HVAC Systems and Airside Economizers - Heating and Air … · 2020-01-15 · a Trane Engineers...

a Trane Engineers Newsletter Live satellite broadcastHVAC Systems and Airside Economizers • 3 May 2006

© 2006 American Standard All rights reserved

Trane, in proposing these system design and application concepts, assumes no responsibility for the performance or desirability of any resulting system design. Design of the HVAC system is the prerogative and responsibility of the engineering professional.

1


HVAC Systems and Airside Economizers

anEngineers Newsletter Live telecast

“Trane” is a Registered Provider with The American Instituteof Architects Continuing Education Systems. Credit earned on completion of this program will be reported to CES Records for AIA members. Certificates of Completion for non-AIA members available on request.

This program is registered with the AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, ordealing in any material or product.Questions related to specific materials,methods, and services will be addressedat the conclusion of this presentation.

© 2006

Am

erican Standard Inc.




2

© 2006

Am

erican Standard A

ll rights reserved

Copyrighted MaterialsThis presentation is protected byU.S. and international copyright laws. Reproduction, distribution, display, and use of the presentation without written permission of Trane or American Standard is prohibited.


© 2006

Am

erican Standard A

ll rights reserved

AIA continuing educationLearning ObjectivesParticipants will learn the following about airside economizers:

ASHRAE/IESNA Standard 90.1-2004 requirements

How issues, such as building pressurization, affect economizer operation

Ways to control airside economizer systems based on HVAC system type and location




3

© 2006

Am

erican Standard A

ll rights reserved

airside economizersToday’s Topics What an airside economizer is

Reasons and exceptions for use

Types of control

Performance in constant- vs. variable-air-volume systems

Implementation in different systems

Application considerations

© 2006

Am

erican Standard A

ll rights reservedToday’s Presenters

Brian Fiegenmanager, applicationsengineering

Dennis Stankestaff applicationsengineer

John Murphysr applicationsengineer




4


What Is an Airside Economizer?

HVAC systems andairside economizers

© 2006

Am

erican Standard A

ll rights reserved

definitions Airside Economizer“1. Device that, on proper variablesensing, initiates control signals oractions to conserve energy …

“2. Control system that reducesthe mechanical heating and cooling requirement … ”

ASHRAE Terminologyof Heating, Ventilation,Air Conditioning & Refrigeration




5

© 2006

Am

erican Standard A

ll rights reserved

definitionsAirside Economizer“A duct-and-damper arrangement and automatic control system that togetherallow a cooling system to supply outdoorair to reduce or eliminate the need for mechanical cooling during mild orcold weather”

ASHRAE/IESNAStandard 90.1-2004

SAOA

RA

RL

space

T

Single Zone, Constant Air Volume (CAV)©

2006Am

erican Standard A

ll rights reserved

Supply-air temperaturevaries to match cooling load




6

© 2006

Am

erican Standard A

ll rights reserved

0

heating mechanical cooling

OA

inta

ke f

low

, %

OA temperaturecold hot

100

min outdoor air

CAV systemOperating Modes

heatingcapacity

© 2006

Am

erican Standard A

ll rights reserved

CAV system without economizerOperating Modes

0

heating mechanical cooling

OA

inta

ke f

low

, %


100

min

coolingcapacity

outdoor air




7

© 2006

Am

erican Standard A

ll rights reserved

CAV system with economizerOperating Modes

0

heatingmodulated

econ

outdoorair

OA

inta

ke f

low

, %


100

min mech clgcapacity

© 2006

Am

erican Standard A

ll rights reserved


0

heatingintegrated

econ

outdoorair

modulatedecon

OA

inta

ke f

low

, %


100

min

mech clgcapacity




8

© 2006

Am

erican Standard A

ll rights reserved


0

mechcoolingheating

integratedecon

outdoorair

modulatedecon

OA

inta

ke f

low

, %


100

min

mech clgcapacity


mechanical coolingmin OA

heatingmin OA

modulatedeconomizermin to100% OA

integratedeconomizer100% OA

high-limit shutoff

© 2006

Am

erican Standard A

ll rights reserved




9


Why Use anAirside Economizer?

HVAC systems and airside economizers

© 2006

Am

erican Standard A

ll rights reserved

airside economizerWhy Use It?

