Fault detection and diagnostics (FDD) is the process of identifying and analyzing malfunctions or failures within a building’s systems to detect and diagnose faults as early as possible. Early detection minimizes the impacts of downtimes, prevents future failures, and improves overall system performance. FDD is crucial for maintaining the reliability and efficiency of a building’s HVAC system.
How Do FDD Systems Work?
FDD is typically achieved using sensors, monitoring systems, and diagnostic algorithms. These tools work together to continuously monitor the performance of the system and detect any abnormal patterns that may indicate a fault. The diagnostic algorithms then analyze the collected to identify the specific fault and provide recommendations for how to address it.
One of the key benefits of FDD is that organizations can proactively identify and address potential issues before they lead to costly downtime or equipment damage. Too often, building owners, maintenance staff, and systems integrators work within a reactionary model, which often follows these steps:
BMS alarm sounds for a VAV
VAV unit inspected
Maintenance request created
Repair or replacement made
This reactionary model works but is inefficient. How long was the VAV malfunctioning before the alarm? How much energy was lost before? How long as it been affecting occupant comfort levels? How much time is required for all steps? How much energy, money, and comfort are sacrificed during downtime? These questions represent the issues inherent in the reactionary model.
FDD sees the problem before the inefficiencies start by using analyzing data from fault trends to predict failures before the actual alarm sounds. If a VAV is consistently running below specification, FDD can flag the activity as consistent with a failing terminal unit. That gives maintenance longer lead times and shortens downtimes.
Diagnostic algorithms like this basic one, move through a series of steps to detect and identify solutions to equipment failures.
FDD Systems Lower Energy Costs
With the growing emphasis on energy efficiency, FDD is becoming increasingly important as a tool for improving overall system performance and reducing energy consumption. Recent studies show that between 5% – 30% of commercial building energy is wasted due to problems associated with controls (Deshmukh 2018). So, FDD offers a massive opportunity to increase energy savings by finding faults faster.
One of the most common types of FDD systems used in buildings is Building Energy Management Systems or BEMS. These computer-based systems monitor and control the HVAC, lighting, and other building systems to optimize energy efficiency. BEMS often use temperature sensors to monitor the performance of an HVAC system and detect when the system is not working as efficiently as it should. The diagnostic algorithms then analyze this data and identify the specific problem, such as a clogged filter or malfunctioning compressor.
Predictive Analytics
Another important aspect of FDD is the use of predictive analytics. Predictive analytics uses historical data and statistical models to predict when a system is likely to fail. This enables building operators and maintenance staff to take proactive measures to address potential issues before they lead to costly downtime or equipment damage. Predictive analytics can be used in a wide range of systems, including industrial equipment, vehicles, and even wind turbines.
Furthermore, the use of predictive analytics can enable organizations to take proactive measures to address potential issues before they lead to a complete system failure.
Improving System Performance
While FDD is typically associated with detecting and diagnosing equipment failures, building operators can use it to improve system performance. By identifying and addressing inefficiencies in a system, organizations can improve overall system performance and reduce energy consumption. For example, an FDD system in an HVAC system might identify that the system is running at a higher temperature than necessary, resulting in increased energy consumption. By addressing this issue, the organization can reduce energy consumption and improve overall system performance.
In conclusion, FDD is an important tool for maintaining the reliability and efficiency of various systems. By detecting and diagnosing faults early on, organizations can take steps to address the problem before it leads to costly downtime or equipment damage.
If COVID-19 taught facilities managers and building engineers anything, it’s the importance of proper design and maintenance of air and water systems for stopping the spread of pathogens. But aside from Coronavirus, there are other deadly bugs we need to control if we are to create healthy environments for building occupants. Legionnaires’ disease is one of them.
What is Legionnaires’ disease?
Legionnaires’ disease is a serious respiratory illness caused by the bacterium Legionella pneumophila. It is typically contracted by inhaling small droplets of water that contain the bacteria and can occur when water vapor or mist from a contaminated source is inhaled into the lungs. Facility water and cooling systems can become a source of Legionella bacteria if they are not properly designed, installed, and maintained.
