standard 62.1: a vav dynamic reset approach

ASHRAE Standard 62.1-2010 DCV in Multiple-Zone Systems: Ventilation Reset Control

Agenda

Presenter: Dennis Stanke, Trane Staff Applications Engineer, FASHRAE

Abstract: ASHRAE Standard 62.1 “Ventilation for Acceptable Indoor Air Quality,” provides minimum outdoor airflow requirements at design conditions. However, ASHRAE Standard 90.1 requires some systems to be operated sothat current ventilation capacity modulates to match current ventilation load (i.e., demand). Standard 62.1 allows optional “dynamic reset” controls to help match current capacity to load, but design details for such controls are left to the designer. One design approached, described in this presentation, combines ventilation reset control at the system level with various zone-level “demand controlled ventilation” strategies.

Learning objectives After viewing this program Participants will be able to:

1. Apply ventilation system design calculations for three ventilation systems: single-zone, 100% outdoor air, and multiple-zone systems (MZS)2. Summarize how demand controlled ventilation (DCV) can be incorporated in all three ventilation systems3. Apply dynamic reset to VAV systems using ventilation reset control, which responds to changes in system ventilation efficiency4. Apply dynamic reset to VAV systems by combining zone-level DCV with system-level ventilation reset control, to respond to both changes in zone population and changes in system ventilation efficiency

Agenda

6.2.2 Zone calculations (zone OA)6.2.3 Single-zone systems (OA intake)6.2.4 100% OA systems (OA intake)6.2.5 Multiple-zone recirc systems (OA intake)6.2.7 Dynamic reset

Wrap-up/discussion

PresenterAgenda_.ai 1 9/6/2012 3:06:02 PM

Multiple-Zone Ventilation© 2012 Trane a business of Ingersoll Rand. All rights reserved

1

Standard 62.1-2010 DCV in Multiple-Zone SystemsV til ti R t C t lStandard 62.1-2010 DCV in Multiple-Zone SystemsV til ti R t C t l

Dennis Stanke

September 2012

Ventilation Reset Control Ventilation Reset Control

Ingersoll Rand

© 2009 Trane2

Approved for 1.0 GBCI hours for LEED professionals

Standard 62.1-2010 DCV in Multiple-Zone Systems-Ventilation Reset Control: Course ID: 0090008756

1.5


2

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

f C l ti f AIA b il blof Completion for non-AIA members are 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, or dealing in any material or product.

© 2009 Trane3

p

Visit the Registered Continuing Education Programs (RCEP) Website to check state Programs (RCEP) Website to check state requirements for Professional Development Hours (PDH) for professional engineers.

www.RCEP.net

© 2009 Trane4


3

Copyrighted Materials

This presentation is protected by U.S. and international copyright laws. Reproduction, distribution, display, and use of the presentation without written permission of Trane is prohibited.

© 2012 Trane a business of Ingersoll-Rand All rights reserved

© 2009 Trane5

© 2012 Trane, a business of Ingersoll-Rand. All rights reserved.

Learning Objectives

After today’s program you will be able to:

• Apply ventilation system design calculations for three ventilation systems: single-zone, 100% outdoor air, and y g , ,multiple-zone systems (MZS)

• Summarize how demand controlled ventilation (DCV) can be incorporated in all three ventilation systems

• Apply dynamic reset to VAV systems using ventilation reset control, which responds to changes in system ventilation efficiency

• Apply dynamic reset to VAV systems by combining zone-

© 2009 Trane6

Apply dynamic reset to VAV systems by combining zonelevel DCV with system-level ventilation reset control, to respond to both changes in zone population and changes in system ventilation efficiency


4

Abstract and Venues

• Abstract– ASHRAE Standard 62.1 “Ventilation for Acceptable Indoor Air Quality,”

provides minimum outdoor airflow requirements at design conditions. p q gHowever, ASHRAE Standard 90.1 requires some systems to be operated so that current ventilation capacity modulates to match current ventilation load (i.e., demand). Standard 62.1 allows optional “dynamic reset” controls to help match current capacity to load, but design details for such controls are left to the designer. One design approached, described in this presentation, combines ventilation reset control at the system level with various zone-level “demand controlled ventilation” strategies.

