chilled water system presentation

8/8/2019 Chilled Water System Presentation

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COMMERCIAL BUILDING SERVICES FLOW THINKING

Chilled Water System Presentation


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Constant Volume DistributionConstant Volume Distribution


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Air-conditioning System Components


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Constant Volume System Components


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Typical 3-way Valve Zone


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Full Load Condition


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Fully Loaded Coil

Supply water temperature 45F

Design return water temp. 55F

Coil design flow 100 GPM

Coil design pressure drop 20 FT

Load (flow x 10F x 500) 500,000 Btuh

Coil P @ design flow 20 FT Bypass flow 0 GPM

Bypass P 3-way valve closed

3-way valve pressure drop 10 FT

Pump flow and head 100 GPM @ 30 FT

Actual return water temp 55 F


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Unloaded Condition


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Unloaded Coil

Supply water temperature 45F Design return water temp. 55F


Coil design pressure drop 3-way valve closed

Load (flow x 10F x 500) 0.0 Btuh Coil P @ design flow 0 FT

Bypass flow 100 GPM

Bypass P 20 FT 3-way valve pressure drop 10 FT

Pump flow and head 100 GPM @ 30 FT

Actual return water temp 45 F


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So What?

When the load on the coil is zero, the valve is returning unusedchilled water at essentially supply temperature.

Cold return water unloads the chillers, causing them to operateinefficiently.


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Part Load Condition


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Partially Loaded Coil

Supply water temperature 45F

Design return water temp. 55F



Load (flow x 10F x 500) 250,000 Btuh Coil P @ design flow 5 FT

Bypass flow ??? GPM

Bypass P 3-way partially closed

3-way valve pressure drop 10 FT

Pump flow and head ??? GPM @ 30 FT

Actual return water temp ?? F


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125

100

75

50

25

0

% Valve Stroke25 50 75 100

%F

low

1/2 Through Coil

1/2 Through Bypass

FullF

low

ThroughCoil

FullF

low

ThroughByp

ass

3-way Valve Characteristic


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Whats Really Happening?


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Coil with 3-way Valve at Mid-position

Supply water temperature 45 F

Design return water temp. 55 F

Load (flow x 10F x 500) 250,000 Btuh


Coil flow 62.5 GPM

Coil P @ 62.5% flow 7.8 FT

Coil leaving water temp 53 F

Bypass flow 62.5 GPM

Bypass P 7.8 FT

3-way valve pressure drop 10 FT Pump flow and head 125 GPM @ 30 FT

Actual return water temp 49 F (62.5 GPM @ 53 F+62.5 GPM @ 45 F)


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Head2 = Head1(Flow2/ Flow1)2

Head2 = 20(.625/1)2

Head2 = 20(.3906 )

Head2

= 7.8


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T = Load/ Flow X 500

T = 250,000/62.5 X 500

T = 8

Therefore, LWTcoil = 45 + 8 = 53


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RWT = (Flow1

X EWT + Flow2

X LWT)/ Flow1 + 2

RWT = (62.5 X 45 + 62.5 X 53)/125

RWT = 49


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1.Low return water temperatures.2.Robs chilled water from other coils at part

load conditions.3.Increases flow in primary piping.4.Adds additional chillers on line.

5.Chiller performance is reduced.

3-way Valve System Deficiencies


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1.1

20 30 40 50 60 70 80 90 10010

1.0

0.9

0.8

0.7

0.6

0.5

KWperTon

Percent Load

Chiller Performance Curve


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Pump Sizing

Select for full chiller flow

Head must be adequate for:

Chiller evaporator

Longest circuit

Coil

Three way valve Air separator


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System Configuration

Constant Volume


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Any Questions?


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Variable Volume Constant Speed


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Primary Secondary System

Primary Includes Chillers & Primary Pump.Circuit Constant water flow through the chiller

is maintained and chilled water is

produced

Secondary Chilled water is circulated to theCircuit demand area (load) by using

Secondary pumps.

