Building Management System-CPD - Part 1.pdf

Why BAS ( BMS)…?
• Early days buildings were very simple with few facilities and services
• With time many services were introduced & crowded
• Now-a-days buildings are very complex with many services and higher
occupancy ( high consumptions of energy)
• Central Monitoring and controlling needed

1. Building Automation System
Jagath Wickramasekara,
Bsc , University of Moratuwa

2. Why BAS ( BMS)…?
•Early days buildings were very simple with few facilities and services
•With time many services were introduced & crowded
•Now-a-days buildings are very complex with many services and higher
occupancy ( high consumptions of energy)
•Central Monitoring and controlling needed

3. What is a Building Automation System..?
Abuildingmanagementsystem(BMS)ora(morerecentterminology)building
automationsystem(BAS)isacomputer-basedcontrolsysteminstalledin
buildingsthatcontrolsandmonitorsthebuilding'smechanicalandelectrical
equipmentsuchasAirConditioning,HeatingCooling,ventilation,lighting,
powersystems,firesystems,andsecuritysystemsandmore….
The objectives
•Improved occupant comfort,
•Efficient operation of building systems,
•Reduction in energy consumption and operating
costs,
•Improved life cycle of utilities,

4. Terminology….
▪Thefollowingtermsareusedinterchangeablyandrefertothesamething:
oBuildingAutomationSystem(BAS)
oBuildingManagementSystem(BMS)
oBuildingControlSystem(BCS)
oBuildingEnergyManagementSystem(BEMS)
oFacilityManagementSystem(FMS)
▪IBMSusuallyrefersto“IntelligentBuildingManagementSystem”or“IntegratedBuilding
ManagementSystem”andreferstoasystemwhereBAS,Fire,Security(CCTV,ACS)
andsometimesothersystemsareintegratedintoacommonsystem
▪MaintenanceManagementSystem(MMS)orComputerizedMaintenanceManagement
System(CMMS)isadifferenttypeofsystemfocusedontheissuingandmanagementof
workorders

5. ▪Connectstovariousmechanicalandelectricalequipmentinthebuilding
▪Automatessomecontrolstrategiessuchasautomaticallyturningequipment
on/offaccordingtoatimeschedule
▪Allowsanoperatorsittingatacomputertoviewkeyinformationaboutthe
building→“ “
▪Allowsanoperatorsittingatacomputertocontrolsomeoftheequipmentin
thebuilding→“ “
▪Maintainsanaudittrailofwhathappenedandwhenithappened
▪Maintainshistoricaldataforselectedinformation(i.e.roomtemperature)
▪Alertstheoperatorwhenreadingsfalloutsideofnormalrange(i.e.breaker
trips,temperaturetoowarm,etc.)
A Building Automation System:

6. Benefits of a Building Automation System
Improvedindoorenvironmentquality
•Comfortablelivingandworkingenvironment
•Bettertemperatureandhumiditycontrol
•Goodairquality
•EnergySavings(automaticcontrolstrategies)
Fasterresponseto..
•Occupantneeds
•End-usercomplaints
•Troubleconditions
MaintenanceSavings.
•Efficientcontrolgiveslesswearandstrainofmechanicalequipment.
•Provideslongerlife
•Runtimemonitoringalertstimelymaintenanceofequipment
•Avoidsexpensivefailures
•Allowsanoperatorsittingatacomputertoviewkeyinformationaboutthe
building➔Improvebuildingoperations(understandwhatisgoingoninthe
building)
Individual Switches for each electrical
equipment

7. EnergySavings
•Eliminatesunnecessarysystemoperation.
•Accurateenergyusageinformation
•Helpsyoutotakestepstoreduceenergyconsumptionlike.
•Optimum-Start
•Night-Purging
•Time-Scheduling
Consolidatedfacilitycontrol.
•Onepointcentralizedoperation
•Simpleroperation
•Reducestimeandresources
Reducedoperatortraining
•On-screen instructions
•User-friendly graphic displays
•Simpler operation programmed for routine and repetitive operation

