HO hibay manufacturers also state that 4 F54T5HOs can also
replace 350W PS MH, which is true if the dome is spun aluminum, but not if
there is a high performance dome. As stated earlier, heat can be a big problem
with T5HO ballasts and lamps. Also make sure you are getting program start
ballasts unless you do not care about lamp warranties and lamp life. With
program start ballasts, lamp life rating is 20,000 hours at 3 hour cycles and
25,000 hours at 12 hour cycles. Until there are good program start high BF
ballasts for T8s, T5HOs with program start ballasts can be a better solution for
occupancy sensor applications where the average cycle length is less than 2
hours. But be careful with T5HOs and occupancy sensors in cool and cold
applications. It takes T5HOs quite a while to get to near full brightness after
they are turned on. To make sure there is enough light for people, especially
fast forklift drivers, extra lamps in hibays or some lamps always on, not
controlled by sensors, are recommended. In properly designed enclosed fixtures,
T5HOs can be used in freezer applications down to below o F (-18o
C). But be cautious of using T5HO fixtures in blast freezers, which are
typically colder and have a serious ‘wind’. I highly recommend that designers
and customers require that T5HO hibay manufacturers provide accurate ballast
case temperature and percentage of light output at cold to hot temperatures for
specific hibay models with and without bottom lens, tube guards and uplight
vents. T5HOs provide maximum light output at ambient 35o C (95o
F) in an open lamp test. This is really an indirect reference, because
maximum light output is really based on the lamp’s cold spot. For a T5HO it is
on the glass close to the end cap on one side of the lamp. T5HO lamp pricing is
coming down, but until the three major manufacturers start making the lamps here
instead of shipping from Europe, they will still be considerably higher than
the best T8s. A number of Chinese and other Pacific Rim
companies are shipping T5HOs to North America at quite low prices, but quality
and warranty issues are big question marks. As stated previously, be cautious
of non-program start ballasts. Some fixture manufacturers may try to save a few
bucks getting instant start ones, but lamp life could be much less than
expected especially in occupancy sensor and other short cycle applications. It
will be interesting to see what the major lamp manufacturers come up with to
make light output more consistent across the temperature range. At least one
major manufacturer is developing a T5VHO lamp, which would provide more lumens
than T5HOs. At least one fixture manufacturer offers different reflector
designs for low, medium and high mounting heights. T5HO and T8 hibays do not
have to look like hooded industrials. The luminaires can have horizontal
triangle, square or cross configuration. They can have direct, indirect or
direct/indirect distribution. Four foot long clear prismatic domes are also
becoming available.
F32T8 Option
In many applications I prefer F32T8 compared to
F54T5HO hibays for the following reasons:
- T8 systems typically use less wattage for the same amount of light
- Ballast case temperature is not such a concern,
because T8 hibays tend to be larger, which facilities heat
dissipation
But it still can be an issue
- High performance T8s last longer with 3+ hour cycles
After high BF program start ballasts for T8s become available, this will also be the case for occupancy sensor applications
- High performance T8s cost about half as much as name brand T5HOs
So 6 F32T8s will cost less than 4 F54THOs in an apples to apples comparison
- T8s often allow for lamp minimization in same building and facility
Can use the same lamp type in hibays as in other applications
I used to think that T8 hibays were only good up
to 25 or 30 feet high. Then I increased it to 40 feet. Recently I heard about
one project they worked well at 85 feet. Maybe T5HO hibays are not better at
high heights, like was supposed.
As stated previously, the F32T8s that should
be used are the ones with 3100+ catalog or photopic lumens, although if they
are 5000K, 3000 catalog or photopic lumens are okay. One concern with T8 hibays
is that after the original high lumen lamps burn out, some people replace them
with lower lumen lamps, because they cost less. This can result in insufficient
light levels.
Ballasts with 1.14 to 1.20 BF are usually required, and since the
only overdrive ballasts are instant start, lamp life and maintenance can be a
problem when controlled by occupancy sensors or manually switched too
frequently. Hopefully during 2004 there will be some overdrive program start
ballasts, which would remedy this problem. But be aware that with program start
ballasts, T8 system efficacy will probably be less than with instant start
ballasts.
