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 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.

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 systems
3. Apply dynamic reset to VAV systems using ventilation reset control, which responds to changes in
system ventilation efficiency
4. 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

Standard 62.1-2010 DCV in Multiple-Zone Systems
Ventilation R
V til ti Reset Control
tC t l
Dennis Stanke
September 2012

Ingersoll Rand

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

Approved for 1.0 GBCI hours for LEED professionals

1.5
2 © 2009 Trane

Multiple-Zone Ventilation 1
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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-zone
level DCV with system-level ventilation reset control, to
respond to both changes in zone population and changes
in system ventilation efficiency

6 © 2009 Trane


Abstract and Venues
• Abstract
– ASHRAE Standard 62.1 “Ventilation for Acceptable Indoor Air Quality,”
p
provides minimum outdoor airflow requirements at design conditions.
q g
However, 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.
• Venues (1.5 hours)
– 11SEP2012 Richland, WA
– 15SEP2012 Portland, OR

7 © 2009 Trane

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
( ) 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

8 © 2009 Trane


6.0 Procedures

• 6.1 General. Find OA intake using VRP or IAQP, or
find opening parameters using NVP
sing
• 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
subjective evaluation
• 6.4 Natural Ventilation Procedure
– Prescribes opening areas and requires both MV and NV

9 © 2009 Trane

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
6 2 7 Dynamic reset

10 © 2009 Trane


6.2.2 Zone Calculations design

1. Calculate breathing-zone outdoor airflow, using Table
6-1
6 1 rates (Rp cfm/per Ra cfm/ft2)
cfm/per,
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.
3 Calculate zone outdoor airflow
Voz = Vbz/Ez (Eq 6-2)

11 © 2009 Trane


• 6.2.7
6 2 7 Dynamic reset

12 © 2009 Trane


6.2.3 Single-Zone Systems
One recirculating air handler
serves one zone

EA RA

OA SA
(Vot) (Vpz)
zone

13 © 2009 Trane

6.2.3 Single-Zone Systems design

For single-zone systems
– 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
g p y
assume peak zone population
– Zone ventilation efficiency (Evz = Voz-actual/Voz-
design) is probably less than 1.0 during operation

14 © 2009 Trane


6.2.3 Single-Zone Systems operation

• That’s it for design, but does 62.1-2010 allow
intake i fl
i t k airflow to vary during operation?
t d i ti ?
• 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 CO2-based reset
Bio-effluent based
– Read Journal articles for “how-to” ideas

15 © 2009 Trane

operation
Dynamic Reset Approaches
• Section 6.2.7 allows dynamic reset of OA intake
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
y , , y
in some VAV systems
– For multiple-zone systems, use system-level controls,
which can be combined with zone-level DCV
• Some examples …

16 © 2009 Trane


single-zone system operation
CO2-based Zone-DCV
Now CO2 varies,
4800 so DCV isn’t as easy 1200
CO2 varies
62.1 2007
62.1-2007
(Std 62.1-2007)
breathing zone OA, Vbz
z

differential CO2, ppm
4000 1000

Vbz = 3900 cfm
3200 800

CO2 = 700 ppm
2400 (Std 62-2001) 600
Vbz = 2190 cfm
1600 400
b

800 lecture classroom 200
Az = 4000 ft2
design Pz = 260 p
0 0
0 40 80 120 160 200 240
zone population, Pz

© 2005 American Standard Inc.

17 © 2009 Trane

one way to implement zone-DCV … operation
62.1 User’s Manual
• Find breathing zone OA (Vbz) range
Vbz
Vb = (R  P + R  A )
(Rp Pz Ra Az)
Vbz-des = (7.5  260 + 0.06  4000)/1.0 = 2190 cfm
Vbz-min = (7.5  0 + 0.06  4000)/1.0 = 240 cfm
• Find target indoor CO2 (Crz) range
Crz – Co = N/(Vbz/Pz)
Crz-des – Co = 0.0105/(2190 cfm/260 p)  1250 ppm
Crz-min – Co = 0.000350 – 0.000350  0 ppm
• 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

18 © 2009 Trane


zone DCV for single-zone systems operation

The Controller
2190

Vbz
(cfm)

240

0 1250
Crz - Co (CO2, ppm)

19 © 2009 Trane

zone DCV for single-zone systems operation
Controller adjusts Vbz,
hing zone OA, Vbz (=Ez*Vot)

4800 based on sensed CO2 1200
differential CO2, ppm

4000 1000

CO2
3200 800

2400 600

1600 Vbz 400
breath

800 lecture classroom 200
Az = 4000 ft2
design Pz = 260 p
0 0
0 40 80 120 160 220 240
zone population, Pz

© 2005 American Standard Inc.

