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AT E M M O D U L E 3 : C O N T R O L SA c c r e d i t e d T e x a s E n e r g y M a n a g e r
System Types
❯Manual
❯Programmable thermostats
❯Mechanical time clocks
❯Electronic time clocks
❯Pneumatic controls
❯Networked thermostats
❯Direct digital control (DDC)
A c c r e d i t e d T e x a s E n e r g y M a n a g e r
Pneumatic Control Systems
A c c r e d i t e d T e x a s E n e r g y M a n a g e r
❯Air compressor
❯Piping & tubing
❯Sensors
❯Actuators
DDC System Components
❯Desktop or laptop computer
-Operator workstation
-Programming
-Network interface
❯Controllers – executes control
logic based on inputs
-Building
-Local
❯Communications interfaces
❯Sensors
❯Data
-Analog – variable
-Digital – 0 or 1/on-off/open-closed
❯Network cabling
A c c r e d i t e d T e x a s E n e r g y M a n a g e r
e n e r g y m a n a g e m e n t p r o g r a m : f u n d a m e n t a l s a n d d e v e l o p m e n t
DDC System Architecture
BC
CC C
Internet
e n e r g y m a n a g e m e n t p r o g r a m : f u n d a m e n t a l s a n d d e v e l o p m e n t
DDC Inputs & Outputs
Controller
Co
ntr
ol O
utp
utsSen
sor In
pu
ts
Valve open/closeDamper open/closeMotor off/onIndicator lightAlarm
TemperaturePressure
FlowHumidity
Motor statusSwitch position
DDC System Functions
❯Scheduling
-Normal work days
-Events
-Weekends
-Holidays
❯Control strategies
-Optimum start & stop
-Demand limiting
-Temperature resets
❯Monitoring
❯Logging & trending
❯Diagnostics & troubleshooting
❯Alarming
A c c r e d i t e d T e x a s E n e r g y M a n a g e r
DDC Protocols
❯BACNet
-Open protocol
-Developed by ASHRAE
-Specifically for building equipment
control
❯LONTalk
-Proprietary protocol
-Developed by Echelon Corp.
-Special micro-compressor chip
required for communication
❯Tridium (Niagra)
-Proprietary built on open
standards
-Allows integration of diverse
systems
A c c r e d i t e d T e x a s E n e r g y M a n a g e r
Demand Control Ventilation
❯Utilize in area w/ high occupancy levels
❯Uses CO2 levels to estimate occupancy
❯Controls outside air flow w/ modulating dampers
-Closed at zero occupancy (low CO2 level)
-Full open at maximum occupancy (high CO2 level)
A c c r e d i t e d T e x a s E n e r g y M a n a g e r
Utilizing Economizers
❯Supplies 100% outside air for cooling
❯Compressors do not operate
❯Takes advantage of mild outdoor
conditions
❯Control types
-Dry bulb
› Less humid climates
› Temperature only
-Enthalpy
› More humid climates
› Temperature & humidity
A c c r e d i t e d T e x a s E n e r g y M a n a g e r
e n e r g y m a n a g e m e n t p r o g r a m : f u n d a m e n t a l s a n d d e v e l o p m e n t
Economizer Operation
Setpoints
A c c r e d i t e d T e x a s E n e r g y M a n a g e r
❯Occupied
-Occupant comfort
-Energy savings
-Cooling costs rise 1.5% for each degree below 72º
-Heating costs rise 1% for each degree above 68º
❯Unoccupied
-Energy savings
-Prevent building damage
-Use instead of turning systems off
Control Strategies
❯Demand limiting
-Demand limit setting
-Loads shed when setting reached
-Reduces peak demand & utility charges
❯Optimal startup
-Heating or cooling started before occupied time
-Setpoint reached at scheduled occupied time
❯Optimum stop
-Heating or cooling setback while facilities occupied
-Building allowed to “coast”
A c c r e d i t e d T e x a s E n e r g y M a n a g e r
More Control Strategies
❯Supply air temperature reset
-Based on return air or outside air temperature
-Reduces amount of reheat during cooling
❯Chilled water temperature reset
-Raise temperature of chilled water
-Based on outdoor temperature & humidity
-Caution not to raise temperature too much in humid conditions
❯Condenser water temperature reset
- Decrease temperature of water leaving cooling tower
- Increases chiller efficiency
- Reduces chiller capacity
A c c r e d i t e d T e x a s E n e r g y M a n a g e r
e n e r g y m a n a g e m e n t p r o g r a m : f u n d a m e n t a l s a n d d e v e l o p m e n t
Sample Display Screen
e n e r g y m a n a g e m e n t p r o g r a m : f u n d a m e n t a l s a n d d e v e l o p m e n t
Sample Display Screen
Ashley Williams, MCRP & ATEM
❯ Texas Energy Managers Association
❯ Director of Curriculum and Certification
questions
e n e r g y m a n a g e m e n t p r o g r a m : f u n d a m e n t a l s a n d d e v e l o p m e n t
Texas Energy Managers Association
❯ www.texasema.org
