nafa technical seminar april 19, 2012

• NAFA Technical Seminar• April 19, 2012

ANSI/ASHRAE 52.2Can we fix this

Method of Test?

History of the Test procedure

• 10+ years in development prior to 1999 release • Task of 52.2 Committee "create a test method

based on particle size removal efficiency for end user evaluation of filter performance"

• Research projects led to greater understanding of the physical science in filtration

• MERV - scales were created with minimal data and educated guesses at value spread

Committee Efforts

• Std published in 1999 for the first usage• No revisions through 2007 (other than edits)• 2008 Arrestance and DHC were added from

52.1 predominantly for MERVs 1-4• 52.1 was removed from ASHRAE Standards• Addition of "Voluntary Conditioning Step"

MERV's Status?

• ASHRAE Rating system?

• No certification of personnel performing tests

• No policing entity to produce a rating system

ISO Standards

• Working groups creating standards for • Cleanroom and HEPA usage completed• UVC, Rotating Equipment, dust collection• Working group 3 - General HVAC filtration is

looking to use 52.2 MOT for developing PM efficiency values

Definition:•System of classification according to merit or amount

•Assessment of something in terms of quality, quantity or both

•What filter parameters should be included?Filter Performance – pressure drop, efficiency,

lifeEnergyPerceive ValueCost

Filter Rating

Is it possible to combine filter performance characteristics into one criterion?Greater value of the criterion equal to “better”

filter

Traditional quality factor (figure of merit):

o E – filter efficiency and ΔPo – filter pressure drop

Potential issues:

Different ΔPo units

Results at different flow rate

Filter Rating

oP

ELn

)1(

Example 1: E1 = 80% and ΔPo = 0.40” H2O

α1 = - ln (1 – 0.8)/ 0.40 = 1.609/0.40 = 4.02

Example 2: E1 = 80% and ΔPo = 0.30” H2O

α2 = - ln (1 – 0.8)/ 0.30 = 1.609/0.30 = 5.36

Example 3: E1 = 85% and ΔPo = 0.40” H2O

α2 = - ln (1 – 0.85)/ 0.40 = 1.897/0.40 = 4.74

Filter Rating

Single Aggregate Objective Function (AOF) Weighting method, linear AOF:

MAX

o E – filter efficiency; ΔPo – filter pressure drop

o C – filter cost; DHC – filter dust holding capacity

o λ – weighting factors; ∑ λi = λ1 + λ2 + λ3 + λ4 =1

o λ – weighting factors are assigned based on priority - subjective

Filter Rating

DHCCPEL 4321

Combination of objectives:

Other objectives: Cost,Energy

Filter Rating

DHCP

ELnDHCa

o

)1(

MERV – is MERV a rating system?

Residential filters – Home DepotFPR (Filter Performance Rating) = 1 – 10 scale

Weighted Average = λ1 (Efficiency Large Particles) +

λ2 (Efficiency Small Particles) + λ3 DHC

λ1 + λ2 + λ3 = 0.6 + 0.3 + 0.1 =1 FPR = 10 for Weighted Average > 25

Residential filters – 3MMPR – Microparticle Performance Rating

ability to capture particles 0.3 – 10 µm (E1)

Filter Rating - Examples

“Too Many MERV’s” ??According to ASHRAE and IEST – 20 Possible Assignable MERV’s

Three “Markets” E3 Arrestance MERV 1-4 General Equipment E2 Middle Efficiency MERV 5-12 Equipment and People E1 High Efficiency MERV 13-20 Marginalized Health People and Specialized End UsesReal Differences Between the Markets

Arrestance High Efficiency

Real Differences Within These Markets MERV 5 MERV12

DifficultiesVariety of End UsesVariety of Air Handling TypesVariety of Pollutants

Conditioning Step is Too Expensive

15

Conditioning Step Not Real World

16

Mechano-ElectretFilter

Mechanical OnlyFilter

52.2 Positive Attributesbefore Conditioning

17

Analogy—Gas Mileage Testing

http://www.caranddriver.com/reviews/2012-ford-focus-sel-test-review 18

ASHRAE 52.2-2007

Tom Justice

2010 Round Robin

2011 Round Robin

Issues under Review by Task Groups

• Current MERV boundaries• Humidity Range• OPC particle counter specifications• Air density calculation• Shedding• IPA vapor conditioning• Test variability

Reported Values

Channel E1 E2 E3 Reporting Value

Particle Size Range .3 to 1 1 to 3 3 to 10

Filter 1 37% 65% 84% MERV 8

Filter 2 36% 65% 85% MERV 11

Issues under Review by Task Groups

• Current MERV boundaries• Humidity Range• OPC particle counter specifications• Air density calculation• Shedding• IPA vapor conditioning• Test variability

Fig. 8 ASHRAE 1287 RPFig. 8 ASHRAE 1287 RP

KCL @ 0% to 85% RHKCL @ 0% to 85% RH

Other Potential Issues

• Test dust• Specifications for particle generator• Radioactive versus corona discharge in

neutralization of airstream• Initial resistance calibration