Understand the Basic concept of BMS system

Understand the Basic concept of BMS system 

What is a BMS or Building Management System?
In a nutshell, BMS otherwise called as BAS or building automation is computer-based control system which reduces the manpower, automate the system, and saving the energy consumption in building by monitoring and controlling the mechanical and electrical equipment in modern day buildings or any industrial plants.
Not only that but BMS helps to
·        Increasing productivity.
·        Increasing the equipment lifetime and better performance.
·        Identifying the systems faults earliest.
·        Managing the hotel tenants in an effective manner.
Nowadays any modern-day buildings built with BMS to support facilities management to accomplish the maintenance and save the energy in building from one place of computers.

Any BMS software or system must provide the following facility to the operator

• Monitoring and controlling connected equipment in the building. 

• The alarm should be a popup in operator workstation for any critical faults in the system. 

• Any types of equipment on, off status and alarm should be logged or stored in PC to retrieve later.

• Scheduling the equipment to on and off automatically by preset time. 

• User interface graphics should be available in order to visualize the field equipment to monitor for BMS operator easily. 

BMS or BAS system monitor and/or controls the following system in buildings

• HVAC (Heating, Ventilation, and Air-conditioning or all supply and exhaust fans, ACs etc). 
• Lighting control system. 
• Fire alarm system. 
• Firefighting system. 
• Security control system. 
• CCTV system.
• Lift control system. 
• Pumping system. 
• Water tanks level. 
• Irrigation system. 
• Electrical meters.
• Water Leak detection system.
• Split units. 
• UPS units.
• VFD-Variable frequency drives. 
• VRF/VRV-Variable refrigerant flow or volume (both are same but each term copyrighted by a different vendor) 
• And any other system which has provision for BMS to control and monitor. 

Main components of the BMS System

1.     Hardware
·        DDC-Direct digital controller
·        Sensors
·        Actuators
·        Cables to connect sensors, actuators to DDC.
·        HMI display-Human machine interface.
·        PC Workstation
·        Server to save the large database.

2. Software

3. Networking protocols

·        Programming or configuration tools.
·        Graphics or User interface.
·        TCP/IP– Transfer control protocols/Internet Protocol.
·        BACnet– Building automation controller network-ASHRAE
·        Modbus
·        LONworks
·        CANbus
·        and numerous protocols available.
Don’t worry about the various protocols, this all protocol doing the same task to transfer data from one device to another device. 

BMS System architecture in the modern-day building

However, BMS System controls and monitor all the electrical and mechanical systems in buildings from BMS workstation or HMI(Human Machine Interfaces), but not directly because each system has its own functionality and unique purpose like

• HVAC System helps to facilitate and provide comfortable and healthy air conditioning to tenants.
• The lighting control system which has a variety of lightings in buildings that needs to be on and off effectively and save energy while tenants not available.
• CCTV helps to facility management to secure the building
• Access control systems may also be used to control access into certain areas located within the interior of buildings.
• A fire alarm system is the life safety system to warn people by audio and visual to protect their lives from fires, smoke, carbon mono oxide and other toxic elements for the human.
• In case of fire Firefighting system aims to protect human life and property in the building by a large amount of water and other gas.
• UPS is to provide to the uninterrupted power supply in the building for electrical equipment.
• Pumping system used in the building to pump the water to the required area.
• still tons of systems evolved in the modern-day building to facilitate the people.

All systems have its own controllers and processing system due to the different functionality of each system.

So BMS controllers or device designed for controlling and monitoring the HVAC system and other small systems and integrate all other systems through dedicated networking protocols like BACnet, Modbus etc.

General BMS System architecture with Levels

• Management Level: This is the front end for operator and engineer used to visualize the graphics for controlling and monitoring the systems which have computer workstation, server, web browser, printers.

• Automation Level: BMS Router and other main controllers connected in building network integrate third-party system and connect BMS devices

• Field devices Level: this is Level where BMS controllers connect to field systems sensors, actuators, and other panel circuits to monitor and control.

Simple Real Time example for BMS System

Any modern day building client provides huge specifications for BMS System, whereas here I am going to take simple requirement to monitor and control the sequence of Air Handling unit. 