© 2009 Trane7

• Venues (1.5 hours)– 11SEP2012 Richland, WA

– 15SEP2012 Portland, OR

Standard 62.1 Ventilation

Why It’s Important …

• For comfort – reduce odors and irritation

• For health – reduce building related illness and sick building syndrome

• For productivity – reduce absenteeism and increase worker satisfaction

• For compliance … – Section 6.2 (VRP) req’d by IMC and UMC

© 2009 Trane8

( ) q y

– Section 4 thru 8 req’d by Std 189.1 (one IgCC path)

– Section 4 thru 7 req’d as LEED prerequisite

– All of Std 62.1 required by ENERGY STAR® and bEQ


5

6.0 Procedures

• 6.1 General. Find OA intake using VRP or IAQP, or find opening parameters sing NVPfind opening parameters using NVP

• 6.2 Ventilation Rate Procedure– Prescribes minimum rates for “typical” zones and

calculations for minimum outdoor air intake rate

• 6.3 IAQ Procedure– Specifies performance based on contaminant levels and

© 2009 Trane9

subjective evaluation

• 6.4 Natural Ventilation Procedure– Prescribes opening areas and requires both MV and NV

6.2 Ventilation Rate Procedure

• 6.2.1 Outdoor air treatment

• 6.2.2 Zone calculations (zone OA)

• 6.2.3 Single-zone systems (OA intake)

• 6.2.4 100% OA systems (OA intake)

• 6.2.5 Multiple-zone recirc systems (OA intake)

• 6.2.6 Design for varying operating conditions

• 6 2 7 Dynamic reset

© 2009 Trane10

• 6.2.7 Dynamic reset


6

6.2.2 Zone Calculations

1. Calculate breathing-zone outdoor airflow, using Table 6 1 rates (Rp cfm/per Ra cfm/ft2)

design

6-1 rates (Rp cfm/per, Ra cfm/ft2)

Vbz = Rp × Pz + Ra × Az (Eq 6-1)where Pz = peak zone population

2. Find zone air distribution effectiveness

Look up Ez (typically 1.0) (Tab 6-2)

3 Calculate zone outdoor airflow

© 2009 Trane11

3. Calculate zone outdoor airflow

Voz = Vbz/Ez (Eq 6-2)









© 2009 Trane12



7

6.2.3 Single-Zone Systems

One recirculating air handlerserves one zone

SA(Vpz)

OA(Vot)

RAEA

zone

© 2009 Trane13

zone


For single-zone systems

design

– Complete first three steps for zone

– Then, find outdoor air intake flow

Vot = Voz (Eq 6-3)

Note:– No design credit for occupant diversity, i.e., must

© 2009 Trane14

g p yassume peak zone population

– Zone ventilation efficiency (Evz = Voz-actual/Voz-design) is probably less than 1.0 during operation


8


• That’s it for design, but does 62.1-2010 allow i t k i fl t d i ti ?

operation

intake airflow to vary during operation?

• Of course … – Section 6.2.7 allows optional dynamic reset of zone

outdoor airflow using various approaches … Population estimate based on scheduling, occupancy

sensing, people counting

Bio effluent control using CO based reset

© 2009 Trane15

Bio-effluent control using CO2-based reset

– Read Journal articles for “how-to” ideas

Dynamic Reset Approaches

• Section 6.2.7 allows dynamic reset of OA intake based on operating conditions, including:

operation

based on operating conditions, including:– Variations in population – zone-level demand

controlled ventilation (DCV) – Variations in system ventilation efficiency – system-

level controls required• Different systems use different approaches

– For single-zone systems, use simple zone-level DCV– For 100% OA systems, use zone-level DCV, but only

