Large Chilled Water System
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Transcript of Large Chilled Water System
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Large Chilled Water SystemDesign Seminar
Presented by:
Larry Konopacz, Manager of Training & Education
Bell & Gossett Little Red Schoolhouse
This presentation is being brought to you
by:ASHRAE India Chapter and Xylem, Inc.
Saturday, September 21, 2013
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Large Chilled Water System Design Seminar
The Production Loop
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Chillers
Cooling towers
Free-Cooling &Waterside Economizer
Thermal Storage
Water Source Heat Pumps
Chilled Water Sources
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I Ton Ice =
2000 LB;1LB Ice =144 Btu;
1 Ton ice =288,000 Btu
Whats a Ton?
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12,000 Btu/h = 500 x gpm x tF = 1 ton
gpm/ton = 12,000/(500 x tF)
= 24/tF
Rule of 24
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What Types of Chillersare Available?
Centrifugal
Rotary screw
Reciprocating Absorption
Evaporator
Condenser
Compressor
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Refrigeration Cycle
Cooling
Tower
Condenser
CondenserWater Pump
Compressor
Motor
Expansion Device
Chilled
WaterPump
High
PressureZo
ne
LowP
ressureZone
L
oad
Hot Water Liquid Flow
Return
WaterVapor Flow
Cool Water
Supply
WaterEva
porator
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Where is What Used?
Large chilled water plants - centrifugal Mid-range size - rotary screw
Smaller chilled water applications -reciprocating
Inexpensive source of steam or other
energy source - absorption Combinations of the above
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CHILLERChiller 2
Chiller 1
SupplyReturn Common Pipe
Chiller Piping - Evaporator Side
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Supply
Return
CommonPipe
TripleDuty
Chiller 3
Chiller 2
Chiller 1TripleDuty
Typical Piping Method
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Supply
Return
Common
Pipe
Triple
Duty
Chiller 2
Triple
DutyChiller 1
Adding Pump Redundancy
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Piped forStandbyPumps
Supply
Return
CommonPipe
TripleDuty
Chiller 3
Chiller 2
Chiller 1
TripleDuty
Actuated Control Valve
Headered Primary Pumps
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Chiller Piping - Condenser Side
CondenserCondenser
Condenser
Pumps
Cooling Towers
Triple Duty
SRS SRS SRS
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TripleDuty
Standby Pump
Condenser
Condenser
Condenser
Multi-cell Cooling Tower
SRS
Multi-celled Cooling Tower
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Cooling Towers
Triple Duty
Condenser
Condenser
Condenser
Equalization
Line
SRS
Tower Equalization
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Cooling Tower Piping Practices
Fill all sections of pipe to purge air. Size piping at a minimum of 2 fps to
move free air bubbles to tower.
All piping installed below system purge
level.
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System Purge Level
SRS
Condenser Water Piping Above Grade
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Overhead Piping Concerns
Piping manifolds can result in low velocities. Low velocity will allow air to be released.
Air trapped in piping increases head required.
Piping installed above purge level compounds
problem.
Unpurged areas are potential sources ofproblems when pumps are turned on.
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Elevated Suction Piping Concerns
Condenser water pump difficult to purge. At start-up a manual air vent may be required.
During operation air will again accumulate.
Automatic air vent may not work.
If above the basin fill level, the result is
cavitation.
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Improper Piping Above Basin Level
System Purge Level
Basin Fill Level
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System Purge Level
SRS
Multi-tower System, Properly Piped
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Tower Piping Observations
At part load reduced velocities in headers may
allow air to be released.
Idle pumps will accumulate air that should be
released prior to starting the pump. Tower basins should be elevated to ensure
positive pressure under all flow conditions.
Pump casings should be fitted with automatic
air vents.
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Condenser Head Pressure Control
With centrifugal chillers a minimum supplywater temperature is needed to:
Maintain optimum efficiency
Maintain a minimum pressure differential
between condenser and evaporator
Prevent pressure imbalance
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Hermetic Compressor Guidelines
Condenser water temperature > 75 F. Establish 75 F within 15 minutes.
N/O condenser water throttling valve.
Three-way bypass valve can be used.
Constant condenser water flow.
Water temperature control through fan
modulation, or other methods.
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Open Compressor Guidelines
Condenser water temperature > 55 F. Three-way bypass valve can be used.
Constant condenser water flow.
Water temperature control through fan
modulation, or other methods.
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Water In Water out
Air in Air out
Cooling Towers
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Water out
Air in Air in
Water in
Air Out
Induced Draft, Counter-flow Tower
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Air Out
Air inAir in
Water out
Water in
Forced Draft, Cross-flow Tower
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Temperature Water Flow
Hot water F
Cold water F
Wet bulb F
L lb/min of water
L lb/min of water
Load
Range
(RF)
A
pproach
(
F)
Heat Load = L x R
Dynamic Relationship of Load,Approach, and Range
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Tower Size Relationships
Variables: Heat Load (Varies Directly)
Range (Varies Inversely)
Approach (Varies Inversely)
Wet-bulb Temperature (Varies Inversely)
Varying any of these variables will affect
the size of the tower.
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Types of Free-Cooling(Waterside Economizer)
Water out
Air in Air in
Water in
Air Out
Earth ContactEvaporative
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Earth Contact Characteristics
Usually indirect. Cooling medium and load separated by heat
exchanger.
Stable temperatures. Water temperature limitations.
Water treatment and pumping costs.
Environmental concerns.
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Heat Exchangers
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How do they work?
Thin plates are stamped with
a unique chevron pattern andassembled in a frame
Four holes punched in the
plate corners form a
continuous tunnel which actsas a distribution manifold for
the inlet and outlet of each
fluid
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How do they work?
Each plate has a gasket that
confines the fluid to the portor to the heat transfer area of
the plate
Units are built to order with a
standard 150 psi ASME Codestamped design or to custom
designs
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LOAD
C
O
N
D
E
V
A
P
Triple Duty
Sediment RemovalSeparator
Triple Duty
TOWER
H
E
A
T
E
X
C
H
GPX
Earth Contact - Summer Cycle
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LOAD
C
O
N
D
E
V
A
P
Triple Duty
Sediment RemovalSeparator
Triple Duty
TOWER
H
E
A
T
E
X
C
H
GPX
Earth Contact - Winter Cycle
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Evaporative Characteristics
Heat rejection device (tower) exists. As temperature declines, opportunity
arises.
Higher sensible vs. latent loads
Leaving water temperature approaches
42 F. Freeze protection may be required.
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Freeze Protection
Sump heaters. Close temperature control.
Accurate water level control.
Prevention of moist air recirculation.
External piping freeze protection.
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Evaporative Cooling - Direct
LOAD
C
ON
D
E
VA
P
Triple Duty
Triple DutySediment Removal
Separator
TOWER
Single Tower, Summer Cycle
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LOAD
C
O
N
D
E
V
A
P
Triple Duty Triple Duty
Sediment Removal
Separator
TOWER
* Alternate location of SRS, depending on
system conditions
NOT RECOMMENDED
Single Tower, Winter Cycle
Evaporative Cooling - Direct
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Evaporative Cooling - Indirect
LOAD
C
O
ND
E
V
AP
Triple Duty
Sediment Removal
Separator
Triple Duty
TOWER
H
E
A
T
E
X
C
H
GPX
Single Tower/GPX, Summer Cycle
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Evaporative Cooling - Indirect
LOAD
C
O
ND
E
V
AP
Triple Duty
Sediment Removal
Separator
Triple Duty
TOWER
H
E
A
T
E
X
C
H
GPX
Single Tower/GPX, Winter Cycle
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COND. WATER
CH. WATER
TEMP.
