Large Chilled Water System

8/10/2019 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


4/314

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


8/314

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.


23/314

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




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Closed Circuit Cooler

Heat Rejecter

Water SourceHeat Pump





Water Source

Heat Pump

Water Source

Heat Pump

Water Source

Heat Pump

Water Source

Heat Pump

Buffer

Tank

( Optional )

Compression

Tank



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Comments?

Questions?Observations?


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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


79/314

Two-way Valve

Control Valve in Secondary

Primary-Secondary Pumping


80/314

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?


89/314

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



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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


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


101/314

From loads

Common

To Loads

Chiller3

Chiller2

Chiller1

Production = Distribution


102/314

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


105/314

Return

Supply

PumpController

Secondary

Pumps


Chiller3

Chiller2

FreeCooling

Primary-Secondary System


106/314

Return

Supply

PumpController

SecondaryPumps


Chiller3

Chiller2

Chiller1

Pump Horsepower Comparison


107/314

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


108/314

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!


111/314

But...

Uncertainties

Coils

Control valves Primary data

Lead times

Dealing With an Overheaded Pump


112/314

Throttle at the discharge valve

Limits on the valve

Flow balance & trim pump impeller

Required by ASHRAE/IES 90.1

Additional Concerns


113/314

Pump Protection at minimum flow

Chiller Staging and De-staging

instrumentation.

Pump Protection


114/314

Minimum recommended flow from ESP Plus = 900 gpm

Bypass Options

1. Establish a minimum flow equal to or greater than


115/314

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


116/314

6

Return

Supply

Pump

Controller

Secondary

Constant Speed

Pumps

PrimarySecondary

Common

Chiller3

Chiller2

Chiller1

2

5

T

Chiller Staging Instrumentation


117/314

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


118/314

From LoadsCommon

To Loads

Production

Secondary/PumpsChiller2

Chiller1

Flow

Swi

tches


119/314


120/314

Large Chilled Water Design Seminar

Variable Speed Pumping

Why variable speed?


121/314

y p

1. When should I use it?

2. How does it work?

3. What about variable primary flow?

Typical operating load profile


122/314

2% 3%5%

15%

20%

30%

15%

5%3%

2%

Bell & Gossett 70V

1970s


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124/314

Adjustable Frequency Drives

Rectifier section

t AC t DC


125/314

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


128/314

%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


129/314

P Sensor/Transmitter25 Ft. Head

System Curve

& V/S Control System


130/314

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


131/314

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


132/314

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


133/314

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


134/314

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


135/314

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


136/314

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




Variable Head Ratio w/

Overheading

140

150 Pump OHeaded by 150%Constant Flow, C/S Pump

(3 Way Valve)

C/S P


137/314

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


138/314

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


139/314

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


140/314

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


141/314

Return

C

HI

L

L

E

R

C

HI

L

L

E

R

C

HI

L

L

E

R

Supply

Variable Head Loss

PumpController


Parallel V/S Operation


142/314

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


143/314

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


144/314

DifferentialPressure

DifferentialTemperature

Flow

PumpController

Temperature

4-20ma

signal

Set PointTechnologic

Pump

AdjustableFrequency

3f , 60 Hz Power

(Control Agent)

Set Point+/- error


145/314

(Input Signal)Pump

Controller

q yDrive

(Controlled Device)

SystemSensor/

Transmitter


FeedbackSignal

ControlledVariable

Technologic Pump

Controller

Controls pumps and drives


146/314

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


147/314

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


148/314

(Input Signal)Pump

Controller Drive

(Controlled Device)

SystemSensor/

Transmitter


FeedbackSignal

ControlledVariable

Adjustable Frequency Drive

ConstantVoltage &F

RectifierSection

DirectCurrent

InverterSection

VariableVoltage &Frequency

PumpMotor


149/314

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


150/314

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


151/314

The Pump

Minimum Flow


152/314

Minimum Flow

Minimum Speed

Inverter Duty

Motors

Motor Couplers

Maintaining Minimum Flow120

110

100

90

100 % Speed


153/314

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


154/314

Failed Hytrel Coupler from a Variable

Speed Pump


155/314


156/314

Variable FlowThrough

The Evaporator

Variable Head Loss

Constant Differential Head Loss

Primary-Secondary System


157/314

Return

C

HI

L

L

E

R

C

HI

L

L

E

R

C

HI

L

L

E

R

Supply

PumpController


Primary-Secondary

Common Practice.


158/314

Why?

Protection. Nuisance shutdowns.

Freezing.

Costly downtime.

Variable Primary Flow

Flow Meter, optionTwo-position Control Valves


159/314

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


160/314

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


161/314

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


162/314

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


163/314

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


164/314

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.


165/314

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


166/314

, 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.


