Why Ductwork Contributes to AC Noise

Why Ductwork Contributes to AC Noise

ceiling fan

The Role of Ductwork in Air Conditioning Systems



The role of ductwork in air conditioning systems is integral to the effective distribution of cooled air throughout a building. However, one often overlooked aspect of this crucial component is how it contributes to noise within an air conditioning system. Understanding why ductwork can be a source of noise requires an examination of its design, material composition, and installation.

Firstly, the design and layout of ductwork play a significant role in noise production. Unusual odors from your vents might indicate a problem that requires HVAC Repair AC repair to enhance your air cooling efficiency and comfort. Ducts are responsible for channeling airflow from the central cooling unit to various parts of a building. If these pathways are poorly designed or improperly sized, they can create turbulence as air moves through them. Turbulence typically results from sharp bends or abrupt changes in duct size, which disrupt smooth airflow and generate sound waves that manifest as noise. Proper design planning that includes gradual transitions and adequate sizing can significantly mitigate this issue.

The material composition of ductwork also contributes to noise levels within an AC system. Many ducts are made from sheet metal due to its durability and cost-effectiveness. However, metal naturally amplifies vibrations caused by moving air, especially at high speeds or pressures common in larger systems. These vibrations resonate through the ducts' thin walls, producing noticeable humming or rattling sounds. Using alternative materials like fiberglass-lined ducts or applying insulation can dampen these vibrations and reduce associated noises.

Installation quality further influences the extent to which ductwork contributes to AC noise. Loose connections between sections of ducts can lead to leaks where air escapes noisily into unconditioned spaces such as attics or basements before reaching intended areas. Additionally, inadequately secured ducts might shift slightly over time due to pressure changes during operation, causing popping sounds as they rub against structural elements like beams or joists.

Another factor worth considering is the impact of external factors on ductwork-related noise. For instance, debris accumulation inside ducts not only affects system efficiency but also creates blockages that increase pressure build-up and subsequent noisy operations when cleared by forceful airflow surges.

In conclusion, while essential for HVAC functionality by facilitating efficient temperature regulation indoors-ductworks' contribution towards unwanted acoustic disturbances cannot be ignored either! Addressing issues related directly back onto their origin: thoughtful designs accommodating sufficient space allowances alongside using appropriate materials coupled together with meticulous attention paid during initial setup stages will go long ways ensuring minimal disruptions occur later down line thus preserving peaceful environment everyone enjoys being part henceforth making entire experience pleasant rather than disruptive affair instead ultimately enhancing overall comfort provided via modern climate control solutions available today!

Common Sources of Noise in Ductwork



Ductwork is an essential component of any heating, ventilation, and air conditioning (HVAC) system. It functions as the circulatory pathway through which conditioned air is distributed throughout a building. However, one common issue associated with ductwork is noise. Understanding why ductwork contributes to AC noise requires exploring the various sources of noise within these systems.

Firstly, airflow turbulence is a significant contributor to ductwork noise. As air travels through the ducts, it encounters various obstacles such as bends, turns, and junctions that can cause the smooth flow of air to become turbulent. This turbulence results in increased friction against the walls of the ducts and creates a rumbling or whooshing sound.

Why Ductwork Contributes to AC Noise - ceiling fan

  1. garage
  2. automobile air conditioning
  3. air pollution
The speed at which air moves can also amplify this effect; higher speeds increase turbulence and consequently lead to louder noises.

Another source of noise in ductwork comes from expansion and contraction due to temperature changes. HVAC systems often cycle between heating and cooling modes, causing metal ducts to expand when heated and contract when cooled. This constant movement can lead to popping or banging sounds known as "oil-canning." These noises are particularly noticeable during transitions between operational modes but can occur anytime there are significant temperature fluctuations.

Vibration is another factor contributing to ductwork noise. Blowers or fans used in HVAC systems can transmit vibrations into the connected duct network. If ducts are not properly secured or if there are loose fittings, these vibrations can resonate throughout the system, producing humming or rattling sounds. Additionally, external factors such as footsteps on floors above or nearby machinery can introduce vibrations into ductwork.

Poor installation practices further exacerbate noise issues in duct systems. For instance, sharp turns or abrupt changes in duct size without proper transition pieces can create additional areas for turbulence and vibration-induced noise. Furthermore, inadequate insulation around ducts may allow more sound transmission into occupied spaces.

Finally, aging components within an HVAC system contribute significantly to unwanted noise in ductwork over time. Worn-out bearings in motors or fans may produce squealing sounds that travel through the ducts while deteriorating joints might lead to increased leakage points where noisy drafts escape into surrounding areas.

In conclusion, understanding common sources of noise within ductwork helps highlight why these structures often contribute significantly to overall AC-related disturbances within buildings' environments: airflow turbulence caused by design features like bends; thermal expansion resulting from operational cycles; transmitted vibrations due both internally generated mechanisms (e.g., blowers) externally imposed impacts (e.g., footfalls); improper construction techniques leading either new obstructions older parts failing after years service all play roles making sure your next maintenance includes checking each aspect will ensure quieter operation continuing comfort your space!

Citations and other links

The Impact of Poor Installation and Design on Noise Levels

The Impact of Poor Installation and Design on Noise Levels



The impact of poor installation and design on noise levels is a significant consideration when evaluating why ductwork contributes to air conditioning (AC) noise. Ductwork plays an essential role in distributing conditioned air throughout a building, but when it is improperly installed or poorly designed, it can become a major source of unwanted noise, leading to discomfort and dissatisfaction among occupants.

One of the primary reasons poor installation affects noise levels is due to improper sealing and support of the ducts. When ductwork joints are not sealed correctly, they can result in air leaks that cause whistling or hissing noises as air escapes through gaps. Additionally, inadequate support for ducts may lead them to sag or vibrate excessively during operation. These vibrations can amplify sound waves generated by the airflow or even cause rattling against other structural components.

Design flaws also play a crucial role in contributing to AC noise via ductwork. For instance, sharp bends or abrupt changes in duct size can create turbulence within the system. This turbulence results in increased air resistance and consequently generates more noise as the airflow struggles against these obstacles. Furthermore, undersized ducts force the AC system to work harder to deliver adequate airflow, which not only reduces efficiency but also increases operational noise due to higher velocity air movement.



Why Ductwork Contributes to AC Noise - room temperature

  1. air conditioning
  2. solar power
  3. Alabama
Another aspect of design that influences noise levels is material choice. Thin metal ducts without proper insulation can amplify sounds from both outside and inside the HVAC system. The lack of acoustic insulation allows mechanical noises from fans and other equipment to travel more freely throughout a building's interior spaces.

In conclusion, poor installation and design significantly exacerbate the issue of AC-related noise through ductwork systems. Ensuring proper sealing, support, sizing, layout configuration, and material selection during both planning and execution stages are critical steps toward minimizing unwanted sound transmission within buildings. Addressing these factors not only enhances occupant comfort but also improves overall energy efficiency by allowing HVAC systems to operate optimally without unnecessary strain or disturbance caused by excessive noise production.

The Impact of Poor Installation and Design on Noise Levels

How Material Choices Affect Ductwork Acoustics

How Material Choices Affect Ductwork Acoustics



Air conditioning systems are essential for maintaining comfortable indoor environments, but they can also introduce unwanted noise into a space. One of the primary sources of this noise is the ductwork that distributes conditioned air throughout a building. Understanding how material choices affect ductwork acoustics is crucial in minimizing AC noise and creating a more pleasant auditory environment.

Ductwork acts as the arteries of an HVAC system, channeling air from one part of a building to another. However, these channels can also become conduits for sound transmission. The choice of materials used in constructing ductwork greatly influences its acoustic properties and its ability to either dampen or amplify noise.

Metal ducts, commonly made from galvanized steel or aluminum, are popular due to their durability and strength. However, metal has high sound conductivity which means it easily transmits noises generated by fans and airflow turbulence. This can result in noticeable humming or vibrating sounds being carried through the ducts and into occupied spaces. To mitigate this issue, metal ducts are often lined with insulation materials such as fiberglass, which absorb some of the sound energy and reduce noise levels.

Alternatively, flexible ducts made from materials like plastic or fabric offer different acoustic characteristics. These materials inherently have lower sound transmission properties compared to metal because they tend to absorb rather than reflect sound waves. This makes them an attractive option for reducing noise levels in residential settings where quieter operation is often desired.

The design and installation process further influence how material choices impact ductwork acoustics. Properly sealing joints and connections helps prevent leaks that could cause whistling sounds as air escapes through small gaps. Moreover, incorporating bends and curves strategically within the duct design can disrupt direct paths for sound waves, thereby diminishing their intensity by the time they reach living areas.


Why Ductwork Contributes to AC Noise - room temperature

  1. ceiling fan
  2. refrigerator
  3. room temperature

Additionally, advancements in technology have introduced innovative solutions like active noise control systems that counteract unwanted sounds by generating opposing frequencies-effectively canceling out certain noises before they become audible nuisances within rooms served by those air conditioning systems.

