Buildings have become incredibly smart. On the leading edge, advanced sensor and automation technologies have made sci-fi-like conveniences possible. A contactless elevator might automatically sense who has boarded and remember where the occupants need to go at certain times of day. An office with no assigned desks may direct arriving workers to an open parking space and an empty desk via an app, sense who is seated where, and adjust the lighting and temperature to their individual preferences.
Flashy futuristic concepts like these are now achievable — and exciting — but not necessarily cost-effective for the average facility to deploy. Much of the best sensor technology currently available actually operates behind the scenes. Facilities teams and building managers are intimately familiar with the systems they empower and streamline, while the average occupant reaps the benefits and is never the wiser.
The nervous system of a smart building is made up of hundreds or even thousands of sensors, carefully positioned around rooms, inside HVAC units, within the plumbing system, and attached to power lines. The intelligence provided by these sensors is what powers the time, cost, and effort-saving automations that we associate with “smart” buildings — and what empowers your team to make smarter decisions about schedules, setpoints, seasonal budgets, and beyond.
You may wonder: If I’m looking to improve the intelligence in my building, where should I start? Here are a few suggestions for sensor types, applications, and purposes that will bring your building up to a competitive standard for today’s ever-rising bar. This list is by no means exhaustive, but should provide a good baseline for the most critical data-gathering functions in a modern smart building.
What Types of Sensors Do I Need?
From a data standpoint, a commercial building is a complex business with diverse needs. The right combination of sensors in an integrated network is worth much more than the sum of its parts, with significant value for predictive maintenance, operational efficiency, downtime reduction, environment stabilization, and occupant comfort.
- Pressure Sensors: AHUs, chillers, and boilers all need pressure sensors to monitor pressure in ducts, condensers, and evaporators, and water supplies. High or low pressure readings are an invaluable predictor of leaks, pump failures, locked rotors, clogs, and other mechanical failures. They’ll provide proof of flow and can be used as a control point for things like fan speeds or air flow through duct work. You’ll also be able to monitor building zone pressure to regulate the inflow of outside air.
- Humidity Sensors: Many facilities have precise environmental humidity requirements — laboratories, libraries, manufacturing plants, et cetera — due to the materials or processes housed within them. Even in office and residential buildings, however, humidity regulation is a critical component of occupant comfort. Humidity sensors within air handling units help you determine how much outside air you need to introduce into the building and keep you timely in your response when RH is exiting the desired range.
- Temperature Sensors: Few sensors see more widespread use in HVAC than temperature sensors, which play crucial roles in virtually all units. Your temperature sensors will monitor duct temperatures, chilled and heated water loops, inside and outside air temperatures, and more. They also provide input for functions such as fan or valve control and flow regulation.
- Current Sensors: These are essential for tracking the run status of all fan and pump motors. A current sensor provides proof of function and eliminates the need to manually check each unit to see if it’s running. If current is flowing, the unit is working.
- CO2 Sensors: The best way to reduce costs on constant conditioning of outside air is to track CO2 for Demand Control Ventilation (DCV) and either recirculate inside air or introduce fresh air, as needed.
- Power Meters: A power meter in a chiller or boiler helps with the efficient management of load shedding agreements and detection of mechanical problems (when, for example, power usage is excessive).
- Flow Meters: Water flow (both return and supply lines) must be monitored in boilers, chillers, or cooling towers to provide proof of flow and measure usage. BTU meters are a version that combine the functions of flow meters and temperature sensors to trend energy usage and detect inefficiencies (which may result from clogs, excessive ice, humidity changes, and other malfunctions).
- Current Switches: These devices track amperage (current) that passes through a conductor. The format of the switch will vary, depending on the application. They’re useful in monitoring the status and run times of circuits, motors, and equipment while also detecting mechanical failures.
- Current Monitoring Relays: A relay can provide a layer of protection for mechanical equipment that may overload under excessive currents. A load-switching relay can easily handle resistive currents for lighting fixtures (e.g. incandescent, LED, fluorescent), and capacitive currents (such as power supplies and loudspeakers). Inductive loads, as with fans, transformers, and electromotors, require careful attention to maximum loads to prevent damage to the relay.
- Current Transducers: A transducer modifies an electrical input to a different kind of signal either passively or actively. These are used for monitoring load trending data and the controls and status of the equipment (such as a fan or pump) receiving the altered signal.
- Indoor Air Quality (IAQ) Room Sensors: IAQ compliance requires careful monitoring of the indoor climate with sensors that track RH, CO2, temperature, and VOC outputs. It’s also critical to track these things for the general comfort and safety of occupants and to protect sensitive materials or equipment. Such units can be wall or ceiling-mounted, and fitted to be controlled by hand or remotely via the BMS or even a wireless application. While it is possible to install individual sensor types for each aspect of IAQ, the best and most cost-effective approach would be to install a network of all-in-one style sensors with the capability to monitor every aspect (or as many as possible) from a single device in each location.
