Improvement of Building Management System to Save Energy

Improvement of Building Management System to Save Energy

1. Introduction of BMS

Building Management System (BMS) is to control and monitor building services systems in an efficient way by centralizing the control of individual systems ( 1.1). The systems include HVAC, Fire Services Lift, Escalator, Lighting, Electrical Distribution, Steam & Hot Water, and Plumbing & Drainage.

The main function of BMS is centralized control & monitoring and fault management. So it has another name call Central Control and Monitoring System (CCMS). The other functions are enhance interface & connectivity between systems, service response to customer, operator control of systems and graphical display to make the control of system more users friendly. Improve energy efficiency and operational efficiency. Allow capacity for future upgrades & expansions and automation. And related system Building Automation System (BAS) will be use on BMS.

2. Basic BMS Design

3-Levels BMS Architecture ( 2.1):

l Management Level – User can configure and monitor plant performance. Anticipate future trends, improve efficiency, and analyze management report.

l Automation / Controller Level – The location with greatest technical control requirement, and differentiate one from others. Controllers automatically perform their tasks from I/P and to O/P. Controllers can communicate with each other (Peer-to-Peer). Event based operation. The devices can function at the highest efficiency and no repetitive information is transmitted. Controllers only react with the Management Level when plant goes out of limits, and adjustments are made through a user interface.

l Field / Floor Level – Information is gathered through sensors and other intelligent devices. The information will be sent back to the controllers.

Third party equipment is integrated into the Automation and Field levels with control at the Management level.

Centralized Architecture:

Centrally controlled system ( 2.5) – A control system in which transmission is to a central computer and the reliance of all controls on a central computer.

Distributed Architecture:

Distributed control ( 2.6) – A control system in which control computations and intelligence are made at different locations and the result coordinated.

System Architecture:

The constraints of BMS are network expansion, the limited variety of topologies and transmission media. The solutions are mixing of communication media (twisted pair, power line, radio, infra-red, fibre optics, coaxial). Complete implementation of OSI model. Using free topology, user-friendly software and development cost.

System Topology

Topology affects system redundancy, communication protocol and system response time. The common system topologies such as: Bus, Star, Tree, Ring and Mesh.

Bus Topology ( 2.7) – All devices are connected to a central cable, call the bus or backbone. The advantage is much less cabling requirements. The brands using include Ethernet, Profitbus, ControlNet, LonWorks.

Star Topology ( 2.8) – All devices are conned to a central hub. Star networks are relatively easy to install and manage, but bottlenecks can occur because all data must pass through the hub. Cable fault affects one device only. But communication hub fault affects all devices. The brands using include Ethernet, Profitbus, ControlNet, LonWorks.

Tree Topology ( 2.9) – The topology combines characteristics of linear bus and star topologies. It consists of groups of star-configured workstations connected to a linear bus backbone cable. Tree topologies allow for the expansion of an existing network, and enable schools to configure a network to meet their needs. Device at the highest point in the hierarchy controls the network. The brands using include Ethernet, Profitbus, ControlNet, LonWorks.

Ring Topology ( 2.10) – All devices are connected to one another in the shape of a closed loop, so that each device is connected directly to two other devices, one on either side of it. Same as bus network with both edges connect. The brands using include Token Ring, FDDI, Profitbus.

Mesh Topology (Fig 2.11) – Network topology which combines more than one basic topology such as bus, ring, or star. Good for redundancy. It will use lots of cable to connect every device with every device.

Considerations in Topology Layout for automating building with vast amount of points require well-designed network segmentation, in order to achieve a good performance & infrastructure. Well designed structured network by using repeaters, bridges or even better using routers to improve network reliability and simplify network troubleshooting. Some reasons why segmenting a network is important: Isolation of individual network segments in order to limit the propagation of a single fault to one segment and prevent this single fault from spreading out over the entire network. Different nodes demand different communication media and different network speeds but they all need to communicate with each other, which requires and interconnection between the different networking media. Increase the number of possible nodes in a single network and increase the number of possible nodes in a single network. Keep local traffic within one segment in order to avoid network traffic overload conditions which will make service like HVAC, lighting … malfunction.

BMS Configurations

There are three types’ configurations using in BMS:

1. Conventional configuration – Server workstations daisy chained with DDCs (usually using RS-485). Typical RS-485 Controller Level network ( 2.14) relatively low bandwidth (around 9600 bps). The limited nodes around 100, and the distance is lower than 1200m. Only for data transmission.

Controller Level Network

2. Ethernet-Based configuration – Use Ethernet as transmission media. Servers, Workstations and DDCs on the same Ethernet platform. Typical Ethernet-Based Network ( 2.15) with high bandwidth (typical 1Gbps backbone). Use IP Technology means open platform for various applications. Virtually no distance limitation. Always use for data, voice & video systems.

Ethernet-Based Network

3. Hybrid configuration ( 2.16) – Non-hierarchy architecture with combination of different independent networks and interfaces. Various network topologies.

Hybrid Configuration

Networking – Protocol

Protocol ( 2.17) is a set of rules, which allows computer/controllers/devices to communicate from one to another. Proprietary Protocols developed by systems or computer manufacture to communicate to their OWN hardware and software over a recommended network. Open Protocols opening up protocols means disclosing procedures, structures, and codes and allowing other system developers to write interfaces and share data on their network. Acceptance of an open protocol depends on its quality, features, and services provided.

2.17 Protocol

The OSI Seven Layer Model ( 2.18)

Each layer has a defined set of functions. The model provides a useful common reference to communicate protocol. Most communication protocols including those used in our field today use either all or some of the seven layers of the OSI model.

1. Network-capable Applications produce DATA.

2. Each protocol layer adds a header to the data it receives from the layer above it. This is called encapsulation. Encapsulated data is transmitted in Protocol Data Units (PDUs). There are Presentation PDU’s, Session PDU’s, Transport PDU’s etc.

3. PDU’s are passed down through the stack of layers (called the stack for short) until they can be transmitted over the Physical layer.

4. Any layer on one machine speaks the same language as the same layer on any other machine, and therefore can communicate via the Physical layer.

5. Data passed upwards is unencapsulated before being passed farther up.

6. All information is passed down through all layers until it reaches the Physical layer.

7. The Physical layer chops up the PDU’s and transmits the PDU’s over the wire. The Physical layer provides the real physical connectivity between machines over which all communication occurs.

2.18 OSI Seven Layer Model

The Physical layer provides for physical connectivity between networked devices. Transmission and receipt of data from the physical medium is managed at this layer. The Physical layer receives data from the Data Link Layer, and transmits it to the wire. The Physical layer controls frequency, amplitude, phase and modulation of the signal used for transmitting data, and performs demodulation and decoding upon receipt. Note that for two devices to communicate, they must be connected to the same type of physical medium (wiring). Ether to Ether, FDDI to FDDI etc. Two end stations using different protocols can only communicate through a multi-protocol bridge or a router. The physical layer is responsible for two jobs:

1. Communication with the Data link layer.

2. Transmission and receipt of data.

The Datalink Layer is the second layer of the OSI model. The datalink layer performs various functions depending upon the hardware protocol used, but has four primary functions:

1. COMMUNICATION with the Network layer above.

2. SEGMENTATION of upper layer datagrams (also called packets) into frames in sizes that can be handled by the communications hardware.

3. BIT ORDERING. Organizing the pattern of data bits before transmission (packet formatting)

4. COMMUNICATION with the Physical layer below.

This layer provides reliable transit of data across a physical link. The datalink layer is concerned with physical addressing, network topology, physical link management, error notification, ordered delivery of frames, and flow control.

Network Layer establishes and terminates connections between the originator and recipient of information over the network. Assign unique addresses to each node on the network. The addresses identify the beginning and end of the data transmission packets. Outbound data is passed down from the Transport layer, is encapsulated in the Network layer’s protocol and then sent to the Datalink layer for segmentation and transmission. Inbound data is de-fragmented in the correct order, the IP headers are removed and then the assembled datagram is passed to the Transport layer. The Network layer is concerned with the following primary functions:

1. Communication with the Transport layer above.

2. Management of connectivity and routing between hosts or networks.

3. Communication with the Datalink layer below.

Transport Layer maintain reliability on the network and enhances data integrity by delivering error-free data in the proper sequence. It may use a variety of techniques such as a Cyclic Redundancy Check, windowing and acknowledgements. If data is lost or damaged it is the Transport layer’s responsibility to recover from that error. Functions:

1. Communicate with the Session layer above.

2. Detect errors and lost data, retransmit data, reassemble datagrams into datastreams

3. Communicate with the Network layer below.

The session layer tracks connections, also called ‘sessions’. For example: keep track of multiple file downloads requested by a particular FTP application, or multiple telnet connections from a single terminal client, or web page retrievals from a Web server. In the World of TCP/IP this is handled by application software addressing a connection to a remote machine and using a different local port number for each connection. The session performs the following functions:

1. Communication with the Presentation layer above.

2. Organize and manage one or more connections per application, between hosts.

3. Communication with the Transport layer below.

The Presentation layer handles the conversion of data formats so that machines can ‘present’

data created on other systems. For example: handle the conversion of data in JPG/JPEG format to Sun Raster format so that a Sun machine can display a JPG/JPEG image. The Presentation layer performs the following functions:

1. Communication with the Application layer above.

2. Translation of standard data formats to formats understood by the local machine.

3. Communication with the Session layer below.

The application layer is the application in use by the user. For example: a web browser, an FTP, IRC, Telnet client other TCP/IP based application like the network version of Doom, Quake, or Unreal. The Application layer provides the user interface, and is responsible for displaying data and images to the user in a recognizable format. The application layers job is to organize and display data in a human compatible format, and to interface with the Presentation layer.