© 2009 Trane16

y , , yin some VAV systems

– For multiple-zone systems, use system-level controls, which can be combined with zone-level DCV

• Some examples …


9

z

12004800Now CO2 varies,so DCV isn’t as easy

single-zone system

CO2-based Zone-DCV

62.1-2007CO2 varies

operation

1600

2400

3200

4000

bre

ath

ing

zo

ne O

A,

Vb

z diffe

ren

tial C

O2 , p

pm400

600

800

1000

62.1 2007

CO2 = 700 ppm(Std 62-2001)

(Std 62.1-2007)

Vbz = 2190 cfm

Vbz = 3900 cfm

© 2009 Trane17

40 80

800

zone population, Pz

b

120 160 200 240

200

000

© 2005 American Standard Inc.

lecture classroomAz = 4000 ft2

design Pz = 260 p

one way to implement zone-DCV …

62.1 User’s Manual

• Find breathing zone OA (Vbz) rangeVb (R P R A )

operation

Vbz = (Rp Pz + Ra Az)Vbz-des = (7.5 260 + 0.06 4000)/1.0 = 2190 cfmVbz-min = (7.5 0 + 0.06 4000)/1.0 = 240 cfm

• Find target indoor CO2 (Crz) rangeCrz – Co = N/(Vbz/Pz)Crz-des – Co = 0.0105/(2190 cfm/260 p) 1250 ppmCrz-min – Co = 0.000350 – 0.000350 0 ppm

© 2009 Trane18

• The Controller: Match Vbz signal range to Crz range

• Adjust OA damper to deliver Vot = Vbz-des/Ez at max signal, = Vbz-min/Ez at min signal


10

zone DCV for single-zone systems

62.1 User’s Manual

The Controller

operation

Vbz(cfm)

2190

© 2009 Trane19

Crz - Co (CO2, ppm)

240

0 1250

*V

ot)

12004800

zone DCV for single-zone systems

62.1 User’s Manualoperation

Controller adjusts Vbz, based on sensed CO2

1600

2400

3200

4000

hin

g z

on

e O

A,

Vb

z (=

Ez d

iffere

ntia

l CO

2 , pp

m400

600

800

1000

Vbz

CO2

© 2009 Trane20

40 80

800

zone population, Pz

bre

ath

120 160 220 240

200

000

© 2005 American Standard Inc.

lecture classroomAz = 4000 ft2

design Pz = 260 p


11









© 2009 Trane21


6.2.4 100% OA Systems

One non-recirculating air handler serves many zones

design

EA

SA

RA

zoneOA(Vot)

CA

Voz

© 2009 Trane22

SA

RA

zone

Voz


12


For 100% OA systems

design

– Complete first three steps for each zone

– Then, find outdoor air intake flow

Vot = Voz (Eq 6-4)

Note:– No design credit for occupant diversity, i.e., must

© 2009 Trane23

g p yassume peak zone population in each zone

– Zone ventilation efficiency (Evz = ΣVoz-actual/ΣVoz-design) is probably less than 1.0 during operation


• That’s it for design but does 62.1-2007 allow i t k i fl t d i ti ?

operation

intake airflow to vary during operation?

• Well, that depends … – Section 6.2.7 allows optional dynamic reset, but … For constant volume OA systems there’s no way to reset

outdoor airflow

For VAV OA systems, intake airflow can be reduced if

All i l d i d d t d

© 2009 Trane24

– All zones include pressure-independent dampers

– DCV zones include DCV sensors and controls

– The 100% OA unit includes VAV controls


13









© 2009 Trane25


6.2.5 Multiple-Zone Systems

One recirculating air handler serves many zones

SA

RA

EA

space

OA(Vot)

Vpz

© 2009 Trane26

SA(Vps)

space

(Vot)

Single-path system (dual-path is more complex)


