Lighting Control Survey

In today’s economy and trends in building management, energy conservation is of utmost importance and is being made mandatory in design practices.  One of the major areas where energy conservation comes into play in design and building management is lighting control.  Many people would assume that having a light switch in a room is all the lighting control that is needed; however, ASHREA 90.1 (Energy Standard Code for Commercial Buildings) and the current IECC (International Energy Conservation Code) dictates that if a building is over 5000 sq. ft., it is mandatory that the building be equipped with a means to automatically shut off all lights.  This post is intended to describe a few options that customers have in providing this control.

Time Scheduling Devices

One method that the Energy Code approves as an acceptable solution is Time-Scheduling Devices.  There are several applications where timers can come into play, one being in-wall timers.   An in-wall timer can essentially replace a lighting switch in a room, and provide a means to turn the lights off in a space based on an interval selected by the user.  These devices are a viable option in retrofit applications, or in buildings where room usage is diverse.  There are a wide variety of in-wall timers (pictured below are a few).

Spring Wound Timer 7-Day Programmable Switches 7-Day Astro Timer
A                                B                              C

Spring-wound timers (A):   These mechanical dials keep the lights on for intervals of 1,2,4,6,8, or 12 hours as the user chooses.  ($15-$30 each)
Digital 7-day time switches (B):  These electronic timer switches can be pre-programmed for ON-OFF operation at regular intervals over the course of a week.  ($20-$50 each)
Astronomical timer (C):
This electronic timer controls fixtures based on sunrise, sunset, and time changes.  It is useful for exterior lighting and day-lighting control of interior spaces exposed to excessive sunlight. ($35-$50)

In buildings that may need less specific control of individual zones, a global timer device may be the answer.  A global timer is useful in buildings that completely shutdown at regular intervals during the week.  In design, or during the retrofit process, all lighting circuits would be fed through a lighting contactor or relay panel which would be controlled by a timer.  The user would set the timer at regular timing intervals which would cause all lighting in the building to be turned off and on automatically.  However, this method of global control requires that lighting be wired apart from other electrical devices in order to be cost effective.  Pictured below are a few options for global timers:

24 Hour Dial 7-Day Mechanical
D                                        E

 Astronomical Timer Digital Global Timers
F                                             G

24 Hour Dial Timer (D):   This timer can be used to control ON-OFF operations of light based on a repeating 24 hour schedule.  If the building opens and closes at the same times everyday, this timer would probably be ideal. (Note* the schedule is the same for all 7 days of the week)   ($80 – $140)
7 Day Dial Timer (E):  This timer can be used to control ON-OFF operations of light based on a repeating 7 day schedule.  If the building opens and closes at different times, or is closed on the weekends, this timer would probably by ideal.   ($180 – $240)
Astronomic Timer (F): Automatically adjusts the ON-OFF operation based on seasonal changes.  This timer would be useful for exterior lighting control.  ($300 – $1500)
Digital Timers (G):  In addition to the timers above, similar timers are offered electronically, without the mechanical dial.  ($400-$800)

 

Occupancy Sensing Devices

Another method that the Energy Code approves as an acceptable solution for global lighting                             control  is Occupancy Sensing Devices.  There are two technologies that are used in sensing occupancy, PIR (Passive Infrared), and Ultrasonic.

PIR sensors detect an occupant’s presence by sensing the heat emitted by moving people and the background heat.
Ultrasonic sensors detect a presence by sending out sound waves and measuring the time in which they return.
Dual Technology Sensors combine both PIR and Ultrasonic into one sensor for more accurate and controlled detection.

Ultrasonic are advantageous in places where line of sight is limited.  PIRs are useful when there are areas in which the owner would like to limit the detection range.  Dual technology sensors combine the advantages of the PIR and Ultrasonic, but are more expensive.  Pictured below are a few sensors available on today’s market:

Wall Switch Occ Sens Wall Mount Occ Sens
H                                                   I

Clg Mount Occ Sens Outdoor Occ Sens
J                                                      K

Wall Switch Sensors (H):   These sensors are available in PIR, Ultrasonic, and dual technology.  They are useful in retrofit applications, as they can directly replace an existing wall switch. ($50 – $175)
Wall Mounted Sensors (I):   Mounted to the wall, these sensors can be used in conjunction with existing switches or other lighting control devices.  They are also available in all the sensing technologies.  ($100 – $300)
Ceiling Mounted Sensors (J):  Mounted at the ceiling, these sensors can be used in conjunction with existing switches or other lighting control devices.  They are also available in all the sensing technologies.  ($100 – $300)
Outdoor Sensors (K): These sensors use motion to control exterior lighting.

