Turning Vanes: Necessary Component, or Efficiency Reduction Device?

The installation of turning vanes in HVAC ductwork is perhaps one of the greatest sources of contention between mechanical contractors and HVAC engineers. Why? Because many mechanical contractors believe that turning vanes can cause the ductwork to become less efficient by increasing the pressure drop in the system, as well as adding time and expense to the overall installation. This belief seems to be based in simple logic: when there is more surface area exposed to the airflow, the amount of friction will be increased, and the harder the fan must work to achieve the required airflows. In some cases when an HVAC system is having particular difficulty in supplying the required amounts of airflow to all zones, many mechanical contractors will recommend the removal of every other turning vane at each fitting in the system in order to “reduce the  friction” in the duct. This practice is a violation of SMACNA® turning vane spacing requirements, and has also been condemned by the Air Conditioning Contractors of America, because it decreases the uniformity of the airflow and increases the pressure drop in the system). The question is, does reality match up with popular belief?

THE FACTS:

When airflow changes direction in a duct that lacks turning vanes, the walls of the duct must absorb the sudden impact of the air in order to reorient the airflow to the direction desired. Turning vanes assist the airflow in making a smoother and more gradual change in direction, resulting in less of an impact, and thus less force transferred (as airflow velocity increases, this effect becomes more pronounced). While the turning vane surfaces do add a small amount of friction, the amount of energy lost to friction from the vanes is nothing compared to the energy lost in the impact resulting from the airflow taking an abrupt or significant change in direction. Figures 1.1 and 1.2 below illustrate the airflow resistance that occurs in a 90° square elbow with and without turning vanes.

 

Figure 1.1

 

 Figure 2.2

 From these figures, it can be seen that the elbow with the turning vanes is 800% more efficient than the same elbow without the vanes. If the owner desires a less expensive installation, the designer may specify radius elbows without turning vanes. A radius elbow without turning vanes is still highly efficient, and is much easier and cheaper to fabricate and install (spatial constraints must also be considered, as a smaller turning radius will decrease efficiency rapidly – minimum recommended turning radius ‘R’ without turning vanes is R=Width/2). Figure 1.3 below illustrates airflow in a radius elbow.

Figure 1.3 

Note also that the radius elbow without turning vanes and having a Radius/Width (R/W) ratio of 1.0 is only 28% less efficient than the elbow with turning vanes. If the radius is increased to R/W=1.5, it will only be 12% less efficient, and if it is increased to R/W=2.0, it will have the same efficiency as the same size elbow with turning vanes! In all cases it can be clearly seen that as the airflow changes direction more gradually, the fitting pressure drop decreases, and with it, the energy required by the system fan to supply the desired airflow volume.

THE CAVEATS:

 There are certain instances where turning vanes can cause an increase in pressure drop, and this article covers two such cases.

Case 1: Installation of turning vanes at the entrance to a branch duct.

The first case is when turning vanes are installed at the entrance to a duct branch. Some contractors, in an honest effort to reduce static pressure, install turning vanes or scoops at the entrance to a duct branch, as shown in Figure 2.1 below.

 

Figure 2.1

This configuration can cause large pressure losses, because the turning vanes disrupt the uniformity of airflow in the main duct, which in turn causes a high pressure drop at the fitting. Branches should be installed with a 45° entry or a radius branch fitting, as shown in Figure 2.3 below.

 

Figure 2.2

Figure 2.3

Note that the radius branch fitting is twice as efficient as the 45° entry fitting. While the radius branch fitting is slightly more expensive to fabricate, the installation cost is the same as the 45° entry fitting, and can greatly reduce pressure drop in systems with a high fitting count.

Case 2: Improper Turning Vane Alignment

The second example of turning vanes causing a pressure loss is where the vanes are not aligned with the ductwork properly, increasing air turbulence and creating a drop in pressure as seen in Figure 3.1 below.