8. Improvedmanagementreporting
•Providesvaluablereal-timedata
•Createsreports,charts...
•Criticalinformationimmediatelysenttoprinters,emailedorsentviaSMS
Timely and effective control
•Alerts your employees when your facility is not operating correctly
•Reduce troubleshooting and down time.
•Remote access connectivity without site visits.
• Performance Benchmarking
•Facilitates the overall system performance measurement
•Comparison with set benchmarks

9. & Servers
Or Gateways/ routers
Communication
Communication
Communication
Management Level
Automation Level
Field Level
Building Automation System Architecture

11. Controlling
Plant Controller
Your
Choice
Output

12. Little Bit About Control Theory ….. ☺
Controlling
•Open Loop Control
•Closed Loop Control
Disturbances
Disturbances

13. Feedback Controller
Error = SetPont–Controller Variable →e = STP-Pv
Because of above precision of sensor is very important
Error –e determines Pvis too high or low
Control signal is proportional to error
Feedback System
Benefit of Feedback Control
•Ease of Adjustment
•Reduction in External disturbances
•Reduction of Steady State errors
•Decrease in the sensitivity of the variations in the parameters of the process ( due to wear aging )
Disadvantages
Instability ( overcorrection of process inputs and delay in component dynamics)
Always try open loop first , then try Closed Loop

14. Controllers/ Control Concepts
•Two Positions –2P
•Floating Control –3P
•Proportional -P
•Proportional plus Integral -PI
•Proportional Plus integral plus Derivatives -PID
•Artificial intelligent -AI
Modulating Control

15. Energy Consumption of a Building

16. What equipment do consume energy in HVAC…?
•Chillers
•Chilled ( Primary , secondary) water Pumps/ Condenser water pumps
•Cooling Tower
•AHUs/ FCU/VAV/CAV
Air Side Control Strategies & Water side control Strategies

17. Factors influence Thermal Comfort
•Air Temperature
•Air Velocity
•RH
•Radiant Environment
•Clothing & Activity Level
HVAC system maintains,
•Temperature
•Humidity
•Air Distribution
•Indoor Air Quality
To ensure the comfortable and healthy environment
Thermal comfort and minimum health requirement must be achieved by the basic controls
of AC system, while the optimal control of the systems aims at providing satisfied thermal
comfort and indoor air quality with minimum energy input

18. BMS Architecture…..
A BMS architecture typically has three levels:
•Field level,
•System level,
•Management level
Fieldlevelreferstoapplicationspecificcontrollers,suchas
terminaldevicesincludingfancoilunits,andvariableair
volumeboxesandcontrolperipherals,suchassensorsand
valveordamperactuators.
Systemlevelalsocalledtheautomationlevel,isassociated
withcontrollersservingthemainplantsuchastheair
handlingunits,chillersandboilercontrol.
ManagementlevelcomprisestheBMSserverandthe
operatorworkstation,alsoknownastheheadendor
buildingdashboard.Themanagementlevelofcontrol
allowsthemanagementandmonitoringofthecontrol
systemfromasinglepoint.
Enterpriselevel.Thissitsabovetheotherlevelsusually
withinacorporatenetworktoprovidedataanalysissuch
asassetmanagement.

19. & Servers
Or Gateways/ routers
Communication
Communication
Communication
Management Level
Automation Level
Field Level

20. IOT Architecture

21. Field Level
•Sensor (www.dwyer-inst.com, Omicron, www.Kele.com)
•Actuators
•FCU Controller
•VAV Box Controller

22. Sensor
•Sophisticationinthecomputingandsoftwarefunctionscannotcompensatefor
inaccurateinformation.(Bypoorquality,wrongmounting)
•Thereare3elements
•Sensingelement–acomponentthatundergoesmeasurablechange(V,IorR)
•Transducer–anactivesignalthatproducesanelectricalsignalwhichisafunctionofthe
changeinthesensingelement.
•Transmitter–Standardizedfunctionofthechange.
•InPracticeTransducerandTransmittercombined.Alsodoremovenoise,averagingover
time,linearization.
•SometimesensingelementdirectlyconnecttotheControllerthenSignalconditioning
takeplaceintheController.
•SensorTypes
•StatusSensorProvidesbinaryoutputs(whethersignalisabovethethresholdornot)
•AnalogueSensorNotdiscretesignal
•SensorController–Thermostats

