ventilation requirements & dynamic reset...intake flow using either vrp or iaqp 6.2 ventilation...
TRANSCRIPT
Multiple-Zone Ventilation© 2007 American Standard Inc. All rights reserved
1
© 2006 American Standard Inc.
complying with Std 62.1-2007:
Ventilation Requirements & Dynamic Reset
complying with Std 62.1-2007:
Ventilation Requirements & Dynamic Reset
Dennis Stanke
February 2008
© 2008 Trane
ASHRAE Standard 62.1
What Is It?
� Title: “Ventilation for Acceptable Indoor Air Quality”
� Purpose: “… to specify minimum ventilation rates and other measures intended to provide indoor air quality that is acceptable to human occupants and that minimizes adverse health effects.”
� Scope: All commercial, institutional, and high-rise residential buildings
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ASHRAE Standard 62.1
Why Care?
� The Std 62.1 Ventilation Rate Procedure (VRP) is now the basis for both US ventilation model codes (UMC and IMC)
� VRP more stringent than some local codes(helps establish “standard-of-care”)
� VRP less stringent than some local codes(helps designer pursue code variance)
� VRP is a prerequisite for any LEED credits
© 2008 Trane
what does Std 62.1 require?
Must Comply With …
� General requirements (Sect 4 and 5)
� To reduce generation of indoor contaminants and introduction of outdoor contaminants
� Ventilation requirements (Sect 6)
� To dilute and remove indoor contaminants
� Construction, startup, operation and maintenance requirements (Sect 7 and 8)
� To assure installation/operation as designed
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ventilation requirements
6.0 Procedures
� 6.1 General. For mechanical systems, find OA intake flow using either VRP or IAQP
� 6.2 Ventilation Rate Procedure
� Prescribes minimum rates for “typical” zones
� Prescribes calculations for minimum intake rate
� 6.3 IAQ Procedure
� It’s performance-based
� Must ventilate as necessary to achieve specific concentration targets for contaminants of concern
© 2008 Trane
Std 62.1-2007 Section 6.2
Ventilation Rate Procedure
� 6.2.1 Outdoor air treatment
� 6.2.2 Zone calculations
� 6.2.3 Single zone systems (intake calculations)
� 6.2.4 100% OA systems (intake calculations)
� 6.2.5 Multiple-zone systems (intake calculations)
� 6.2.6 Design for varying operating conditions
� 6.2.7 Dynamic reset
� 6.2.8 Exhaust ventilation
� 6.2.9 Ventilation in smoking areas
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Std 62.1-2007 Section 6.2.2
Zone Calculations
1. Calculate breathing-zone outdoor airflow, using Table 6-1 rates (cfm/per, cfm/ft2)
Vbz = Rp × Pz + Ra × Az (6-1)
2. Find zone air distribution effectiveness, Ez
Look up Ez (typically 1.0) (Tab 6-2)
3. Calculate zone outdoor airflow
Voz = Vbz/Ez (6-2)
© 2008 Trane
6.2.2 zone calculations
Minimum Ventilation Rates
Table 6-1: Minimum breathing-zone rates for 63 categories
Office 20 0.0 5.0 0.06
Classroom (ages 5-8) 15 0.0 10.0 0.12
Lecture classroom 15 0.0 7.5 0.06
Retail sales 0 0.3 7.5 0.12
Auditorium 15 0.0 5.0 0.06
Std 62-2001 Std 62.1-2007
Rp Ra Rp RaOccupancy category cfm/p cfm/ft² cfm/p cfm/ft²
Prescribes both per-person, per-area rates
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Office (5p) 100 20.0 85 17.0
Classroom (ages 5-8) (25p) 375 15.0 370 15.0
Lecture classroom (65p) 975 15.0 550 8.5
Retail sales (20p) 300 15.0 270 14.0
Auditorium (150p) 2250 15.0 810 5.4
Occupancy category(default density/1000 ft²)
Std 62-2001
Vbzcfm
Effectivecfm/p
6.2.2 zone calculations
Effective Minimum Rates
Std 62.1-2007
OA flow rates go down in 70% of occupancies
Vbzcfm
Effectivecfm/p
© 2008 Trane
Std 62.1-2007 Section 6.2
Ventilation Rate Procedure
� 6.2.1 Outdoor air treatment
� 6.2.2 Zone calculations
� 6.2.3 Single zone systems (intake calculations)
� 6.2.4 100% OA systems (intake calculations)
� 6.2.5 Multiple-zone systems (intake calculations)
� 6.2.6 Design for varying operating conditions
� 6.2.7 Dynamic reset
� 6.2.8 Exhaust ventilation
� 6.2.9 Ventilation in smoking areas
Multiple-Zone Ventilation© 2007 American Standard Inc. All rights reserved
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© 2008 Trane
Single-Zone CV System
SAOA
RAEA
space
© 2008 Trane
Std 62.1-2007 Section 6.2.3
Single-Zone Systems
For single-zone systems
� Complete first three steps for zone
� For system, find outdoor air intake flow, Vot:
Vot = Voz (6-3)
Compared to 62.1-2001, reduced zone airflow reduces design intake OA in many
single-zone systems
But … intake flow (Vot) equals zone OA (Voz), that is, no credit available for system
occupant diversity
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six-zone school example
Design Zone Calculations Example School Rp Pz Ra Az Ez Voz
cfm/per people cfm/ft2 ft2 -- cfm
South classrms (9+) 10 140 0.12 4,000 1.0 1,880
West classrms (9+) 10 140 0.12 4,000 1.0 1,880
North lecture class 7.5 260 0.06 4,000 1.0 2,190
East lecture class 7.5 260 0.06 4,000 1.0 2,190
Interior offices 5 5 0.06 1,000 1.0 85
North art classrm 10 32* 0.18 2,000 1.0 680
* Average (81% of 40 peak)
Step 1: Vbz = Rp*Pz + Ra*AzStep 2: Look up EzStep 3: Voz = Vbz/Ez
Step 7: Vot = ΣΣΣΣVoz
© 2008 Trane
Single-Zone Systems
� OK, for design.