F32T8s can often be a better solution than F54T5HOs in colder
applications, because F32T8s provide optimal light output at 25o C
(77o F), compared the 10o degree C higher optimal for
T5HOs.
Just like for T5HOs, I highly recommend that designers and customers
require that T8 hibay manufacturers provide accurate ballast case temperature
and percentage of light output at cold to hot temperatures for specific hibay
models with and without bottom lens, tube guards and uplight vents.
At least one lamp manufacturer will honor warranty with up to a 1.32 BF. A 3100 lumen
F32T8 with a 1.32 BF ballast provides 4092 lumens, which is not that far away
from 5000 lumen F54T5HOs. Other manufacturers are considering this at least on
a specific project basis. At least one fixture manufacturer is having good
success with T8s in freezer applications below –18o C (0o
F). There are also T8HOs that work well in cold applications.
Recently I have become aware of several problems with tube guards on T8s. It is very important
to make sure that the tube guard end caps allow for proper electrical
connection and that either instant start ballasts with arc protection or
program start ballasts are used. NEMA has a good document on this. nema.org
T8 hibays, like their T5HO cousins do not have to
look like hooded industrials. They can be designed to have an architectural
flair.
Compare Options
Make your own comparisons. Include quality of
light, S/P ratio (if you want to), end-of-life horizontal & vertical
footcandles, dirt depreciation, glare, distribution, shadowing, spacing
criteria, system wattage, initial parts and installation costs, ambient
temperature range, ballast case temperature ratings, warm up and restrike
times, control flexibility, lamp life, replacement lamp cost, labor cost for
maintenance and lift rental costs. Also compare options within options, like
apples to apples comparisons of various T8 hibays.
WHATEVER YOU DO, PLEASE HELP STAMP OUT
- Standard MH
- Standard HPS
- Basic-grade domes
Table Time
There are three useful tables in this section. The
numbers and rankings in these tables are not set in stone. I encourage you to
use these tables as templates based on specific lamps, ballasts and fixtures
that you are considering. The first one shows how fluorescent with half the
initial catalog lumens can replace basic grade MH and HPS systems. Lamp lumens,
BF, luminaire efficiency, etc. can vary among manufacturers and models, so you
could do your own specific comparisons.
How can fluorescents with half the initial lumens replace HID?
Some examples:
The High Performance Hibay Comparison Table shows
how generic high performance PS and ceramic MH systems compare with T5HO and T8
systems. You can do your own comparisons with specific lamps, ballasts,
luminaire efficiency and distribution, and temperature. S/P ratio can vary
within each lamp type. At optimal temperatures, T5HO and T8 systems do have
better performance than PS and ceramic MH ones, but often the air temperature
by the fluorescent lamps and the fluorescent lamps’ cold spots are not at
optimal temperature. The Temperature/Light Output Table, and similar ones from
other manufacturers, is based on lamps operated in the open air at various
ambient temperatures. But the same information directly applies to the air near
the lamp in the lamp compartment. The lamp compartment can be much hotter than
the ambient temperature. A T5HO will lose about 20% of its light when
temperature near lamp is 26o C (79o F) and 55o
C (131o F). A T8 will lose about 20% of its light when temperature
near lamp is 13o C (55o F) and 46o C (115o
F). At higher and lower temperatures, the reductions are greater for both T5HOs
and T8s. For example, at 16o C (60o F) near lamp, a T5HO
will lose about half of its light, which could be very important with occupancy
sensors in cold applications. The 90 and 92 CRI MH lamps can also be an
advantage compared to fluorescent is some applications. If somebody would make
a 5000K ceramic PS MH lamps, the task modified lumens per watt would be
awesome. Although listed luminaire efficiencies are very similar, some fixtures
aim light differently, which can be very important for some applications.
The bottom line is that no one technology is
superior for all applications.
