Introduction to Building Automation Systems (BAS)

Transcription

1 Introduction to Building Automation Systems (BAS) Ryan R. Hoger, LEED AP Building Automation Systems Centralized controls Change scheduling for multiple HVAC units at same time Monitor health of equipment Internet accessible Alarming via text msg or Collect/trend data Integrate to lighting control or security system 1

2 DDC - Direct Digital Control of an HVAC system A method of monitoring and controlling HVAC system performance by collecting, processing, and sending information using sensors, actuators, and microprocessors. What is DDC? DDC is the concept or theory of HVAC system control that uses digital controls Physically, DDC encompasses all the devices used to implement this control method: a whole group of DDC controllers/microprocessors, actuators, sensors, and other devices. What is DDC? 2

3 DDC - the Control Theory input-process-output cycle A point is ANY input or output device used to control the overall or specific performance of equipment or output devices related to the equipment. What Is a Point? 3

4 AI Analog input -a sensor that monitors physical data, such as temperature, flow, or pressure. DI Discrete input -a sensor that monitors status. Momentary and maintained switches, ON-OFF equipment status, and digital pulses from flow and electric power meters are discrete inputs. AO Analog output - a physical action of a proportional device in the controlled equipment - e.g., actuator opens air damper from 20% to 40%, other dampers, valves, inlet guide vanes, etc. DO Discrete output - changes or maintains device status. Performs momentary or maintained switching for start/stop of pumps, fans, two-position dampers, and on/off control. Four Kinds of Points Input sensors and status devices react to changes in conditions. Conditions include internal load, outside air temperature, and output actions. Output devices act based on sensor and status device reactions. Ex. 1: Open cooling coil valve (output action). Supply air temperature sensor SAT detects (input reaction) decrease in temperature. Ex. 2: Filters on an air handler get dirty (conditions). Air switch reacts by closing contact for filter dirty alarm. DDC: Actions and Reactions 4

5 Control Point Identification Exercise AI Temperature Thermistors Resistance Temp. Detectors (RTDs) Transmitters Pressure Humidity Flow (CFM, GPM) Voltage Current CO2 DI Switch dry contact (open or closed) Airflow Water Differential pressure High/low limit switch (alarm or normal) Freeze alarm Smoke detectors Wattmeter pulses (pulse initiator or counter) Sensor and Status Devices used as Input Points (Reactions) 5

6 AO Damper actuators DO Solenoid valves Modulating valves Relays / VFD contactors Alarm signal Devices used as Output Points (Actions) Closed Loop Control is accomplished by the control signal being sent to the controlled device with constant feedback from the sensor/status device providing input to the controller. DDC: Closed Loop Control 6

7 Closed loop control is determined by: Control algorithms Configuration values Time schedule data Setpoint schedule data Closed Loop Control Heating/cooling coil control Humidification/dehumidification Mixed air damper optimization VAV fan control VAV supply & return fan tracking Indoor air quality Generic PID control Control point reset Typical Control Algorithms 7

8 Time of day scheduling Discrete device controlled as analog Discrete interlock Discrete staging Proportional thermostat Primary/secondary pump control Night free cooling Adaptable start/stop Permissive interlock Typical Control Algorithms (cont d) P Proportional PI Proportional-Integral PID Proportional-Integral-Derivative Algorithm Type Used by Processor Determines Control Strategy 8

9 PID = Proportional-Integral-Derivative Control What it is: This type of control algorithm is based on value/amount (proportion), rate of change (integral), and error allowances (derivative). PID control calculates and sends commands for outputs based on all three types of information. Advantages: More precise than P and PI controls, PID wastes less energy based on more frequent feedback and quicker responses. What Is PID Control? What it is: Control algorithm based only on value/amount (proportion). Disadvantages: Less precise than PID and PI control; cannot respond to error margins or time. Uses the most energy due to over- and under- outputs. Proportional Control (P) 9