� But … What about operation?
� Does 62.1-2007 allow intake airflow to vary during operation?
� Of course.
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operation for varying conditions
6.2.7 Dynamic Reset
Optional controls may reset zone or system settings based on changing conditions, including:
� Variations in occupancy (TOD, OCC, COU) or ventilation airflow (CO2)
� May reset zone OA flow in any system
� Variations in efficiency
� May reset system OA intake in VAV systems
� Reset VAV box minimums when economizing
� May reset minimums in some VAV-reheat systems
Std 62.1 allows zone-level dynamic reset based on “demand” (Demand Controlled Ventilation: DCV)
part load
© 2008 Trane
Single-Zone CV System
SAOA
RAEA
space
Variations in occupancy:
� Time-of-day (TOD) schedule
� Occupant count/detection
� CO2-based DCV
Variations in occupancy:
� Time-of-day (TOD) schedule
� Occupant count/detection
� CO2-based DCV
part load
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6.2.7 dynamic reset
Variations in Occupancy
May reset zone OA requirement to match it to current population (that is, demand), based on:
� Time-of-day (TOD) schedules… number of people expected in zone at a given time
� On/off occupancy (OCC) sensors … design population or no people in zone
� People-counters (COU)… “accurate” real-time count of people in zone
� Carbon dioxide sensors (CO2)… estimate of OA flow (cfm/person) within zone
part load
© 2008 Trane
CO2-based demand-controlled ventilation
How Concentrations Work
Ci = Co + N/Vo
where
Co = CO2 concentration inoutdoor air, ppm
N = CO2 generation rate,cfm/person
Vo = outdoor airflow rate,cfm/person
� When OA flow Vo = 15 cfm/p, 80% of visitors deem human bioeffluent odors as acceptable
� Sedentary people generate CO2
at about 0.0105 cfm/p
� If Co = 300 ppm,Ci = 300 + 10500/15
= 1000 ppm
� So, maintaining Ci – Co = 700 ppm indirectly maintains to 15 cfm/p
At Steady State
part load
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40 80
800
1600
2400
3200
4000
zone population, Pz
breath
ing zone O
A, Vbz
120 160 220 240
diffe
rentia
l CO
2 , ppm
200
400
600
800
1000
1200
000
4800
Now ∆∆∆∆CO2 varies,so DCV isn’t as easy
CO2-based DCV
ASHRAE Std 62.1-2007
Fixed ∆∆∆∆CO2 setpoint no longer works as well
62.1-2007
© 2005 American Standard Inc.
What about CO2 levels?
∆∆∆∆CO2 = 700 ppm(Std 62-2001)
∆∆∆∆CO2 varies(Std 62.1-2007)
Vbz = 2190 cfm
Vbz = 3900 cfm
lecture classrmsdesign Pz = 260 p
part load
© 2008 Trane
How to Use CO2?
� Reminder: This is zone-level DCV for a single-zone system
� Here’s some example approaches:
� Follow the Users Manual
� Modify the UM using a minimum non-zero population
� Use a fixed ∆CO2 set point combined with a minimum OA intake (Vot) setting
part load
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one way to implement SZS DCV …
62.1 User’s Manual
� Find breathing zone OA (Vbz) range
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) range
Crz = Co + N/(Vbz/Pz)Crz-des = 0.000350+0.0105/(2190 cfm/260 p) � 1600 ppmCrz-min = 0.000350 � 350 ppm
� The Controller: Set Vot (= Vbz/Ez) signal range to match Crz range
� Adjust OA damper to deliver Vbz-des at max signal, Vbz-min at min signal
part load
© 2008 Trane
DCV for single-zone CV systems
62.1 User’s Manual
Crz (CO2, ppm)
Vbz(cfm)
240
2190
350 1600
The Controller
part load
Multiple-Zone Ventilation© 2007 American Standard Inc. All rights reserved
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© 2008 Trane
DCV for single-zone CV systems
62.1 User’s Manual
� Using this controller, sensing CO2 and adjusting OA damper position, results in Vot equal to or greater than the required minimum Vot
� Incidentally, to make the following plots, at each zone population, we assumed a zone-CO2 level (Crz-guess), then found breathing zone OA (Vbz) needed using The Controller, solved for Crz at that Vot, and compared. We repeated the process until Crz matched Crz-guess.
