Building Management System-CPD - Part 1.pdf
- 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..? A building management system (BMS) or a (more recent terminology) building automation system (BAS) is a computer-based control system installed in buildings that controls and monitors the building's mechanical and electrical equipment such as Air Conditioning , Heating Cooling, ventilation, lighting, power systems, fire systems, and security systems and more…. The objectives • Improved occupant comfort, • Efficient operation of building systems, • Reduction in energy consumption and operating costs, • Improved life cycle of utilities,
- 4. Terminology…. ▪ The following terms are used interchangeably and refer to the same thing: o Building Automation System (BAS) o Building Management System (BMS) o Building Control System (BCS) o Building Energy Management System (BEMS) o Facility Management System (FMS) ▪ IBMS usually refers to “Intelligent Building Management System” or “Integrated Building Management System” and refers to a system where BAS, Fire, Security ( CCTV , ACS ) and sometimes other systems are integrated into a common system ▪ Maintenance Management System (MMS) or Computerized Maintenance Management System (CMMS) is a different type of system focused on the issuing and management of work orders
- 5. ▪ Connects to various mechanical and electrical equipment in the building ▪ Automates some control strategies such as automatically turning equipment on / off according to a time schedule ▪ Allows an operator sitting at a computer to view key information about the building → “ “ ▪ Allows an operator sitting at a computer to control some of the equipment in the building → “ “ ▪ Maintains an audit trail of what happened and when it happened ▪ Maintains historical data for selected information (i.e. room temperature) ▪ Alerts the operator when readings fall outside of normal range (i.e. breaker trips, temperature too warm, etc.) A Building Automation System:
- 6. Benefits of a Building Automation System Improved indoor environment quality • Comfortable living and working environment • Better temperature and humidity control • Good air quality • Energy Savings (automatic control strategies ) Faster response to .. • Occupant needs • End-user complaints • Trouble conditions Maintenance Savings. • Efficient control gives less wear and strain of mechanical equipment. • Provides longer life • Runtime monitoring alerts timely maintenance of equipment • Avoids expensive failures • Allows an operator sitting at a computer to view key information about the building ➔ Improve building operations (understand what is going on in the building) Individual Switches for each electrical equipment
- 7. Energy Savings • Eliminates unnecessary system operation. • Accurate energy usage information • Helps you to take steps to reduce energy consumption like. • Optimum-Start • Night-Purging • Time-Scheduling Consolidated facility control. • One point centralized operation • Simpler operation • Reduces time and resources Reduced operator training • On-screen instructions • User-friendly graphic displays • Simpler operation programmed for routine and repetitive operation
- 8. Improved management reporting • Provides valuable real-time data • Creates reports, charts... • Critical information immediately sent to printers, emailed or sent via SMS 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
- 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 Pv is 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 Field level refers to application specific controllers, such as terminal devices including fan coil units, and variable air volume boxes and control peripherals, such as sensors and valve or damper actuators. System level also called the automation level, is associated with controllers serving the main plant such as the air handling units, chillers and boiler control. Management level comprises the BMS server and the operator workstation, also known as the head end or building dashboard. The management level of control allows the management and monitoring of the control system from a single point. Enterprise level. This sits above the other levels usually within a corporate network to provide data analysis such as asset management.