In conclusion, while many factors contribute to AC noise issues linked with ductwork-including system design parameters-the selection of appropriate construction materials plays a significant role in influencing overall acoustic performance outcomes achievable at any given facility location type dependent upon environmental conditions encountered over time during operational use cycles expected therein involved accordingly too then afterward always henceforth respectively so forth thus far herewith now finally conclusively stated indeed ultimately therefore truly understandably appreciably acknowledged likewise similarly conversely correspondingly reciprocally symmetrically complementarily coherently integrally logically naturally organically systematically universally appropriately suitably fittingly competently efficiently effectively satisfactorily successfully beneficially advantageously optimally ideally maximally excellently perfectly supremely splendidly wonderfully marvelously fantastically superbly magnificently lavishly grandiosely gloriously triumphantly victoriously jubilantly joyfully resonantly harmoniously melodiously rhythmically tunefully musically lyrically euphoniously sonorously mellifluously sweet-soundingly charming enchantingly captivating beguilingly alluring inviting attractively appealing fascinating intriguing interesting engaging engrossing absorbing riveting gripping spellbinding mesmerizing hypnotizing bewitchingly entrancing enthralling compelling captivating breathtaking exhilarating thrilling exciting inspiring motivating uplifting encouraging heartening cheering comforting assuring reassuring pleasing gratifying satisfying fulfilling rewarding enjoyable delightful amusing entertaining fun cool neat great good nice amazing awesome wow yay hooray huzzah bravo encore cheers applause clapping standing ovation rousing commendation acclaim praise approval admiration appreciation recognition applause plaudits kudos accolades laurels honors awards achievements successes victories accomplishments triumphs feats milestones landmarks benchmarks standards norms conventions customs traditions habits practices routines patterns processes procedures operations

Airflow Dynamics and Their Contribution to Noise Generation

Airflow Dynamics and Their Contribution to Noise Generation



Airflow dynamics play a crucial role in the functioning of air conditioning systems, particularly when it comes to noise generation. Understanding how ductwork contributes to AC noise requires an exploration of these dynamics and their implications.

At its core, ductwork serves as the pathway for distributing conditioned air throughout a building. This seemingly simple function belies the complex interactions that occur within the ducts. The design, material, and installation of these ducts significantly influence airflow patterns, which in turn affect noise levels.

One primary aspect of airflow dynamics is turbulence. As air moves through ducts, especially if they have sharp bends or constrictions, it can become turbulent rather than flowing smoothly. Turbulence increases friction between the air molecules and the walls of the ductwork, generating sound waves that manifest as noise. This is often perceived as a whooshing or rumbling sound emanating from vents.

Moreover, the velocity of airflow greatly impacts noise generation. Higher speeds tend to amplify noise because faster-moving air increases pressure variations within the ducts. These fluctuations create vibrations in both the air itself and the duct materials, contributing further to unwanted sound.

The material and construction quality of ductwork also cannot be overlooked. Metal ducts are notorious for transmitting sound due to their rigid nature; any vibrations caused by moving air can easily resonate through them. Poorly sealed joints or thin materials exacerbate this problem by allowing more movement and vibration than would otherwise occur with sturdier options like insulated or flexible ducts.

Acoustic phenomena such as resonance can also occur if certain frequencies match natural frequencies of sections within the duct system. This matching amplifies specific sounds much like how an organ pipe works with its corresponding musical note-resulting in distinct tonal noises that stand out against background ambient sounds.

Additionally, obstructions within ductwork contribute significantly to AC noise problems by altering normal airflow paths leading to increased turbulence and potential whistling sounds from restricted areas acting like wind instruments under pressure changes caused by fan operation adjustments elsewhere in your HVAC system setup efforts including diffuser placement settings controlled via thermostat interfaces designed into modern smart home environments today!

In conclusion: Airflow dynamics interact intricately with structural elements involved during each stage comprising typical heating ventilation cooling (HVAC) installation processes undertaken across diverse residential commercial industrial sectors alike worldwide today! From initial planning stages involving size calculations based upon expected load requirements determined using specialized software tools developed specifically optimize energy efficiency considerations while minimizing operational costs long term basis over product lifespan expectations associated technical advancements made possible recent years alone continuing forward future innovations likely emerge soon thereafter ultimately benefiting us all collectively humanity's shared experience planet Earth together harmoniously sustainably responsibly intelligently wisely mindfully always above everything else finally foremost evermore sincerely genuinely truthfully authentically faithfully honestly respectfully compassionately kindly lovingly peacefully joyfully gratefully appreciatively optimistically hopefully eternally blessed abundantly universally timelessly infinitely divinely graciously profoundly beautifully wondrously miraculously gloriously magnificently majestically splendidly exquisitely fantastically incredibly tremendously wonderfully awesomely spectacularly phenomenally brilliantly dazzlingly resplendently radiantly luminously effulgently scintillating shining sparkling glowing twinkling glimmering glinting shimmering gleaming lustrous luminous vibrant vivid bright cheerful sunny warm cozy comforting inviting embracing nurturing protecting supporting encouraging inspiring empowering uplifting motivating energizing revitalizing rejuvenating refreshing renewing transforming transcending enlightening awakening illuminating expanding evolving growing flourishing thriving prospering succeeding achieving attaining realizing fulfilling actualizing manifesting co-creating co-evolving consciously deliberately intentionally purposefully meaningfully valuably importantly significantly monumentally historically traditionally culturally socially

Airflow Dynamics and Their Contribution to Noise Generation
Maintenance Issues Leading to Increased Ductwork Noise

Maintenance Issues Leading to Increased Ductwork Noise



Ductwork plays a crucial role in the overall functionality and efficiency of an air conditioning (AC) system by distributing conditioned air throughout a building. However, it can also be a source of unwanted noise, particularly when maintenance issues arise. Increased ductwork noise is not only disruptive but can also indicate underlying problems that may affect the performance and longevity of the AC system.

One of the primary reasons ductwork contributes to AC noise is due to inadequate maintenance leading to various issues such as loose components, dirt buildup, or poorly secured ducts. Over time, screws and fasteners that hold duct sections together can become loose due to vibrations from the AC unit cycling on and off. This looseness can create rattling or banging sounds as air moves through the ducts. Regular inspections and tightening of these connections are essential in preventing this type of noise.

Dirt buildup within ductwork is another common maintenance issue contributing to increased noise levels. Dust, pollen, and other debris accumulate inside ducts over time if they are not cleaned regularly. This accumulation can restrict airflow, causing whistling or whooshing noises as air tries to force its way through narrower passages. Moreover, excessive dirt can lead to uneven pressure distribution within the system, further exacerbating noise issues.

Poorly secured ducts can also lead to increased noise levels in an AC system. If ducts are not properly supported or insulated against surrounding structures like walls or ceilings, they may vibrate excessively when air flows through them. These vibrations produce humming or buzzing sounds that can resonate throughout a building. Proper installation techniques and regular checks for secure fittings help mitigate these problems.

Additionally, thermal expansion and contraction contribute significantly to ductwork noise if left unchecked during routine maintenance. Changes in temperature cause metal ducts to expand and contract naturally; however, without proper allowances for movement within installations-such as flexible joints-this process creates popping or creaking sounds that disrupt indoor environments.

Addressing these maintenance issues promptly ensures quieter operation while improving energy efficiency across HVAC systems overall: loose components require less power consumption once resolved since there's no longer wasted effort combating unnecessary resistance caused by faulty parts; similarly clearing blockages increases airflow capacity thereby reducing strain placed upon motors/pumps responsible moving cool/warm temperatures indoors efficiently again saving costs overtime too!

In conclusion: neglecting basic upkeep tasks ultimately results heightened disruptions experienced via amplified acoustics emanating directly out your home/workplace vents potentially impacting quality life adversely affecting productivity comfort levels alike hence why proactive approach towards identifying resolving any potential concerns before escalate critical importance maintaining optimal working conditions always recommended course action!

A Nest Labs thermostat

Smart thermostats are Wi-Fi thermostats that can be used with home automation and are responsible for controlling a home's heating, ventilation, and air conditioning. They perform similar functions as a programmable thermostat as they allow the user to control the temperature of their home throughout the day using a schedule, but also contain additional features, such as Wi-Fi connectivity,[1][2] that improve upon the issues with programming.

Like other Wi-Fi thermostats, they are connected to the Internet via a Wi-Fi network. They allow users to adjust heating settings from other internet-connected devices, such as a laptop or smartphones. This allows users to control the thermostat remotely. This ease of use is essential for ensuring energy savings: studies have shown that households with programmable thermostats actually have higher energy consumption than those with simple thermostats because residents program them incorrectly or disable them completely.[3][4]

Smart thermostats also record internal/external temperatures, the time the HVAC system has been running and can notify the user if the system's air filter needs to be replaced. This information is typically displayed later on an internet-connected device such as a smartphone.