14

For multiple-zone recirculating systems, complete first three steps for each zone then solve MZS equations:

design


steps for each zone, then solve MZS equations:

4. Find primary outdoor air fraction, Zp

Zp = Voz/Vpz-min (6-5)

5. Find uncorrected outdoor airflow, Vou

Vou = D*(Rp×Pz) + (Ra×Az) (6-6)

6 Fi d t til ti ffi i E

© 2009 Trane27

6. Find system ventilation efficiency, Ev

Calculate Ev per equations (App A)

7. Find outdoor air intake flow, Vot:

Vot = Vou/Ev (6-8)


4. Find primary outdoor air fraction for each zone or each critical zone

design

each critical zone

Zp = Voz/Vpz (Eq 6-5)

Note: – Vpz = Vpz-design = minimum primary airflow expected at

“ventilation design” condition (usually higher than minimum box setting)

– Picking Vpz-design - probably most confusing part for MZS

© 2009 Trane28

Picking Vpz design probably most confusing part for MZS

Many use minimum box setting – easy but conservative

Some use 8760 simulation to find an accurate value(Maybe Std 62.1 should use 0.5*Vpz-design as default)

NOTE: “ventilation design” ≠ “thermal design”


15


5. Find uncorrected outdoor airflow

V D* (R P ) (R A ) (E 6 6)

design

Vou = D*(Rp×Pz) + (Ra×Az) (Eq 6-6)

Note: – Design credit for occupant diversity (D)

– D = expected population/sum-of-peak populations= 50 people/100 chairs = 0.5

– Occupant diversity reduces

© 2009 Trane29

uncorrected outdoor airflow


6. Find system ventilation efficiency

Fi t fi d td i f ti (X ) i

design

– First, find average outdoor air fraction (Xs) using system primary airflow (Vps) at ventilation design

Xs = Vou/Vps (Eq A-1)

– Then, find zone ventilation efficiency (Evz)

Evz = 1 + Xs – Zpz (Eq A-2)

– Finally, lowest Evz is system ventilation efficiency (Ev)

© 2009 Trane30

Ev = min(Evz) (Eq A-8)

Note: – Lowest Evz defines the “critical zone” for ventilation


16


7. Find outdoor air intake flow

V t V /E (E 6 8)

design

Vot = Vou/Ev (Eq 6-8)

Note: – Compared to 2001, the 2010 rates and equations

reduce intake airflow (Vot) for many systems

© 2009 Trane31









© 2009 Trane32



17

Multiple-Zone Systems

• That’s it for MZS design but can intake flow vary d i ti ?

operation

during operation?

• Sure– Provided Section 5.3.1 (no less than required Vot

under all “operating” conditions) is met …

– Section 6.2.7 allows optional dynamic reset, regardless of system type

© 2009 Trane33

• But how do you do it in a VAV system?


• Already reviewed for single zone and 100% OA

operation

• For VAV MZS operation, you could … – Use “ventilation reset control” (VRC) Reset intake flow based only on changes in system

ventilation efficiency (Ev) due to changes in zone airflow

– Combine system-level VRC with zone-level DCV Reset intake flow based on changes in system ventilation

efficiency due to changes in both zone airflow and

© 2009 Trane34

efficiency due to changes in both zone airflow and population

– Use system-level DCV of some sort Approaches not well-known, but hopefully Dr. Lau’s

research addresses this


18

Ventilation Reset Control

• VRC resets system-level outdoor air intake flow(V t) t t l d diti b

operation

(Vot) at part load conditions by:– Assuming design population in all zones without

accounting for reduced population in any zone

– Accounting for changes in system ventilation efficiency(Ev) due to zone and system airflow changes

– Solving the MZS equations in real time (quasi-steady state) to find current intake flow (Vot) set point required

