Residential HVAC Filtration
What Does it Do?
T.J. Ptak and Chrystal Gillilan
Presented at
National Air Filtration Associat...
Scope
Introduction
Indoor air quality
Airborne contaminants
Filter performance test method
Residential HVAC system
I...
Indoor Air Quality
Air pollution
Unwanted substances
Particulate matter including bioaerosols
Gaseous pollutants, rado...
Indoor Air Quality – Commercial Buildings
Sick Building Syndrome (SBS)
30% office buildings suffer from SBS (64 million
...
Indoor Air Quality – Residential Buildings
Over 50% of homes have at least 6 detectable
allergens present
Allergic disea...
Indoor Air Quality – Health Impact
Short term and chronic exposure to particulate
matter (PM) is associated with:
Relati...
Indoor Air Quality – Impact of Filtration
Filtration impact on microvascular function (MVF):
21 couples, nonsmokers
Dur...
Personal and Ambient
Personal and outdoor PM2.5
Good correlation (impact of ETS)
Personal and outdoor PM10
CPersonal =...
Indoor Air
 Particle size - 0.005 to 500 micrometers
 Sources:
 Outdoor
Infiltration
 Tobacco smoke, stoves, fireplac...
Particle Size
Tobacco smoke 0.01 – 1 µm
Household dust 0.05 – 100
– Pet dander 0.5 – 100
– Dust mite debris 0.5 – 50
– Ski...
Household Aerosols
                           
PARTICLE SIZE, MICROMETERS
       
0.01 0.1 1 10 100
                   
  ...
Lung Deposition
 Particle deposition in lungs
Source; J. Heyder, GSF
Lung Deposition
 Particle deposition in respiratory tract:
 Upper, upper bronchial, lower bronchial, alveolar
Source; J....
Scope
Introduction
Indoor air quality
Airborne contaminants
Filter performance test method
Residential HVAC system
I...
ASHRAE 52.2 Test Method
Filtration efficiency for particle sizes 0.3 to 10
µm
Challenge aerosol KCl
Test dust ASHRAE
I...
ASHRAE 52.2 Test Method
Air flow rate (face velocity) for testing
 118 – 246 – 295 – 374 - 492 – 630 – 748 fpm
 Concept...
MERV
GROUP
NUMBER
MERV
RATING
E1
Average Particle
Size Efficiency (PSE)
0.3 - 1.0 Microns
E2
Average Particle
Size Efficie...
Residential HVAC
Building as protection against outdoor contaminants
Residential HVAC systems
Indoor sources of particu...
Residential HVAC
Major components
Return and supply ducts
Blowers
Permanent Split Capacitor (PSC)
 Brushless Permanen...
Typical Residential HVAC
ΔPS (+) ΔPR (-)
SUPPLY RETURN
HEATING
F
Flow Rate
Fan curve for PSC blower
 Typical, small residential PSC blowers HP⅓
Types of Residential Filters
Pleated and flat panel – 1 and 4” deep
Residential HVAC
Residential furnace filters – typical issues
Filter bypass
Lack of seal, gaskets
Filter size does not...
Undersized Filters
Practical industry standards
One ton of cooling 12,000 Btu
Cooling airflow 400 cfm/ton
Heating airf...
Filter Area Utilization
Change in cross section area of a return duct
Smaller inlet to the blower
Test Overview
Selection of residential furnace filters
Dimensions 20 x 25 x 5 in.
Efficiency MERV 4 – 16
Filter testin...
Laboratory Test
 Blower
 Permanent Split Capacitor (PSC)
 ¾ HP
 Test set up
 Duct dimensions 28 x 12 in.
28 x 21 in.
...
Air Velocity
 Air velocity across MERV 8 filter
 Measurements 2 in. from the test filter
 Theoretical air velocity V = ...
Performance of Selected Filters
Filters tested according to ASHRAE 52.2
Filter dimensions 20 x 25 x5 in.
