A Home Use Study of Residential HVAC Filters

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Marsha Nelson
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1 A Home Use Study of Residential HVAC Filters John Zhang and Andy Fox Construction and Home Improvement Markets Division Presentation in AFS 2015 October 7, 2015

2 Outline Characteristics of Residential HVAC Efficiency Study of Residential HVAC Filters Pressure Study of Residential HVAC Filters

3 Residential HVAC vs Commercial HVAC Lower Duty Cycle Residential : 10 25% run time (Zhao et al, 2015) Commercial: 50% - 100% Particle source Residential: mostly indoor particulates Commercial: mostly outdoor particulates Particle Concentration Residential: 1 mg/m 3 5 mg/m 3 (PM2.5) Commercial: 10mg/m 3-30mg/m 3 (PM2.5) Face Velocities Residential : 250 FPM 500FPM Commercial: > 500FPM

4 (Zhao, Azimi and Stephes ASHRAE 2015)

5 Particle Sources Shower Head Bacteria, Fungus Aerosol Dust Particles Smoke Pollens Bacteria, Virus Smoke,Soot Dust Bacteria, Allergens Cooking Stove Smoke, Fume Dust, Allergens Smoke, Smog, emission Indoor Outdoor

6 Part I: Efficiency Study The ASHRAE standard includes a conditioning test, Appendix J, to determine the minimum efficiency of a filter. The minimum efficiency is used to compare the relative life-time performance of various filters. Is Appendix J representative for residential HVAC filters?

7 Experiment Plan Efficiency Study Evaluated 3 different types of electret residential HVAC filters. Measured initial efficiency of test filters Installed each type of filters in 3 or 4 different homes. Removed at 90 days (EOL) to measure fractional efficiency in the lab Performed ASHRAE 52.2 testing on companion filter for each performance level

8 Table 1. Properties of Three Electret Furnace Filters Filter ID Media Type Charged yes/no? Pleats per foot Type A High Loft Yes 12 Type B Pleatable Yes 42 Type C Pleatable Yes 42

9 Efficiency, % ASHRAE 52.2 Appendix J Conditioning Results Overlay for Type A Filter Particle Size, um Initial-1 Initial-2 Initial-3 Initial-4 MCE EOL-1 EOL-2 EOL-3 EOL-4 App J

12 MERV Comparison Initial 52.2 MCE Home Use Appendix J Conditioning Filter A MERV 11 MERV 11 MERV 7/8 MERV 7 Filter B MERV 11 MERV 11 MERV 10/11 MERV 6/7 Filter C MERV 13 MERV 13 MERV 12 MERV 8 For residential HVAC filters, Appendix J conditioning under-predicted the filter performance.

13 Summary (1) Efficiency Study Current ASHRAE Appendix J conditioning is not representative for predicting EOL efficiency of residential HVAC filters. It is suggested to conduct research to identify/develop a test conditioning aerosol that is representative for residential home environment. It is needed to separate the air filter standards for commercial and residential HVAC filters.

14 Part II: Pressure Drop Study The ASHRAE standard includes a dust loading test to determine the dust holding capacity of a filter up to a pre-determined final pressure drop. The dust holding capacity is often used to compare the relative loading performance of various filters. Is the pre-determined final pressure drop representative for residential HVAC filters?

15 Experiment Plan Pressure Drop Study Evaluated 18 different types of electret residential HVAC filters. Measured initial drop of test filters Installed each type of filters in different homes. The study was run in the middle of winter in St. Paul, which is a high duty cycle environment. Removed at 90 days (EOL) to measure pressure drop in the lab

16 Table 1: Filter constructions used in the study (all 16x25x1 nominal size) Filter Media Filter pleats per foot Mean dust fed to 0.5, g A High loft B High loft C High loft D High loft E High loft F High loft G High loft H Pleatable I High loft J High Loft K High loft L High loft M Pleatable N High loft O High loft P High loft Q High loft

17 Pressure Drop, "H2O What Really Happens in Use? results from 18 in-home studies Three months, winter use, St. Paul, MN Typical resistance rises ~ 40% Pressure Drop of Home-Use Test Filters ASHRAE MERV 9-12 Final Resistance Final resistance is still at a fairly low value ASHRAE MERV 5-8 Final Resistance A B C D E F G H I J K L M N O P Q Initial Final Final resistance is far below recommended MERV test levels Earlier 52.2 versions Home-Use Filter Set N > 30 for most filter types

18 Summary (2) Pressure Drop Study Final resistance is far below recommended MERV test levels (earlier 52.2 versions) for residential HVAC filters. It is suggested to conduct research to identify/develop a test conditioning aerosol or modify the dust loading procedure to better simulate the dust loading for residential home environment. It is needed to separate the air filter standards for commercial and residential HVAC filters.

19 Thank You!!!

AIR FILTERS: REAL WORLD PERFORMANCE

AIR FILTERS: REAL WORLD PERFORMANCE B. Dean Arnold Kimberly-Clark Corporation, 1 Holcomb Bridge Road, Roswell, GA 376 ABSTRACT This paper describes the results of studies conducted to investigate the actual