DEG. F
EXCHANGER
LENGTH
57=
42=
45=
52=
7F TEMPERATURE
CROSS
3F COOLING
APPROACH
T1
t2
t1
T2
Temperature Cross and Approach
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Temperatures are in F Flow is in USGPM
Heat exchanger selection based on max pressure drop of 7 psi
10/3.92=2.55 Approach = 3F10/4.93=2.03 Approach = 4F
10/5.94=1.69 Approach = 5F
COND. WATER CH. WATER LMTD AREA EXCH. COST
EWT LWT FLOW EWT LWT FLOW DEG F SQ.FT. MODEL INDEX
42 52 1000 57 45 834 3.92 1390 GPX807 1.00
42 52 1000 58 46 834 4.93 1135 GPX807 0.85
42 52 1000 59 47 834 5.94 975 GPX807 0.76
Heat Transfer Area vs Approach
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Production Source - Thermal Storage
Application Criteria Economics
Storage Media
Storage Technologies
System Configurations
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Application Criteria
High maximum load. Significant premium for peak demand.
Incentives.
Limited space available.
Limited electrical capacity.
Back-up or redundancy required.
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Storage Media
Chilled Water Ice Harvesting
External/Internal Ice Melt
S f C S
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T
Vent
Load
Pressure sustainingand check valve
StorageWarm
Cool
Variable volumedistributionpump
Constant volumeprimary pump
Chiller
Stratified Chilled Water System
T t St tifi ti
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30 40 50 60 70
-5
-10
-15
Bottom -20
Top 0
Deptho
ftank,ft
Temperature, F
Thermocline
Temperature Stratification
U f P S t i i V l
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Vent
Pressure sustaining
and check valve
StorageWarm
Cool
Constant volume
primary pump
Chiller
Distributionpump
Primarypump
Load
Transfer PumpDirectioncontrolvalves
Use of Pressure Sustaining Valves
I ti H t E h
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Load
T
Vent
Pressure sustainingand check valve
StorageWarm
Cool
Variable volumeprimarypump
Constant volumeprimary pump
Chiller
T
Heat
Exchanger
Variable volumesecondarypump
Incorporating Heat Exchangers
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Section1
Section2
Section3
Section4
Ice harvester
chiller
Load
Chilled water
pump
Ice waterrecirculation
pump
Ice Harvesting System
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Charging ModeDischarging Mode
External Melt Ice Storage
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Ice
WaterIceCold glycol
Warm glycol
Charging Mode Discharging Mode
Encapsulated Ice StorageCharge and Discharge Modes
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Tons
Time of Day
Cooling load
(met by storage)
Charging
Storage
Charging
Storage
Chiller meets load directly
Chiller on
Chiller off
Full Storage Strategy
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T
ons
Time of Day
Cooling load(met by storage)
ChargingStorage
ChargingStorage
Cooling load
(met by chiller)
Chiller runs continuously
Partial Storage - Load Leveling
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Tons
Time of Day
(met by storage)Charging
StorageCharging
Storage
(met by chiller)
Cooling load
Reduced on-peak demandPartial Storage - Demand Limiting
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Production Source - Water Source Heatpumps
Growing market segment System temperature range 40 - 90 F
Energy added below 40 F (heat)
Heat removed above 90 F (cooling
tower)
Heat Pump Cycles Water Source
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Air Coil(Evaporator)
CoolAir Compressor
Reversing Valve
Capillary
Air Conditioner Cooling
Air Coil(Condenser)
WarmAir
Reversing Valve
Capillary
Air Conditioner Heating
Water Coil(Evaporator)
Water Coil(Condenser)
System WaterSupply
Return
Compressor
Refrigerant
Loop
Heat Pump Cycles - Water Source
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Design Considerations
Use slow closing two-way valves foreach zone
Good system balance required
Use staged c/s or v/s pumps
Use with cooling towers and GPX
Use with closed circuit cooling towers
Heat Pump-Water Source Schematic
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Water Source
Heat Pump
Water Source
Heat Pump
Water Source
Heat Pump
Water Source
Heat Pump
Water Source
Heat Pump
Water Source
Heat Pump
Water Source
Heat Pump
Water Source
Heat Pump
Water Source
Heat Pump
Buffer
Tank
( Optional )
Compression
Tank
Gasketed
Plate Heat
Exchanger
Cooling
Tower
Heat Pump-Water Source Schematic
Heat Pump-Water Source Schematic
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Closed Circuit Cooler
Heat Rejecter
Water SourceHeat Pump
Water SourceHeat Pump
Water SourceHeat Pump
Water SourceHeat Pump
Water SourceHeat Pump
Water Source
Heat Pump
Water Source
Heat Pump
Water Source
Heat Pump
Water Source
Heat Pump
Buffer
Tank
( Optional )
Compression
Tank
Heat Pump-Water Source Schematic
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Comments?
Questions?Observations?
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Large Chilled Water System Design Seminar
Variable Volume Distribution
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Variable flow through coilConstant flow through system
Three Way Valve
Variable flow through coilVariable flow through system
Two Way Valve
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Three-Way Valve Systems
Low return temperatures Balance problems
Increased flow at part load
Extra chillers to provide flow at low t
Chillers operate at high kW/ton
Two Way Valve System with
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C
H
I
L
L
E
R
C
H
I
L
L
E
R
Two-Way Valve System with
Chiller BypassA
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We want:
a. variable volume, to save pumping
costs at part load,
b. constant flow through the chiller to
protect it.
A Solutiona. constant flow primary system for the chillers
b. variable flow secondary system for the load
A Problem
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C
HI
L
L
E
R
C
HI
L
L
E
R
C
HI
L
L
E
R
Return
Primary-SecondaryCommon Pipe
SupplyPrimary Loop
Production
Secondary Loop
Distribution
Primary-Secondary Terms
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Fundamental Idea
Secondary
Pump
Tee
APrimary
Pump
Tee
B
Low pressure drop in the common pipe
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Primary-Secondary Pumping
The idea is based on:
Conservation of Mass
Conservation of Energy
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50 GPM100 GPM
50 GPM
Law of the Tee: Diversion
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40 GPM60 GPM
100 GPM
Law of the Tee: Mixing
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No Secondary Flow
100 GPM @ 45F
Secondary
Pump
Off
A B100 GPM @ 45F
100 GPM @ 45FPrimary
Pump
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Primary = Secondary
100 GPM @ 45F0 GPM
Pump On
A B
100 GPM @ 45F 100 GPM @ 55F
100 GPM @ 55F
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Primary > Secondary
Pump On
A B
Mixing at Tee B
100 GPM @ 45F
50 GPM @ 45F
100 GPM @ 50F
50 GPM @ 55F
50 GPM @ 45F
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Pump On
A B
Mixing at Tee A
100 GPM @ 45F 100 GPM @ 55F
100 GPM @55F
200 GPM @ 50F 200 GPM @ 55F
Primary < Secondary
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Two-way Valve
Control Valve in Secondary
Primary-Secondary Pumping
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C
H
IL
L
E
R
C
H
IL
L
E
R
C
H
IL
L
E
R
Return
Primary-SecondaryCommon
SupplyPrimary Loop
Production
Secondary Loop
Distribution
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Common Pipe Design Criteria
Use the flow of the largest chiller
Chiller staging at half of this flow is
common
Head loss in common
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Return
Supply
PumpController
SecondaryConstant Speed
Pumps
Common
Chiller3
Chiller2
Chiller1
Design of the Common Pipe
10 dia.
Common Pipe Configurations
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A B
C D
Secondary System Curve
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Head
F1 F2 F3
H1
H2
H3
Flow
Control Valves
Closing
Control Valves
Opening
Typical System
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From Loads
Common
To LoadsProduction
Secondary Pumps
1500 gpm each
Distribution
Ch
iller2,off
Chiller1,on
1500 gpm
each
45F
Production = Distribution
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Common -- No Flow
SecondaryPumps
1500
1500
1500 15000
CHWS Temp45oF
CHWR Temp
55
o
F
ECW Temp
55
o
F
1500
Chille
r2,off
Chille
r1,on
Distribution > Production
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Common -- 500
Secondary
Pumps
1500
2000
1500 20000
CHWS Temp
47.5oF
CHWR Temp
55o
F
ECW Temp
55o
F
Mixing (1500 @ 45) + (500 @ 55)
Chiller
2,off
Chiller
1,on
2000
Check Valve in Common?
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>1500 GPM
Return
Common
Supply
>1500 GPM
0 GPM
>1500 GPM
@ 47.5oF
>1500 GPM
@ 55oF
Be Careful!
C
hiller2,off
C
hiller1,on
What can we do?