Intended Market

Controlled by

Developed by



ASHARE Committee

ASHARE Committee


Utilities Power Generation

DNP3 Users Group


EIB – European Installation Bus





Residential, Buildings






Modicon (Schneider)

OPC – OLE for Process Control


OPC Foundation

Microsoft and other companies






Industrial, Buildings

EN50170, DIN19245

ABB, Siemens, Honeywell


Industrial, Buildings

ISO 11898/11519





Allen Bradley

Message Frame Format

Fig 2.19 Message Frame Format

Master-Slave Protocol (2.20) – The control station is called “master device”. Only master device can control the communication. It may transmit messages without a remote request. No slave device can communicate directly with another slave device.

2.20 Master-Slave Protocol

Peer-to-Peer Protocol (2.21) – All workstations are loaded with the same peer-to-peer network operating system. Each workstation configured as service requester (client), service provide (server), or even BOTH.

2.21 Peer-to-Peer Protocol

Client-Server Protocol (2.22) – Client workstation are loaded with specialized client software. Server computers are loaded with specialized server software designed to be compatible with client software.

2.22 Client-Server Protocol

The CSMA/CE Protocol is designed to provide fair access to the shared channel so that all stations get a chance to use the network. After every packet transmission all stations use the CSMA/CD protocol to determine which station gets to use the Ethernet channel next. CSMA/CD likes a dinner party in a dark room: Everyone around the table must listen for a period of quiet before speaking (Carrier Sense). Once a space occurs everyone has an equal chance to say something (Multiple Access). If two people start talking at the same instant they detect that fact, and quit speaking (Collision Detection). IEEE 802.3 standard covers CSMA/CD.

Switched Ethernet – nodes are connected to a switch using point-to-point connections, When a frame arrives at the switch, the control logic determines the transmit port. If the transmit port is busy, the received frame is stored in the queue which is a First-in First-out (FIFO) queue. The memory to store pending frames is obtained from a shared memory pool. In case the memory is full, the received frame is dropped.

Networking – Cables

Copper wire pairs are the most basic of the data media.

• Two wire untwisted pair

The insulated wire conductors run in parallel, often in a moulded, flat cable. Normally used over short distances or at low bit rates, due to problems with crosstalk and spurious noise pickup. Performance in multiple conductor cables is enhanced by dedicating every second cable as a ground (zero volt reference), and by the use of electrically

banetworkced signals.

1. A single wire is used for the signal transmission/reception

2. A common reference level/point is existed between the transmitter and receiver

3. It is the simplest connection technique but it is sensitive to noise, interference, loss, and signal reflection

4. It is suitable for short distance and low data rate application (Normally less than 200Kb-meter/s)

• Twisted Pair

The insulated conductors are twisted together, leading to better electrical performance and significantly higher bit rates than untwisted pairs. UTP is unshielded, like telephone cable, whilst STP is shielded and capable of higher bit rates. Systems using banetworkced signals obtain the highest bit rates.

1. Twisting or wrapping the two wires around each other reduces induction of outside interference

2. 1 to 5 twists per inch is quite typical • Cheap and moderate bit rate applications

3. For a few km distance the bit rate can be up to 10Mb/s, and 100Mb/s can be achievable for short distance applications like 100m

2.23 Two wire untwisted pair and Twisted Pair

Unshielded Twisted Pair (UTP):

•Composed of two of more pairs of wires twisted together

•Not shielded

•Signal protected by twisting of wires

•Impedance of 100W

•Recommended conductor size of 24 AWG

2.24 Unshielded Twisted Pair

Cat5e: 100MHz ANSI/TIA/EIA-568-B.1

Cat6: 250MHz

Cat7: 600MHz


•Susceptibility to damage

•Limited flexibility for MACs (move, add and change)

•Distance limit of 10m

•Avoid in high traffic areas, heavy furniture locations, cross undercarpet power on top at 90 degrees

2.25 Cat3, Cat5e and Cat6 Cable

Screened Twisted-Pair (ScTP):

•Characteristic impedance of 100 W

•Four pair 22-24 AWG solid conductors

•Mylar/aluminum sheath around all conductors

•Drain wire that must be grounded

2.26 Screened Twisted-Pair

Shielded Twisted Pair (STP):

•Composed of two pairs of wires

•Metal braid or sheathing that reduce electromagnetic interference (EMI)

•Must be grounded

•Characteristic impedance of 150 W

•Conductor size is 22 AWG

•Electrical performance is better than UTP (300MHz bandwidth)

•More expensive

•Harder to handle – thick and heavy

2.27 Shielded Twisted Pair

Coaxial Cable (Coax): Composed of insulated center conductor with braided shied. It provides high degree of protection against EMI.

•Because the electrical field associated with conduction is entirely carried inside the cable; problems with signal radiation are minimized very little energy escapes, even at high frequency.

•There is little noise pick up from external sources. Thus, higher bit rates can be used over longer distances than with twisted pairs

2.28 Coaxial Cable

Series 6 (Video):

•Characteristic impedance of 75 ohms

•Mylar/aluminum sheath over the dielectric

•Braided shield over the mylar

•18 AGW solid-center conductor

2.29 Series 6

Series 11U (Video):

•Characteristic impedance of 75ohms

•Mylar/aluminum sheath over the dielectric

•Braided shield over the mylar

•14 AWG solid-center conductor or 18 AWG stranded-center conductor

2.30 Series 11U

Series 8:

•50 ohms characteristic impedance

•Multiple mylar/aluminum sheath over the dielectric

•Multiple braided shield over the mylar

•11 AWG solid-center conductor

2.31 Series 8

Series 58 A/U:

•50 ohms characteristic impedance

•Mylar/aluminum sheath over the dielectric

•Braided shield over the mylar

•20 AWG solid-center conductor

2.32 Series 58 A/U

Fibre Optics: Higher bandwidth and much lower signal loss than copper conductors. It used in the backbone or in horizontal runs of huge control network.

•The data is carried as pulses of light from a laser or high-power LED.

•Optical fibre is non-electrical, hence is completely immune from electrical radiation and interference problems. It has the highest bit rate of all media.

•The fibre consists of an inner glass filament, contained inside a glass cladding of lower refractive index, with an outer protective coating. In a step index fibre, there is a sudden transition in refractive index. A graded index fibre has a gradual transition from high to low index, and much higher performance.

•Most common fibres are multimode, where the inner fibre is larger than the wavelength of the light signal, allowing multiple paths to exist, and some dispersion to limit the obtainable bit rate. In single mode fibres, the inner fibre is very thin, and extremely high bit rates (several Gbps) can be achieved over long distances.

2.33 Fibre Optics

Multimode Fibre: Composed of a 50 or 62.5 micron core and 125 micron cladding. It commonly used in horizontal and intrabuilding backbones. It has distance limitation of 2000m. Often uses a light-emitting diode (LED) light source.

•The center core is much larger and allows more light to enter the fiber

•Since there are many paths that a light ray may follow as it propagates down the fiber, large time dispersion may occur which results in short distance applications or bandwidth reduction

•Because of the large central core, it is easy to couple light into and out of the this type of fiber

•It is inexpensive and simple to manufacture

•Typical value: 62.5/125

Multi-Mode Graded Index

•It is characterized by a center core that has non-uniform refractive index

•The refractive index is maximum at the center and decreases gradually towards the outer edge

•The performance is a compromise between single-mode step index fiber and multi-mode step index fiber

2.34 Multi-Mode Fibre

Singlemode Fibre: It composed of a 6 or 9 micron core and 125 micron cladding (say8/125 or 9/125). It used for distances up to 3000m. It uses a laser light source.

