1. MECH 8250 Ventilation
Winter 2014
Lecture: February 2nd
08/09/2014

2. Topics Covered by this Course
Building Ventilation Systems
BCBC 2012
ASHRAE 62.1
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3. Natural Ventilation
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4. Mechanical Ventilation
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5. Mechanical Ventilation
Dedicated Outdoor Air Systems (DOAS)
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6. Ventilation Standards
BCBC 2012
: Ventilation of Vestibules
: For Storage Garage
9.32: Ventilation for Single Dwelling Unit
ASHRAE Standard 62
62.1: Non-Residential
62.2: Residential (BCBC 2012 takes over)
LEED (Leadership in Environment & Energy Design)
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7. VENTILATION – BCBC 2012
BCBC : Natural Ventilation: Unobstructed area of 0.1m2 for each door that opens into the vestibule BUT not less than 0.4m2 Mechanical Ventilation: 14m3/hr.m2 (0.82 cfm/ft2) for vestibule area
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8. BCBC 3.3.5.7 – Ventilation of Vestibules
Natural Ventilation: Unobstructed area of 0.1m2 for each door that opens into the vestibule BUT not less than 0.4m2 Mechanical Ventilation: Supply 14m3/hr.m2 (0.82 cfm/ft2) for vestibule area
Natural Ventilation: 0.2m2 – which is less than 0.4m2. therefore 0.4m2 of free 50% free area dampers, we have 0.8 m2 ( ~86 ft2)
Mechanical Ventilation: Supply 14m3/hr.m2 (0.82 cfm/ft2) for vestibule area
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9. BCBC 6.2.2.3 – For Storage Garage
Mechanical Ventilation:
Continuous supply of ventilation 14m3/hr.m2 (0.76 cfm/ft2) of the floor area.
When CO and NO2 is detected at higher levels, this ventilation air is increased. 6ACH.
Garage: m2 10,610ft2
cfm/ft2 3,900 l/s 8,000 cfm
6ACH (3m – 9ft high) 9,500 cfm
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10. VENTILATION – BCBC 2012
BCBC : Ventilation during Non-Heating Season : Natural Ventilation Table Open areas for various rooms : Mechanical Ventilation 0.5 ACH for air-conditioning spaces 1.0 ACH for NON air-conditioning spaces
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11. VENTILATION – BCBC 2012
BCBC : Ventilation during Heating Season : Principal Ventilation Exhaust Fan OR Dedicated Central Ventilation System
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12. VENTILATION – BCBC 2012 Changes implemented on December 19 2014:
The End of Exhaust-Only Ventilation Systems. Exhaust-only ventilation systems are being replaced by a system that includes both exhaust and supply.
Principal Ventilation System Requirements : Continuous Operation (24 hours a day)
The same Principal Exhaust Fan can be used for Washroom or Kitchen, but when the room is being used, the exhaust will increase to satisfy the exhaust requirements
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13. VENTILATION – BCBC 2012
Ventilation during Heating Season : Dedicated Central ventilation System with minimum Ventilation rate
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14. Principal Ventilation System Exhaust Fan
A SFD unit shall include: A principal ventilation system including supply (1) and continuous exhaust (2). The bathroom fan (2) provides continuous exhaust as the principal ventilation exhaust fan and intermittent, on command exhaust at a higher air flow rate as a bathroom fan. The kitchen exhaust is provided by a dedicated kitchen exhaust fan (3). The heated crawl space is provided with a dedicated fan (4) and at least one passive grille to the rest of the house (5).
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15. Ducted forced-air furnace
The furnace ducting provides supply air to required areas of the dwelling unit and the bathroom fan is designated as the principal ventilation exhaust fan, operating continuously as the principal ventilation exhaust fan (see ) and intermittently as a bathroom fan (see ).
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16. Use of HRV in Ducted Furnace
(3) Using a ducted forced-air furnace in the principal ventilation system. The HRV may act as the principal ventilation exhaust fan and may exhaust from more than one location in the dwelling unit. In this case, the bathroom and kitchen fans are not part of the principal ventilation system.