Comply with ASHRAE 90.1-2004, Section 6.5.1 …or local energy code




10

1a

2a

3a

4a

7a

2b3b

3c

*Alaska = Zones 7, 8Hawaii = Zone 1a

U.S. climate zones*

4c6b

7b

5b5a6a

7 very cold8 subarctic

5 cool6 cold

3 warm4 mixed

1 very hot2 hot

cmarine

bdry

amoist

© 2006

Am

erican Standard A

ll rights reserved

warm,humid

4b

© 2006

Am

erican Standard A

ll rights reserved

6

6

6

77

Halifax

8

Vancouver

Prince George

Ft. Nelson

Whitehorse

ReginaWinnipeg

St. John’s

Inuvik

Ft. Smith

Calgary

Saskatoon Kapuskasing

Montreal

Goose Bay

Toronto

8

8 8

57

5

7

6777

7Kamloops

Canadaclimate zone examples

Climate zones of citieslisted in Table B-2,ASHRAE 90.1-2004

7 very cold

8 subarctic

5 cool

6 cold

Québec




11

© 2006

Am

erican Standard A

ll rights reserved

11

1

43Mexico City

Monterrey

Tampico

Guadalajara

Veracruz

Mérida

3

Mexicoclimate zone examples

Climate zones of citieslisted in Table B-3, ASHRAE 90.1-2004

3 warm

4 mixed

1 very hot

2 hot

4b

cmarine

bdry

amoist

© 2006

Am

erican Standard A

ll rights reserved

System 65,000 Btu/h?Economizer required

System 135,000 Btu/h?Economizer required

EconomizerNOT required

Std 90.1’s economizer requirementsException (a)




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© 2006

Am

erican Standard A

ll rights reserved

airside economizer useStd 90.1’s Exceptions(a) Individual fan-cooling units with

less-than-minimum capacities installed in specific climate zones

(b) Systems with gas-phase outdoor air cleaningto meet ASHRAE Standard 62

(c) Systems with > 25% of supply airserving spaces humidified above35°F DP for process needs

(d) Systems with condenser heat recovery

© 2006

Am

erican Standard A

ll rights reserved

airside economizer useStd 90.1’s Exceptions(f) Residential space systems with capacities

< 5× limit in Exception (a)

(f) Space sensible cooling load transmission+ infiltration load at 60°F

(g) Systems that operate < 20 hr/wk

(h) Supermarket applications, where outdoor air for cooling affects open refrigerated cases

(i) Systems with high mechanical cooling efficiency ( Table 6.3.2 requirements)




13

© 2006

Am

erican Standard A

ll rights reserved


Comply with ASHRAE 90.1-2004,Section 6.5.1 …or local energy code

Reduce operating costs

© 2006

Am

erican Standard A

ll rights reserved

airside economizer (Columbus)HVAC Energy Savings

base VAV CAV75

80

85

90

95

100

HV

AC

en

erg

y co

nsu

mp

tion

,%

of

bas

e




14

© 2006

Am

erican Standard A

ll rights reserved

airside economizer (Cincinnati)HVAC Energy Savings

CAVVAVbase75

80

85

90

95

100H

VA

C e

ner

gy

con

sum

pti

on,

% o

f b

ase

© 2006

Am

erican Standard A

ll rights reserved


Comply with ASHRAE 90.1-2004,Section 6.5.1 …or local energy code

Reduce operating costs

Earn LEED-NC v2.2 certification EA Prerequisite 2: Must comply

with ASHRAE 90.1-2004 EA Credit 1:

Optimize energy cost




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EconomizerControl Types


Disable econ Enable econ(up to 100% OA) (minimum OA)

Control type when OA is: when OA is:

Fixed dry bulb Warmer than Cooler thanfixed setting fixed setting

Differential dry bulb Warmer than RA Cooler than RA

Fixed enthalpy Higher thermal Lower thermalenergy than fixed energy than fixedsetting setting

Electronic enthalpy Above fixed DB Below fixed DBvs. DP curve vs. DP curve

Differential enthalpy Higher thermal Lower thermal(comparative enthalpy) energy than RA energy than RA

Dew point & dry bulb Warmer or wetter Cooler and drier(fixed DB with than fixed DB,DP than fixed DB,DPDP lockout) settings settings