Filter efficien...
Performance of Selected Filters
Filters tested according to ASHRAE 52.2
Filter dimensions 20 x 25 x5 in.
Filter efficien...
Performance of Selected Filters
Filters tested according to ASHRAE 52.2
Filter dimensions 20 x 25 x5 in.
Filter pressure...
Filter Bypass
Filter penetration, P with bypass flow, QB
Bypass flow through gaps
   
 
Efficiency decrease depends on:...
Filter Efficiency
Filter initial efficiency at the flow rate of 2000 cfm
E1 efficiency for submicron particles (0.3 – 1)...
Impact of Bypass
Filter initial efficiency at the flow rate of 2000 cfm
E1 efficiency for submicron particles (0.3 – 1)
...
Scope
Introduction
Indoor air quality
Airborne contaminants
Filter performance test method
Residential HVAC system
I...
Cleaning Effectiveness – Particle Decay
 Concentration of particles
 Submicron 0.3 – 0.5 micron
 E2 range 1 – 3 micron
...
Cleaning Effectiveness – Impact of MERV
 Particle decay for 0.3 – 0.5 micron particles
Cleaning Effectiveness – Impact of MERV
 Particle decay for 1 – 3 micron particles
Cleaning Effectiveness – Filter Size Impact
 Particle decay for 0.3 – 0.5 micron particles
Cleaning Effectiveness – Filter Size Impact
 Particle decay for 1 – 3 micron particles
Cleaning Effectiveness – Filter ΔP impact
 Particle decay for 0.3 – 0.5 micron particles
 ΔP = 0.15 and ΔP = 0.49 in. H2...
Cleaning Effectiveness – Filter ΔP impact
 Particle decay for 1 – 3 micron particles
 ΔP = 0.15 and ΔP = 0.49 in. H2O @1...
Scope
Introduction
Indoor air quality
Airborne contaminants
Filter performance test method
Residential HVAC system
I...
Life Cycle Costs
Life Cycle Costs (LCC) widely used to design energy
efficient commercial HVAC systems
LCC =Initial Inves...
Typical Residential HVAC
ΔPS (+) ΔPR (-)
SUPPLY RETURN
HEATING
F
Flow Rate
Fan curve for PSC blower
 Typical, small residential PSC blowers HP⅓
Power Consumption
Power consumption for PSC blower
 Typical, small residential PSC blowers HP⅓
Test House
 HVAC System
 Duct dimensions 24 x 10 in.
 Blower PSC – 1/3 HP
 Rated at TESP 0.50 in. H2O
 Furnace 88,000...
Test Results
Filter Filter ΔP Flow Power ΔPR ΔPS
[in. H2O] [cfm] [W] [in. H2O]
NO FILTER 1232 636 -0.23 0.11
MERV 8 0.13 1...
Impact on Heating Time
Test results
Test house 2300 Ft2
 Mode Heating
Test time 1-1.5 hr per filter
Outside temperatu...
Impact on Heating Time
Average heating time for each filter was measured
Heating time for high ΔP filter
Ratio = -------...
Impact on Heating Time
Blower electrical energy
High ΔP filter Low ΔP
filter
Power usage, [W] 552 606
Corrected for time ...
Summary
 Literature data support link between exposure to
submicron particles and health issues
 Performance of resident...
Summary
 Energy cost to operate residential HVAC system during
heating mode is higher for high resistance filters
 Resid...
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Residential HVAC Filtration - What does it do?

