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Transcript of Ashrae Std 62 11
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Ventilation for AcceptableIndoor Air Quality
62.1-2010
Dave Kahn, P.E.Dave Kahn, P.E.
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What Is ASHRAE Standard
62.1?
The Industries Ventilation StandardConsensus StandardStandard of Care
Used in NFPA 5000 BuildingConstruction and Safety Code
LEED Requirement
2009 IMC Ventilation systemefficiency may be calculated byAppendix A (62.1-2004)
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History of the Standard
1905 Flugge 30 cfm
1936 Yaglou 10 cfm 1973 First Issued office 15 cfm/p 1981 Lower Rates office 5 cfm/p 1989 Higher Rates office 20 cfm/p
1999 Little Change
office
20 cfm/p
2001 More Mandatory Language office 20 cfm/p
2004 Key Changes
office 17 cfm/p
2007 Appendix H office 17 cfm/p 2010 Dropped Smoking office17 cfm/p
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Acceptable Indoor Air Quality
What Is It? Standard 62: Air in whichthere is no known
contaminants at harmful
concentrations as determinedby cognizant authorities and
with which a substantial
majority (80% or more) of thepeople exposed do not
express dissatisfaction.
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How Much Ventilation?
Unknown Chamber studies
Limited to body odor (olf)
Medical evidence
No evidence based
studies
Rule of thumb evidence
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Chamber Body Odor StudiesImpact of ventilation rate on visitors
From ASHRAEpresentation by
Steve Taylor
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Body Oder StudiesCain & Leaderer
From ASHRAEpresentation by
Steve Taylor
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Cain & Leaderer
1983 For nonsmoking occupancy, 47 combinationsof temperature, humidity, ventilation rate and
occupancy density were examined. Odor
level depended entirely on ventilation rate perperson irrespective of the number of personsin the chamber.
For both smoking and nonsmokingconditions, a combination of hightemperature (78F) and humidity (r.h. > 70
%) exacerbated the odor problem
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Recent Studies
Hillsborogh County Schools March 2011 Engineered Systems
9th
largest district in US
7.5 cfm/student 2 California Studies ongoing Anticipate ventilation rate changes
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62.1 New in 2010
PM2.5 non-attainment areas require air cleaning Smoking spaces no longer covered by thestandard Air intake separation distances revised Deletes requirements for health care spaces Revises IAQ procedure to make it more robust Most natural ventilation systems now requiremechanical systems for when natural vent cannot
be used (thermal comfort, noise, security)
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Fun Facts
Means to balance the system to achieve minimum
airflow. Design documentation to state ventilation rate andair distribution assumptions. Controls to enable the fan to operate wheneverthe spaces served are occupied. VAV systems with fixed OA dampers must complyat minimum supply airflow.
MERV 6 filters upstream of all coils or other
devices with wetted surfaces.
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Two paths to compliance
Ventilation Rate Procedure
Most commonly used method
Lookup table (simple) or Appendix A (complex)
Need zone air distribution effectiveness
LEED requires this method
Indoor Air Quality Procedure
Design to maintain specific contaminant levels
Mass Balance Analysis
Methods used in similar buildings
Validation by contaminant monitoring
Single duct
systems such
as VAV
reheat
Multiple paths: Fan
powered VAV and
Dual duct
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Ventilation Rate Procedure
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Ventilation Rate Procedure
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Ventilation Rate Procedure
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Classroom ExampleSingle zone 2010
High School classroom 35x35 30 people Vbz = Rp
Pz
+ Ra
Az Vbz
= Breathing Zone OA
10 cfm /person 10 * 30 = 300 cfm
0.12 cfm/ft2 0.12 * 35 * 35 = 147 cfm
300 + 147 = 447 cfm
Zone outdoor airflow Voz =Vbz /Ez 447 /1 = 447 cfm or14.9 cfm/person
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Short-Term Conditions
Peak occupancy of short duration Ventilation interrupted for a short period oftime T = 3V/ Vbz V = Volume of ventilation zone
+ Zone outdoor air flow
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Example Private Office
230 Sq Ft, 9 ft ceiling Work station and 2guest chairs
T= 3V/ Vbz = 9*230*9/(3*5 +230 *0.06) = 3.6hrs
Assume guests present 1/3 of time
Design occupancy = 1 + (2 * 1/3) = 1.7
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Multiple-Zone Recirculating
Systems
For each zone: Vbz = Rp
Pz
+ Ra
Az Just like previous example
Voz =Vbz /Ez Just like previous example
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Multiple-Zone Recirculating
Systems
Primary outdoor air fraction Zp Zpz = Voz
/Vpz (For each zone)
Voz -
zone outdoor airflow
Vpz - minimum zone primary airflow(supply air)
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Uncorrected Outdoor
Air Intake
Vou
= Dall zones
Rp
Pz
+ all zones
Ra
Az Vou
-
uncorrected outdoor air intake
D - occupant diversity = Ps / all zones Pz
Ps
-total population of area served
by the system
Pz
- largest number of peoplein the zone
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System Ventilation Efficiency
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Outdoor Air Intake
Vot = Vou /Ev Vot - design outdoor air intake flow
Vou
-
uncorrected outdoor air intake
Ev - ventilation efficiency from Table 6-3or Appendix A
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62MZCalc
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62MZCALC
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62MZCALC
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DYNAMIC RESET
VRP procedure gives the peak rate based on
worst case assumptions (design)
Reset based on Occupancy: time of day Occupancy sensors
Carbon dioxide
Air distribution efficiency
Multiple space equation solved
dynamically Economizer reset of VAV minimums
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Dynamic Reset
Air Distribution Efficiency If min OA determined in heating mode, OA can bereduced during cooling due to a higher Ez
Solve equations in appendix A dynamically based onzone and system flows to reset zone minimums andoutdoor airflow.
OA economizer reset of VAV Box minimum
Dont drop below the area outdoor air rate Ra . Economically limited to high-density occupancies.
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Demand Controlled Ventilation
CO2 .Time averaging to reduce zone population is notallowed
Constant Volume with no air flow measurementAt CO2
max, damper positioned to admit Vot design
occupancy
At ambient CO2
levels set minimum to admit required
air quantity with no occupants Vat
Linear reset between CO2
max and CO2
ambient
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Demand Controlled Ventilation
CO2 sensor location: In the breathing zone
Typically adjacent to the temp sensor
44 AFF
Return air sensing doesnt work
Sensor type Infrared Accuracy +- 75 PPM
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Constant Volume W/O air flow
measurement
Calculate Vot at design occupancy rate Calculate Vot with no occupants call it Vat
Reset min OA damper position from Vat to
Vot as CO2 varies from 400 (ambient) to 800(calculated or arbitrary setpoint)
Damper positions set in conjunction withbalancer
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Constant volume with air
flow measurement Solve equations A-H dynamically to reset therequired min OA qty
Cant reduce the number of occupants using
time averaging Can reset zone effectiveness based onsupply air temperature
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Multiple Zone Systems
ASHRAE Research 1547TRP is working on it
Old
method in 2004 handbook
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Learning More
Read the standard
2010 Handbook is available ASHRAE ALI courses
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Questions