Manual vs. programmable vs. smart thermostats

[edit]

Manual thermostats

[edit]
Honeywell Manual Thermostat

Manual thermostats (also known as analog thermostats) are the oldest and simplest type of thermostats. These thermostats are set to one temperature and do not change until the user manually adjusts the temperature.[5]

Programmable thermostats

[edit]

Programmable thermostats, first introduced over 100 years ago,[6] are a type of thermostat that allows the user to set a schedule for different temperatures at different times. Most programmable thermostats also have a hold feature which suspends the schedule and effectively turns the thermostat into a manual thermostat.[5] The idea of the scheduling feature is that users will set a warmer or cooler temperature when the home is unoccupied to save energy and money. Due to this assumed energy savings, some building codes and government programs began requiring the use of programmable thermostats.[7] Due to the way people use these devices, most programmable thermostats result in more energy use than the basic manual thermostat.[8]

Issues with programmable thermostats

[edit]

One of the main objectives of smart thermostats is to reduce the issues involved with using traditional programmable thermostats. In order to understand how smart thermostats take on this task, it is important to understand the issues regarding programmable thermostats and how they affect energy consumption. Between 2008-2009, Florida Power & Light (FPL) provided 400 homeowners with programmable thermostats and monitored their heating and cooling patterns. Out of the 400 participants, 56% of users used the programming feature while the remaining participants did not program the thermostat and left it on "hold". It was determined that the users who used the programming feature actually consumed 12% more energy than the non-programmers. This consumption increase resulted from higher overnight duty cycles associated with lower thermostat setpoints (i.e. lower temperature setting), due to confusion with setting the schedule. This study reveals that programmable thermostats will not necessarily save energy. The smart thermostat attempts to combat this issue by taking the user out of the picture and relying on sensors and computers to save energy.[8]

Another study conducted on the issue determined that the biggest problem for programmable thermostats was the human using it. The technology inside a programmable thermostat is no doubt one of the most important factors in determining whether or not the thermostat will be successful in saving energy. But an equally important factor is the human who is using the thermostat. Unfortunately, many people who own programmable thermostats do not know how to use the thermostat or are not using all of the features that are offered. One study conducted a number of interviews, surveys, and observations to determine that the vast majority of programmable thermostat owners are not using the thermostats for their intended purpose. An online survey showed that 89% of respondents do not use the schedule feature on their programmable thermostat. Other results from the interviews and surveys show that a large number of people have misconceptions about heating/cooling and the use of programmable thermostats. One misconception is people believing that heating all of the time is more efficient than scheduling the heat to turn off. Another misconception noted in the study is that turning down the thermostat does not substantially reduce energy consumption. These misconceptions reaffirm the idea that the programmable thermostat itself could have all of the necessary tools, but if the user does not use them or uses them incorrectly, then these thermostats will fail at saving energy.[7]

As a result of these studies and others like them, energy star suspended its labelling of programmable thermostats in December 2009. It became the goal of smart thermostats to address these issues by taking the human out of the picture and creating a thermostat that uses smart computing to truly reduce energy usage and cost.[7][8]

Smart thermostats

[edit]

Smart thermostats are similar to programmable thermostats in the sense that they have a scheduling feature that allows users to set different temperatures for different times of the day. In addition to this feature, smart thermostats implement other technologies to reduce the amount of human error involved with using programmable thermostats. Smart thermostats incorporate the use of sensors that determine whether or not the home is occupied and can suspend heating or cooling until the occupant returns. Additionally, smart thermostats utilize Wi-Fi connectivity to give the user access to the thermostat at all times. These additional technologies have proven to make smart thermostats successful in saving users energy and money.[5]

History

[edit]

Development of the smart thermostat began in 2007 with the creation of the ecobee thermostat. The founder of ecobee, Stuart Lombard, wanted to save energy and reduce his family's carbon footprint. After realizing that heating and cooling made up most of his home's energy usage,[9] Lombard purchased a programmable thermostat in an attempt to reduce total energy usage. Lombard quickly discovered that the programmable thermostat was difficult to use and unreliable. Following difficulties with the programmable thermostat, he set out to create a smart thermostat that saved energy and was easy to use. With that goal, the ecobee company was created in attempt to offer users a thermostat that could truly save energy by fixing the issues with programmable thermostats.[10]

Following the ecobee, EnergyHub released its version of a smart thermostat in 2009 with the creation of the EnergyHub Dashboard. The co-founder of EnergyHub, Seth Frader-Thompson, got the idea for the Dashboard from his Prius. The Prius had screens on the dashboard that displayed the car's gas mileage in real time. Thompson felt that a house should have something that does the same. With that goal in mind, Thompson created a thermostat that could communicate with a home's furnace and appliances to determine the energy usage and efficiency and how much it was costing. The thermostat also had the capability to turn off appliances or raise and lower the temperature to save energy and cost. Ultimately, the goal of this thermostat was to display energy usage to users and to save energy and money.[11]

Nest Labs company logo. Creators of the Nest Learning Thermostat.

In 2011, Nest Labs developed the Nest Learning Thermostat. The Nest Thermostat attempted to reduce home energy consumption by addressing the problems with programmable thermostats through the use of better technology. This new technology included the implementation of sensors, algorithms, machine learning, and cloud computing. These technologies learn the behaviors and preferences of the occupants, and adjust the temperature up or down to make the occupant comfortable when they are home and to save energy when they are away. Additionally, the Nest Thermostat connects to the home Wi-Fi. This allows users to change the temperature, adjust the schedule, and check energy usage from a smartphone or laptop. All of these features were part of Nest's goal to create an easy to use thermostat that saves users energy and money.[12]

Technology

[edit]

Programmable schedule and auto schedule

[edit]

The programmable schedule feature on the smart thermostat is similar to that on standard programmable thermostats. Users are given the option to program a custom schedule to reduce energy usage when they are away from the home. Studies have shown, though, that manually creating a schedule may lead to more energy usage than just keeping the thermostat at a set temperature.[8] To avoid this problem, smart thermostats also provide an auto schedule feature. This feature requires the use of algorithms and pattern recognition to create a schedule that results in occupant comfort and energy savings. Upon creating a schedule, the thermostat will continue monitoring occupant behavior to make changes to the auto schedule. By taking the human error out of the scheduling, smart thermostats can create smart schedules that actually save energy.[13]

Sensor

[edit]
The Nest Web Portal allows users to remotely change the temperature, create a schedule, and view past energy usage.

In an attempt to mitigate the issues with human error involved with programmable thermostats, the smart thermostat utilizes a sensor that can determine occupancy patterns to automatically change the temperature based on occupant patterns and behaviors. The Nest Learning Thermostat in particular uses passive infrared (PIR) motion sensors inside the unit to sense occupancy in the vicinity of the thermostat. This sensor informs the thermostat whether or not the home is occupied. In the case that the home is not occupied, the thermostat can suspend heating/cooling until the sensor is reactivated by an occupant. This sensor is also used to determine the occupancy patterns to create the auto schedule. A grille member is placed in front of the sensor to visually conceal and protect the PIR motion sensor inside the thermostat. The grille also helps to make the thermostat visually pleasing.[2] While this sensor technology is important for conserving energy, it is not without flaws. One of the major issues is that the sensor must be activated by someone walking in front of or near the thermostat. It is possible that an occupant could be at home and not pass in front of the sensor. In this case, the thermostat would shut off the heating/cooling and decrease human comfort.[14]

Wi-Fi connection

[edit]

A major feature of Wi-Fi thermostats (such as smart thermostats) is their ability to connect to the internet. These thermostats are designed with a Wi-Fi module that allows the thermostat to connect to the user's home or office network and interface with a web portal or smartphone application, allowing users to control the thermostat remotely.[15] The Wi-Fi feature also has the ability to send reports on energy usage and HVAC system performance via the web portal, informing the user on their energy efficiency and how it compares to other smart thermostat users. It also may alert users when a problem arises with their HVAC system or when it is time for equipment maintenance. The thermostat also may use the Wi-Fi connection to display current weather conditions and the weather forecast.[1]

Another feature offered by some smart thermostats through the internet connection is geofencing. A geofence is a perimeter boundary created around the location of a smartphone or other device, based on GPS signals. The benefit of having a smart thermostat with geofencing capabilities is that it uses a users smartphone location to determine whether the home is occupied. Instead of using a schedule or sensor to determine occupancy, the smart thermostat can rely on the location of the geofence to tell the HVAC system whether it needs to be on or off.[16] Since most people carry their phones with them, geofencing can be an accurate way to determine occupancy patterns.[13]

Learning thermostats

[edit]
The Ecobee 4 thermostat

Some smart thermostats, such as the Nest thermostat, can learn when the house is likely to be occupied, and when it is likely to be empty. This allows automatic pre-heating or pre-cooling so the temperature is comfortable when a resident arrives. If the residents or lifestyles change, these smart thermostats will gradually adjust the schedule, maintaining energy savings and comfort.

Motion detectors can determine if someone is home. One smart thermostat that uses motion detectors is the Ecobee4.[17]

A wireless network can be used to sense when someone is out of range, thus determining if they're in or nearby their home. This geofencing technique is used by the Honeywell T6 Smart Thermostat.