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17. Topics Covered by this Course
General requirements
LEED Points
Ventilation requirements
Construction and O/M requirements
Energy Efficiency Options
Possible Coming Changes
Questions
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18. ASHRAE – LEED Points EQ Prerequisite 1: Minimum IAQ
EQ Prerequisite 2: Environmental Tobacco Smoke (ETS) Control
EQ Credit 1: Outdoor Air Delivery Monitoring for CO2
EQ Credit 2: Increased Ventilation – at least 30% more than ASHRAE
EQ Credit 3.1: Construction IAQ Management during Construction
EQ Credit: Construction IAQ Plan before occupancy
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19. 1. Purpose
1.1 The purpose of this standard 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. 1.2 This standard is intended for regulatory application to new buildings, additions to existing buildings, and those changes to existing buildings that are identified in the body of the standard. 1.3 This standard is intended to be used to guide the improvement of indoor air quality in existing buildings.
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20. 2. Scope
2.1 All spaces intended for human occupancy excluding low-rise residential (62.2) 2.2 Defines requirements for ventilation, air-cleaning design, commissioning, installation and O&M 2.3 Additional requirements and other standards may apply (labs, healthcare, industrial, etc.) 2.4 May be applied to both new and existing buildings, not intended to be used retroactively 2.5 Does not prescribe specific ventilation rates for smoking spaces 2.6 Ventilation requirements based on chemical, physical, & biological contaminants 2.7 Consideration or control of thermal comfort is not included 2.8 In addition to ventilation, the standard contains requirements related to certain sources
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21. 2. Scope
2.9 Acceptable IAQ may not be achieved in all buildings meeting these requirements because of:
Diversity of sources and contaminants
Air temperature, humidity, noise, lighting, and psychological/social factors
Varied susceptibility in the occupants
Introduction of outdoor contaminants
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22. 2. DEFINITIONS
Acceptable indoor air quality: Air in which there are no known contaminants at harmful concentrations as determined by cognizant authorities and with which a substantial majority (80% or more) of the people exposed do not express dissatisfaction. Occupiable space: an enclosed space intended for human activities, excluding those spaces intended primarily for other purposes, such as storage rooms and equipment rooms, that are only occupied occasionally and for short periods of time.
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23. Ventilation System
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24. 6. PROCEDURES 6.1 General. 6.1.1 Ventilation Rate Procedure.
Ventilation Rate Procedure or IAQ Procedure for outdoor airflow values for mechanical ventilation systems
6.1.1 Ventilation Rate Procedure.
Prescribes rates & procedures based on typical space contaminant sources & source strengths
6.1.2 IAQ Procedure.
Requires calculation of rates based on analysis of contaminant sources, concentration targets and perceived air quality targets.
This slide shows that there are two different procedures that can be used to design ventilation system for a building in the case of mechanical ventilation systems.
a) Ventilation Rate Procedure and
b) IAQ procedure.
VRP is a prescriptive procedure that specifies minimum outdoor airflow rates which are based on contaminant sources and strengths that are typical for the listed space. The rates are meant to dilute and exhaust odorous bioeffluents from occupants and odorous and sensory irritant contaminants from other sources typical of that space type. Details of the ventilation calculations are covered in another presentation.
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25. 6. PROCEDURES Ventilation Rate Procedure Indoor Air Quality 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
This slide shows that there are two different procedures that can be used to design ventilation system for a building in the case of mechanical ventilation systems.
a) Ventilation Rate Procedure and
b) IAQ procedure.
VRP is a prescriptive procedure that specifies minimum outdoor airflow rates which are based on contaminant sources and strengths that are typical for the listed space. The rates are meant to dilute and exhaust odorous bioeffluents from occupants and odorous and sensory irritant contaminants from other sources typical of that space type. Details of the ventilation calculations are covered in another presentation.
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26. VENTILATION RATE PROCEDURE
This slide shows that there are two different procedures that can be used to design ventilation system for a building in the case of mechanical ventilation systems.
a) Ventilation Rate Procedure and
b) IAQ procedure.
VRP is a prescriptive procedure that specifies minimum outdoor airflow rates which are based on contaminant sources and strengths that are typical for the listed space. The rates are meant to dilute and exhaust odorous bioeffluents from occupants and odorous and sensory irritant contaminants from other sources typical of that space type. Details of the ventilation calculations are covered in another presentation.