167/314

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


168/314

Minimum chiller flow

Minimum pump flow

Ganged Pumps

DPSENSOR

FLOWMETER

DPSENSOR

DPSENSOR

DPSENSOR

DPSENSOR

SIGNALTO TECH

T

FFF

SUPPLY

CHILLER CHILLERCHILLER


169/314

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.


170/314

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.


171/314

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


172/314

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


173/314

Parts. Maintenance.

Unequal size pumps.

Control issues.

Flow issues.

Premature failure, large pump at low flow.

Chiller Selection Equal size chillers.

R d d


174/314

Redundancy. Parts.

Maintenance.

Unequal size chillers.

Control issues.

Flow issues Additional equipment.


Size bypass for minimum flow of largest chiller.

Minimum building load?

Size bypass modulating valve


175/314

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.


Sequence chillers based on p or temperature

sensors.

Use accurate calibrated flow meter or p sensors


176/314

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


177/314

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


178/314

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


179/314

#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


180/314

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


181/314

Application specific.

Consider thermal storage

Operator Ability

Within operators ability?.

Commercial buildings may not have well


182/314

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


183/314

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


184/314

Additional controls the pumps. Pumps operate on flow, temperature, and

P.

Chiller P.

Sensor Calibration

Multiple sensors control:

Flow.


185/314

Flow. Temperature.

Delta p

Maintenance.

Calibration.

Summary

Evaluate all the options.

Read some articles:


186/314

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.


187/314


Primary-Secondary-Tertiary Pumping Systems


188/314

Zone A

Zone C

Primary-Secondary-Tertiary


189/314

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


190/314

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


191/314

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


RIGHT !


192/314

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


193/314

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


can be even more useful


194/314

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


195/314

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


196/314

T3

T1

Common

T2

T4

Chilled

Water

Return

Pumped

Chilled

Water

Supply

Tertiary

Zone

Pump

Tertiary Bridge

LoadMV

LoadMV

LoadMV

Temperature Sensor Locations


197/314

T3

T1

Common T2

T4

Chilled

Water

Return

Pumped

Chilled

Water

Supply

Tertiary

ZonePump

T2 T3 T4T1


198/314

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


199/314

T1

Load

MV

LoadMV

Load

MV

T4T1 T2 T3 T4

T2 Operation


200/314

T3

Common T2

ChilledWaterReturn

PumpedChilledWaterSupply

TertiaryZonePump

1. Maintains chilled water return temperature at setpoint

2. Will not overload the chiller

ADVANTAGES


201/314

1. No control of zone supply water temperature

2. Could lose humidity control

3. Will not recognize increased supply water temperature

DISADVANTAGES


202/314

T1

LoadMV

LoadMV

LoadMV

T4T1 T2 T3 T4

T3 Operation


203/314

T3

T1

Common T2

T4

Chilled

Water

Return

Pumped

Chilled

Water

Supply

Tertiary

Zone

Pump

T1 T2 T3 T4


204/314

1. Little, if any, valve modulation unless it is set to

close on sensing supply temperature lower than

permissible in the zone

DISADVANTAGES


205/314

T1

LoadMV

LoadMV

LoadMV

T4T1 T2 T3 T4

T4 Operation


206/314

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


207/314

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


208/314

No single sensor locationsatisfies all design criteria

SO


209/314

SO........

T1

LoadMV

LoadMV

LoadMV T2 T3T1

Applying Zone Valve Controller


210/314

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


211/314

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


212/314

Minimize secondary flow rate

Optimize return water temperature

3-way Valve Application


213/314

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


214/314

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


215/314

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


216/314

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


217/314

Btu/hr totalization

Outdoor temperature reset

Independent operation

Independent pressure control

District Cooling Application

with GPX


218/314

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


219/314

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?


220/314

Questions?

Observations?


Primary-Secondary Zone Pumping Systems


221/314


Primary-Secondary Zone Pumping


222/314

CHILLER

CHILLER

Return

Supply


223/314

Shared Piping



224/314

CHILLE

R

CHILLE

RReturn

Supply

Shared Pipe


Shared Piping


225/314

CHILLE

R

CHILLE

RReturn

Supply

Shared Pipe


1500 gpm 1500 gpm (1500 gpm)

Current = 3000Future = 4500

Flow :

Present and Future Piping


226/314

CHILLER

CHILLER

Return

Supply

Current = 1500Future = 3000

Current = 0Future = 1500 Future Zone C


(1500 gpm) (1500 gpm)1500 gpm @ 80

Zone A Requirements


227/314

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


228/314

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


229/314


1500 gpm @ 80 (1500 gpm)1500 gpm @ 80

Zone B Requirements


230/314

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


231/314

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


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?


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



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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



Base


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nBHP

% Flow

40

30

20

10

0 10 1009080706050403020



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



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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




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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


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 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?


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%

Large Chilled Water System

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