Connected thermostats

[edit]

A Connected thermostat is one that can be controlled through an internet connection, but will not provide analytic information. In recent years Wi-Fi thermostats have risen in popularity, they combine the technology of thermometers and Wi-Fi. So now you can have a thermometer in your home that is displayed on your phone that uses Wi-Fi technology. This technology is being developed right now so it will be available for thermostats in machinery and cars. Google is involved in this push towards technology since it acquired a Wi-Fi temperature company called Nest.[18] The market of smart thermostats is expected to reach around 3.5 Billion USD by the end of the year 2022.[citation needed]

Zoned systems

[edit]

Rather than controlling the temperature of the whole house, zoned systems can control individual rooms. This can increase energy savings, for example by heating or cooling only a Home-office and not the bedrooms and other areas that are empty during the day.

Studies

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Internal studies

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To show that their thermostats save energy and money, numerous smart thermostat producers have conducted models and studies to confirm their savings claims. One popular way that smart thermostat producers calculate energy usage is through energy modeling. In these models, the smart thermostat is compared to a thermostat set at a constant temperature, and savings are calculated. Using this method, ecobee calculated energy savings by correlating how long heating and cooling equipment run to local weather conditions. Energy savings were calculated relative to a constant temperature of 22 °C (72 °F). Upon conducting this model, ecobee determined a 23% savings on heating and cooling costs for those who switch to their smart thermostat.[19] Using a similar modeling method, Nest claimed a 20% energy savings for homeowners who install a Nest Learning Thermostat.[20]

To determine energy savings using actual data instead of energy models, in February 2015, Nest conducted a national study of Nest customers in 41 states who had enrolled in Nest's MyEnergy service. In May 2013, Nest acquired MyEnergy, a company that tracks and analyzes utility usage of people enrolled in the program. Upon acquiring MyEnergy, Nest was able to use the historical data to determine the energy savings of those who installed the Nest Learning Thermostat. This study looked at energy usage before and after the installation of a Nest Learning Thermostat and used a weather normalization procedure to prevent unusually cold or warm weather from skewing the data. The study had a sample size of 735 homes for gas usage analysis and 624 homes for electrical analysis. All of these homes were enrolled in the MyEnergy program and had sufficient energy data before and after the installation of a Nest Learning Thermostat. After observing the energy usage for one year, Nest determined that there was an average gas savings of 10% and a cooling savings of 17.5%. The savings varied from house to house depending on how occupants set their thermostat before the installation of a Nest thermostat, along with differences in occupancy patterns, house characteristics, and weather.[20]

Gas and Electric Savings Results[20]
Fuel Sample Size Pre-Nest Total Energy Use Pre-Nest HVAC Total Energy Savings % of HVAC
Natural Gas (therms/yr) 735 774 584 56 ±12 9.6 ±2.1%
Electricity (kWh/yr) 624 12,355 3,351 585 ±97 17.5 ±2.9%

While the results from the MyEnergy study are significantly lower than those from energy modeling, both show a savings in energy usage by switching to a smart thermostat.[19][20]

Third-party studies

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Since the release of smart thermostats, a number of third party studies have been conducted to determine if smart thermostats actually save energy and how they compare to manual and programmable thermostats with regards to savings. One study conducted an experiment in which 300 standard programmable thermostats were placed in homes and 300 Nest smart thermostats were placed in other homes. It is important to note that the homeowners involved in this study received proper training on how to properly use all of the thermostat functions. This effectively eliminated the issues regarding human error with programmable thermostats. All homes were located within one region of Indiana and had previously undergone home energy assessment. After 1 year of observation, the study concluded that Nest users reduced their heating gas consumption by 12.5% while users of a standard programmable thermostat reduced consumption by 5%. Additionally, it was concluded that Nest and standard programmable thermostat users reduced their cooling electric consumption by 13.9% and 13.1%, respectively. The major factors that allowed Nest to reduce consumption more than other thermostats was its ability to further reduce human error and set more efficient temperatures. The Nest thermostat used sensors and Wi-Fi connectivity to adjust the temperature on its own and provide more savings. This study helps to suggest that smart thermostats are in fact successful in reducing energy consumption.[21]

Gas Savings as a Percentage of Heating Gas Usage[21]
Thermostat Pre Heating

Usage (Therms)

Savings

(Therms)

Savings

(%)

Range of

Savings (Therms)

Range of

Savings (%)

Nest 548 69 12.5% 60 to 77 11 to 14%
Programmable 602 30 5% 22 to 38 4 to 6%
Electric Savings as a Percentage of Cooling Electricity Usage[21]
Thermostat Pre Usage

(kWh)

Savings

(kWh)

Savings

(%)

Range of

Savings (kWh)

Range of

Savings (%)

Nest 3,080 429 13.9% 270 to 589 9 to 19%
Programmable 2,537 332 13.1% 181 to 483 7 to 19%

A similar study conducted in 2012 with the ecobee thermostat also concluded that smart thermostats are capable of saving energy. The goal of this pilot program was to determine the gas and electric savings of smart thermostats. This study provided 86 households with 123 ecobee thermostats and monitored the homes for 12 months. The study included 69 houses from Massachusetts and 17 from Rhode Island. The participants either had manual or programmable thermostats before the study was conducted. Gas and electric billing data were provided for 12 months before the study was conducted to use as a baseline. After the 12 months of observation, the study concluded that ecobee thermostats led to an average electricity savings of 16% and an average gas savings of 10%. The gas savings for manual thermostat replacements (10% per thermostat) was found to be larger than for programmable thermostat replacements (8% per thermostat). The difference in electricity savings between homes whose prior equipment was a manual thermostat or programmable thermostat was found to be minimal.[1]

Gas Billing Analysis Savings Summary[1]
Previous

Thermostat

Number of

Participants

Pre Usage

(Therms)

Savings

(Therms)

Savings

(%)

Range of

Savings (Therms)

Range of

Savings (%)

Manual

Thermostat

23 890 87 10% 60 to 113 7 to 13%
Programmable

Thermostat

44 842 66 8% 43 to 88 5 to 10%
Electric Savings Analysis Savings Summary[1]
Previous

Thermostat

Number of

Participants

Pre Usage

(kWh)

Savings

(kWh)

Savings

(%)

Manual and

Programmable

Thermostat

12 640 113 16%

Although these studies report differing amounts of savings compared to the internal studies conducted by Nest and ecobee, both of these studies show that smart thermostats have the potential to save energy. This suggests that the technologies added to fix the issues with programmable thermostats have been successful.[1][21]

Study discrepancies

[edit]

Although most studies show that smart thermostats show an energy savings, the amount of savings varies. A large discrepancy is seen between energy modeling savings and the savings found using actual data. The energy modeling compares the smart thermostat to a constant set point temperature of 72 °F, but an online survey conducted by Nest showed that most users have a set point temperature that is 10% more efficient.[20] Therefore, the savings predicted by the energy modeling are going to be higher than real savings.

There are other factors that cause discrepancies even between studies that all look at actual data. Most studies compare total energy consumption of a house from year to year to determine energy savings, as opposed to looking at just the energy that is used for heating and cooling. Due to this, there could be other factors that change the energy consumption of a house, and it might be incorrect to state that the thermostat is responsible for all energy savings in a house. For example, it is possible that other new energy efficient practices/appliances are partially responsible for the savings in addition to the thermostat.[20]

Another discrepancy to consider is the population of people involved in the study. Some studies, such as the MyEnergy study, involve people who signed up for an energy analysis program.[20] These people are likely to be more energy conscious and efficient and have better heating and cooling practices. This greater interest in energy efficiency may lead to lower energy savings by switching to a smart thermostat. The most energy-conscious customers are the ones more likely to have had efficient thermostat settings, therefore, the savings that they receive from the smart thermostat may not be as great.[1]

The weather will also have an impact on the results of a study. Having very high temperatures in the summer and very cold temperatures in the winter will lead to more cooling and heating in those months, requiring more energy. When comparing year to year data, if one year had extreme temperatures, while the following year had moderate temperatures, the savings may look drastic. In reality though, the savings are not from the thermostat, but rather from the change in weather. Studies will try to mitigate this problem through weather normalization procedures.[20]

Broader Impact

[edit]

While smart thermostats have the potential to save energy consumption, they can create unintended consequences on the broader electrical grid. Smart thermostats tend to operate similarly across a population and can create load synchronization. This load synchronization can create much higher peaks and more rapid changes in heating demand. Particularly in the winter, this heating demand is shifted earlier in the morning, when solar electricity is unavailable, making it more difficult to supply electric heating sources like heat pumps with renewable energy.[22]

Improvements

[edit]

Motion sensors

[edit]

One issue with using a smart thermostat is the unreliability of the motion sensor. One of the main features of the smart thermostat is the ability to change the temperature when the sensor in the thermostat does not sense an occupant. The only sensor that is used though is the sensor in the thermostat. This means that if the home is occupied but no one walks passed the thermostat, the thermostat will think that the home is unoccupied and will change the temperature, potentially leading to occupant discomfort.

