by Greg Jourdan Wenatchee Valley College Las Vegas, Nevada March 15-16th, 2010 2:30-4 PM
DDC Controls and Software for the HVAC Lab Agenda
1. Types and Level of Automation 2. HVAC DDC Control Principles 3. Open Protocol Control Principles 4. DDC Architecture 5. Examples of DDC Software Programs 6. Typical DDC Control Systems and Applications 7. Present and Future Trends in DDC Controls 8. Getting DDC Equipment in your Schools
DDC Controls Quiz 1. T F
DDC and PLC’s are basically the same control devices.
2. T F
There are 3 key components of any DDC controls system.
3. T F
BACNet, Lon, and Tridium are Open Software DDC Integration Tools
4. T F
The thermistor is linear like the RTD.
5. T F
The Boolean Point is used for converting temperature sensors into useful information.
The Various Levels of DDC and Automation • Residential and Home Automation – Smart Homes, not widely adopted with HVAC Manufacturer’s Equipment – Smart HVAC Systems, ie. Carrier, Nordyn
• Commercial – DDC is Designed for Commercial Buildings – Multiple Vendors
• Industrial – PLC’s, SCADA, Ladder Logic, Costly $$$
Residential and Home Automation
Commercial DDC Automation
Present DDC Control Vendors and Merger Corporations
Schneider
Industrial Automation
Evolution of Controls and DDC
PC Based DDC Control System
Trunk / Network Cable
Field
Field
Field
Panel
Panel
Panel
1
2
3
LAN Devices
LAN Devices
Modern DDC Building Controls Utilize a Four Level Architecture
Sensor Level
Field Controller Level
Integration Level
Management Level
The Purpose of any Temperature Control System • Control systems are the “brains” of HVAC equipment to maintain human comfort. Pictured below is an AHU that serves only one zone. This type of AHU is called a single zone AHU. In the example, a temperature sensor (stat) sends a signal to a control panel, which sends a signal to a valve.
Three (3) Key Components of any Control System Include:
DDC Terminology Set Point and Offset Set point is the desired condition of a variable that is to be maintained, such as temperature. In the example below, 75 degrees F. is the room temperature set point. Offset is the amount of difference between control point and set point in a proportional control system. In the example below, the offset is approximately 4°F.
DDC Terminology Control Point • The Control Point is the actual temperature being sensed. The Control Point (temperature) may not be on the set point, but instead may be above or below it. Simply stated, set point is what you want, while control point is what you get.
• System Throttling Range (STR) is the change in the measured variable (i.e. temperature) that causes the controlled device to travel from one end of its stroke to the other.
The DDC Control Cycle and Control Action Can be Very Accurate •Two Position •Floating Action •Proportional Action •PI •PID
Control Cycle Graph
Two Position (Old School-Not Accurate)
Two Position control action chart (heating action shown)
Floating Action Control
Floating Control Action
Proportional Action
Proportional Control Action
Proportional with Integral Control (PI)
Proportional Plus Integral (PI) Control Action
PID-Proportional Plus Integral & Derivative
Proportional Plus Integral Plus Derivative (PID) control action
Control Points for the DDC System Four Types of Point Data Categories
• Boolean - Represents a binary value with only two states, such as "Off" or "On."
• Numeric - Represents an analog value such as a temperature, level, rate or similar floating point number, or a varying count (integer).
• Enum - Represents an enumerated state (more than two), such as a multi-speed fan with states "Off," "Slow," and "Fast." Enums are often called multi-states or discretes.
• String - A string of one or more ASCII characters and often (if alpha-numeric) with some literal meaning.
Control Points for the DDC Eight Types of Control Points Boolean
Numeric
Enumerated
String
BooleanPoint
NumericPoint
EnumPoint
StringPoint
A read only point
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•
Facets Proxy Extension Out
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Facets Proxy Extension Out
A read only point
•
Facets Proxy Extension Out
A read only point Facets Proxy Extension Out
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BooleanWritable •
A read only point
Extended to include Priority controls Fallback property Override expiration 7 Commands On & Off timers
NumericWritable •
Extended to include
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Priority controls Fallback property Override expiration 5 Commands
EnumWritable •
Extended to include Priority controls Fallback property Override expiration 5 Commands
StringWritable •
Extended to include Priority controls Fallback property Override expiration 5 Commands
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Sensors • A sensor monitors and measures a variable. The HVAC variables are temperature, humidity, flow, and pressure. Different types of signals are produced by different types of sensors. They include:
– Electric Sensors – Pneumatic Sensors – Electronic Sensors Examples of a sensor is shown here. While it may appear to be a thermostat, it is a remote sensor with a remote set point dial. The controller is in another location.
