© Belimo University 2011, All Rights Reserved Enhancing Sustainability Advantages of pressure...

© Belimo University 2011, All Rights Reserved

Enhancing Sustainability Advantages of pressure independent control valves;basic commissioning of Belimo PI valves.

Enhancing Sustainability

First, an analogy between air systems and hydronic systems.

Why are there no more VAV pressure dependent air systems?


Air Handling Unit

Return Duct

VVT Boxes

Supply Duct

Bypass Duct

SpaceTemp

Balancing Damper

Pressure Dependent VVT System

How many Pressure Dependent VVT systems have you seen lately?


Air Handling Unit

Return Duct

VVT Boxes

Supply Duct

Bypass Duct

SpaceTemp

Balancing Damper

Pressure Dependent VVT System

Part Load Performance:•Unable to respond to flow variation due to changing pressure conditions.•Unstable control – system is “oversized”.•Occupant comfort and energy efficiency are compromised.•Spaces too cold (or hot).


Temp. Control

Air Flow

ControllerAir Flow

Measurement Device

Pressure Independent VAV Box

Water Flow Measurement Device

Water Flow

Controller

From Temp. ControlPressure Independent Control Valve

•Stable control – system is “rightsized”.

Part Load Performance:•Flow is controlled under all pressure conditions.

•Occupant comfort and energy efficiency are improved.•Spaces at or near design.

A PI Control Valve….

Is a 2-way control valve that supplies a precise flow at any given control signal…

Regardless of pressure variations in a system.

It is not just a control valve and flow limiting circuit setter in the same assembly!

Note: Automatic or manual balance valves should NOT be used with PI valves. If they are already installed they should be set WIDE OPEN.

What is a pressure independent control valve?

Pressure Independent Control Valve

Flow rate through equal % globe valve as a function of differential pressure (Cv = 1.9).

Pressure Dependent Control Valve

Flow rate through PI Control Valve as a function of differential pressure (3 GPM valve plotted). Equal % characteristic.

Pressure Independent Control Valve

Equal % Valve Characteristic100

0 40 60 80 100

20

40

60

80

10

30

50

70

90

10 20 30 50 70 90

Signal (%)

Coi

l Ene

rgy

Out

put

(%)

Resulting Energy Output of Coil

Energy Characteristic of

Coil

Flow Characteristic of Equal % Control Valve

ASHRAE 2008 HVAC Systems and Equipment Handbook pg. 46.8

Advantages

SAT Setpoint Change Globe Valve Water Flow

The Pressure Dependent Valve loses authorityat part load. In effect, it becomes “Oversized”

•Iowa Energy Center Pressure Independent Valves Study•Chilled Water Closed Loop Test

PICCV Valve Water Flow

Globe Valve

PI Control Valve

Energy saving potential

Advantages


Advantages

Totalized Flow over 24 Hrs

Globe Valve = 358.7 gallons

PI Control Valve = 283.6 gallons

Note: The over-flow and under-flow cycling of this control valve results in a net over-flow condition!


Advantages

Globe = 358.7 gallonsPI Control Valve = 283.6 gallons

Pump Affinity Laws

HP = Horse PowerGPM = Flow in Gallons/Minute

3

2

1

2

1

GPM

GPM

HP

HP

Globe Valve

PI Control Valve

A 26.5% increase in flow results in twice the horsepower requirements from the pump.

Pressure Differential SensorSetpoint = 10 psid

Chiller200 tonsVFD-Pump

Coil #40 - 200 gpm

10ft H2O (4 psid)

VFD-Pump

Chiller200 tons

Pressure Dependent Control

ValvesDesign: 400 Ton / 800 GPM CHW

System @ 12˚ΔT

40 psid

30 psid

20 psid

10 psid4 psid2 psid

Coil #30 - 200 gpm

10ft H2O (4 psid)

Coil #2 0 - 200 gpm

10ft H2O (4 psid)

Coil #10 - 200 gpm

10ft H2O (4 psid)

4 psid12 psid

4 psid22 psid

4 psid32 psid

T

24TonsGPM

For a given load, flow and ΔT are inversely proportionate. As flow increases, ΔT drops.


Advantages

T12

24TonsGPM 800

2TonsGPM 800

Tons2

GPM 800

400Tons

Pressure Differential Sensor


Coil #40 - 200 gpm

Coil #3 0 - 200 gpm

Coil #1 0 - 200 gpm

Coil #2 0 - 200 gpm

VFD-Pump

Chiller200 tons


Valves

Design: 400 Ton CHW System @

12˚ΔT

CHWS

Coil #40 - 200 gpm

Coil #3 0 - 200 gpm

Coil #1 0 - 200 gpm

Coil #20 - 200 gpm

CHWR

180 Ton Load(45%)

42˚ (12˚ΔT)

360 GPM Loop Flow

54˚

Advantages


Valves

•Hold the load constant and vary the flow.