© 2009 Trane35

state) to find current intake flow (Vot) set point required

• Here’s an example building using one possible VRC approach

VRC w/o Zone-Level DCV

Single-Supply VAV System: Ventilation Design

Votreq’d

@ design

design

Single Supply VAV System: Ventilation Design

8, 810population Pz 140 140 260 260 5 40prim airflow Vpz 6,500 6,700 5,500 7,900 500 1,700min expect Vpzm 4,000 4,000 4,000 4,000 300 1,300vent rate Vbz 1,880 1,880 2,190 2,190 85 760vent fract Zpz 0.470 0.470 0.548 0.548 0.283 0.585

Ventilation design - For each zone use:Pz = peak zone populationVpz = peak primary airflow Vpzm = minimum expected Vpz @ design

Then find:

Then, find:Vou = D*Rp*Pz + Ra*Az (5)

D = Ps/Pz = 550/845 = 0.65= 0.65*7,130 + 1,860 = 6,500

Ev = min(Evz) (6)

© 2009 Trane36

Then, find:Vbz = Rp*Pz + Ra*Az (1)Ez = design zone air dist eff (2)Voz = Vbz/Ez (3)Zpz = Voz/Vpzm = Vbz/(Ez*Vpzm) (4)

For the system use:Ps = highest system population = 550LDF= load diversity factor = 0.7

Ev = min(Evz) (6)Vps = LDF*ΣVpz

= 0.7*28,800 = 20,200Xs = Vou/Vps

= 6,500/20,200 = 0.322Evz = 1+ Xs – Zpz

= 1 + 0.322 – 0.585 = 0.738= min(Evz) = 0.738

Vot = Vou/Ev = 6,500/0.738 = 8,810 (7)


19

Votreq’d

(current)


Votreq’d

@ design

Single-Supply VAV System: 100% Thermal Load (2:00 pm Friday perhaps)

operation

8, 3908, 810population Pz 140 140 260 260 5 40prim airflow Vpz 4,960 5,000 4,000 4,000 500 1,700vent rate Vbz 1,880 1,880 2,190 2,190 85 760vent fraction Zdz 0.379 0.376 0.548 0.548 0.170 0.447

Single Supply VAV System: 100% Thermal Load (2:00 pm Friday, perhaps)

Now, controls calculate:Vou = D*Rp*Pz + Ra*Az (5)

D = Ps/Pz = 550/845 = 0.65= 0.65*7,130 + 1,860 = 6,500

Ev = min(Evz) (6)

Operation w/o DCV: For each zone use:Pz = peak zone population (entry)

Then, controls determine or calculate:Vpz = current primary airflow (sensed)Vbz = Rp*Pz + Ra*Az (calc or entry) (1)

© 2009 Trane37

Ev = min(Evz) (6)Vps = Vpz

= 20,200 Xs = Vou/Vps

= 6,500/20,200 = 0.322Evz = 1+ Xs – Zpz

= 1 + 0.322 – 0.548 = 0.775= min(Evz) = 0.775

Vot = Vou/Ev = 6,500/0.775 = 8,390 (7)

Vbz = Rp Pz + Ra Az (calc or entry) (1)Ez = current value (2)Voz = Vbz/Ez (3)Zpz = Voz/Vpz (4)


Votreq’d

(current)


Votreq’d

@ design


operation

8, 3908, 810population Pz 140 140 260 260 5 40prim airflow Vpz 4,960 5,000 4,000 4,000 500 1,700vent rate Vbz 1,880 1,880 2,190 2,190 85 760vent fraction Zdz 0.379 0.376 0.548 0.548 0.170 0.447


Now, controls calculate:Vou = D*Rp*Pz + Ra*Az (5)

D = Ps/Pz = 550/845 = 0.65= 0.65*7,130 + 1,860 = 6,500

Ev = min(Evz) (6)

Operation w/o DCV: For each zone use:Pz = peak zone population (entry)

Then, controls determine or calculate:Vpz = current primary airflow (sensed)Vbz = Rp*Pz + Ra*Az (calc or entry) (1)