Outbreaks are common with facilities like hotels, vacation rentals, medical facilities and cruise ships. Public hot tubs, for example, present ideal conditions for Legionella pneumophila and are common sources for outbreaks. About 1 in 10 people who contract Legionnaires’ disease will die due to complications from the illness. In health care facilities, the mortality rate jumps to 1 in 4, according to the CDC.
Controlling the Spread
To minimize the risk of Legionnaires’ disease growing within water or cooling systems, it is important to follow best practices for the design, installation, and maintenance of these systems.
Water Cooler System Design. Design water and cooling systems to minimize the risk of Legionella growth and proliferation. This includes using materials that are resistant to corrosion and scale formation, as well as designing the system to allow for proper water flow and circulation.
Regular Maintenance. Regularly clean and maintain water and cooling systems to prevent the buildup of Legionella bacteria. This includes flushing the system to remove any sediment or debris and using water treatment chemicals to kill bacteria and prevent the growth of biofilm.
Temperature Control. Maintain your water and cooling systems at a temperature too high for Legionella bacteria to grow. This typically means keeping the water temperature preferably above 124°F (51°C), and below 68°F (20°C). (Source: CDC)
Control Your pH Levels. Legionella bacteria thrive in water with a pH between 6.0 and 8.5. To prevent the growth of these bacteria, it is important to maintain the pH of the water in the system outside this range. Studies show that a pH of 9.6 prevents the bacteria’s growth in cooling towers. (Source: Water Research).
Disinfection. Regularly disinfect water and cooling systems to kill any Legionella bacteria that may be present. This can be done using chemicals such as chlorine or monochloramine or by using UV light to kill the bacteria.
Risk Assessment. It is important to regularly assess the risk of Legionella growth in water and cooling systems. Implement appropriate control measures as needed. This may include regularly testing the water for the presence of Legionella bacteria and implementing additional measures such as water treatment or increased cleaning.
In addition to these measures, it is important to educate employees and building occupants about the risks of Legionnaires’ disease and how to prevent it. This may include providing information about the signs and symptoms of the disease and reminding people to wash their hands frequently to reduce the risk of infection.
Overall, the key to preventing Legionnaires’ disease from water and cooling systems is to properly design, install, and maintain these systems. By following these best practices, you can significantly reduce the risk of this serious and potentially life-threatening illness.
Buildings are responsible for a significant chunk of emitted green house gases (GHGs) into the atmosphere. Therefore, they’re a leading contributor to global warming. In the U.S., buildings account for 40% of all U. S. primary energy and its associated GHG emissions. While these stats appear bleak, they actually represent a positive when it comes to FMs and owners. Because property owners and managers helm the ship of the Built Environment, they have the power to steer decarbonization efforts in the right direction. By adopting smart technology and building automation, property owners can significantly contribute to GHG reduction while saving money and futureproofing their investments.
With building decarbonization, small changes can make a big difference. Automating your after-hours HVAC program is an easy first step to reducing your property’s carbon footprint. You don’t need to take out a loan to invest in automation tech either. Online tools like cloud-based after-hours HVAC apps are inexpensive and simple to integrate with your existing BMS.
Cut Mistakes, Cut Waste
While after-hours request programs vary, the standard process works like this: the tenant fills out a work request for after-hours air conditioning or heating. Staff members record the request. The building engineer programs the HVAC to fulfill the request. The air con/heating is delivered at the require day and time. The property manager invoices the tenant at the end of the month.
Every step in this manual request process is an opportunity for errors to crop up. Forgotten emails, data entry mistakes and missed change requests are all more likely with a manual process. Mistakes cost time and energy, whether its extra lighting, access gates, lift rides or added HVAC service itself.
After-hours HVAC booking apps replace these manual step with wireless technology and network connections. Tenants create requests via a mobile or desktop app. The system then interfaces with the building’s BMS to schedule the request. The tenant, time and date are automatically logged, and the BMS delivers heating and air con on the requested days. By automating these steps, you cut out the wasted energy and help lower your carbon footprint.
Push Buttons vs. Cloud-Based Apps
Push button systems for activating HVAC service eliminate some, but not all, of the manual steps. They’re designed to deliver service as requested, giving tenants easy access to and control over HVAC operation. However, their openness can be a liability. Since anyone within the building can request service, savings from push button controls are often undermined by their public access.