•Small core diameter so that there is essentially only one path that light may Take care,as it propagates down the fiber

• There is minimum time dispersion because all rays propagating down the fiber with the same delay time and results in wider bandwidth (i.e. high bit rate)

• Because of the small central core, it is difficult to couple light into and out of the this type of fiber

• It is expensive and difficult to manufacture

• Typical value: 9/125

2.35 Singlemode Fibre


Also Called





4-wire phone station wire





Voice application

Flat Gray Modular

Flat Satin, tele. cable



RJ-11 / RJ-45

Short data cables






*5 categories

*Twist prevent interference

*Voice grade usually not for data





RJ-45 / IBM data connector

*Shielding reduces interference

*Complicate installation


Frozen yellow garden hose




Original Ethemet cabling


RG-58 Cheapenet




*Looks like cable TV

*Easier to work with than thick coax.





BNC or IBM data connector

Similar to RG-58, but not interchangeable

Fibre-optic cable

Fibre Glass

Several Gbps

Several km

SI / ST / SMA905 / SMA906

*Difficult to install

*High bandwidth

*Long distance

*Virtually error free

*High security

2.36 LAN Media Technology Analysis

Open System

The definition of open system is that system implements sufficient open standards for interfaces and services. It is supporting formats to enable properly engineered components to be utilized across a wide range of systems and to interoperate with other components. And that system in which products and services can be mixed and matched from set of suppliers; and supports free exchange of information/data between different systems without inserting gateways or proprietary tools. Some benefits from Interoperability:

•Devices can be shared among different subsystems.

•Reduce cost, shorten installation time, and reduce complexity as parts are being reduced.

•Devices in different subsystems can interact with each other; therefore, new breed of applications can be created easily.

•Owners can choose the best-of-breed products from different manufacture.

•Elimination of gateway dependency, especially during system upgrade.

•Allow move-add-change relatively easy, hence lower life-cycle costs.

The characteristics of open system are well defined, widely used, preferably nonproprietary interfaces/protocols; Use of standards which are developed/adopted by recognized standards bodies or the commercial market place; and definition of all aspects of system interfaces to facilitate new or additional systems capabilities for a wide range of applications.

The different between proprietary protocols and open protocols; For Proprietary protocols, most manufactures have their own proprietary protocols within their systems, so no communication between Systems unless a gateway is deployed. For open protocols, it allows systems of different manufacturers to communicate. Systems communicate with each other.

2.1 BMS – Open System – Modbus:

A high-level protocol for industrial networks developed in 1979 by Modicon (now Schneider Automation Inc.) for use with its PLCs. It is providing services at layer 7 of the OSI model. Modbus defines a request/response message structure for a client/server environment. It is the most commonly available means of connecting industrial electronic devices. Several common types of Modbus:

l Modbus RTU

n A compact, binary representation of the data.

l Modbus ASSII

n Human readable & more verbose.

l Modbus/TCP

n Very similar to Modbus RTU but is transmitted within TCP/IP data packets.

2.37 Modbus

2.2 BMS – Open System – ARCent:

Attached Resource Computer NETwork (ARCnet) was founded by the Data point Corporation in late 1970s. ARCnet was one of the topologies used early on networking and is rarely used as the topology of choice in current LAN environments. ARCnet, however, still is a solid, functional and cost effective means of networking. Each device on an ARCnet network is assigned a node number. This number must be unique on each network and in the range of 1 to 255. ARCnet manages network access with a token passing bus mechanism. The token (permission to speak on the network) is passed from the lowest number node to higher number nodes in ascending order. Lower numbered addresses get the token before the higher numbered addresses. Network traffic is made more efficient by assigning sequential numbers to nodes using the same order in which they are cabled. Choosing random numbers can create a situation in which a node numbered 23 can be a whole building away from the next number, 46, but in the same room as numbers 112 and 142. The token has to travel in a haphazard manner that is less effective than if you numbered the three workstations in the same office sequentially, 46, 47, and 48, and the workstation in the other building 112. With this configuration, the packet stays within the office before venturing on to other stations. A maximum time limit of 31 microseconds is allotted for an ARCnet signal. This is also called a time-out setting. Signals on an ARCnet can travel up to 20,000 feet during the 31-microsecond default time-out period. You can sometimes extend the range of an ARCnet by increasing the time out value. However, 20,000 feet is the distance at which ARCnet signals begin to seriously degrade. Extending the network beyond that distance can result in unreliable or failed communication. Therefore, the time-out parameter and cabling distance recommendations should be increased only with great caution.

An ARCnet network is used primarily with either coax or twisted pair cable. Most older ARCnet installations are coax and use RG-62 A/U type cable terminated with 93 Ohm terminators. Twisted pair (UTP) installations are newer and use stranded 24 or 26 gauge wire, or solid core 22, 24, or 26 gauge type cable terminated with 100-Ohm terminators. Many ARCnet networks use a mix of both coax and UTP cabling. UTP cable is simple to install and provides a reliable connection to the devices, whereas coax provides a means to span longer distances. Typical ARCnet installations are wired as a star. ARCnet can run off a linear bus topology using coax or twisted pair as long as the cards specifically support BUS. The most popular star-wired installations of ARCnet run off two types of hubs:

1. Passive hubs cannot amplify signals. Each hub has four connectors. Because of the characteristics of passive hubs, unused ports must be equipped with a terminator, a connector containing a resistor that matches the ARCnet cabling characteristics. A port on a passive hub can only connect to an active device (an active hub or an ARCnet device). Passive hubs can never be connected to passive hubs.

2. Active hubs have active electronics that amplify signals and split them to multiple ports. The number of ports on an active hub varies with the manufacturer, but eight is typical. A port on an active hub can be connected to a port on another active device (such as another active hub or an ARCnet device) or to a passive hub.

One of the greatest flexibilities of ARCnet is that you can integrate connections from active hubs to a linear bus connection as long as you terminate at the last connection point.

2.38 Standard ARCnet Connection

• In cabling ARCnet networks with coax cable, you must follow several rules:

1. Never connect a passive hub to another passive hub directly.

2. Passive hubs should never be used to connect two active hubs.

3. Passive hubs are only used to connect an active hub and a node.

4. Unused connectors on active hubs do not need to be terminated.

5. Unused connectors on passive hubs must be terminated using a 93 Ohm terminator.

• The Fig 2.39 shows an ARCnet configuration using active and passive hubs. Active hubs are required to extend the network for long distances and to configure networks that have more than four nodes. Passive hubs are used as an economical means of splitting a port on an active hub to support three devices.

2.39 ARCnet Network with Coax

2.40 ARCnet Cable Distance

The trouble shooting of ARCnet:

•Duplicate addresses: No more than one node can have a given node address on the same network. If two or more nodes share an address, one of the two workstations will either lose its network connection or will not be able to find a network.

•Missing terminators: Missing terminators may not present visible problems on a small network. Missing terminators cause data retransmits on smaller systems, eventually appearing as transmit time out errors or network errors.

•Using a terminator with an incorrect rating: Coax uses 93 Ohm; UTP must use 100 Ohm terminators. A terminator’s value in ohms depends on the impedance of the cable. The cable’s impedance and the terminator’s value should always match.

•Failed network interface

•Failed active hubs (or a port on that hub)

•Cable lengths that exceed specifications: Twisted pair, cabled in a bus rather than a star, cannot have more than ten devices per segment. This number varies with different manufacturers. ARCnet UTP installed in a bus configuration is generally used only in very small networks of six nodes or less. This configuration has the major drawback of halting the network if a single cable is disconnected. In an ARCnet bus configuration, the network must be brought down to make any changes or service to the ARCnet interface cards.

•Coax connector not built and/or crimped correctly: Twist-on connectors are responsible for more intermittent errors on a network than most other failures because of their design.

ARCnet use as an office automation has diminished; however, ARCnet continues to find success in the field level automation industry because its robustness, deterministic performance and long cable distances.

• ARCnet ANSI/ATA 878.1 standard was developed by the ARCnet Trade Association (ATA) and approved by the American National Standards Institute (ANSI) in 1992.

• ARCnet Standard:

1. ANSI/ATA 878.1 – This standard defines the frame format, medium access, services, active hub operation, and the physical layer functions and connectors for a token bus LAN operating at 2.5 Mbps.

2. ANSI/ATA 878.1-1999 – Broaden the 878.1 standard to include alternate physical layers such as fiber optics and EIA-485 communications as well as alternate data rates.

3. ATA 878.2 (Draft) – This standard defines the method and the frame formats by which a block of data can be transferred utilizing ARCNET independent of the number of octets in the block of data. The standard defines a protocol by which data can be fragmented into one or more ARCNET frames and re-assembled at the receiving station.

4. ATA 878.3 (Draft) – This protocol encapsulation standard defines a method to embed or encapsulate an existing protocol onto an ATA 878 (ARCNET) network. This standard allows devices using RS-232, RS-422/485 point to point standards to migrate upward to a high-speed network with multi-master capabilities.

• Over the years, ARCnet has developed a large customer base for smaller LAN real-time automation systems, including building automation and industrial controls systems. Its success can be attributed to its high speed deterministic nature and its high reliability.