� Assume Cr-guess
� Vot = (1.56 � (Crz-guess – 350) + 240)/1.0
� Crz = 350 + Pz � k � m / Vbz
� Repeat until Crz = Crz-guess
part load
© 2008 Trane
DCV for single-zone CV systems
62.1 User’s Manual
40 80
800
1600
2400
3200
4000
zone population, Pz
120 160 200 240
indoor C
O2 , C
rz, p
pm
300
600
900
1200
1500
1800
000
4800
Vot-min
Vot-design
outd
oor-a
ir inta
ke flo
w, Vot, cfm
part load
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another way to implement SZS DCV
62.1 UM Modified
zone population, Pz
300
600
900
1200
1500
1800
0
Vot-design
Vot-min
Cs-design
Pz-min
Cs-min
indoor C
O2 , C
rz, p
pm
outd
oor-a
ir inta
ke flo
w, Vot, cfm
40 80 120 160 200 2400
800
1600
2400
3200
4000
0
4800
part load
© 2008 Trane
another way to implement SZS DCV
Single CO2 Setpoint
zone population, Pz
300
600
900
1200
1500
1800
0
Cs-min
Vot-min
indoor C
O2 , C
rz, p
pm
outd
oor-a
ir inta
ke flo
w, Vot, cfm
40 80 120 160 200 2400
800
1600
2400
3200
4000
0
4800
part load
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Implementation Issues
� Sensor location
� Wall-mounted (in the breathing zone)
� Duct-mounted (not so good)
� Economizer operation may override DCV minimum OA intake
� Don’t forget about building pressure control! Can only reduce intake so much.
part load
© 2008 Trane
DCV approaches
Resources
� ASHRAE Journal
� May 2006: CO2-based DCV Using 62.1-2004
� Dec 2006: System Operation: Dynamic Reset Options
� Std 62.1-2007 User’s Manual, Appendix A (for single-zone systems only)
part load
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Std 62.1-2007 Section 6.2
Ventilation Rate Procedure
� 6.2.1 Outdoor air treatment
� 6.2.2 Zone calculations
� 6.2.3 Single zone systems (intake calculations)
� 6.2.4 100% OA systems (intake calculations)
� 6.2.5 Multiple-zone systems (intake calculations)
� 6.2.6 Design for varying operating conditions
� 6.2.7 Dynamic reset
� 6.2.8 Exhaust ventilation
� 6.2.9 Ventilation in smoking areas
© 2008 Trane
100% OA Systems
CA
OA
EAEA
space
space
SA
RA
SA
RA
design
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Std 62.1-2007 Section 6.2.4
100% OA Systems
For 100% OA systems
� Complete first three steps for zone
� For system, find outdoor air intake flow, Vot:
Vot = ΣΣΣΣVoz (6-4)
Compared to 62.1-2001, reduced zone airflow reduces OA energy in many
100% OA systems
But … intake flow (Vot) must be sum-of-zone OA at design (Voz), that is, no credit available for system occupant diversity
design
© 2008 Trane
system calculations
100% OA SystemsExample School Rp Pz Ra Az Ez Voz
cfm/per people cfm/ft2 ft2 -- cfm
South classrms (9+) 10 140 0.12 4,000 1.0 1,880
West classrms (9+) 10 140 0.12 4,000 1.0 1,880
North lecture class 7.5 260 0.06 4,000 1.0 2,190
East lecture class 7.5 260 0.06 4,000 1.0 2,190
Interior offices 5 5 0.06 1,000 1.0 85
North art classrm 10 32* 0.18 2,000 1.0 680
OA intake flow (Vot) 8,900
*Average (81% of 40) Step 7: Vot = ΣΣΣΣVoz
Step 1: Vbz = Rp*Pz + Ra*AzStep 2: Look up EzStep 3: Voz = Vbz/Ez
design
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100% OA Systems
� OK, for design.
� But … What about operation?
� For CV AHU, dynamic reset (zone level DCV) can’t be implemented – no dampers
� For VAV AHU, it seems reasonable to apply single-zone DCV concepts to find and control Voz zone-by-zone
© 2008 Trane
100% OA Systems - CV
CA
OA
EAEA
space
space
SA
RA
SA
RA
No DCV possible
part load
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100% OA Systems - VAV
CA
OA
EAEA
space
space
SA
RA
SA
RA
VFD
VFD
CO2
OCC
DCV at zones resets Voz,AHU control resets Vot at
system
part load
© 2008 Trane
DCV for 100% OA systems
100% OA Systems - VAV
� If you calculate Voz set point
� For TOD, OCC, and COU zones, find Voz = Rp*Pz + Ra*Az using estimated or actual population
� For CO2 zones, find Voz = [Rp*Pz + Ra*Az]/Ev, using sensed CO2 and differential controller
� If you don’t calculate Voz
� For occ/unocc TOD, OCC zones, simply open/close damper – we don’t know Pz so we can’t modulate
� For estimated pop (TOD, COU) and CO2 zones, use “trim/respond” logic to modulate damper
part load
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100% OA Summary
� To comply at design, Vot = Voz. No diversity credit possible … must assume full system population to size AHU
� Optional control at part load,
� For CV OA AHU, no way to use DCV in zones … nothing to adjust!