 Figure 3.1

When the turning vanes are not properly aligned to run parallel with the sides of the ductwork at both the entrance and the exit of the vanes, the airflow will impact the sides of the duct and create turbulence. The effects of the improperly aligned turning vanes can range from mild to severe, and are determined by how far out of alignment the vanes are. Improper vane alignment occurs in many cases where ductwork is installed hastily or sloppily, and can be prevented by simply performing a final alignment check on all vanes prior to completing the installation. See Figure 3.2 below for an example of airflow in a duct with correctly aligned turning vanes.

 

Figure 3.2

 

THE CONCLUSION:

Turning vanes have been proven to be very valuable for reducing pressure losses and increasing system efficiency. Designers should always specify the highest efficiency fittings possible within the owner’s budget, to increase system efficiency at every available opportunity. Mechanical contractors should never take it upon themselves to add to or remove turning vanes from an engineer’s designs. Each system is designed to a specific total static pressure, and removing or adding turning vanes where they have not been accounted for in the engineer’s calculations will make the system function differently than intended. In a worst case scenario, the changes to the system may cause it to become incapable of supplying the required airflows to all zones.

Author: Miles D. Johnson, LEED® G.A., Mechanical Designer & LEED® Consultant

 

RESOURCES: 

 Sheet Metal and Air Conditioning Contractor’s National Association, Inc. (SMACNA).  HVAC Duct Construction Standards – Metal and Flexible. Second Edition, 1995. Sheet Metal and Air Conditioning Contractor’s National Association, Inc. (SMACNA): 1998. Print.

Air Conditioning Contractors of America. Manual Q – Commercial Low Pressure, Low Velocity Duct System Design. Air Conditioning Contractors of America: 1990. Print.

American Society of Heating, Refrigeration, and Air-Conditioning Engineers, Inc. (ASHRAE). 2008 ASHRAE Handbook – HVAC Systems and Equipment. I-P Edition, 2008. American Society of Heating, Refrigeration, and Air-Conditioning Engineers, Inc.: 2008. Print.

American Society of Heating, Refrigeration, and Air-Conditioning Engineers, Inc. (ASHRAE). 2009 ASHRAE Handbook – Fundamentals. Inch-Pound Edition, 2009. American Society of Heating, Refrigeration, and Air-Conditioning Engineers, Inc.: 2009. Print.

Be an Informed LEED-er

Requirements To Consider When Preparing to LEED® Certify An Existing Building

The U.S. Green Building Council® (USGBC®) LEED for Existing Buildings Operations and Maintenance® is a program designed to recognize and rank buildings that have already been constructed that make great strides towards becoming environmentally friendly. For many buildings, this program begins where LEED for New Construction® ends, but the USGBC® also uses this program to recognize existing buildings that have not already been certified under the LEED for New Construction® program.

This article examines the prerequisites in LEED for Existing Buildings Operations and Maintenance® that have the potential to have large costs associated with them. The ultimate goal of this article is to assist with determining an accurate cost baseline for making buildings as environmentally friendly as possible.

Water Efficiency Prerequisite 1: Minimum Indoor Plumbing Fixture & Fitting Efficiency*

Prerequisite Summary: Establish a calculated Baseline, and a calculated fixture water usage, using LEED® guidelines (this can be determined through a calculation template that can be downloaded from the USGBC® website). Reduce calculated building fixture water usage to within 120% of this calculated Baseline (if the building fixtures were installed in or after 1993) or 160% of this calculated baseline (if the building fixtures were installed before 1993).

Consider: LEED® uses the International Plumbing Code® 2006 Edition to calculate the usage baseline. This prerequisite does not require that all of a building’s fixture water usage ratings must meet code, or be within 120% (or 160%) of it; the fixture usage rates are weighted, based on a usage profile defined by all the different groups of people using a building (such as visitors, students, residents, full-time employees, etc) that have access to each of these fixtures. Thus, a fixture that is installed in a publicly accessible location in a building with a high number of daily visitors will count more than the exact same fixture installed in a private office bathroom in the same building.