Let us see below the requirement of the client to monitor and control the sequence in BMS System.

Before we go detailed about how to design the BMS System for the requirement. let us see some basics components of the AHU-Air handling unit.

AHU is an HVAC system which consists of the duct, fan, filter, cooling coil, heating element,humidifier, sound attenuators, dampers, valves and many more to regulate the air into the room by heating, ventilation and conditioning to distributes the conditioned air through the building and returns it to the AHU and also called as centralised AC in modern-day building.

Duct – It is the collection of metallic tubes that interconnected and distributes the heated/cooled air to the required rooms.

In order to monitor the duct air temperature in fresh, return and supply duct. we have to install the duct temperature sensor in the duct.

Fan Motor– Blower is used to circulate the air from fresh and return duct to the supply duct.

This fan motor controlled and monitored by the separate electrical panel by the designed electrical circuit with help of electrical relay and contactor and providing an option to BMS system to

• On/Off the fan.

• Monitor the fan running status.

• Monitor the Fan motor overload fault status and many more.

Filter– It is one of the main components in AHU to prevent the dust and dirt particles to enter in the AHU.

When the AHU fan motor started, the fresh outside air supplied into the duct where filter components used to filter the dirty particles continuously and in order to monitor the filter extreme dirty condition,

DPS switch is used to install across the filter and provide a signal to BMS when the filter gets dirty(technically DPS-Differential pressure switch will send the signal to BMS when the pressure reached more than pre-set across the filter and this same function can be used to monitor the fan status.

Now we Read about How DPS used to monitor fan and filter status

Heating/Cooling element- It is used to cool or heat the water that entered in the coil so that air in the duct can be heated or cooled based on the user requirement.

Either heating or cooling water enters into the coils are controlled and monitored by valves on the pipe with help of valve actuator.

Dampers- An HVAC damper is a movable plate, located in the ductwork, that regulates airflow and directs it to areas that need it most.

Damper opening and closing position controlled electrically with the help of damper actuators and this actuators have terminal for control from BMS and terminal to monitor the feedback of position.

System Description:

The variable speeds Air Handling Units are used to serve air conditioning need for all area of buildings

The Air Handling Unit comprises:

·        Variable Speed Supply Fan

·        Chilled water coil with the 2-Way modulating control valve

·        Duct mounted supply air pressure sensor

·        Outdoor & re-circulating Air modulating damper

·        Carbon dioxide sensor.

·        Supply and Return Air temperature sensors

·        Supply air differential pressure switch

·        Differential pressure switches for 2 set of filters

System Monitoring and Alarm:

      ·        Software alarms shall be generated at the operator workstation whenever the run status of the supply fan (with differential pressure switch) does not match the current command state.
·        A failure alarm shall occur when the run status of the load shows no operation and the load has been commanded to be on.
·        An advisory alarm shall occur when the run status of the load shows operation and the load has been commanded to be off. All alarms shall be recorded in an alarm log for future review. Provide 15 seconds (adjustable) time delays before generating an alarm.

The sequence of Operation

a. Auto Mode:

When the AHU start is in AUTO mode (i.e. selector switch installed in the MCC must be in Auto Position), the unit is started and stopped from the BMS via a time schedule or BMS override command. When the start for the AHU is initiated, the control program residing in the controller follows the following sequence

Start-Up:

The following sequence follows with a preset time interval per interlock equipment start-up:
1) Check Supply fan trip signal – Normal State
2) Supply Air Damper –Open Position
3) Outdoor Air Damper –Open Position
4) Return Air Damper – Open Position

5) Once the above conditions are satisfied, AHU is enabled to start in Auto mode or using a plant enable button on the graphics in manual mode by the operator. Once enabled, BMS will automatically command supply fan to start.

