1 Chiller Plant Control
Nov 08, 2014
1
Chiller Plant Control
Introduction to Trane Control Systems2 © 2010 Trane
What We Will Cover
• Factory-integrated controls on chillers
• Chiller plant control strategies
• Tracer control features
• Reliability and serviceability
• Chiller plant optimization
• Additional discussion
Introduction to Trane Control Systems3 © 2010 Trane
Trane AdaptiView™ Control System4th Generation Microprocessor Chiller Control
• Adaptive control – Reliable operation through difficult
operation conditions
• Feed-forward control– Accurate and stable control under
the most dynamic system transients
• Sophisticated diagnostics
• Fast restarts
• Operator tested – informative display
• Multiple open protocol communication options
Introduction to Trane Control Systems4 © 2010 Trane
Feed-forward control enables the chiller to respond
faster to load changes
• Feed-forward control uses flow change and entering water
temperature as an indication of load change
• It proactively compensates for load changes
Trane AdaptiView™ Control SystemFeed-forward Control
Introduction to Trane Control Systems5 © 2010 Trane
PID Feedback
42º?º
Typical Controller
Trane
UC800/AdaptiView
UC800 Feedback
40º56º
Feedforward
ΣΣΣΣ
DP
627 gpm
• Return Water Temp• Evaporator Flow
Trane AdaptiView™ Control SystemFeed-forward Control
Introduction to Trane Control Systems6 © 2010 Trane
• Directly measures chilled water flow
• Enhances leaving water temperature control during rapid flow rate changes of up to 50%/min.
– >30 % /min commercial control
– 10% /min precision process control
• Auto-tunes control gains to maintain stability and accuracy over chiller’s full range of flow rates.
Trane AdaptiView™ Control SystemVariable Flow Compensation
Introduction to Trane Control Systems7 © 2010 Trane
What Do Customers Really Care About ?
• Reliable chilled water flow
• Operating cost (energy efficiency)
• Operator safety
• Environmental awareness
• Reduced maintenance cost
Introduction to Trane Control Systems8 © 2010 Trane
Tracer Chiller Plant Control• Repeatability – performance from plant to plant
– Maximize the use of pre-engineered features
– Minimize on-site customization
• Flexibility – supports a variety of:– Plant layouts
– Chiller types
– Control strategies
• Maximized energy savings
– Load matching
– Chiller tower optimization
– Distributed pump pressure optimization
– Thermal ice storage
– Minimize manual intervention
• Minimized operational costs
– Minimize manual intervention, but anticipate it
– Maintain chilled water flow and temperature
– Minimize service surprises
Introduction to Trane Control Systems9 © 2010 Trane
LoadDetermination
Chiller Plant Control
ChillerSequencing
Chiller Plant Control
UserInterface
SystemOptimization
Introduction to Trane Control Systems10 © 2010 Trane
Plant Layout FlexibilityConstant Flow
Chiller #1
Chiller #2
CW SupplyTemp
CW ReturnTemp
UCP2UCP2
UCP2UCP2
Introduction to Trane Control Systems11 © 2010 Trane
Plant Layout FlexibilityVariable Flow - Decoupled
Air Handling Units
Control Valves
Variable-Speed
Drive
Pressure Differential Controller or Transmitter
Production
DistributionBypass Line
SU
PP
LY
DE
MA
ND
Chiller #1
Chiller #2UCP2
UCP2
UCP2UCP2
Introduction to Trane Control Systems12 © 2010 Trane
Plant Layout FlexibilityVariable Primary Flow
Air Handling Units
Control Valves
Production
DistributionBypass Line
SUP
PLY
DE
MA
ND
Variable-Speed Drive
Flow
Meter
UCP2UCP2
UCP2UCP2
Differential Pressure Sensor or
Transmitter
Introduction to Trane Control Systems13 © 2010 Trane
Pre-engineered Features
• Load determination
• Capacity matching
• Rotation
• Chiller setpoint control
• Failure recovery
• User interface
Installation and operating reliability and efficiency
Introduction to Trane Control Systems14 © 2010 Trane
Load Determination (when to add or subtract a chiller)
What is the optimal sequencing for chillers?