23. Sensors…
•Analogue sensors –2 type
•Passive Sensor –No transducer available , no external power needed
•Active Sensor –signal conditioning is incorporated in the sensor , external power needed
•Standard Electrical Signals
•4 –20 mA –Current Signal ( 0 ~ 20 mA)
•0 –10 Vdc–Voltage Signal ( 0 ~5 Vdc)
•Voltage Free Contact ( NO or NC)
•Pulses
•Via High Level interfacing
•Additional Data Processing –calibration, compensation, calculation –Eg-Enthalpy

24. Loop powered Sensors ( 2 wire )
•Voltage Drop
3 V Max
3V @ 20 mA
150 Ohms

25. 0 –10 Vdc Vs 4 ~ 20 mA
•True zero is not possible
•Cable resistance is immaterial for 4 ~ 20 mA
•Current regulator is in action
•Low sensitivity to Electrical noise
•Easy detect loss of signal or power
•Propper Isolation needed in each 4 ~ 20 mA loop

28. Noise
•Ground Loop
•Poor Wiring Practices
•Improper Grounding
•Close Proximityother Equipment
•Long wire Leads picking up RF
•Poorly designed product Circuitry
•

29. Best Practices
•No power & Signal Together
•Away from magnetics field sources –TF , Motors , Contactors ( or keep 90
Deg –Parallel more susceptible )
•Twisted Pairs / short wires / shielded cables with proper grounding
•Selecting signal type with more noise immunity ( low voltage signals are more
susceptible to noise than current signals)
•Converting signals to Digital whenever possible ( MODbusRS 485)

30. Sensors….
Stats Sensor
Passive Analogue Sensor
Active Analogue Sensor
Thermal well

31. Technical Specifications of Sensors…
•Range–operationRange
•Sensitivity–howmuchwilltheinputvariablemustchangetoproduceanoutput
•Linearity–ifnotlinear,signalconditioningneeded
•Resolution-theabilityofasensortoseesmalldifferencesinreadings
•Drift-Thisisthelowfrequencychangeinasensorwithtime
•Stability-anotherwayofstatingdrift.Thatis,withagiveninputyoualwaysgetthesame
output
•Repeatability-Thisistheabilityofasensortorepeatameasurementwhenputbackin
thesameenvironment.
•Hysteresis-Alinearupanddowninputtoasensor,resultsinanoutputthatlagstheinput
•ResponseTime-Thetimeconstantofanysensorisdefinedasthetimerequiredforthat
sensortorespondto63.2ofit.
•Accuracy-isthedegreeofclosenessofmeasurementsofaquantitytothatquantity's
actual(true)value.
•Precision-alsocalledreproducibilityorrepeatability,isthedegreetowhichrepeated
measurementsunderunchangedconditionsshowthesameresults

32. Input Units and Signal Conversion
•Input&Outputinterfaceprovidelinkto
theMicroprocessor(NodirectLink)
•AnaloguessignalstobeconvertedtoBits
andBytes
•A/DconversionandSampling
•Samplingfrequencytwicehigherthansignal
frequency(Shannon’ssamplingtheory)
•InPractices10timeshigher
•A/Dconversionaccuracy

33. Sampling…..
Oneofthemostimportantfunctionsofanybuildingautomationsystemisthe
collectionofcontinuousmeasurementdata,atregulartimeintervalsfromlarge
numbersofindividualmeasurementsensors,and‘binary’statedatafrom
detectorssuchassmokealarms.

34. 8 Bit A/D Conversion Vs16 Bits A/D Conversion

35. Solution….
80 C
-20 C
10 Vdc
0 Vdc
0 255
8 Bit A/D Converter

36. •Accuracy: The claimed accuracy for a sensor does not guarantee that the
same accuracy will be achieved at the controller or BMS supervisor, or that it
will be maintained over the operating life of the sensor. The accuracy of the
overall measurement system depends on many factors including:
accuracy of the sensing element, sensitivity of sensor element, insensitivity of
sensor element to interacting variables, stability, hysteresis, mounting, signal
conditioning, and A/D conversion.
Sensor Range A/D Measuring Range