� For VAV OA AHU, use zone DCV to estimate current Voz and adjust zone damper
� Control OA AHU to modulate intake airflow, based on duct pressure or ventilation damper positions (Std 90.1 might require this)
© 2008 Trane
Std 62.1-2007 Section 6.2
Ventilation Rate Procedure
� 6.2.1 Outdoor air treatment
� 6.2.2 Zone calculations
� 6.2.3 Single zone systems (intake calculations)
� 6.2.4 100% OA systems (intake calculations)
� 6.2.5 Multiple-zone systems (intake calculations)
� 6.2.6 Design for varying operating conditions
� 6.2.7 Dynamic reset
� 6.2.8 Exhaust ventilation
� 6.2.9 Ventilation in smoking areas
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Multiple-Zone Systems
SAOA
RA
EA
space
space
© 2008 Trane
Std 62.1-2007 Section 6.2.5
MZ Recirculating Systems
For multiple-zone recirculating systems, complete first three steps for zone, then:
4. Find primary (or discharge) outdoor air fraction
Zp = Voz/Vpz-min (6-5)
5. Find uncorrected outdoor airflow
Vou = D*ΣΣΣΣ(Rp×Pz) + ΣΣΣΣ(Ra×Az) (6-6)
6. Find system ventilation efficiency
Look up default Ev, or (Table 6-3)
Or, calculate Ev per equations (App A)
7. Find outdoor air intake flow, Vot:
Vot = Vou/Ev (6-8)
design
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Std 62.1-2007 Section 6.2.5
MZ Recirculating Systems
For multiple-zone recirculating systems, complete first three steps for zone, then:
4. Find primary (or discharge) outdoor air fraction
Zp = Voz/Vpz-min (6-5)
5. Find uncorrected outdoor airflow
Vou = D*ΣΣΣΣ(Rp×Pz) + ΣΣΣΣ(Ra×Az) (6-6)
6. Find system ventilation efficiency
Look up default Ev, or (Table 6-3)
Or, calculate Ev per equations (App A)
7. Find outdoor air intake flow, Vot:
Vot = Vou/Ev (6-8)
Compared to 62.1-2001, reduced zone airflow (Voz) reduces design OA (Vot) and
energy in many multiple-zone systems
Compared to single-zone and 100% OAsystems, accounting for occupant diversity
reduces design OA (Vot) and energy
design
© 2008 Trane
six-zone school example
Zone-Level Calculations Example School Rp Pz Ra Az Ez Voz
cfm/per people cfm/ft2 ft2 -- cfm
South classrms (9+) 10 140 0.12 4,000 1.0 1,880
West classrms (9+) 10 140 0.12 4,000 1.0 1,880
North lecture class 7.5 260 0.06 4,000 1.0 2,190
East lecture class 7.5 260 0.06 4,000 1.0 2,190
Interior offices 5 5 0.06 1,000 1.0 85
North art classrm 10 32* 0.18 2,000 1.0 680
* Average (81% of 40 peak)
Step 1: Vbz = Rp*Pz + Ra*AzStep 2: Look up EzStep 3: Voz = Vbz/Ez
design
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multiple-zone system calculations
Single-Path VAV: Calc EvExample School Pz Vdz Voz Vdzm Zd Evz
people cfm cfm cfm -- (5,6,7)
South classrms (9+) 140 6,500 1,880 4,000 0.47
West classrms (9+) 140 6,700 1,880 4,000 0.47
North lecture class 260 5,500 2,190 4,000 0.55
East lecture class 260 7,900 2,190 4,000 0.55
Interior offices 5 500 85 300 0.28
North art classrm 32* 1,700 680 1,300 0.52
* Average (81% of 40 peak)
Step 4: Find outdoor air fraction for each zone:Zd = Voz/Vdzm = 1880/4000 = 0.47
design
© 2008 Trane
multiple-zone system calculations
Single-Path VAV: Calc EvExample School Pz Vdz Voz Vdzm Zd Evz
people cfm cfm cfm -- (5,6,7)
South classrms (9+) 140 6,500 1,880 4,000 0.47 --
West classrms (9+) 140 6,700 1,880 4,000 0.47 --
North lecture class 260 5,500 2,190 4,000 0.55 --
East lecture class 260 7,900 2,190 4,000 0.55 --
Interior offices 5 500 85 300 0.28 --
North art classrm 32* 1,700 680 1,300 0.52 --
Uncorrected OA flow -- -- -- Step 5 Vou 6,500
* Average (81% of 40 peak)
Step 5a: Find occupant diversity:D = Ps/ΣΣΣΣPz = 550/837 = 0.66
Step 5b: Find uncorrected outdoor air intake:Vou = D*ΣΣΣΣ(Rp*Pz) + ΣΣΣΣ(Ra*Az)
= 0.66*7,000 + 1,900 = 6,500 cfm
design
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multiple-zone system calculations
Single-Path VAV: Calc EvExample School Pz Vdz Voz Vdzm Zd Evz
people cfm cfm cfm -- (5,6,7)
South classrms (9+) 140 6,500 1,880 4,000 0.47 0.85
West classrms (9+) 140 6,700 1,880 4,000 0.47 0.85
North lecture class 260 5,500 2,190 4,000 0.55 0.77
East lecture class 260 7,900 2,190 4,000 0.55 0.77
Interior offices 5 500 85 300 0.28 1.04