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Step
Function
Linear
Function
Return
Primary/Secondary
Common
Supply
Production
Distribution
Chiller3
Chiller2
Chiller1
Typical Load Profile
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0-10 30-40 60-70 90-100
0
5
10
15
20
25
30
0-10 30-40 60-70 90-100
%T
ime
% Load
Multiple Chillers
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Chiller2
,
60%
Chiller1
,
40%
% Load
% Time
100
80
60
40
20
100755025
Chiller 1
Chiller 2
1
12 2
What else can we do?
Reset S ppl Temperat re
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Reset Supply Temperature
Lower chiller set point when mixing occurs to
maintain a constant temperature to the system. Allows us to mix colder water and maintain supply
temperature to secondary. (coils)
Expect increases in cost of chiller operation atlower set point: 1-3% per degree of reset.
Adds to control complexity.
Delays start of the next chiller.
Production > Distribution
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Common -- 900
Secondary
Pumps
3000
2100
15002100
1500
CHWS Temp
45oF
CHWR Temp
55o
F
ECW Temp
52o
F
Mixing (2100 @ 55) + (900 @ 45)
(Flow in GPM)
P/S Chiller Bridge - Front Loaded Common
Chiller1,on
Chiller2,on
Loading a Chiller
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Loading a Chiller
A chiller is a heat transfer device. Like
most equipment, it is most efficient at
full load.
To load a chiller means: Supply it with its rated flow of water
Insure that water is warm enough to permit
removal of rated Btu without freezing thewater
Chiller Performance Curve
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Chiller Performance Curve1.1
20 30 40 50 60 70 80 90 10010
1.0
0.9
0.8
0.7
0.6
0.5
KWper
Ton
Percent Load
Typical Load Profile
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0-10 30-40 60-70 90-100
0
5
10
15
20
25
30
0-10 30-40 60-70 90-100
%T
ime
% Load
Typical Load Profile
60/40 Chiller Split to Help Minimize
Low Part Load Operation
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Chiller
2,60%
Chiller
1,4
0%
% Load
% Time
100
80
60
40
20
100755025
Chiller 1
Chiller 2
1
1
2 2
Low Part Load Operation
Three Unequally Sized Chillers
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% Load
% Time
100
80
60
40
20
100755025Chiller 1
or
Chiller 2
Chiller 3
Chiller 1and
Chiller 2
Chiller 1 orChiller 2and
Chiller 3
Chiller
2,4
0%
Chille
r1,4
0%
Chiller
3,60%
Three Unequally Sized Chillers
Approaching Flow = Load
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% Load
Time
Approaching Flow = Load
Applying a Variable Speed Chiller
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% Load
% Flow
100755025
100
75
50
25
Ch 1Ch 2 Ch 3 Ch 4
Ch 1Ch 2 Ch 3
Ch 1Ch 2
Ch 1
Applying a Variable Speed Chiller
Back Loaded Common
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From loads
Common
To Loads
Chiller3
Chiller2
Chiller1
Production = Distribution
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Common
0 Flow
Secondary
Pumps
1500
CHWS Temp
45oF
CHWR Temp
55o
F
Chiller2,off
Chiller1,on
1500
1500
15001500
Distribution > Production
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Common
500 gpm
SecondaryPumps1500
2000
1500 20000
CHWS Temp47.5oF
CHWR Temp
55o
F
500
Mixing (1500 @ 45) + (500 @ 55)
500
Chille
r1,on
Chille
r2,off
Production > Distribution
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Common900
SecondaryPumps1500
2100
1500
2100
1500 GPM
@ 49oF
CHWS Temp45oF
CHWR Temp55oF
Mixing (900 @ 45) + (600 @ 55)
900 600
900 GPM@ 45oF
600 GPM@ 55oF
1500 GPM
@ 55oF
Chiller2,on
Chille
r1,on
Maximize Free Cooling
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Return
Supply
PumpController
Secondary
Pumps
Primary-SecondaryCommon
Chiller3
Chiller2
FreeCooling
Primary-Secondary System
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Return
Supply
PumpController
SecondaryPumps
Primary-SecondaryCommon
Chiller3
Chiller2
Chiller1
Pump Horsepower Comparison
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BHP
125
100
75
50
25
150
25 50 75 100
Design Coil Flow
%
Primary Pumps = V/V
Secondary Pumps +
Constant Flow Primary Pumps, only
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2012 ASHRAE Handbook - HVAC Systems and Equipment, p 44.11
140
150 Pump Over-headed by 150%Constant Flow, C/S Pump
(3 Way Valve)
Constant vs Variable Volume
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% Flow
90
80
70
60
50
40
30
20
10
0 10 1009080706050403020
100
110
120
130
BaseDesign
HP %
% Full Load
(Design) HP
Constant Flow, C/S Pump
(3 Way Valve)
C/S Pump
(2 Way Valve)
Pump Head Matchedto System @
Design Flow
Impact of Piping Length and Overheading
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0
50
100
150
200
250
300
350
0 1000 2000 3000 4000 5000 6000 7000 8000 9000
Pipe Length , Feet
Yearly
Opera
tingCostx
$1
000
c/s @ 1.0
c/s @ 1.25
c/s @ 1.50
c/s @ 2.0
Always Size the Pump to the System!
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But...
Uncertainties
Coils
Control valves Primary data
Lead times
Dealing With an Overheaded Pump
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Throttle at the discharge valve
Limits on the valve
Flow balance & trim pump impeller
Required by ASHRAE/IES 90.1
Additional Concerns
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Pump Protection at minimum flow
Chiller Staging and De-staging
instrumentation.
Pump Protection
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Minimum recommended flow from ESP Plus = 900 gpm
Bypass Options
1. Establish a minimum flow equal to or greater than
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q g
the minimum required to protect the pump.
2. Install a bypass at the end of the mains with a
balance valve to set minimum flow.
3. Install a bypass at ends of zones.
4. In retrofits, leave a three way valve at the end of the
system.
5. Use P or flow sensing to open pump bypass only
when needed.
6. V/S pumps are not as big a problem because oflower head at reduced flow.
System Bypass Options3
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6
Return
Supply
Pump
Controller
Secondary
Constant Speed
Pumps
PrimarySecondary
Common
Chiller3
Chiller2
Chiller1
2
5
T
Chiller Staging Instrumentation
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From Loads
Common
To Loads
Production
Secondary/Pumps
Distribution
Chille
r2,off
Chiller
1,on
FP
FSTS-S
TS-RTP-R
TP-S
Common Pipe Flow Indication
Distribution
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From LoadsCommon
To Loads
Production
Secondary/PumpsChiller2
Chiller1
Flow
Swi
tches
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Large Chilled Water Design Seminar
Variable Speed Pumping
Why variable speed?
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y p
1. When should I use it?
2. How does it work?
3. What about variable primary flow?
Typical operating load profile
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2% 3%5%
15%
20%
30%
15%
5%3%
2%
Bell & Gossett 70V
1970s
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Adjustable Frequency Drives
Rectifier section
t AC t DC
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converts AC to DC
several varieties available Inverter section
forms a synthetic sine wave
several varieties available
maintains a controlled frequency/voltage ratio
Requires an automatic control system Adds to the initial cost of the system
Affinity Laws
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1. Capacity varies as the RPM change ratio:
FLOW 2 = FLOW 1 ( SPEED2 / SPEED 1)
2. Head varies as the square of the RPM change ratio:
HEAD 2 = HEAD 1 (SPEED 2 / SPEED 1)2
3. Brake horsepower varies as the cube of the RPM change ratio:
BHP 2 = BHP 1 (SPEED 2 / SPEED 1)3
Affinity Laws for Centri fugal Pumps
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0
10
20
3040
50
60
70
80
90
100
0 10 20 30 40 50 60 70 80 90 100
Flow/Speed, Percent
P
ercent
Flow
Head
Horsepower
Theoretical Savings120
110
100
120
110
100
Pump Curves 100% Speed
90% Design
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%H
ead
%B
HP
% Design Flow
90
80
5040
30
2010
70
60
90
80
50
40
30
2010
70
60
0 0
80%
70%
60%
50%
40%
30%
Head
Flow
BHP
10 20 30 40 50 60 70 80 90 1000
HP Draw
Head
Required Differential Pressure
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P Sensor/Transmitter25 Ft. Head
System Curve
& V/S Control System
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Flow
piping headloss curve
Distribution
Pum
pTDH
Overallsystem curve
Head
80
60
40
20
110
0200 400 600 800 1000 1200 1400 16000
100
Set Point
25 FT Differential HeadMaintained Across Load
(Set Point)
Effect of Constant* Set Point110
100
As the valve closes,
the pump slows down
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piping headloss curve
Distribution
PumpT
DH
Overall system curve
Head
80
60
40
20
0200 400 600 800 1000 1200 1400 16000
Flow
Control curveSet point,
25 FT
*Whats Constant?