37. Sensors

39. Sensors Used in BMS
•Analogue signal sensors
•Temperature sensor / type
•Pressure sensor /type
•Humidity sensor / type
•CO2 sensor
•Flow sensor / type
•Other sensor ( vibration , air speed, CO ,VOC, level )
•Digital signal sensors
•Switches
•Status detection
•Detection sensor
•Pulse Generator & Metering
•meters

40. Analogue Sensor
“Analoguesensorsproducecontinuousoutputsignals(egvoltage)whichisusually
proportionaltotheamountmeasured.Physicalquantitiessuchasspeed,pressure,
temperature,pressure,strainanddisplacementareallanaloguequantities.”
V = IR
Q = CV

41. Digital Switches (Sensors)
“signalthatisarepresentationofasequenceofdiscretevalues”

42. TemperatureMeasuring
•Bimetal
•Rod and Tube
•Sealed Baloon
•Remote Bulb
•Thermistor
•Resistance Temperature Detector –RTD
•Thermocouple
Bimetal –for Both ON/OFF and Proportional controlling
Less expensive , accuracy will drift over time
Rod & Tube –Metal Rod and Tube combination –immersion type temp sensor
Sealed Bellows / Remote Bulb–a balloon filled with gas , vapor –old thermostats

43. Thermistor
•A thermistor is a type of resistor whose resistance varies
significantly with temperature
•Use Ceramic , Polymer
•Mostly Nonlinear
•Large response for small change
•Low cost
•Good for a limited range
NTC–Type Sensor / PTC –Type Sensor /RTD

44. Resistance Temperature Detector –RTD
•Metal
•Platinum, Nickel, Copper , ect
•Platinum liner 0 ~ 300 F 0.3% -Tolerance
•Some time Integrated to a Circuit to produce 0~10 Vdc, 4 ~ 20 mA
•PT1000-has a resistance of 1000 ohms at 0 °C.
•Excellentaccuracyoverawidetemperaturerange(from-200to
+850°C.
Pt 1000 temp Characteristic curve

45. Thermocouple
•A thermocouple is a temperature-measuring device consisting of two dissimilar
conductors that contact each other at one or more spots
•Suitable for High Temperature applications

46. •Interchangeability:the“closenessofagreement”
•InsulationResistance:Errorcausedbytheinabilitytomeasuretheactualresistance
ofelement.
•Stability:AbilitytomaintainRvsTovertimeasaresultofthermalexposure.
•Repeatability:AbilitytomaintainRvsTunderthesameconditionsafter
experiencingthermalcyclingthroughoutaspecifiedtemperaturerange.
•Hysteresis:Changeinthecharacteristicsofthematerialsfromwhichthesensoris
builtduetoexposurestovaryingtemperatures.
•SelfHeating:Errorproducedbytheheatingofthesensorelementduetothepower
applied.
•TimeResponse:Errorsareproducedduringtemperaturetransientsbecausethe
sensorcannotrespondtochangesfastenough.
•ThermalEMF:ThermalEMFerrorsareproducedbytheEMFaddingtoorsubtracting
fromtheappliedsensingvoltage,primarilyinDCsystems.
Biggest Problems of the sensors are the Errors
Sources of error of Sensors

47. Type Of Temperature sensor
1.Room sensors for wall mounting
2.Room sensors for flush mounting
3.Duct sensors
4.Immersion sensors
5.Strap-on sensors
6.Outside sensors
7.Cable sensors

48. Parameters of Temperature Sensors

51. Measuring the R in DDC
Two Wires
??????
??????=
??????
??????−2??????
0
??????
??????+2??????
0
??????
??????= R1, R2, R3
R
x= R
RTD+ 2R
L
Three wires
Four Wire
Four Wire -Kelvin Connection –for
laboratory usage mostly

52. Time Constant
•The Thermal Time Constant is a measurement of the time required for the
sensor to respond to a change in the ambient temperature. The technical
definition of Thermal Time Constant is, "The time required for a sensor to
change 63.2% of the total difference between its initial and final body
temperature when subjected to a step function change in temperature, under
zero power conditions".