• ARCnet is a data-link layer technology with no defined application layer (i.e., defines two lower layers of the OSI model: data link and physical layers)

• The token-passing MAC defines five transmission types:

1. Invitation to transmit (ITT): the token

2. Free buffer enquiry (FBE): a query from the transmitting node to destination node to check buffer availability

3. Data packet (PAC): the data transmitted between nodes (8 to 516 characters)

4. Positive acknowledgement (ACK): acknowledgement of recipient

5. Negative acknowledgement (NAK): of FBE and PAC from the destination node


• Basic Symbol Units are the elements used to construct basic frames and reconfiguration bursts:

1. <SD>Starting Delimiter (all ARCnet frames begin with this symbol unit)

1 1 1 1 1 1 (6 symbols)

2. <RSU>Reconfiguration Symbol Unit

1 1 1 1 1 1 1 1 0 (9 symbols)

3. <ISU>Information Symbol Unit (each information unit contains 8 bits of data and 3-bit preamble)

1 1 0 d0 d1 d2 d3 d4 d5 d6 d7 (11 symbols)

• The data in <ISU> can be:

1. <SOU>Start of Header 0x01 (used to identify a packet)

2. <ENQ>Enquiry 0x85 (used to identify a request for a free buffer)

3. <ACK>Acknowledgement 0x86 (used to identify acceptance)

4. <NAK>Negative Acknowledgement 0x15 (used to identify non-acceptance)

5. <EOT>End of Transmission 0x04 (used to identify a token pass to the logical neighbor)

6. <NID>Next Node Identification 0x01 to 0xff (used to identify the next node in the token loop)

7. <SID>Source Node Identification 0x01 to 0xff (used to identify the source node of a packet transmission)

8. <DID>Destination Node Identification 0x000 to 0xff (used to identify the destination node of a transmission request or a packet transmission)

9. <CP>Continuation Pointer 0x03 to 0xff (used to identify the length of packet.)

In short packet mode (0 to 252 bytes), the CP requires only one <ISU>.

In long packet mode (256 to 507 bytes), the CP requires two <ISU>.)

10. <SC>System Code 0x00 to 0xff (used to identify a high level protocol, the ATA has a list of SC assignments)

11. <…DATA…>Data (the user data) Packet with size of 253, 254 or 255 ISUs are called exception packets and must be padded with null data and sent as a long packet

12. <FCS>Frame Check Sequence 0x00 to 0xffff (cyclic redundancy check CRC-16)

• A token is passed in an orderly fashion among all the active nodes in the network

• For example:

1. A network consisting of four active nodes addressed 6, 109, 122 and 255, connected in a star topology as shown above

2. Once the network is configured, the token is passed from one node to the node with the next highest node address even though another node is physically closer

3. All nodes have a logical neighbor and will continue to pass the token to their neighbor in a logical ring fashion regardless of the physical topology of the network, e.g., 6 – 109 – 122 – 255 – 6 – …

• Directed Messages:

1. Source node, which has grabbed the token to talk, inquires if the destination node is in a position to accept a transmission by sending out a FBE.

2. The destination node responds by returning an ACK meaning that a buffer is available or by returning a NAK meaning that no buffer is available.

3. Upon an ACK, the source node sends out a PAC with either 0 to 507 bytes of data

4. If the data was properly received by the destination node, the destination node sends another ACK. If the transmission was unsuccessful, the destination node does nothing, causing the source node to timeout. The source node will infer that transmission failed and will retry after it receives the token on the next token pass

5. The token is passed to the next node

• If the desired message exceeds 507 bytes, the message is sent as a series of packets – one packet every token pass. This is called a fragmented message. The packets are recombined at the destination node to form the entire message.

•ARCnet supports a broadcast message, which is an unacknowledged message to all nodes.

•Nodes that have been enabled to received broadcast messages will receive a message that specifies node 0 as the destination address.

•Node 0 does not exist on the network and is reserved for broadcast function

•No ACKs or NAKs are sent during a broadcast message making broadcast messaging fast

•ARCnet is able to reconfigure the network automatically if a node is either added to or deleted from the network. This reconfiguration process is automatic and quick without any software intervention.

•If a node joins the network, it does not automatically participate in the token-passing sequence. Once a node notices that it is never granted the token, it will jam the network with a reconfiguration burst that destroys the token-passing sequence. Once the token is lost, all nodes will cease transmitting and begin a timeout sequence based upon their own node address. The node with the highest address will timeout first and begin a token pass sequence to the node with the next highest address. If that node does not respond, it is assumed not to exist. The destination node address is incremented and the token resent. This process is repeated until a node responds. At that time, the token is released to the responding node and the address of the responding node is noted as the logical neighbor of the originating node. The process is repeated by all nodes until each node learns its logical neighbor. At that time the token passes from neighbor to neighbor without wasting time on absent addresses.

•RECON – Reconfiguration Burst <RSU><RSU>…<RSU> 765 RSUs

•If a node is unplugged from the network the reconfiguration sequence is slightly different. When a node releases the token to its logical neighbor, it continues to monitor network activity to ensure that the logical neighbor responded with either a token pass or a start of a transmission sequence. If no activity was sensed, the node that passed the token infers that its logical neighbor has left the network and immediately begins a search for a new logical neighbor by incrementing the node address of its logical neighbor and initiating a token pass. Network activity is again monitored and the incrementing process and resending of the token continues until a new logical neighbor is found. Once found, the network returns to the normal logical ring routine of passing tokens to logical neighbors.

2.3 BMS – Open System – EIB:

EIB concentrates on home and/or building automation and management.

Europe: European Installation Bus

Asia: Electrical Installation Bus

The protocol standards of EIB are ANSI/EIA 766 and ENV 13154-2.

• The EIB Device Network protocol defines:

1. Physical Layer

2. Data Link Layer

3. Network Layer

4. Transport Layer

5. Application Layer

• EIB goes on to specify (mandatory!) standard datapoint formats and their semantics in various applications.

The EIB Device Network Protocol supports the following media:

1. Twisted Pair (9600 bps)

• STP with 30Vdc

• Balanced, baseband, asynchronous (UART) transmission with even parity (range 1 km)

• Data packet size of 14 bytes (extension to 230 is currently under consideration)

• CSMA with bit-wise Collision Avoidance (dominant 0)

2. Powerline Carrier (1200 bps)

• Currently 230V 50Hz mains only

• Spread-spectrum FSK

• Maximum distance between 2 devices (without repeater): 600 m. (Communication is influenced by electromagnetic pollution conditions in the installation.)

3. Radio Frequency

• Under development

• In free field conditions, the transmission distance is about 300 m.

4. Infrared

• Under development

• No other information on this media.

The physical network topology of EIB.TP:

•The electrical segments can have an arbitrary topology (i.e. linear, star, tree, loop or combinations of them) consisting of individual wiring sections as long as the electrical requirements (resistive and capacitive length) are not exceeded.

•Terminating resistors are not required in EIB.

•Up to 64 bus devices may be connected to each lines, allowing a total of 64.000 components to be connected.

•The total cable length shall not exceed 1000 m per electrical segment. The maximum length allowed is 700 m between two devices and 350m between a power supply unit and a device. In certain cases the connection of more than 64 devices to the same line may be required. The system allows two segments to be connected via a bridge, mostly named “repeater”. The connection capacity of the line may thus be doubled. In principle, a line may include up to 4 electrical segments connected together via repeaters, thus taking the capacity of the line to 256 devices. However, more than one electrical segment shall only be used for extension of existing installation but not for a new (initial) installation. A maximum of 6 Line Controllers (i.e. Line Couplers, Backbone Couplers and Repeaters) are allowed in one transmission path. The logical segments themselves are connected together by line couplers (LC) via a single logical segment. A maximum of 16 logical segments is allowed. Up to 15 zones can be federated by using the Bus itself. This can be also achieved by higher level bus systems like ISDN or Profibus, requiring appropriated gateways.

•The first character of each frame is the control field.

•The control field contains the information about the layer-2 service, its class and a flag containing the information whether the LPDU is a repeated one.

•The control field indicates the type of the request frame, L_Data-, L_Poll_Data request frame or Acknowledgment frame. The two class-bits of the control field control the priority of the frame, if two devices start transmission simultaneously.

•Repeated format 1 frames have the repeat_flag set to zero, non-repeated ones have it set to one.

•The last character of a frame is the check byte which makes an odd parity over the set of corresponding bits belonging to the preceding bytes of the frame. This represents a logical NOT XOR function over the individual bits of the preceding bytes of the frame.

•EIB is a fully peer-to-peer network, which accommodates up to 65536 devices.

•The logical topology allows 256 devices on one line: 15 lines may be grouped together with a main line into an area

•An entire domain is formed by 15 areas together with a backbone line.

•On open media, nearby domains are logically separated with a 16-bit SystemID.

•Without the addresses reserved for couplers, (255 x 16) x 15 + 255 = 61’455 end devices may be joined by an EIB network.