There are no guards against everyone (ex. maintenance or cleaning staff) from accessing controls. So, unauthorized access can lead to unaccounted and wasted energy use. It’s also easy for occupants to “hit the button” minutes before leaving the room or floor, resulting in wasted energy from heating and cooling unoccupied spaces.
After-hours HVAC apps reduce energy waste by limiting access to the platform. In a cloud-based system, only authorized users can create HVAC requests. And the system records both the request and the requester. So owners always know who requests services. Plus, tenants can re-schedule and cancel bookings from anywhere there’s an internet connection. This helps save energy by eliminating empty room heating and cooling.
Data Equals Decarbonization
Automation goes hand-in-hand with data. Today’s smart sensors, IoT devices, machine learning, AI, digital twins, and BMS integration all point to the eventual integration of every building systems. In the near future, fire systems will “talk” with access systems to track occupants during an emergency. Access systems will work in tandem with HVAC systems to adjust heating and cooling demands based on occupancy levels. Building management systems will connect to utility providers to shift energy usage during peak demand. Such interoperability is already evolving, but it requires data to work properly.
By automating your HVAC requests, you can collect data on how and when your tenants are requesting HVAC services and use it to conserve energy. For example, you can identify seasonal trends and make targeted improvements and retrofits for specific zones of your property. Automation puts you in a better position to transition your property into a smart building and futureproof your assets.
Fire protection systems are one of the most complex and ubiquitous structures within facilities today. They contain many parts intertwined with other building components. For example, emergency lighting and smoke detectors wire into your electrical system. Fire pumps and hydrants hook up to your water mains. Fire alarms connect to your building’s access system to automatically unlock exterior doors.
Your HVAC system is also closely coupled to your fire protection equipment, and its maintenance and condition can directly impact the safety of your inhabitants and the extent of damage to your property.
1. Ductwork
Your system’s ductwork distributes conditioned air throughout the building. But during a fire, such distribution is unwanted. As temps rise and smoke builds, your HVAC’s return ductwork can carry smoke, toxic gases, and superheated air throughout other areas. This spreads the fire and puts occupants in danger. Even worse, supply side ductwork can actually “feed” a localised fire with fresh oxygen, increasing the temperature and property damage.
During a fire, smoke is the number one killer. In fact, most fire deaths are not caused by burns, but by smoke inhalation. Therefore, controlling its spread is safety 101. Plus, smoke can often emit from sources besides an open flame. Burnt toast or microwave popcorn could result in smoke rolling through an entire office floor. This could cause a panic and dangerous stampede to exits. So, any fire safety plan should also include the perception of fire itself as a real threat to life and property.
Duct smoke detectors can help. These devices reside within your ductwork where they detect smoke moving throughout your HVAC system and initiate pre-programmed actions. For example, one of your HVAC fan motors overheats and produces smoke. Once activated, the duct detector could turn on an exhaust fan, close a damper, shut down automation systems, signal an alarm and/or cut power to the fan motor itself.
2. Fire and Smoke Dampers
Fire dampers are another critical way your HVAC systems aid your facility’s fire protection system. Dampers are essentially air valves that shut off airflow in the event of a fire. They’re normally installed at any point where your system’s ductwork passes through a wall, floor or other fire-rated partition. The idea is to close off HVAC ventilation for any area where a fire exists. So, locating them within a fire-rated wall, for example, retains the integrity of the wall even if the ductwork falls away or is damaged by fire.
There are two basic types of dampers: fire and smoke. Fire dampers are usually triggered by a physical device such as a fusible link. Once the temperature rises above a specific point, the fusible link will melt and trigger the closing of the fire damper. As its name suggests, the damper’s main function is to stop fire from spreading through the ductwork.
Smoke dampers are part of the smoke suppression system. They typically connect to fire alarm systems, which trigger the dampers to close and prevent smoke transference. There are smoke/fire combination dampers as well.
Most fire codes require fire and smoke dampers to be actuated and tested every few years, depending on the facility type. Make sure you know your fire code and test that your dampers are physically working, installations are compliant and any replacements are compatible with your system.
3. AHU Support and Location
In the event of a fire, your alarm system should shut down any air handling units (AHUs) within the affected area or site wide. Again, the purpose is to contain the movement of smoke and air, and your AHU is the central place where this happens. However, operation isn’t the only consideration.