53. Temperature Sensors
Sensor TypePrimary Use Advantages Disadvantages
RTD General Purpose,Air, Water, Steam Very Accurate, Interchangeable,
Stable
Relatively Expensive , not
very sensitive
Thermistor High Sensitivity Applications, Chilled
water metering
LargeChange in Resistance for a
small change in Temperature -
Sensitivity
Nonlinear, Fragile, Self-
heating
Thermocouple High Temperature Applications Boiler ,
Stack gas
Inexpensive , Self-powered,
Rugged
Low –Voltage output,
not very sensitive

54. Humidity Sensor
•Thin-film polymers sensor
•Chilled mirror sensor
•Relative humidity / Dew point
•Hygroscopic Element is used , mechanical operation
•A humistoris a type of variable resistor whose resistance varies based on
humidity.
•An Active Sensor

55. Humidity Sensor
Chilled mirror sensor

56. Humidity Sensors
Sensor Type Primary Use Advantages Disadvantages
Thin Film PolymerRelative humidityInexpensive contamination
Chilled MirrorDew point
Temperature
Precise
measurement
Periodic Cleaning,
expensive

57. Pressure Sensor
•Absolute pressure sensor: measures the pressure relative to perfect vacuum.
•Gauge pressure sensor: measures the pressure relative to atmospheric
pressure.
•Vacuum pressure sensor: Vacuum pressure sensors measure pressure that is
less than 0 PSI.
•Differential pressure sensor: measures the difference between two pressures
points.
•Sealed pressure sensor: Measures the pressure relative to some fixed

58. Pressure Sensors

59. Pressure Sensors
•Capacitive
•Strain Gauge
•Inductive Transducers

60. Pressure Sensor
•Piezoelectric
•Potentiometric

61. Pressure Sensors
Sensor Type Primary Use Advantages Disadvantages
Capacitive Low Pressure Air, DuctStatic,
Filter DP
Inexpensive Signal Conditioning is
complex, low output
Inductive Low Pressure Air, fume hood
DP
Rugged ConstructionExpensive ,
temperature
compensation may be
difficult
Strain Gauge High Pressure , Chilled water
, Steam
Linear Output Low Output Signal
Piezoelectric Fluctuating pressure , sound,
mechanical vibration
Wider Pressure rangeCalibrationproblem
PotentiometricGeneral Purpose Inexpensive , High
output
Low accuracy , large
size,wear and tear

62. Flow measurements ( Air & Liquid )
Flow Measuring is mostly done through Pressure Measuring but not always
Total Pressure = Static Pressure + Velocity Pressure
Air Velocity (fpm) = 4005 Air Velocity pressure

63. •PitotTubes
•Turbines
Flow Sensor/meters
Annubar
VenturiFlow meter

64. Flow Sensor/meters
•Vortex

65. Flow Sensor/meters
•Orifice Plate
•Hot Wire Anemometers

66. Electromagnetic Flow Meters
useamagneticfieldappliedtothemeteringtube,whichresultsinapotentialdifference
proportionaltotheflowvelocityperpendiculartothefluxlines
Thepotentialdifferenceissensedbyelectrodesalignedperpendiculartotheflowandthe
appliedmagneticfield.

67. https://www.youtube.com/watch?v=f949gpKdCI4

68. Ultrasonic Flow meters
•TherearetwomaintypesofUltrasonicflowmeters:Dopplerandtransittime.
•byaveragingthedifferenceinmeasuredtransittimebetweenthepulsesof
ultrasoundpropagatingintoandagainstthedirectionoftheflow
•bymeasuringthefrequencyshiftfromtheDopplereffect
•https://www.youtube.com/watch?v=Bx2RnrfLkQg

69. Transit Time VsDoppler

70. Flow meters
Sensor TypePrimary UseAdvantages Disadvantages
PitotTube Air Inexpensive clogging
Orifice PlateWater , SteamInexpensive, many pipe
size
Can erode, accuracy
depend on diameter
VenturiTubesWater,Air Lowest Head loss of
insertion type
Large in size more costly
Hot Wire Air Measure mass flow, not
contaminated
fragile
Turbine Steam, WaterGood turndown rationWear , can damage
Vortex SheddingWater accurate Complicated signal
conditioning
Ultrasonic Water nonintrusive Most expensive

71. End