Building Management Systems (BMS) is one of the most powerful tool in the building engineering services, which is primarily used to monitor and control electro-mechanical systems, extra low voltage systems, elevators, lighting etc. Building management system also ensures efficient utilization of resources, energy efficiency, improved comfort and safety to the user.
Main components of BMS include system software, Direct digital controllers and sensors which all are inter-connected through communication network. The output values from the field sensors and different switch states are monitored through the input ports (Digital/Analog) of DDC over a pre-defined time interval. Any change in the values/states will be immediately reported to the DDC. The direct digital control analyses these changes in values/states through the pre-written PID (Proportional Integral Derivative) program in the DDC and required control action would be initiated through Analog/Digital output ports of DDC. DDC also have communication ports like Ethernet, RS 485 through which DDC can communicate with other third-party devices for monitoring and controls through protocols like BACnet, MODBUS, LON Works, M-Bus, KNX, OPC etc. BMS software also will have a graphical user interface (GUI) installed in a computer through which the user can monitor and control the systems remotely.
Now a days, almost all the equipment and systems used in the building engineering industry comes with communication ports or hardwired potential free contacts, to enable the user to interface with BMS, to remotely monitor and control the systems.
From my little experience in varied projects, I found that most of the facilities do not relay much on the building management system for its operation and is merely used only as a tool for recording and investigation, may be because of the lack of understanding about the systems or limited system capability or due to design deficiencies.
Here in this topic, I would like to share some of my views and basic minimum features required to be implemented in the building management systems. Some of the common parameters/points pertaining to various systems that could be interfaced with BMS for monitoring and controls are listed below
Electrical Systems :
- HT/LT Breaker Off/On/Trip Status
- Utility Energy Meter Readings
- Transformer Temp. Monitoring
- Diesel Generator Run Status
- Diesel Generator ‘s Engine Parameters
- Diesel Tank Level status
- Un-interruptible Power Supply (UPS) Parameters
- Lighting On/Off Controls
- Variable Frequency Drives
HVAC Systems :
- Chiller & Heat Pump
- Chilled Water & Hot Water Pumps
- Chilled Water Pressurization Unit
- Temperature of Chilled Water Lines
- Chilled Water Control Valves (2 Way & Modulating Valves)
- Chemical Dosing System
- Cooling Tower Water Level Monitoring
- Ambient Temp. & Humidity
- BTU Meters
- Variable Air Volume Boxes (VAV)
- Space Temperatures,
- LPG Detectors, Carbon Dioxide and Carbon Monoxide Detectors
- AHU/TFA/Vent. Fans
Plumbing, Fire Protection & Water Treatment Systems :
- UG & OH Water Tank Levels
- Feed Water Pumps, Transfer Pumps & Sump Pumps
- Water Treatment Plant & RO Plant
- Sewage Treatment Plant
- Hydro-pneumatic Systems
- Water Meter Readings
- Fire Protection System Supply Healthiness Monitoring
- Fire Protection System Pressure
- Fire Protection Pumps Healthiness
- Diesel Pump Battery Voltage
- Hot Water Tank Temperature
- Diesel Pump’s Diesel Tank Level
- pH Analyser, Hardness Analyser, Conductivity Analyser readings
Extra Low Voltage Systems :
- CCTV Common Alarm from DVR / NVR
- Common Alarm from Access Control System
- Power Supply Monitoring of Access Control System
- Fire Alarm System Alarm Status
- Fire Alarm System Supervisory Alarm Status
- Fire Alarm System Common Fault
- Fire Alarm System Supply Healthiness Status
- AV System Common Fault Status
Other Systems :
- Elevator Run & Floor Status
- Elevator Trip/Common Fault
- Elevator Emergency Alarm Status
While designing BMS system, implementation of some of the smart strategies reduces the complexity of the system as well as the overall cost. Most of the designers simply add hard points in addition to the soft points already available in the equipment which will add only cost to the user, but no value additions. Therefore, it is suggested that BMS designer also should specify the IO points required to be included in the equipment and the type of physical connectivity required rather simply specify that the equipment should have open protocol connectivity or PFC contacts. Also, before the final selection of the equipment, BMS designer has to carefully examine equipment data sheet for correctness of data given. Few of the points to be kept in mind while designing BMS are listed below
- Reliable and continuous supply availability is the prime importance in electrical systems. Hence, by monitoring the incoming and outgoing feeder’s energy meter/multi-function digital meters, we could identify if the supply is available and the bus is energized. For a normal facility, the above arrangement will be more than sufficient which will take away the need of PFC Contacts for monitoring On/Off status of breakers.
- Most of the main distribution panel will have load management systems for which PLC is inevitable. Status of all the breakers will be readily read out from the PLC through RS 485 communication interface, which avoids the need of additional PFC Contacts/IO Points in DDC/Wiring etc. which again saves the cost. I would suggest installing PLC in Main LT Panel for reading the status and interface with DDC through soft integration (Through RS 485 Network) rather running numerous cables.
- All the Chillers/Heat Pumps will have inbuilt temperature sensors for monitoring the temperature and hence it is not necessary to add additional temperature sensors which may not be 100% accurate. We could fetch these values through soft interface with these systems in Modbus/BacNet protocols.
- Run Status of pumps also to be taken from mechanical side by installing DP Switches across pumps rather relaying on electrical starters as starter will always show On status when switch on but sometimes pump may not be really running in the field due to some mechanical failures
- Instead of integrating the Main Fire Alarm Panel fully into BMS, it is better to assign 2 control relays, one for supervisory monitoring and one for fire alarm monitoring in the firs alarm system. By monitoring the status of these control relays, BMS operator could come to know the main 2 status. Upon activation of the same, detailed investigation would be possible after looking at Main Fire Alarm Control Panel and take necessary control action can be initiated. By doing so, the cost of BMS interface card required to be installed in the Fire Alarm Control Panel and the number of soft points in the BMS Software also could be saved.
- Availability of electric supply at the fire protection panel is of prime importance rather monitoring the LT breaker On/Off/Trip status. By incorporating Line Voltage Monitoring (LVM) relay and monitoring the output of it, we could monitor the electric supply availability and fault status, if any.
Apart from the integration of the above parameters/points, the BMS software should be customized to depict and process the data in a facility management perspective. Some of the specific function which are very much required in my view are briefed below.
- Report generation of energy consumption values from utility meters on a daily cut-off hour. Let us say @ 12:00 Midnight
- Trending of parameters and status in HVAC Systems, Hot Water Systems, Ambient Conditions etc.
- Trip/Fault and Stop status of equipment to be popped up in the BMS Workstation with an Audio-Visual Alarm.
- Automatic printing of alarms and events through a printer attached to BMS Workstation.
- Preventive maintenance schedule alarms based on the operating hours of the equipment.
Above functionalities in the software would enable the facility management team to analyze the energy usage pattern, variation of parameters at different operating conditions, resulting proper planning, efficient and optimal utilization of energy and resources.
Finally, effective use of BMS depends on the accuracy of information available from the system and hence proper commissioning and validation of the system is very much crucial for the proper functioning and operational data analysis.
