Fundamentals Of HVAC Control Systems - Ibse.hk
ASHRAE Hong Kong Chapter Technical WorkshopFundamentals of HVACControl Systems18, 19, 25, 26 April 2007 2007 ASHRAE Hong Kong ChapterSlide 1
About the Speakers“The Black Hairs” Dr. Sam C. M. HuiDept. of Mechanical Engineering, HKU Over 18 years of experience in teaching,research, consultancy & design Mr. William YickBusiness Development Director ofJohnson Controls Over 30 years of professional experience inthe HVAC controls “The White Hairs” 2007 ASHRAE Hong Kong ChapterSlide 2
Know The Instructor Dr. Sam C M Hui – Dept. of Mech. Engg.,The University of Hong Kong PhD, BEng(Hons), CEng, CEM, MASHRAE, MCIBSE,MHKIE, MIESNA, LifeMAEE, AssocAIAHKU Dept. of Mechanical Engineering (4.5 years)HKU Dept. of Architecture (6 years)Asia Pacific Energy Research Centre, Japan ( 1 year)PhD study (4 years)Associated Consulting Engineers (2 years)Current role in ASHRAE: President of ASHRAE Hong Kong Chapter 2007 ASHRAE Hong Kong ChapterSlide 3
ASHRAE Study Guide “Fundamentals of HVAC Control Systems”List price at US 150 Included for each participant of the workshop Divided into 10 chapters Typical structure of each chapterà Instructionsà Study Objectivesà Main Bodyà The Next Stepsà Summaryà Bibliographyà Skill Development Exercises 2007 ASHRAE Hong Kong ChapterSlide 4
Main Topics in Study Guide 1. Introduction to HVAC Control Systems2. Basic of Electricity3. Control Valves and Dampers4. Sensors and Auxiliary Devices5. Control Diagrams and Sequences6. Self-Powered Controls7. Electric Controls8. Pneumatic Controls9. Analog Electronic Controls10. Digital Controls(* Practical considerations and applications are added too.) 2007 ASHRAE Hong Kong ChapterSlide 5
Assumptions & Focus AssumptionsAudience knows the basic HVAC equipment &terminology Audience members have interest in HVAC controlsystems and may have some experience before orworking on it now Focus of this workshopBasic concepts of HVAC control systems Practical considerations and applications Updated with latest developments too, e.g. DDC system 2007 ASHRAE Hong Kong ChapterSlide 6
Chapter 1Introduction to HVACControl Systems 2007 ASHRAE Hong Kong ChapterSlide 7
Why We Need Controls? To regulate the output of systems andequipment Such as your carFor HVAC system, to regulate themovement of air, water, electricity toobtain desired indoor conditions Also for energy management and safety 2007 ASHRAE Hong Kong ChapterSlide 8
Control System Types Self-powered controlsElectric controlsPneumatic controlsAnalog electronic controlsDigital controls Direct Digital Control (DDC)* Most control systems today use acombination of the 5 system types Hybrid control system 2007 ASHRAE Hong Kong ChapterSlide 9
Block Diagram of a Control Loop 2007 ASHRAE Hong Kong ChapterSlide 10
Simple Heating System 2007 ASHRAE Hong Kong ChapterSlide 11
Key Terms Controlled variableControl pointSetpointSensorControlled deviceProcess plantControllerControl loopClosed loop (i.e. w/ feedback)Open loop (i.e. w/o feedback) 2007 ASHRAE Hong Kong ChapterSlide 12
Some Definitions Automatic control system: A system thatreacts to a change or imbalance in thevariable it controls by adjusting othervariables to restore the system to thedesired balance.Controlled Variable: The quantity orcondition that is measured and controlled.Controller: A device that senses changesin the controlled 2007 ASHRAE Hong Kong ChapterSlide 13
[Source: Honeywell, 1997. Engineering Manual of Automatic Control: for Commercial Buildings] 2007 ASHRAE Hong Kong ChapterSlide 14
Basic Types of Control Modes Two-position controlFloating controlModulating control 2007 ASHRAE Hong Kong ChapterSlide 15
Two-Position Control 2007 ASHRAE Hong Kong ChapterSlide 16
Two-Position ControlWith Anticipator 2007 ASHRAE Hong Kong ChapterSlide 17
Step Control 2007 ASHRAE Hong Kong ChapterSlide 18
Floating Control 2007 ASHRAE Hong Kong ChapterSlide 19
P-I-D Control 2007 ASHRAE Hong Kong ChapterSlide 20
Proportional-Only Control 2007 ASHRAE Hong Kong ChapterSlide 21
P-I Control 2007 ASHRAE Hong Kong ChapterSlide 22
Proportional ControlProportional-Integral(PI) ControlProportional-IntegralDerivative (PID) Control[Source: Honeywell, 1997. Engineering Manual of Automatic Control: for Commercial Buildings] 2007 ASHRAE Hong Kong ChapterSlide 23