North art classrm 32* 1,700 680 1,300 0.52 0.80
Uncorrected OA flow -- -- -- Step 5 Vou 6,500
Uncorrected OA frac Step 6 Xs 0.32
Sys vent eff -- -- -- Ev 0.77
* Average (81% of 40 peak)
Step 6a: Find system primary airflow:Vps = LDF*ΣΣΣΣVpz = 0.70*28,800 = 20,200
Step 6b: Find average outdoor air fraction:Xs = Vou/Vps = 6,500/20,200 = 0.32
Step 6c: Find ventilation efficiency for each zone:Evz1 = 1+Xs–Zd = 1+0.32–0.47 = 0.85
Step 6d: Find system ventilation efficiencyEv = min(Evz) = 0.77
design
© 2008 Trane
multiple-zone system calculations
Single-Path VAV: Calc EvExample School Pz Vdz Voz Vdzm Zd Evz
people cfm cfm cfm -- (5,6,7)
South classrms (9+) 140 6,500 1,880 4,000 0.47 0.85
West classrms (9+) 140 6,700 1,880 4,000 0.47 0.85
North lecture class 260 5,500 2,190 4,000 0.55 0.77
East lecture class 260 7,900 2,190 4,000 0.55 0.77
Interior offices 5 500 85 300 0.28 1.04
North art classrm 32* 1,700 680 1,300 0.52 0.80
Uncorrected OA flow -- -- -- Step 5 Vou 6,500
Uncorrected OA frac Step 6 Xs 0.32
Sys vent eff -- -- -- Ev 0.77
Outdoor air intake -- -- -- Step 7 Vot 8,400
* Average (81% of 40 peak)
Step 7: Find outdoor air intake flow:Vot = Vou/Ev
= 6,500/0.77 = 8,400
design
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VRP calculation details
Resources
� ASHRAE Journal
� Oct 2004 Single-zone and dedicated-OA systems
� Nov 2004 Ventilation for changeover-bypassVAV systems
� Jan 2005 Single-path, multiple-zone systems
� May 2005 Dual-path, multiple-zone systems
� Go to <ashrae.org>, Addenda to Std 62-2001, Addendum 62n, for one spreadsheet
� See Std 62.1-2007 User’s Manual for another
design
© 2008 Trane
Multiple-Zone Systems
� OK, for design.
� But … What about operation?
� Can we use dynamic reset controls?
� Sure …
Multiple-Zone Ventilation© 2007 American Standard Inc. All rights reserved
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© 2008 Trane
operation for varying conditions
6.2.7 Dynamic Reset
Optional controls may reset zone or system settings based on changing conditions, including:
� Variations in occupancy (TOD, OCC, COU) or ventilation airflow (CO2)
� May reset zone OA flow in any system
� Variations in efficiency
� May reset system OA intake in VAV systems
� Reset VAV box minimums when economizing
� May reset minimums in some VAV-reheat systems
Std 62.1 allows zone-level dynamic reset based on “demand” (Demand Controlled Ventilation: DCV)
part load
© 2008 Trane
multiple-zone system
Dynamic Reset Approaches
� No dynamic reset
� Easy to do, but doesn’t save any energy!
� System-level (DCV)
� Approach not developed … needs research
� Ventilation reset control (VRC) only
� Responds to changes in system vent efficiency
� Ventilation reset (VRC) combined with zone-level DCV
� Responds to changes in both zone population and system ventilation efficiency
part load
��������
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MZS dynamic reset approaches
Ventilation Reset Control
� Provides system-level reset
� Accounts for changes in ventilation system efficiency (Ev) due to zone/system airflow changes
� Solves MZS equations in real time to find current Vot set point required (assuming design population in zones)
part load
© 2008 Trane
dynamic reset
Ventilation Reset Control
� Current zone airflows
Vbz = entry (found using Pz-des)Voz = Vbz/Ez (calculated w/Ez)Vdz = sensed (discharge airflow sensor)
� Current ventilation fraction for each zoneZdz = Voz/Vdz (calculated)
� Current intake airflow Vot set point (solving MZS equations)
Vou = entry (found using Pz-des and Ps)
Ev = 1 + Vou/Vps – Zd (calculated)Vot = Vou/Ev (calculated)*
*Vot =< Vot-des
part load
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VAV ventilation reset control (no DCV)
Single-Duct VAV System
Design
VRP requires minimum Vot at design
8, 810
For each zone use:
Pz = highest expected zone populationVdz = the peak zone discharge airflow Vdzm = minimum expected VdzVbz = Rp*Pz + Ra*AzZdz = Voz/Vdzm = Vbz/(Ez*Vdzm)
Votreq’d
@ design
population Pz 140 140 260 260 5 40disc airflow Vdz 6,500 6,700 5,500 7,900 500 1,700
