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First computer 87‐100 BC
Terminology
controlleddevice
controller
controlledvariable
sensor
controlledagent
airflow
Open Loop
valve
controller
outdoor-airsensor
chilledwater
airflow
Closed Loop
airflow
valve
chilledwater
controller
discharge-airtemperature sensor
Control Reset
controller
airflow
valve
chilledwater
outdoor-airsensor
discharge-airtemperature sensor
Control “Points”
• Binary input point (BIP)– Examples: fan status (on/off), dirty filter
• Binary output point (BOP)– Examples: start/stop fan or pump, open/close damper
• Analog input point (AIP)– Examples: temperature, pressure, airflow
• Analog output point (AOP)– Examples: control valve or damper position, temperature setpoint
Types of Control Action
• Two‐position (on/off)• Floating• Proportional• Proportional–Integral (PI)• Proportional–Integral–Derivative (PID)
Two‐Position (On/Off)co
ntroll
er ou
tput
time
B0°F
- 5°F
100%
0%
+ 5°F
contr
olled
-varia
blede
viatio
n differential
on
off
A
setpoint
setpoint
Floatingco
ntroll
er ou
tput
time
BA
0°F
- 5°F
100%
0%
+ 5°F
differential
C
D
open
stop
stop
close
switch differential
contr
olled
-varia
blede
viatio
n
Proportionalco
ntroll
er ou
tput
time
0°F
- 5°F
100%
0%
+ 5°Foffset
setpointA throttling
range
contr
olled
-varia
blede
viatio
n
Integralco
ntroll
er ou
tput
time
0°F
- 5°F
100%
0%
+ 5°F
setpoint
A
B
contr
olled
-varia
blede
viatio
n
Proportional–Integral (PI)co
ntroll
er ou
tput
time
0°F
- 5°F
100%
0%
+ 5°F
setpoint
proportionalintegral
PI
contr
olled
-varia
blede
viatio
n
Derivativeco
ntroll
er ou
tput
time
0°F
- 5°F
100%
0%
+ 5°F
setpointA
BC
contr
olled
-varia
blede
viatio
n
Proportional–Integral–Derivative (PID)
contr
oller
outpu
t
time
0°F
- 5°F
100%
0%
+ 5°F
setpoint
PI
derivative
PID
contr
olled
-varia
blede
viatio
n
Comparison of Control Actions
time
setpoint
PI
PID
P
offset
contr
olled
-varia
ble de
viatio
n
overshoot
Controller Technologies
• Pneumatic• Analog‐electric• Microprocessor‐based
Pneumatic Control System
storagetank
compressorairdrier air
filter
pressure-reducing valve
main line
branch line
controller
controlleddevice
drain
Pneumatic Controller
orificemainline
branchline
flappersetscrew
bimetal element
nozzle
Pneumatic Controlled Device
actuatorchamber
branch linevalvestem
diaphragmspring
plug
valve seat
Analog‐Electric Controller
Electronic Controlled Device
actuator
valvestem
plug
valve seat
Microprocessor‐Based Controller
DDC Controlled Device
Comparison of Technologies
Pneumatic• No communication
capabilities• Expensive and complicated to
provide complex control strategies
• Inherently proportional• Extensive maintenance
requirements
Microprocessor‐based• Allows system‐wide
communication• Fewer hardware components• Easily accommodates complex
control strategies• Provides many types of
control action• Fewer maintenance
requirements
period twoAutomatic Control of HVAC Systems
HVAC System Control
Air Conditioning Clinic TRG-TRC017-ENAir Conditioning Clinic TRG-TRC017-EN© American Standard Inc. 2002
Control of an HVAC System
unit-level control
system-levelcontrol
buildingmanagement
Benefits of Unit‐Level Control
unit-level control
• Stand‐alone control• Safeties, alarms, and diagnostics• Installed, tested, and commissioned in factory
Unit‐Level Control
VAV air handler
Discharge‐Temperature Control Loop
valve
discharge-airtemperature sensor
controller
VAV air handler
Ventilation Control Loop
outdoor-airdamper
return-air damper
controller
VAV air handler
Economizer Control Loop
outdoor-airtemperature sensor controller
VAV air handler
Mixed‐Air‐Temperature Control Loop
mixed-air temperature sensor
controller
VAV air handler
Static‐Pressure Control Loop
duct static-pressure sensorsupply fan
controller
VAV air handler
Building‐Pressure Control Loop
controller
indoor-pressure
sensor
relief fan
outdoor-pressuresensor
VAV air handler
Pneumatic Controls
main line controllers
Equipment Protection
unit-levelcontroller
air-cooledwater chiller
System‐Level Control
unit-level control
system-levelcontrol
Chilled‐Water VAV System
system-levelcontroller
pumps exhaust fan
boiler
water-cooledchiller
coolingtower
VAV airhandler
VAV terminalunits
System‐Level Operating Modes
Occupied Mode• Terminal units maintain
“occupied” setpoints• Outdoor‐air damper delivers
proper amount of ventilation air
• Air is cooled or heated to desired setpoint
• Supply fan operates continuously, modulating to maintain system static‐pressure setpoint
Unoccupied Mode• Terminal units maintain
“unoccupied” setpoints• Outdoor‐air damper is closed• Supply fan, cooling coil, and
heating coil operate only as needed
Rooftop VAV System
system-levelcontroller
VAV terminalunitspackaged rooftop
air conditioner
occupied hours
Morning Warm‐Up
6 AM Noon 6 PM
occupiedsetpoint
unoccupiedsetpoint
zonetemperature
system on system off
Air‐Cooled Chiller, Fan‐Coil System
system-levelcontroller
air-cooledchiller
fan-coilunits
dedicatedoutdoor-air unit
boilerpumps
Two‐Pipe Changeover Requirements
outdoor dry-bulb temperature
hot water
chilled water0°F
(-18°C)20°F
(-7°C)40°F(4°C)
60°F(16°C)
80°F(27°C)
40°F(4°C)
80°F(27°C)
120°F(49°C)