• Should I run one chiller at 100% or two chillers at 50%?
• The givens…– whether you run one chiller or two…
� The building load does not change
� The outside wet bulb temperature does not change
– When you run two chillers…
� You may double the number of pumps
� You may double the number of tower cells
Introduction to Trane Control Systems15 © 2010 Trane
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4
0 20 40 60 80 100
Percent Load
kW
/to
n
One Chiller at 100%? orTwo Chillers at 50%?
Constant Speed Centrifugal ChillerUnloading at constant condenser water temperature
Introduction to Trane Control Systems16 © 2010 Trane
Capacity Matching(turn the right chiller on)
Dependent on chiller plant design
• Normal - identical chillers
• Base - heat recovery/super efficient
• Pea - back up/alternate energy source/inefficient
• Swing - match the load!
• Custom - mix and match/nested CPC objects
Reduce operating costs
Introduction to Trane Control Systems17 © 2010 Trane
UCP2
450 Ton Chiller (Swing) 900 Ton Chiller
(Normal-1)
900 Ton Chiller (Normal-2)
UCP2
UCP2
0 2250450 18001350900
UCP2
Building Load (Tons)
Reduce operating costs
Introduction to Trane Control Systems18 © 2010 Trane
Flexible Rotation Which chiller is next?
• Schedule based
• Run-time
• Manual operator decision
• Customized
– Number of starts
– Other?
Reliable chilled water
Introduction to Trane Control Systems19 © 2010 Trane
Unload Before StartKeep chillers online
• Ride out flow transients on startups
– Deals with less sophisticated chiller controllers
• Variable flow / multiple pump systems
• Low supply water temperatures
Reliable chilled water
Introduction to Trane Control Systems20 © 2010 Trane
Failure Recovery Keep chilled water flowing
• No manual intervention required
• Follow the standard sequence
• Multiple failure inputs
– Chiller level
– System level
Reliable chilled water
Introduction to Trane Control Systems21 © 2010 Trane
Intuitive User Interface
• Minimize training time
• Minimize undesirable manual control
• Maximize operator efficiency
Reduced Operational Costs
Introduction to Trane Control Systems22 © 2010 Trane
Chiller - Tower Optimization Tower Setpoint Optimization
• Load
• Condenser watertemperature
• Wet bulb
• Tower design
• Load
• Condenser watertemperature
• Chiller design
Introduction to Trane Control Systems23 © 2010 Trane
Chiller - Tower Optimization Chiller–Tower Interaction
Condenser Water Temperature, °°°°F
400
74
En
erg
y C
on
su
mp
tio
n, kW
76 78 80 8272
300
200
100
084
Tower
Optimalcontrol point
Chiller
Total
Introduction to Trane Control Systems24 © 2010 Trane
Chiller - Tower OptimizationNorth America
350K
An
nu
al
Op
era
tin
g C
os
t, $
US
D
300K
250K
200K
150K
100K
50K
0Mexico City Orlando San Diego Toronto
55°°°°F Lvg Tower
Optimal Control
Design ECWT
Control Strategy
Introduction to Trane Control Systems25 © 2010 Trane
Air Handling Units
Control
Valves
Pressure
Differential
Controller or
Transmitter
• Critical valve reset
• Benefits
– Reduced pump energy
– Better coil control
– Extend pump life
Distribution Pumping Critical Valve Pressure Control
Reduce operating costs
Introduction to Trane Control Systems26 © 2010 Trane
Chiller Plant Dashboard Details
Daily Average MetricsPump Pressure
Pump Status
System and Chiller Status
Chilled Water Temps
Tower Water Temps
System Load
System Efficiency
Pump Flow
Introduction to Trane Control Systems27 © 2010 Trane
Summary
Key points to remember
• Integrated chiller controls
– Factory quality; better performance, efficiency and serviceability; lower risk
• Performance
– Temperature control; reliability; extended equipment life; automatic failure response
• Efficiency
– Lower energy and maintenance costs
• Sustainability
– Maintain performance over time
– Document performance
28
Thank you!