Variable Volume Constant Speed


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PRIMARY - SECONDARY


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Other Famous Names of Primary-Secondary

Primary Production Loop

Secondary Distribution Loop


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Fundamental Idea


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No Secondary Flow


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Primary = Secondary

FLOW THINKING


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Primary > Secondary

FLOW THINKING


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Primary < Secondary



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Control Valve in Secondary



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Use the flow of the largest chiller

Chiller staging at half of this flow is common

Head loss in common


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Variable flow through coilConstant flow through system

Three Way Valve

Variable flow through coilVariable flow through system

Two Way Valve

Control Valve in Secondary



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PRIMARY SECONDARY CIRCUITVariable Volume Constant Speed



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Head

F1 F2 F3

H1

H2

H3

Flow

Control Valves Change the Secondary

System Curve



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FLOW THINKING

% Flow

125

100

75

50

25

150

25 50 75 100

HDVarying differential pressureabsorbed by control valve

System resistance

TDH of pump

Pump curve

Head Absorbed by 2-way Valves



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FLOW THINKING

HP

125

100

75

50

25

150

25 50 75 100

% Design Flow

Primary Pumps = V/V

Secondary Pumps +

Constant Flow Primary Pumps, only

Pump Horsepower Comparison



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FLOW THINKING

% F low

90

80

70

60

50

40

30

2010

0 10 1009080706050403020

100

110

120

130

140

150

BaseDesignHP %

% Full Load(Design) HP

Pump Ove r-haded by 150%Constant Flow, C/S Pump

(3 Way Valve)

Constant Flow, C/S Pump

(3 Way Valve)

C/S Pump(2 Way Valve)

Pump HD Matchedto System @Design Flow

C/SPump

(2Wa

yValv

e)

Constant vs Variable Volume


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Any Questions?


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Step Function of Chillers



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Production = Distribution



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Distribution > Production



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Production > Distribution



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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 the water



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Chiller Performance Curve

1.1

20 30 40 50 60 70 80 90 10010

1.0

0.9

0.8

0.7

0.6

0.5

KWpe

rTon

Percent Load



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Check Valve in Common?



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What can we do?



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What else can we do?

Reset Supply Temperature

Lower chiller set point when mixing occurs to maintain a constant

temperature to the system.

Expect increases in cost of chiller operation at lower set point: 1-3% perdegree of reset.

Delays start of the next chiller.



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What else can we do?

Coils that are selected at higher supply temperatures will not beimpaired by small changes.

Loads that require fixed temperatures may use a small chiller toreverse the effects of mixing.



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Multiple Chillers



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60/40 Chiller Split to Help Minimize Low Part Load Operation



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0-10 30-40 60-70 90-1000

5

10

15

20

25

30

0-10 30-40 60-70 90-100

%

Time

% Load

Typical Load Profile



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Three Unequally Sized Chillers



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% Load

Time

Approaching Flow = Load


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Any Questions?AlternatePumping Methods

Comparison


T Pi Di t R t


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Two Pipe Direct Return


T Pi R R t


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Two Pipe Reverse Return



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Primary-Secondary Pumping.

Simplest to install.

Simplest to operate.

Flexible in design for present and future. Efficient to operate.

May over-pressurize near zones.


P i S d T ti


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Primary-Secondary-Tertiary



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Primary-Secondary-Tertiary Pumping.

Best piping flexibility.

Best expansion flexibility.

Provides hydraulic decoupling.

Efficient to operate.

May require added horsepower.

Requires additional pumps and piping. Increased controls complexity.


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Primary-Secondary-Tertiary Hybrid Pumping.

Low present horsepower.

Low future horsepower.

Good piping flexibility.

Good expansion flexibility.

Provides hydraulic decoupling.

May require added horsepower Requires additional pumps and piping.

Increased controls complexity.


Primary-Secondary Zone Pumping


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Primary-Secondary Zone Pumping



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Primary-Secondary Zone Pumping.

Low built out horsepower.

Low system head.

Increased control complexity.

Present horsepower total higher due to future needs.

Present pumps sized for future requirements.

Difficult to apply in retrofits projects.


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Any Questions?


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Variable Volume Variable Speed



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Why Do We Need Variable SpeedSecondary Pumps ???

For Energy Saving.

For better & optimise operation.



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How Do We Achieve This Reduction In PowerConsumption ??

By Using Variable Frequency Drive and Logic controller

with the Secondary Pumps.



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Power Comparison at Reduced Speed



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Basic Law which helps in achieving this Affinitylaw

1. Flow2 = Flow1(Speed2/ Speed1)

2. Head2 = Head1(Speed2/ Speed1)2

3. BKW2

= BKW1(Speed

2/ Speed

1)3

If Diameter of Impeller is to be trimmed then instead ofspeed the same can be used in above formulas.