•Installation restrictions may depend on implementation (medium, transceiver types, power supply capacity) and environmental (electromagnetic noise, …) factors. Installation and product guidelines should be taken into account. Couplers connect lines or segments, e.g. within the Twisted Pair (TP) medium, or different media; their functionality may be (some combination of) repeater, bridge, router, package filter (for traffic optimisation), firewall protection etc. EIB defines various standard coupler profiles.

• Physical Address

1. Each device, i.e. a router or an EIB end device shall have a unique physical address in an EIB network. The physical address is a two-octet value that consists of an 8-bit device number, a 4-bit line number and a 4-bit area number.

2. The device number shall be unique within a line. Routers shall always have the device number zero; i.e. EIB end devices may have the device numbers 1-255. See also paragraph 1.3.3 “Router, Sub-line, Main Line and Zone” for details.

3. The line number shall be unique within an area (0-15). The devices in the main line of an area shall always have the line number zero.

4. The area number shall be unique within an EIB network (0-15). The devices in the inner area shall always have the area number zero.

• Group Address

1. The group address is a two-octet value that doesn’t need to be unique. An EIB end device may have more than one group address.

2. Each EIB end device belongs to group zero, i.e. request frames with destination group address zero are broadcasts.

3. Functions of EIB Bus devices belonging to the same group, may be controlled by only one message sent by a “source” EIB Bus device.

• The source address field always contains the physical address. The physical address is only used as destination address for initialization, programming and diagnostic operations (connection oriented transmission).

Transport Layer Services – EIB layer-4 provides four different types of communication relationships:

•(T_Groupdata) A multicast communication relationship connects group-objects that belong to the same group. Group-objects may be distributed to a number of EIB end devices. Each EIB end device may be a transmitter. More than one group-object may exist in an EIB end device. The group-objects of an EIB end device may belong to the same or to different groups.

•(T_Broadcast) The broadcast communication relationship connects a single EIB end device with all communication partners. The single EIB end device is always a transmitter, the communication partners are always receiver.

•(T_Data_Unack) Every EIB end device has a one-to-one connection-less communication relationship with every other EIB end device. A one-to-one connection-less communication relationships shall not be used if the connection-oriented communication relationship is established to the same partner at the same time.

•(T_Connect, T_Data, T_Disconnect) An EIB end device only has a single one-to-one connection-oriented communication relationship.

The destination address (octets three and four) defines the EIB end device(s) that shall receive the frame. The destination address can be either a physical address (DAF=0) or a group address (DAF=1), depending on the destination address flag (DAF) of octet five.

The APDU corresponds to the TPDU, but reduced by the transport control field. The application control field is encoded and decoded by layer-7 and contains the layer-7 service codes. The application control field has a length of 4 or 10 bits, depending on the layer-7 service. The codes for the application control field are shown in 3/3/7-3. The complete PDU for each service primitive is shown in the description of every service. Not defined and not supported application layer services are ignored by the layer-7.

•4 bits in octet 5 indicate the length of data, the maximum length is 14

•Through the Network Protocol Control Information (NPCI), the Network Layer controls the hop count; for devices other than routers or bridges,

•Every message passing require acknowledgement from the receiving device(s)

Two vendor-independent EIB Tool Software (ETS) suites for Windows:

1. ETS End-User’s Edition: A project engineer or electrical contractor can import the Component Description into the ETS Project Edition. All device instances can be customized to the needs of the project and logically linked by assigning Group Addresses.

2. ETS Developer’s Edition (ETS+): With the ETS Developer’s Edition, the manufacturer encapsulates the remotely loadable applets in a series of abstract representations, which hide all implementation details. The resulting Component Description can be exported.

•1 bus line with up to 64 bus devices (max 1km)

•1 main line (function area) with up 16 bus line by line couplers

•1 area line (bus system) with up to 15 main lines by backbone couplers

•Total available bus devices in an EIB system is 11,520 – Automation Network specification realizes EIB on all media with a logical link layer according to ISO/IEC 802-2, including Ethernet and Arcnet. Not limited to highspeed backbones, also allows management or automation level devices to be directly connected. An enhanced specification catering for routing based on the Internet Protocol (IP) is being reviewed. In this way, allows transparent usage of existing LAN infrastructure, and is intrinsically Internet and Intranet enabled.

Advantages of EIB:

• For manufacturers and vendors:

1. EIB’s compact communication stack allows for small footprint implementations (< 5 kB); requirements are such, that the system may be realized easily on an 8-bit microprocessor.

2. Kick-start building blocks are available through standard EIB system implementations from major manufacturers.

3. Any product from any manufacturer can be imported as a template into the common ETS binding tool, without any need for PC software development by the product manufacturer.

4. An open software engineering Component Architecture for PC tools and implementations.

5. Tens of thousands of trained installation professionals.

• For installers and system integrators:

1. A synonym for unrivaled multi-vendor flexibility, guaranteed by certified EIB logo.

2. Neutral ETS tool platform for project design and commissioning.

3. Off-the-shelf training from dozens of training centers.

4. Wide spectrum of available products and solutions.

5. Robust installation technology.

• For owner, occupant and Facility Manager:

1. Minimal cost of ownership, as shown by 10 years of experience.

2. High electrical and functional safety of each individual device and of the system as a whole.

3. Long-term availability of extension and replacement technology and components.

• For all:

1. Standard Win32 API’s, including OPC server etc.

2. IP connectivity ensured through EIB ANubis.

The Limitations of EIB is 64 thousand devices with 32 thousand individually addressable, shared datapoints or subnetwork..

2.4 BMS – Open System – OPC:

OPC (OLE for Process Control) originally based on Microsoft’s OLE COM (Component Object Model) and DCOM (Distributed Component Object Model) technologies, the specification defined a standard set of objects, interfaces and methods for use in process control and manufacturing automation applications to facilitate interoperability.

OPC is a standard interface for factory automation application. It allows every system and communication drive program to connect and communication freely, therefore, OPC is a software interface definition.

OPC is not a new bus standard or a general communication protocol.

2.41 OPC Specification

2.4 BMS – Open System – LonWork:

LonWorks technology, brought on the market by the Echelon Corporation, is a complete platform for implementing control network systems, these networks consist of intelligent devices or nodes that interact with their environment, and communicate with one another over a variety of communications media using a common, message-based (information-based) control protocol, called LonTalk. LONs stand for local operating networks.

•The LonWorks protocol is also known as the LonTalk protocol and ANSI/EIA


•The LonTalk protocol is a layered, packet-based, peer-to-peer communications protocol

•It is designed for the specific requirements of control systems, rather than data processing systems

•The LonTalk tailors the protocol for control at each of the OSI seven layers to ensure a reliable and robust communications for control applications

•LONWORKS technology provides many different communications media options including 1.25 Mbps twisted pair, power line, fiber optic, coax, IR and RF transceivers. This media-independent feature provides the designer and end-user with a wide range of choices for communicating your data.

•The bit rate of a channel depends upon the properties of the medium and the transceiver design. In addition, the transceiver determines transmission distance, data throughput, node power consumption and node cost.

•For TP channels, 22- or 24- AWG cables should be used.

•For PL channel, the frequency range of transceivers is 100kHz to 450kHz.

•For RF channel, the currently approved transceiver is for a transmission speed of 4.883 kbps and frequency ranges conforming to the standard of region, e.g., ETS 300220 for European standard, MPT 1329 for UK standard, RCL 1993/1 for Australian standard, and FCC Part 90 for USA.

For data encoding methods, multiple data encoding methods are used in the LonTalk. Each encoding scheme is media dependent.

•Differential Manchester Coding used in direct mode:

•A transition at the beginning of every bit period provides a signal for synchronizing the receiver clock

•The presence of a second transition halfway between clock transitions indicates a zero data

•A “1” data is indicated by absence of a second transition in a bit period

•Non Return to Zero Coding (NRZ) used in special purpose mode:

•”1″ is high and “0” is low

• The LonWorks modified the CSMA protocol for multiple communication media, sustained performance during heavy loads, and support large networks

• If the devices wait for the same duration after backoff and before retry sending data, repeated collisions will result. Thus, randomizing the access delay reduces collisions

• LonWorks devices randomize over a minimum of 16 different levels of delay

• For example, 16 slots reduce the probability of two packets colliding to 1/16 = 0.0625

• A unique feature of the LonTalk protocol is that the number of available time slots is dynamically adjusted by every device, based on an estimate of expected network loading maintained by each device and hence number of randomization slots is increased as traffic increases (predicting the channel load)

• The number of randomizing slots = n * 16, where n = 1 to 63, the estimated channel backlog

• Each node that requires priority access is allocated a unique slot number on its Priority Channel

• Benefits

1. Linearly increasing response time, up to 99 % of the bandwidth

2. Supports open transmission media

3. Adding and removing of devices does not disturb data transmission

•Preamble is a sequence of “1” bits that allows the other nodes to synchronize their receiver clocks. The length of it must be long enough for synchronization. It is user-selectable, but at least six bits long.