AB
Pump
Initial Speed
Control Curve
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Q1Q2Flow, Q
(gpm)
Head, H
(feet)
Decrease in Heat Load Results in Troom < T set pointCauses Two Way Valves to Throttle Flow
Pipe, Fitting
Friction Loss
AB
Pump
CurveControl Curve
Speed 1
Speed 2
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Q1Q2Flow, Q(gpm)
Head, H(feet)
Decrease in Pump Speed Reduces Flow, Reduces Error
Speed 2
C
Q3
Pipe, Fitting
Friction Loss
AB
Control CurveSpeed 1
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System Operation on Control Curve at Lower Speed
Q1Flow, Q(gpm)
Head
(ft) Pipe, Fitting
Friction LossFinal Speed C
Q4
V i bl H d L
Constant Head Loss
Variable vs Constant Head Loss
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Return
C
HI
L
L
E
R
C
HI
L
L
E
R
C
HI
L
L
E
R
Supply
Variable Head Loss
PumpController
Adjustable Freqy. Drives
90
100C/S, Constant Flow System Pump Head Matched to
System at Design FlowBase
Variable Head Loss Ratio
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PercentD
esignBHP
% Flow
90
80
70
60
50
40
30
20
10
0 10 1009080706050403020
C/S, Variable Flow V/S, 0% Variable Hd Loss, 100% Constant Hd
V/S, 25% Variable Hd Loss, 75% Constant Hd
V/S, 50% Variable Hd Loss, 50% Constant Hd
V/S, 75% Variable Hd Loss, 25% Constant Hd
V/S, 100% Variable Hd Loss, 0% Constant Hd
Variable Head Ratio w/
Overheading
140
150 Pump OHeaded by 150%Constant Flow, C/S Pump
(3 Way Valve)
C/S P
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90
80
70
60
50
40
30
20
10
0 10 1009080706050403020
100
110
120
130
Base
Design
HP %
% Full Load
(Design) HP
Constant Flow, C/S Pump
(3 Way Valve)
C/S Pump
(2 Way Valve)
Pump HD Matched
to System @Design Flow
* 25/75 Means:25 % Variable HD Loss
75 % Constant HD Loss
120
11080 %
85 %80 %70 %60 %
50 %
85 %
% Efficiency
V/S Curves
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100
90
80
50
40
30
20
10
70
60
0100 200 300 400 500 600 700 800 900 10000
100 %
90 %
80 %
70 %
60 %
50%
40 %
30 %
80 %
% Speed Curves
ConstantEfficiencyCurve
Head
,Feet
GPM
120
11080 %
85 %80 %70 %60 %
50 %
85 %
% Efficiency
Efficiency Changes
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100
90
80
50
40
30
20
10
70
60
0
100 200 300 400 500 600 700 800 900 10000
100 %
90 %
80 %
70 %
60 %
50%
40 %
30 %
80 %
% Speed Curves
Constant
Efficiency
Curve
Head
,Feet
GPM
Minimum Drive Speed120
110
100 100 %
80 %85 %80 %
70 %60 %50 %
85 %
% Efficiency
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90
80
50
40
30
20
10
70
60
0
100 200 300 400 500 600 700 800 900 10000
90 %
80 %
70 %
60 %
50%
40 %
30 %
% Speed Curves
ConstantEfficiency
Curve
Head,
Feet
GPM
Variable Head Loss
Constant Differential Head Loss
Multiple Pump System Staging
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Return
C
HI
L
L
E
R
C
HI
L
L
E
R
C
HI
L
L
E
R
Supply
Variable Head Loss
PumpController
Adjustable Freqy. Drives
Parallel V/S Operation
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Control Curve
Pump 1
Pumps 1 & 2 Pumps 1, 2 & 3
1770 RPM
600 RPM 900 RPM
1150 RPM
1450 RPM
Set PointTechnologic
P
AdjustableFrequency
3f , 60 Hz Power
(Control Agent)
Set Point+/- error
Variable Speed Pumping Equipment
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Set Point(Input Signal)
PumpController
FrequencyDrive
(Controlled Device)
SystemSensor/
Transmitter
3f, Variable FrequencyVariable Voltage
FeedbackSignal
ControlledVariable
The Controlled Variable Determines the Type of Sensor
Pressure
Differential
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DifferentialPressure
DifferentialTemperature
Flow
PumpController
Temperature
4-20ma
signal
Set PointTechnologic
Pump
AdjustableFrequency
3f , 60 Hz Power
(Control Agent)
Set Point+/- error
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(Input Signal)Pump
Controller
q yDrive
(Controlled Device)
SystemSensor/
Transmitter
3f, Variable FrequencyVariable Voltage
FeedbackSignal
ControlledVariable
Technologic Pump
Controller
Controls pumps and drives
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Controls pumps and drives
Accept set point, analyze sensor input
PID function
Pump staging
Pump alternation Recognize and react to component failure
Provide message display
Central management system link Safeguard system
PID Control Eliminates offset from set point
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Eliminates offset from set point
Allows for timely speed change
Handles large, sudden disturbances
Prevents oscillation and over-damping
Set Point( S )
TechnologicPump
Adjustable
Frequency
3f , 60 Hz Power
(Control Agent)
Set Point+/- error
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(Input Signal)Pump
Controller Drive
(Controlled Device)
SystemSensor/
Transmitter
3f, Variable FrequencyVariable Voltage
FeedbackSignal
ControlledVariable
Adjustable Frequency Drive
ConstantVoltage &F
RectifierSection
DirectCurrent
InverterSection
VariableVoltage &Frequency
PumpMotor
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Frequency
Power
Section Current Section Frequency
Power
Motor
Some important issues:
Rectifier and Inverter Design
Drive EfficiencyRFI and EMI Noise
Audible Noise
Size and Cost
Manual drive bypass
100
120
Typical Efficiency Range
Variable Speed Drives
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0
20
40
60
80
0 20 40 60 80 100
Design Speed, %
E
fficiency,% Currently AvailableAFDs
Typical Older AFDs
Other Types
Pump and Motor
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The Pump
Minimum Flow
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Minimum Flow
Minimum Speed
Inverter Duty
Motors
Motor Couplers
Maintaining Minimum Flow120
110
100
90
100 % Speed
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80
50
40
30
20
10
70
60
0
10 20 30 40 50 60 70 80 90 1000
% Flow
Head
30% Speed
EPDM couplers on variable-speed pumps
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Failed Hytrel Coupler from a Variable
Speed Pump
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Variable FlowThrough
The Evaporator
Variable Head Loss
Constant Differential Head Loss
Primary-Secondary System
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Return
C
HI
L
L
E
R
C
HI
L
L
E
R
C
HI
L
L
E
R
Supply
PumpController
Adjustable Freqy. Drives
Primary-Secondary
Common Practice.
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Why?
Protection. Nuisance shutdowns.
Freezing.
Costly downtime.
Variable Primary Flow
Flow Meter, optionTwo-position Control Valves
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AFD AFD AFD
CHILLER
CHILLER
CHILLER
Modulating
Valve
DP
Sensor
Controller
DPSensor D
PSensorD
PSensor
Whats different? Primary pumps only Flow meters or p sensors at each
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chiller.
Two-position isolation valves at each
chiller Minimum flow bypass with a modulating
control valve.
Smarter controller.
