Nafa Tech Seminar Phoenix Arizona 2004 Phil Maybee NAFA President the filter man

MERV A practical look at ASHRAE 52.2 “Method of testing general ventilation air-cleaning devices for removal efficiency by particle size”

Definition Minimum – worst case scenario Efficiency – based upon specific particle size challenge Reported –12 sets of particle sizes in three groups of four sets to make ranges E-1,2,3 Value – tested upstream vs downstream and given as a percentage performance

WHY MERV ASHRAE 52.2 ASHRAE 52.1 Particle size performance Minimum efficiency Tested to maximum airflow advertised Tested to realistic pressure drops Consistent test aerosol ASHRAE 52.1 Dust spot efficiency Average efficiencies Moving pressure drop values Atmospheric challenge changes Dust Holding Capacity

ASHRAE 52.2 Test Duct Configuration Outlet Filters ASME Nozzle Downstream Mixer Exhaust Room Air OPC Inlet Filters Aerosol Generator Upstream Mixer Device Section Blower Flow Control Valve Backup Filter Holder (Used When Dust loading)

Possible downside? ASHRAE 52.2 uses Neutralized dust meaning that the natural positive and negative charges in the atmosphere are diminished in the test This could have a different effect on efficiency compared to natures effects

Average Efficiency? When it does not work!! (new) When is a 95% filter not a 95% filter? When it does not work!! (new) the top five 95% V-cell filters today have an initial efficiency of 57 – 81% on their best distributed test report

Determine the NEED The particle size which causes problems varies from industry to industry and methods or purpose of use Once we determine the particle size we can choose a filtration efficiency - MERV

WHO Sets the Particle Size? Industries that know what the killer defect size particle is, require filtration systems to remove those particles from the air… Paint finishes Computer chip manufacturing Bio/Genetic research Surface Etching

Ranges in 52.2 Testing E-3 particles between 3 and 10 microns (efficiency is calculated on the composite range) NOTE: there is no mathematical correlation between 52.1 and 52.2 filter efficiencies

MERV Data

MERV 1 - 4 Filters that fit within the 1 - 4 category are not tested by ASHRAE 52.2 test procedure. Rather the Standard refers them back to ASHRAE 52.1 Less than 20% Efficient on the E-3 range These are the historic arrestance type filters – autorolls, metal washables, etc

MERV 5 - 8 Starting above 20% on the E-3 range MERV 5 must be 20-35% MERV 8 must be above 70% Can be Filters from 20% to 60% Dust Spot

MERV 9 - 12 Measurable efficiency on the E-2 Range and a minimum of 85% or more on E-3 MERV 9 must be up to 50% MERV 10 must be 50-65% MERV 11 must be 65-80% MERV 12 must be more than 80% (filters can be from 40 – 90% Dust spot)

MERV 13 - 16 Measurable efficiency in submicron E-1 and more than 90% in the E-2 and E-3 MERV 13 is up to 75% MERV 14 must be 75-85% MERV 15 must be 85-95% MERV 16 must be more than 95% in all categories E-1, E-2 and E3 (can be filters from 75 Dust spot – 95 DOP)

MERV Reporting A filter is given a MERV at a given airflow Example : MERV 11 at 492 fpm (1968 cfm) MERV 11 at 295 fpm (1180 cfm)

MERV Reporting Final pressure drops are per Range E-3 is 0.6” wg Dust Holding Capacity is not a reported value

What does the 52.2 Provide “When a specific particle size efficiency is identified as the target particle size it is possible to look at the test for that specific size rather than depend on the MERV”

TYPICAL 52.2 COMPLETE LOADING TEST DATA REPORT Size Range (microns) Fractional Efficiency (%) @ P (“W.G.) Composite Minimums 0.285 0.320 0.464 0.643 0.822 1.000 0.3-0.4 2.7 6.7 17.2 29.4 37.1 37.9 2.7 0.4-0.55 7.8 15.9 27.7 43.3 53.2 54.6 7.8 0.55-0.7 11.2 30.2 46.0 60.7 70.5 71.6 11.2 0.7-1.0 17.6 42.6 59.3 73.7 81.3 81.8 17.6 1.0-1.3 20.4 51.6 70.3 80.8 83.7 85.2 20.4 1.3-1.6 23.9 58.2 76.5 84.7 86.1 87.2 23.9 1.6-2.2 28.3 69.9 84.1 89.1 90.2 91.0 28.3 2.2-3.0 36.3 83.9 91.9 94.2 94.4 93.2 36.3 3.0-4.0 39.4 89.4 93.7 95.8 96.4 94.9 39.4 After all of the testing and dust loading to final resistance, this is the data produced. Here you see the composite minimum of a MERV 6 filter. 4.0-5.5 42.8 90.6 95.3 96.5 97.9 95.6 42.8 5.5-7.0 46.5 92.3 97.1 98.0 98.4 97.9 46.5 7.0-10.0 50.4 94.8 97.5 98.3 100.0 99.2 50.4 Initial Minimum Efficiency Reporting Value: MERV 6 @500FPM 0.3 to 1.0 Micron 1.0 to 3.0 Micron 3.0 to 10.0 Micron Composite Average Efficiency: E1 = 9.8 E2 = 27.2 E3 = 44.8

52.2 Users Guide Simple explanation of test procedure Has all the ranges and particle size info Rough equations to 52.1 efficiency And examples of the uses