Electronic Sensors Include: • Resistance sensors are Resistance Temperature Devices (RTDs), and are used in measuring temperature.
• Voltage sensors could be used for temperature, humidity and pressure.
• Current sensors could be used for temperature, humidity, and pressure. The typical current range is 4 to 20 mA (milliamps).
Temperatures Sensors Can be either Thermocouple, RTD, or Thermistor. This Chart Compares the Advantages and Disadvantages.
Modern HVAC DDC Sensors Include • Humidity and Temperature Transmitters • CO2 for Indoor Air Quality (IAQ) Utilizing Demand Ventilation • Power Meters • Branch Circuit Monitors • Energy Meters
Controllers Can Include: Electric Controls
Pneumatic Controls
DDC Controls Electronic Controls
Controllers Principles The Controller Receives the Input and Processes an Output
The DDC Controller Has 3 Functions 1. Receives the Input From the Sensor 2. Performs a Logic Function 3. Processes an Output
Basic DDC-Electronic Control System
Direct Digital Control System DAMPER
DUCT
ELECTRIC MOTOR
DIGITAL COMPUTER
ELECTRIC
With INTERFACE
OPERATOR
HARDWARE VALVE
SPACE
PNEUMATIC OPERATOR
DISCHARGE SENSORS
E-P TRANSDUCER
FINAL CONTROL
VALVE
Controlled Devices Dampers and Valves
Automatic Control Typical Multiblade Dampers
Typical Typical Single Single - and Double-Seated Two-Way Valves
Typical Three-Way Mixing and Diverting Valves
Controlled Devices 2-Way & 3-Way Control Valves
DDC Control Systems Use Control Valves That Are •Fully Electronic •3-Way Control Valves •Not commonly used •2-Way Control Valves •Used with DP sensors and VSD pump systems •Pressure Independent Characterized Control Valves™ (PICCV) •No Cv required, reduced pumping costs, higher efficiency, easy to balance
Direct Connect Actuator
Damper Connected to Actuator Via Shaft and Coupling
Damper Actuators are Controlled by Either a Voltage (2-10vdc) or Current (4-20ma) Signal from the Controller
Courtesy Belimo
Electronic ASDs, VFD’s
Adjustable Speed Drives •Vary Frequency of Motor •Often Called VSDs or VFDs •Used with Any Variable Motor Speed Control Application
Adjustable Speed Drives Turn AC to DC and Back to AC (Pulsed PWM)
Variable Frequency Drives (VFD’s) are Becoming Standard Equipment On:
• Towers • VAV Fans • Pumps • Chillers
Example of DDC Controls
Example of DDC Control Heating Coil Control With Reset
Example of DDC Control Converter Control With Reset
Variable Speed Pumps are Used in HVAC Projects for Energy Conservation The Westin Building:Building Hydronic System VSD’s match calculated Demand to
Cooling Tower tonnage
VSD Drives on Fans to Maintain Static Pressure for Energy Conservation
Many Factory Built-Up AHU’s Are VAV with DDC Controls
http://www.mmtmagazine.org/page/indexa916.html?id=44
Modern Control Systems Tie All Building Systems Together Via a Standardized Networks (TCP/IP, BACnet, LON)
HVAC
Life Safety Systems
Lighting
Security
Chillers
Boilers
Building Switchgear
DDC Software is Integrated into the Building Systems Current automation systems allow communications with multiple vendors
■ Fire alarm, security ■ Lighting, fan units ■ PLCs (Programmable Logic Controllers)
■ Boilers and chillers
BACnet Software Standard Protocol •BACnet, Developed by ASHRAE •True, Non-proprietary, Open Protocol (Industry Standardized)
•Multiple Vendor Controllers
BACnet Connectivity
LonWorks Platform (Open Protocol)
LonTalk and the Neuron Chip
BACnet is the Preferred and Fastest Growing Network Standard Revenue (mill $)
Units (1000s) BACnet
Lon
Pro-
BACnet
Lon
prietary
Proprietary
1998
145
44
588
110
43
604
2001
183
58
717
231
61
684
2008
747
90
947
648
78
821
* Units sold and revenue for BACnet, LonWorks, and proprietary systems in the building automation industry, 1998-2008
DDC Networks Have Lot of Connections And Don’t Always Communicate between the Various Vendors Application A
Application B