Case Studies
Pacific Gas and Electric Distribution
Center Fremont, CA
This was one of the early T5HO projects, and it is
holding up quite well. This project demonstrates how installation of F54T5HO
reduced load, but really set the table for a major controls implementation. The
warehouse had mainly 400W HPS high bays mounted at 35 feet height with hook,
cord and plug. In the rack aisles, minor hallway and back open areas, each 400W
HPS hibay was replaced with an 8 ft. hooded industrial hibay that used a cord
and plug and was easily chainmounted. Each new luminaire has 6–F54T5HO lamps, three
program start (1.0 BF) electronic ballasts, 95% reflective specular reflectors,
a power pack, and occupancy sensor. With power feeds running perpendicular to
rack aisles, it was more practical for each hibay to have its own sensor and
power pack than to run low voltage wires among fixtures. We specified hibays
with 6–T5HOs instead of 4– T5HOs, so forklift drivers would have sufficient
light as soon as fixtures turned on, especially on cold days. 8 ft. hibays were
chosen over less expensive 4 ft. luminaires to reduce shadowing. Wattage was
reduced from 450 to 351. Obviously the majority of savings is attributed to
burn-time reduction from occupancy sensors that totally switch off fixtures in
occasionally occupied areas. Sensor time delay was set for 10 minutes in rack
aisles and 30 minutes in minor halls and back open areas. In a similar manner,
1000W MH high bays were replaced with 8’ hooded industrials with 8 T5HOs,
ballasts, sensors, etc. In addition to the 610 watt per fixture reduction there
is again significant KWH savings from the sensors, which are set at 30 minute
delay. In the front open area and major hall shadowing was not a factor, and
traffic is higher during normal operating hours. Here the 400W HPS high bays
were replaced with 4’ hooded industrials with four T5HOs and no sensors.
Wattage was reduced almost 50%. A programmable time clock with digital time
switch override was installed to control burn time. Previously, fixtures in
this area were often left on all night long and most weekends.
Big Box Retail
It seems that all of the big box chain stores are
switching from standard MH to T5HO, T8, PS MH or ceramic MH both for new stores
and retrofits. Some of these chains prefer the traditional HID hibay ‘look’,
instead of linear fluorescent.
Plus the round clear prismatic domes provide more
uniform uplight than linear fluorescent.
Gymnasiums
I have specified replacing HPS and standard MH
hibays with T8 and T5HO hibays in numerous K12 and college gyms. Typically the
wattage was cut in half. With the warm-up and restrike time of the old HID
hibays, the lights had been left on all day, even when not being used for
substantial periods of time. Now teachers, coaches and maintenance folks can
turn the lights off and back on when needed.
One San Jose, CA high school gym had HPS hibays.
After they were replaced with T8s, the varsity basketball coach told me that he
and team loves the new lighting, but they lost their home court advantage.
Before his team was used to the yellow and low color rendering lighting and the
visiting teams were not.
The Solano Junior College Gym in Northern
California had end to end 8’ hooded industrials with two F96T12 VHO lamps. To
avoid expensive inside wireman wages we retrofitted a portion of these fixtures
with specular hood kits and combinations of either 4 or 6 F54T5HOs. The
remaining fixtures were gutted and used as power channels with new ballast
covers. Occupancy sensors were also installed in non-emergency fixtures.
Strong wire cages were used for all of these gym
applications.
Airplane Hangar with 1000W MH hibays mounted at 85'
This is a high security facility that will remain
nameless. Maintenance costs are very high, so the original main concern was to
provide long group relamping intervals in addition to reducing wattage. Before
the retrofit, the group relamping schedule was about 9,000 hours, which is 75%
of the 12,000 hour rated life of the lamps they were using. Some 1000W MH lamps
are rated for 15,000 – 18,000 hours. I considered the pros and cons of three
options - induction, T5HOs and PS MH with electronic ballasting. (T8s, biaxial
lamps and CFLs were not considered at this height)
Induction
Since higher wattage lamps are not available yet, it would take at least four of 150 or 165W
lamps and ballasts to replace 1000W MH. The fixture system wattage would be
about 660 watts. Contractor cost would be about $1500. With mark up and
installation this would be quite expensive. Although induction lamps and
ballasts have a rated life of 100,000 hours, which seems very appealing, there
are downsides. With lamp lumen and dirt depreciation, the lamps and reflective
surfaces would probably have to be cleaned every 40,000 or so hours of
operation, unless a six lamp system would be used and that would be more
expensive and consume more than 900 watts.