- Occupancy Sensors: When it comes down to it, building management is about keeping a building functional and cost-efficient for the people and processes housed within. This is most achievable with an accurate data model on space usage — where, how long, and in what numbers people are residing in the building — to guide the setpoints and schedules in your system. Some systems can be turned down or off, even during times the building is in use, if certain areas are less active or perhaps not active at all. Data from occupancy sensors will guide planned maintenance outages, field service of equipment, energy management for peak hours or off hours, and more.
Where (and Why) Should I Use Them?
Your sensors and meters will be integrated throughout the building, from individual flow meters within the valves of a boiler’s hot water loop to a simple wall thermostat in the lobby. Each sensor acts like a nerve that connects HVAC, power, lighting, and other systems to the BMS for a complete picture of unit health and performance. It’s critical that sensors are installed within the following units and systems for an optimal set of control points and insights.
- Air Handling Units (AHU): The AHU will use an array of pressure, humidity, temperature, current, and CO2 sensors to keep operations efficient and help you optimize setpoint automations and strategic cycle scheduling. Pressure sensors keep track of filter status, whereas RH, CO2, and temperature sensors should be positioned periodically in all ducts. A current sensor monitors each fan motor.
- Water Cooled Chillers: The chilled water loop and condenser water loop will need temperature sensors to help you better control the valve that determines circulation speeds. Return and supply lines use flow meters to provide proof of function and gauge pressure sensors to enable the BMS to calculate differential pressure between supply and return. A current sensor is needed for all pump motors to detect on/off status, locked rotors, and functionality.
- Cooling Towers: Use a flow meter on both the supply and the sewer drain to reduce your costs. The meter helps you detect how much water went down the drain by showing the difference between the volume of water initially supplied and the water discharged into the sewer. As much as 50-60% could be lost to evaporation. Proving this will save on utility charges that assume all water supplied was also sent into the sewer system. Immersion temperature sensors are a useful control input for fan rotation, and as with other units, current sensors should track all pumps and fans to ensure they’re working.
- Variable Air Volume (VAV) Boxes: Temperature sensors provide the needed input to control dampers, fan speeds, or power to suit the demands of the space. VAV boxes with heating and cooling coils will also use temperature sensors to control those points. A current sensor monitors the fan motor (and thus the fan status).
- Boiler Systems: The boiler requires a complex network of sensors to track power, pressure, current, temperature, and flow. The power meter assists in regulating load shedding processes as well as detecting issues in the boiler pump motor. Current sensors also provide proof of function for the pump motor. Gauge pressure sensors monitor the supply and return lines for total pressure (and allow for calculation of differential pressure). Temperature sensors track the heated water loop to help you determine pump speed and control the valve for water recirculation with efficiency. BTU flow meters are a valuable input for trending boiler efficiency and measuring the total energy it consumes. Overconsumption can indicate compressor cycling issues, clogs, or malfunctioning pumps.
- Current Monitoring System: An optimal energy bill depends upon efficient management of your energy consumption. Modern power and current monitoring systems must provide more than a whole-building view. Individual breakouts of performance and trends at each circuit enable you to pinpoint energy consumption, detect inefficiencies or problems, and predict electrical or equipment-based maintenance needs. It’s best to meter as many lighting circuits, fans, motors, pumps, and equipment power supplies as is feasible. An ideal meter can accurately monitor 50, 100, or potentially even more circuits — you won’t need a matching number of meters to make individual monitoring possible.
- All Occupied/Sensitive Interior Spaces: Wall-mounted and ceiling-mounted IAQ and occupancy sensors can be easily fitted for every room or hall that will be occupied or contain climate-sensitive materials or equipment. Keep precise track of the humidity, temperature, and CO2/VOC levels in these areas to detect potential blockages or failures in the ventilation system and to respond quickly to increased needs in times of high occupancy. In many applications, these sensors will also be necessary to help you maintain compliance with codes for the space.
Every Building Needs a Brain
Building automation technology has a long history, dating back to Warren Johnson’s “electric tele-thermoscope” at the State Normal School in 1883 (it rang a bell at set temperatures to alert firemen to open or close heating dampers).
Today’s buildings are far more sophisticated — or at least, they can be — with a robust sensor network that provides precise data for code compliance, energy optimization, troubleshooting, and predictive maintenance. The building management system (BMS) is the brain, but it is limited by the extent of the nervous system. Your sensors work together from end-to-end to keep you in tune with the building’s health and provide better control.
— Contributed by Veris.