For many buildings (particularly buildings built after 1993), meeting this prerequisite may be as simple as installing new faucet aerators to meet the 0.5 gallon-per-minute (gpm) water flow rate required by code. Other, older buildings might require the installation of new low-flow flushometers for flush valve water closets or urinals. Unfortunately, most of the pre-1993 buildings face a much tougher road to fulfilling this requirement in the form of having to install all-new water closets and urinals. Most of the older 3.0 gallons-per-flush (gpf) water closets are not compatible with low-flow flushometers, and thus both the porcelain and the flushometer must be replaced in order to meet the requirements for this prerequisite. Special considerations must be taken for wall-hung fixtures, since replacement fixtures that are compatible with the existing bracket and connection locations must be selected if piping modifications and wall reconstruction are to be avoided. The total cost for this operation can run into the tens of thousands of dollars very quickly. The good news is that in many cases buildings that replace the older 3.0 or 3.5 gpf fixtures with the newer low-flow fixtures are likely to achieve payback from water savings in less than 10 years (this will depend entirely on fixture usage volume).

The Conclusion: When considering whether to try to get a building LEED® certified, it must be considered beforehand whether all-new bathroom fixtures must be installed before the building can qualify to begin earning points, and, if so, if the project budget can afford it. At an average installed rate of anywhere from $600 to $1000 per water closet or urinal (including labor), this prerequisite has the potential to eat up the entire budget for a LEED® project on its own. Payback periods should also be taken into consideration, and can soften the impact of a high-cost installation.

Energy & Atmosphere Prerequisite 2: Minimum Energy Efficiency Performance*

 Prerequisite Summary: The building must achieve either a 69 ENERGY STAR® rating, or have an Energy Usage Index (EUI) 19% lower than the average building of its type (the ENERGY STAR® rating for any building is based on that building’s EUI).

Consider: The true focus of this credit is on reducing the building’s Greenhouse Gas Emissions (GHG). LEED® considers conventional or “high-impact” electricity (non-renewable fuel source or high-impact hydroelectric) to be the most polluting energy on the market. This causes a building that receives 100% of its power from conventionally-generated electricity to have a much harder time satisfying this prerequisite than one with alternatively fueled space heating, water heating, etc. Table 1 below demonstrates the EUI advantage of using alternative fuels by comparing the EUIs of two buildings, one powered by conventional electricity alone, the other powered by a combination of conventional electricity and natural gas.

 Table 1Table 1: Energy Usage Index Comparisons

 

 

 

 

 

 

 

 

It is obvious that a building using alternative low-emissions fuel for at least part of its processes has a significant advantage over a building using conventional electricity. If the total energy usage in a building is difficult to reduce (because of process equipment required, etc.), some ways to reduce GHG emissions and improve a building’s EUI are as follows:

  1. Swap out electric-powered appliances/equipment for their natural gas (or other alternative low-emissions fuel) counterparts; e.g., swap electric water heaters for gas water heaters, electric strip-heaters for natural gas or propane furnaces, etc. Depending on what you replace, this can be quite expensive, and one must also consider the ongoing costs of the alternative fuel desired, when compared to those of electricity. Check to make sure your building has a natural gas service line installed, as well. Installing a new gas service line can be very expensive.
  2. Install on-site renewable power generation (solar, wind, etc.). All power that is generated on-site via renewable sources is not counted in the building’s total energy usage profile. This option also has the benefit of earning extra credits under Energy & Atmosphere Credit 4. Something to consider, however, is that (with government tax credits and grants) this option only sees payback after about 25 years at the time of this writing (this calculation is based on a municipal electricity cost rate of $0.16 per kWh). Most of the larger building are able to purchase electricity at a much lower rate (average rate is $0.08 per kWh for the buildings audited by Mullinax Solutions), and thus will see even longer payback periods of 45 years or more. Payback from the installation of on-site renewable power generation is essentially non-existent, in almost every case Mullinax Solutions has examined.
  3. Install energy meters on all process equipment. LEED® does not require process energy (computers, data centers, large kitchen equipment, etc.) to be included in energy usage index calculations; thus, all energy used to power process equipment may be subtracted from the total building power. Depending how much of a building’s total energy usage is due to process equipment, the project might be able to meet this prerequisite by using this method alone. This is typically the least expensive option, and is typically the easiest to implement as well.