•Byte sync is a single “0” bit that marks the end of preamble and indicates the beginning of a frame

•Followed by up to 256 bytes of L2 data (MSB first)

•Packet ends with Manchester code violation

•Delta backlog field in Layer 2 header updates offered traffic estimate on receiving nodes

•For example: For acknowledged message to a group of nodes, the expected traffic = 1 ACK from each receiver

•Packets can be addressed to a single device, to any group of devices, or to all devices.

•A LonTalk address is hierarchical structured as shown in the diagram above.

•Physical Address: Every LonWorks device includes a uniquie 48-bit identifier called the Neuron ID. The Neuron ID is typically assigned when a device is manufactured, and does not change during the lifetime of the device.

•Device Address: A LonWorks device is assigned a device address when it is installed into a particular network. Device addresses are used instead of physical addresses because they support more efficient routing of messages, and they simplify replacing failed devices. Device addresses consists of three components: a domain ID, subnet ID, and node ID. Devices must be in the same domain to exchange packets. The subnet ID identifies a collection of devices that are on a single channel, or a set of channels connected by repeaters. Subnet Ids are used to support efficient routing of packets in large networks. A node ID identifies an individual device within a subnet.

•Group Address: A group is a logical collection of devices within a domain. Groups are limited to 64 devices if acknowledged messaging is used; whereas any number of devices if unacknowledged messaging is used. A device is allowed to configure to be a member of up to 15 groups.

•Broadcast Address: It identifies all devices with a subnet, or all devices within a domain.

•An address is assigned to a node during installation process. It is said that the node is configured.

•The total address size is computed by adding the appropriate number of bytes indicated in the table above.

•Every LonTalk packet contains the address of transmitting device (the source address) and the address of receiving devices (destination address) that can either be a physical address, a device address, a group address, or a broadcast address.

•Devices respond only to those packets corresponding to their domain ID and their own physical address, which is usually known only to the corresponding network installation tools.

There are four different message services on LonWorks: Acknowledged, Repeated, Unacknowledged and Authenticated.

•Acknowledged Messaging: Acknowledgements are expected from each receiving device. If the sender do not receive acknowledgements, it times out and retries the transaction. The number of retries and timeout are both configurable.

•Repeated Messaging: A message is sent to a device or group devices multiple times. This messaging service does not incur the overhead and delay of waiting for acknowledgements. This is especially important when broadcasting information to a large group of devices.

•Unacknowledged Messaging: A message is sent once and no response is expected. This messaging service has the lowest overhead.

•Authenticated Service: Allows the receivers to determine if the sender is authorized to send that message. This messaging service prevents unauthorized access to devices and is implemented by distributing 48-bit keys to the devices at installation time.

A number of tradeoffs between efficiency, response time, security and reliability must be taken into account when using these message services.

• Authentication prevents unauthorized access to nodes and their applications, e.g., a junior technician cannot operate on a security device if he is not authorized.

• Sender and receiver possess the same 48-bit encryption key.

• Authentication is set by a network management command at installation time.

• Authentication process:

1. A receiver receives an authorized message

2. The receiver sends a random number to the sender and challenges the sender to provide authentication

3. The sender then uses the 48-bit encryption key, the data from the original packet and the 64-bit random number to perform a transformation on the challenge

4. The sender returns the result of transformation to the receiver

5. The receiver compares the response with its own transformation

6. If the transformation match, the receiver

The LonMark Interoperability Association was formed in 1994 by Echelon. Only LonWorks devices that have been certified by the LonMark Association – called LonMark devices can carry the LonMark logo.The availability of LonMark products provides end-users, system integrators and equipment specifiers the benefits of open interoperable multi-vendor systems:

1. Choice of vendors

2. Use of third party tools

3. Easy integration

4. Easy additions and changes

5. Reduced installation costs

Where once end-users were locked into lengthy and costly service and upgrade agreements from a single vendor, they can now implement control systems using LonMark devices from multiple vendors picking and choosing devices that best suit their needs knowing they can be easily integrated.

2.42 LonMark logo

• Functional profiles are implemented as LonMark objects on individual devices.

• LonMark objects are defined as a set of one or more input and/or output network variables, with semantic definitions relating the behavior of the object to the network variable values and to a set of configuration properties that specify configuration data for the object.

1. Standard Network Variable Types (SNVTs): ensure the data within the network variable interpreted in the same way (e.g., all temperature values must be transmitted over the network media in a common format)

2. Configuration Properties: provide standards for documentation and for the network message formats used to download the customization data to the device by network tools (e.g., hysteresis bands, default values, minimum and maximum limits, gain settings, and delay times). Other than Standard Configuration Property Types (SCPTs), manufacturers may also define their own User-defined Configuration Property Types (UCPTs)

• LonMark Functional profiles describe in detail the application layer interface including the network variables, configuration properties, and default and power-up behaviors required on LonMark devices for specific, commonly used control functions.

•The above example is the functional profile for a lamp actuator. The profile is used for devices that can control the illumination level of a lamp. Typical lamp actuators are dimmers, relays and controllable electronic ballasts.

• Network configuration includes the following steps:

1. Assigning domain ID and logical addresses to all devices and groups of devices.

2. Binding the network variables to create logical connections between devices.

3. Configuring the various LonWorks protocol parameters in each device for the desired features and performance, including channel bit rate, acknowledgement, authentication, and priority service.

• Network configuration may be quite complex, but the complexity is hidden by the network integration tools. LonMaker for windows offers a simple functional network design by simply dragging the devices’ application functional blocks onto a drawing and connecting inputs and outputs to determine how functional blocks communicate with each other.

• Network configuration can be either an ad hoc process or a pre-engineered process: in the former method, the devices are already connected to the network and powered-up, and the configuration data is downloaded over the network as it is defined. In the engineered method, the information is collected into a database by the network integration tool and is downloaded to the devices at installation time.

•LonWorks Network Services (LNS) is the NOS that provides a common, network-wide set of services supporting monitoring, supervisory control, installation, and configuration. In addition, it also provides programming extensions for easy use of network management and maintenance tools, data access services for HMI and SCADA applications as well as remote access via LonWorks or IP networks.

•With LNS, multiple system integrators, managers, and maintenance personnel can simultaneously access network and application management services and data from any number of client tools. It is because LNS uses a client/server architecture so that multiple applications can be active on a network at the same time.

•Using LNS, a manufacturer’s device plug-in software (implemented as an ActiveX automation server) runs without modification in any PC, and can be seamlessly integrated with the installation tools on the PC (i.e., the LonMaker)

•The LNS Servers are local to each subsystem and the LNS Servers are used to provide connectivity to both the LonWorks channels as wells as the IP channel. This approach does not provide a cost savings for small systems that require a local PC for supervisory control or a local HMI application since the PC and support both the local application as well as provide IP connectivity.

• An alternative implementation of LonWorks network as shown in the diagram above, in which, LonWorks to IP routers (i.e., i.Lon) are used to create IP channels.

• In addition to data server, the i.Lon is also a web server such that you can develop web pages stored in the i.Lon to serve the LonWorks network.

• There are three different ways to access the LonWorks network by i.Lon:

1. LNS

2. i.Lon Web Tag

3. xml

2.5 BMS – Open System – BACnet:

BACnet (Building Automation and Control Network) is a standardized data communication protocol which is used to connect all kinds of systems and infrastructure typically found in buildings, e.g. HVAC (Heating, Ventilation and Air Conditioning) control, access control systems, fire detection and alarm, vertical transport systems, elevator control, maintenance, waste management, lighting, etc. Developed by American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). A key design criterion was that the protocol had to be applicable to all building automation needs. To accomplish this, BACnet specifies most all of the most common functions: analog and binary input, output, and values; control loops; schedules, etc. that clearly applies to almost any kind of monitoring or control application.

The standards of BACnet are ANSI/ASHRAE 135, ISO 16484-5 and ENV 1805-1.

•The highest performance LAN option in terms of speed and data throughput is ISO 8802- 3, better known as “Ethernet”, which is very popular especially in the area of office networks. The second alternative is ARCNET (ATA/ANSI 878.1). In contrast to Ethernet, ARCNET uses a token-passing protocol to access the physical communication media and thus is deterministic, meaning that it is possible to place a bound on the maximum time that a device could have to wait before having a chance to transmit a message. This can be an important feature in real-time applications.

•The third networking possibility in BACnet, MS/TP (Master-Slave/Token-Passing), is not based on an existing standard (like Ethernet and ARCNET) but is a proprietary data link layer protocol which was designed from scratch. The MS/TP option was implemented to make it possible for manufacturers to build BACnet devices at lowest costs necessary for BACnet’s success in competing with proprietary LANs. By virtue of its simple interface and its communication rates MS/TP can be implemented on many standard microcontrollers without the added cost of dedicated communications ICs. BACnet MS/TP uses EIA-485 as a physical layer.

