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Class II Div 2 Hazardous Environment
Occupancy Sensor
Project Statement
For Sensor Switch’s Approval
Joint ECE (Team 166) and ME (Team 26) Senior Design
ECE 4901/ME 4972
Fall 2012
Sponsored By:
Contact: David Behnke (Dave.Behnke@AcuityBrands.com)
Computer Engineering
Christopher Zannoni
Electrical Engineering
Christopher Zannoni
Joanne Hitchcock
Gledi Progonati
Engineering Physics
Russell Gee
Mechanical Engineering
Michael Gazda
James Fisher
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Statement of Need:
In 1987, Sensor Switch was founded and quickly became one of the industry leaders in
developing occupancy sensor products and technology for lighting control. Today, their sensors are used
throughout society in many commercial and non-residential facilities such as schools, hospitals,
warehouses and more. Many businesses look to Sensor Switch for their high-quality and cost-effective
sensor lighting products which are developed right in their headquarters of Wallingford, Connecticut.
Their wide array of sensors keeps them driving forward to create the most optimal products in today’s
market.
Sensor Switch has sponsored six senior design students from the University of Connecticut, all of
whom are either studying in the area of mechanical or electrical engineering. They have been given the
task of developing an occupancy sensor to work in a hazardous environment. Organizations such as the
Occupational Safety and Health Administration (OSHA) and the National Electric Manufacturers
Association (NEMA) have many strict safety requirements in these environments. Therefore, this project
will require lots of research and creative design. One of the main reasons that Sensor Switch has
presented this project to the Uconn Senior Design class is because of the up and coming demand for
sensors in this environment. Since Sensor Switch is a leading manufacturer in the occupancy sensor
field, they would like to develop a cost effective way to make this happen. The main goal of this project
is to have a product design and setup that will ultimately be marketable.
Preliminary Requirements:
Our design must comply with the codes for an occupancy sensor to be installed and run in a
Class II Division 2 location. These locations are defined as areas where combustible dusts exist (e.g. flour
mills, wood shops, etc.) but are not normally present. The setup of this product must be quick and easy
to keep the installation cost as low as possible. Along with the installation cost, the cost to manufacture
must be low to keep costs down.
Basic Limitations:
There are many limitations when working in a hazardous location with a Class II Division 2
designation. One main limitation is the amount of energy that exists in this type of environment due to
the potential of releasing that energy into a cloud of combustible dust, thereby igniting it. This energy
can come in many forms which include but are not limited to, circuit power in the form of watts, stored
inductive power, stored capacitive power, and heat. Electrical discharge is also prohibited in this type of
environment, for obvious reasons, as it could also ignite the combustible cloud of dust. The electrical
discharge that we have to prevent coming in contact with the hazardous environment is from the relay
that switches on or off the electrical component.
Another limitation is build up of this combustible dust as with greater concentrations comes
greater risk of ignition. Due to this, along with protecting the relay, protective enclosures will have to be
made for the sensor and/or the switch. However, the enclosures have to comply with Class II Division 2
standards as well.
The only driving force to install this sensor is that it will save the customer money. Thus, Sensor
Switch gave us a limit on cost. The sensor must cost less than the savings a customer would realize due
to the energy savings of the occupancy sensor being installed for three years or less; the calculations to
Initials of signing parties _____ , _____
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find this cost are presented in the next section. Due to the cost limitation, consideration has to be given
in the design for the enclosure’s assembly and installation.
Cost Specifications and Limitations
The supplied Sensor Switch CM 10 occupancy sensor can cover, on average, about 2400 square
feet1, with fluorescent light fixtures on average consuming about 1 watt per square foot2 we can
calculate that one sensor controls 2.4 kW worth of lights. With the average US cost per kWh of
$0.10/kWh in 20123 and using a figure of 3000 hours/year a facility operates4 one occupancy sensor
controls $720/year worth of electricity. Storage areas or warehouses would be a good example a
division 2 area5. According to a U.S. EPA Prediction6 a storage area is occupied 45%-80% of the time.
Using this percentage, one sensor would save $144-$396 per year in electricity costs if the lights were on
100% of the operating time without a sensor. Using the 3 year constraint mentioned earlier the cost of
the sensor, relay and installation, cannot be more than $432-$1188.
Verification Approach:
In order to confirm that our sensor and relay is designed correctly and can work in a Class II
Division 2 environment, testing will have to be performed. This approach will be determined by the
exact specifications that are drawn from the Class II Division 2 restrictions. One approach in testing is to
measure all the operating energy mentioned earlier (i.e. voltage, current, inductive power, etc.). In
conjunction with this approach is to verify that this sensor and relay with modifications comply with
current regulatory standards for a Class II Division 2 environment (i.e. measuring component spacing
and rigidity). Another approach that may be utilized is installing this sensor in a simulated Class II
Division 2 environment to see if combustion occurs.
End of Project Deliverables:
At the end of this project Sensor Switch should receive a prototype of a modified Sensor Switch
occupancy sensor and relay that we believe could pass inspection to work in a Class II Division 2
hazardous environment. Technical drawings and explanations of these modifications should accompany
the prototype. Due to cost and time constraints actual certification testing by a Nationally Recognized
1
http://www.sensorswitch.com/Onlineatalog.aspx?sn=cm%2010
http://www.gelighting.com/LightingWeb/na/resources/tools/lighting-assistant-toolkit/lighting-layoutestimator.jsp
3
http://www.eia.gov/electricity/monthly/pdf/epm.pdf
4
57hours/week from: http://infohouse.p2ric.org/ref/32/31316.pdf
2
5
Understanding Hazardous Area Sensing-Intrinsic Safety, handbook by Bob Svacina and Brad
Larson found at: http://www.parrinst.com/wp-content/uploads/downloads/2011/06/SvacinaLarson_Understanding-Hazardous-Area-Sensing_Intrinsic-Safety.pdf
6
Although the actual report could not be found, this number is used throughout the industry. Additionally we did
find a study by a member of the EPA ENERGY STAR Buildings Program, Bill VonNeida, who referenced that this
number. The report is found here: http://www.lrc.rpi.edu/resources/pdf/dorene1.pdf
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Testing Laboratory will not be preformed. Although instructions will be given to Sensor Switch on how to
do so.
Approvals:
Signatures below indicate that the signing party understands and approves of this entire
document. Along with signing below, initial in the footer of each page on the line provided.
Sensor Switch Approval:
___________________________________
Signature of David Behnke, Director of Engineering at Sensor Switch
Uconn Senior Design Team 166 and Team 26 Approval:
___________________________________
Signature of Christopher Zannoni, Team Leader for Uconn Senior Design Team 166 and Team 26