20 © 2009 Trane



• 6.2.7
6 2 7 Dynamic reset

21 © 2009 Trane

6.2.4 100% OA Systems design

One non-recirculating air handler
serves many zones

EA Voz

OA zone
(Vot) SA
CA
RA

Voz

zone
SA

RA

22 © 2009 Trane


6.2.4 100% OA Systems design

For 100% OA systems
– 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
g p y
assume peak zone population in each zone
– Zone ventilation efficiency (Evz = ΣVoz-actual/ΣVoz-
design) is probably less than 1.0 during operation

23 © 2009 Trane

6.2.4 100% OA Systems operation

• That’s it for design but does 62.1-2007 allow
intake i fl
i t k airflow to vary during operation?
t d i ti ?
• 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 zones i l d pressure-independent d
include i d d t dampers
– DCV zones include DCV sensors and controls
– The 100% OA unit includes VAV controls

24 © 2009 Trane



• 6.2.7
6 2 7 Dynamic reset

25 © 2009 Trane

6.2.5 Multiple-Zone Systems
One recirculating air handler
serves many zones
RA

EA
Vpz
space

OA
(Vot) SA
(Vps)

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

26 © 2009 Trane


design
6.2.5 Multiple-Zone Systems

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

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. Find
6 Fi d system ventilation efficiency, E
t til ti ffi i Ev
Calculate Ev per equations (App A)
7. Find outdoor air intake flow, Vot:
Vot = Vou/Ev (6-8)

27 © 2009 Trane

6.2.5 Multiple-Zone Systems design

4. Find primary outdoor air fraction for each zone or
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
Vpz design
 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”

28 © 2009 Trane



5. Find uncorrected outdoor airflow
Vou = D*(R P ) + (R A )
V (Rp×Pz) (Ra×Az) (Eq 6-6)
(E 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
uncorrected outdoor airflow

29 © 2009 Trane


6. Find system ventilation efficiency
– Fi t find average outdoor air f ti (Xs) using
First, fi d td i fraction (X ) i
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)
Ev = min(Evz) (Eq A-8)
Note:
– Lowest Evz defines the “critical zone” for ventilation

30 © 2009 Trane



7. Find outdoor air intake flow
Vot Vou/Ev
V t = V /E (Eq 6-8)
(E 6 8)

Note:
– Compared to 2001, the 2010 rates and equations
reduce intake airflow (Vot) for many systems

31 © 2009 Trane


• 6.2.7
6 2 7 Dynamic reset

32 © 2009 Trane


Multiple-Zone Systems operation

• That’s it for MZS design but can intake flow vary
during
d i operation?
ti ?
• 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
• But how do you do it in a VAV system?

33 © 2009 Trane

Dynamic Reset Approaches operation

• Already reviewed for single zone and 100% OA
• 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
population
– Use system-level DCV of some sort
 Approaches not well-known, but hopefully Dr. Lau’s
research addresses this

34 © 2009 Trane


Ventilation Reset Control operation

• VRC resets system-level outdoor air intake flow
(Vot) t
(V t) at part l d conditions by:
t load diti b
– 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
• Here’s an example building using one possible
VRC approach