6) Supply Fan shall start and it’s associated Interlock equipment in sequence. Through the signal from the Diff. Airflow Switch, if airflow is detected, the System will continuously run, if No airflow is detected by the DP Switch, the Supply Fan will de-activated and send an Alarm to the DDC – for “No Airflow” and shut down the whole system including its associated interlocks. If the Air flow switch signal is proved ‘ON’ then BMS will enable control loops.

b. Shutdown Mode:

When the shutdown command for the AHU is initiated, the control program residing in the controller follows the following sequence.
1) Send Stop command to stop the supply fan
2) The outdoor air, return and supply air damper move to close
3) Move chilled water valve to close position

c. Manual (Hand) Mode:

When the AHU is the manual mode, the fans are started and stopped from the AHU control panel. Other control except for fan on/off control shall function as per the Auto mode.

d. Fire / Smoke Mode:

Fire condition is determined by the Fire Alarm Control Panel. AHU will automatically shutdowns the whole system with associated interlocks.

AHU Control

The control program, on the feedback of air handling unit operation, initiates the control algorithm. This algorithm consists of three controls. Each temperature, pressure and ventilation control has its own control loop. The pressure control loop is used to modulate the speed of the supply air fan hence supply air flow. The control loops design to function as per following explanation:

a. Temperature Control loop:

The supply air temperature installed in the duct will relay the measured signal (temperature) to the DDC controller, the DDC controller compares this signal with set-point (adjustable by the operator from BMS central) and generates an analog output to the 2-way modulating cooling valve. Based on the difference between the two values, a proportional-integral program will determine the percentage of the cooling coil valves opening to achieve the desired condition. The default set-point value for the supply air temperature is 13ºC (Adjustable).

b. Pressure Control loop:

The supply air pressure sensor shall be installed in the duct  will relay the measured signal (static pressure) to the DDC controller, the DDC controller compares this signal with the set-point (adjustable by the operator from BMS central) and generates an analog output to the variable frequency drive (VFD) of the supply air fan. Based on the difference between the two values, a Proportional-Integral program will determine the percentage of the fan speed to achieve the desired pressure. The set-point value for the supply air pressure for each AHU shall be adjusted.

c. Ventilation Control loop:

Demand control ventilation employs return air carbon dioxide controlling strategy.

A single carbon dioxide sensor sense carbon dioxide concentration in the return air duct and sent to the DDC controller, the DDC controller compares the signals with return air carbon dioxide concentration (Default carbon dioxide level difference value 400 ppm).

Then DDC controller generates an analogue output to the outside air dampers and returns air damper to modulate, based on the difference between the values, the Proportional integral program will determine the percentage of the modulation of outdoor and return air dampers.

Minimum outdoor air quantity shall be governed either by building pressurization requirement (Input from Building differential pressure sensor) or 20% of the Maximum outdoor requirement of the AHU.

Alarms:

The following minimum alarms shall be generated on BMS
1) Filter Dirty Alarm: This is generated when pressure drop on each filter exceeds the set value to indicate dirt accumulate at filters.
2) Fan Trip Alarm: A normally open “NO” volt free contact at the MCC panel when closed will generate an alarm at the BMS indicating that the fan is tripped
3) Fan Fail: In case the supply air fan fails to start or if the differential pressure switch across

supply fan is not giving the signal according to the command due to any reason then alarm shall be generated. In case of a fan fail alarm on the BMS, due to abnormal behaviour, the DDC controller will latch the alarm. The operator has to acknowledge (reset) the alarm on the BMS once the trouble has been checked and removed. The operator shall not be able to start the AHU until the alarm s acknowledged and reset.

4) Temperature High & Low: Temperature HIGH and LOW alarms shall be generated if the supply/return air temperature rises above or falls below the supply /return air temperature alarm limit.

List of Input and output points are required for the above-discussed sequence of operation for AHU

Some basic terms of digital electronics

• Analog Input: Analog inputs can come from a variety of sensors and transmitters. You can measure a whole bunch of different things. The job of the sensor or transmitter is to transform that into an electrical signal. Here are a few of the things you can measure with analog sensors:

·        Level

·        Flow

·        Distance

·        Viscosity

·        Temperature

• Digital Input: It allows a microcontroller to detect logic states either 1 or 0 otherwise called as VFC-Volt free contact.
• Analog Output: In automation and process control applications, the analogue output module transmits analogue signals (voltage or current) that operate controls such as hydraulic actuators, solenoids, and motor starters.
• Binary Output: it is nothing but relay output from the controller to trigger on and off any equipment.

