Bank Office Retrofit
My client had 2-foot by 4-foot T- 12 recessed fixtures with four
lamps behind a lens (see photo 1). Because these lamps were
phased out of production in 2014, the client had to make a change.
My routine retrofit would replace the four lamps and two T- 12
magnetic ballasts with two new T- 8 or T- 5 lamps and one ballast (see photo 2). I tested sample fixtures with T-8s in the client’s
office. Then, out of curiosity, I also installed a fixture with $25 snap-in LED strips next to the other test fixtures (photo 3).
Ultimately I chose the LEDs for the client’s project. Lighting
levels and light quality were improved and energy cut by 65–70%.
Although the facility’s operating hours totaled only 2,000 hours per
year, the LEDs had a good payback. (See costs at right.)
This LED retrofit doesn’t require recycling of the old sockets,
which may be near the end of their useful life anyway. You also
don’t need to fit new lamp holders into your old metal fixture since
the LED tubes don’t have the two pins at each end. The small magnets on the back of the LED attach easily to the back of the fixture.
Installation labor was less because this retrofit had only five steps:
1) Open lens
2) Cut all the wires
3) Remove the ballasts and
4) Snap in the two LED
5) Hardwire the tubes and
close the lens
That’s it! In the now vacant
space where the T- 12 ballasts
were attached, I had ample
room to contain the wire con-
nections and wire nuts to sat-
isfy our local electrical code.
Aesthetics, Risks and Downsides
For this project, most occupants preferred reading under the LED
fixture, probably because the color rendering index was higher (80
CRI) than that of the existing fluorescents (70 CRI).
Many LED strips/tubes come with either a frosted shield or clear
plastic. Frosted is best if the strip/tube is visible to the occupants
because it reduces the glare and the ability for someone to see the
LED sources, which can be too bright for many people. The clear
lens is useful for indirect lighting, when the light source is shielded
from occupant view.
LEDs are basically tiny computers that are more sensitive to voltage or current fluctuations than fluorescent lamps. During testing,
look for flicker when refrigerators, laser printers and other large
devices turn on.
These LEDs had a five-year, unconditional warranty. When they
fail, my client will need to replace two $25 LED tubes instead of two
$2 fluorescent lamps. However, if the retrofit economics are favorable today, they should be even more so in the future because LED
manufacturing costs are falling rapidly.
PHOTO 1: Existing four-lamp, T- 12 fixture
PHOTO 2: New two-lamp T- 8 fixture
New LED tubes
Existing fixture energy input: 144 watts per four-lamp fixture
LED fixture energy input:
18 watts per two-lamp fixture
LED tube material cost: $25 each
LED installation cost: $15 per fixture
Fixture rebate from local utility (your rebate may vary): $11
SAVINGS PER FIXTURE
= [(144 watts/fixture) – ( 36 watts/fixture)] x 2,000 hours/year
= 216 k Wh/year, which equals about $21.60 per year per fixture
in energy savings 10 cents/k Wh
When projecting your savings from a retrofit, you may want to include
savings from reduced labor and HVAC load. But as you can see below,
the payback is impressive without these factors.
INSTALLATION COSTS PER FIXTURE
= [($25/tube) x (2 tubes)] + ($15 installation) – ($11 rebate)
= $54 per fixture
= ($54/fixture)/($21.60/year in savings)
= 2.5 years