Alternative #1
Minimum Flow Bypass at Chillers
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Minimum Chiller Flow
Minimum Pump flow
Ganged Pumps
DPSENSOR
FLOWMETER
DPSENSOR
DPSENSOR
DPSENSOR
DPSENSOR
SIGNALTO TECH
SIGNAL SIGNAL BYPASS:
T
FFF
CHILLER CHILLER CHILLER
SUPPLY
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AFD AFD AFD
SIGNALSTO TECH
SIGNAL
TO TECH
SIGNAL
TO TECH
NOTE:
ALL SENSORSIGNALS WIRED TOTECHNOLOGIC5500
BYPASS:
FOR SYSTEMS WITHEXTENDED LIGHT
LOADS/WEEKENDSHUTDOWNS. SETBALANCE VALVEFOR LOW FLOW TOREDUCE THERMALSTRATIFICATIONAND ALLOW QUICKSTART UP AFTER
SHUT DOWN.
T
SIGNALSTO TECH
SIGNALSTO TECH
F
T
FLOWMETER/TRANSMITTER
TEMPERATURE SENSOR
ISOLATION VALVE
CHECK VALVE
RETURN
TDV TDV TDV
Monitoring Chiller Flow
P sensors - Technologic controller ensures the chilleris in proper working condition by monitoring each
working chillers differential pressure. Flow through the
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chiller is calculated using the values defined in the usersetup.
OR
Flow sensors - Technologic controller ensures the chiller
is in proper working condition by monitoring each
working chillers flow rate.
Technologic 5500 Initial programming is
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crucial. Must use accurate data
from the chiller
manufacturer. Start-up coordination
should include the BMS
too.
Technologic 5500 Control Variables
1. Monitor zone differential pressure sensors,
compare actual values to the required set points.
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Pump speed is modulated to maintain set point. Pump staging will occur as required to meet set point.
Control sequence is exactly as described earlier.
Technologic 5500 Control Variables2. Determine if the minimum flow requirements are
being met for all working chillers.
Prevents freeze-up or chiller low-flow trips
If chiller flow is too low, controller opens minimum flow
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, p
bypass valve in programmed increments. Size the valve
for system p.
Requests de-staging action from the chiller control
system or BMS.
Allows for operator intervention, decision making.
Required by code in some areas.
Ganged pumps allow operation of two chillers with one
pump.
Technologic 5500 Control Variables
3. Monitors chiller flow rate to prevent operation
above the maximum flow for the chillers and the
pumps.
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Excess chiller flow generates a request to stage on anadditional chiller. Minimum flow bypass valve is closed.
Operator or BMS intervention required.
Ganged pumps allow operation of one chiller, twopumps.
Optional system flow meter provides end-of-curve
protection for the pumps
Alternative #2
Bypass at End of System
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Minimum chiller flow
Minimum pump flow
Ganged Pumps
DPSENSOR
FLOWMETER
DPSENSOR
DPSENSOR
DPSENSOR
DPSENSOR
SIGNALTO TECH
T
FFF
SUPPLY
CHILLER CHILLERCHILLER
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AFD AFD AFD
SIGNALSTO TECH
SIGNALTO TECH
SIGNALTO TECH
NOTE:ALL SENSORSIGNALS WIRED TOTECHNOLOGIC5500
T
SIGNALSTO TECH
SIGNALSTO TECH
F
T
FLOWMETER/TRANSMITTER
TEMPERATURE SENSOR
ISOLATION VALVE
CHECK VALVE
RETURN
TDV TDV TDV
Alternative #2
Minimum flow bypass valve is controlledto protect both the pumps and the
chillers.
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Pump requires >25% BEP flow
Minimum flow of largest chiller
Size the bypass valve using the zonep.
Best for systems with extended light
loads or weekend shut-down.
Alternative #3
Primary pumps piped directly to chillers.
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More common in retrofit systems.
Easier for applying un-equally sizedchillers in parallel.
DPSENSOR
FLOWMETER
DPSENSOR
DPSENSOR
DPSENSOR
DPSENSOR
SIGNAL
TO TECH
SIGNAL
TO TECH
SIGNAL
TO TECH BYPASS:
T
FFF
CHILLER CHILLER CHILLER
SUPPLY
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AFD AFD AFD
SIGNALS
TO TECH
TO TECH TO TECH
NOTE:
ALL SENSOR
SIGNALS WIRED TOTECHNOLOGIC5500
BYPASS:FOR SYSTEMS WITHEXTENDED LIGHT
LOADS/WEEKENDSHUTDOWNS. SETBALANCE VALVE
FOR LOW FLOW TOREDUCE THERMAL
STRATIFICATIONAND ALLOW QUICKSTART UP AFTER
SHUT DOWN.
T
SIGNALS
TO TECH
SIGNALS
TO TECH
F
T
FLOWM ETER/TRANSMITTER
TEMPERATURE SENSOR
CHECK VALVE
ISOLATION VALVE
TDV TDV TDV
RETURN
Pump Selection Equal size pumps. Redundancy.
P t
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Parts. Maintenance.
Unequal size pumps.
Control issues.
Flow issues.
Premature failure, large pump at low flow.
Chiller Selection Equal size chillers.
R d d
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Redundancy. Parts.
Maintenance.
Unequal size chillers.
Control issues.
Flow issues Additional equipment.
Design Considerations
Size bypass for minimum flow of largest chiller.
Minimum building load?
Size bypass modulating valve
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for system p, if its installed near the chillers
for zone p, if its out in the system.
Program the controller with the chiller
p setpoints for minimum and maximum chiller flow.
Verify with chiller manufacturer.
Design Considerations
Sequence chillers based on p or temperature
sensors.
Use accurate calibrated flow meter or p sensors
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Use accurate, calibrated flow meter or p sensorsat each evaporator
Allow for operator training.
Initial
On-going
Consider this design if:
System flow can be reduced by 30%.
System can tolerate modest changes in water
temperature
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temperature.
Operators are well trained.
Demonstrates a greater cost savings.
High proportion of operating hours at:
Part load.
Full load with low entering condenser water.
Turn-down Ratio
Chiller manufacturers publish 3 - 11 fps
evaporator velocity range (typically).
You may have to increase your
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You may have to increase your
acceptable head loss targets, use more
pump head. Nominal base of 7 fps desirable.
Variation of 1 to 2 fps.
Work with the manufacturer.
Rate of Change*Maximum rate of flow change, % design flow per minute
Source Vapor Compression Absorption
#1 4-12 **
#2 20 30 2 5
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#2 20-30 2-5
#3 ** 30
#4 2 **
#5 ** 1.67
*Table 2-2
ARTI-21CR/611-20070-01, 2004, Bahnfleth & Peyer
** Information not provided
Do not use if:
Supply temperature is critical.
Three way valves are used throughout
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Three-way valves are used throughout.
Existing controls are old, inaccurate.
Operators are unlikely to operate the
system as designed.
Supply Water Temperature
Dependant on : System volume.
Rate of flow change.
A li ti ifi
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Application specific.
Consider thermal storage
Operator Ability
Within operators ability?.
Commercial buildings may not have well
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Commercial buildings may not have wellqualified operators.
Training is mandatory.
Initial
Periodic, in view of operator turnover.
Start-Up & Shut-down
In systems that start-up and shut-down, it
may be advisable to anticipate, and
avoid rapid changes in flow as control
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avoid, rapid changes in flow as controlvalves all tend to act together.
Control system, BMS, manual
procedures.
Use slow opening/closing valves at the
chiller, 60-90 seconds.(?)
Controls Complexity
Additional controls for the chillers
Additional controls the pumps
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Additional controls the pumps. Pumps operate on flow, temperature, and
P.
Chiller P.
Sensor Calibration
Multiple sensors control:
Flow.
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Flow. Temperature.
Delta p
Maintenance.
Calibration.
Summary
Evaluate all the options.
Read some articles:
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Read some articles: Variable Primary Flow CHW: Potential Benefits and Application Issues
by Bahnfleth and Peyer. Pennsylvania State University, ARTI-
21CR/611-20070-01
Chilled Water System for University Campus by Stephen W. Duda, PE,
ASHRAE Journal May, 2006
Another tool for the toolbox.