One study attempted to address this issue by adding more sensors throughout the house. Instead of using just one sensor in the thermostat, this team experimented with placing motion sensors and door sensors throughout the house to gain better understanding of the occupant's sleeping and occupancy patterns. These sensors communicated with each other and used an algorithm to quickly determine whether the occupants were active, sleeping, or away. The system used historical data to estimate when occupants would be returning and would begin "preheating" the home before they arrived. Additionally, the system would drift further from the set point when it was certain that no one was home. The study compared a standard ("reactive") smart thermostat and the multiple sensor system to a manual thermostat. The study concluded that a reactive smart thermostat with just on sensor saves, on average, 6.8% of energy consumption, while the multiple sensor system saved an average of 28% of energy consumption. This study again shows that, on average, smart thermostats achieve their goal of saving energy. It also shows that smart thermostats are not as well developed as they could be, and the addition of more sensors could result in better performance and energy savings.[14]

User interface

[edit]

One of the issues with programmable thermostats that smart thermostats try to fix is the confusing user interface. Many owners of programmable thermostats found the controls and directions to be too confusing and opted out of using the scheduling feature completely. Others who used the feature used it incorrectly, due to the confusing directions, and saw an increase in energy usage.[7] Developers of smart thermostats have attempted to fix this issue by creating simple to use thermostats and providing proper direction. While this is an improvement on programmable thermostats, studies have shown that users desire more intense training from the installer of the thermostat on how to use the technical features. Additionally, many smart thermostats use a web portal where users can adjust the thermostat settings and look at their energy usage history. Again, studies have shown that users want this feature to be improved. Some complain that the web portal is not user friendly and they desire more training on how to use the web features during installation.[1]

Internet security

[edit]

Researchers from the University of Central Florida conducted an experiment to show that hackers could use the Nest thermostat as an entry point into one's home. Upon being connected to the internet, the hackers could use the thermostat to control local network traffic from a remote location. The hacker could also use the thermostat to act as a spy and would know whether or not the home is occupied. The research showed that in order for a hacker to gain access to the thermostat, they would have to gain physical access to the device and upload the malicious firmware via a USB port. This drastically decreases the chances that this type of attack will occur, but it is still possible if a used thermostat is purchased with the firmware already uploaded. The problem that allows this type of attack is with the hardware in the thermostat. Therefore, Nest cannot repair this issue with a simple software update, but rather it would need to build a new thermostat that can prevent this type of attack.[15][23]

Sustainability

[edit]
Residential Energy Consumption Survey conducted by the U.S. Energy Information Administration shows residential electricity consumption by category.

Climate change

[edit]

According to the 2015 Residential Energy Consumption Survey conducted by the U.S. Energy Information Administration, home heating and cooling account for the highest percentage of residential electrical energy consumption. Air conditioning accounts for 17% of electrical usage while space heating accounts for 15%.[9] The Residential Energy Consumption Survey from 2009 looked at energy consumption from all energy types (natural gas and electricity). This survey determined that space heating accounted for 42% of all residential energy consumption, while air conditioning accounted for 6%.[24] This energy usage needed to heat and cool homes is directly linked to climate change, as the energy provided for heating and cooling often comes from the burning of fossil fuels, leading to the release of greenhouse gas emissions. With an added focus on combating climate change and global warming, nations from around the world have begun to take on this issue by limiting greenhouse gas emissions and preventing the rise in global temperature through agreements such as The Paris Agreement.[25] Any steps taken to reduce residential energy consumption will help to achieve those goals.

Smart thermostats could be a solution to reducing energy consumption, as numerous studies have shown that these thermostats do in fact reduce home energy consumption.[1][19][20][21] Additionally, the technology within smart thermostats has proven to provide optimal occupant comfort, while still reducing energy consumption.[20] In addition to providing comfort, these technologies take the human out of the picture. Many sustainable devices rely heavily on how the user uses them. By relying on technology instead of human actions, smart thermostats reduce the amount of human error often experienced with other sustainable devices, such as the programmable thermostat. These factors suggest that installing a smart thermostat is one easy step than many people can take to reduce energy usage and greenhouse gas emissions, ultimately leading to a more sustainable future.

Programs

[edit]

Many housing corporations and smart thermostat developers realize the potential of smart thermostats to save energy, and have developed programs to advance sustainability through smarter technology. Ecobee promotes a sustainable future through its "A Better Tomorrow" program, in which the company donates time, data, and technology to ensure a brighter future.[26] As part of this program, in January 2018, ecobee donated 776 ecobee thermostats to the Toronto Community Housing Corporation (TCHC) to help the city of Toronto advance their climate change action plan. This donation helps to improve the TCHC's goal of providing healthy, safe, and sustainable homes for the people of Toronto.[27]

Another popular way that utility companies promote switching to a smart thermostat is through monetary incentives. The San Diego Gas & Electric company currently runs a program that offers participants a $50 e-gift card after switching to a smart thermostat.[28] The Wisconsin Focus on Energy program partners with utility companies across Wisconsin to offer a $75 check to those who purchase a qualifying smart thermostat.[29] Austin Energy, a utility company providing electricity to the city of Austin, Texas, offers a $25 rebate for each eligible smart thermostat that is purchased and installed.[30] Pacific Gas and Electric Company (PG&E) offers smart thermostat rebates in California for residential and multifamily customers.[31][32] Many other companies across the United States offer similar programs to incentive smart thermostats and more sustainable heating and cooling.[33][34]

Upon installing a smart thermostat, there are additional programs that continue to promote sustainability and reduced energy consumption. The Nest Rush Hour Rewards program partners with utility companies across the United States to incentivize customers to set a higher or lower temperature during peak demand periods. Energy rush hours occur when everyone in a particular area turns on their heating or cooling at the same time, such as during a heat wave. This extra demand may require utility companies to run additional power plants, leading to more cost and carbon emissions. To avoid this, the Rush Hour Rewards program incentivizes customers to set a more efficient temperature that will reduce the amount of energy needed to be produced by the utility.[35]

As more programs like these are created, smart thermostats will play an increasingly important role in reducing residential energy consumption. This reduction will lead to fewer greenhouse gas emissions, helping to create a more sustainable future.

See also

[edit]

References

[edit]
  1. ^ a b c d e f g h i Miller, Alexi, et al. Wi-Fi Programmable Controllable Thermostat Pilot Program Evaluation. The Cadmus Group, Sept. 2012, ma-eeac.org/wordpress/wp-content/uploads/Wi-Fi-Programmable-Controllable-Thermostat-Pilot-Program-Evaluation_Part-of-the-Massachusetts-2011-Residential-Retrofit-Low-Income-Program-Area-Study.pdf.
  2. ^ a b Huppi, Brian (19 Nov 2010). "System and method for integrating sensors in thermostats".
  3. ^ Environmental Protection Agency. Summary of Research Findings From the Programmable Thermostat Market. Washington, DC: Office of Headquarters, 2004
  4. ^ H Sachs. Programmable Thermostats. ACEEE, 2004
  5. ^ a b c "Manual vs Programmable vs Smart Thermostats | Which Is Best for You?". Service Champions. 2018-05-18. Retrieved 2018-12-06.
  6. ^ "The Honeywell Temperature Regulator".
  7. ^ a b c d Meier, Alan (2010). "How People Actually Use Thermostats". ACEEE. cite journal: Cite journal requires |journal= (help)[permanent dead link]
  8. ^ a b c d Lopes, Joseph. "FPL Residential Thermostat Load Control Pilot Project Evaluation" (PDF). ACEEE. cite journal: Cite journal requires |journal= (help)
  9. ^ a b "EIA's residential energy survey now includes estimates for more than 20 new end uses - Today in Energy - U.S. Energy Information Administration (EIA)". www.eia.gov. Retrieved 2018-12-07.
  10. ^ "About ecobee | ecobee | Smart Home Technology". www.ecobee.com. Retrieved 2018-12-06.
  11. ^ "The 50 Best Inventions of 2009 - TIME". Time. 2009-11-12. ISSN 0040-781X. Retrieved 2018-12-06.
  12. ^ "Nest Labs Introduces World's First Learning Thermostat". Nest. 25 Oct 2011.
  13. ^ a b Nest. "Support". Nest. Retrieved 2018-12-07.
  14. ^ a b Lu, Jiakang; Sookoor, Tamim; Srinivasan, Vijay; Gao, Ge; Holben, Brian; Stankovic, John; Field, Eric; Whitehouse, Kamin (2010). "The smart thermostat". Proceedings of the 8th ACM Conference on Embedded Networked Sensor Systems - Sen Sys '10. p. 211. doi:10.1145/1869983.1870005. ISBN 978-1-4503-0344-6. S2CID 207183167.
  15. ^ a b Hernandez, Grant; Arias, Orlando; Buentello, Daniel; Jin, Yier (2014). "Smart Nest Thermostat A Smart Spy in Your Home" (PDF). Blackhat. S2CID 14493263.
  16. ^ "Should You Get a Thermostat with Geofencing Technology?". General Heating & Air Conditioning. 2014-07-21. Retrieved 2018-12-07.
  17. ^ "Does the ecobee4 also have a built-in motion sensor?". ecobee Support. Retrieved 2018-09-21.
  18. ^ Whitney, Lance (February 12, 2014), "Google closes $3.2 billion purchase of Nest", CNET
  19. ^ a b c "Saving money with ecobee smart Wi-Fi thermostats | ecobee | Smart Home Technology". www.ecobee.com. Retrieved 2018-12-07.
  20. ^ a b c d e f g h i j "Energy Savings from the Nest Learning Thermostat: Energy Bill Analysis Results". Nest Labs, Inc., Feb. 2015, nest.com/-downloads/press/documents/energy-savings-white-paper.pdf.
  21. ^ a b c d e Asrish, Carlyn. Evaluation of the 2013–2014 Programmable and Smart Thermostat Program . The Cadmus Group, 9 Jan. 2015, www.cadmusgroup.com/wp-content/uploads/2015/06/Cadmus_Vectren_Nest_Report_Jan2015.pdf?submissionGuid=c8eda45b-2759-4a31-90e3-d2ecdb9001de.
  22. ^ Lee, Zachary (2022). "Unintended consequences of smart thermostats in the transition to electrified heating". Applied Energy. 322: 119384. doi:10.1016/j.apenergy.2022.119384. S2CID 249809288.
  23. ^ Tilley, Aaron. "How Hackers Could Use A Nest Thermostat As An Entry Point Into Your Home". Forbes. Retrieved 2018-12-07.
  24. ^ "Energy Use in Homes - Energy Explained, Your Guide To Understanding Energy - Energy Information Administration". www.eia.gov. Retrieved 2018-12-07.
  25. ^ "The Paris Agreement | UNFCCC". unfccc.int. Retrieved 2018-12-07.
  26. ^ "Social Impact | ecobee | Smart Home Technology". www.ecobee.com. Retrieved 2018-12-07.
  27. ^ "CNW | ecobee donates over 700 thermostats to Toronto Community Housing to improve sustainability and resident comfort". www.newswire.ca. Retrieved 2018-12-07.
  28. ^ "Smart Thermostat Incentives | San Diego Gas & Electric". www.sdge.com. Retrieved 2018-12-10.
  29. ^ "Smart Thermostats | Focus on Energy". www.focusonenergy.com. Retrieved 2018-12-10.
  30. ^ "Power Partner Thermostats". savings.austinenergy.com. 2013-04-24. Retrieved 2018-12-10.
  31. ^ "Smart thermostat rebate". www.pge.com. Retrieved 2021-09-29.
  32. ^ "Energy management for property managers". www.pge.com. Retrieved 2021-09-29.
  33. ^ "Smart Thermostat Rebate Program | The City of Naperville". www.naperville.il.us. Retrieved 2018-12-10.
  34. ^ "Energy Efficiency Programs | Entergy Mississippi, Inc". www.entergy-mississippi.com. Retrieved 2018-12-10.
  35. ^ Nest. "Support". Nest. Retrieved 2018-12-10.
Diagram of a HEPA (high-efficiency particulate air) filter
Reusable washable HVAC air filter