•The fourth option, LonTalk (ANSI/EIA 709), is the standardized language for the very popular building automation system LonWorks. BACnet only uses LonTalk as a data link layer protocol and does not make use of all the specific features defined in the LonTalk standard. LonTalk offers the greatest number of options in physical media including RF, infrared, twisted pair, coax and fibre-optic cables.

•The final data link and physical layer option in BACnet is the Point-To-Point (PTP) protocol. The PTP protocol accesses the communication medium through an EIA-232 full duplex interface. A typical application would be to connect to a modem for dial-up access to a remote building automation system.

•A single networking technology can be used in a system or multiple options can be combined to form a BACnet internetwork. In the latter case network segments using different LAN options are connected over router devices. It is frequently necessary to have multiple networks in a single installation. There may be too many devices to be connected to a single LAN, or the requirements of the installation might dictate the use of different types of LANs for different functions. In a typical scenario there is a number of controller devices based on MS/TP or LonTalk and a high-speed backbone based on Ethernet or ARCNET.

•The purpose of the BACnet network layer is to provide the means by which messages can be relayed from one BACnet network to another, regardless of the BACnet data link technology in use on that network.

•Some functions assigned to the network layer in the OSI model are not required in BACnet. One example is selecting a communications path between source and destination devices. BACnet imposes a requirement that, at most, one active path can exist between two devices.

•Another network layer function that BACnet does not support is message segmentation and reassembly. BACnet imposes a limitation on the length of the messages that pass through a router. The maximum length shall not exceed the capability of any data link technology encountered along the path from source to destination. Messages longer than this can still be conveyed, but they must be segmented and reassembled at the application layer. (Ethernet – 1497 bytes, ARCnet, MS/TP, PTP – 501 bytes, LonTalk – 228 bytes)

•Control byte indicates the presence or absence of other network layer information. If the destination for the message is a device on the same network, no additional network layer information is needed. If the destination is on a remote network, the client device must include the destination network number and MAC address of the destination device. The router on the local network will insert addressing information about the local network so that a response can be returned. Thus, a device does not need to know its own network number.

•DNET – destination network number

•DLEN – length of ultimate destination MAC layer address (a value of 0 indicates a broadcast on the destination network)

•DADR – ultimate destination MAC layer address

•S… – source …

Three dorms broadcast messages used by BACnet: Local, Remote and Global.

•A local broadcast makes use of the broadcast MAC address appropriate to the local network’s LAN technology, i.e., 0xFFFFFFFFFFFF for Ethernet, 0x00 for ARCnet, 0xFF for MS/TP, 0x00 in the DstSubnet field of Address Format 0 in LonTalk

•A remote broadcast is made on behalf of the source device on a specific distant network by a router directly connected to that network. In this case DNET shall specify the network number of the remote network and DLEN shall be set to zero

•A global broadcast, indicated by a DNET of 0xFFFF, is sent to all networks through all routers.

The key to understand the BACnet Application Layer are the model of the information contained in a building automation device and the group of functions or “services” used to exchange that information.

•The internal design and configuration of a BACnet device is proprietary in nature and different for each vendor.

•BACnet overcomes this obstacle by defining a collection of abstract data structures called “objects”, the properties of which represent the various aspects of the hardware, software, and operation of the device.

•BACnet objects provide a means of identifying and accessing information without requiring knowledge of the details of a device’s internal design.

•The communications software in the device can interpret requests for information about these abstract objects and translate those requests to obtain the information from the real data structures inside the device.

•These objects provide a “network visible” representation of the BACnet device.

•An object is simply a collection of information related to a particular function that can be uniquely identified and accessed over a network in a standardized way.

•All information in a BACnet system is represented by such data structures. The object concept allows us to talk about and organize information relating to physical inputs and outputs, as well as non-physical concepts like software, or calculations.

•Objects may represent single physical point, or logical groupings of points that perform a specific function. Objects meet the design requirement of providing each device with a common “network view,” i.e., all objects, regardless of the machine in which they reside, look alike!

•All BACnet objects provide a set of properties which are used to get information from the object, or give information and commands to an object. You can think of an object’s properties as a table with two columns. On the left is the name or identifier for the property, and on the right is the property’s value. Some properties are read only meaning that you can look at the property value, but not change it. Some properties can be changed (written).

•The slide above shows an example of a temperature sensor, which might be represented as a BACnet Analog Input object. The example shows a few of the properties which might be available with this object, although in practice there would be many more properties than those shown.

•The object has a name property (SPACE TEMP) and an object type (ANALOG INPUT). The Present_Value property tells us what the temperature sensor is reading at this moment (72.3 degrees). Other properties show us other information about the sensor object, such as whether it appears to be functioning normally, or High and Low Limits for alarming purposes

•Although there are thousands of potentially useful object types which might be found in building automation, BACnet defines 23 standard object types in some detail. A BACnet standard object is one whose behavior, in terms of which properties it provides and what they do, is defined in the BACnet standard.

•This set of standard objects represents much of the functionality found in typical building automation and controls systems today. BACnet devices are only required to implement the Device object. Other objects are included as appropriate to the device’s functions.

A “BACnet Device” is simply a collection of objects that represents the functions actually present in a given real device. While the slide above shows only one instance of each kind of object in the example device, a more typical BACnet device might have 16 BI and BO objects, 2 or 3 Schedule objects, and so on.

•The second part of the development challenge was to agree on what kinds of messages building automation and control devices might want to send to each other. Because BACnet is based on a “Client-Server” communication model, these messages are called “services” which are carried out by the server on behalf of the client.

•Here are the services related to accessing the properties of the objects previously described. Their names pretty much describe what the services do. The ReadProperty service, for example, is a message that contains the object and property identifiers that uniquely identify which object’s property is to be read and sent back. The message is always sent to a specific recipient and returns, hopefully, the requested property value in a standard form.

Beside using the LANs referred to previously, BACnet messages can travel over networks that use the Internet Protocol (IP) as their networking protocol. The major distinction between the two ways that BACnet can work over an IP internet can be summarized as follows: In IP message tunneling, the BACnet devices don’t know, or need to know, anything at all about IP. In BACnet/IP, each BACnet device is actually a full-fledged IP node, complete with its own IP address and IP protocol stack.

•In IP tunneling, Device A on Network 1 addresses a message to Device B on Network 2 using the BACnet network layer protocol. It sends the message to the Annex H router on its local network. (The router is called an “Annex H” router because Annex H is the place in the standard where this process is defined.) The Annex H router knows how to send IP messages over the Internet (or an “Intranet” based on IP) to its peer device on Network 2. It encapsulates the BACnet message (in a User Datagram Protocol frame) and sends it via IP to the Annex H router on Network 2. Note that both networks are connected via a standard IP router to the Internet at large.

•When the Annex H router on Network 2 receives the IP message from its peer, it removes the encapsulated BACnet message and sends it on to its final destination, Device B.

•The only downside to this is that each message shows up twice on each network – once as a pure BACnet message and once as an IP message.

•BACnet/IP is a different beast entirely. BACnet/IP devices view the IP internet as if it were a local area network. A device’s IP address (a 4-octet number like serves the same purpose as a device’s MAC or physical LAN address in other BACnet networks (and in the BACnet network layer protocol control information).

•The “BACnet Virtual Link Layer” or BVLL provides a set of messages that are used to deal, among other things, with specific idiosyncrasies of IP networks, such as the way broadcasts are handled. In addition, BVLL concept provides the following benefit:

•the BVLL control information can be easily extended to encompass virtually any kind of new network technology or other “microprotocol” that might come along. (A microprotocol is a set of rules that provide a “value-added” function like data encryption or data compression on packets that are otherwise ready for transport.) This means that with a minimum of fuss a specification could be developed to run BACnet directly over Asynchronous Transfer Mode (ATM) networks, Synchronous Optical Networks (SONET), Frame Relay networks, Integrated Services Digital Networks (ISDN), etc., and to provide for enhanced security and efficiency measures, all without touching BACnet’s existing application and network layer protocols.

•BACnet/IP devices don’t need Annex H routers and can talk with each other directly over the Internet. The only hitch is that IP routers don’t normally pass along “broadcast” messages, i.e., messages intended for all devices on a BACnet internetwork. Enter the “BACnet Broadcast Management Device” (BBMD).

•BBMDs act similarly to the Annex H routers previously described except that they only handle the forwarding of broadcasted IP messages. Since broadcasts are generally used very infrequently in BACnet, their propagation should not cause any problems.

•BACnet/IP also allows “foreign devices” to join the BACnet network from any subnet via SLIP or PPP, e.g., through an Internet Service Provider (ISP)

•By registering with a BBMD, the foreign workstation becomes a member of the BACnet/IP network and will receive forwarded broadcast messages from the BBMD when they are available and can request that messages be broadcast by the BBMD on its behalf. The foreign device can, of course, talk with any BACnet device directly without registration but will only receive broadcasts if the registration procedure is followed.