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Large Chilled Water System Design Seminar
Primary-Secondary-Tertiary Pumping Systems
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Zone A
Zone C
Primary-Secondary-Tertiary
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C
H
I
L
L
E
R
C
H
I
L
L
E
R
Zone B
Variable Speed Pump
Zone AZone B Zone C
WRONG !
Direct Pumped Zones
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C
H
I
L
L
E
R
C
H
I
L
L
E
R
DP Controller
WRONG !
WRONG !
Zone A Zone B Zone C
T
Constant Demand Zones
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WRONG !
Automatic
Flow Control
ValveHard set valve
C
H
I
L
L
E
R
C
H
I
L
L
E
R
Zone A
Zone C
Primary-Secondary-Tertiary
RIGHT !
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C
H
I
L
L
E
R
C
H
I
L
L
E
R
Zone B
Variable Speed Pump
RIGHT !
Three Different Buildings
A has coils selected for 44F.
B has coils selected for 45F.
C has coils selected for 46F
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C has coils selected for 46 F.
Therefore, the supply water temperaturemust be at least 44F for A.
But what about B and C?
Zone A
Zone B
Zone C
Primary-Secondary-Tertiary
can be even more useful
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C
H
I
L
L
E
R
C
H
I
L
L
E
R
Zone B
Optional Variable
Speed Pump
?
LoadMV
LoadMV
LoadMV
Temperature Sensor Locations
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T3
T1Load
Common T2
T4
Chilled
Water
Return
Pumped
Chilled
Water
Supply
Tertiary
ZonePump
T2 T3 T4T1
Circuit Setter
T1
LoadMV
LoadMV
LoadMV
T4
Tertiary Bridge
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T3
T1
Common
T2
T4
Chilled
Water
Return
Pumped
Chilled
Water
Supply
Tertiary
Zone
Pump
Tertiary Bridge
LoadMV
LoadMV
LoadMV
Temperature Sensor Locations
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T3
T1
Common T2
T4
Chilled
Water
Return
Pumped
Chilled
Water
Supply
Tertiary
ZonePump
T2 T3 T4T1
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1. Temperature of return water is unknown
2. Temperature of return water to chiller may be too high
3. Will not recognize increased supply water temperature
DISADVANTAGES
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T1
Load
MV
LoadMV
Load
MV
T4T1 T2 T3 T4
T2 Operation
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T3
Common T2
ChilledWaterReturn
PumpedChilledWaterSupply
TertiaryZonePump
1. Maintains chilled water return temperature at setpoint
2. Will not overload the chiller
ADVANTAGES
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1. No control of zone supply water temperature
2. Could lose humidity control
3. Will not recognize increased supply water temperature
DISADVANTAGES
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T1
LoadMV
LoadMV
LoadMV
T4T1 T2 T3 T4
T3 Operation
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T3
T1
Common T2
T4
Chilled
Water
Return
Pumped
Chilled
Water
Supply
Tertiary
Zone
Pump
T1 T2 T3 T4
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1. Little, if any, valve modulation unless it is set to
close on sensing supply temperature lower than
permissible in the zone
DISADVANTAGES
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T1
LoadMV
LoadMV
LoadMV
T4T1 T2 T3 T4
T4 Operation
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T3
Common T2
Chilled
Water
Return
Pumped
Chilled
Water
Supply
Tertiary
Zone
Pump
T1 T2 T3 T4
1. Maximizes coil flow rate
2. Ensures good humidity control
ADVANTAGES
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1. Temperature of return water is unknown
2. Temperature of return water to chiller may be too high3. Will not recognize increased supply water temperature
DISADVANTAGES
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No single sensor locationsatisfies all design criteria
SO
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SO........
T1
LoadMV
LoadMV
LoadMV T2 T3T1
Applying Zone Valve Controller
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T3Common T2
Chilled
Water
Return
Pumped
Chilled
Water
Supply
Tertiary
Zone
Pump
1. Temperature control to the zone (T1 sensing).
2. If T1 is satisfied, return water temperature to the chiller
plant (T2 sensing).3. Monitor secondary chilled water supply temperature
Control Algorithm
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3. Monitor secondary chilled water supply temperature
(T3 sensing) for temperature increase due to secondary
return water recirculation or temperature decrease due tochiller leaving water temperature reset.
4. Reference point for automatic reset andT (T2 - T3)
control T3 sensin .
So what?
Satisfy zone cooling requirement at themaximum possible supply temperature
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Minimize secondary flow rate
Optimize return water temperature
3-way Valve Application
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ChillerPlant
Secondary Pumps
Tertiary
Pump
Tertiary
PumpTertiary
Pump
Problems
Bypass returns cold water to chillers,
reduces system t.
Linear valve characteristics can cause
i d fl t t l d
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increased flow at part load.
Balancing required in bypass pipe andcoil-to-coil.
High cost per ton at the chiller.
T1
MVLoad
Load MV
Load MV
T2T1 T3
3-way Valve System
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Common
T2
T3
Flow
MeterSmall
By-Pass
Secondary Supply
Secondary Return
T3
Common
T3
CommonCommonT3
Zone SupplyTemperature
Chiller Supply
Temperature
Terminal
Unit Control
Valve
Terminal
Unit Balance
ValveZone
(Tertiary)
Pump
Zone 3Zone 1 Zone 2 Zone 4
T1T1 T1T1
T3GPX
Multi-zone Application
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T2 T2T2 T2
FlowMeter
T3 T3 T3Temperature
]e
Zone Bias
Control Valve
Rolairtrol
Return
Water
Temperature
C
o
m
m
o
n
3D Valves
Distribution
(Secondary)
Pumps
T3
C
h
i
l
l
e
r
C
h
i
l
l
e
r
C
h
i
l
l
e
r
Individual building temperature control
Static pressure isolation Return water temperature control
District Cooling Application
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Btu/hr totalization
Outdoor temperature reset
Independent operation
Independent pressure control
District Cooling Application
with GPX
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HVAC fluid isolation
T3
Common
T3
CommonCommonT3
Zone SupplyTemperature
Chiller Supply
Temperature
Terminal
Unit Control
Valve
Terminal
Unit Balance
ValveZone
(Tertiary)
Pump
Return
Zone 3Zone 1 Zone 2 Zone 4
T1T1 T1T1
T3GPX
VPF Application
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T2 T2T2 T2
FlowMeter
p
Zone
BalanceValve
Zone BiasControl Valve
Rolairtrol
Return
Water
Temperature
3D Valves
C
h
i
l
l
e
r
C
h
i
l
l
e
r
C
h
i
l
l
e
r
Comments?Questions?
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Questions?
Observations?