Vot-actual is less than Vot-design

VRC w/o DCV reduces

© 2009 Trane38

Ev = min(Evz) (6)Vps = Vpz

= 20,200 Xs = Vou/Vps

= 6,500/20,200 = 0.322Evz = 1+ Xs – Zpz

= 1 + 0.322 – 0.548 = 0.775= min(Evz) = 0.775

Vot = Vou/Ev = 6,500/0.775 = 8,390 (7)

Vbz = Rp Pz + Ra Az (calc or entry) (1)Ez = current value (2)Voz = Vbz/Ez (3)Zpz = Voz/Vpz (4)


VRC w/o DCV reduces required Vot, even at 100% thermal load:

Ev-actual ≥ Ev-design


20


Votreq’d

@ design

Votreq’d

(current)


operation

8, 810population Pz 140 140 260 260 5 40prim airflow Vpz 4,960 5,000 4,000 4,000 500 1,700vent rate Vbz 1,880 1,880 2,190 2,190 85 760vent fraction Zpz 0.379 0.376 0.548 0.548 0.170 0.447

8, 390

population Pz 140 140 260 260 5 40prim airflow Vpz 4,000 3,700 4,200 4,300 300 1,700vent rate Vbz 1,880 1,880 2,190 2,190 85 760vent fraction Zpz 0 470 0 508 0 521 0 509 0 283 0 447

8,810 7,780


Single-Supply VAV System: 90% Thermal Load (1:00 pm Monday, perhaps)

© 2009 Trane39

Now, controls determine or calculate:Vou = D*Rp*Pz + Ra*Az = 6,500Vpz = (sensed)Vps = Vpz = 18,200Xs = Vou/Vps = 6,500/18,200 = 0.357Ev = 1 + 0.357 – 0.521 = 0.836Vot = Vou/Ev = 6,500/0.836 = 7,780

vent fraction Zpz 0.470 0.508 0.521 0. 509 0.283 0.447

VRC w/o DCV reduces required Vot even more at lower thermal loads:Ev-actual >> Ev-design


• Already reviewed for single zone and 100% OA

operation

• For VAV MZS operation, you could … – Use “ventilation reset control” (VRC) Reset intake flow based only on changes in system

ventilation efficiency (Ev) due to changes in zone airflow

– Combine system-level VRC with zone-level DCV Reset intake flow based on changes in system ventilation

efficiency due to changes in both zone airflow and

© 2009 Trane40

efficiency due to changes in both zone airflow and population

– Use system-level DCV of some sort Approaches not well-known, but hopefully Dr. Lau’s

research addresses this


21

VRC with Zone-Level DCV

• VRC resets system-level outdoor air intake flow(V t) t t l d diti b

operation

(Vot) at part load conditions by:– Assuming design population in non-DCV zones while

accounting for reduced population in DCV zones

– Accounting for changes in system ventilation efficiency(Ev) due to zone and system airflow changes

– Solving the MZS equations in real time (quasi-steady state) to find current intake flow (Vot) set point required

© 2009 Trane41

state) to find current intake flow (Vot) set point required

• Here’s the same example building using the same VRC approach, but with various “zone types” including both non-DCV and DCV zones

VRC w/Zone-Level DCV

• Defining zone types

Z ith t DCV

operation

– Zones without DCV Non-DCV zones (NON): Pz = peak zone population at all

conditions, regardless of actual population

– Population-estimating DCV zones (EST) include: “Time-of-day” zones (TOD): Pz = predicted population

“Occupied/unoccupied” (OCC) zones: Pz = peak or zero population, depending on occupancy sensor

© 2009 Trane42

population, depending on occupancy sensor

“Count” zones (COU): Pz = sensed number of occupants

– CO2-based DCV zones (CO2) (Pz = unknown) Breathing-zone OA flow depends on sensed difference

between primary and zone CO2: Vbz = f (ΔCO2)


