Flow and Energy Measurement for Hydronic Systems

Presented By: Barry Dunham, PE

Director HVAC Marketing ONICON Inc.

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Flow and Energy Measurement for Hydronic Systems

Flow and Energy Metering Presentation Why Measure Flow and Energy in Todays HVAC

Applications?? HVAC - Flow and Energy Measurement Fundamentals Technology Selection What to Consider Flow and Energy Measurement Applications

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Founded in Clearwater, FL in 1988

Shifted focus to HVAC building controls market in early 1990s

Recognized throughout the HVAC controls industry for innovation and outstanding service

Background on ONICON:

Why Measure Flow??? Whats Driving the Need to Measure Flow in Todays

HVAC Applications?

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Recent Trends in the HVAC Industry Driving the Need for Flow Measurement

ASHRAE Standards Serves as the Basis for LEED V4 Advanced Metering Credits Government Mandates, FEMP M&V Requirements Energy Service Contracts Performance Verification Required for the implementation of Complex Control -

Strategies and Plant Optimization Provides the basis for meeting Sustainability and Energy

Conservation Goals Provides the basis for Billing and Cost Allocation in Multi-

Tenant Buildings Identifies the Energy Hogs

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Why Do We Need a Flow Meter?

How does buying a flow meter save energy?

Consider the scale. The act of purchasing a scale wont

reduce your weight, but. Would you begin a weight loss

program without first establishing a baseline and having the ability to measure progress?

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Why are Engineers Specifying Flow Meters? Doesnt TAB Verify the Flows?

Flow meters are being used to substantiate the Actual Energy Savings vs. the Modeled Energy Savings.

Accurate flow measurement is essential for benchmarkingsystem performance, and flow meters play an integral role in maintaining performance over the life of the building.

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Fluid / Water Flow Measurement

Flow Measurement Fundamentals Definitions and Relationships Calibration and Accuracy Installation Requirements

Accuracy The ability of an instrument to make the measurement as referenced to a standard

Repeatability The deviation of multiple measurements of the same quantity under the same conditions. Not a measure of absolute accuracy.

Definitions and Relationships

Specified Turndown the published instrument range specified as a ratio of high measured value to low measured value

Effective Turndown the actual instrument range as related to the maximum flow of the specific application

Example: Specified Turndown of 1-30 ft/s = 30:1 Turndown. An application flow rate at 4 ft/s max, yields a 4:1 Effective Turndown

Definitions and Relationships

AccuracyA valid accuracy statement consists of three

components:

1. % uncertainty

2. Reference (% of what? Reading or rate, full scale)

3. Range over which the accuracy is specified

An accuracy statement is meaningless without all three components (if incomplete, you must assume the worst case).

Accuracy Statement Comparison

gpm@ gpm@ gpm@ gpm@ gpm@ gpm@ 1 Ft/Sec 2 Ft/Sec 4 Ft/Sec 8 Ft/Sec 10 Ft/Sec 12Ft/Sec

0.75 1.7 3.3 6.6 13 17 201 2.7 6.0 12 24 30 36

1.25 4.7 9.3 19 37 47 561.5 6.4 13 25 51 64 762 11 21 42 84 105 126

2.5 15 30 60 119 149 1793 23 46 92 184 230 276

3.5 31 62 123 246 308 3704 40 79 159 318 397 4765 62 125 250 499 624 7496 90 180 360 720 900 1,0808 156 312 624 1,248 1,560 1,87210 246 492 984 1,968 2,460 2,95212 349 698 1,396 2,792 3,490 4,18814 422 844 1,688 3,376 4,220 5,06416 551 1,102 2,204 4,408 5,510 6,61218 697 1,394 2,788 5,576 6,970 8,36420 866 1,732 3,464 6,928 8,660 10,39224 1,253 2,506 5,012 10,024 12,530 15,036

Pipe Size

HVAC Design Range

4 ft/s 8 ft/s

Velocity to GPM Conversion Chart

14Flow Measurement Fundamentals - 2014

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Pipe Sizegpm@gpm@gpm@gpm@gpm@gpm@

1 Ft/Sec2 Ft/Sec4 Ft/Sec8 Ft/Sec10 Ft/Sec12Ft/Sec

0.751.73.36.6131720

12.76.012243036

1.254.79.319374756

1.56.41325516476

211214284105126

2.5153060119149179

3234692184230276

3.53162123246308370

44079159318397476

562125250499624749

6901803607209001,080

81563126241,2481,5601,872

102464929841,9682,4602,952

123496981,3962,7923,4904,188

144228441,6883,3764,2205,064

165511,1022,2044,4085,5106,612

186971,3942,7885,5766,9708,364

208661,7323,4646,9288,66010,392

241,2532,5065,01210,02412,53015,036

363,04200000

485,64000000

608,81200000

7212,69000000

&C&"Arial,Bold"&16Ft/Sec to GPM Conversion Chart

Prepared by Allen Kesselring &D&RPage &P

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Sheet3

Accuracy Requirements The following applications are listed from Highest to Lowest in terms of accuracy typically required:

Cost Allocation, Billing ApplicationsSystem Control ApplicationsMeasurement and VerificationSystem Monitoring Applications

Calibration Method MattersThe calibration method ultimately determines the level of accuracy a flow meter can achieve. Wet calibrations are the most accurate.