Large Chilled Water System Design Seminar
Primary-Secondary Zone Pumping Systems
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Zone A Zone B Zone C
Primary-Secondary Zone Pumping
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CHILLER
CHILLER
Return
Supply
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Shared Piping
Zone A Zone B Zone C
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CHILLE
R
CHILLE
RReturn
Supply
Shared Pipe
Zone A Zone B Zone C
Shared Piping
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CHILLE
R
CHILLE
RReturn
Supply
Shared Pipe
Zone A Zone B Zone C
1500 gpm 1500 gpm (1500 gpm)
Current = 3000Future = 4500
Flow :
Present and Future Piping
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CHILLER
CHILLER
Return
Supply
Current = 1500Future = 3000
Current = 0Future = 1500 Future Zone C
Zone A Zone B Zone C
(1500 gpm) (1500 gpm)1500 gpm @ 80
Zone A Requirements
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Return
SupplyA1 A2 A3
B1 B2 B3
Pressure drop:A to A1+B to B1
Present = 20.8
*Future = 45.2
A
B
Zone A
4500 gpm*
4500 gpm*
Table 9-1 Zone A calculations
Zone A A to A1 + B to B1 Future Flow 4500 m Present Flow 3000 mPi e Size 14 14
Pressure Dro - ft / 100 ft 2.26 1.04
E uivalent Len th
Zone A Calculations
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su l & return 1000 ft x 2 = 2000 ft 1000 ft x 2 = 2000 ft
Pressure dro 45.2 ft 20.8 ftZone ressure dro 80 ft 80 ft
Total ressure dro 125.2 ft 100.8 ftPum Selection 1500 m 1510-6G 56.4 h = 75 h * 1510-6G 45.8 h = 60 h *
Note: 15 h additional for future re uirements* Nominal horsepower motor for NOL pump
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Zone A Zone B Zone C
1500 gpm @ 80 (1500 gpm)1500 gpm @ 80
Zone B Requirements
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Return
SupplyA1 A2 A3
B1 B2 B3
Pressure drop: Zone B
AtoA1+ BtoB1 + A1toA2 + B1toB2
Present =20.8 9.0*Future = 45.2 33.4
A
B
4500 gpm* 3000 gpm*
4500 gpm* 3000 gpm*
Table 9-2 Zone B calculations
Zone B A1to A2+B1 to B2 Future Flow 3000 m Present Flow 1500 m
Pi e Size 12 12Pressure Dro - ft / 100 ft 1.67 0.45
E uivalent Len th
su l & return 1000 ft x 2 = 2000 ft 1000 ft x 2 = 2000 ft
P d 33 4 ft 9 0 ft
Zone B Calculations
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Pressure dro 33.4 ft 9.0 ft
Previous ressure dro 45.2 ft 20.8 ftZone ressure dro 80 ft 80 ft
Total ressure dro 158.6 ft 109.8 ftPum Selection 1500 m 1510-6G 71.4 h = 100 h * 1510-6G 49.6 h = 60 h *
Note: 40 additional h re uired for future re uirements
*Nominal horsepower motor for NOL pump
Zone A Zone B Zone C
1500 gpm @ 80 1500 gpm @ 80 1500 gpm @ 80
Zone C Requirements
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Return
SupplyA1 A2 A3
B1 B2 B3
Pressure drop: Zone C
AtoA1+ BtoB1 + A1toA2 + B1toB2 + A2toA3+ B2toB3
Present = 45.2 + 33.4 + 21.4
Future = Present
A
B
4500 gpm3000 gpm 1500 gpm
4500 gpm 3000 gpm 1500 gpm
Zone C (A2 to A3 + B2 to B3) Future Flow @ 1500 gpm Present Flow @ 0 gpm
Pipe Size 10Pressure Drop - ft / 100 ft 1.07Equivalent Length(supply & return) 1000 ft x 2 = 2000 ftPressure drop 21.4 ftPrevious pressure drop 78.6 ft
Zone C Calculations
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p p(A to A2, B to B2)Zone pressure drop 80 ft
Total pressure drop 180.0 ftPump Selection @ 1500 gpm 1510-6G @ 82.7 hp = 125 hp*; Note: 50 hp more
than Zone A
Zone Pumping Summary
Present Requirement Future RequirementSummary Duty Pump Standby Pump Duty Pump Standby Pump
Zone A 1 @ 75 hp 1 @ 75 hp 1 @ 75 hp 1 @ 75 hpZone B 1 @ 100 hp 1 @ 100 hp 1 @ 100 hp 1 @ 100 hp
Zone C 1 @ 125 hp 1 @ 125 hp2 @ 175 hp 2 @ 175 hp 3 @ 300 hp 3 @ 300 hp
Total 4 @ 350 hp 6 @ 600 hp* Nominal horsepower motor for NOL pump
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0 0
Zone
Pump AZone
Pump B ZonePump C
Load
FrictionLoss
Pressure Diagram - Zone Pumped
System
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0
Friction Loss
Supply Header
Friction Loss
Return Header
Supply
C C C
3000 GPM 1500 GPM
1500 GPM 1500 GPM
A
A1 A2 A3
(1500 GPM)
Primary-Secondary Equivalent
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Return
PumpController
AFDs
Ch
iller3
Ch
iller2
Ch
iller1
3000 GPM1500 GPM
A
BB1 B2 B3
Primary-Secondary pressure drop calculation:
Pi e Se ment Pressure Dro
Present, feet
Pi e Se ment Pressure Dro
Future, feet
A to A1 + B to B1 20.8 A to A1 + B to B1 45.2
A1 to A2 + B1 to B2 9 0 A1 to A2 + B1 to B2 33 4
P-S Calculations
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A1 to A2 + B1 to B2 9.0 A1 to A2 + B1 to B2 33.4
A2 to A3 + B2 to B3 DNA A2 to A3 + B2 to B3 21.4Zone B 80.0 Zone C 80.0
Total 109.8 Total 180
Distribution pump selection:
Present = 3000 gpm @ 109.8 feet, increase impeller to 13.5 for future head requirements:
2 @ VSCS 8x10x17L @ 111.0 hp 125 NOL1 @ VSCS 8x10x17L @ 111.0 hp 125 NOL, standby
Total 3 Pumps 375 NOL, Total
Future = 4500 gpm @ 180 feet:
P-S Calculations
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Future = 4500 gpm @ 180 feet:
3 @ VSCS 8x10x17L @ 114.4 hp 375 NOL1 @ VSCS 8x10x17L @ 114.4 hp 125 NOL
Total 4 Pumps 500 NOL
Comparison
Zone Pumping
Present
350 hp
Future
600 hp
P/S Pumping
Present
375 hp
Future
500 hp
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Primary-Secondary Zone
Pumping Cautions Excessive initial horsepower
Initial equipment investment
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Future considerations
Reduced Horsepower
Comments?Questions?
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Observations?
Large Chilled Water System Design Seminar
Variable Speed Sensor Selection and Location
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Supply
Pump
C t ll
Differential
Pressure
SensorCh
Ch
Ch
Direct Return Piped System
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Return
Controller
AFDs
iller3
h
iller2
h
iller1
Supply
Chi
Ch
Ch
WRONG!Single
Point
Pressure
Sensor
Single Point Pressure Sensor
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Return
Pump
ControllerAFDs
iller3
iller2
iller1
Head
90
80
50
40
70
60
1750 RPM
Constant Pressure
Design PointShut-off head
Control Curve Using Single Point
Pressure Sensor
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,FT
40
30
20
10
0200 400 600 800 1000 1200 1400 16000
Flow, gpm
(Maximum rpm)
1480 RPM
(Minimum rpm)
Single Point Pressure Sensor
in a CHW System A rise in the average water temperature
results in a net expansion of the water. This net expansion volume flows into
the compression tank, raising the
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system pressure.
The pump slows down.
What if?
CHI
CHI
CHI
Supply
P Sensor here
Zone A Zone B Zone C
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Return
I
LLER
I
LLER
I
LLER
PumpControllerAFDs
Sensor Across Mains At Pump
Whats the set point?
Its the greatest branch and distribution
piping head loss calculated at design
flow. In other wordsdesign head.
What will the flow be in each zone?
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Determined by the zone path CV
Head
90
80
50
40
70
60
Maximum rpm
Design Point
Differential Pressure Sensor
at the Pump
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,FT
30
20
10
0200 400 600 800 1000 1200 1400 16000
Flow, gpm
Minimum rpm
Variable Head Loss Ratio
P
ercentDesig
90
80
70
60
50
100 C/S, Constant Flow System Pump Head Matched toSystem at Design Flow
C/S, Variable FlowV/S, 0% Variable Hd Loss, 100% Constant Hd
V/S, 25% Variable Hd Loss, 75% Constant Hd
V/S, 50% Variable Hd Loss, 50% Constant Hd
Base
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nBHP
% Flow
40
30
20
10
0 10 1009080706050403020
V/S, 75% Variable Hd Loss, 25% Constant Hd
V/S, 100% Variable Hd Loss, 0% Constant Hd
Coil or Valve?
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25 Head
P
Supply
Variable Head Loss
Constant Head Loss
Pump
Controller
Differential
Pressure
SensorChi
Ch
Ch
Maximizing Variable Head Loss
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Return
AFDs
ller3
iller2
iller1
CH
I
CH
I
CH
I
DP Sensor
Zone 1
20 ft
Zone 2
20 ft
A B C D
Control Area
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LL
E
R
LL
E
R
LL
E
RPump
ControllerAFDs
EF
P AB+EF
20FT
P Zone 1
20FT
P BC+DE
20FT
P Zone 2
20FT
Pressure Drops in Piping (Table 11-1)
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TDH = P AB + EF + BC + DE + P ZONE 2 = 60 FT
Control Area CalculationTable 11-2 Control Area Calculation
Flow
Zone 1
Flow
Zone 2
Friction
Loss
AB+EF
Friction
Loss
Zone 1
P
Zone 1
Friction
Loss
BC+DE
Friction
Loss
Zone 2
P
Zone 2
TDH
0 gpm 600 gpm 5 0 40 20 20 20 45300 gpm 300 gpm 5 5 25 5 20 20 30
600 gpm 0 gpm 5 20 20 0 0 20 25
0 gpm 0 gpm 0 0 20 0 0 20 20
600 gpm 600 gpm 20 20 40 20 20 20 60
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What pump head is required at:
zero flow?
full flow?
less than full flow?
