Integrating BAS, electrical systems

10/03/2013


Electrical systems integration

Figure 2: Data can be gathered from network-enabled power meters into the BAS platform for historical performance data. Courtesy: Environmental Systems DesignMany types of modern electrical equipment are microprocessor-based, meaning they can easily collect and act on data in real time. Sending data to the BAS enables users to optimize each system it supports to provide effective maintenance protocols. Typical electrical equipment that can be integrated into the BAS includes: 

Power meters: Because one cannot manage what is not measured, the smart power meter is a vital part of BAS-electrical system integration (see Figure 2). For example, sustainable design rating systems, such as U.S. Green Building Council’s LEED system and Abu Dhabi’s Estidama Pearl system, encourage separately metering power consumption by load type (i.e., lighting, HVAC, plug loads, and IT loads). The BAS becomes the central location for gathering and monitoring these data.

Figure 3: BAS monitoring of critical power distribution equipment, such as generators, can provide alerts in advance of potential problems. Courtesy: Environmental System DesignGenerators: Often required by code for life safety purposes or used to back up critical systems in mission critical facilities, the generator has its own control system that ensures it runs as intended. Because there are so many things that can go wrong with a generator—from high temperatures to low fuel supply—the systems are typically monitored remotely with a status panel located at the fire command center and/or building engineer’s office. If also tied into the BAS, an electronic message can be sent in a timely fashion to the building engineer, who may be located remotely—both when the generator is running smoothly and when it has a problem that needs immediate attention (see Figure 3). The BAS can also be used to document and alert personnel when the next maintenance testing is required. 

Transfer switches: The transfer switch connects life safety and critical loads to the alternate power source upon loss of utility power. Via the BAS, the position of the transfer switch can be remotely monitored (see Figure 4). It can be also be remotely controlled for testing the emergency system, for sending a signal to load shed to avoid overloading a generator, or for switching loads to the generator for demand response. 

Figure 4: Switchgear can contain multiple devices to be monitored by BAS, including PLC automation, power meters, surge protective devices, and even circuit breakers with communicating trip units. Courtesy: Environmental System DesignUPS: Any downtime on a UPS makes the connected critical loads more susceptible to power quality issues and in danger of going offline due to a sudden power failure. By integrating a UPS with the BAS, quick action can be taken by immediately notifying personnel when adverse conditions, such as high temperature, are experienced in the room or when a sudden UPS failure occurs. 

Surge protection devices (SPDs): In addition to reliability, power quality is important in critical facilities. Metal-oxide varistors (MOVs) are the most common element used in SPDs to divert electrical surges away from critical loads. However, MOVs do fail over time while performing their intended function. Because these devices are not normally checked after installation, connecting them to the BAS to remotely monitor the quantity of surges diverted allows preventive replacement toward the end of their life to prevent the next surge from causing severe electrical system damage.

Transformers: Fans can be integrated into transformer housings to allow more power capacity from its standard rating by cooling the transformer with forced air. A controller is able to start the fan when the value of the transformer winding temperature indicates a load approaching its standard rating. Using the BAS to monitor temperature and fan status, and comparing it to the measured transformer power consumption ensures the fans are working as designed so the transformer can be loaded to its extended capacity. 

Lighting controls: A lighting control system can—and often should be—its own purposely built specialty subsystem. If complex lighting system strategies are required, the lighting control system may handle them more effectively than the BAS. For example, when daylight-dimming controls are specified, algorithms are set within the lighting control system to optimize this functionality. However, the BAS can monitor and make basic operational changes to the lighting control system for normal daily operations or coordinate with the mechanical system’s schedule during off-hour occupancies. The BAS can also enhance HVAC energy efficiency by allowing HVAC systems to change setpoints based on occupancy sensor data received from the lighting control system. 

Shades: Motorized shades on the building’s interior or exterior can be programmed to function according to the BAS time clock or the computed position of the sun relative to the building, instead of occupants manually opening and closing each one. Keeping shades down in an empty building in the summer can significantly reduce solar heat gain, while outdoor views and daylight are not required by occupants. Automatically operating shades to balance reduced heat gain and increased daylighting can contribute to increased worker satisfaction and productivity gains. 

Figure 5: Energy generation from renewable resources, such as these photovoltaic modules integrated into a building’s curtain wall, can be monitored and tracked by the BAS to optimize power production. Courtesy: Environmental System DesignPhotovoltaics: Some building owners install photovoltaic panels to optimize power generation. BAS monitoring is crucial to verifying that these panels are working optimally (see Figure 5). Soiling and shading can determinately and exponentially reduce the amount of power generated from a string of photovoltaic modules. By monitoring the photovoltaic array output power and coordinating it with historical weather data of a similar date and time or current weather conditions (i.e., estimating cloud coverage based on exterior photocell data), it is possible to calculate approximately what the output should be on a given day and compare that with real-time activity. When proper maintenance or action isn’t taken to ensure the system is kept in absolutely optimal condition, the estimated payback may double from the initially calculated amount and may not make this sustainable investment economically feasible.

Fire alarm system: Fire alarm system requirements are dictated by codes and authorities having jurisdiction, which generally discourage low-level integration with the BAS in favor of a dedicated specialty fire alarm system. However, fire alarms can be interfaced easily with the BAS to share summary zone alarms to provide supplemental monitoring. This can allow the BAS to send alarms by e-mail or text message. A BAS can even push emergency information to digital signage to alert occupants and provide egress assistance. 

Security system: As with fire alarm systems, security systems are often provided as dedicated specialty subsystems with unique features and functions. However, when integrated into the BAS, the security system has the capability to create additional efficiencies and enhance security as well. Card access systems can maintain a count of occupants in a space when configured to require users to card out when leaving. This occupant count can be used to optimize building ventilation rates. In case of emergency, when there is a fire at a specific building location, the security cameras in that vicinity could be programmed to pop up on the security officer’s screen. Also, if there is a chiller malfunction, the chiller alarm could cause the camera in the mechanical room to appear on the officer’s screen. 

Conclusion

Integrating electrical systems into an existing BAS can promote operational efficiencies, optimize maintenance staff effectiveness, and leverage fault diagnostics, while using historical data to set a baseline for it all. Taking advantage of existing BAS features, such as trending, alarming, web-based graphics, and analytics, can present new opportunities for integrating electrical equipment and systems when moving to a single, unified BAS platform. The result will be truly integrated, high-performance buildings.


Mar is senior associate at Environmental Systems Design and a member of the Consulting-Specifying Engineer editorial advisory board. Knight is senior associate at Environmental Systems Design.


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