Allowed Types of Economizer Control©

2006Am

erican Standard A

ll rights reserved




16

humidity ratio, grains/lb of dry air

dry-bulb temperature, °F

© 2006

Am

erican Standard A

ll rights reserved

wet-bulb temperature, °F

minimumOA intake

high-limitshutoff

econOFF

econOFF

economizerON

economizer control type:Fixed Dry Bulb

4b

cmarine

bdry

amoist

© 2006

Am

erican Standard A

ll rights reserved

Prescribed High-Limit Settingsfor economizer shutoff

For Fixed DB,OA > 75°F






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© 2006

Am

erican Standard A

ll rights reserved




minimumOA intake

econOFF

econOFF

high-limit shutoff75°F DB

economizerON

55°F

missed opportunities:Fixed Dry Bulb

possible increasedcooling tons

© 2006

Am

erican Standard A

ll rights reserved

economizer control type:Fixed Enthalpy



dry-bulb temperature, °FeconOFF

economizerON

high-limit shutoff28 Btu/lb

minimumOA intake




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© 2006

Am

erican Standard A

ll rights reserved

missed opportunities:Fixed Enthalpy




high-limit shutoff28 Btu/lb

minimumOA intake

55°F

75°F

economizerON

possible missed CVeconomizer hours





© 2006

Am

erican Standard A

ll rights reserved

econOFF

minimumOA intake

economizer control type:Electronic Enthalpy

high-limit shutoffcurve “A”

economizerON




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© 2006

Am

erican Standard A

ll rights reserved

econOFF

minimumOA intake

high-limit shutoffcurve “A”

missed opportunities:Electronic Enthalpy

75°F

55°F

missedeconomizerhours

economizerON


© 2006

Am

erican Standard A

ll rights reserved




minimumOA intake

high-limitshutoff range

economizer control type:Differential Enthalpy

economizerON




20

© 2006

Am

erican Standard A

ll rights reserved




minimumOA intake

high-limitshutoff range(hOA > hRA)

missed opportunities:Differential Enthalpy

75°F

55°F

economizerON

© 2006

Am

erican Standard A

ll rights reserved




minimumOA intake

high-limitshutoff55°F DP OA

high-limitshutoff75°F DB OA

economizer control type:Dew-Point and Dry-Bulb Temperatures

economizerON




21

© 2006

Am

erican Standard A

ll rights reserved




minimumOA intake

missed opportunities:Dew-Point and Dry-Bulb Temperatures

high-limitshutoff55°F DP OA

55°F

possible missedeconomizer hours

high-limitshutoff75°F DB OA

economizerON

cmarine

bdry

amoist

Limitations on Economizer Control Types©

2006Am

erican Standard A

ll rights reserved

No fixedenthalpy

Any control type

No differentialdry bulb




22

© 2006

Am

erican Standard A

ll rights reserved

economizer controlHigh-Limit Shutoff It’s an enable/disable point,

prescribed by control type and climate (see Table 6.5.1.1.3B)

“Right” limit setting should yield largest energy-use reduction

If analysis shows a “better” setting: Ask for a variance, or Use Energy Cost Budget Method

(Section 11)

© 2006

Am

erican Standard A

ll rights reserved

economizer controlIntegrated Economizer Extends economizer hours to save

more cooling energy

Must use everywhere—except almost anywhere

“Economizer systems shall be integrated with the mechanical cooling system and be capable of providing partial cooling even when additional mechanical cooling is required to meet the remainder of the cooling load”

ASHRAE/IESNA Std 90.1-2004, Section 6.5.1.3




23

cmarine

bdry

amoist

Integrated Economizer Exceptions

© 2006

Am

erican Standard A

ll rights reserved

DX systems that reduce OA to prevent frosting

Small DX systems with capacities < 65,000 Btu/h

Any system in most climates

integratedeconomizerrequired

© 2006

Am

erican Standard A

ll rights reserved

economizer controlIntegrated Economizer Use in chilled water systems whenever

possible—even if not required

Use with care in built-up DX systemsLow-load operation can lead to: Very cold coil temperatures and frosting Compressor flooding and excessive

cycling, and possible premature failure Out-of-control space relative humidity




24

© 2006

Am

erican Standard A

ll rights reserved

CAV-system operating modesIntegrated Economizer

0

mechcoolingheating

integratedecon

modulatedecon

OA

inta

ke f

low

, %


100

min

high-limitshutoff

outdoor air

© 2006

Am

erican Standard A

ll rights reserved

CAV-system operating modesNon-Integrated Economizer

0

heatingmechanical

cooling

outdoorair

modulatedecon

OA

inta

ke f

low

, %


100

min

mech clgcapacity

low-limitenable




25


Performance in a Constant-Volume System


© 2006

Am

erican Standard A

ll rights reservedEconomizer Performance Compare:

Economizer control types High-limit shutoff settings

Assess impact on: Energy use Space humidity




26

© 2006

Am

erican Standard A

ll rights reserved

Building Analysis ToolsTRACE™ 700HVAC load design and analysis software

Comprehensive energy andeconomic analysis for virtuallyany building

Also tracks space humiditylevels

© 2006

Am

erican Standard A

ll rights reserved

TRACE™ 700Space Humidity Profile




27

5a

cmarine

bdry

amoist

warm,humid

Retail storeConstant-volume system

Office buildingVAV system

Columbus, Ohio

SA

OA

RA

EA

space

© 2006

Am

erican Standard A

ll rights reserved

T

High-limit shutoff:

55°F 70°F 65°F 75°F

single-zone CAV system

economizer control type:Fixed Dry Bulb

MA




28

© 2006

Am

erican Standard A

ll rights reserved

CAV system (Columbus)Energy: Fixed Dry Bulb

8%

15%13%

75

80

85

90

95

100

HV

AC

en

erg

y co

nsu

mp

tion

,%

of

bas

e

none 55°F 65°F 70°F 75°Fhigh-limit shutoff setting (fixed DB)

13%

180

160

140

120

100

80

60

40

20

0


11030 40 50 60 70 80 10090dry-bulb temperature, °F

85

80

75

60

5550

4540

3530


OA

RA

70°F high-limitshutoff setting

75°F high-limit shutoff setting

MA

SA

© 2006

Am

erican Standard A

ll rights reserved

*Single-zone CAV system: Mild, rainy day in Columbus, Ohio

fixed dry bulb:Example at Part Load*




29

© 2006

Am

erican Standard A

ll rights reserved

CAV system (Columbus)Humidity: Fixed Dry Bulb

0

50

100

150

200

250h

ours

wit

h s

pac

e R

H >

58

% 206

nonehigh-limit shutoff setting (fixed DB)

206 208228218

55°F 65°F 70°F 75°F

180

160

140

120

100

80

60

40

20

0



85

80

75

70

65

60

5550

4540

3530


OA

RA

MA

SA

RASA

70°F high-limitshutoff setting


© 2006

Am

erican Standard A

ll rights reserved


fixed dry bulb:Example at Part Load*




30

© 2006

Am

erican Standard A

ll rights reserved

CAV system (Columbus)Energy: DP Lockout

8%

13%15%

13% 14%

HV

AC

en

erg

y co

nsu

mp

tion

,%

of

bas

e

75

80

85

90

95

100


75°F DB,55°F DP

© 2006

Am

erican Standard A

ll rights reserved

CAV system (Columbus)Humidity: DP Lockout

hou

rs w

ith

sp

ace

RH

> 5

8%

0

50

100

150

200

250206 206 208

228218 206


75°F DB,55°F DP




31

SA

OA

RA

EA

space

© 2006

Am

erican Standard A

ll rights reserved

h


High-limit shutoff:

23 Btu/lb 32 Btu/lb 28 Btu/lb

economizer control type:Fixed Enthalpy

MA

© 2006

Am

erican Standard A

ll rights reserved

CAV system (Columbus)Energy: Fixed Enthalpy

HV

AC

en

erg

y co

nsu

mp

tion

,%

of

bas

e

75

80

85

90

95

100

none 70°Ffixed DB

75°F DB,55°F DPlockout

23Btu/lbfixed h

28Btu/lbfixed h

32Btu/lbfixed h

15% 14%16%

11%

14%




32

© 2006

Am

erican Standard A

ll rights reserved

180

160

140

120

100

80

60

40

20

0



85

80

75

70

65

60

5550

4540

3530


OA

RA

MASA

*Single-zone CAV system: Hot, dry day in El Paso, Texas

SA

fixed enthalpy:Example at Part Load*

© 2006

Am

erican Standard A

ll rights reserved

CAV system (Columbus)Humidity: Fixed Enthalpy

hou

rs w

ith

sp

ace

RH

> 5

8%

0

50

100

150

200

250

none 70°Ffixed DB


23Btu/lbfixed h

28Btu/lbfixed h

32Btu/lbfixed h

206 218 206 206 216207




33

180

160

140

120

100

80

60

40

20

0



85

80

75

70

65

60

5550

4540

3530


shutoff setting

© 2006

Am

erican Standard A

ll rights reserved

*Single-zone CAV system

economizer control type:Electronic Enthalpy (h)*

© 2006

Am

erican Standard A

ll rights reserved

CAV system (Columbus)Energy: Electronic Enthalpy

16%15% 14% 15%

none 70°Ffixed DB


28Btu/lbfixed h

electronicenthalpy

HV

AC

en

erg

y co

nsu

mp

tion

,%

of

bas

e

75

80

85

90

95

100




34

© 2006

Am

erican Standard A

ll rights reserved

CAV system (Columbus)Humidity: Electronic Enthalpy

hou

rs w

ith

sp

ace

RH

> 5

8%

0

50

100

150

200

250207 207206206 218

none 70°Ffixed DB


28Btu/lbfixed h

electronicenthalpy

SA

OA

RA

EA

space

© 2006

Am

erican Standard A

ll rights reserved

h


hRA

economizer control type:Differential Enthalpy

MA




35

© 2006

Am

erican Standard A

ll rights reserved

CAV system (Columbus)Energy: Differential Enthalpy

HV

AC

en

erg

y co

nsu

mp

tion

,%

of

bas

e

75

80

85

90

95

100

none 70°Ffixed DB


28Btu/lbfixed h

electronicenthalpy

differentialenthalpy

16%16%15% 14% 15%

© 2006

Am

erican Standard A

ll rights reserved

CAV system (Columbus)Humidity: Differential Enthalpy

hou

rs w

ith

sp

ace

RH

> 5

8%

0

50

100

150

200

250206 218 206 211207 207

none 70°Ffixed DB


28Btu/lbfixed h

electronicenthalpy





36

180

160

140

120

100

80

60

40

20

0



85

80

75

70

65

60

5550

4540

3530


OA

75°F DB50%RH


differential enthalpy:Example at part load*


Performance in a Variable-Volume System





37

© 2006

Am

erican Standard A

ll rights reserved

VAV system (Columbus)Energy: Fixed Dry Bulb

HV

AC

en

erg

y co

nsu

mp

tion

,%

of

bas

e

75

80

85

90

95

100


8%

11%10%9%

75°F DB,55°F DP

11%

© 2006

Am

erican Standard A

ll rights reserved

VAV system (Columbus)Humidity: Fixed Dry Bulb

nonehigh-limit shutoff setting (fixed DB)

