Building Management Systems Basics

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by
BAS Consultant & Engineer

2. Basic of Instrumentation
• Us our Body and its parts
• Our Body Reflexes

3. In BMS
INPUTS:- Sensors
Temperature (of room)
Humidity (of room)
Flow Rate (chilled Water)Flow Rate (chilled Water)
Pressure (of Fire Hydrant)
Level (of a Tank)
Run status (Pumps, Fans)

4. Temperature Sensors
– Sensing technologies
• Thermistor
– Accurate over limited
range
– Point type only
– Used for space
temperature
• Nickel Wire
– General purpose sensor
– Point or averaging type
– Used for space or duct
– Application Issues
• Mount inside thermal well for water
temperature
• Mount return air sensor away from
fresh air stream
• Mount space temperature sensor :
– At 1500 mm height
– On inside wall
– Away from direct sun or other
heat sources
• Ensure off-coil sensors are far
– Used for space or duct
• Platinum
– High accuracy / linearity
– Point type only
– Precision applications
• Ensure off-coil sensors are far
enough away from coil
• Outdoor air temperature sensors
require sunscreen
• Calibrate using precision resistor,
validate using digital thermometer
• Know mounting scope of
responsibility

5. Pressure Sensors
– Air Static Pressure
• Used to control VFD based on
VAV duct static
• Must be mounted in region of
laminar flow; five duct diameters
from restrictions
• Active sensor
– Water Static Pressure
• Used to monitor pressure at top of
sprinkler riser
• Commercial grade sensors can leak
– Water Differential Pressure
– Air Differential Pressure
• Used to calculate airflow from
velocity pressure
– PVELOCITY = PTOTAL - PSTATIC
– CFM = 4005 * AREA *
(PVELOCITY / K FACTOR)½
• Used in VAV boxes and air flow
monitoring stations
– Water Differential Pressure
• Used to control bypass valve or VFD
• When controlling bypass, best to
mount at last AHU
• Do not try to save costs by using
two static pressure sensors
• Calculation error of same magnitude
as signal may ocur.

6. Other Sensors
Waterflow
Mount in region of laminar
flow; five diameters from
restrictions
Many technologies:
Annubar
Paddlewheel
Carbon monoxide
Control car park ventilation fans
Carbon Dioxide
Used as indirect indicator of
indoor air quality
Paddlewheel
Electromagnetic
Turbine
Humidity
Used to measure the Relative
Humidity in air.
Some humidity sensors comes
with in built temperature
sensors also.
indoor air quality
Electrical Transducers
Current Transducers
Voltage Transducers
Lux Level Sensors
To measure the intensity of
light.

7. In BMS
OUTPUTS:- Control
Valves
VFD Speed Command
Air Dampers Actuators
ON-OFF Command (Fans,
Pumps, Boilers)

8. INPUTS & OUTPUTS
INPUTS e.g
Analouge (varying-reading)
AI
Temperature, Humidity, Water Flow , Air
Flow , Tank Level, Energy KW, Voltage,
Current, Pressure, pH, Conductivity
Digital (Binary-ON or OFF)
DI or BI
Status (on/off, airflow , run, open/close)
Alarm
TripTrip
OUTPUTS e.g
Analouge (varying-positioning)
AO
Fan Speed regulating (0 to 100%)
Chilled water valve control (0 to 100%)
Digital (Binary-ON or OFF)
DO or BO
Command (on/off, open/close)

9. I/O
Building management system relies on 4 types sensory information to make a control decision
Analog inputs : are used to read a variable measurement. Examples are temperature, humidity and
pressure sensor which could be thermistor, 4-20 mA, 0-10 volt or platinum resistance thermometer
(resistance temperature detector), or wireless sensors.
Digital input : indicates if a device is turned on or not. Some examples of a digital input would be , an airDigital input : indicates if a device is turned on or not. Some examples of a digital input would be , an air
flow switch, or a volt-free relay contact.
Analog output : controls the speed or position of a device, such as a variable frequency drive, a I-P
(current to pneumatics) transducer, or a valve or damper actuator. An example is a chilled water valve
opening up 25% to maintain a setpoint.
Digital outputs : are used to open and close relays and switches. An example would be to turn on the
parking lot lights when a photocell indicates it is dark outside.
A typical Mid Size Building may have 800 -2000 sensory points also known and I/O points.
A complex Building like an Airport may have more than 5000 points