  1. 1. Residential HVAC Filtration What Does it Do? T.J. Ptak and Chrystal Gillilan Presented at National Air Filtration Association, TECH 2009
  2. 2. Scope Introduction Indoor air quality Airborne contaminants Filter performance test method Residential HVAC system Impact of filter efficiency on indoor air Energy cost Conclusions
  3. 3. Indoor Air Quality Air pollution Unwanted substances Particulate matter including bioaerosols Gaseous pollutants, radon, noise U.S. residents spend*  87% of time indoors  7.2% in transit and 5.6% outdoors Indoor and outdoor air pollutants Indoor concentration >outdoor concentration *R. Wilson and J. Spengler – Particles in Our Air
  4. 4. Indoor Air Quality – Commercial Buildings Sick Building Syndrome (SBS) 30% office buildings suffer from SBS (64 million workers) Indoor Air Pollution costs employees $150 billion in employee productivity 5 -7 % productivity loses Productivity loss $22.67/Ft2
  5. 5. Indoor Air Quality – Residential Buildings Over 50% of homes have at least 6 detectable allergens present Allergic diseases affect as many as 40 -50 mln Asthma (chronic disease) affects about : 20 mln adult Americans 9 mln children Allergic asthma – allergens (dust mites, mold, animal dander, pollen) make their symptoms worse Asthma costs USA $18 billion Source: American Academy of Allergy Asthma & Immunology
  6. 6. Indoor Air Quality – Health Impact Short term and chronic exposure to particulate matter (PM) is associated with: Relationship between mortality rate and PM2.5 concentration Increased morbidity and mortality Respiratory and cardiovascular disease Pulmonary inflammation, oxidative stress, endothelial dysfunction, Combustion PM associated with mortality Ultrafine particles induce reactive oxygen species, oxidative stress and inflammation Source: American Journal of Respiratory and Critical Care Medicine
  7. 7. Indoor Air Quality – Impact of Filtration Filtration impact on microvascular function (MVF): 21 couples, nonsmokers During test ( 48 hrs) participant stayed home Concentration of particles (0.1 – 0.7 µm) was monitored Baseline concentration 10,016 #/cm3 Filtered 3,206 #/cm3 MVF was measured Results: Indoor air filtration significantly improved MVP by 8.1% Source: American Journal of Respiratory and Critical Care Medicine
  8. 8. Personal and Ambient Personal and outdoor PM2.5 Good correlation (impact of ETS) Personal and outdoor PM10 CPersonal = 55 + 0.6 COutdoor [µg/m3 ] Weak correlation *R. Wilson and J. Spengler – Particles in Our Air
  9. 9. Indoor Air  Particle size - 0.005 to 500 micrometers  Sources:  Outdoor Infiltration  Tobacco smoke, stoves, fireplaces  Occupant activities  Carpets, curtains, furniture  Emission by humans  100,000 to 10,000,000 particles per minute Relationship between indoor/outdoor concentration Residence with smokers 4.4 Residence without smokers 1.1 - 1.4 Indoor sources – cooking 5 - 10
  10. 10. Particle Size Tobacco smoke 0.01 – 1 µm Household dust 0.05 – 100 – Pet dander 0.5 – 100 – Dust mite debris 0.5 – 50 – Skin flakes 0.4 – 10 – Cooking smoke/grease 0.02 – 2 Pollen 5 – 100 Bacteria 0.2 – 20 Viruses 0.005 – 0.1 Biological agents 0.5 – 5 Molecules < 0.001 Settling velocity of 10 µm particle V = 1.5 fpm