3. BMS – Compare with BACnet, LonMark & OPC:

The following table compare with BACnet, LonMark & OPC in different characteristics:





Data exchange between equipments




Monitor & operation value




Time control




Online group/ restructuring




Trend/ record




Unnecessary project items




Backup/ recovery




Remote management




Information technology compatibility

(network protocol, Gigabit Ethernet)




Network management




Lots of vendor selection




Implementation costs can be calculated from each point




The following table compare with BACnet, LonMark & OPC in different application, cost-effectiveness, standard protocol & interoperability:





Applicable to building automation & related applications

Industrial standard, commonly used for indoor heating and air-conditioning automation

Industrials standard for data exchange, a platform for integration with third-party system


Applicable to equipment with large data volume and review function

Applicable to field equipment with limited data volume & function

A platform for integration with third-party system, high engineering demand

Standard Protocol

All equipments are tested and certified by BACnet Testing Laboratory (BTL)

All equipments’ certification are self-declared by LonMark manufacturers

Object linking and degree of embedding (OLE)


Through testing to ensure standard mechanism, e.g. PICS, BIBBS and device profile

No definition for testing mechanism, limited interoperability

Depend on the implementation process

The result of compared with BACnet, LonMark & OPC. BACnet is better than others. The reason are because of user demand, no fixed architecture, object model is easily extended, do not depend on current technology, broad participation in its development, many vendors are committed to it and global interest. And the benefits of use BACnet are no charge for its use -anyone many develop implementations without cost. It maintained by an ASHRAE committee representing all sectors of industry. It designed specifically for building control. It can be implemented in devices of any size, readily enhanced and improved. And BACnet not tied to present technology. So BACnet succeed in Building Management System.

4. Energy Management

Energy Management is the major role of Building Management System – Building Automation System. Energy management system (EMS) optimizes the operations, conditioning processes, and indoor environmental parameters of building systems in order to maintain a satisfactory indoor environment at minimum energy use (mainly in HVAC and Lighting control).

EMS is special purpose computerized control system which can be programmed to operate in an energy efficient and effective manner.

i) Lighting equipment

ii) HVAC equipment – chillers, fans, boilers, pumps, dampers, valves and motors, etc.

iii) Vertical Transportation equipment – lifts, escalators)

Improve energy efficiency & reduce energy demand. Create environmental benefits.

i) reduce consumption of fuels and emissions from existing power plants and building boilers

ii) Improve IAQ (when more % of outside air is used)

4.1 EMS on HVAC:

4.1.1 Set-points:

Set- points saving by reappraise and / or relax set-points. Set-point for cooling can be increased relative to an increase external temperature. It cautions to match overall plant scheme in accordance to overall control strategy. Set-point regular review of set-points and modification is an essential part of the ongoing energy cycle. It graduals change over a period of time to ensure smooth transition. 5-30% saving is possible.

4.1.2 Time Schedule

Time schedule only run the plant when the space is occupied. It may needs multiple switching periods of occupancy on different days.

4.1.3 Calendar Schedules

Calendar schedules use different switching patterns on different calendar dates. It enables carried time scheduling to match varying working patterns. It is good for exhibition halls or meeting rooms. Save operator time as can be configured once. And holiday schedule enable further saving. (e.g. 8 public holiday, 5 working days/ week, equate to 3% energy saving).

4.1.4 Economizer

For cooling system that has a capacity of 7.5 tons or more. Basic principle is to compare the external and internal temperatures, i.e. based on how mild it is outside, and how high the internal temperature is the cooling plant will be switched on at the least possible time, and opposite for the optimum off function. Economizer has a properly of a building’s total energy consumption depending mostly on local climate and internal cooling loads. Today, It has a choice of algorithms such as linear relationship between rate of rise and internal temperature to enable a more accurate calculation of start and stop time. But malfunctioning economizers waste much more energy than were intended to save. If it breaks down when its damper is in a fairly wide-open position, peak loads shoot up as cooling or heating systems try to compensate for the excess air entering the building, resulting from cooling excessive outside air.

4.4 Economizer example

The components of an economizer: An economizer is simply a collection of dampers, sensors, actuators, and logic devices that together decide how much outside air to bring into a building.

4.1.5 Night Purge / Summer Pre-Cooling

Night purge / summer pre-cooling a cooling load at start of building occupancy is required. External air is cooler than the required occupancy temperature. This sequence enable central AHU plants to run in full fresh air mode for a period of time (30 minutes is typical). Reduce the initial load on the primary plant at occupancy start. Night purge / Summer pre-cooling have additional benefit of a fresh air feeling for staffs at occupancy.

4.1.6 Load cycling

Load cycling is switching off of electrical load for a period of time on a regular basis. Applied to background plant such as a fan or pump where the effect of it being turned off will not result in inconvenience. Should allow override in the event of exceeding pre-set such as high space temperature. The disadvantages that load cycling may cause an increase in electrical load during start up and decrease the overall life of the plant.

4.1.7 Maximum demand

Maximum demand applied to buildings where a limit is set for the maximum consumption allowed (normally over a half-hour period). It has a cost reduction measure by preventing this limit being exceeded. When exceeded, a higher tariff per KW/H applies. Cost reduction is typically 3-5%. Some electrical loads will be shed and reinstated.

4.2 EMS on Electrical:

4.2.1 Power Factor

Power factor (PF) is a major consideration in efficient building system operation.

Power factor = Real Power / VI = kWh/Sqrt(kWhA² + kVarhA²)

=VIP / Sqrt(VA²IPA²+VA²IrA²+VA²IhA²)

It is the measure of how effectively the equipment is converting electric current to useful power output. When the power factor is high, it can avoid power factor surcharges on the electricity bill. The power factor decrease with the installation of non-resistive loads, such as motors, transformers, lighting ballasts, VSD in HVAC, chiller pumps, lift. The benefits of maintaining a high power factor include released system capacity and improved voltage. It can be improved by proper selection, sizing and installation of capacitors if it is not due to harmonics.

A quick estimation of PF is shown in the fig 4.2.1 as below

4.2.1.Power factor – kVarh/kWh relationship

PF correction equipment is necessary to maintain the required voltage levels and system stability.

4.2.2 Lighting

The monitoring and control of area lighting can be summarized in the figure below:

4.2.Lighting Monitor & Control

1. Hardware interface: Network wiring, device address, poll priority, etc.

2. Relay I/O status: Indicate on/off status of light, as well as an alarm trigger.

3. Group mapping: A collection of output relays that are assigned through software for on/off.

4. COS reporting: Report the change of object attributes values back to the BAS.

5. Triggers: Change of attribute value can cause a control process to run.

6. Scheduling: Schedule for light on/off.

7. Overrides: Allows one to turn the outputs on or off regardless of schedules or other requests.

Energy concern accounts for 30-40% of the electrical operating costs in commercial buildings; yet, 70% of the time is unoccupied. During occupied period, lighting level is usually higher than needed. Lighting control programs can provide the flexibility of the occupant needs. Energy management strategies: interface the electrical panels with zones of lighting fixtures, or individual controls can be placed at the fixtures to control lighting conditions.

5. Conclusion

In conclusion, Building Management System (BMS) is computer software using in a building to control, monitor and manage all the system. The system includes HVAC, Fire Services Lift, Escalator, Lighting, Electrical Distribution, Steam & Hot Water, and Plumbing & Drainage. The monitoring facilities of a BMS to monitored and recorded the building status, environmental conditioning and energy consumption. Building operator can get all the data with full pictures how the system is operated. So the operator can often lead to identification of problems and improvement on the building operated. The result of data can be help to have a greater awareness on energy efficiency with the trend logging of energy performance. BMS can improve the overall management and performance of building facilities. The system can be set to operate different equipment automatically according to a pre-determined schedule. Now BMS can perform interactive calculations to determine the most efficient operating conditions to save energy. After use BMS can be cut down the electricity bill by about 10% to 20%. There should be noted that the energy saving of using BMS is affected by the condition of the building equipment, the existing O&M service levels, the skill and knowledge of the O&M team and the operating features of the premises.

There are several brands of BMS in the market. After compare with the different BMS, the result is that BACnet is better than others. The reason are because of user demand, no fixed architecture, object model is easily extended, do not depend on current technology, broad participation in its development, many vendors are committed to it and global interest. The key design issues for the building management system: Network span and number of controlled devices; Reliability of data exchange ; Transmission time; Mixing of communication media; Installation technology; Automation services to be integrate (Security, FS); Interface to other ELV and BMS systems; Node cost and installation cost; Wiring topology; Long-term cost saving; User-friendly operating software for value added services. It is suggested to take the above mentioned actions for improving the building management system, thus save more energy and money.


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Improvement of building management system to save energy. (2017, Jun 26). Retrieved September 19, 2021 , from

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