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27. VENTILATION RATE PROCEDURE
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28. Ventilation Air (OA) Calculation
Step 1
Vbz = RpPz + RaAz
Vbz = Breathing Zone OA
Rp= Outdoor Air Rate per person
Pz = Zone Population
Ra = Outdoor Air Rate per unit area
Az = Zone Floor Area (Net occupiable)
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29. Ventilation Air (OA) Calculation
Step 2
Voz =Vbz/Ez
Voz = Ventilation Outdoor Airflow in the zone
Vbz = Breathing Zone Outdoor Airflow
Ez = Effectiveness of the air distribution
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31. COOLING
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32. Induced Ventilation
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33. HEATING
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34. Ventilation Air (OA) Calculation
Step 2
Voz =Vbz/Ez
Voz = Ventilation Outdoor Airflow in the zone
Vbz = Breathing Zone Outdoor Airflow
Ez = Effectiveness of the air distribution
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35. Multiple Spaces Vot = Vou/Ev Vot - Design OA intake flow
Vou - Uncorrected OA intake
Ev - ventilation efficiency from Table 6-3 or Appendix A
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36. General Requirements 4. OUTDOOR AIR QUALITY 5. SYSTEMS AND EQUIPMENT
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37. 4. Outdoor Air Quality 4.1 Regional Air Quality 4.2 Local Air Quality
Must determine NAAQS attainment status
Air cleaning is required in some cases in non-attainment areas
4.2 Local Air Quality
Conduct observational site survey to identify local sources of air contaminants
4.3 Documentation
Regional air quality compliance status
Local survey information
Conclusions regarding acceptability of outdoor air quality
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38. 5. SYSTEMS AND EQUIPMENT 5.1 Natural Ventilation
Location and size of openings
Naturally ventilated spaces shall be permanently open to and within 8 m (25 ft) of operable wall or roof openings to the outdoors, the openable area of which is a minimum of 4% of the net occupiable floor area.
Louvers based on the free unobstructed area.
Where interior spaces without direct openings to the outdoors are ventilated through adjoining rooms, the opening between rooms shall be permanently unobstructed and have a free area of not less than 8% of the area of the interior room nor less than 25 ft2 (2.3 m2).
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39. VENTILATION – ASHRAE 62.1 5.1 Natural Ventilation
Determine the maximum W to qualify for natural ventilation.
Minimum size of each operable window.
What needs to be changed for the 10’x10’ room to allow natural ventilation?
What if the operable windows are changed with a louver with 0.5 free area.
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40. VENTILATION – ASHRAE 62.1 5.1 Natural Ventilation
Determine the maximum W to qualify for natural ventilation. Within 25’ of the opening. Therefore the W will be 10’ + 25’ = 35’
Minimum size of each operable window. Opening Size: 4% minimum of the floor area Floor area: 35’ x 40’ = 1,400 ft2 Opening Area = 56ft2 Window area: 18.7ft2 (three)
What needs to be changed for the 10’x10’ room to allow natural ventilation? The door (>8.5ft high and 3ft wide) must be removed to make the opening permanently unobstructed so that the interior office can have natural ventilation. Greater of the two: 8% of floor area = 112 ft2 OR 25ft2
What if the operable windows are changed with a louver with 0.5 free area. 56ft2 x 0.5 = 112ft2
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41. 5. SYSTEMS AND EQUIPMENT 5.2 Ventilation Air Distribution
Must provide means to adjust the system (Balancing Dampers)
Minimum ventilation air must be provided to each terminal unit in ceiling/floor plenum systems
Documentation (Air Balancing Reports)
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42. 5. SYSTEMS AND EQUIPMENT 5.3 Exhaust Duct Location
Operate exhaust ducts with harmful contaminants at negative pressure
(Install Exhaust Fans at the end of the exhaust duct system)
5.4 Ventilation System Controls
Control to assure proper ventilation under any operating condition
5.5 Airstream Surfaces
Use materials that have documented resistance to microbial growth and erosion
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43. 5. SYSTEMS AND EQUIPMENT 5.6 Outdoor Air Intakes
Location: Separate OA intake from outdoor contaminant sources
Must comply with default minimum separation distances in Table 5-1. Examples:
Loading dock 25 ft
Dumpster 15 ft
Surface below intake 1 ft
Cooling tower exhaust 25 ft
Rain Entrainment: Must limit moisture penetration (using hood, proper velocity, etc.) or manage water that penetrates
Rain Intrusion: Prevent moisture intrusion into equipment mounted outdoors
mounted outdoors
Snow Entrainment: Designed to manage melted snow drawn in the system.
