Exploring Integration Opportunities with Airflow Measurement Stations

Written by Darryl DeAngelis published in the Journal of Building Automation

The increasing requirement for intelligent cities and energy-efficient facilities with enhanced security systems fuels the Building Automation Systems (BAS) industry. The global BAS market size was valued at USD 86.8 billion in 2022, and it is projected to reach USD 148.6 billion by 2027, growing at a compound annual growth rate (CAGR) of 11.4%.1 

Thermal dispersion airflow measurement stations with BACnet communication protocols address the industry's need for data integration and operational transparency. Advanced BAS systems use extracted data for decision-making, trend analysis, interoperability, and issue resolution. The advantage of using a BACnet airflow sensor is that it allows for more actionable data with the option of using analog for the local controller.

Integrating airflow data into the BAS provides the flexibility to control, monitor, and trend historical events for outside air, supply and return air, and exhaust systems. Thermal dispersion offers advantages over other technologies, such as inherent temperature measurement, multiple measurement points, and shorter distances from disturbances. System integrators can fully utilize airflow measurement station data with built-in BACnet digital communication protocols for monitoring and system control. There are also application-specific advantages, like the fan array, where you can individually measure the flow and control each fan independently. The system integrator uses industry software to execute all necessary field device setups, monitor, and control connected devices, reducing commissioning time and eliminating errors. 

Facility managers and operators gain valuable equipment operation and performance insights without leaving their desks. Access to all device data enables timely fault detection and aids in diagnostics. The BTL-certified device "Protocol Implementation Conformance Statement," or "PICS," lists and describes the airflow measurement station functionality of the product: example shown above, Table F-2. PICs are available from BACnet International or the manufacturer's website. During the initial BAS setup, obtaining granular airflow information is possible with individual sensing node data points. Monitoring every node offers several advantages for efficiency, control, and optimization as the controller will compensate for airflow changes. For instance, if the airflow decreases, the fan will automatically increase to maintain the rate. This declining trend can lead to a continuous increase in fan speed over time, using more energy without understanding the reason for the decline. With individual sensor node data, you can evaluate the airflow profiles and trends of the decline, evaluate potential causes, and take action to resolve the problem. It could be anything from damage to a damper blade, rag in the damper on the sensor node, mechanical failure, dirty filters, fouling or heat exchangers, etc.

Integrators often use only average outputs to simplify information exchange, as shown in the image above: Example of Typical Average Outputs. However, more detail is valuable for operational efficiency, fault detection, energy usage, maintenance management, and problem-solving. You can have up to 16 sensor nodes, each with individual values. Within the PIC statement, each value noted for each sensor node: AV 21, AV 22, AV 23, AV 24, AV 25, AV 26, etc., provides real-time point temperature and airflow rate values. You can create a visual profile model of thermal and flow with the individual points. Since the system temperatures and flow rates are often changing, trends in performance can be recorded in more detail.

By setting up the system to request sensor node values via BACnet, you can monitor individual nodes and still control them by the average measured value. The probe's sensor nodes provide an airflow and temperature measurement with NIST traceable calibration capable of communicating information with the BAS or Cloud monitoring systems—multiple sensing points to produce more accurate velocity and temperature measurements. Adding optional humidity sensing provides control based on relative humidity, dew point, or enthalpy. Using this technology in converging airstreams or across energy-exchanging components can provide energy performance insight and act as an airside energy meter. The relative humidity and enthalpy can be more accurately calculated with multiple temperature and flow measuring points. The example image below could represent an outdoor air intake where the sun impacts the temperature in an upper hood. Alternatively, it could be a convergence of two airstreams or downstream of a split 2-stage cooling coil common in RTUs— having more data results in better control decisions for energy efficiency.

Using BACnet fosters a culture of data collection, leading to improved insight into buildings' airflow system operation. Analyzing data and system performance over time helps detect maintenance issues, schedule diagnostics, and identify faults, making buildings smarter. Facility managers, service technicians, 3rd party data management, TAB, and Commissioning agents, to name a few, can use networked field devices to troubleshoot or adjust parameters. The system-level controllers can read airflow measurement device performance data to make HVAC equipment more efficient. A well-integrated BAS can analyze historical airflow data, identifying patterns that hint at potential issues. Proactive maintenance becomes a reality, preventing costly downtimes and enhancing system longevity. BAS integration via BACnet allows for customized airflow adjustments based on occupancy and improved scheduling. This dynamic control ensures occupant comfort while conserving energy. Standardized communication facilitates smoother data exchange between airflow measurement stations and the BAS. Integrating airflow device data enables enhanced operational insight and management.

Digital communicating airflow measurement stations feature standard analog outputs and can be field configured to 0-5/0-10 VDC or 4-20mA for flow, temperature, or alarm. Low flow alarms can be field set and enabled. Airflow measurement systems with optional BACnet MS/TP and BACnet Ethernet / IP network cards provide more flexibility, allowing local control via analog and a separate data channel for monitoring and trending, parameter changes, overrides, alarms, etc.

An app can display the sensor system's operation locally and provide additional information on settings, individual node values, and other diagnostic data.

Airflow Measurement Stations' seamless integration with BACnet presents opportunities to revolutionize how building environments are managed. Data from various airflow measurement stations can be provided through BACnet to many different platforms used to improve building operations. By navigating the challenges and leveraging the opportunities offered by this integration, we can create and manage indoor environments for a sustainable future.

ABOUT THE AUTHOR

Darryl DeAngelis is the Director of Business Development for EBTRON, with over 30 years of experience in the HVAC industry. He holds a B.S. in Marine Engineering from the Massachusetts Maritime Academy and is a LEED AP. A 20-year ASHRAE member is active in ASHRAE technical and standard committees, including 11, 62.1, 90.1, 180, and 207. He is chair of TC 7.7 Testing and Balancing and a voting member 62.1 Ventilation subcommittee. Darryl is a participating voting member in ASTM and a member of ISIAQ and I2SL. Darryl holds four HVAC-related patents.

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