140°F(60°C)
supp
ly-wa
ter te
mper
ature
30°F(17°C)
15°F (8°C)
deadband
Water‐Source Heat‐Pump System
system-level controller
dedicatedoutdoor-air unit
water-sourceheat pumpsboiler
pumps
coolingtower
exhaust fan
Loop Temperature Control
cooling toweroff
boiler off
heat pumps inheating modeheat pumps in
cooling mode
pumps on
System Optimization
unit-level control
system-levelcontrol
VAV system
Fan‐Pressure Optimization
damper positions
system-level controller
fan speed orinlet-vane
position VAVterminal units
supplyfan
static-pressure sensor
rooftop VAV system
Optimum Start
occupied hours
6 AM Noon 6 PM
occupiedsetpoint
unoccupiedsetpoint
zonetemperature
time clock
optimum start
air‐cooled chiller, fan‐coil system
Chilled‐Water Reset
constant-volumepump coil
air-cooledchiller
system-levelcontroller
54°F(12.2°C)
47°F(8.3°C)
valveposition
leaving-watertemperature
water‐source heat‐pump system
Optimized Loop Controlco
mbine
d ene
rgy u
se, k
W
cooling towercooling tower
100100
heatpumpsheatpumps
loop water-temperature setpointloop water-temperature setpoint
90°F(32°C)90°F(32°C)
optimizedcontroloptimizedcontrol
8080
6060
9090
7070
5050
failure recovery
Sequences of Operation
chiller-plantcontroller
failure recovery
Stand‐Alone Operationheat pump withunit-level controller
thermostat
system-levelcontroller
failure recovery
Selection of Controlled Devices• Normally‐closed actuator• Normally‐open actuator• Position‐maintained actuator
period threeBuilding Automation Systems
HVAC System Control
Air Conditioning Clinic TRG-TRC017-ENAir Conditioning Clinic TRG-TRC017-EN© American Standard Inc. 2002
Building Management
unit-level control
system-levelcontrol
buildingmanagement
Responding to Comfort Complaints
Graphical User Interface
Time‐of‐Day Scheduling
Centralized Alarms and Diagnostics
Remote Access
• Alarm notification• Dial‐in access
Reports
• Trend logs• Alarm activity• Building energy use
• After‐hours tenant occupancy
• Equipment diagnostics and
f
Preventive Maintenance
Integration with Other Systems
return-airdamper
normal HVAC operation smoke-control operation
smoke-control
dampers
Connecting Multiple Sites
• Centralized monitoring
• Diagnose or predict problems with systems
• Combine energy usage for negotiating energy contracts
period fourInteroperability
HVAC System Control
Air Conditioning Clinic TRG-TRC017-ENAir Conditioning Clinic TRG-TRC017-EN© American Standard Inc. 2002
Network
server
nodenode
node
node
Dedicated Versus Shared Networks
• Dedicated network– Easier to design and install– More expensive
• Shared network– Less expensive (shares infrastructure)– More difficult to ensure security
LAN Versus WAN
routerrouter
building A building B
Intranet Versus Internet
routerrouter
building A building B
Internet
firewall
“Tiered” BAS Architecture
HVAC system
controllerlighting system
controller
fire-protectionsystem
controller
securitysystemcontroller
PC workstation
LAN forunit controllers
LAN forsystem controllers
equipment with unit controllers
Communications Protocols
• Proprietary– Used, produced, or marketed under exclusive legal right of an individual or organization
• Open– Available to public domain and is shared among vendors
• Standard– Open protocol that has been formalized by a governing body
Gateways
gateways
HVAC lightingfireprotection security
proprietary protocol LAN
proprietary protocol LAN
gateways
PC workstation
System‐Level Interoperability
HVAC lightingfireprotection security
proprietary protocol LAN
open, standard protocol LAN
PC workstation
gateways
Unit‐Level Interoperability
HVAC lightingfireprotection security
open, standard protocol LAN
proprietary protocol LAN
gateways
PC workstation
Interchangeability
• Plug‐and‐play
• Standard object types– Analog input– Analog output– Analog value – Multi‐state input– Multi‐state output – Device– Event enrollment– Notification class – Trend– Group
Binary input Binary output Binary value Loop Command File Calendar Schedule Program
LonTalk
• LonMark functional profiles– Boiler controller– Chilled ceiling controller– Chiller– CO2 sensor– Damper actuator– Discharge‐air controller– Fan‐coil controller– Heat pump– Lighting‐panel controller– Occupancy sensor– Pressure sensor
Rooftop unit controller
Space-comfort controller
Temperature sensor
Thermostat Unit-ventilator
controller Variable-speed
motor drive VAV controller
“Tiered” BAS Architecture
HVAC lightingfireprotection security
PC workstation
LonTalk protocol
BACnet protocol
“Flat” BAS Architecture
open, standard protocol LAN
PC workstationPC workstation
period fiveReview
HVAC System Control
Air Conditioning Clinic TRG-TRC017-ENAir Conditioning Clinic TRG-TRC017-EN© American Standard Inc. 2002
Review—Period One
controlleddevice
controller
controlledvariable
sensor
controlledagent
airflow
Review—Period Two
unit-level control
system-levelcontrol
buildingmanagement
Review—Period Three
• Building automation system functions– Respond to comfort complaints
– Centralize scheduling
– Receive alarms and diagnostics
– Provide remote
Review—Period Four
HVAC lightingfireprotection security
PC workstation
LAN forunit controllers
LAN forsystem controllers