United States
Environmental Protection
Agency
EPA430-F-96-052
October 1996
APPLICATION PROFILE
Occupancy Sensor Control in
Educational Spaces
Cincinnati, Ohio
Director of Facilities
Management: Jim Tucker
Contractor:
In-House
Utility:
Cincinnati Gas & Electric
TYPICAL APPLICATIONS
| Classrooms
| Lecture Halls
I Faculty Offices
I Library Stacks
| Restrooms
| Study Rooms
Recycled/Recyclable Printed with
vegetable oil based ink on paper that
contains at least 50% recycled fiber
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For help in starting an
occupancy sensor
control program,
contact a Green Lights
Lighting Management
Company Ally. Fora
list of these
companies, call the
Green Lights Hotline
at i-888-STAR-YES.
OCCUPANCY SENSORS IN
CLASSROOMS
Automatic lighting controls are an
essential component of an aggressive
and profitable energy management
program in educational facilities. Occu-
pancy sensors minimize the unneces-
sary lighting of vacant spaces to save
energy both during and after normal
business hours. Occupancy sensors
not only eliminate wasted lighting in
infrequently or unpredictably occupied
spaces during the day, but also prevent
runaway lighting operation at night by
eliminating reliance on occupants,
cleaning or security crews to manually
turn the lights off.
Occupancy sensors are suitable for
a wide range of lighting applications.
Sensors are most commonly mounted
in switch locations, combinations of
wall/corner surfaces, or ceiling
mounted above the center of a space.
Two motion-sensing strategies are
prominent; passive-infrared and ultra-
sonic technologies. Infrared sensors
detect body heat and require a direct
"line-of-sight" to occupant motion. Ul-
trasonic sensors emit and receive ultra
high-frequency sound waves well
above the range of human hearing.
They are better at recognizing motion
hidden from the sensor's direct view.
Some occupancy sensors are also
equipped with an integral photocell to
combine daylighting control with occu-
pancy control.
The specification, placement and
installation of occupancy sensors
should be done by experienced, knowl-
edgeable personnel. For a successful
application, proper calibration is a
must. Most sensors have adjustments
for sensitivity to ensure that occupant
motion is detected while filtering out
extraneous signals, and for time delay
to minimize excessive on/off cycling.
Sensors equipped with photocells also
have a light level setpoint adjustment
to turn lights off in a room when ad-
equate daylight is available. Trial in-
stallations are an excellent way to ad-
dress many of these issues.
Benefits
Complimentary Technology: Occu-
pancy sensors make an excellent
compliment to other lighting sys-
tem upgrades. They are compat-
ible with many technologies, and
they offer additional HVAC savings
and security advantages.
Peak Demand Period Opportuni-
ties: Occupancy sensors are the
only effective control strategy for
reducing lighting run-time during
business hours.
Immediate and Flexible Savings:
A properly commissioned occu-
pancy sensor can immediately
adapt to many workplace variables
while remaining a low-mainte-
nance component of lighting sys-
tems.
Issues
False Switching: Occupant anxi-
eties related to false switching can
be addressed through careful
specification of detection strategy,
installation position, and post-in-
stallation commissioning.
Lamp Life: Although fluorescent
lamp life is reduced by frequent
switching, the overall reduction in
operating hours can extend the
calender life for lamps.
Energy, Demand, and $ Savings:
Demand and energy rate structures
must be considered to ensure that
anticipated energy savings yield
cost savings.
Occupant Education: An occupant
notification and education pro-
gram is an essential component to
foster user acceptance and ensure
lasting savings.
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CASE STUDY
Lindner Hall
The University of Cincinnati (DC)
installed occupancy sensors through-
out Lindner Hall, a classroom building,
as part of their intelligent building plan.
The goal of the plan was to reduce
energy consumption and emissions
while giving occupants greater control
and more comfort. They chose occu-
pancy sensors for Lindner Hall because
they did not affect light output while
the space is occupied, but reduced the
total energy consumption.
One dual-technology sensor (with
both passive infrared and ultrasonic
technologies) was placed in each
classroom. According to Jim Tucker, the
Director of Facilities Management,
Lindner Hall was the "logical trial site
because of its high usage." The
sensors are integrated into the direct
digital control (DDC) system, which
provides control of the HVAC system. In
addition to controlling the lights, each
room's sensor also cuts air flows to a
minimum when the room is unoccu-
pied. The DDC system has an override
capability that allows the ventilation
system to remain active based on
scheduled room occupancy. The
University of Cincinnati is pleased with
the success of the occupancy sensor
trial and would use the technology
again because "it's an efficient and
economical approach to providing a
comfortable environment within our
facilities."
Facility Information
87,230 square feet
675 seats in a lecture hall
i occupancy sensor per lecture hall
4,160 hours per year (base case)
2,660 hours per year (upgrade)
Equipment Information
Watt Stopper Dual-Technology, Ceiling-
Mounted Sensor
Watt Stopper Power and Slave Packs
We knew that installing
dual-technology occupancy
sensors would enhance the
energy efficiency we were
already reaping through our
//
DDC system.
-Jim Tucker
Director of Facilities
Management
Comparison of Lighting Hours With and Without an Occupancy Sensor
ON
M
s
i
OFF
Lights off (savings)
[ ] Lights on
i r
— .
Midnight
8:30 AM
Noon
6:00 PM
10:00 PM Midnight
Time of Day(Hr)
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WILL IT WORK FOR YOU?
Use the following graph to estimate the cost effectiveness of installing occupancy
sensors in your facility.
I Determine your average electricity rate. For our example, the average electric-
ity rate is 8 cents per kilowatt-hour.
I Draw a vertical line from this point until it intersects the line that represents the
estimated percentage reduction in lighting operating hours due to the installa-
tion of occupancy sensors. For our example, it is estimated that a 20%
reduction in operating hours will result due to the installation of occupancy
sensors.
I Draw a horizontal line from this point until it intersects the vertical axis that
measures the after-tax internal rate of return. Our sample upgrade earns an
internal rate of return of 32 percent.
OPEN AREA - CEILING-MOUNTED SENSOR
80
10% Reduction
in Operating Hours
45 6 7 8 9 10 11 12
Electricity Rate (cents/kWh)
The Green Lights Program offers 2-
day Lighting Upgrade Workshops,
Application Profile brochures, and
other technical support services to
assist program participants in
applying cost-saving lighting
strategies. For more information,
call the Green Lights Hotline at
l-888-STAR-YES.
Graph
Assumptions
Ceiling-mounted sensor control-
ling 10 fixtures, $190 installed cost.
3,500 hr/yr uncontrolled system
operation.
Fixtures are 3-lamp F32T8 with
electronic ballasts @ 91 watts/
fixture. Maintenance budget
assumes a group maintenance
program.
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