Chapter 13 Building Automation Systems for IAQ Buildin

1
Chapter 13

• Building Automation Systems for IAQ

Building Automation Systems and Controllers
Operator Interface Methods Building Automation
System Input and Output Components Direct
Digital Control Strategies, Features, and
Algorithms IAQ Strategies and Energy
Considerations
2
Chapter 13

• Building Automation Systems for IAQ

Building Automation Systems and Controllers
Operator Interface Methods Building Automation
System Input and Output Components Direct
Digital Control Strategies, Features, and
Algorithms IAQ Strategies and Energy
Considerations
3

• Distributed direct digital control systems have
  multiple CPUs at the controller level.

4

• Application-specific controllers are designed to
  control only one type or part of an HVAC system.

5

• Unitary controllers are designed for simple zone
  control using a standard wall-mounted temperature
  sensor.

6

• Air-handling unit controllers are used when the
  sophisticated control of large central-station
  air-handling units is required.

7

• Variable-air-volume (VAV) air terminal unit
  controllers are similar in appearance to unitary
  controllers. The difference is in the factory
  programming of the erasable programmable
  read-only memory (EPROM) chip.

8

• Variable-air-volume (VAV) air-handling unit
  controllers are used to control VAV air-handling
  units in order to maintain a minimum static
  pressure in supply ducts.

9

• Variable-air-volume (VAV) air-handling
  controllers are used to control building space
  temperature and air volume in VAV air-handling
  systems.

10

• Network communication modules coordinate
  communication from controller to controller on a
  network and provide a location for operator
  interface.

11

• Desktop personal computers (PCs), alarm printers,
  notebook PCs, portable operator terminals, keypad
  displays, and dumb terminals are used in large
  buildings to access and troubleshoot a buildings
  automation system.

12

• A building automation system with web browser
  software packages allows a stationary engineer to
  communicate and change settings from anywhere in
  the world.

13

• Analog input devices send 4 mA to 20 mA or 0 V to
  10 or 20 V signals to a building automation
  systems controllers, causing a proportional
  electrical signal change to output components.

14

• Temperature sensors are available in a variety of
  packages and mounting configurations including
  wall-mounted, duct-mounted, immersion
  (well-mounted), and averaging.

15

• Humidity sensors contain a hygroscopic element
  that changes physical characteristics as the
  humidity changes.

16

• Piezoelectric elements (pressure-sensitive
  crystals) are used in duct pressure-sensing
  applications, while bellows elements are used in
  many piping applications.

17

• In IAQ applications, differential pressure
  sensors or pitot tubes and temperature sensors in
  a duct can act as airflow measuring stations
  (AMS).

18

• A digital input device signal is a binary (ON or
  OFF) signal.

19

• Limit thermostats maintain a temperature above or
  below an adjustable setpoint.

20

• Humidistats are digital input devices used in
  ducts and indicate when a humidity setpoint has
  been reached.

21

• Differential pressure switches are often used to
  indicate a difference in pressure across a fan or
  pump or to indicate the condition of an
  air-handling unit filter.

22

• Electric/pneumatic transducers have an analog
  input signal, such as 4 mA to 20 mA, from the
  building automation system and an output air
  pressure signal of 0 psi to 20 psi.

23

• Triac-switched controller output terminals
  require an external power supply and are used to
  switch alternating current (AC).

24

• Relays are used to allow low-voltage-rated triacs
  of building automation system controllers to
  switch line-voltage components ON and OFF.

25

• In a direct digital control system, a building
  automation system controller is wired directly to
  controlled components.

26

• In closed-loop control, feedback occurs among the
  controller, sensor, and controlled component(s).

27

• In open-loop control, no feedback is provided
  from sensors to a building automation system
  controller.

28

• Setpoint is the desired value to be maintained by
  a system with the desired accuracy to the
  setpoint being programmed into a BAS controller.

29

• Setup and setback setpoints are values that are
  active during the unoccupied mode of a building
  automation system.

30

• Low-limit controls stop outside-air dampers from
  closing 100 and still allow ventilation air into
  a building when ventilation-air temperatures are
  excessively low outside.

31

• Proportional control algorithms position a
  controlled component in response to the amount of
  offset experienced in a building automation
  system.

32

• Derivative control algorithms determine the
  instantaneous rate of change of a controlled
  variable.

33

• Adaptive control algorithms are self-tuning
  algorithms that are often used to correct an
  overcycling control system.

34

• Acceptable indoor air quality numbers for
  ventilation are detailed in ANSI/ASHRAE Standard
  62.1-2007, Ventilation for Acceptable Indoor Air
  Quality.

35

• CO2 levels in building spaces or zones are used
  as an indicator of occupancy.

36

• A typical HVAC system increases ventilation when
  CO2 levels rise to 600 parts per million (PPM) so
  that levels do not exceed 1000 PPM.

37

• Economizers use outdoor air to provide free
  cooling and are not practical or advisable in
  hot-humid climates.

38

• In night precooling, cool outdoor night air is
  used to cool a building while simultaneously
  exhausting accumulated pollutants.