Now its time to choose the DDC controllers based on the above input and output point list.

Any BMS controllers manufacturer must have the basic controllers types of analogue input-output, binary input, and output controllers either dedicated controllers or mixed of all types in a single controller.

For the above applications, we need to choose controllers that should accommodate 17 AI, 6 BI, 5 AO, and 1 BO(Note that temperature and humidity are two different analogue input)

Once controllers are designed, we need to calculate power load for each controller (available in controller datasheet) and field devices to choose the right transformer rating for our DDC panel.

Next things are to write a program for our controllers to accomplish the above sequence,

First, we need to change English words into the flowchart then we can change it later on the different programming language that required for BMS vendors either ladder logic or functional block or plain English and etc.

Whatever it is any BMS program functionality that will not go beyond the basic digital logic gates.

Flowchart for AHU Control sequence of operation

GUIDE TO BUILDING AUTOMATION

GUIDE TO BUILDING AUTOMATION

Building automation is monitoring and controlling a building’s systems including: mechanical, security, fire safety, lighting, heating, ventilation, and air conditioning.

Such systems can

• ·         keep building climates within a specified range,
• ·         light rooms according to an occupancy schedule,
• ·         monitor performance and device failures in all systems, and
• ·         alarm facility managers in the event of a malfunction.

Relative to a non-controlled building, a building with a BAS has lower energy and maintenance costs.

There are many components to a building automation system that require a little explaining to understand, and the benefits of installing such a system may not be immediately clear until you understand the mechanisms driving these systems.

That’s why we created this ultimate guide to understanding building automation systems. It’s designed to be an easy read-through, but feel free to use the links below to go directly to a topic that is relevant to your own research.

WHAT IS BUILDING AUTOMATION?

Building automation most broadly refers to creating centralized, networked systems of hardware and software monitors and controls a building’s facility systems (electricity, lighting, plumbing, HVAC, water supply, etc.)

When facilities are monitored and controlled in a seamless fashion, this creates a much more reliable working environment for the building’s tenants. Furthermore, the efficiency introduced through automation allows the building’s facility management team to adopt more sustainable practices and reduce energy costs.

These are the four core functions of a building automation system:

·         To control the building environment

·         To operate systems according to occupancy and energy demand

·         To monitor and correct system performance

·         To alert or sound alarms when needed

At optimal performance levels, an automated building is greener and more user-friendly than a non-controlled building.

A Building Automation System may be denoted as:
An automated system where building services, such as utilities, communicate with each other to exchange digital, analogue or other forms of information, potentially to a central control point.

What Is Meant By ‘Controlled?

A key component in a building automation system is called a controller, which is a small, specialized computer. We will explore exactly how these work in a later section. For now, it’s important to understand the applications of these controllers.

Controllers regulate the performance of various facilities within the building. Traditionally, this includes the following:

·         Mechanical systems

·         Electrical systems

·         Plumbing systems

·         Heating, ventilation and air-conditioning systems

·         Lighting systems

·         Security Systems

·         Surveillance Systems

A more robust building automation system can even control security systems, the fire alarm system and the building’s elevators.

To understand the importance of control, it helps to imagine a much older system, such as an old heating system. Take wood-burning stoves, for example. Anyone heating their buildings through pure woodfire had no way to precisely regulate the temperature, or even the smoke output. Furthermore, fueling that fire was a manual effort.

Fast-forward 150 years: Heating systems can be regulated with intelligent controllers that can set the temperature of a specific room to a precise degree. And it can be set to automatically cool down overnight, when no one is in the building.

The technology that exists today allows buildings to essentially learn from itself. A modern building automation system will monitor the various facilities it controls to understand how to optimize for maximum efficiency. It’s no longer a matter of heating a room to a specific temperature; systems today can learn who enters what rooms at what times so that buildings can adjust to the needs of the tenants, and then conserve energy when none is needed.

There is a growing overlap between the idea of controlling a building and learning from all the data the system collects. That’s why automated buildings are called “smart buildings” or “intelligent buildings.” And they’re getting smarter all the time.