The Conclusion: This credit has the potential to be the least, or most, expensive of all the prerequisites, depending on what needs to be upgraded or changed. Also, keep in mind that ENERGY STAR® uses a 1-year benchmark to give a rating, so once new energy-saving procedures have been implemented, it will take one full year for the savings to be fully reflected in the ENERGY STAR® rating or EUI. This will cause the project to be delayed for a minimum of one year.

Energy & Atmosphere Prerequisite 3: Fundamental Refrigerant Management*

Prerequisite Summary: Ensure that all HVAC equipment in the building contains no chlorofluorocarbon (CFC) refrigerants.

Consider: Newer buildings should have no problem with this prerequisite, since CFCs have not been in production for some time now, but older buildings (particularly those with chilled water systems) may have an older chiller that uses CFC-11 or CFC-114. Older restaurants may also have some issues, since many models of older walk-in coolers make use of CFC-12. Although some HVAC equipment may be able to be converted to use the more environmentally friendly hydro-chlorofluorocarbon (HCFC) refrigerants, many cannot be converted, and would have to be replaced before the building would be eligible to receive LEED® certification. The required modifications to equipment can range from relatively inexpensive and simple (such as installing a new thermal expansion valve, discharging old refrigerant, and recharging with an approved alternative refrigerant) to expensive and possibly very complex (such as purchasing a new walk-in cooler, or installing a new chiller).

The Conclusion: The nameplates and tags on all refrigeration equipment should be examined to determine what kind of refrigerant it uses. This will assist in determining what (if any) equipment needs to be retrofitted or replaced. Equipment manufacturers will be able to assist with supplying retrofit kits for equipment that can be modified to accept HCFC refrigerants. Lists of the various CFC refrigerants that have been banned can be found on the EPA® website at http://www.epa.gov/ozone/science/ods/index.html.

Indoor Environmental Quality Prerequisite 1: Minimum Indoor Air Quality Performance*

Prerequisite Summary: Meet the outside air supply requirements set forth in ASHRAE® 62.1-2007.

Consider: In order to increase the maximum outside air supply capacity of a typical unit, it must be equipped with enthalpy wheels, reheat systems, etc. Such a system is commonly known as an Energy Recovery Ventilator (ERV), and is usually capable of properly conditioning anywhere from 55%-100% outside air by total volume. 

The Conclusion: Unfortunately, installing a brand new ERV can be quite expensive, so it must be carefully examined whether a building meets (or can be easily configured to meet) ASHRAE® outside air requirements with its existing equipment and system configuration. If the system does not meet ASHRAE® requirements with its existing equipment or system configuration, the best-case scenario would consist of a simple rebalance of the airflow distribution and unit settings by a certified test and balance technician in order to supply the proper amount of outside air to each zone. The worst-case scenario would require installation of a new HVAC unit (or even possibly a redesign of the HVAC system) before the building could submitted for LEED® certification. While LEED® does provide an alternative for buildings that cannot provide the amount of outside air required by ASHRAE® 62.1-2007 with their current equipment, the alternative requirement (10 CFM per occupant at all times) can be just as difficult to achieve. This is particularly true for equipment serving areas (such as office buildings) where ASHRAE® outside air supply rates for occupants are significantly lower than 10 CFM per occupant.