A particulate air filter is a device composed of fibrous, or porous materials which removes particulates such as smoke, dust, pollen, mold, viruses and bacteria from the air. Filters containing an adsorbent or catalyst such as charcoal (carbon) may also remove odors and gaseous pollutants such as volatile organic compounds or ozone.[1] Air filters are used in applications where air quality is important, notably in building ventilation systems and in engines.

Some buildings, as well as aircraft and other human-made environments (e.g., satellites, and Space Shuttles) use foam, pleated paper, or spun fiberglass filter elements. Another method, air ionizers, use fibers or elements with a static electric charge, which attract dust particles. The air intakes of internal combustion engines and air compressors tend to use either paper, foam, or cotton filters. Oil bath filters have fallen out of favour aside from niche uses. The technology of air intake filters of gas turbines has improved significantly in recent years, due to improvements in the aerodynamics and fluid dynamics of the air-compressor part of the gas turbines.

Do-it-yourself air cleaner are low-cost alternative to commercial portable air cleaners.[2]

HEPA filters

[edit]

High efficiency particulate arrester (HEPA),[3][4] originally called high-efficiency particulate absorber but also sometimes called high-efficiency particulate arresting or high-efficiency particulate arrestance, is a type of air filter. Filters meeting the HEPA standard have many applications, including use in clean rooms for IC fabrication, medical facilities, automobiles, aircraft and homes. The filter must satisfy certain standards of efficiency such as those set by the United States Department of Energy (DOE).

Varying standards define what qualifies as a HEPA filter. The two most common standards require that an air filter must remove (from the air that passes through) 99.95% (European Standard)[5] or 99.97% (ASME standard)[6] of particles that have a size greater than or equal to 0.3 μm.

Automotive cabin air filters

[edit]

The cabin air filter, also known in the United Kingdom as a pollen filter, is typically a pleated-paper filter that is placed in the outside-air intake for the vehicle's passenger compartment. Some of these filters are rectangular and similar in shape to the engine air filter. Others are uniquely shaped to fit the available space of particular vehicles' outside-air intakes.

The first automaker to include a disposable filter to keep the ventilation system clean was the Nash Motors "Weather Eye", introduced in 1940.[7]

A reusable heater core filter was available as an optional accessory on Studebaker models beginning in 1959, including Studebaker Lark automobiles (1959-1966), Studebaker Gran Turismo Hawk automobiles (1962-1964) and Studebaker Champ trucks (1960-1964). The filter was an aluminum frame containing an aluminum mesh and was located directly above the heater core. The filter was removed and installed from the engine compartment through a slot in the firewall. A long, thin rubber seal plugged the slot when the filter was installed. The filter could be vacuumed and washed prior to installation.

Clogged or dirty cabin air filters can significantly reduce airflow from the cabin vents, as well as introduce allergens into the cabin air stream. Since the cabin air temperature depends upon the flow rate of the air passing through the heater core, the evaporator, or both, clogged filters can greatly reduce the effectiveness and performance of the vehicle's air conditioning and heating systems.[8]

Some cabin air filters perform poorly, and some cabin air filter manufacturers do not print a minimum efficiency reporting value (MERV) filter rating on their cabin air filters.[citation needed]

Internal combustion engine air filters

[edit]
Used auto engine air filter, clean side
Used auto engine air filter, dirty side
Auto engine air filter clogged with dust and grime
Low-temperature oxidation catalyst used to convert carbon monoxide to less toxic carbon dioxide at room temperature. It can also remove formaldehyde from the air.

The combustion air filter prevents abrasive particulate matter from entering the engine's cylinders, where it would cause mechanical wear and oil contamination.

Most fuel injected vehicles use a pleated paper filter element in the form of a flat panel. This filter is usually placed inside a plastic box connected to the throttle body with duct work. Older vehicles that use carburetors or throttle body fuel injection typically use a cylindrical air filter, usually between 100 millimetres (4 in) and 400 millimetres (16 in) in diameter. This is positioned above or beside the carburetor or throttle body, usually in a metal or plastic container which may incorporate ducting to provide cool and/or warm inlet air, and secured with a metal or plastic lid. The overall unit (filter and housing together) is called the air cleaner.

Paper

[edit]

Pleated paper filter elements are the nearly exclusive choice for automobile engine air cleaners, because they are efficient, easy to service, and cost-effective. The "paper" term is somewhat misleading, as the filter media are considerably different from papers used for writing or packaging, etc. There is a persistent belief among tuners, fomented by advertising for aftermarket non-paper replacement filters, that paper filters flow poorly and thus restrict engine performance. In fact, as long as a pleated-paper filter is sized appropriately for the airflow volumes encountered in a particular application, such filters present only trivial restriction to flow until the filter has become significantly clogged with dirt. Construction equipment engines also use this. The reason is that the paper is bent in zig-zag shape, and the total area of the paper is very large, in the range of 50 times of the air opening.[citation needed]

Foam

[edit]

Oil-wetted polyurethane foam elements are used in some aftermarket replacement automobile air filters. Foam was in the past widely used in air cleaners on small engines on lawnmowers and other power equipment, but automotive-type paper filter elements have largely supplanted oil-wetted foam in these applications. Foam filters are still commonly used on air compressors for air tools up to 5 horsepower (3.7 kW). Depending on the grade and thickness of foam employed, an oil-wetted foam filter element can offer minimal airflow restriction or very high dirt capacity, the latter property making foam filters a popular choice in off-road rallying and other motorsport applications where high levels of dust will be encountered. Due to the way dust is captured on foam filters, large amounts may be trapped without measurable change in airflow restriction.[citation needed]

Cotton

[edit]

Oiled cotton gauze is employed in a growing number of aftermarket automotive air filters marketed as high-performance items. In the past, cotton gauze saw limited use in original-equipment automotive air filters. However, since the introduction of the Abarth SS versions, the Fiat subsidiary supplies cotton gauze air filters as OE filters.

Stainless steel

[edit]

Stainless steel mesh is another example of medium which allow more air to pass through. Stainless steel mesh comes with different mesh counts, offering different filtration standards. In an extreme modified engine lacking in space for a cone based air filter, some will opt to install a simple stainless steel mesh over the turbo to ensure no particles enter the engine via the turbo.