12˚ΔT

CHWS

Coil #40 - 200 gpm

Coil #3 0 - 200 gpm

Coil #1 0 - 200 gpm

Coil #2 0 - 200 gpm

CHWR

180 Ton Load(45%)

42˚ (10.9˚ΔT)

396 GPM Loop Flow (+10%)

52.9˚

Advantages


Valves


12˚ΔT

CHWS

Coil #40 - 200 gpm

Coil #3 0 - 200 gpm

Coil #1 0 - 200 gpm

Coil #2 0 - 200 gpm

CHWR

180 Ton Load(45%)

42˚ (10.4˚ΔT)


52.4˚

Advantages


ValvesAn increase in flow results in:

•Lower return temperature.

•Reduced ΔT.

•Increased pumping power.


12˚ΔT

Pressure Differential Sensor

Chiller200 tons

Coil #40 - 200 gpm

Coil #3 0 - 200 gpm

Coil #1 0 - 200 gpm

Coil #2 0 - 200 gpm

Chiller200 tons


Valves


12˚ΔT

With a 15% overflowΔT Reduction goesFrom 12°F (Design)To 10.4°F (Actual)

A reduction of 13%.

With a 10% overflowΔT Reduction goesFrom 12°F (Design)To 10.9°F (Actual)A reduction of 9%.


VFD-Pump

Chiller200 tons

180 Ton Load(45%)

42˚ (12˚ΔT)

360 GPM Loop Flow

54˚CHWS CHWR

KW=1.0k 90% Load

Advantages


Valves

•Hold the load constant and vary the flow.


12˚ΔT

Arbitrary Value


VFD-Pump

Chiller200 tons

180 Ton Load(45%)

42˚ (10.9˚ΔT)


52.9˚CHWS CHWR

KW=1.33k 90% Load

Advantages


Valves

An increase in flow results in:•Lower return temperature.•Reduced ΔT.•Increased pumping power.

(396GPM/360GPM)3 = 1.33 (33% increase in

pump power!)


VFD-Pump

Chiller200 tons

180 Ton Load(45%)

42˚ (10.4˚ΔT)


52.4˚CHWS CHWR

Chiller200 tons

KW=0.76k 45% Load

KW=0.76k

Advantages

45% Load


Valves

Also, a chiller receiving cold return water can’t load up!


12˚ΔT

(414GPM/360GPM)3 = 1.52 (52% increase in

pump power!)

An additional pump and chiller were started

to meet the flow demand, not cooling

demand!

Two Solutions for Today’s Hydronic Systems

Belimo PI Valves

PICCV

½” – 2”

0.5 GPM – 100 GPM

ePIV

2 ½” – 6”

105 GPM – 713 GPM

Belimo Pressure Independent Valves Commissioning

PICCV(Equal %)

ePIV(Equal % or Linear; factory or field selectable)

Water exits valve

Pressure is P3 (low)

Water enters valve

Pressure is P1 (high)

Belimo PI Valves

Water passes through regulator Pressure is P2 (intermediate)

Ports sense pressure drop and transfer it below regulator

Low pressure pulls regulator down, against the spring force

PICCV

DDC Controls

AI AO

Process Piping

PICCV Process Flow Diagram

PICCV

Process Piping

AO AI

Control Signal (2-10 vdc (default)/vdc Variable)

Valve Position Feedback (2-10 vdc (default)/vdc

Variable)

Note: Selection is made with PC Tool and ZTH-

GEN/ZTH-PICCV.

Min/Max actuator stroke %

programming per

application design flow.

Internal Mechanical ΔP

Regulator

Equal % Characterized Ball

Valve

Valve Stem and Coupler

Belimo MFT Actuator

P2P3

Note: Shown for functional purposes only. Ancilliary

piping, mechanical regulator and ball valve

are machined into common valve body.

Non-Spring ReturnSpring Return

•Magnetic Flow Sensor •Smart Actuator

•LGCCV Valve•Flow Feedback and•Control Signal

Belimo ePIV

• Measures changes to the induced voltage of a conductive fluid through a controlled magnetic field.

• No moving parts or openings to clog or jam.

• No maintenance.