Operating Cost


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0

50

100

150

200

250

300

350

400

450

50 100 150 200 250 300 350 400 450 500

Motor Horsepower

AnnualOperatingCost$1000

$0.10/kWh

p g


Variable flow system


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Head

Flow

PumpCurve

System

Curve

System Curveas two wayvalves close

Variable flow system


Energy savings offset


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Q

H

Pump

Curve

System Curve

at design flow

System Curveat part load

Increasedhead loss

Energy savings offset


Pumps in parallel


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Head

Flow

SinglePump

Pumps inParallel

SystemCurve

p p


Parallel pumping power savings


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Horsepower%

100

90

80

70

60

50

40

30

20

10

00 10 20 30 40 50 60 70 80 90 100

Flow%

Single Large Pump

Two ParallelPumps

Single ParallelPump


Theoretical Savings


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g


Establishing Efficiency Curves


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12 0

11 0

10 0

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 %

85 %80 %70 %60 %

50 %

85 %

% Speed Curves

ConstantEfficiencyCurve

% Efficiency

He

ad,

Feet

GPM


Variable Speed Efficiencies


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750

900 1150 1450 1770600

900

1150

1450

1770

600

A

B

C

D

E

4500 gpm @ 100 FT, 85.9 %


No Valve System Curve


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Flow

piping headloss curve

Distribution

PumpTDH

Overallsystem curve

Head

80

60

40

20

110

0200 400 600 800 1000 1200 1400 16000

100

Set Point

25 FT Differential Head

Maintained Across Load(Set Point)


Effect of Constant Set Point110


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Distribution

PumpT

DH

Overall system curve

Head

80

60

40

20

0200 400 600 800 1000 1200 1400 16000

Flow

100

Control curveSet point,

25 FT


Control curve


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100%

75%

50%

Flow

Head

ControlCurve

VariableHead

LossP

P1 P2


Large systems, long pipe runs


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Annual

OperatingCost

($1000/year

@

$0.10/kwh)

50

45

40

35

30

25

20

15

10

05

001000 2000 3000 4000 5000

Total Equivalent Pipe Length(feet)

SingleC/SPump,NoOverheading

Sing

leC/S

Pum

p,200

%Ove

rhea

ded

VariableSpe

edPump


Variable Head Loss Ratio


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PercentDe

signBHP

% Flow

90

80

70

60

50

40

30

20

10

0 10 1009080706050403020

100C/S, Constant Flow System Pump Head Matched to

System at Design Flow

C/S, Variable Flow

V/S, 0% Variable Hd Loss, 100% Constant Hd




V/S, 100% Variable Hd Loss, 0% Constant

Hd

Base


Variable Head Ratio w/ Overheading

150 P OH d d b 150%C Fl C/S P


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90

80

70

60

50

40

30

20

10

0 10 1009080706050403020

100110

120

130

140

150

BaseDesignHP %

% Full Load(Design) HP

Pump OHeaded by 150%Constant Flow, C/S Pump(3 Way Valve)

Constant Flow, C/S Pump

(3 Way Valve)

C/S Pump(2 Way Valve)

Pump HD Matchedto System @Design Flow

* 25/75 Means:25 % Variable HD Loss75 % Constant HD Loss

C/SPump(2

WayV

alve)

V/S,100%ConstantHD

V/S,25/7

5*

V/S,50/5

0

V/S,75/2

5

V/S,

100%V

ariab

leHD


Locations of Sensor


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Where to install the Sensor?

What type of Sensor?


Single Point Pressure Sensor


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Chillers

Primary Pumps

SecondaryPumps

Load

Balancing Valve 2 WayValve

Panel withPLC & VFD`s

Air -Separator

Com

mon

Single Point PressureSensing


Single Point Pressure Sensor


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Is Single Point Pressure Sensor Correct?

Wrong !!

Why?

-Pump is a differential pressure device.

-A single point is only influence by pressure. This is good for booster only.

-In a closed loop system, system pressure rises due to thermal expansion,

pumps will slow down.

-When static pressure decrease, pumps will speed up.

-This is self-defeating since now the pump speed is not influence by the

system load changes, but rather by system water pressure.

-Therefore, single pressure sensor are a misapplication in a closed loop

HVAC system.


Single Point Differential Pressure Sensor


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Chillers

Primary Pumps

SecondaryPumps

Load

Balancing Valve 2 WayValve


Air -Separator

Com

mon

Primary - Secondary Circuit With Variable SpeedSecondary Pumps

DPT


2 Way Valve Control


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Opening/Closing of 2- Way Valve-Signal from the sensor, installed at load

regulates the valve opening & closing.

-This way differential across 2-way valve also

changes & accordingly output signal is given to

PLC.

``

`

Temperature Sensor

Load

Output to PFU from DPT


93/119

Question:

Can we put the DPT across coilalone?