10 What it is: Control algorithm based on value/amount (proportion), rate of change (integral). PID uses error allowances (derivative) as well. Advantages: More precise control and less energy used than proportional (P); minimum swings from setpoints. Proportional-Integral Control (PI) & (PID) Exercise 1: Building Direct Digital Control on a CV Air Handler 10

11 Exercise 1: Base CV Air Handler Unit -No Controls Exercise 1: AHU - DDC Control of Start / Stop Scheduling 11

12 Exercise 1: AHU - Add DDC Damper Exercise 1: AHU - Add DDC Cooling Coil Control 12

13 Exercise 1: AHU - Add DDC Outside Air reset and Enthalpy Control 13

14 Control Point Summary for Base CV AHU Exercise 2: Building Direct Digital Control on a VAV Air Handler 14

15 History VAV systems came into favor for mid and large size facilities in the 1960s and 1970s Save energy Improve comfort Take advantage of building diversity Cooling needed year round for true interior core zones Sequence Main AHU provides morning warm-up heat until RAT setpoint is satisfied all zones at 100% design airflow AHU switches to 55 F discharge air controlled cooling zones modulate CFM to controls space temp No AHU heat remainder of day individual zone reheat or baseboard as needed Zoning Systems 15

16 Single Zone Systems Heating/Cooling Unit ROOF Heating/Cooling Unit Heating/Cooling Unit Heating/Cooling Unit TMT TM TMZC TM ZONE 1 ZONE 2 ZONE 3 ZONE 4 Multiple Zone Systems 16

17 To Build DDC on a VAV AHU, Start with DDC on a CV AHU... Exercise 2: Create a VAV AHU with Inlet Guide * If using VFD, use two Variable Frequency Drives instead, but you will still need the same control points and HPS shown. 17

18 Filter Status (FLTS) FreezeStat (FRZ) Smoke Detector (SMK) Typical DDC Items You Can Add as Optional Items: Exercise 2: VAV AHU with DDC Filter Status 18

19 Exercise 2: VAV AHU with DDC FreezeStat Exercise 2: VAV AHU with DDC Smoke Detector 19

20 Control Point Summary for Base VAV AHU DDC Controllers Programmable controllers Application Specific controllers Factory integrated controllers 20

21 Types of Direct Digital Control Networks Interface - devices and software that work as a translator between a DDC system and the humans who operate it. An interface is the operator s window into a building s operating systems and conditions. Interfaces to DDC 21

22 User interfaces: Allow more efficient system operation monitoring. You can look at what s happening on all floors from the tenth floor if DDC network is peer-to-peer. Allow immediate diagnosis of HVAC units and controls, including changes, without physically being in front of the unit. Can provide reports (e.g., historical, consumable, run times, system activity) to be used as records of building operations. Can provide graphical representations of the controlled system. User Interface Benefits User Interface Types 22

23 Hand-held Connected to a DDC Controller Interface Examples PC Connected to a DDC Network Interface Examples 23

24 Web Server Connected to DDC Network Interface Examples Web Interfaces Standard web browser or WAP access View system status Access schedules and setpoints Trending, alarming, reporting Real time interactive graphics 24

25 FLOOR PLAN GRAPHICS EQUIPMENT GRAPHICS 25

26 EQUIPMENT GRAPHICS FLEXIBLE SCHEDULING 26

27 TRENDING Internet Thermostats Low cost alternative to BAS Direct to Ethernet No PC software uses standard web browser No access fees Text/ alerts 27

28 Internet Thermostats Internet Thermostats 28

29 Phone Apps for Thermostats Integration Information Transfer Add new HVAC equipment to an existing Building Management System Common User Interface Building Integration Lighting, HVAC, Security, Fire & Life Safety Enterprise Integration-Utilities, Financial 29