THE EVOLUTION OF SMART BUILDINGS

Kevin Callahan, writing for Automation.com, points to the creation of the incubator thermostat — to keep chicken eggs warm and allow them to hatch — as the origin of smart buildings.

Like most technologies, building automation has advanced just within our lifetimes at a rate that would have baffled facility managers and engineers in, say, the 1950s. Back then, automated buildings relied on pneumatic controls in which compressed air was the medium of exchange for the monitors and controllers in the system.

By the 1980s, microprocessors had become small enough and sufficiently inexpensive that they could be implemented in building automation systems. Moving from compressed air to analog controls to digital controls was nothing short of a revolution. A decade later, open protocols were introduced that allowed the controlled facilities to actually communicate with one another. By the turn of the millennium, wireless technology allowed components to communicate without cable attachments.

An Intelligent Building system may be denoted as:

An automated system where building services and corporate processes, communicate with each other to exchange digital, analogue or other forms of information, to a central control point to manage the environment.

Terms to Understand

At first, the terms building automation professionals use look like a big game of alphabet soup. There are acronyms everywhere. Let’s clarify this now: 

Building Management System (BMS) and Building Control System (BCS) — These are more general terms for systems that control a building’s facilities, although they are not necessarily automation systems.

Building Automation System (BAS) — A BAS is a subset of the management and control systems above and can be a part of the larger BMS or BCS. That said, building management and building automation have so thoroughly overlapped in recent years that it’s understandable people would use those terms interchangeably.

Energy Management System (EMS) and Energy Management Control System (EMCS)— These are systems that specifically deal with energy consumption, metering, etc. There is enough overlap between what a BAS does and what an EMS does that we can consider these synonymous.

Direct Digital Control (DDC) — This is the innovation that was brought about by small, affordable microprocessors in the ‘80s. DDC is the method by which the components of a digital system communicate.

Application Programming Interface (API) — This is a term common in computer programing. It describes the code that defines how two or more pieces of software communicate with one another.

What makes the terminology particularly complicated is that the technology evolves so quickly that it’s hard to know at what point a new term needs to be applied. Then, you also have professionals in different countries using different terms but still having to communicate with one another. Just be prepared for the terminology to be in a state of flux.

HOW DO BUILDING AUTOMATION SYSTEMS WORK?

Basic BAS have five essential components:

Input devices / Sensors — Devices that measure values such as CO2 output, temperature, humidity, daylight or even room occupancy.

Controllers — These are the brains of the systems. Controllers take data from the collectors and decide how the system will respond.

Output devices — These carry out the commands from the controller. Example devices are relays and actuators.

Communications protocols — Think of these as the language spoken among the components of the BAS. A popular example of a communications protocol is BACnet.

Dashboard or user interface — These are the screens or interfaces humans use to interact with the BAS. The dashboard is where building data are reported.

What a BAS Can Do

·         It can set up the lighting and HVAC systems to operate on a schedule that makes those systems both more intelligent and more efficient.

·         It can get the various components and facilities within a building to coordinate and work together toward greater overall efficiency.

·         It can optimize the flow of incoming outside air to regulate freshness, temperature and comfort inside the building.

·         It can tell you when an HVAC unit is running in both heating and cooling helping to reduce utility costs.

·         It can know when an emergency such as a fire breaks out and turn off any facilities that could endanger building occupants.

·         It can detect a problem with one of the building’s facilities — such as, for example, an elevator getting stuck with people inside — and send an instant message or an email to the building’s facility manager to alert him/her of the problem.

·         It can identify who and when someone is entering and leaving a building

·         It can turn a camera on a begin recording when activity takes place – and send an alert and direct camera feed to the security team and facility manager.

·         Are there other functions that address clear pain points for building owners / facility managers?

The Role of Controllers

Controllers are the brains of the BAS, so they require a little more exploration. As mentioned above, the advent of direct digital control modules opened up a whole universe of possibilities for automating buildings.

A digital controller can receive input data, apply logic (an algorithm, just as Google does with search data) to that information, then send out a command based on what information was processed. This is best illustrated through the basic three-part DDC loop:

1.   Let’s say a sensor detects an increase in temperature in a company’s board room when the room is known to be unoccupied.