Oil bath

[edit]

An oil bath air cleaner consists of a sump containing a pool of oil, and an insert which is filled with fiber, mesh, foam, or another coarse filter media. The cleaner removes particles by adhering them to the oil-soaked filter media rather than traditional filtration, the openings in the filter media are much larger than the particles that are to be filtered. When the cleaner is assembled, the media-containing body of the insert sits a short distance above the surface of the oil pool. The rim of the insert overlaps the rim of the sump. This arrangement forms a labyrinthine path through which the air must travel in a series of U-turns: up through the gap between the rims of the insert and the sump, down through the gap between the outer wall of the insert and the inner wall of the sump, and up through the filter media in the body of the insert. This U-turn takes the air at high velocity across the surface of the oil pool. Larger and heavier dust and dirt particles in the air cannot make the turn due to their inertia, so they fall into the oil and settle to the bottom of the base bowl. Lighter and smaller particles stick to the filtration media in the insert, which is wetted by oil droplets aspirated there into by normal airflow. The constant aspiration of oil onto the filter media slowly carries most of the finer trapped particles downward and the oil drips back into the reservoir where the particles accumulate.

Oil bath air cleaners were very widely used in automotive and small engine applications until the widespread industry adoption of the paper filter in the early 1960s. Such cleaners are still used in off-road equipment where very high levels of dust are encountered, for oil bath air cleaners can sequester a great deal of dirt relative to their overall size without loss of filtration efficiency or airflow. However, the liquid oil makes cleaning and servicing such air cleaners messy and inconvenient, they must be relatively large to avoid excessive restriction at high airflow rates, and they tend to increase exhaust emissions of unburned hydrocarbons due to oil aspiration when used on spark-ignition engines.[citation needed]

Water bath

[edit]

In the early 20th century (about 1900 to 1930), water bath air cleaners were used in some applications (cars, trucks, tractors, and portable and stationary engines). They worked on roughly the same principles as oil bath air cleaners. For example, the original Fordson tractor had a water bath air cleaner. By the 1940s, oil bath designs had displaced water bath designs because of better filtering performance. [9]

Bulk solids handling filters

[edit]

Bulk solids handling involves the transport of solids (mechanical transport, pneumatic transport) which may be in a powder form. Many industries are handling bulk solids (mining industries, chemical industries, food industries) which requires the treatment of air streams escaping the process so that fine particles are not emitted, for regulatory reasons or economical reasons (loss of materials). As a consequence, air filters are positioned at many places in the process, especially at the reception of pneumatic conveying lines[10] where the quantity of air is important and the load in fine particle quite important. Filters can also be placed at any point of air exchange in the process to avoid that pollutants enter the process, which is particularly true in pharmaceuticals and food industries. The physical phenomena involved in catching particles with a filter are mainly inertial and diffusional[11]

Filter classes

[edit]

Under European normalization standards EN 779, the following filter classes were recognized:

Usage Class Performance Performance test Particulate size
approaching 100% retention
Test Standard
Coarse filters

(used as

Primary)

G1 65% Average value >5 μm BS EN779
G2 65–80% Average value >5 μm BS EN779
G3 80–90% Average value >5 μm BS EN779
G4 90%– Average value >5 μm BS EN779
Fine filters

(used as

Secondary)

M5 40–60% Average value >5 μm BS EN779
M6 60–80% Average value >2 μm BS EN779
F7 80–90% Average value >2 μm BS EN779
F8 90–95% Average value >1 μm BS EN779
F9 95%– Average value >1 μm BS EN779
Semi HEPA E10 85% Minimum value >1 μm BS EN1822
E11 95% Minimum value >0.5 μm BS EN1822
E12 99.5% Minimum value >0.5 μm BS EN1822
HEPA H13 99.95% Minimum value >0.3 μm BS EN1822
H14 99.995% Minimum value >0.3 μm BS EN1822
ULPA U15 99.9995% Minimum value >0.3 μm BS EN1822
U16 99.99995% Minimum value >0.3 μm BS EN1822
U17 99.999995% Minimum value >0.3 μm BS EN1822

European standard EN 779, on which the above table is based, remained in effect from 2012 to mid-2018, when it was replaced by ISO 16890.[12]

See also

[edit]

References

[edit]
  1. ^ "California Environmental Protection Agency - Air Cleaning Devices for the Home, Frequently Asked Questions" (PDF). California Environmental Protection Agency Air Resources Board. Retrieved 2016-12-14.
  2. ^ Holder, Amara L.; Halliday, Hannah S.; Virtaranta, Larry (2022). "Impact of do-it-yourself air cleaner design on the reduction of simulated wildfire smoke in a controlled chamber environment". Indoor Air. 32 (11): e13163. doi:10.1111/ina.13163. ISSN 1600-0668. PMC 9828579. PMID 36437679.
  3. ^ HEPA Company glossary of terms
  4. ^ Originally High Efficiency Particulate Arrestment - see thefreedictionary.com
  5. ^ European Standard EN 1822-1:2009, "High efficiency air filters (EPA, HEPA and ULPA)", 2009
  6. ^ American Society of Mechanical Engineers, ASME AG-1a–2004, "Addenda to ASME AG-1–2003 Code on Nuclear Air and Gas Treatment", 2004
  7. ^ Vwlarry (19 May 2009). "Nils Wahlberg and Nash - Salute To A Great Engineer And Unsung Automobiles".
  8. ^ "Dirty cabin air filter symptoms". FIRST BRANDS GROUP LLC. Retrieved 12 June 2024.
  9. ^ Peter, Paul. "Isolier Konzept". Retrieved 26 September 2022.
  10. ^ "Air filtration - Dust collectors".
  11. ^ "Solid Gas separation (cyclone - filtration)".
  12. ^ ISO 16890-1:2016(en) Air filters for general ventilation — Part 1: Technical specifications, requirements and classification system based upon particulate matter efficiency (ePM)
[edit]

 

An air handling unit; air flow is from the right to left in this case. Some AHU components shown are
1 – Supply duct
2 – Fan compartment
3 – Vibration isolator ('flex joint')
4 – Heating and/or cooling coil
5 – Filter compartment
6 – Mixed (recirculated + outside) air duct
A rooftop packaged unit or RTU

An air handler, or air handling unit (often abbreviated to AHU), is a device used to regulate and circulate air as part of a heating, ventilating, and air-conditioning (HVAC) system.[1] An air handler is usually a large metal box containing a blower, furnace or A/C elements, filter racks or chambers, sound attenuators, and dampers.[2] Air handlers usually connect to a ductwork ventilation system that distributes the conditioned air through the building and returns it to the AHU, sometimes exhausting air to the atmosphere and bringing in fresh air.[3] Sometimes AHUs discharge (supply) and admit (return) air directly to and from the space served without ductwork[4]

Small air handlers, for local use, are called terminal units, and may only include an air filter, coil, and blower; these simple terminal units are called blower coils or fan coil units. A larger air handler that conditions 100% outside air, and no recirculated air, is known as a makeup air unit (MAU) or fresh air handling unit (FAHU). An air handler designed for outdoor use, typically on roofs, is known as a packaged unit (PU), heating and air conditioning unit (HCU), or rooftop unit (RTU).

Construction

[edit]

The air handler is normally constructed around a framing system with metal infill panels as required to suit the configuration of the components. In its simplest form the frame may be made from metal channels or sections, with single skin metal infill panels. The metalwork is normally galvanized for long term protection. For outdoor units some form of weatherproof lid and additional sealing around joints is provided.[2]

Larger air handlers will be manufactured from a square section steel framing system with double skinned and insulated infill panels. Such constructions reduce heat loss or heat gain from the air handler, as well as providing acoustic attenuation.[2] Larger air handlers may be several meters long and are manufactured in a sectional manner and therefore, for strength and rigidity, steel section base rails are provided under the unit.[2]

Where supply and extract air is required in equal proportions for a balanced ventilation system, it is common for the supply and extract air handlers to be joined together, either in a side-by-side or a stacked configuration.

Air handling units types

[edit]

There are six factors for air handlers classifications and determine types of them, based on:

  1. Application (air handling unit usage)
  2. Air flow control (CAV or VAV air handlers)
  3. Zone control (single zone or multi zone air handlers)
  4. Fan location (draw-through or blow-through)
  5. Direction of outlet air flow (front, up, or down)
  6. Package model (horizontal or vertical)

But, the first method is very usual in HVAC market. In fact, most of the company advertise their products by air handling unit applications:

  1. Normal
  2. Hygienic
  3. Ceiling mounted

Components

[edit]

The major types of components are described here in approximate order, from the return duct (input to the AHU), through the unit, to the supply duct (AHU output).[1][2]

Filters

[edit]
A RTU viewed from inside with supply diffusers and return vent (center right)

Air filtration is almost always present in order to provide clean dust-free air to the building occupants. It may be via simple low-MERV pleated media, HEPA, electrostatic, or a combination of techniques. Gas-phase and ultraviolet air treatments may be employed as well.

Filtration is typically placed first in the AHU in order to keep all the downstream components clean. Depending upon the grade of filtration required, typically filters will be arranged in two (or more) successive banks with a coarse-grade panel filter provided in front of a fine-grade bag filter, or other "final" filtration medium. The panel filter is cheaper to replace and maintain, and thus protects the more expensive bag filters.[1]

The life of a filter may be assessed by monitoring the pressure drop through the filter medium at design air volume flow rate. This may be done by means of a visual display using a pressure gauge, or by a pressure switch linked to an alarm point on the building control system. Failure to replace a filter may eventually lead to its collapse, as the forces exerted upon it by the fan overcome its inherent strength, resulting in collapse and thus contamination of the air handler and downstream ductwork.