35 © 2009 Trane

VRC w/o Zone-Level DCV design

Vot
req’d
@ design
Single Supply
Single-Supply VAV System: Ventilation Design
population Pz 140 140 260 260 5 40 8, 810
prim airflow Vpz 6,500 6,700 5,500 7,900 500 1,700
min expect Vpzm 4,000 4,000 4,000 4,000 300 1,300
vent rate Vbz 1,880 1,880 2,190 2,190 85 760
vent fract Zpz 0.470 0.470 0.548 0.548 0.283 0.585
Ventilation design - For each zone use: Then, find:
Pz = peak zone population Vou = D*Rp*Pz + Ra*Az (5)
Vpz = peak primary airflow D = Ps/Pz = 550/845 = 0.65
Vpzm = minimum expected Vpz @ design = 0.65*7,130 + 1,860 = 6,500
Then,
Then find: Ev = min(Evz) (6)
Vbz = Rp*Pz + Ra*Az (1) Vps = LDF*ΣVpz
Ez = design zone air dist eff (2) = 0.7*28,800 = 20,200
Voz = Vbz/Ez (3) Xs = Vou/Vps
Zpz = Voz/Vpzm = Vbz/(Ez*Vpzm) (4) = 6,500/20,200 = 0.322
Evz = 1+ Xs – Zpz
For the system use: = 1 + 0.322 – 0.585 = 0.738
Ps = highest system population = 550 = min(Evz) = 0.738
LDF= load diversity factor = 0.7 Vot = Vou/Ev = 6,500/0.738 = 8,810 (7)
36 © 2009 Trane


VRC w/o Zone-Level DCV operation

Vot Vot
req’d req’d
@ design (current)
Single Supply
Single-Supply VAV System: 100% Thermal Load (2:00 pm Friday perhaps)
Friday,
population Pz 140 140 260 260 5 40 8, 810 8, 390
prim airflow Vpz 4,960 5,000 4,000 4,000 500 1,700
vent rate Vbz 1,880 1,880 2,190 2,190 85 760
vent fraction Zdz 0.379 0.376 0.548 0.548 0.170 0.447

Operation w/o DCV: For each zone use: Now, controls calculate:
Pz = peak zone population (entry) Vou = D*Rp*Pz + Ra*Az (5)
Then, controls determine or calculate: D = Ps/Pz = 550/845 = 0.65
Vpz = current primary airflow (sensed) = 0.65*7,130 + 1,860 = 6,500
Vbz = Rp*Pz + Ra*Az (calc or entry) (1)
Rp Pz Ra Az Ev = min(Evz) (6)
Ez = current value (2) Vps = Vpz
Voz = Vbz/Ez (3) = 20,200
Zpz = Voz/Vpz (4) Xs = Vou/Vps
= 6,500/20,200 = 0.322
Evz = 1+ Xs – Zpz
37 © 2009 Trane


Vot Vot
req’d req’d
@ design (current)
Single Supply
Friday,
population Pz 140 140 260 260 5 40 8, 810 8, 390
prim airflow Vpz 4,960 5,000 4,000 4,000 500 1,700
vent rate Vbz 1,880 1,880 2,190 2,190 85 760
vent fraction Zdz 0.379 0.376 0.548 0.548 0.170 0.447
Vot-actual is less
Operation w/o DCV: For each zone use: Now, controls calculate: than Vot-design
Pz = peak zone population (entry) Vou = D*Rp*Pz + Ra*Az (5)
Then, controls determine or calculate: D = Ps/Pz = 550/845 = 0.65
Vpz = current primary airflow (sensed) = 0.65*7,130 + 1,860 = 6,500
Vbz = Rp*Pz + Ra*Az (calc or entry)w/o DCV Ev = min(Evz)
Rp Pz Ra Az VRC (1) reduces (6)
Ez = current value required Vot, even at Vpz
(2) Vps =
Voz = Vbz/Ez (3) = 20,200
Zpz = Voz/Vpz 100%(4)thermal load:= Vou/Vps
Xs
Ev-actual ≥ Ev-design = 6,500/20,200 = 0.322
Evz = 1+ Xs – Zpz
38 © 2009 Trane



Vot Vot
req’d req’d
@ design (current)
Single Supply
Friday,
population Pz 140 140 260 260 5 40 8, 810 8, 390
prim airflow Vpz 4,960 5,000 4,000 4,000 500 1,700
vent rate Vbz 1,880 1,880 2,190 2,190 85 760
vent fraction Zpz 0.379 0.376 0.548 0.548 0.170 0.447