  11. 11. Household Aerosols                             PARTICLE SIZE, MICROMETERS         0.01 0.1 1 10 100                                 Pet Dander                                     Dust Mite Debris                                         Skin Flakes                                                     Can                                     Tobacco Smoke                                               Cooking smoke                                                           Pollens                                         Bacteria                                                         Hair                              
  12. 12. Lung Deposition  Particle deposition in lungs Source; J. Heyder, GSF
  13. 13. Lung Deposition  Particle deposition in respiratory tract:  Upper, upper bronchial, lower bronchial, alveolar Source; J. Heyder, GSF
  14. 14. Scope Introduction Indoor air quality Airborne contaminants Filter performance test method Residential HVAC system Impact of filter efficiency on indoor air Energy cost Conclusions
  15. 15. ASHRAE 52.2 Test Method Filtration efficiency for particle sizes 0.3 to 10 µm Challenge aerosol KCl Test dust ASHRAE Initial efficiency and efficiency after dust loading Efficiency for three particle size ranges: E1 0.3 – 1.0 µm E2 1.0 – 3.0 µm E3 3.0 – 10 µm Minimum Efficiency Reporting Value (MERV)
  16. 16. ASHRAE 52.2 Test Method Air flow rate (face velocity) for testing  118 – 246 – 295 – 374 - 492 – 630 – 748 fpm  Concept of the face velocity strongly influenced by commercial HVAC Residential HVAC – filter tested at 295 and 492 fpm Final resistance of filter after dust loading Greater than twice the initial resistance Minimum final resistance depends on MERV Does not reflect conditions for residential HVAC ASHRAE 52.2 and residential HVAC
  17. 17. MERV GROUP NUMBER MERV RATING E1 Average Particle Size Efficiency (PSE) 0.3 - 1.0 Microns E2 Average Particle Size Efficiency (PSE) 1.0 - 3.0 Microns E3 Average Particle Size Efficiency (PSE) 3.0 - 10.0 Microns Average Arrestance (ASHRAE52.1 Minimum Final Resistance (In W.G.) 1 MERV 1 MERV 2 MERV 3 MERV 4 Less than 20 % Less than 20% Less than 20% Less than 20% Less than 65% 65 - 69.9% 70 - 74.9% 75% or greater 0.3" 0.3" 0.3" 0.3" 2 MERV 5 MERV 6 MERV 7 MERV 8 20 - 34.9% 35 - 49.9% 50 - 69.9% 70 - 84.9% 0.6" 0.6" 0.6" 0.6" 3 MERV 9 MERV 10 MERV 11 MERV 12 Less than 50% 50% - 64/9% 65% - 79.9% 80% - 89.9% 85% or greater 85% or greater 85% or greater 90% or greater 1.0" 1.0" 1.0" 1.0" 4 MERV 13 MERV 14 MERV 15 MERV 16 Less than 75% 75% - 84.9% 85% - 94.9% 95% or greater 90% or greater 90% or greater 90% or greater 95% or greater 90% or greater 90% or greater 90% or greater 95% or greater 1.4" 1.4" 1.4" 1.4"
  18. 18. Residential HVAC Building as protection against outdoor contaminants Residential HVAC systems Indoor sources of particulate matter Re-circulating air Portable air cleaners Infiltration Recommended < 0.06 cfm/ft2 of outside area at ΔP = 0.30” H2O Typical commercial and residential infiltration is higher
  19. 19. Residential HVAC Major components Return and supply ducts Blowers Permanent Split Capacitor (PSC)  Brushless Permanent Magnet (BPM) Rated at Total External Static Pressure ΔP = 0.5 in. H2O Filters Ideal filter ΔP < 20% TESP Heaters Ideal coil ΔP < 40% TESP
