lightfair international - Illuminating Engineering Society

210 to 101. Photocells were also
installed for the three fixtures closest
to sunlight. Maintenance will be
reduced because these biax-T5s are
rated for 20,000 hours, compared to
10,000 hours for the 175 W metal
halide lamps. This is a big plus
because these fixtures have tricky
access. Three replacement bi-axial
lamps cost slightly more than one
175 W metal halide lamp.
Eastmont Mall, Oakland, CA
At Eastmont Mall, interior areas
with recessed cans were replaced
with retrofit cans. Interior cans
got 42 W triple-loop electronically
ballasted fluorescent lamps rather
than 50 W metal halide. Other locations
got units with 2–42 W triple
loop lamps over 100 W metal halide.
Kaiser Hospital, Walnut Creek, CA
The exterior roof maintenance
area had 100 W mercury vapor
wall packs. Owing to warm-up time
and restrike time, these fixtures
were left on all night, every night.
Each fixture was replaced with a
flood fixture with two F17T8 835s
and electronic ballast. Wattage
was reduced from 118 to 33. A
timer switch was also installed,
so lights are only on when engineering
staff is present.
It should be noted that across
the board owners and occupants
have been extremely satisfied with
lumen quantity and quality, and
energy savings.
Should you eliminate HID
It definitely should be considered
as an option.
The best light source is only part
of the problem. The other part is
the fixture’s job of getting as much
of the available light out of the fixture
and directing it where needed.
There are some very well designed
HID fixtures and some that are
incredibly mediocre. The full range
is also true for fluorescent fixtures.
Since HID is more of a point source
than fluorescent, it is easier to
focus the light, but some fluorescent
fixtures will do a reasonably
good job. For fluorescent fixtures,
enhanced aluminum with 95 percent
reflectivity often works best
for high fixture mountings, while
90–92 percent white reflectors
tend to work best for lower fixture
mountings.
In lighting, as in other endeavors,
it is important to “follow the
money.” If a sales person or manufacturer’s
representative works for
an HID fixture company, do not be
surprised if that person pushes HID.
They may not even be aware what
the new fluorescent systems can
do. Even internal battles in the
major lamp manufacturing companies
occur when the HID division
does not want to lose market share
to the fluorescent division.
With
the substantial
inconsistency
between photopic
lumens and
general perception,
we no longer
base lighting
recommendations
on just
photopic lumens
or light meter
measurements.
We have endeavored to remain
independent, not linked to any
technology or manufacturer. We
still recommend some HID, usually
for high wattage pole fixtures, wall
packs, and floods for exterior applications.
For these applications
pulse start metal halide is the
preferred choice. HID is usually
better for cold ambient temperatures.
Also, fluorescents cannot
easily compete with the PAR metal
halide lamps used for accent and
display lighting.
Additional Notes
Task modified lumens are not
easily measured with a light meter,
and are not yet accepted by the
IESNA. If you require legal protection,
meeting IESNA recommended
light levels is still advised.
If S/P ratios are useful to you,
request the lamp manufacturer of
your choice provide up-to-date
ratios for established and new
lamps.
Reference
1. Berman, S. and Liebel, B.
1996. Essay by Invitation. LD+A 26
(no. 11): 11–17.
The Authors: Stan Walerczyk and
Brooks Sheifer are vice presidents
of Alamo Lighting, where they
focus on turn-key energy efficient
lighting upgrades, consulting and
new construction design.
This article was previously
published in a condensed version
in Energy User News, September
1998, as “Comparing Fluorescent
and HID.”
Authors’ Note: We applaud LD+A
for providing a forum of controversy
as may appear in “Essay by Invitation.”
From the perspective of designers
who repeatedly specify HID and
fixture manufacturers who are heavily
invested, our findings may seem to
encroach on sacred turf. In the spirit
of free speech, LD+A has permitted
diverse ideas at the risk of infuriating
readers and advertisers.
We design and manage the retrofit
of millions of square feet annually.
Our methods emanate from the
trenches, through trial and error. We
are independent of any lamp, ballast,
or luminaire manufacturer.
There are many applications
where point source HID outshine
fluorescent. In other settings fluorescent
enjoys an advantage, even
over pulse-start metal halide. Our
intention is to simply explain the
merits and drawbacks of each.
Please be aware these findings
do not reflect the opinions of LD+A
or the IESNA.
LD+A/April 1999 9