Application C
Niagara Normalizes All Systems BACNet or LON Network Application A
Application B
Application C
DDC Control Systems – Schematics are done on AutoCAD •Drawings are sent via email •As Built Modifications are easy to change
Example of DDC AutoCAD Boiler Controls
Typical DDC AutoCAD-Example Schematic
Actuator
Sensors
Controller
Typical DDC Software Controls on Factory AHU’s Economizer Example Sensors
Controller
Actuator
Sensors
Controller
Actuator
Typical Controls on Factory AHU’s Example of Program for Siemens Controls
Typical Controls on Factory AHU’s- Example of Program for Siemens Controls
Typical DDC Controls AHU’s-Example of Automated Logix Graphics Display
Present and Future DDC Systems Are Using
Smart Card Access
• Employee ID Card • Physical Access Badge • Remote Access Token • Combines function into a single smart card on a USB stick
Present and Future Control Systems are Using • PDA’s by the building operators are used as diagnostic and maintenance tools.
Present and Future Control Systems Will Be Able to Do Anything Money Will Buy Including: • Using Cloud Height Ceilometers
• Owners can know the weather without going outside. Performance and reliability in all weather conditions up to 25,000 feet
• GPS Tracking Systems on each individual in the Building
Present and Future Controls are Using Wireless Mesh Networks
Wireless Networks Include: Wibree Bluetooth ZigBee
Present and Future Controls are Using Wireless Power Meters
Present and Future DDC Controls are Smart at the Field Level
Talking Thermostats
Telephone Thermostats
Smart Air Velocity Sensors
Present and Future DDC Controls are Smart and on the Internet WEB
Present and Future DDC Building Control Systems Will
Control Individual Lighting Monitor Each Tenants Total KwH Power Control RH and CO2 Provide Customers Options to Control Individual Space or Cubicle Areas via the Web
Present and Future DDC Control Systems Can Use Door Lock ID tags to always tell management where you are in the building. Radio frequency ID systems which allow you to track building inventory and manage information with reliability, even in harsh industrial environments . •
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DDC Challenges and Obstacles for HVAC Instructors and Students • DDC Building Systems are becoming more complex. • Information Tech (IT) Departments need to be involved in maintenance of building controls
• Future trends and demands for skilled labor is creating shortages (not enough people entering blue collar trades)
DDC HVAC Controls Changes and Challenges
Building Controls are Evolving to become: Totally Integrated Modern Sensors and Instrumentation Devices will be Adopted Maintaining Building Efficiencies and Comfort at Minimum Costs will be more complex. Challenges and Obstacles will be a continued shortage of skilled labor.
Getting Started with DDC at your HVAC School • Network with Industry • Work as Summer Interns • Develop or Buy Updated Curriculum
Getting Started with DDC at your HVAC School • Get the DDC Equipment • Donated is Ok, New is Better • Start Writing Grants
Answers to DDC Controls Quiz 1. 6. TT FF 2. 7. TT FF 3. T F 8. T F 4. T F 5. 9. TT FF 10.T F
DDC and PLC’s are the HVAC Systems costbasically over 35% ofsame
control thedevices. energy in the typical building. There are 3 keyCFM components of any The minimum requirements for a DDC controls system. home is based on the number of people. BACNet, Lon, and Tridium are Open According to EPA and WHO, Americans Software DDC Integration Tools spend approximately 90% of their time The thermistor is indoors. linear like the RTD. The Point is above used for converting HighBoolean return air CO2 1000 ppm is temperature sensors an indication of into IAQuseful problems. information. Vents, chimneys, flues must be at least
10’ from outside air intakes.