  20. 20. Typical Residential HVAC ΔPS (+) ΔPR (-) SUPPLY RETURN HEATING F
  21. 21. Flow Rate Fan curve for PSC blower  Typical, small residential PSC blowers HP⅓
  22. 22. Types of Residential Filters Pleated and flat panel – 1 and 4” deep
  23. 23. Residential HVAC Residential furnace filters – typical issues Filter bypass Lack of seal, gaskets Filter size does not match size of specific housing Undersized filters for given flow rate Filter area not fully utilized Non-uniform air velocity Inefficient filters Large number of MERV 7-8 filters Majority filters MERV 10
  24. 24. Undersized Filters Practical industry standards One ton of cooling 12,000 Btu Cooling airflow 400 cfm/ton Heating airflow 100 – 150 cfm/10,000 Btu Undersized filters for given flow rate Filter Face area, [ft2 ] Flow rate @295 fpm 16 x 25 2.47 820 20 x 20 2.47 820 20 x 25 3.47 1,024
  25. 25. Filter Area Utilization Change in cross section area of a return duct Smaller inlet to the blower
  26. 26. Test Overview Selection of residential furnace filters Dimensions 20 x 25 x 5 in. Efficiency MERV 4 – 16 Filter testing according to ASHRAE 52.2 Laboratory testing Filter efficiency measurement using test set up simulating a typical residential furnace Impact of seal and filter bypass Test house Concentration of particulates inside test house Power consumption – test house
  27. 27. Laboratory Test  Blower  Permanent Split Capacitor (PSC)  ¾ HP  Test set up  Duct dimensions 28 x 12 in. 28 x 21 in.  Filter housing 21 x 28 x 7 in.  Filter dimensions 20 x 25 x 5 in.  Measurements  Air velocity  Filter efficiency
  28. 28. Air Velocity  Air velocity across MERV 8 filter  Measurements 2 in. from the test filter  Theoretical air velocity V = 576 fpm  Turbulent flow due to sharp turns
  29. 29. Performance of Selected Filters Filters tested according to ASHRAE 52.2 Filter dimensions 20 x 25 x5 in. Filter efficiency at 1200 cfm
  30. 30. Performance of Selected Filters Filters tested according to ASHRAE 52.2 Filter dimensions 20 x 25 x5 in. Filter efficiency at 2000 cfm
  31. 31. Performance of Selected Filters Filters tested according to ASHRAE 52.2 Filter dimensions 20 x 25 x5 in. Filter pressure drop
  32. 32. Filter Bypass Filter penetration, P with bypass flow, QB Bypass flow through gaps       Efficiency decrease depends on: Bypass flow Filter efficiency without bypass U-shaped 10 mm gap at ΔP = 50 Pa QB/Q ~20% �� = 12�� ��3 �� + ሺ1.5+�ሺ� 2�2 �2 �� 2
  33. 33. Filter Efficiency Filter initial efficiency at the flow rate of 2000 cfm E1 efficiency for submicron particles (0.3 – 1) Ambient aerosol Optical particle counter Filter MERV 8 MERV 13 MERV 16 ASHRAE 52.2 23.0 64.3 95.0 Test set up 20.0 59.7 91.2 NOTE: MERV 13 filter ΔP = 0.48 in. H2O at 2000 cfm MERV 16 filter ΔP = 0.32 in. H2O at 2000 cfm
  34. 34. Impact of Bypass Filter initial efficiency at the flow rate of 2000 cfm E1 efficiency for submicron particles (0.3 – 1) Ambient aerosol Optical particle counter Filter MERV 8 MERV 13 MERV 16 Test set up 20.0 59.7 91.2 With 5 mm gap* n/a 58.1 89.1 NOTE: *Bypass gap 250 x 5 mm (10 x 0.25 in.)