- 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 • Sophistication in the computing and software functions cannot compensate for inaccurate information. ( By poor quality , wrong mounting) • There are 3 elements • Sensing element – a component that undergoes measurable change ( V,I or R) • Transducer – an active signal that produces an electrical signal which is a function of the change in the sensing element. • Transmitter – Standardized function of the change. • In Practice Transducer and Transmitter combined. Also do remove noise , averaging over time, linearization. • Some time sensing element directly connect to the Controller then Signal conditioning take place in the Controller. • Sensor Types • Status Sensor Provides binary outputs ( whether signal is above the threshold or not) • Analogue Sensor Not discrete signal • Sensor Controller – 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 Proximity other 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 ( MODbus RS 485)
- 30. Sensors…. Stats Sensor Passive Analogue Sensor Active Analogue Sensor Thermal well
- 31. Technical Specifications of Sensors… • Range – operation Range • Sensitivity – how much will the input variable must change to produce an output • Linearity – if not linear , signal conditioning needed • Resolution - the ability of a sensor to see small differences in readings • Drift - This is the low frequency change in a sensor with time • Stability - another way of stating drift. That is, with a given input you always get the same output • Repeatability - This is the ability of a sensor to repeat a measurement when put back in the same environment. • Hysteresis - A linear up and down input to a sensor, results in an output that lags the input • Response Time - The time constant of any sensor is defined as the time required for that sensor to respond to 63.2 of it. • Accuracy - is the degree of closeness of measurements of a quantity to that quantity's actual (true) value. • Precision - also called reproducibility or repeatability, is the degree to which repeated measurements under unchanged conditions show the same results
- 32. Input Units and Signal Conversion • Input & Output interface provide link to the Microprocessor ( No direct Link) • Analogues signals to be converted to Bits and Bytes • A/D conversion and Sampling • Sampling frequency twice higher than signal frequency ( Shannon’s sampling theory) • In Practices 10 times higher • A/D conversion accuracy
- 33. Sampling….. One of the most important functions of any building automation system is the collection of continuous measurement data, at regular time intervals from large numbers of individual measurement sensors, and ‘binary’ state data from detectors such as smoke alarms.
- 34. 8 Bit A/D Conversion Vs 16 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 “Analogue sensors produce continuous output signals ( eg voltage) which is usually proportional to the amount measured. Physical quantities such as speed, pressure, temperature, pressure, strain and displacement are all analogue quantities.” V = IR Q = CV
- 41. Digital Switches (Sensors) “signal that is a representation of a sequence of discrete values”
- 42. Temperature Measuring • 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. • Excellent accuracy over a wide temperature range (from -200 to +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 “closeness of agreement” • Insulation Resistance: Error caused by the inability to measure the actual resistance of element. • Stability: Ability to maintain R vs T over time as a result of thermal exposure. • Repeatability: Ability to maintain R vs T under the same conditions after experiencing thermal cycling throughout a specified temperature range. • Hysteresis: Change in the characteristics of the materials from which the sensor is built due to exposures to varying temperatures. • Self Heating: Error produced by the heating of the sensor element due to the power applied. • Time Response: Errors are produced during temperature transients because the sensor cannot respond to changes fast enough. • Thermal EMF: Thermal EMF errors are produced by the EMF adding to or subtracting from the applied sensing voltage, primarily in DC systems. 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 𝑅𝑥 = 𝑉𝑖 − 2𝑉0 𝑉𝑖 + 2𝑉0 𝑅 𝑅= R1, R2, R3 Rx = RRTD + 2RL 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 Type Primary 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 Large Change 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 humistor is 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 Polymer Relative humidity Inexpensive contamination Chilled Mirror Dew 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, Duct Static, Filter DP Inexpensive Signal Conditioning is complex, low output Inductive Low Pressure Air, fume hood DP Rugged Construction Expensive , 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 range Calibration problem Potentiometric General 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. • Pitot Tubes • Turbines Flow Sensor/meters Annubar Venturi Flow meter
- 65. Flow Sensor/meters • Orifice Plate • Hot Wire Anemometers
- 66. Electromagnetic Flow Meters use a magnetic field applied to the metering tube, which results in a potential difference proportional to the flow velocity perpendicular to the flux lines The potential difference is sensed by electrodes aligned perpendicular to the flow and the applied magnetic field.
- 68. Ultrasonic Flow meters • There are two main types of Ultrasonic flow meters: Doppler and transit time. • by averaging the difference in measured transit time between the pulses of ultrasound propagating into and against the direction of the flow • by measuring the frequency shift from the Doppler effect • https://www.youtube.com/watch?v=Bx2RnrfLkQg
- 69. Transit Time Vs Doppler
- 70. Flow meters Sensor Type Primary Use Advantages Disadvantages Pitot Tube Air Inexpensive clogging Orifice Plate Water , Steam Inexpensive, many pipe size Can erode, accuracy depend on diameter Venturi Tubes Water, Air Lowest Head loss of insertion type Large in size more costly Hot Wire Air Measure mass flow, not contaminated fragile Turbine Steam, Water Good turndown ration Wear , can damage Vortex Shedding Water accurate Complicated signal conditioning Ultrasonic Water nonintrusive Most expensive
- 71. End