 

Building Automation Systems

Another method that can be used for global control of lighting is a Building Automation System (BAS).  A signal from the BAS can be used to control the contactor or relay panel when the building is Occupied or Unoccupied.  Schedules can be set within the system to energize certain zones at certain times and to provide overrides for after hour uses.

In conclusion, by using some or all of these technologies, an owner can have more precise control over the lighting energy usage in his/her respective building.  Not only will these technologies meet the requirements of ASHREA 90.1 and the current IECC, but their use will provide the owner with lower energy usage bills. These technologies represent the most common forms of lighting control in our experience, but are in no way the only means to accomplishing control.  In later posts, we will discuss more advanced controlling methods and applications including dimming systems, bi-level dimming, and day-lighting controls.

Author: Ben Thornton – Mullinax Solutions Electrical Designer

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Lighting Technologies: T5 lamps vs. T8 lamps

As engineers, we strive to find ways of utilizing new technologies in our clients’ buildings that not only provide energy savings, but do so at a justifiable cost to the end user. Typically, our standard at Mullinax Solutions, Inc. is to push technologies that offer a 2-10 year payback, depending on the application and technology type. T5 fluorescent lamping is fairly new technology that is garnering attention in today’s energy conscious society. Below is a brief look at our experience and opinion on the T5 lamping technology.

T5 fluorescent lamps are advertised as the next step up in terms of energy savings when compared to the standard T8 fluorescent lamp. Standard T5 lamps are 28 watts and standard T8 lamps are 32 watts. On a per lamp basis, it’s a 12.5% energy savings. From that perspective alone, it sounds like an attractive alternative. However, there are a number of disadvantages to the T5 technology. T5 lamps are not the same length as the 48” T8 lamp. Instead, they are T5,T8 Picture2” shorter, at 46”. Building owners or facility managers who desire to use them will not be able to easily retrofit existing T8 fluorescent fixtures with T5 lamps. There are retrofit lighting trays available that close the 2” gap and allow for the usage of T5 lamps in T8 fixtures, but that is just one more element that increases the retrofit application costs. Speaking of costs, a standard T8 lamp will run you about $2 a lamp where a standard T5 lamp is about $8-10. That’s a fairly large cost increase to only net 4 watt savings on each lamp. In 2006, we fell victim to the promises of the T5 technology. While working on the electrical design for a new elementary school, a lighting representative sold the idea of T5 lighting fixtures to us, which at the time was a newer technology. Their sales brochures and limited data lead us to specify their new fixtures and lamps. After design documents were completed, much like the majority of new construction projects, the time for value engineering came. One of the first items on the list was the use of parabolic T8 fixtures instead of the T5 lighting fixtures. In considering the ramifications of this change, we decided to put the savings promised by the T5 fixtures to the test. An energy model was constructed and we compared the yearly savings of utilizing T5 fixtures vs. the standard equivalent of T8 fixtures. Our results netted the owner a payback on the initial cost of approximately 13 years. That figure in itself did not take into account any of the lamp replacement or maintenance which would also have been more expensive than that of the T8 lamped fixtures. Ultimately, we ended up changing all of the T5 fixtures to standard T8 fixtures.

The T5 lamping technology in itself, is not impractical by any means and it is not our intention to present it in this light. Nowadays, the minor energy savings does not justify the high initial costs, in our opinion. Furthermore, there are newer technologies today that further negate the advantages of T5 lamps, such as 28 watt T8 lamps, high lumen output T8 lamps, and LED tube lights. The majority of these alternatives stack up well when compared to T5 lamps, and would likely yield shorter paybacks to the end user. All negative criticism aside, there are certain applications where T5 lamps make sense. T5 high output lamps (at 54 watts each) are a great alternative for certain high ceiling applications (gymnasiums, retail, high ceiling coves, or industrial applications).

In conclusion, we believe that building owners and designers looking for energy savings in fluorescent applications should first consider the newer 28 watt T8 lamps, more efficient ballasts, and reliable lighting control schemes. T5 lamping and fixtures may be a modern option, but in our experience, there are more cost effective solutions in today’s market.

Author: Jeffrey Morgan, P.E. – Mullinax Solutions Project Manager