Bird Screens: Must use bird screens and prevent bird nesting
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44. 5. SYSTEMS AND EQUIPMENT 5.7 Local Capture of Contaminants
Discharge air from non-combustion equipment that captures contaminants shall be exhausted to the outdoors
5.8 Combustion Air
Follow manufacturer’s instructions to provide sufficient combustion air and exhaust air for indoor fuel-fired appliances
Products of combustion from vented appliances shall be vented directly outdoors
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45. 5. SYSTEMS AND EQUIPMENT 5.9 Particulate Matter Removal
MERV 6 (or gUse a filter rated at MERV 6 (orgreater) upstream of cooling coils and other wet-surface devices in supply stream
5.10 Dehumidification Systems
Must be able to limit indoor RH to 65%or less at design dew point condition
Exception to RH limit - where occupancy requirements or processes dictate higher RH conditions
Intake airflow must be greater than relief/exhaust during cooling (to minimize moist air infiltration)
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46. 5. SYSTEMS AND EQUIPMENT
At 75F, 65% RH, safety Margin is 13F before condensation occures.
62F DP
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47. 5. SYSTEMS AND EQUIPMENT 5.11 Drain Pans
Assure drainage without flooding or carryover
Slope: 0.125” (1/8”) per foot toward outlet
Drain: located at lowest point, with sufficient diameter prevent overflow
Drain seal: Shall include P-trap or other seal for negatively pressurized drain pans to prevent ingestion of air while allowing complete drainage (fan on or off)
Pan size: length at least 1/2 coil height or as necessary to limit carryover
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48. 5. SYSTEMS AND EQUIPMENT 5.12 Finned Tube Coils and Heat Exchangers
Use drain pan
Select to limit coil pressure drop to fpm face velocity
If higher pressure drop, provide access on both sides for maintenance
5.13 Humidifiers and Water Spray Systems
Use potable water (or better)
No downstream devices within absorption distance
5.14 Access for Inspection, Cleaning and Maintenance.
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49. 5. SYSTEMS AND EQUIPMENT 5.15 Building Envelope and Interior Surfaces
Weather barrier to prevent water penetration into envelope
Vapor retarder or other means to prevent condensation on cold surfaces within envelope
Seal all seams, joints, penetrations to limit infiltration
Insulate pipes, ducts expected to have surface temperature below surrounding dew point
5.16 Buildings with Attached Parking Garages. Limit infiltration of vehicular exhaust
Maintain garage pressure at or below adjacent occupied space
Or, use a vestibule
Or, otherwise design to minimize air migration from garage to occupied space
Although these envelope details are usually not under the HVAC designers purview, they are important considerations to reduce the potential for microbial growth, especially within the wall structure….
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50. 5. SYSTEMS AND EQUIPMENT 5.17 Air Classification and Recirculation
Limit recirculation or transfer of “dirty” air to “cleaner” spaces
Classification
Designate air leaving each space using Table 6.1
Class 1: Low contaminant concentration (office)
Class 2: Moderate concentration (dining room)
Class 3: Significant concentration (sick room)
Class 4: Highly objectionable or potentially harmful concentration
Note that these classes of air relate to commercial applications for the Standard and that other industry Standards (ACGIH, etc.) have developed classes of air for non-commercial applications…
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51. 5. SYSTEMS AND EQUIPMENT 5.17.2 Re-Designation:
Air Cleaning. May reclassify air cleaned by passing it through an appropriate air-cleaning system
Energy Recovery. Energy recovery ok:
class 2 (exhaust) airstreams must have no more than 10% leakage into a class 1 airstream.
class 3 (exhaust) airstreams must have no more than 5% leakage into a class 1 airstream.
Transfer. Mixed classes are re-designated.