10. DDC Controllers
Types of DDC controllers
Fixed function
Configurable
Text programmable
Graphic programmable
Point Definition
Ranging (linear, calculated,
Control Loops
Proportional plus integral control
commonly used
Other software routines used in
local control logic
Minimum, maximum, average,
calculator, etc.
Psychometric calculations
Timing (delays, pulses, etc.)Ranging (linear, calculated,
polynomial)
Filtering (smoothing and
debounce)
Interlocks
Timing (delays, pulses, etc.)
Boolean and comparator
operators
Time clock and backup schedules

11. DDC physical

12. Control System

13. Sl.
No
IO Description AI DI AO DO FIELD DEVICE
1 AHU On/Off 0 0 0 1 AHU panel to accept 2A NO contact
2 AHU Run Status 0 1 0 0 Differential Pressure Switch across blower
3 AHU Auto/Manual Status 0 1 0 0 Pot . free contact @ AHU Panel
4 AHU filter Status 0 1 0 0 Differential Pressure Switch across filter
5 Return air temperature 1 0 0 0 Duct type temperature sensor
6 2 Way chilled water modulating valve control 0 0 1 0 2 way Modulating Valve
7 Chilled water return header flow rate 1 0 0 0 Flow meter
TOTAL 2 3 1 1

14. Basics of HVAC
Pot with water
Evaporation through the pores of Mud Pot makes the water inside cool

15. Purpose of HVAC
The main purpose of HVAC is to provide
the people working inside the building with
“CONDITIONED AIR” so that they will
have a comfortable and safe workhave a comfortable and safe work
environment.

16. What is Conditioned Air?
Conditioned Air” means that the air is clean
and Odor-Free, and the temperature,
humidity and movement of air are within
certain comfort range.certain comfort range.
Comfort Zone: (ASHRAErecommendation)
– – Temp : 22.7oC to 26.1oC
– – Relative Humidity : 50%
– – Air Velocity : 30 feet per minute

17. What is AHU?
• AHU is Air Handling Unit
Contains:–Fan, Cooling coil , Air Filter

23. Inputs to the Controller:

24. Outputs from the Controller:

25. What is a Chiller
• A heat exchanger using air, refrigerant, water and evaporation to transfer
heat (BTUs) to produce air conditioning (measured in tons).
• A chiller is comprised of an evaporator, compressor, condenser and
expansion valve system.

26. Cycle

30. Chiller Plant

31. Chiller Plant with BMS sensor

32. Chiller Plant Operation

33. Control Logic

34. Building Management System-: Begin with the basics
BMS – Building Management system
Building Automation system
A Building Management System (BMS)
is a blend of hardware & software basedis a blend of hardware & software based
control system installed in buildings to
control and monitor the building’s
mechanical, electrical & other utility
equipment

35. Building Services
Services Equipments
Mechanical system HVAC , Plumbing , Fire Fighting, STP
Electrical System Electrical DB’s/Lighting control & monitoring,
Generator set, UPS
Utility Lifts, Fire Alarm System, Security System, Public
address system

36. What is a Building Automation System?
A BMS system collects the operating information required for intelligent building
management.
It analyses the operation of the building systems by viewing all important
temperatures, humidities and equipment status.
Further to collection of these data, the BMS presents these data on the screen with
full color
• Automates some control strategies such as turning equipment On/Off according
to a time schedule – ensures energy savings
• Allows an operator sitting at the BMS work station to view key information about
the building – improves building operationsthe building – improves building operations
• Allows an operator sitting at the BMS work station to control some of the
equipment in the building – improves building operations allowing remote control
/ over-ride where necessary
• Maintains an audit trail of what happened and when it happened – improves
building management by means reporting and traceability
• Maintains historical data for selected information (like temperature, humidity
..etc) – improves building management by means reporting and traceability
• Alerts the operator at the BMS work station when readings fall outside of normal
range (i.e. breaker trips, temperature too warm, etc.) – improves building
management by having a faster reaction time to problems
• By doing the above and more a BMS system saves manpower, ensures productive
occupants (especially in an office environment), prolongs equipment life, and the
most important of all saves energy. diagrams (graphics) for the ease of
understanding.