T5HOs
It would require a fixture with at least 8 F54T5HO
lamps to replace a 1000W MH hibay. The wattage would be about 468, which is good,
but the group relamping duration would not be. T5HOs are rated for 20,000
hours, which at 75% of that, it would be a 15,000 hour group relamping
interval. Relamping duration could be doubled, but it would require a pair of 8
lamp fixtures with a programmable time clock that would switch power from one
fixture to the other after 15,000 hours, which would increase relamping
duration to 30,000 hours. This would also be expensive.
Pulse Start MH with electronic ballasting
A yoked pair of hibays with one electronic ballast looked like the best total value.
Each hibay would have one 450W pulse start MH lamp, glass lined faceted metal
dome and inner reflector. The luminaire efficiency would be over 90%. The
single ballast will drive the lamp of least resistance at any time. So as the
lamps age and the fixtures are turned on and off, the lamps will get about
equal burn time. With this electronic ballast, rated lamp life may be increased
from 20,000 hours to 25,000 hours. So rated life per yoked pair may be up to
50,000 hours. Based on group relamping at 75% of rated life, the useable life
may be 37,500 hours. Going this or any longer in calendar days would probably
result in unacceptable low light levels due to dirt depreciation. The wattage
would be about 465. Each yoked pair would cost about half as much as a quad set
of four 150 or 165W induction lamps and ballasts. The installed cost for this
option would be significantly less than for the 16 T5HO lamp fixture array.
….then the facility changed priorities.
More light became more important than maintenance
concerns. We decided on replacing each 1000W MH hibay with a yoked pair of
glass lined metal faceted hibays having two 400W PS MH lamps, two electronic
ballasts and two glass lined metal faceted domes, each with its own inner
reflector. Both lamps are on at the same time. Wattage was reduced from about
1100 to 830 and light levels were significantly increased. The group relamping
schedule will still be greatly improved.
Lamp minimization was another benefit. These
dimming electronic ballasts also allowed us to minimize
lamp types. We replaced 1000 MV, 400W MH and 250MH lamps with the same 400W PS
MH lamps with the ballasts dimmed down to appropriate light and wattage levels.
Industrial Facility
This facility now has primarily 250W HPS low bays.
Areas keep changing. What is production now, may turn into a storage area in a
month, which may become an aisle in a year. So design flexibility is very
important. I specified 4’ low bays with 4 F32T8s, 1.15 BF extra efficient
instant start ballast and exposed reflectors to dissipate heat. Replacing 250W
HPS and standard MH with 4 T8s works out better than with T5HOs, because 2
F54T5HOs is not quite enough light and 3 F54T5HOs is too much wattage. Each T8
hibay is specified to have a plug-in occupancy sensor port, lens door
receptacle, and 12’ power cord so mounting positions can be easily changed.
Occupancy sensors should be originally provided for 75% of the fixtures. Lens
doors should be provided for 20% of the fixtures.
Four For Induction
7Up / RC Cola in Vernon, CA had 35 mostly 400W HPS
hibays over a production area with serpentine conveyor belts. Access to the
hibays was so difficult that many of the hibays were left burned out. It cost
approximately $30,000 to erect custom scaffolds and planking in this 24/7
operation. To significantly reduce lighting maintenance costs, each HID hibay
was replaced with a dual 150W induction lamp hibay. Lamp life is more than
quadrupled, but fixtures may have to be cleaned before lamps burn out. If that
is necessary, hopefully a pole will work. In other areas HID hibays were
replaced with T5HO ones.
Several food companies have converted to induction
in their large freezers in distribution centers and in grocery stores. If you
have ever had to replace lamps and ballasts in a heavy parka with thin gloves
on a lift above food, you would want to do it as infrequently as possible. Just
dropping a lamp, which breaks, can mean tossing out pallets of food.