20
30
40
50
60
Head,FT
Lower Limit
U Li i
Control Area
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0
10
0 100 300 500 600 900 1100 1200
Flow, gpm
Upper Limit
Single Point
So What...?
Staging pumps in a closed loop HVAC
system by flow alone may not work
because of different head requirementsfor a given flow.
Wire to water pump efficiency
l l ti t t l d d d h il
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calculations at part load depend heavilyon the assumptions made about the
nature and shape of the control curve.
Single Sensor, IncludingBalance Valve Pressure Drop
Zone 1
25 ft
Zone 2
20 ft
AB (50) C
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E (10)F
D
What do you mean...?
The head loss across the coil and the
wide open valve in zone 1 is 25 feet at
full flow.
If thats true, then we need to add an
t 15 f t f h d l i th b l
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extra 15 feet of head loss in the balancevalve to insure adequate flow out to
Zone 2 when the Zone 1 valve is wide
open.
Set Point, Zone 1, 40 ft
Flow Zone 1 Flow Zone 2 Friction Loss
AB+EF
Friction Loss
BC+DE
Head Required
Zone 2
Setpoint -
Friction Loss
0 gpm 600 gpm 5 20 20 0
300 gpm 300 gpm 5 5 5 30
600 gpm 0 gpm 5 0 0 40
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Excess head means wasted energy
CH
I
LL
CH
I
LL
CH
I
LL
DP Sensor
Zone 1 Zone 2
A B C D
Sensor Location
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LL
E
R
LL
E
R
LL
E
RPump
ControllerAFDs
EF
Single Sensor in Zone 2
Flow
Zone 1
Flow
Zone 2
Friction Loss
AB+EF
Friction Loss
Zone 1
Friction Loss
BC+DEP Zone1,
Available
P Avail -
Friction Loss
Zone 1
0 m 600 m 5 0 20 40 40
300 m 300 m 5 6.25 5 25 13.75
600 m 0 m 5 25 0 20 - 5
Zone 1 requires 600 gpm at 25 ft
Zone 2 requires 600 gpm at 20 ft
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600 m 0 m 5 25 0 20 5
Inadequate head for Zone 1
Sensor in Zone 1
Flow Zone 1 Flow Zone 2 Friction Loss
AB+EF
Friction Loss
BC+DE
Head Re uired
Zone 2Setpoint -
Friction Loss
0 m 600 m 5 20 20 5
300 gpm 300 gpm 5 5 5 20
600 m 0 m 5 0 0 25
Zone 1 requires 600 gpm at 25 ft
Zone 2 requires 600 gpm at 20 ft
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600 m 0 m 5 0 0 25
Inadequate flow in Zone 2
What can we do...?In this system:
Single sensor in Zone 2 at 20 ft fails toprovide adequate flow only when
load in Zone 2 < 50% and
load in Zone 1 > 75%
Is this a predictable, recurring situation?
manual adjustment
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manual adjustment programming
Add a second sensor
CHI
LL
CHI
LL
CHI
LL
Supply
DP Sensors
Zone A Zone B Zone C
Applying Multiple Sensors
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Return
LER
LER
LER
PumpControllerAFDs
Use Multiple Sensors?
Load Similarity
Priority
Diversity
One building or several
Redundancy
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Redundancy First cost vs operating cost
The Active Zone
Zone set points do not have to be thesame.
Technologic pump controller scans all
zones often, comparing process
variable to set point in each case.
Pumps are controlled to satisfy the
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Pumps are controlled to satisfy theworst case.
What happens to the rest of the zones?
Effect of Sensor Location
Zone 1 Zone 2
A
BC
OR
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EF
D
Multiple sensors, set point across Zone 1, = 25 FT and setpoint across Zone 2 = 20 FT, (Table 11-6)
Flow
Zone
1
Flow
Zone
2
Friction Loss
AB+EF
Minimum
Reqd
P Zone 1,
P
Zone1
Available
Friction Loss
BC+DE
Minimum
Reqd
P Zone2
P
Zone 2
Available
0 600 5 0 40 20 20 20
300 300 5 6.25 25 5 5 20600 0 5 25 25 0 0 25
Multiple Sensors & Setpoints
Row 1. Sensor 2 is controlling, Zone 1 is over pumped.
Row 3. Sensor 1 is controlling, Zone 2 is over pumped.T t l h d i d
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g, p pTotal pump head required:
row 1 45 ft
row 2 30 ft
row 3 30 ft
C
H
I
L
Supply
Reverse Return Piped System
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L
L
E
R
Return
Reverse Return Systems
If all the circuits are the same length,will the pump still change speed?
Suppose a coil with a high
prequirement and another with a lower p
requirement are served by the same
reverse return piping system. OK?
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reverse return piping system. OK? If the coils are serving different sides of
the building, could we have a problem?
C
H
I
L
L
C
H
I
L
L
Zone A Zone CZone B
Tertiary Piped System
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L
E
R
L
E
R
Return
C
HI
C
HI
Supply
Zone A Zone B Zone C
Zone Piped System
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L
L
E
R
L
L
E
R
Return
Summary Give priority to the needs of the branch.
The rule of sensor location is simple and easyto apply:
If you have to use a single sensor, put it across
the critical branch.
Whats the critical branch?
Its the same one that determined the pump head.A th l i i i t t
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p p As weve seen, the analysis is more important
than the rule.
Comments?Questions?
Observations?
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Observations?
Large Chilled Water System Design Seminar
Achieving Hydronic System Balance
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Systems Approach
M
Load
Air ManagementDistribution
Verification
Control
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Source
Philosophy
Systems Approach
All components work together as team
Components interact and work as well as we
understand them
A collection of mismatched components will
not perform as expected
Owner, engineer, architect, contractor, and
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operators are part of the system too!
Hydronic Balancing
We worry about balance because:
Load calculations are approximate
Piping circuitry analysis is approximate
Control valve selection is approximateApproximations will lead to underflow andoverflow situations
Results of overflow or underflow Design Dt cannot be achieved
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Design Dt cannot be achieved
Supply temperature controller hunts (?)
Sequence of operation can be upset.
For example:
Published by
ASHRAE &
Hydraulic
Institute
Darcy-
Weisbach
Equation.
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Add 15%!
Its test, adjust & balance
Test: The system, now built, is verified in
operation to perform to the expected level.
What do we measure? temperature, flow, pressure drop, energy
consumption.
What do we test with? Can we test with what is installed?
What Is Balancing?
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Can we test with what is installed?
Can we obtain accurate readings?
What level of adjustment, and for what
purpose?
Create comfort conditions
Minimize energy consumption Prevent equipment damage
Adjust: tested in operation, the system isfound lacking and needs fine tuning.
Adjust
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q p g
How do we adjust?
Balance
Balance is often interpreted to mean 10%
of design flow.
This generalization may or may not yieldsatisfactory heat transfer required for
comfort conditions
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Redefining Balance
Evaluate System Operation
If the goal is occupant comfort, then heat
transfer becomes the key concern.
We control heat transfer as a sensible
temperature control process between controller,
control valve and coil
Analysis should account for interaction of all key
components, and how they affect the rest of the
t
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system
Balanced Hydronic Systems
All terminals receive enough flow to produce
satisfactory heat transfer (97.5% - 102.5%)
At design conditions, all terminals receive
satisfactory flow with the pump in a specifiedrange of operation
Under temperature control modulation to
match load, circuit flow does not exceeddesign flow accuracy
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design flow accuracy
Chilled Water Coil Flow vs. Heat Transfer
%
40%
60%