Single-Supply VAV System: 90% Thermal Load (1:00 pm Monday, perhaps)
population Pz 140 140 260 260 5 40 8,810 7,780
prim airflow Vpz 4,000 3,700 4,200 4,300 300 1,700
vent rate Vbz 1,880 1,880 2,190 2,190 85 760
vent fraction Zpz 0 470 0 508 0 521 0 509 0 283 0 447
0.470 0.508 0.521 0. 0.283 0.447

Now, controls determine or calculate: VRC w/o DCV reduces
Vou = D*Rp*Pz + Ra*Az = 6,500 required Vot even more
Vpz = (sensed)
Vps = Vpz = 18,200 at lower thermal loads:
Xs = Vou/Vps = 6,500/18,200 = 0.357 Ev-actual >> Ev-design
Ev = 1 + 0.357 – 0.521 = 0.836
Vot = Vou/Ev = 6,500/0.836 = 7,780
39 © 2009 Trane

Dynamic Reset Approaches operation

• Already reviewed for single zone and 100% OA
• 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
population
– Use system-level DCV of some sort
 Approaches not well-known, but hopefully Dr. Lau’s
research addresses this

40 © 2009 Trane


VRC with Zone-Level DCV operation

• VRC resets system-level outdoor air intake flow
(Vot) t
(V t) at part l d conditions by:
t load diti b
– 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
• Here’s the same example building using the same
VRC approach, but with various “zone types”
including both non-DCV and DCV zones

41 © 2009 Trane

VRC w/Zone-Level DCV operation

• Defining zone types
– Z
Zones without DCV
ith t
 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
 “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)

42 © 2009 Trane


VRC w/ Zone-Level DCV design

Vot
NON NON CO2 NON NON EST req’d
@ design
Single Supply
Single-Supply VAV System: Design Ventilation
population Pz 140 140 260 260 5 40 8, 810
prim airflow Vpz 6,500 6,700 5,500 7,900 500 1,700
min expect Vpzm 4,000 4,000 4,000 4,000 300 1,300
vent rate Vbz 1,880 1,880 2,190 2,190 85 760 DCV: No impact
vent fract Zpz 0.470 0.470 0.548 0.548 0.283 0.585 on Vot-design
Design ventilation: For each zone use: Then, find:
Pz = peak zone population Vou = D*Rp*Pz + Ra*Az (5)
Vpz = peak primary airflow D = Ps/Pz = 550/845 = 0.65
Vpzm = minimum expected Vpz @ design = 0.65*7,130 + 1,860 = 6,500
Then,
Then find: Ev = min(Evz) (6)
Vbz = Rp*Pz + Ra*Az (1) Vps = LDF*ΣVpz
Ez = design zone air dist eff (2) = 0.7*28,800 = 20,200
Voz = Vbz/Ez (3) Xs = Vou/Vps
Zpz = Voz/Vpzm = Vbz/(Ez*Vpzm) (4) = 6,500/20,200 = 0.322
Evz = 1+ Xs – Zpz
43 © 2009 Trane

VRC w/ Zone-Level DCV operation

Vot Vot
NON NON CO2 NON NON EST req’d req’d
@ design (current)
Single Supply
Friday,
population Pz 140 140 ??? 260 5 0 8, 810 8, 390
prim airflow Vpz 4,960 5,400 4,000 4,000 500 1,300 8, 030
vent rate Vbz 1,880 1,880 1,300 2,190 85 360