30 Building Management Systems HVAC Lighting Security Power Metering Common Protocols PT PT MODBUS PT 30

31 Integration Interoperability is the ability of different devices from the same or different manufacturers to function accurately together. Standard protocol - a set of guidelines for commands, inputs, and output encoding to create a universal language for all DDC devices. When the same standard protocol is used in DDC devices, interoperability is possible. Gateways - devices added to DDC networks to make standard protocols available and interoperability possible. Interoperability BACnet Standard protocol requirements for Building Automation and Control networking, created by ASHRAE to ensure interoperability. BACnet uses software and a LAN interface to DDC to provide: Representation of all manufacturer devices internal functioning in a common, network-visible way. A common command set for device services. Common encoding of commands, understandable by all devices and interfaces adhering to the protocol. 31

32 Enterprise Security Systems Energy Lighting CFO MODBUS XML SQL HTTP HTML Fire Systems LEGACY Open System Framework ODBC SNMP JDBC FTP Facility Management SMTP WAP Maintenance HVAC Systems And More Typical Questions Q: What part of the control system is done by the HVAC designer? What is done by the installing contractor? Do most HVAC engineers actually do control system work or is that done by specialty contractors? A: Depends on the project A good designer lays out the control system as an integral part of the mechanical system, including: Sequence of operation Front-end/user interface details The details of hardware, software, and cabling should be left to the contractor since every manufacturer s system is different Unfortunately, most designers rely on manufacturers to write project specs, or worse, contractors to design in the field as they install 32

33 Typical Questions Q: How does one select the type, number, and position of sensors? (i.e. measure temp in a room or in the supply duct? Where in the room or duct do the sensors go? How many go in each room?) A: Depends on the project Best to measure what you want to control usually space temp Mount between 4 and 5 ft high, out of direct sunlight, and in the return air path One sensor per controllable piece of equipment is best usually one per room Many exceptions for specialty systems and/or install cost compromises Typical Questions Q: How does one go about determining the coefficients of a P, PI, or PID controller and tune the system once it has been installed? A: Practice and Patience Zero out the derivative term HVAC equipment and building systems react too slowly for it to matter Tune the proportional term first, then worry about integral term Make small changes and monitor Use a dynamic graph 33

34 Typical Questions Q: Where can one go to get more information and training? A: Iowa Energy Center / Iowa State University ASHRAE Learning Institute Continental Automated Buildings Association BACnet - Case Study Conrad Hotel 352 HVAC units 311 guestrooms Added DDC controls Occupancy sensors Entrance door & motion 34

35 Energy Savings Estimation Tools Utility Rebates for Controls Programmable Thermostat Nicor Gas or NIPSCO Gas $50 Peoples Gas or North Shore Gas $80 Wisconsin Focus on Energy $100 per RTU Economizer Controls ComEd $40 per ton Wisconsin Focus on Energy $250 per RTU CO2-based DCV ComEd $0.03 per ft2 DCEO $0.28 to 0.40 per ft2 Peoples Gas or North Shore Gas double custom NIPSCO Gas $0.15 per ft2 Wisconsin Focus on Energy $0.05/CFM supply Wisconsin Focus on Energy $350 per RTU 35

36 Utility Rebates for Controls Boiler Reset Control Nicor Gas $0.50 per MBH Peoples Gas or North Shore Gas $500 NIPSCO Gas $0.35 per MBH Wisconsin Focus on Energy $75/controller DDC Controls ComEd $0.20 per ft2 DCEO $0.20 to 0.40 per ft2 Variable Frequency Drives (VFDs) ComEd $60 per Hp DCEO $92 per Hp NIPSCO Electric - $40 per Hp Wisconsin Focus on Energy $50 per Hp Utility Rebates for Controls Hotel Guest Room Energy Mgmt System ComEd $25 to 65 per unit Kitchen Exhaust Demand Control Ventilation ComEd $350 per Hp Custom Incentives (based on annual savings) ComEd $0.06 to 0.07 per kwh Nicor Gas $0.75 to 1.00 per therm Peoples Gas or North Shore Gas $1.00 per therm DCEO $0.12/kWh and $3.00/therm NIPSCO $0.09/kWh and $0.60/therm 36

37 Thanks for Coming! and Special Thanks to those who allowed me to use their graphics Ryan R. Hoger, LEED AP