The Waste Isolation Pilot Plant (WIPP) is a DOE
low level radioactive waste disposal facility near Carlsbad, NM. It had 400W
HPS hibays. Light quality was not good. With the warm up and restrike times the
lights were left on from Monday morning to Friday night. Having to shut down
areas to allow lamps and ballasts to be replaced is very expensive. Plus
expensive boom lifts are required for some locations that do not allow straight
up access. Most of these HPS hibays have been replaced one for one with new
hibays that have two 150W induction lamps and ballasts. The three major
benefits are fixture wattage reduction from about 465 to 314, burn time
significantly reduced because of instant on, and probably most important,
minimum projected maintenance for next 10 to 15 years. Lawrence Berkeley
National Laboratory provided additional design/feedback/assistance and pre and
post metering. The simple payback is 3.1 years including maintenance savings.
A multi-level parking garage for a hospital had
175W standard MH ceiling cone fixtures. The hospital would test its back up
generator once a week. The MH’s long warm and restrike times caused problems
because of darkness. Not enough of the fixtures had quartz back ups, plus they
seemed to keep burning out. The MH lamps were rated for 10,000 hours. The labor
rate is quite high, because it is union. Including improving the lighting,
energy savings and reduced maintenance costs, it was cost effective to replace
these fixtures with similar ones that have 165W induction. Now there is instant
on. The wattage was reduced from 210 to 165, and lamp life was increased ten
fold. Since induction lasts so long, if the fixtures are not designed properly,
they will need to be cleaned every 25,000 or 50,000 hours, which defeats one of
the main benefits of induction. There are sealed fixtures designed specifically
for induction that are more than sealed and gasketed. They really do not let
dirt in.
Moscone Convention Center
San Francisco,CA
The best solution does not have to be either HID
or fluorescent. The best solution can incorporate the advantages of both.
A very good example is the south hall of this
convention center. It had fixture arrays consisting of a 400W standard MH
hibay, 1000W standard MH hibay, and two 500W incandescents. The 400 watter was
mainly used for show set ups and tear downs and self illuminated shows, like
when Lightfair was there. Both the 1000 and 400 watters were used for many shows.
The incandescents were also used for many shows, because of the much better
CRI. The incandescents were also used for emergency lighting, because of
instant on. Each of these fixture arrays were replaced with a rectangular
assembly that has one 400W PS MH lamp in a high performance dome and twelve
F54THOs with specular reflectors. These fixture assemblies look quite good. The
three circuits still allow for three levels of lighting. The T5HOs have instant
on and good enough color rendering, so incandescents are not needed.
Wrap Up
An appropriate ‘follow the money’ question for
this article follows. Does the hibay fixture manufacturer try to recommend the
best solution or just what it has and can sell? I highly respect manufacturers
and rep agencies that recommend other firms’ products when they know they are
better. Although they maybe lost a few sales, I have given them more total
sales over the years because of their and honesty and knowledge. Some of these
manufacturers have expanded their product lines to include different lighting
technologies in order to provide more best solutions.
I am trying to get at least one independent test
lab to set up a good procedure and set up to measure ballast case temperature
and light output from cold to hot ambient temperatures. That would provide
fixture manufacturers and customers invaluable information on the lighting
strategies and options, including up vents and lenses, for specific
applications.
The research for this article taught me some very
good lessons, including do not get lamp life information from ballast
companies. It would be helpful if lamp manufacturers and ballast manufacturers
worked closer together.
A final note is that I thank all of the lamp, ballast
and fixture manufacturers, lighting designers and retrofitters that helped me
with this article. If all of the names were listed, it would be a long
paragraph, and this article is already too long.
About the Author
Stan Walerczyk, LC, is Director of Lighting at Sun
Energy Solutions. He is a member of IESNA’s Energy Management Committee and
Retrofit/Upgrade Subcommittee. Most of Stan’s articles and links to other
articles are available at sunenergysolutionsllc.com.
For questions, comments and ideas for future topics please email lightingwizard@sbcglobal.net
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Downloads
This white paper:
High-bays: It's all about the details
(144K) Adobe PDF
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