Vdzm 4,000 4,000 4,000 4,000 300 1,300vent rate Vbz 1,880 1,880 2,190 2,190 85 760vent fract Zdz 0.470 0.470 0.548 0.548 0.283 0.585
Vou = D*ΣRp*Pz + ΣRa*Az = 0.65*7,125 + 1860 = 6,500Xs = Vou/Vps = 6,500/20,160 = 0.322Ev = 1 + 0.322 – 0.585 = 0.738Vot = Vou/Ev = 6,500/0.738 = 8,808
For the system use:
Ps = highest system pop = 550D = Ps/ΣPz = 550/845 = 0.650LDF = load diversity factor = 0.7Vps = LDF*ΣVdz-des
= 0.7*28,800 = 20,160
design
© 2008 Trane
8, 810
Votreq’d
(current)
VAV ventilation reset control (no DCV)
Single-Duct VAV System
100% Load (1)
8, 810
For each zone use:
Pz = use highest zone populationVdz = use current discharge airflow Vdzm = don’t needVbz = same as design (Pz = Pz-des)Zdz = Vbz/(Ez*Vdz) = current fraction
Votreq’d
@ design
population Pz 140 140 260 260 5 40disc airflow Vdz 4,960 5,400 4,000 4,000 500 1,300vent rate Vbz 1,880 1,880 2,190 2,190 85 760vent fract Zdz 0.379 0.348 0.548 0.548 0.170 0.585
Vou = D*ΣRp*Pz + ΣRa*Az = 0.65*7,125 + 1860 = 6,500Xs = Vou/Vps = 6,500/20,160 = 0.322Ev = 1 + 0.322 – 0.585 = 0.738Vot = Vou/Ev = 6,500/0.738 = 8,808
For the system use:
Ps = use highest system popD = Ps/ΣPz = 0.650 (same as design)LDF = don’t needVps = ΣVdz = 20,160 = currentairflow
part load
Multiple-Zone Ventilation© 2007 American Standard Inc. All rights reserved
28
© 2008 Trane
8, 390
Votreq’d
(current)
VAV ventilation reset control (no DCV)
Single-Duct VAV System
100% Load (2)
VRC delivers Vot-des or less at 100% load
8, 810
Votreq’d
@ design
population Pz 140 140 260 260 5 40disc airflow Vdz 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
Vou = D*ΣRp*Pz + ΣRa*Az = 0.65*7,125 + 1860 = 6,500Xs = Vou/Vps = 6,500/20,160 = 0.322Ev = 1 + 0.322 – 0.548 = 0.775Vot = Vou/Ev = 6,500/0.775 = 8,390
part load
© 2008 Trane
VAV ventilation reset control (no DCV)
Single-Duct VAV System
100% Load (2)
8, 810
Votreq’d
@ design
population Pz 140 140 260 260 5 40disc airflow Vdz 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
Vou = D*SRp*Pz + SRa*Az = 0.65*7,125 + 1860 = 6,500Xs = Vou/Vps = 6,500/20,160 = 0.322Ev = 1 + 0.322 – 0.548 = 0.775Vot = Vou/Ev = 6,500/0.775 = 8,390
8, 390
Votreq’d
(current)
population Pz 140 140 260 260 5 40disc airflow Vdz 4,000 3,700 4,200 4,300 300 1,700vent rate Vbz 1,880 1,880 2,190 2,190 85 760vent fraction Zdz 0.470 0.508 0.521 0. 509 0.283 0.447Vou = 6,500Xs = Vou/Vps = 6,500/18,200 = 0.357Ev = 1 + 0.357 – 0.521 = 0.836Vot = Vou/Ev = 6,500/0.836 = 7,780
90% System Load
8,810 7,780
VRC reduces Vot,saves energy
part load
Multiple-Zone Ventilation© 2007 American Standard Inc. All rights reserved
29
© 2008 Trane
multiple-zone system
Dynamic Reset Approaches
� No dynamic reset
� Easy to do, but doesn’t save any energy!
� Demand controlled ventilation (DCV) only
� Approach not developed … needs more work
� Ventilation reset control (VRC) only
� Responds to changes in system vent efficiency
� Ventilation reset (VRC) combined with DCV
� Responds to changes in both zone population and system ventilation reset
part load
© 2008 Trane
VRC calculations with DCV zones
Single-Duct VAV System
� If you calculate Vot set point
� For non-CO2 zones, find Vbz = Rp*Pz + Ra*Az using estimated (TOD, OCC) or actual (COU) Pz
� For CO2 zones, find Vbz = [Rp*Pz + Ra*Az], using a CO2 Controller (relates sensed CO2 to Vbz required)
� Use current Vbz and Voz values to solve MZS equations for current Vot set point
� If you don’t calculate Vot set point
� I’m not sure what to do … this type of “trim and respond” approach with zone or system-level DCV needs study
part load
Multiple-Zone Ventilation© 2007 American Standard Inc. All rights reserved
30
© 2008 Trane
8, 810
Votreq’d
@ design
VAV vent reset control with DCV zones
Single-Duct VAV System
Design
Same Vot-des, with or w/o DCV zones
For each zone use:
Pz = highest expected zone populationVdz = the peak zone discharge airflow Vdzm = minimum expected VdzVbz = Rp*Pz + Ra*AzZdz = Voz/Vdzm = Vbz/(Ez*Vdzm)
population Pz 140 140 260 260 5 40disc airflow Vdz 6,500 6,700 5,500 7,900 500 1,700
Vdzm 4,000 4,000 4,000 4,000 300 1,300vent rate Vbz 1,880 1,880 2,190 2,190 85 760vent fract Zdz 0.470 0.470 0.548 0.548 0.283 0.585