Hot (heat A.K.A furnace) and cold (air conditioning) elements

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Air handlers may need to provide hot air, cold air, or both to change the supply air temperature, and humidity level depending on the location and the application. Such conditioning is provided by heat exchanger coils within the air handling unit air stream, such coils may be direct or indirect in relation to the medium providing the heating or cooling effect.[1][2]

Direct heat exchangers include those for gas-fired fuel-burning heaters or a refrigeration evaporator, placed directly in the air stream. Electric resistance heaters and heat pumps can be used as well. Evaporative cooling is possible in dry climates.

Indirect coils use hot water or steam for heating, and chilled water or glycol for cooling (prime energy for heating and air conditioning is provided by central plant elsewhere in the building). Coils are typically manufactured from copper for the tubes, with copper or aluminum fins to aid heat transfer. Cooling coils will also employ eliminator plates to remove and drain condensate. The hot water or steam is provided by a central boiler, and the chilled water is provided by a central chiller. Downstream temperature sensors are typically used to monitor and control "off coil" temperatures, in conjunction with an appropriate motorized control valve prior to the coil.

If dehumidification is required, then the cooling coil is employed to over-cool so that the dew point is reached and condensation occurs. A heater coil placed after the cooling coil re-heats the air (therefore known as a re-heat coil) to the desired supply temperature. This process has the effect of reducing the relative humidity level of the supply air.

In colder climates, where winter temperatures regularly drop below freezing, then frost coils or pre-heat coils are often employed as a first stage of air treatment to ensure that downstream filters or chilled water coils are protected against freezing. The control of the frost coil is such that if a certain off-coil air temperature is not reached then the entire air handler is shut down for protection.

Humidifier

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Humidification is often necessary in colder climates where continuous heating will make the air drier, resulting in uncomfortable air quality and increased static electricity. Various types of humidification may be used:

  • Evaporative: dry air blown over a reservoir will evaporate some of the water. The rate of evaporation can be increased by spraying the water onto baffles in the air stream.
  • Vaporizer: steam or vapor from a boiler is blown directly into the air stream.
  • Spray mist: water is diffused either by a nozzle or other mechanical means into fine droplets and carried by the air.
  • Ultrasonic: A tray of fresh water in the airstream is excited by an ultrasonic device forming a fog or water mist.
  • Wetted medium: A fine fibrous medium in the airstream is kept moist with fresh water from a header pipe with a series of small outlets. As the air passes through the medium it entrains the water in fine droplets. This type of humidifier can quickly clog if the primary air filtration is not maintained in good order.

Mixing chamber

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In order to maintain indoor air quality, air handlers commonly have provisions to allow the introduction of outside air into, and the exhausting of air from the building. In temperate climates, mixing the right amount of cooler outside air with warmer return air can be used to approach the desired supply air temperature. A mixing chamber is therefore used which has dampers controlling the ratio between the return, outside, and exhaust air.

Blower/fan

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Air handlers typically employ a large squirrel cage blower driven by an AC induction electric motor to move the air. The blower may operate at a single speed, offer a variety of set speeds, or be driven by a variable-frequency drive to allow a wide range of air flow rates. Flow rate may also be controlled by inlet vanes or outlet dampers on the fan. Some residential air handlers in USA (central "furnaces" or "air conditioners") use a brushless DC electric motor that has variable speed capabilities.[1] Air handlers in Europe and Australia and New Zealand now commonly use backward curve fans without scroll or "plug fans". These are driven using high efficiency EC (electronically commutated) motors with built in speed control. The higher the RTU temperature, the slower the air will flow. And the lower the RTU temperature, the faster the air will flow.

Multiple blowers may be present in large commercial air handling units, typically placed at the end of the AHU and the beginning of the supply ductwork (therefore also called "supply fans"). They are often augmented by fans in the return air duct ("return fans") pushing the air into the AHU.

Balancing

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Un-balanced fans wobble and vibrate. For home AC fans, this can be a major problem: air circulation is greatly reduced at the vents (as wobble is lost energy), efficiency is compromised, and noise is increased. Another major problem in fans that are not balanced is longevity of the bearings (attached to the fan and shaft) is compromised. This can cause failure to occur long before the bearings life expectancy.

Weights can be strategically placed to correct for a smooth spin (for a ceiling fan, trial and error placement typically resolves the problem). Home/central AC fans or other big fans are typically taken to shops, which have special balancers for more complicated balancing (trial and error can cause damage before the correct points are found). The fan motor itself does not typically vibrate.

Heat recovery device

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A heat recovery device heat exchanger may be fitted to the air handler between supply and extract airstreams for energy savings and increasing capacity. These types more commonly include for:

  • Recuperator, or Plate Heat exchanger: A sandwich of plastic or metal plates with interlaced air paths. Heat is transferred between airstreams from one side of the plate to the other. The plates are typically spaced at 4 to 6mm apart. Heat recovery efficiency up to 70%.
  • Thermal wheel, or Rotary heat exchanger: A slowly rotating matrix of finely corrugated metal, operating in both opposing airstreams. When the air handling unit is in heating mode, heat is absorbed as air passes through the matrix in the exhaust airstream, during one half rotation, and released during the second half rotation into the supply airstream in a continuous process. When the air handling unit is in cooling mode, heat is released as air passes through the matrix in the exhaust airstream, during one half rotation, and absorbed during the second half rotation into the supply airstream. Heat recovery efficiency up to 85%. Wheels are also available with a hygroscopic coating to provide latent heat transfer and also the drying or humidification of airstreams.
  • Run around coil: Two air to liquid heat exchanger coils, in opposing airstreams, piped together with a circulating pump and using water or a brine as the heat transfer medium. This device, although not very efficient, allows heat recovery between remote and sometimes multiple supply and exhaust airstreams. Heat recovery efficiency up to 50%.
  • Heat pipe: Operating in both opposing air paths, using a confined refrigerant as a heat transfer medium. The heat pipe uses multiple sealed pipes mounted in a coil configuration with fins to increase heat transfer. Heat is absorbed on one side of the pipe, by evaporation of the refrigerant, and released at the other side, by condensation of the refrigerant. Condensed refrigerant flows by gravity to the first side of the pipe to repeat the process. Heat recovery efficiency up to 65%.

Controls

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Controls are necessary to regulate every aspect of an air handler, such as: flow rate of air, supply air temperature, mixed air temperature, humidity, air quality. They may be as simple as an off/on thermostat or as complex as a building automation system using BACnet or LonWorks, for example.

Common control components include temperature sensors, humidity sensors, sail switches, actuators, motors, and controllers.

Vibration isolators

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The blowers in an air handler can create substantial vibration and the large area of the duct system would transmit this noise and vibration to the occupants of the building. To avoid this, vibration isolators (flexible sections) are normally inserted into the duct immediately before and after the air handler and often also between the fan compartment and the rest of the AHU. The rubberized canvas-like material of these sections allows the air handler components to vibrate without transmitting this motion to the attached ducts.

The fan compartment can be further isolated by placing it on spring suspension, neoprene pads, or hung on spring hangers, which will mitigate the transfer of vibration through the structure.

Sound attenuators

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The blower in the air handler also generates noise, which should be attenuated before ductwork enters a noise-sensitive room. To achieve meaningful noise reduction in a relatively short length, a sound attenuator is used.[1] The attenuator is a specialty duct accessory that typically consists of an inner perforated baffle with sound-absorptive insulation. Sound attenuators may take the place of ductwork; conversely, inline attenuators are located close to the blower and have a bellmouth profile to minimize system effects.

Major manufacturers

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See also

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References

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  1. ^ a b c d e f 2008 ASHRAE handbook : heating, ventilating, and air-conditioning systems and equipment (Inch-Pound ed.). Atlanta, Ga.: ASHRAE American Society of Heating, Refrigerating and Air-Conditioning Engineers. 2008. ISBN 9781933742335.
  2. ^ a b c d e f Carrier Design Manual part 2: Air Distribution (1974 tenth ed.). Carrier Corporation. 1960.
  3. ^ "Air Handling Units Explained". The Engineering Mindset. 26 September 2018.
  4. ^ HVAC, experts. "how air handling unit work?".

 

Frequently Asked Questions

Ductwork can contribute to AC noise due to several factors, such as loose or poorly secured ducts that rattle or vibrate, rapid airflow through the ducts causing a whooshing sound, and expansion and contraction of metal ducts leading to popping noises.
Improperly sized ductwork can lead to increased noise levels because if the ducts are too small, air moves through them at a higher velocity, creating more turbulence and noise. Conversely, oversized ducts might not fit properly in their spaces, leading to rattling or banging.
The material of the ductwork affects sound transmission; for example, metal ducts tend to be noisier than flexible or fiberglass-lined ones because they conduct vibrations more easily. Using insulated or lined ducting can help reduce these sounds.
Yes, regular maintenance helps identify and fix issues like loose connections or debris buildup that could amplify noise. Ensuring proper installation and securing of ducts during maintenance checks also minimizes potential sources of unwanted sounds.