An alternative approach to this prerequisite might be to first set the outside airflows to satisfy the ASHRAE® space-only requirements (not including occupant outside air supply rates), and then install CO2 sensors to monitor the ambient air conditions and modulate the outside air supply to satisfy the occupants with outside air on an on-demand basis (a Credit Interpretation Request may need to be submitted to LEED® to obtain approval for this approach). This approach will require that a digital control system be installed, and thus would be most suitable for buildings with an existing Building Automation System (BAS); installing and programming a new BAS for an average building can be very costly. In all cases, proper thought must be put into how this prerequisite will be met, because it has the potential to cost the project a significant portion of its budget. 

Concluding Remarks:

Mullinax Solutions strongly believes in the principles of LEED®. Every building is unique in its purpose, design, and construction, and will need to be evaluated independently of all other buildings. Many buildings will meet the prerequisites examined in this article with no additional work necessary, while others will need modifications that will require anything from simple and inexpensive modifications to complex and costly replacements. One thing, however, is for certain: following these guidelines to environmentally responsible leadership, the people of our nation will become less energy-dependent, will learn to be better stewards of our valuable natural resources, and they will begin to secure a cleaner and healthier environment for our future generations.

Author: Miles D. Johnson, LEED® G.A., Mechanical Designer & LEED® Consultant

 

LEED® and the USGBC® logo are registered trademarks of the U.S. Green Building Council, and are used by permission.

*All prerequisites and credits mentioned in this article have been developed by the U.S. Green Building Council (USGBC), and remain the sole property of the USGBC and its affiliated

RESOURCES:

The US Green Building Council. www.usgbc.org.

The US Green Building Council. Various. Web, October 14, 2009.

The US Green Building Council. LEED Reference Guide for Green Building Operations and Maintenance. 2009 Edition.The US Green Building Council: 2009. Print. 

The Environmental Protection Agency (EPA). www.epa.gov.

The United States Federal Government

August 28, 2009. Web, October 14, 2009.

The WEBstraunt Store. www.Webstrauntstore.com.

The WEBstraunt Store Food Service & Supply Company

October 14, 2009. Web, October 14, 2009.

Tank-type vs. Tankless Water Heaters

Tankless water heaters seem to be the new fad these days. Save on your energy bills! Enjoy your endless supply of hot water! This technology’s claims are attractive, but what are the disadvantages to tankless water heaters and how do they really stack up to the more traditional tank-type water heaters on today’s market? In this post, we will explore the answers to these questions.

Summary of the Technologies:Tank-type Heater

Tankless Water Heater

 

 

 

 

 

 

 

  

                          1.                                                        2.

1. Tank-type Water Heater – Tank type water heaters have been the industry standard for decades. Its components are similar to tankless water heaters, aside from the fact that it has a storage tank where it keeps a reservoir of hot water on hand. Operationally, tank type water heaters maintain a certain hot water temperature (typically 110-140 degrees farenheit) within the storage tank. As such, its burner and/or heating element is cycled on and off regularly, as needed to maintain the storage water’s hot water temperature.

2. Tankless  Water Heater – A tankless water heater is just that: tankless. Typically, its a smaller wall mounted rectangular box that houses a burner or heating element, controls, and internal piping. Operationally, the water heater only fires when there’s a need for hot water. As water flows through the heater to meet the demand, a water flow sensor activates and fires the burner or heating element.

Advantages/Disadvantages:Each technology has its respective advantages and disadvantages. Realization of the advantages depends largely upon the application of the respective technologies. It’s important to note that the advantages and disadvantages vary depending on the fuel sources as well (natural gas or electric).

1. Tank-type Water Heater

Advantages:

  • Low first cost (both gas & elec) – approx. $400 – $550 for a typical unit sized for a single dwelling.
  • Smaller gas/power requirements (more typical of what has been the standard for decades).
  • Easily adapted to re-circulation applications.
  • Easily adapted to solar pre-heat applications. This technology is becoming very popular in today’s society. A tank type water heater is a required element in the majority of these applications. Currently, tankless water heaters are not used in solar pre-heat applications.