Magnetic Flow Sensor

Actuator/Flow Tolerances

Controller starts to control if delta "flow actual value" and "flow set value" > 5% (50% of the Flow tolerance)Controller stops to control if delta "flow actual value" and "flow set value" < 1% (10% of the Flow tolerance)

ExampleControl Signal Y = 100GPM (stable no changes)

If the measured Flow is higher then 105GPM Actuator will correct until measured Flow is 101GPM.

If the measured Flow is lower then 95GPM Actuator will correct until measured Flow is 99GPM.

Flow Accuracy +/- 6% of Vnom

Signal Conditioning

(Linear or Equal % Scaling)

Selectable

Internal Control Algorithm

(PV=Input from Flow Sensor)

(SP=Flow Setpoint from DDC)

(CV=Output to Actuator for Valve Positioning)

(FB=Flow Feedback to DDC)

DDC Controls

AI AO

(PV)Velocity to

Flow Conversion

Magnetic Flow Sensor (External

to ePIV Controller)

4-20 milliamp

Actuator (Integral to ePIV Controller)

(CV)

LG-CCV

Process Piping

ePIV Process Flow/Logic Diagram

ePIV

Process Piping

AO AI

Control Signal (2-10 vdc (default)/vdc Variable)

Flow Feedback (2-10 vdc (default)/vdc Variable)

Flow SetpointFlow Feedback

Note: Selection is made with PC Tool v3.5 and higher and ZTH-GEN.

(Release code required)

Closed Loop Control

Valve Stem and Coupler

• 5 straight pipe diameters before the flow sensor

• no straight pipe requirement on the outlet of the valve

STRAIGHT INLET LENGTHS

•2-1/2” ePIV = 12.5” 4” ePIV = 20” 6” ePIV = 30”

•3” ePIV = 15” 5” ePIV = 25

Installation Considerations

Actuator must be kept above horizontal!

Installation Considerations

• Cost effective flow sensor technology combined with Belimo’s industry leading intelligent actuators and proven characterized valve technology

• Both non-spring and electronic fail-safe proportional models

• Provides all the benefits of PI valves (accurate flow control, improved efficiency at part load by reduced pumping power, improved waterside ΔT)

• Reduced cost, less weight, less raw materials, more sustainable!

• True flow measurement, available to DDC system through feedback wire

• Glycol concentration up 50% has no effect on flow measurement

• Can be configured for either linear or equal percentage flow characteristic with a simple program change.

Introducing – the ePIVelectronic Pressure Independent Valve

ZTH-GEN

Field adjustable programming tool allows:

•PICCV

•Control/feedback signal

•Custom flows/adjust flows

•Many other parameter adjustments

• ePIV

•Control/feedback signal

•Custom flows/bias adjustment

•Flow coefficient

•Equal % or linear setting

•Many other parameter adjustments

Belimo Field Programming Tool

No external power needed; no battery; powered by actuator 24 vac! Just plug it into actuator.

• Control/Feedback Signal Voltage

– 2-10 VDC– 0-10 VDC– User selected

• Flow Characteristic*

– Equal Percentage– Linear

• Maximum (Design) Flow

• Bias Adjustment

Belimo PC Tool ePIV adjustments (PC Tool v3.5 and above)

Additional P/T PORT for verification of 5 psi (11.5 ft H20) minimum differential across the PI Valve.

Commissioning

Minimum ΔP across valve must be verified with PI valve COMMANDED by DDC (or by programming tool) to design

flow, not manually positioned!

CommissioningStep 1: Ensure all strainers are clean and bypass valves are closed.

Step 2: Command via DDC all PI valves to design flow. (Diversity assumed at 100%.)

Step 3: Set distribution pump(s) to elevated speed by commanding ΔP setpoint or pump speed directly.

Step 4: Find the “critical zone” (ie. the PI valve that has the least ΔP).

Step 5: Increase or decrease pump speed/ΔP setpoint until critical zone has just over 5 psid (11.5 ft H20). The resulting ΔP at the system sensor will be the optimum system ΔP setpoint.

Step 6: Verify total system flow is at design at main flow station (or by other method).

Step 7: If flow is not within +/- 10% of design, start checking valves at terminal level, starting with largest valve(s) first (voltage, control signal, strainer, etc.)

Commissioning

• Belimo PI valves do NOT require that the entire system be placed in full design flow. Each PI valve flow can be verified individually with the rest of the system under normal control.

1) Command valve assembly to design.2) Verify at least 5 psid across PI valve

assembly.3) Verify coil flow as per usual method (coil ΔP

method, etc.)

Link for PI valve commissioning document:

www.piccv.com/pdf/PICCV_Application_Bulletin.pdf

Questions?

© Belimo University 2011, All Rights Reserved Enhancing Sustainability Advantages of pressure...

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