Recirculation Limitations:
Manage recirculation as follows
Class 1 to anywhere
Class 2 to self, similar Class 2 or Class 3 or Class 4
Class 3 to self
Class 4 to outdoors
Reclassification of air by air cleaning requires approval of authority having jurisdiction. Class 3 air may be re-designated to Class1 in the process of energy recovery if diluted with OA so no more than 5% is Class 3
Transfer Example: Air mixed from Class 2 space and Class 1 space air streams must be designated Class 2
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52. 5. SYSTEMS AND EQUIPMENT
5.18 Requirements when building has both ETS and ETS-Free areas.
Does not purport to achieve acceptable IAQ in ETS areas.
Spaces must be classified as ETS or ETS-Free
Air must be kept separate by means of walls, automatic door closers and pressurization
Recirculation or transfer from ETS to ETS-Free is prohibited
ETS areas must be exhausted to the outdoors
Pressurization. Relative pressure in ETS and ETS-Free areas may be demonstrated by various methods (Example - Engineering analysis, measurement, airflow measurement). Separation techniques between dwelling units and adjacent properties are thoroughly described in the Exceptions to Separation include other engineered solutions to maintain airflow to protect against movement of ETS laden air into ETS-Free areas - examples are described in
The scope of the standard excludes setting specific ventilation rates for smoking areas. The current requirement is that smoking areas shall have more ventilation and/or air cleaning than comparable no smoking areas (6.2.9). This section addresses separation of ETS and ETS-free areas, not outdoor airflow rates or air cleaning requirements.
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53. 6. PROCEDURES 6.1 General. 6.1.1 Ventilation Rate Procedure.
Ventilation Rate Procedure or IAQ Procedure for outdoor airflow values for mechanical ventilation systems
6.1.1 Ventilation Rate Procedure.
Prescribes rates & procedures based on typical space contaminant sources & source strengths
6.1.2 IAQ Procedure.
Requires calculation of rates based on analysis of contaminant sources, concentration targets and perceived air quality targets.
This slide shows that there are two different procedures that can be used to design ventilation system for a building in the case of mechanical ventilation systems.
a) Ventilation Rate Procedure and
b) IAQ procedure.
VRP is a prescriptive procedure that specifies minimum outdoor airflow rates which are based on contaminant sources and strengths that are typical for the listed space. The rates are meant to dilute and exhaust odorous bioeffluents from occupants and odorous and sensory irritant contaminants from other sources typical of that space type. Details of the ventilation calculations are covered in another presentation.
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54. 7. CONSTRUCITON & SYSTEM START-UP
7.1 Construction Phase
Don’t operate air handlers without filters
Protect building materials
Protect occupied areas
Limit migration of construction contamination into occupied space
Air Duct Construction shall be in accordance with the SMACNA duct construction standards and NFPA standards governing installation of HVAC systems
7.2 System Start-up
Balance airflow values, test drain pans, clean up before starting, test damper controls
Documentation including balance report, construction drawings and design criteria with assumptions shall be provided to Owner
The Owner may be the operator or designee of the Owner….
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55. 8. OPERATION & MAINTENANCE
8.2 Operations and Maintenance Manual.
Develop and maintain a building operations and maintenance manual which shall include a maintenance schedule with frequencies of tasks.
8.3 Ventilation System Operation.
Operate in accordance with Building Operations Manual
8.4 Ventilation System Maintenance.
Maintain in accordance with Building Operations Manual.
Proper maintenance of system is very important. Maintain design air flow at all times.
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56. 8. OPERATION & MAINTENANCE
Coil drains
Drain pans shall be inspected at least once a year and cleaned if required
Outside Air Flow Verification
For units >2,000 cfm the outside air flow shall be tested a minimum of every 5 years and adjustments shall be made to have the design flow provided to system
Re-commission system every 5 years or sooner if possible.
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57. ASHRAE 62.1 - History 62-2001 Prescriptive Commissioning O&M
Combustion air
Filtration
IAQ-Health disclaimers
Smoking disclaimers
Clarified CO2as ventilation metric
Alternative Air Quality Proc.
Updated
1970
1980
1990
2000
2010
Removed Thermal Comfort
Ventilation Rate Proc.
IAQ Proc.
Commercial and High Rise Res.
Enforceable code language
ETS vent. rates not covered
Vent. Rate. Proc. Modified
Occupant and area vent. rates
first issued
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