Disadvantages:

  • Energy is used periodically 24/7 to keep storage tank temperature consistent.
  • Larger footprint than a tankless water heater. This becomes a significant issue when the hot water demand is high, as additional storage tanks may be required to meet that demand.
  • Limited hot water supply. You can supply only as much hot water as your storage capacity and burner/heating element recovery capability allow.

2. Tankless Water heater

Advantages:

  • Energy is not used until a demand is present.
  • Smaller footprint than tank-type water heaters, saves floorspace.
  • Unlimited hot water supply, as long as fuel is present (electric/gas).
  • No risk of a broken or ruptured tank, which could lead to flood damage.

Disadvantages:

  • High first cost (both gas & elec) – approx. $1000 – $1200 for a typical unit sized for a single dwelling.
  • Larger gas/power requirements (in terms of demand), which drives up installation costs and can have a significant impact on building service sizes.
  • Re-circulation applications are not easily implemented. It usually involves the addition of a small tank-type heater in the circulation loop to maintain the re-circ loop temperature when the tankless water heater is not firing. It can also be accomplished with a special pump. Either way, the assembly becomes more expensive and complex for a contractor to install.
  • Limited hot water flow, depending on the unit size. Most manufacturers offer units supplying up to about 7-9 gallons per minute. Once the demand gets above that, the practice is to add more of the same water heater in parallel. It is critical that these systems be sized properly.
  • Wastes more water than a tank-type water heater. When the demand for hot water is there, water begins to flow through the tankless water heater. The tankless must then heat up the cold water at that moment. The result is more water down the drain while you wait for the water to heat up to the desired temperature. This can be alleviated with a demand type hot water pump, but that is an added expense on top of the already increased first cost of the tankless water heater.

Tankless and Tank-type Water Heater Lime Buildup:

Lime buildup is a problem in water heaters, especially in environments with hard water. The buildup occurs over time, and usually originates at the areas where heat is applied. The result of this buildup is a loss of efficiency of the respective water heater technology, be it tankless or tank-type. I have seen some tankless water heater manufacturers claim that an advantage of their units is that they are less susceptable to lime buildup. I did not include this in advantages/disadvantages because for typical tankless water heaters, it’s just not true. Lime buildup can be avoided if the velocity of the water is great enough, but with typical tankless water heaters, the velocity is not such. PM Engineer® did an in-depth analysis of tankless water heaters vs. tank-type water heaters. Their results can be found here. In their analysis, they found that lime built up on the lines inside the tankless water heaters at a faster rate than it would in a storage tank water heater. I won’t go as far as saying that tank type water heaters are less susceptable to lime buildup, only that both technologies suffer from it. There are special water heaters that are designed to minimize lime buildup, but for the purposes of this analysis, I won’t be taking those into account.

Conclusion:

As originally stated, tankless water heaters and tank-type water heaters each have their share of advantages and disadvantages. In my experience, a tankless water heater is not a 1:1 replacement solution for a traditional tank-type water heater, although it’s often advertised as that. There are electrical/gas service implications, as well as usage profiles that have to align well with the operation of a tankless water heater. Applications that lend themselves to tankless water heaters in terms of their savings and application are facilites that require large volume, constant flow (i.e. laundromats, car washes, some commercial restaurants), have limited floor space, or are located remotely (i.e. remote building that is used infrequently).  Tank-type water heaters have come a long way. They are better insulated than they’ve ever been, resulting in less heat and energy loss, and some of the newer technologies help alleviate some of the disadvantages of past designs. I encourage designers, builders, and facility owners to familiarize themselves with the facts about the various water heater technologies before making a decision that could cost them in the long run if the specific project parameters and application are not taken into account.

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

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

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

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Hello all and welcome to “The Building Engineer”. This blog was established by the engineering staff of Mullinax Solutions, Inc. and is intended to serve as a platform to inform clientele and general web browsers of the advantages and disadvantages of today’s building technologies and practices. We hope that you find our blog informative and beneficial and welcome any expertise or feedback you have on our topics.

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