37. BMS Protocols
BMS system manufacturer divided predominantly into two different
protocols, mentioned below-
• BACnet - A Data Communication Protocol for Building Automation and
Control Networks developed by ASHRAE. It gives freedom to client to
connect all BACnet compliant devices and ease in commissioning &
configuring.configuring.
• Lonworks -Lon Works is actually a family of products originally developed
by the Echelon Corporation. At the core of this technology is a proprietary
communications protocol called Lon Talk. Here one needs to buy license for
each individual controllers & devices. Commissioning requires software key
(dongle) all the time for commissioning & configuration.
• Modbus is developed by Modicon in 1979. It is used to establish master-
slave/client-server communication between intelligent devices. It is a de
facto standard, truly open and the most widely used network protocol in the
industrial environment and devices.

38. BMS System Architecture –
• IP- 1 Tier
Where all controllers are connected
to HMI on LAN.

39. RS 485 – 2Tier
Level1-: where all controllers are connected
to each other in daisy chain fashion & then
after they connect to router or gateway.
Level2-: When router or gateway is connected
to any HMI for monitoring & controlling.to any HMI for monitoring & controlling.

40. Building Automation System Software
Alarms
User Interface
and Password
Energy
Operations
Maintenance
Supervisory Controller (processing)
Operator Workstation (long term storage)
Operator Workstation
Where this feature resides
Control Logic
Demand Limiting
and Duty Cycling
Historical Data
Graphics
Scheduling
Supervisory Controller
DDC Controller
Supervisory Controller
Operator Workstation
Supervisory Controller
Supervisory Controller (processing)
Operator Workstation (long term storage)

41. BMS Typical BOQ-
It can be categorized in 3 broad categories-
1. BMS controllers, Softwares, POT(Portable Operator
Terminal),integration & PC.
2. Field Devices- It comprises different kind of sensors,
switches, actuators, Transmitters etcswitches, actuators, Transmitters etc
3. Cables & conduits

42. 1. BMS controllers, Software's, POT
(Portable Operator Terminal), for integration & PC.
• Controllers selection can be done based on the IO (Input Output) requirements directly
just to match AI(Analog Input), AO(Analog Output), DI(Digital Input), DO(Digital
Output) in the layman’s language.
• Integration to collect the data from different devices.

43. 2. Field Devices-
Comprises different kind of sensors, switches,
actuators, Transmitters
BMS
Areas
Category
Type
Sub-
Category
Application
AHU(Airside) Temperature(cum
Humidity/RH)
Sensor Room To know the actual Temp inside without cooling
Duct
To know flowing air Temp(& RH) inside duct for
supply & Return Air
Differential Pressure Across AHU Fan to check it is on or off physically,Differential Pressure
Switch Air
Across AHU Fan to check it is on or off physically,
across filter to check the status
Valve & Actuators Across cooling coil
Chillers, cooling
towers(Waterside)
Temperature(cum
Humidity/RH) Sensor Immersion
To Know water temperature from the chillers & to the
chillers
Outside To Know outside temp & RH
Differential Pressure
Switch Water
Across Pumps to check it is on or off physically, across
filter to check the status
Others
Level Transmitters Water To know the water level
Oil To know the oil level
CO2, CO sensor Room To know the air quality as in parking lot

44. 3. Cable
It generally can be categorized in two different applications-:
• Signal/Control Cable: From different field devices to controllers &
from Controllers to field devices to control the equipments
• Communication Cable: cable between different controllers, routers
& gateways for the purpose of intercommunication between& gateways for the purpose of intercommunication between
controllers.
• Integration cable: cable required for monitoring of third party
devices.

45. Cable Selection
BMS
Areas Category Cable Type Application
AHU Duct, Room Temp sensor 2c x 1 sqmm shielded Passive Temp(2c) signals from sensor to controllers
Temp cum humidity sensor 4c x 1sqmm shielded
Passive Temperature(2c) & Active(2c-power) RH measurement
from sensor to controllers
DP Switch for Air 2c x 1 sqmm shielded Passive Temp(2c) signals from switch to controllers
AHU FAN VFD 2c x 1 sqmm shielded Run status
2c x 1 sqmm shielded On/off status
2c x 1 sqmm shielded Relay output for VFD On/OFF Operation
Valve & Actuator 5c x 1sqmm shielded Control & Power (3c power and command) & Monitor (2c)