AHUs are large, heavy pieces of equipment weighing several tons depending on the size of the system. They’re also loud; that’s why they’re usually located within mechanical rooms and building rooftops. In multi-storey properties, these behemoths can become a danger to building inhabitants. During a fire, walls and floors weaken under intense heat, and those supporting heavy AHUs can give way quickly. While there’s little you can do to predict heat intensity during a fire, you can ensure your AHUs are appropriately located and that building floors are rated for their weight and size.
Conclusion
To function correctly, building systems must work together. It’s not enough just to tackle preventative maintenance for one system and ignore another. Their intertwining requires awareness of how changing one system affects another. Your HVAC system is no different. Upkeep and maintenance of it directly affects the effectiveness and efficiency of your fire protection system.
The COVID pandemic increased awareness and use of relatively new decontamination methods for medical facilities. In addition to standard surface cleaning and disinfection, hospital managers employ vaporized hydrogen peroxide (VHP) systems within negative pressure rooms to eliminate SARS-CoV-2. Sometimes referred to as “Deprox,” these systems distribute a mixture of hydrogen peroxide and water within a room. The mixture is small enough to decontaminate areas that are too difficult or impossible to clean by hand.
However, VHPs must work in conjunction with HVAC systems to be safe and effective, and most functional descriptions put strict limits on an HVAC’s operation during decontamination. Use the following information to guide your design when connecting to VHPs.
HP Vapor vs Aerosol Systems
There are two methods for dispersing hydrogen peroxide (H2O2) for airborne disinfection. One is vapor phase hydrogen peroxide (VPHP) and the other is aerosolised hydrogen peroxide (aHP). The main difference being the size and concentration of the hydrogen peroxide as it leaves the system. VPHP systems produce much smaller particles and at higher concentration than aHPs. They are much closer to a gas than aHPs, which are more of a “fog” ranging from 5 and 20 μm in size.
Exposure Limits
Both VPHPs or aHPs require some downtime for operation and room exposure levels to return to normal. Decontamination cycles may take up to three hours to complete. Exposure to hydrogen peroxide vapor can be harmful, resulting in irritation to the eyes, nose and throat. The OSHA standard for permissible exposure limits to H2O2 is 1 part per million parts of air (ppm) averaged over an eight-hour work shift.
Functional Descriptions
Include these sections when writing a FD that includes VPHP or aHP for negative/positive pressure rooms.
Room Modes—Room modes include isolation, deprox and standby. During the deprox process, the HVAC system should be turned off and dampers closed to ensure the VHP system works effectively.
Closing Dampers—When switching from standby or isolation to deprox mode, factor in a lag time to allow dampers to fully close. For example:
If the room is switched to deprox mode, the deprox LED will flash on and off for 75 seconds whilst the room dampers are driving closed. Once the 75 seconds have passed, the LED will be enabled.
Velocity Pressure Setpoint—Include a deprox pressure setpoint when setting duct velocity pressure points.
If the room is put into deprox mode, the velocity pressure setpoint is reduced to the deprox velocity pressure setpoint (To be determined at time of commissioning).
Smoke and Fire Detectors
Particles from VPHP or aHP can set off fire and smoke detectors. Consider the implications for your HVAC system. Since HVAC systems are normally integrated into fire systems to ensure proper exhaust of smoke, a false alarm may affect your system.
Colder weather often brings spikes in COVID-19 and influenza cases. With this in mind, we should continue promoting vaccinations, mask wearing, social distancing, surface cleaning and handwashing inside your buildings. However, we shouldn’t forget about our HVAC systems; they also play an important role in stopping the spread of COVID. In fact, if not properly managed, these systems significantly contribute to virus transmission. To properly protect your facility’s visitors and workers this winter, prep your HVAC system the right way by following these guidelines.
Use an Air Dilution Strategy
Viruses like SARS-CoV-2 travel within tiny liquid droplets expelled through our coughs and sneezes. These droplets can range in size from larger particles (5-10 μm) to smaller ones (less than 5 μm). Larger droplets fall to the ground quickly, while smaller aerosols linger in the air much longer. Their hang time presents both a problem and an opportunity. The problem is that these tiny airborne particles can easily cluster together, becoming concentrated within small areas like offices. Concentration makes them more potent and contagious.