hou

rs w

ith

sp

ace

RH

> 5

8%

0

50

100

150

200

250

29

55°F 65°F 70°F 75°F

319 2619

75°F DB,55°F DP

8




38

180

160

140

120

100

80

60

40

20

0



85

80

75

70

65

60

5550

4540

3530


OA

RA

MA

SA

RASA


© 2006

Am

erican Standard A

ll rights reserved

*VAV system: Mild, rainy day in Columbus, Ohio

55°F SAtemperature

fixed dry bulb:Example at part load*

180

160

140

120

100

80

60

40

20

0



85

80

75

70

65

60

5550

4540

3530


OA55°F

SA setpoint70°F economizershutoff setting

RA

MA

MA/SA

RASA

*VAV system: Columbus, Ohio

© 2006

Am

erican Standard A

ll rights reserved

VAV system:Economizer Effect on Space Humidity*




39

© 2006

Am

erican Standard A

ll rights reserved

VAV system (Columbus)Energy: Fixed Enthalpy

HV

AC

en

erg

y co

nsu

mp

tion

,%

of

bas

e

75

80

85

90

95

100

11%10% 9% 8%11% 11%

none 70°FfixedDB


23Btu/lbfixed h

28Btu/lbfixed h

32Btu/lbfixed h

electronicenthalpy

© 2006

Am

erican Standard A

ll rights reserved

VAV system (Columbus)Humidity: Fixed Enthalpy

hou

rs w

ith

sp

ace

RH

> 5

8%

0

50

100

150

200

250

none 70°FfixedDB


23Btu/lbfixed h

28Btu/lbfixed h

32Btu/lbfixed h

electronicenthalpy

1919 1929 19 8 2




40

© 2006

Am

erican Standard A

ll rights reserved

none 70°Ffixed DB


28Btu/lbfixed h

electronicenthalpy


VAV system (Columbus)Energy: Differential Enthalpy

11%10% 11% 12%11%

HV

AC

en

erg

y co

nsu

mp

tion

,%

of

bas

e

75

80

85

90

95

100

© 2006

Am

erican Standard A

ll rights reserved

VAV system (Columbus)Humidity: Differential Enthalpy

29 19 8 19 1819

hou

rs w

ith

sp

ace

RH

> 5

8%

0

50

100

150

200

250

none 70°Ffixed DB


28Btu/lbfixed h

electronicenthalpy





41

180

160

140

120

100

80

60

40

20

0



85

80

75

70

65

60

5550

4540

3530


OA

SA

55°FSA setpoint

60°FSA setpoint

RA

RA

*VAV system: Columbus, Ohio

© 2006

Am

erican Standard A

ll rights reserved

VAV system:SA Temperature Reset*

180

160

140

120

100

80

60

40

20

0



85

80

75

70

65

60

5550

4540

3530


55°FSA setpoint

modulatedeconomizer

integratedeconomizer

55°FSA setpoint

Traditional VAV System©

2006Am

erican Standard A

ll rights reserved




42

180

160

140

120

100

80

60

40

20

0



85

80

75

70

65

60

5550

4540

3530

48°FSA setpointreset

Cold-Air VAV System

© 2006

Am

erican Standard A

ll rights reserved


integratedeconomizer

modulatedeconomizer

© 2006

Am

erican Standard A

ll rights reservedEnergy/Humidity Effects Control strategy and high-limit shutoff

setting impact energy use AND indoor humidity levels

TRACE 700 can aid in analyzing various economizer control strategies

SA temperature reset can save cooling and reheat energy, BUT …increases supply fan and preheat energy, and raises space humidity




44

© 2006

Am

erican Standard A

ll rights reserved

single-zone systemsPackaged DX Rooftop

OA

RRA SA

Size OA intake hood for design airflow of system

© 2006

Am

erican Standard A

ll rights reserved

single-zone systemsIndoor Air Handler

Size OA duct for the air handler’s design airflow

SA

OA

RRA




45

© 2006

Am

erican Standard A

ll rights reserved

single-zone systemsUnit Ventilators

OA

RRA

SA

minimum = 1 ft

Size OA intake forthe unit ventilator’sdesign supply airflow

© 2006

Am

erican Standard A

ll rights reserved

multiple-zone systemsOutdoor Air Handler

RRA

SA

VAV terminals

Measure and controloutdoor airflow to maintainproper airflow rates

OA




46

© 2006

Am

erican Standard A

ll rights reserved

VAV terminals

multiple-zone systemsIndoor Air Handler

RRA

OA SA

Measure and control outdoor airflowto maintain proper airflow rates

alt

Options include flow-sensing dampersand airflow measurement stations

© 2006

Am

erican Standard A

ll rights reserved

multiple-zone systemsCommercial Self-Contained

RRA

RRA

minimumOA

RRA

SA

SA




47

© 2006

Am

erican Standard A

ll rights reserved

multiple-zone systems (central AHU)Commercial Self-Contained

DX coil

condensers

economizer coil

cooling tower

© 2006

Am

erican Standard A

ll rights reserved

dedicated outdoor-air systemsCentral Air Handling

RRA

RRA

SA

minimumOA

conditionedOA




48

© 2006

Am

erican Standard A

ll rights reserved

dedicated outdoor-air systemsWater-Source Heat Pumps

minimumOA

SARRA

conditionedOA

SARRA

Water-Source Heat Pumpwith waterside economizer coil

economizer coil

3-way valve

refrigerant-to-waterheat exchanger




49

© 2006

Am

erican Standard A

ll rights reserved

dedicated outdoor-air systemsFan-Coils

minimumOA

SA

RRA

conditionedOA

SASA

closed ineconomizermode

typicalcooling

coil

heatexchanger

Plate-and-Frame Heat Exchangeras waterside economizer




51

© 2006

Am

erican Standard A

ll rights reserved

application considerationsBuilding Pressure ControlStandard 90.1 requires:

Low-leak dampers Some method for controlling

building pressure

“Systems shall provide a means to relieve excess outdoor air during air economizer operation to prevent overpressurizing the building. The relief air outlet shall be located to avoid recirculation into the building”

ASHRAE/IESNA Std 90.1-2004, Section 6.5.1.1.5

return airRA

OAoutdoor(intake) air

space

© 2006

Am

erican Standard A

ll rights reserved

Building Pressure Terminology

relief airRL

RRArecirculated

return air

SAsupply air

EAlocalexhaustair

exfiltration

infiltration

mixed-airplenum

return-airplenum




52

© 2006

Am

erican Standard A

ll rights reserved

system configurationsNatural Relief

return airRA


spaceRRA

recirculatedreturn air

SAsupply air

EAlocalexhaustair

exfiltration

infiltration

mixed-airplenum

return-airplenum

Only works forsmall buildings

© 2006

Am

erican Standard A

ll rights reserved

system configurationsLocal Barometric Relief

return airRA


spaceRRA


SAsupply air

EAlocalexhaustair

exfiltration

infiltration

mixed-airplenum

return-airplenum

Works okay, butisn’t accurate

localrelief air




53

© 2006

Am

erican Standard A

ll rights reserved

system configurationsCentral Barometric Relief

return airRA


spaceRRA


SAsupply air

EAlocalexhaustair

exfiltration

infiltration

mixed-airplenum

return-airplenum

Doesn’t workvery well

centralrelief air

return airRA


space

© 2006

Am

erican Standard A

ll rights reserved

relief airRL

SAsupply air

EAlocalexhaustair

exfiltration

infiltration

mixed-airplenum

return-airplenum

system configurationsRelief Fan

Works well formost buildings

P

RRA


P




54

return airRA


space

© 2006

Am

erican Standard A

ll rights reserved

relief airRL

RRArecirculated

return air

SAsupply air

EAlocalexhaustair

exfiltration

infiltration

mixed-airplenum

return-airplenum

system configurationsReturn Fan

Works well withducted return

© 2006

Am

erican Standard A

ll rights reserved

application considerationsDynamic Reset“The system may be designed to reset thedesign outdoor air intake flow (Vot) and/orspace or zone airflow as operating conditions change. These conditions include but are not limited to:

Variations in occupancy … Variations in the efficiency … A higher fraction of outdoor air …”

ASHRAE Standard 62.1–2004




55

© 2006

Am

erican Standard A

ll rights reserved

application considerationsDynamic Reset Control“These conditions include … Variations in occupancy or ventilation airflow in one or more individual zones for which ventilation airflow requirements will be reset.

“Note: Examples of measures for estimatingsuch variations include: occupancy scheduled by time-of-day, a direct count of occupants, or an estimate of occupancy or ventilation rate per person using occupancy sensors such as those based on indoor CO2 concentrations.”


0

mechcoolingheating

integratedecon

outdoorair

modulatedecon

flow

, %

maxheating

load

maxcoolingload

100

80

60

40

20

application considerationsDynamic Reset

chilledwater

mincoolingload

high-limitshutoff

returnair




56

© 2006

Am

erican Standard A

ll rights reserved

dynamic reset controlMinimum Intake Airflow

intake

exhaust

=exfiltr’n

resetlimit

relief

For positive pressure …intake exfiltration + exhaust

design

design

exhaust=intake

dynamic reset

allowable reset

exfiltr’n

© 2006

Am

erican Standard A

ll rights reserved

dynamic reset controlMinimum Intake Airflow

intake

exhaust

=

infiltr’n

resetlimit

design

For negative pressure …intake + infiltration exhaust

relief

exhaust=intake

dynamic reset

allowable reset

infiltr’n

design




57

© 2006

Am

erican Standard A

ll rights reserved

application considerationsDynamic Reset“These conditions include … :

Variations in occupancy … Variations in efficiency with which outdoor

air is distributed to the occupants under different ventilation system airflows and temperatures