2.   The controller will apply logic according to what it knows: That no one is expected in that room, thus there is no demand for additional heat, thus there is no need for that room to warm up. (Note: The algorithm with which a controller processes information is actually far more complex than depicted in this example.) It then sends a command to the heating system to reduce output.

3.   The actual heating unit for the boardroom in question receives that command and dials back its heat output. All of this appears to happen almost instantaneously.

WHY ARE BUILDING AUTOMATION SYSTEMS USEFUL?

 The benefits of building automation are manifold, but the real reasons facility managers adopt building automation systems break down into three broad categories:

·         They save building owners money

·         They allow building occupants to feel more comfortable and be more productive

·         They reduce a building’s environmental impact

Saving Money

The place where a BAS can save a building owner a significant amount of money is in utility bills. A more energy-efficient building simply costs less to run.

An automated building can, for example, learn and begin to predict building and room occupancy, as demonstrated earlier with the heated board room example. If a building can know when the demand for lighting or HVAC facilities will wax and wane, then it can dial back output when demand is lower. Estimated energy savings from simply monitoring occupancy range from 10-30%, which can add up to thousands of dollars saved on utilities each month.

Furthermore, a building can also sync up with the outdoor environment for maximum efficiency. This is most useful during the spring and summer, when there is more daylight (and thus less demand for interior lighting) and when it is warmer outside, allowing the building to leverage natural air circulation for comfort.

Data collection and reporting also makes facility management more cost efficient. In the event of a failure somewhere within the system, this will get reported right on the BAS dashboard, meaning a facility professional doesn’t have to spend time looking for and trying to diagnose the problem.

Finally, optimizing the operations of different building facilities extends the lives of the actual equipment, meaning reduced replacement and maintenance costs.

Typically, facility managers find that the money a BAS saves them will over time offset the installation and implementation of the system itself.

Comfort and Productivity

Smarter control over the building’s internal environment will keep occupants happier, thereby reducing complaints and time spent resolving those complaints. Furthermore, studies have shown that improved ventilation and air quality have a direct impact on a business’s bottom line: Employees take fewer sick days, and greater comfort allows employees to focus on their work, allowing them to increase their individual productivity.

Environmentally Friendly

The key to an automated building’s reduced environmental impact is its energy efficiency. By reducing energy consumption, a BAS can reduce the output of greenhouse gases and improve the building’s indoor air quality, the latter of which ties back into bottom-line concerns about occupant productivity.

Furthermore, an automated building can monitor and thus control waste in facilities such as the plumbing and wastewater systems. By reducing waste through efficiencies, a BAS can leave an even smaller environmental footprint. In addition, a regulatory government agency could collect the BAS’s data to actually validate a building’s energy consumption. This is key if the building’s owner is trying to achieve LEED or some other type of certification.

The fact that everything is integrated into one control system, instead of three separate systems, is a real positive – Arindam Bhadra, Technical Head, SSA Integrate.

Sources

·         http://xinca.com/elements-intelligent-buildings-2734.html

·         http://en.wikipedia.org/wiki/Building_automation

·         https://members.questline.com/presentations/20140403ConsumersEnergyBuildingAutomationSystems.pdf

·         http://highperformancehvac.com/building-automation-systems-hvac-control/

·         http://www.automation.com/portals/industries/building-automation/the-evolution-of-building-automation-systems-bas

·         http://highperformancehvac.com/ddc-systems-direct-digital-controls/

·         http://www.automatedbuildings.com/news/apr14/articles/skyfoundry/140312090000skyfoundry.html

·         http://automatedbuildings.com/news/apr12/articles/8760inc/1203240751018760inc.html

·         http://www.mepc-mn.org/Understanding%20Your%20Utility%20Bill/Benefits%20of%20Building%20Automation%20Systems%20with%20EMS%20Logo.pdf

·         http://www.buildingautomationsystem.org/Benefits-Of-Building-Automation-Systems.html

·         http://www.kmccontrols.com/docs/Building_Sustainability.pdf