Vou = D*ΣRp*Pz + ΣRa*Az = 0.65*7,125 + 1860 = 6,500Xs = Vou/Vps = 6,500/20,160 = 0.322Ev = 1 + 0.322 – 0.585 = 0.738Vot = Vou/Ev = 6,500/0.738 = 8,808
For the system use:
Ps = highest system population = 550D = Ps-des/ΣPz-des = 550/845 = 0.650LDF = load diversity factor = 0.7Vps = LDF*ΣVdz-des
= 0.7*28,800 = 20,160
CO2 OCC
design
© 2008 Trane
VAV vent reset control with DCV zones
Single-Duct VAV System
100% Load (1)
8, 810
For each non-dcv zone use:Pz = highest zone pop (Pz = Pz-des) Vbz = same as design
For each non-CO2 dcv zone use:Pz = estimated pop (Pz = Pz-est)Vbz = Rp*Pz-est + Ra*Az
For each CO2 dcv zone use:Pz = ??? (don’t know current pop)Vbz = Vbz-est (from CO2 Controller)
Votreq’d
@ design
population Pz 140 140 ??? 260 5 0disc airflow Vdz 4,960 5,400 4,000 4,000 500 1,300vent rate Vbz 1,880 1,880 1,300* 2,190 85 360vent fract Zdz 0.379 0.348 0.325 0.548 0.170 0.277
Vou = D*Σnon(Rp*Pz)+Σnon(Ra*Az)+Σnon-co2(Rp*Pz-est+Ra*Az)+Σco2[Vbz-est]
= 0.65*4,780 + 1,260 + 360 + [1,300] = 6,030Xs = Vou/Vps = 6,030/20,160 = 0.299Ev = 1 + 0.299 – 0.548 = 0.751Vot = Vou/Ev = 6,030/0.751 = 8,030 (but no more than 8,808)
For the system use:D = Ps-des/ΣPz-des = 0.650Vps = current airflow = ΣVdz = 20,160Vou = D*Σnon (Rp*Pz-des) + Σnon (Ra*Az)
+ Σnon-co2 (Rp*Pz-est + Ra*Az)+ Σco2 [Vbz-est]
CO2 OCC
part load
8, 810
Votreq’d
(current)
8, 030
For all zones:Vdz = current discharge airflowZdz = current OA fraction = Vbz/Ez*Vdz
Multiple-Zone Ventilation© 2007 American Standard Inc. All rights reserved
31
© 2008 Trane
VAV vent reset control with DCV zones
Single-Duct VAV System
100% Load (1)
8, 810
For each non-dcv zone use:Pz = highest zone pop (Pz = Pz-des) Vbz = same as design
For each non-CO2 dcv zone use:Pz = estimated pop (Pz = Pz-est)Vbz = Rp*Pz-est + Ra*Az
For each CO2 dcv zone use:Pz = ??? (don’t know current pop)Vbz = Vbz-est (from CO2 Controller)
Votreq’d
@ design
population Pz 140 140 ??? 260 5 0disc airflow Vdz 4,960 5,400 4,000 4,000 500 1,300vent rate Vbz 1,880 1,880 1,300* 2,190 85 360vent fract Zdz 0.379 0.348 0.325 0.548 0.170 0.277
Vou = D*Σnon(Rp*Pz)+Σnon(Ra*Az)+Σnon-co2(Rp*Pz-est+Ra*Az)+Σco2[Vbz-est]
= 0.65*4,780 + 1,260 + 360 + [1,300] = 6,030Xs = Vou/Vps = 6,030/20,160 = 0.299Ev = 1 + 0.299 – 0.548 = 0.751Vot = Vou/Ev = 6,030/0.751 = 8,030 (but no more than 8,808)
For the system use:D = Ps-des/ΣPz-des = 0.650Vps = current airflow = ΣVdz = 20,160Vou = D*Σnon (Rp*Pz-des) + Σnon (Ra*Az)
+ Σnon-co2 (Rp*Pz-est + Ra*Az)+ Σco2 [Vbz-est]
CO2 OCC
part load
8, 810
Votreq’d
(current)
8, 030
For all zones:Vdz = current discharge airflowZdz = current OA fraction = Vbz/Ez*Vdz
VRC w/DCV reduces Vot,saves energy (even at 100% load in some
cases)
© 2008 Trane
VAV vent reset control with DCV zones
Single-Duct VAV System
100% Load (1)
8, 810
Votreq’d
@ design
population Pz 140 140 ??? 260 5 0disc airflow Vdz 4,960 5,400 4,000 4,000 500 1,300vent rate Vbz 1,880 1,880 1,300* 2,190 85 360vent fract Zdz 0.379 0.348 0.325 0.548 0.170 0.277
Vou = D*Σnon(Rp*Pz)+Σnon(Ra*Az)+Σnon-co2(Rp*Pz-est+Ra*Az)+Σco2[Vbz-est]
= 0.65*4,780 + 1,260 + 360 + [1,300] = 6,030Xs = Vou/Vps = 6,030/20,160 = 0.299Ev = 1 + 0.299 – 0.548 = 0.751Vot = Vou/Ev = 6,030/0.751 = 8,030 (but no more than 8,808)
CO2 OCC
part load
8, 810
Votreq’d
(current)
8, 030
population Pz 140 140 ??? 260 5 0disc airflow Vdz 4,000 3,700 4,200 4,300 300 1,700vent rate Vbz 1,880 1,880 2,190 2,190 85 760vent fraction Zdz 0.470 0.508 0.521 0. 509 0.283 0.447 Vou = 0.65*4,780 + 1,260 + 360 + 1,300 = 6,030Xs = Vou/Vps = 6,030/18,200 = 0.331Ev = 1 + 0.331 – 0.521 = 0.810Vot = Vou/Ev = 6,030/0.810 = 7,440
90% System Load
8,810 7,780
VRC w/DCV reduces Votsaves more energy
7,440
Multiple-Zone Ventilation© 2007 American Standard Inc. All rights reserved
32
© 2008 Trane
VAV vent reset control (with DCV zones)
Single-Duct VAV System
� So, if you had a way to relate zone CO2
sensed to zone OA required, you could use MZS equations to find Vot-set
� One simple way uses a linear controller to relate zone CO2 to require Vbz, like we did for SZS
� Can this be implemented? Yes.