  35. 35. Scope Introduction Indoor air quality Airborne contaminants Filter performance test method Residential HVAC system Impact of filter efficiency on indoor air Energy cost Conclusions
  36. 36. Cleaning Effectiveness – Particle Decay  Concentration of particles  Submicron 0.3 – 0.5 micron  E2 range 1 – 3 micron  Instrument optical particle counter  Location 36 in. above the floor  Test house  House size 2300 ft2  Blower PSC, heating mode  Test filters  Dimensions 20 x 25 x 5 and 20 x 25 x 1 in.  Seal gasket around filters
  37. 37. Cleaning Effectiveness – Impact of MERV  Particle decay for 0.3 – 0.5 micron particles
  38. 38. Cleaning Effectiveness – Impact of MERV  Particle decay for 1 – 3 micron particles
  39. 39. Cleaning Effectiveness – Filter Size Impact  Particle decay for 0.3 – 0.5 micron particles
  40. 40. Cleaning Effectiveness – Filter Size Impact  Particle decay for 1 – 3 micron particles
  41. 41. Cleaning Effectiveness – Filter ΔP impact  Particle decay for 0.3 – 0.5 micron particles  ΔP = 0.15 and ΔP = 0.49 in. H2O @1200 cfm
  42. 42. Cleaning Effectiveness – Filter ΔP impact  Particle decay for 1 – 3 micron particles  ΔP = 0.15 and ΔP = 0.49 in. H2O @1200 cfm
  43. 43. Scope Introduction Indoor air quality Airborne contaminants Filter performance test method Residential HVAC system Impact of filter efficiency on indoor air Energy cost Conclusions
  44. 44. Life Cycle Costs Life Cycle Costs (LCC) widely used to design energy efficient commercial HVAC systems LCC =Initial Investment + Energy Cost + Maintenance Cost + Cost of Disposal  Cost of energy during filter service life Flow rate, average filter pressure drop and energy cost P TPQ tEnergy η8515 [$]cos ∆ =
  45. 45. Typical Residential HVAC ΔPS (+) ΔPR (-) SUPPLY RETURN HEATING F
  46. 46. Flow Rate Fan curve for PSC blower  Typical, small residential PSC blowers HP⅓
  47. 47. Power Consumption Power consumption for PSC blower  Typical, small residential PSC blowers HP⅓
  48. 48. Test House  HVAC System  Duct dimensions 24 x 10 in.  Blower PSC – 1/3 HP  Rated at TESP 0.50 in. H2O  Furnace 88,000Btu  Filter dimensions 20 x 25 x 5 in.  Measurements  Flow rate  Air velocity in the return duct  Filter pressure drop  Power consumption
  49. 49. Test Results Filter Filter ΔP Flow Power ΔPR ΔPS [in. H2O] [cfm] [W] [in. H2O] NO FILTER 1232 636 -0.23 0.11 MERV 8 0.13 1172 606 -0.22 0.10 MERV 16 0.17 1117 600 -0.19 0.10 MERV 16 – H 0.42 950 552 -0.13 0.07 COMMENTS: • Flow rate without filter is comparable to the fan curve •Power usage is comparable the fan curve •Pressure drop in the return and supply ducts is significant •Filter pressure drop inside the system
  50. 50. Impact on Heating Time Test results Test house 2300 Ft2  Mode Heating Test time 1-1.5 hr per filter Outside temperature 30 – 35o F During test temperature within 2o F Test filters MERV 8 MERV16 – High MERV 8 filter ΔP = 0.10 in. H2O @1200 cfm MERV 16 – H filter ΔP = 0.49 in. H2O @1200 cfm
  51. 51. Impact on Heating Time Average heating time for each filter was measured Heating time for high ΔP filter Ratio = --------------------------------------- Heating time for low ΔP filter
  52. 52. Impact on Heating Time Blower electrical energy High ΔP filter Low ΔP filter Power usage, [W] 552 606 Corrected for time 592 606 Annual heating 2080 hrs 1231 kWh 1260 kWh Cost @$0.10/kWh, [$] 123 126 Furnace – natural gas High ΔP filter Low ΔP filter Annual energy, [therm] 790 Corrected for time 848 790 Cost @$1.30/therm, [$] 1102 1027
  53. 53. Summary  Literature data support link between exposure to submicron particles and health issues  Performance of residential filters in real life conditions does not correlate well with the laboratory testing according to ASHRAE 52.2 due to lower test face velocity (295 fpm), flow conditions, leaks, duct construction  Low grade residential HVAC filters (MERV ≤ 10) do not provide sufficient protection against airborne particles  In order to decrease cardiovascular risk and other health hazards associated with exposure to air pollution, high efficiency residential filters such as MERV 14 – 16 should be used
  54. 54. Summary  Energy cost to operate residential HVAC system during heating mode is higher for high resistance filters  Residential HVAC systems with PSC blowers and installed high pressure drop filters require:  Longer time to heat specific space resulting in higher operational cost  Longer time to reduce concentration of airborne particles due to reduced flow rate

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