For each NON-DCV zone use: Now, for system:
Pz = peak zone population (entry) Vou = D*NONRp*Pz + NONRa*Az (5)
Vbz = Rp*Pz + Ra*Az (entry) + ESTRp*Pz + ESTRa*Az + CO2Vbz
For each EST-DCV zone: Ps = highest system population = 550
Pz = estimated population (sensed) D = Ps/Pz-peak = 550/845 = 0.65
Vbz Rp*Pz Ra*Az
Vb = R *P + R *A (calc)
( l ) = 0.65*4,780 + 1,260 + 0 + 360 + 1,300
*
For each CO2-DCV zone use: = 6,030
Vbz = f (ΔCO2) (sense & calc) Ev = min(Evz) (6)
For each zone, controls determine: Vps = Vpz = 20,200 (calc)
Vpz = current zone primary (sensed) Xs = Vou/Vps = 6,030/20,200 = 0.299
Vbz = current reqmt (entry or calc) (1) Evz = 1 + Xs – Zpz
Ez = current value (2) = 1 + 0.299 – 0.548 = 0.751
Voz = Vbz/Ez (3) Vot = small(Vou/Ev or Vot-des) (7)
Zpz = Voz/Vpz (4) = 6,030/0.751 = 8,030
44 © 2009 Trane



Vot Vot
@ design (current)
Single Supply
Friday,
population Pz 140 140 ??? 260 5 0 8, 810 8, 390
prim airflow Vpz 4,960 5,400 4,000 4,000 500 1,300 8, 030
vent rate Vbz 1,880 1,880 1,300 2,190 85 360

For each NON-DCV zone use: Now, for system: VRC w/DCV
Pz = peak zone population (entry) reduces Vot-actual
Vou = D*NONRp*Pz + NONRa*Az (5)
Vbz = Rp*Pz + Ra*Az (entry) + ESTRp*Pz + ESTRa*Az + CO2Vbz
For each EST-DCV zone: Ps = highest system population = 550
Pz = estimated population (sensed) D = Ps/Pz-peak = 550/845 = 0.65
Vbz Rp*Pz Ra*Az
Vb = R *P + R *A (calc)
( l ) = 0.65*4,780 + 1,260 + 0 + 360 + 1,300
*
For each CO2-DCV zone use: = 6,030
Vbz = f (ΔCO2) (sense & calc) Ev = min(Evz) (6)
For each zone, controls determine: Vps = Vpz = 20,200 (calc)
Vpz = current zone primary (sensed) Xs = Vou/Vps = 6,030/20,200 = 0.299
Vbz = current reqmt (entry or calc) (1) Evz = 1 + Xs – Zpz
Ez = current value (2) = 1 + 0.299 – 0.548 = 0.751
Voz = Vbz/Ez (3) Vot = small(Vou/Ev or Vot-des) (7)
Zpz = Voz/Vpz (4) = 6,030/0.751 = 8,030
45 © 2009 Trane


– For design, note:
 D = P /ALLP
Ps/ Pz-peak, bk because occupant diversity
t di it
distributes 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)
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

46 © 2009 Trane



Vot Vot
@ design (current)
Single Supply
Single-Supply VAV System: 100%Thermal Load (2:00 pm Friday perhaps)
Friday,
population Pz 140 140 ??? 260 5 0 8, 810 8, 030
prim airflow Vpz 4,960 5,400 4,000 4,000 500 1,300
vent rate Vbz 1,880 1,880 1,300 2,190 85 360

Single-Supply VAV System: 90% Thermal Load (1:00 pm Monday, perhaps)
population Pz 140 140 ??? 260 5 0 8,810 7,780
prim airflow Vpz 4,000 3,700 4,200 4,300 300 1,700 7,440
vent rate Vbz 1,880 1,880 1,300 2,190 85 360
vent fraction Zpz 0 470 0 508 0 521 0 509 0 283 0 447
0.470 0.508 0.521 0. 0.283 0.447

Now: VRC with DCV reduces
Vou = 6,030
Vps = Vpz = 18,200 Vot-actual more, saves
Xs = 6,030/18,200 = 0.331 more energy
Ev = 1 + 0.331 – 0.521 = 0.810
Vot = Vou/Ev = 6,030/0.810 = 7,440

47 © 2009 Trane

Implementation

• For VRC alone or combined with zone-level DCV,
design
d i usually includes:
ll i l d
– 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:
– 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

48 © 2009 Trane


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):
 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)

49 © 2009 Trane

Thanks

Any questions?

Dennis Stanke
dstanke@trane.com

50 © 2009 Trane


Standard 62.1: A VAV Dynamic Reset Approach

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Standard 62.1: A VAV Dynamic Reset Approach