� Does it work? Probably, but how well? This needs ASHRAE research.
© 2008 Trane
one way to implement DCV-zone …
CO2 DCV for VAV
� Find breathing zone outdoor airflow range
Vbz = (Rp × Pz + Ra × Az)Vbz-des = (7.5 × 260 + 0.06 × 4000) = 2190 cfmVbz-min = (7.5 × 0 + 0.06 × 4000) = 240 cfm
� Find target indoor ∆∆∆∆CO2 range
Crz = Cd + N/(Vbz/Pz)Crz-max = (after some math) = 1500 ppmCrz-min = (after some math) = 500 ppm
� Set CO2 signal range to match Cr range
� Adjust The Controller to require Vbz-design at max CO2
signal, Vbz-min at min CO2 signal
part load
Multiple-Zone Ventilation© 2007 American Standard Inc. All rights reserved
33
© 2008 Trane
one way to implement DCV-zone …
CO2 DCV for VAV
CO2 (Crz), ppm)
Vbz(cfm)
240
2190
500 1500
The Controller
part load
© 2008 Trane
DCV for multiple-zone systems
62.1 User’s Manual
� In operation we could:
� Sense CO2 in the zone (Crz)
� Adjust OA required (Vbz) per The Controller
� Solve use current Vbz values to solve the MZS equations and find the current set point for OA intake, provided Vot-set <= Vot-des
� Actual OA delivered to the CO2-zone would always equal or exceed the minimum Vbz required by Std 62.1
� But this control approach must be refined and the results analyzed before we go too far with it
part load
Multiple-Zone Ventilation© 2007 American Standard Inc. All rights reserved
34
© 2008 Trane
Implementation
� For VRC alone or combined with zone-level DCV, design usually includes:
� Communicating DDC VAV boxes
� A communicating BAS with equation-solving capability
� Intake airflow sensing and control at the AHU
part load
© 2008 Trane
OA
RA
SA
central station air handlerwith controls
communicatingBAS
• Reset outdoor airflow(TRAQ™ damper)
For VRC: Need DDC/VAV, a BAS, OA flow sensor
DDC/VAV terminals
• Req’d ventilation (Vbz, Voz)• Actual discharge flow (Vdz)• Current ventilation fraction(Zdz = Voz/Vdz)
• Totals (Vou, Vps)• “Used” OA fraction (Xs)• Sys vent efficiency (Ev)• New OA setpoint (Vot)
VAV ventilation optimization
Single-Duct VAV System
OCCCO2 TOD
part load
Multiple-Zone Ventilation© 2007 American Standard Inc. All rights reserved
35
© 2008 Trane
Some Things To Consider
� Can the BAS solve the MZS equations dynamically? If so:
� Do you want system-level VRC only, or using both VRC and zone-level DCV?
� If VRC and DCV, do you want use CO2, TOD, OCC, COU or some combination?
� Without solving MZS equations, is there a reasonable “trim/respond” approach based on DCV zones? (Don’t know, now)
part load
© 2008 Trane
incidentally, if you reduce intake airflow…
Building Pressure Control
At minimumintake, exhaust must be less than intake airflow
(Positive building pressure reduces infiltration)
++++
exhaustintake
Multiple-Zone Ventilation© 2007 American Standard Inc. All rights reserved
36
© 2008 Trane
incidentally, if you reduce intake airflow…
Building Pressure Control
If DCV reduces intake, exhaust airflow may not exceed intake
(Negative building pressure causes infiltration)
––––
exhaustintake
© 2008 Trane
ASHRAE Standard 62.1
Quick Summary
� Compared to 1989, 1999, 2001, the 2007 version of the Ventilation Rate Procedure:
� At design
� Lowers many breathing zone OA flows
� Ventilates for two zone sources (people and building), which make zone-level DCV more difficult
� Requires OA intake dependent upon system type
� For operation, makes DCV more difficult, but it allows OA intake reset based on:
� Zone-level demand (DCV)
� System-level ventilation efficiency (VRC)
Multiple-Zone Ventilation© 2007 American Standard Inc. All rights reserved
37
© 2006 American Standard Inc.
Questions?
Dennis Stanke
complying with Std 62.1-2007:
Ventilation Requirements & Dynamic Reset
complying with Std 62.1-2007:
Ventilation Requirements & Dynamic Reset