Recommended control modes for HVAC systemApplicationControl modeSpace temperatureP, PIDMixed air temperaturePI, Enhanced PIDCoil discharge temperaturePI, Enhanced PIDChiller discharge temperaturePI, Enhanced PIDAir flowPI (use wide proportional band & afast reset rate), PIDFan static pressurePI, Enhanced PIDHumidityP, possibly PI for tight controlDewpoint temperatureP, possibly PI for tight control[Source: Honeywell, 1997. Engineering Manual of Automatic Control: for Commercial Buildings] 2007 ASHRAE Hong Kong ChapterSlide 24
Pulse Width Modulation 2007 ASHRAE Hong Kong ChapterSlide 25
Time-Proportioning Control 2007 ASHRAE Hong Kong ChapterSlide 26
Proportional Control(Gain and Loop Tuning – adjust the %gain to meet the specific application) 2007 ASHRAE Hong Kong ChapterSlide 27
P-I Control(Loop Tuning is an “art”. Usually tune the P gain first, then adjust I gain to eliminate offset) 2007 ASHRAE Hong Kong ChapterSlide 28
P-I-D Control(Derivative is seldom used because HVAC system response is rather slow.) 2007 ASHRAE Hong Kong ChapterSlide 29
Proportional Control 2007 ASHRAE Hong Kong ChapterSlide 30
Control Action & Normal Position 2007 ASHRAE Hong Kong ChapterSlide 31
SequencingTypical control ranges:- Pneumatic 3-13 psi- Electronic 2-12 VdcControl range(heating) 2007 ASHRAE Hong Kong ChapterControl range(cooling)Slide 32
Chapter 2Basics of ElectricityIntroduce simple electrical circuits and common devices for controlling electricalpower in HVAC systems. Some concepts of electronics are also helpful.Common devices: relays, transformers, starters 2007 ASHRAE Hong Kong ChapterSlide 33
Simple Electrical CircuitV IxR 2007 ASHRAE Hong Kong ChapterP V x I I2 x RSlide 34
Water Tank Analogy 2007 ASHRAE Hong Kong ChapterSlide 35
Parallel Circuits 2007 ASHRAE Hong Kong ChapterSlide 36
Series Circuits 2007 ASHRAE Hong Kong ChapterSlide 37
Alternating Voltage 2007 ASHRAE Hong Kong ChapterSlide 38
Simple AC Circuit 2007 ASHRAE Hong Kong ChapterSlide 39
Capacitor in DC Circuit 2007 ASHRAE Hong Kong ChapterSlide 40
Voltage & Current Out of Phase 2007 ASHRAE Hong Kong ChapterSlide 41
Magnetic Field 2007 ASHRAE Hong Kong ChapterSlide 42
Inductor in DC Circuit 2007 ASHRAE Hong Kong ChapterSlide 43
3-Phase VoltageP V x I x PF x 3 2007 ASHRAE Hong Kong ChapterSlide 44
Transformer 2007 ASHRAE Hong Kong ChapterSlide 45
120/208V Service(4-wire Wye Connected) 2007 ASHRAE Hong Kong ChapterSlide 46
480/277V Service(4-wire Wye Connected) 2007 ASHRAE Hong Kong ChapterSlide 47
Electromagnetic Relay(On/Off signal; a type of remote-controlled switch) 2007 ASHRAE Hong Kong ChapterSlide 48
Simple DC Circuit With Relay 2007 ASHRAE Hong Kong ChapterSlide 49
Multipole Relay 2007 ASHRAE Hong Kong ChapterSlide 50
Single- & Double-Throw Contacts 2007 ASHRAE Hong Kong ChapterSlide 51
Across-the-Line Motor Starter(Start/stop control and overload protection) 2007 ASHRAE Hong Kong ChapterSlide 52
Starter With H-O-A Switch(H-O-A hand-off-auto) 2007 ASHRAE Hong Kong ChapterSlide 53
Starter With H-O-A Switch& Aux. Contact 2007 ASHRAE Hong Kong ChapterSlide 54
Starter With ManualStart/Stop Buttons 2007 ASHRAE Hong Kong ChapterSlide 55
Magnetic Starter WithLife Safety Fan Wiring 2007 ASHRAE Hong Kong ChapterSlide 56
Variable Speed Drives Inverter VariableFrequency DriveVSD variable speed driveASD adjustable speed driveVFD variable frequency drive 2007 ASHRAE Hong Kong ChapterSlide 57
Sine-Coded PWM Waveform(PWM pulse-width modulation) 2007 ASHRAE Hong Kong ChapterSlide 58
Variable Speed DriveWith Optional Starter(the starter is provided as a backup, in case the VSD fails) 2007 ASHRAE Hong Kong ChapterSlide 59
Simple Relay Logic(Boolean logic notation, e.g. if (A or B) then C) 2007 ASHRAE Hong Kong ChapterSlide 60
Relay Logic WithDouble-Throw Contact 2007 ASHRAE Hong Kong ChapterSlide 61
Three-Way Light Switch 2007 ASHRAE Hong Kong ChapterSlide 62
Symbols for Elec. Logic Devices 2007 ASHRAE Hong Kong ChapterSlide 63
Voltage Feedback Bug(Ladder diagrams to show how devices are to be physically wired in the field.) 2007 ASHRAE Hong Kong ChapterSlide 64
Correction forVoltage Feedback 2007 ASHRAE Hong Kong ChapterSlide 65
Ladder Diagram 2007 ASHRAE Hong Kong ChapterSlide 66
Introduction to HVAC Control Systems 2. Basic of Electricity 3. Control Valves and Dampers 4. Sensors and Auxiliary Devices 5. Control Diagrams and Sequences 6. Self-Powered Controls 7. Electric Controls 8. Pneumatic Controls 9. Analog Electronic Controls 10. Digital Controls (*
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