A higher fraction of outdoor air in theair supply due to intake of additional outdoor air for free cooling or exhaust air makeup”


© 2006

Am

erican Standard A

ll rights reserved

airside economizersWhat We Covered ASHRAE 90.1 requirements, exceptions

(location/size, controls, integration)

Energy costs and humidity levels(constant- vs. variable-air-volume systems)

Economizer implementation in various system types

Application considerations(building pressurization)

Trane Engineers Newsletter Live satellite broadcast

Bibliography

Page 1 of 1

Industry Standards American Society of Heating, Refrigeration, and Air-Conditioning

Engineers (ASHRAE). ANSI/ASHRAE IESNA Standard 90.1-2004: Energy Standard for Buildings Except Low-Rise Residential Buildings. Available at http://xp20.ashrae.org/ frame.asp?standards/std90.html

American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc. (ASHRAE). Standard 90.1-2004 User’s Manual. Available at http://www.ashrae.org

American Society of Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE). ANSI/ASHRAE Standard 62.1-2004: Ventilation for Acceptable Indoor Air Quality. Available at < http://www.realread.com/prst/pageview/browse.cgi?book=1931862672>

American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc. (ASHRAE). Standard 62.1-2004 User’s Manual. Available at http://www.ashrae.org

Articles Brambley, M., Pratt, R., Katipamula, S. et al. 1998. “Diagnostics for

Outdoor Air Ventilation and Economizers.” ASHRAE Journal 40-10 (October), 49-55.

Taylor, S. 2000. “Comparing Economizer Relief Systems.” ASHRAE Journal 42-9 (September), 33-40, 42.

Trane Publications Stanke, D. “Keeping Cool with Outdoor Air: Airside Economizers.”

Engineers Newsletter 35-2 (2006). Available at <http://www.trane.com/commercial/ navigation/files/pdf/6/admapn020en_0406.pdf>

Trane. 2002. HVAC System Control (Trane Air Conditioning Clinic TRG-TRC017-EN). La Crosse, WI: Inland Label and Marketing Services, LLC.

03 May 2006



Brian Fiegen | manager, applications engineering & systems marketing | Trane

Brian has been with Trane for 23 years in a variety of product management and system development roles. Specifically, he has worked with Trane’s air handling and VAV product lines, including unit controls for that equipment. He is presently responsible for Trane’s applications engineering and systems marketing team, and is well-respected for his extensive knowledge in airside design and controls. Brian is a member of ASHRAE.

John Murphy | senior applications engineer | Trane

John has been with Trane since 1993. His primary responsibility as an applications engineer is to aid design engineers and Trane sales personnel in the proper design and application of HVAC systems. His main areas of expertise include dehumidification, air-to-air energy recovery, psychrometry, ventilation, and ASHRAE Standards 15, 62.1, and 90.1. John is the author of numerous Trane application manuals and Engineers Newsletters, and is a frequent presenter on Trane’s Engineers Newsletter Live series of satellite broadcasts. He also is a member of ASHRAE, has authored articles for the ASHRAE Journal, and is a member of ASHRAE’s “Moisture Management in Buildings” and “Mechanical Dehumidifiers” technical committees.

Dennis Stanke | staff applications engineer | Trane

Dennis, a mechanical engineer from the University of Wisconsin, has been with Trane since 1973 and is a specialist in airside systems and controls, ventilation, indoor air quality, and dehumidification. He’s authored numerous publications on these subjects, has appeared in several Engineers Newsletter Live broadcasts, and holds three U.S. patents related to VAV system control. An active ASHRAE member, Dennis currently serves as chair for SSPC62.1, the committee responsible for ASHRAE Standard 62, Ventilation for Acceptable Indoor Air Quality, and is a member of the editorial board for the ASHRAE publication, IAQ Applications. He combines his knowledge of ventilation system design and control with knowledge of IAQ-related issues and solutions to help designers meet IAQ, ventilation, and energy challenges in commercial, institutional, and high-rise residential buildings. In addition to his Trane responsibilities as staff applications engineer, Dennis also serves on research advisory boards at UC–Berkeley (Centers for the Built Environment) and Penn State University (Indoor Environment Center), and is an active member of the USGBC LEED® Technical Advisory Group for Indoor Environmental Quality (EQ TAG).

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