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Questions to ask: Is every meter individually wet-calibrated? How is the meter calibrated? What is the calibration standard?

Calibration Standards

Apples to Apples Comparison!!

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Accuracy and Installation

After calibration, the largest contributor to the accuracy achieved by any flow meter is based on meeting the installation requirements and operating ranges of the selected meter.

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Industry standard 10 up and 5 down rule

What does it really mean?

Straight Pipe Run Requirements

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Velocity profile is distorted by pipe obstructions and direction changes.

Friction from the pipe wall conditions the velocity profile, eventually flattening the profile (based on velocity and viscosity typically found in HVAC applications).

Velocity Profile of Water in Pipes

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Velocity Profile of Water in Pipes3 Single Bend No Meter High Contrast

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Velocity Profile of Water in Pipes3 Single Bend 10D High Contrast

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Velocity Profile of Water in Pipes

10 Single Bend 7D High Contrast

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Upstream length requirement typically increases with multiple obstructions, valves, tees and pumps.

Straight Pipe Run RequirementsIndustry Standard - Reality

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Minimum upstream dimensions depend on the type of pipe obstruction.

AVOID THESE:

Control Valve

Inflowing Tees

Multiple Bends Out of Plane

Multiple Bends In Plane

IDEAL:

Straight Pipe

THESE ARE WORKABLE:

Outflowing Tees

Pipe Reduction or Enlargement

Single Bend

Straight Pipe Run Requirements

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Accuracy and Installation

Trade-offs can be made in terms of straight run vs. accuracy required when faced with real world (mechanical room) installation issues.

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Straight Run Matters!

A Flow Meter Manufacturers Dream, literally miles and miles of straight run!

Straight Run Matters!With a little planning, straight run requirements can typically be met within Central Plant systems.

Locating Meters - Trade Offs

Avoid locating meters downstream of modulating valves.

Avoid locating meters downstream of inflowing tees.

Straight Pipe Run The Real World

Real World Flow Meter Installations rarely have the straight run required by the manufacturer to achieve the published accuracy.

Example of straight pipe run actually encountered in flow meter used for billing application, two (2) diameters downstream of an isolation valve, one (1) diameter upstream of an outflowing tee.

Energy Measurement

Energy Measurement Fundamentals Equations Calibration and Accuracy

Hydronic Cooling/Heating System

Heat Load Calculation:BTU Rate = Flow Rate x Density x Specific Heat x Delta-T

BTU Measurement Accuracy Evaluation

The effect of using typical HVAC grade flow and temperature sensors into standard analog control inputs for energy measurement is widely misunderstood.

Class A RTD Information

Class A RTD Temperature Measurement Uncertainty

RTD Accuracy Comparison

Degrees C Degress F OHMS R0 + OHM - OHM Actual OHMPotential Offset

OHMs Slope

OHMS/ Deg FPotential Offset

0F

Un-Certainty in % Based on 10

Deg Delta

3 0.00 32.0 100.00 100 100.0600 99.9400 100.00 0.120 0.218 0.551 5.51%

4 2.50 36.5 100.98 100 101.0421 100.9379 100.98 0.124 0.218 0.567 5.67%

4 4.45 40.0 101.75 100 101.8087 101.7167 101.75 0.126 0.218 0.579 5.79%

5 5.00 41.0 101.96 100 102.0249 101.9364 101.96 0.127 0.218 0.583 5.83%

6 10.00 50.0 103.93 100 103.9928 103.9358 103.93 0.134 0.218 0.614 6.14%

7 15.00 59.0 105.89 100 105.9635 105.9380 105.89 0.141 0.219 0.645 6.45%

8 20.00 68.0 107.86 100 107.9371 107.9431 107.86 0.148 0.219 0.676 6.76%

9 25.00 77.0 109.84 100 109.9136 109.9511 109.84 0.155 0.219 0.707 7.07%

Advantage - BTU Measurement System with Factory Calibration!

BTU Meter, Flow Meter and Matched Temperature Sensors Specified, Purchased, and Installed as a Complete, Factory-Calibrated, NIST Traceable System (Third Party Verification)

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Basic F