22

Votreq’d

@ design

VRC w/ Zone-Level DCV

Single-Supply VAV System: Design Ventilation

design

CO2 ESTNON NONNONNON

8, 810

Single Supply VAV System: Design Ventilation

population Pz 140 140 260 260 5 40prim airflow Vpz 6,500 6,700 5,500 7,900 500 1,700min expect Vpzm 4,000 4,000 4,000 4,000 300 1,300vent rate Vbz 1,880 1,880 2,190 2,190 85 760vent fract Zpz 0.470 0.470 0.548 0.548 0.283 0.585

Design ventilation: For each zone use:Pz = peak zone populationVpz = peak primary airflow Vpzm = minimum expected Vpz @ design

Then find:

Then, find:Vou = D*Rp*Pz + Ra*Az (5)

D = Ps/Pz = 550/845 = 0.65= 0.65*7,130 + 1,860 = 6,500

Ev = min(Evz) (6)

DCV: No impact on Vot-design

© 2009 Trane43

Then, find:Vbz = Rp*Pz + Ra*Az (1)Ez = design zone air dist eff (2)Voz = Vbz/Ez (3)Zpz = Voz/Vpzm = Vbz/(Ez*Vpzm) (4)


Ev = min(Evz) (6)Vps = LDF*ΣVpz

= 0.7*28,800 = 20,200Xs = Vou/Vps

= 6,500/20,200 = 0.322Evz = 1+ Xs – Zpz

= 1 + 0.322 – 0.585 = 0.738= min(Evz) = 0.738

Vot = Vou/Ev = 6,500/0.738 = 8,810 (7)


Votreq’d

@ designCO2

Votreq’d

(current)


operation

ESTNON NONNONNON

For each NON-DCV zone use:Pz = peak zone population (entry)Vbz = Rp*Pz + Ra*Az (entry)

For each EST-DCV zone:Pz = estimated population (sensed)Vb R *P R *A ( l )

Now, for system:Vou = D*NONRp*Pz + NONRa*Az (5)

+ ESTRp*Pz + ESTRa*Az + CO2VbzPs = highest system population = 550 D = Ps/Pz-peak = 550/845 = 0.65

*

8, 810population Pz 140 140 ??? 260 5 0prim airflow Vpz 4,960 5,400 4,000 4,000 500 1,300vent rate Vbz 1,880 1,880 1,300 2,190 85 360vent fraction Zpz 0.379 0.348 0.325 0.548 0.170 0.277


8, 030

8, 390

© 2009 Trane44

Vbz = Rp*Pz + Ra*Az (calc)For each CO2-DCV zone use:

Vbz = f (ΔCO2) (sense & calc)For each zone, controls determine:

Vpz = current zone primary (sensed) Vbz = current reqmt (entry or calc) (1)Ez = current value (2)Voz = Vbz/Ez (3)Zpz = Voz/Vpz (4)

= 0.65*4,780 + 1,260 + 0 + 360 + 1,300 = 6,030

Ev = min(Evz) (6)Vps = Vpz = 20,200 (calc) Xs = Vou/Vps = 6,030/20,200 = 0.299Evz = 1 + Xs – Zpz

= 1 + 0.299 – 0.548 = 0.751Vot = small(Vou/Ev or Vot-des) (7)

= 6,030/0.751 = 8,030


23


Votreq’d

@ designCO2

Votreq’d

(current)


operation

ESTNON NONNONNON

For each NON-DCV zone use:Pz = peak zone population (entry)Vbz = Rp*Pz + Ra*Az (entry)

For each EST-DCV zone:Pz = estimated population (sensed)Vb R *P R *A ( l )

Now, for system:Vou = D*NONRp*Pz + NONRa*Az (5)

+ ESTRp*Pz + ESTRa*Az + CO2VbzPs = highest system population = 550 D = Ps/Pz-peak = 550/845 = 0.65