However, these clusters are also easily dispersed or “diluted” by adequate air flow. So, an effective dilution strategy is to keep a good mixture of air within every part of your building. It’s a similar idea to running vs standing water. Which is safer to drink? Here are some tips for an effective dilution strategy.
Increase Outside Air Flow
Increasing outside air flow helps dilute recirculated interior air and break up any high concentration particle clusters. The CDC recommends the following tips when introducing outside air flow into your interior spaces:
Disable demand-controlled ventilation (DCV) systems
Open outdoor air dampers beyond minimum settings
When conditions allow, open windows and external doors
Use stand-alone fans inside windows
Set indoor AC unit fan speeds to “on” instead of “auto”
Run your systems longer, 24/7 if possible
CAVEAT: Increasing outside air flow during very cold or very warm weather raises your energy costs and puts added stress on your system to maintain set points. So, some actions may only be practical during milder weather. Another concern is the introduction of pollutants and pollen into the building. For occupants with allergies, outside air could contain possible health risks from contaminants. Increasing outside air flow during very cold or very warm weather raises your energy costs and puts added stress on your system to maintain set points. So, some actions may only be practical during milder weather.
Another concern is the introduction of pollutants and pollen into the building. For occupants with allergies, outside air could contain possible health risks. Most higher-rated filters can catch pollen (which is between 5 -11 μm) so introduction of outside air through fans, open windows and doors pose the greater risk.
Target 5 Air Changes Per Hour
Your air change rate (ACH) is a measure of how often you replace the air within a space. However, ACH is a bit misleading since one cycle doesn’t equate to 100% removal. In fact, it takes longer than you’d expect to vacate any contaminants from a room.
“When we change air in a room,” explains Lance Jimmieson, of Jackson Engineering, “we’re not magically taking out all of the air that’s there and replacing it with fresh air. It comes in, mixes and turns over, and typically mixes between perimeter and center zones. So, we’ve got to remove it.”
Jimmieson advises targeting a minimum of 5 air changes/hr (12 cycles) and bases his recommendation on CDC data (Table B.1). “Even with ten air changes an hour, i.e. every 6 minutes, it’s still going to take half an hour to get rid of any traces of an aerosol in the room, so air change rates need to be relatively high,” he explains.
The choice of filter matters when trying to arrest droplets containing small contaminants like viruses. ASHRAE recommends a minimum MERV-13 grade or better for commercial buildings. MERV-13 through 16 can achieve a 95-99% average removal efficiency for particles from 0.3 to 1.0 μm.
High Efficiency Particulate Air (HEPA) filters have an even higher performance, capturing 99.97% of particles with a size of 0.3 μm. However, their superior efficiency creates more pressure drop in your system, which will reduce airflow rates and therefore system performance.
CAVEAT Pressure drops from upgrading filters can have a significant impact on your HVAC system. In fact, most managers and owners will find it too difficult or impossible to retrofit their HVAC systems with HEPA filters without a costly or significant redesign. This hurdle is why ASHRAE recommends using portable systems with HEPA filters. Also, higher grade filters are costly and single use, so expect an uptick in operating costs.
Consider UV Germicidal Irradiation
Ultraviolet germicidal irradiation (UVGI) systems use short wavelength UV-C light to kill viruses and bacteria before they’re distributed by your ventilation system. UVGI systems for HVAC are usually mercury-based lamps or LEDs. As viruses pass through the HVAC system, the lamps “inactivate” any viruses captured by high efficiency filters or that move through the AHU.
UVGI lamps contribute to air sterilization, especially where outside air flow is restricted and/or dilution efforts are insufficient. However, UV-C does have limits. Jimmieson notes that one critical restriction that’s often overlooked is particle size. “By and large, a good rule of thumb is that if you’ve got a particle size that is bigger than 5 μm then you’re going to struggle to nuke that particle with UV light.”
It’s a fact that has implications for your filtration system, since low efficiency filters allow particles greater than 5 μm to pass through. If those larger particles are hosting viruses, then they may not be neutralized by your UVGI. “You really want to position the UVGI system downstream of a good quality filter to take the lumps out of the air,” Jimmieson recommends.