94/119

Question:

Across the pumps?


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System Control Curve


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Distribution

Pum

pTDH

Overallsystem curve

FtHd

80

60

40

20

110

0

200 400 600 800 1000 1200 1400 16000

Flow, gpm

100

Control curve

Set point,25 FT


Variable vs Constant Head Loss


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The Active Zone


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Zone set points do not have to be the same.

Pump controller scans all zones often, comparing processvariable to set point in each case.

Pumps are controlled to satisfy the worst case.

What happens to the rest of the zones?


Basic Concept


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PFU

PMU

4 20 mA

Set Value

From FieldSensor (DPT)

PFU Pump Functional Unit

PMU Pump Management Unit

Output

To

VFD/Pump


Different Sensor Signal To Common PFU Panel

Multi Point Differential Pressure Sensor


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ChillersSecondary

Pumps

Balancing Valve

DPTDPT

Co

mmon


Load

Different Sensor Signal To Common PFU Panel


POSSIBILITY OF MULTIPLE PROCESS



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PFU

PMU

Set Value

Multiple Process SignalsFrom Field Sensors

POSSIBILITY OF MULTIPLE PROCESSSIGNALS FROM DIFFERENT ZONES

All zones can have different set values

Module

VFD

VFD


POSSIBILITY OF MULTIPLE PROCESS



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PFU

PMU

Set ValueMultiple Process SignalsFrom Field Sensors

POSSIBILITY OF MULTIPLE PROCESSSIGNALS FROM DIFFERENT ZONES

All zones can havedifferent set values

SignalComparator

VFD

VFD

SignalComparator

4 20 mA Sig


HVAC Control System


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DPT Signal Comparator


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HVAC Control System

DPT Si l C t


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DPT Signal Comparator

Benefits

1) We are able to supply VFD systems with multiple inputs signals ranges to compete

with our competitors.

2) We are able to use Grundfos PFU 2000 as the main processor to control the full systemoperations.

3) We will be minimising outsourcing or external controller in order to serve the HVAC

market.

4) The MM allows us to integrate into the system multiple sensor control at a more cost

effective price.


HVAC System


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Other Types of

Systems


DPT

Separate System for Each Zone


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Chillers

Primary Pumps

BalancingValve

SecondaryPumps

Air -Separator

ExpansionTank

Load

Panel with

PLC & VFD`s

Commo

n

DPT

2 WayValve

DPT


Systems In Multi - Zones

Separate System for Each Zone


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Systems In Multi Zones

Two options:

1. Separate Systems can be used fordifferent zones. So each zone willhave its own sensor.

2. Signal from different zone sensors isgiven to the common PFU and most

deviated signal, from the set point, isgiven as output.


DPTVFD pumps For Each Zone

Tertiary Pumping System


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Chillers

Primary Pumps

BalancingValve

Air -Separator

ExpansionTank

Load

Commo

n

DPT

2 WayValve

DPT

E-pumpsE-pumps

SecondaryPump


Reverse Return Pumping

Load


110/119

Load

Air -Separator

Chillers

PrimaryPumps

SecondaryPumps

Balancing Valve


Common

DPT


Reverse Return Pumping


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Benefits :

1) Equalize the pressure drops of each zone.

2) Selections of the sensor becomes easier.

3) If load are similar or symmetrical, 1 centrally located sensor

is adequate.

4) As in direct return system, multiple sensor can still provide a

benefit to the end user.



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Type of VFD Systems


Possible Options of Variable Speed panels


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Possible Options of Variable Speed panels

Type ME - Multiple Pumps &Multiple VFDs.

Type MF - Common VFD for MultiplePumps.


System with Multi Pumps & Multi VFDs


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Signal from FieldSensor(s) (DPT)

Panel with

PFU & PMU

VFD - 1 VFD - 2

Secondary Pumps


System with Common VFD for All Pumps


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Signal from Field Sensor(s) (DPT)

VFD

Panel with

PFU & PMU

Secondary Pumps

System with Common VFD for All Pumps


APPROVAL FROM INTERNATIONALAGENCIES


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AGENCIES

Approval from CE, U/LConforms to - Electromagnetic compatibility

(89/336/EEC) to standard EN 50 081 1 and EN 50082 2 and Electrical equipment design 73/23/EECstandard to EN 60 204-1.


Single PMU For Control of 8 Zones/Pumps


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PFU

PMU


PFU




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PFU

PMU

S g e U o Co t o o 8 o es u ps

PFUPFU PFU


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The End

chilled water system presentation

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