*



8, 030

8, 390

VRC w/DCV reduces Vot-actual

© 2009 Trane45

Vbz = Rp*Pz + Ra*Az (calc)For each CO2-DCV zone use:

Vbz = f (ΔCO2) (sense & calc)For each zone, controls determine:

Vpz = current zone primary (sensed) Vbz = current reqmt (entry or calc) (1)Ez = current value (2)Voz = Vbz/Ez (3)Zpz = Voz/Vpz (4)

= 0.65*4,780 + 1,260 + 0 + 360 + 1,300 = 6,030

Ev = min(Evz) (6)Vps = Vpz = 20,200 (calc) Xs = Vou/Vps = 6,030/20,200 = 0.299Evz = 1 + Xs – Zpz

= 1 + 0.299 – 0.548 = 0.751Vot = small(Vou/Ev or Vot-des) (7)

= 6,030/0.751 = 8,030


– For design, note:D P / P k b t di it

operation

D = Ps/ALLPz-peak, because occupant diversitydistributes total population among all zones in system

D applies to all zones for design

– For operation, note: D applies NON-DCV zones (occupant diversity credit)

D = 1.0 for EST-DCV zones (estimated Pz is independent of occupant diversity)

© 2009 Trane46

p y)

D isn’t used for CO2-DCV zones (Vbz is determined by controller, without regard to occupant diversity

Rule: To assure adequate heat/cool capacity, Vot during operation must never be greater than Vot at design


24


Votreq’d

@ design

Votreq’d

(current)

operation

Single-Supply VAV System: 100%Thermal Load (2:00 pm Friday perhaps)

CO2 ESTNON NONNONNON


8, 030

population Pz 140 140 ??? 260 5 0prim airflow Vpz 4,000 3,700 4,200 4,300 300 1,700vent rate Vbz 1,880 1,880 1,300 2,190 85 360vent fraction Zpz 0 470 0 508 0 521 0 509 0 283 0 447

8,810 7,780

Single Supply VAV System: 100%Thermal Load (2:00 pm Friday, perhaps)

Single-Supply VAV System: 90% Thermal Load (1:00 pm Monday, perhaps)

7,440

© 2009 Trane47

vent fraction Zpz 0.470 0.508 0.521 0. 509 0.283 0.447

Now:Vou = 6,030Vps = Vpz = 18,200Xs = 6,030/18,200 = 0.331Ev = 1 + 0.331 – 0.521 = 0.810Vot = Vou/Ev = 6,030/0.810 = 7,440

VRC with DCV reduces Vot-actual more, saves

more energy

Implementation

• For VRC alone or combined with zone-level DCV, d i ll i l ddesign usually includes:– Communicating DDC-VAV boxes

– BAS with equation-solving capability

– Intake-airflow sensing and control at the AHU

– Building pressure control (which limits Vot reduction)

• Remember:

© 2009 Trane48

– Std 62.1 allows DCV in any system

– Std 90.1 requires DCV in 40 p/1000 ft2 zones

– Std 189.1 requires DCV in 25 p/1000 ft2 zones


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Quick Summary

Dynamic reset depends on ventilation system type– Single-zone systems (no design population diversity) Optional zone DCV allowed

– 100% OA systems (no design population diversity) CV: Zone DCV & Vot reset not useful w/constant Vot

VAV: Zone DCV & Vot reset allowed but not cheap

– Multiple-zone sys (population diversity design credit):

© 2009 Trane49

Optional system Vot reset allowed

– Based only on system ventilation efficiency (VRC)

– Based on zone DCV combined with system VRC

– Based only on zone DCV (not covered)

Thanks

Any questions?

© 2009 Trane50

Dennis Stanke

[email protected]

standard 62.1: a vav dynamic reset approach

Education

systemlevel ventilation

ventilation systems3

zonezone level dcv

system ventilation efficiency4

current ventilation

zonelevel dcv

zone calculations zone

zone population