46. Integration
BMS
Areas Category Cable Type Application
Integartion DG
2c x 1.5 sqmm twisted pair
shielded
Integration is only to collect data from different devices to monitor
& generate reports
UPS
2c x 1.5 sqmm twisted pair
shielded
Integration is only to collect data from different devices to monitor
& generate reports
VAV's
2c x 1.5 sqmm twisted pair
shielded
Integration is only to collect data from different devices to monitor
& generate reports
2c x 1.5 sqmm twisted pairIntegration is only to collect data from different devices to monitor
Electrical Panels
2c x 1.5 sqmm twisted pair
shielded
Integration is only to collect data from different devices to monitor
& generate reports
Chillers
2c x 1.5 sqmm twisted pair
shielded
Integration is only to collect data from different devices to monitor
& generate reports
Security & Fire Alarm
system
2c x 1.5 sqmm twisted pair
shielded
Integration is only to collect data from different devices to monitor
& generate reports
Elevator
2c x 1.5 sqmm twisted pair
shielded
Integration is only to collect data from different devices to monitor
& generate reports

47. BMS Design Aspects
Basic data required before you start system design:
1. Input / Output summary for all subsystems, which need to either monitor or control.
2. Selection of appropriate field devices.
3. All integration devices & respective point details which has to be monitored.
4. Signal & Communication cable route layout (at least tentative).
5. Panel (Enclosure for controllers) location, BMS PC location.
Steps to follow for designing-:
1. Select the suitable controllers required for the requirement.
2. Select the enclosure to mount those controllers, which includes power supply for controllers & other wirings for field device
connection.
3. Now start with the AHU designing which includes signal & control cabling requirement for different field device selection as
per the requirement.
4. A typical AHU generally requires following field devices-Temperature cum Humidity sensor (or only Temp) in return & supply
duct. Differential Pressure Switch (For Air) across the AHU Fan, Filter, Actuators for AHU Line.
5. A typical AHU will have following wiring connection- Connection to all Field devices, Connection to electrical panels as per
I/O, connection to VFD’s.
6. A typical Chiller side will have following field devices-Immersion type temperature sensor (for supply & return pipes),
Butterfly Valve & Actuator in each chiller supply, differential Pressure sensor across main supply & return .
7. A typical chiller will have connection to all field devices, chiller panels, Pump VFD’s.

48. BMS Commissioning Aspects –
Air Side Commissioning- It comprises individual commissioning of AHU (Air handling Unit), CSU
(Ceiling Suspended Unit), Fans & associated field devices.
• We need to measure each field devices value during AHU commissioning as first task to make
sure all field devices are working & then all points can be put in a logic.
Water side commissioning – It comprises individual commissioning of Water cooled chillers, Air
cooled chillers, Cooling towers, Primary pumps, Secondary pumps, VFD’s & associated field
devicesdevices
• We need to measure each field device value & other connected points value individually before
putting them into logic.
Integration of Air side & water side in a logic-This is to integrate all independent system in logic.
Which can work automatically based on the user defined parameters without any conflict of
individual system functionality.

49. BMS Commissioning Aspects
Integration of monitoring points-
• This is to collect all data in BMS system for the purpose of monitoring only.
• PICS details i.e mapping details to be taken from respective equipment supplier.
• Protocol significance for integration purpose-whenever we say one device supports Modbus over
RS485, here RS 485 signifies physical channel (cable type) & communication port while Modbus
signifies data pattern. Therefore all devices in a loop must support same protocol & configure to
the same.
• Cable used for integration is 2 core x 1.5 sqmm shielded• Cable used for integration is 2 core x 1.5 sqmm shielded
• All monitored devices have to be looped in daisy chain connection to RS-485 port. Devices can
support different communication over different protocols. We need to make sure whenever making
a loop all devices should support same communication & protocol type. for instance Modbus over
RS485.
Client User interface (UI)
• Client can change parameters as temperature & humidity from UI as per the comfort level & all
basic information can be viewed on the UI.

50. SNAPS OF INSTALLATION

51. PANEL

52. SCHEMATICS-AHU

53. SCHEMATICS-TFA

54. SCHEMATICS-SCRUBBER

55. Water Tank

56. EXHAUST FAN

57. CHILLER

58. CHW & CDW PUMPS

59. COOLING TOWER